The Stovebolt Site Forums The Shop Area The HiPo Shop 49 GMC project

Finalized the trade and now have a slammed 49 GMC 1/2 ton siting in my shop. Supposedly it's only a battery away from running so I'll be checking that soon. It's far from stock and I'm in the process of ciphering out what it is I traded for LOL.
The engine serial # is F1031TAJ and it's loaded with what I've been told is smog related crapola. The previous owner says it's a 250 but I'm hoping to verify that with help from y'all. I've been unsuccessful in translating that number.
It has a 4bbl quadrajet carb and dual exhaust exiting the rear.
Previous owner also indicated it has a turbo 400 auto but since the dang thing is so low to the ground I'm going to have to jack it up just to see. I do see the open driveshaft. It has 5 lug Cragers all around and power disc's up front. Ripped bucket seats inside and thankfully the lower bench frame is still intact.
I don't know if having a 4bbl later model 6 banger qualifies to be in the HiPo forum but it certainly ain't stock lol.
Any help on ID'ing the powerlant in this lowrider will be appreciated.
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A mixture of Hotrod and stock. I think you can post in whatever forum you feel is best for the subject at hand. Looks really cool and you’re going to have a blast with it.🛠

Check the front motor mounts- - - -if they're straight across from each other, you've got a late model 250. The mounts are offset on a 292, and the side cover would also be very tall. The valve cover with all the oddball plumbing and the air injection lines in the exhaust ports pretty much date the engine to the late 1980's or so. Does it have the integral intake manifold cast with the head? Hope not, as those things were bad when they were new, and several decades of use haven't improved them! The 4-BBL was never a factory option, BTW, that has been adapted somewhere along the way, and probably isn't calibrated for a 250 at all. There was a Q-Jet for a Pontiac 250 overhead cam six, but it's about as easy to find as a saddle-broke unicorn!
Jerry

Good deal Martin. I'll keep it here for now.

Jerry, best I can tell the intake manifold is integral to the head. I'll attach some closeups. The exhaust manifold looks like a cast dual with an EGR. Factory perhaps? I'm not experienced with these 230/250's so this is new territory and I usually enjoy new territory. I'm going to try and start it up before I tear into anything. Previous owner said it ran great until he bottomed out on a railroad track and noticed anti freeze under it. Said he hasn't run it in a yr and ofcourse the battery is deader than dead.
Another thing, he said it had an electric fan which burnt out and included a brand new in the box electric fan to be re installed. If I'm not mistaken a 230/250 isn't any longer than the 228 that was probably in it. There seems to be enough room to bolt a stock fan back in, I even have the fan on my rebuilt 235 I could try, I may try it.

Theres alot of hillbilly engineering I'm going to have to sort out, but I got the time. Dang thing sit's so low I'm wondering if I can even get a jack under it.....
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My crowded shop.

Sneaky trick- - - - -stack up 2 or 3 layers of 2X6 lumber with 4 inches of offset on one end like stairsteps, join them with long wood screws, and drive up onto them to raise the frame high enough to get a jack underneath. We used to carry a couple of stacks like that to help level travel trailers and motorhomes so the LP gas refrigerator would function in a campground.
Jerry

Good idea on the 2x6's.

Found the date code on the engine, J268. Translated it means the engine was cast on Oct 26 of the year ending in a 8.
I'm going to guess it's a 1978 as it appears Chevy stopped putting the 250 in USA vehicles in 1984.
It also a possibility that it's the one year only LD4 version 250 and I don't know if thats good or bad LOL.
The block casting code appears to be 473483 which isn't in any database I could find online and the serial number stamped on the block distributor boss is F1031TAJ which I couldn't cross ref either. I think the TAJ means it came out of a truck which could mean that the intake is for a 2bbl. but thats a guess at this point. I'll have to pull the carb to know for sure.
Atleast I'm pretty sure it's a 250 since it has the integrated head and intake manifold. (which may be bad in it's own right).

It'll be a couple days before I can get back on it but the plan is still to get it running as is then go from there. I can definitely see removing all the smog crapola and perhaps putting a nicer valve cover on it.

Might be of use:
Old SB Query

Search your block casting code here

quote: At least I'm pretty sure it's a 250 since it has the integrated head



Bingo. That valve cover was for PAIR (pulse air injection reaction), didn't use a pump. Used a 2bbl Rochester Vari-jet carb on pick up engines. The integrated head was never used on 292.

Gord and BC, good info and links.

Got it up on jacks. Saw some good things and so not so good things.
The good:
The front disc brake assembly and rear end assembly look to be properly installed. There was a little ding on one corner of the tranny pan but it wasn't bad and wasn't leaking. The exhaust looked good with dual Smithy's but for some unknown reason it doesn't have tailpipes. The pipes exit the Smithy's and hump over the rearend and turn towards the back but thats where they stop. Also seen the remains of the original wood bed with what appears to have all the hardware. Floorpans looked good. Other than a small leak on one of the tran's cooler lines and a loose clamp on the lower radiator hose, the engine, trans and radiator appear to be holding fluids.

The bad:
I found the trans cooler ty-rapped to the front axle and it was leaking from one of the clamp connections. It will get extended to up infront of the radiator. Saw a rust hole in the rear tranny cross member. I may patch it but need to inspect it more. Theres no parking brake.
The triple pulley harmonic balance only clears the front cross member by 1/4" to 5/8". It's so tight I couldn't get the alt belt (that was off and turned inside out) back into the pulley without jacking the engine up slightly and squeezing it in. The Alt was missing the lower through bolt that probably contributed to it being thrown off the pulley. I'm going to research into getting a dual pulley for the Alt so I can install the belt on the 2nd HB pulley and not have to jack an engine up just to change a belt.....

The ugly:
I can see how they lowered the front and rear, they removed leaf springs. Theres only 2 full length springs in the front with several spacer blocks to take up the slack. I don't think the spindles are the drop type but I'll study on that later. I can see adding some leafs back. The front short shock looks to be no more than 12" tall and may be shorter.
It appears they've "engineered" a 4bbl carb to a 1bbl intake.

I did get it started and running. It also moves and stops. Once I got the Alt belt on, it charged and the stock ammeter registered accurately until the belt snapped, The oil pressure, temp and gas gauges didn't register. No headlites or turn sigs but brake and parking lites worked. The "engineered" single electric windshield wiper was inop also.
The engine would fast idle and I couldn't get it to knock down to slow idle even though the choke opened fully. Even screwing out the idle screw didn't have any effect, will study on that. It would stumble and lose power when I tried to goose the throttle. It would accelerate if I slowly raised the throttle. Don't know if it's a leaky vacuum or something to do with that 4bbl. I found a complete 1bbl Rochester MonoJet in a box under the seat. I'm betting it was the original. I may go back to it but will get the Alt, cooling system situated and the trans cooler moved in the mean time.
The engine smoked alittle but may be due to lack of use. Didn't want to run it long without a cooling fan.
A few pics.
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Running video

That engine is probably out of a 1973, 1974 or 1979 truck. Search TAJ here

You need to check the date code on the block.

edit: Since it has an HEI distributor, it must be 1979

Since the integral-intake cylinder head isn't particularly popular, a little machining and tinkering on it to adapt a small-bore Rochester 2 barrel carb calibrated for a 265 V8 might be a better option than the current Q-jet setup. I doubt if you'll ever get it to wind up tight enough to open those massive secondary barrels, and the acceleration stumble probably means it's going lean even on the primaries unless you feather-foot the gas. I also seem to remember Rochester making a 2 BBL for some of their 90 degree V6 engines in the 1980's that was essentially the front half of a Q-jet with no secondary barrels.
Jerry

Jerry;

They were called "Dual Jet". As you said they are the front half of a Q-Jet. The only problem is/was that they had a funky bolt pattern. As always, there are a few on ebay. Your suggestion of the Rochester 2 bbl (some were called 2 Jets!!) is probably the better way to go.

SimS

The Rochester 2 BBL used on the 265 and 283 engines was a very good carburetor. There was also a bigger bore model used on Pontiacs and a few other bigger-displacement engines. That one got adapted to 305 and 350 engines 20-something years later. The 305's had problems with it because of the large venturi size and had to have a very high float setting to avoid an off-idle stumble and a lean surge at part throttle. The small bore carb calibrated for a 265 should work pretty well on a 250, but only if the manifold is modified to accommodate the carb base. Using an adapter to mate the 2-BBL to the one-hole original carb flange would be worse than useless.
Jerry

Sure was an interesting choice for an engine swap. Not unusual to see a 230/250 in that era of truck. But I’ve sure never seen one like that!

Looks like a fun project.

It now appears the block was cast Oct 26 1978 and installed in a 1979 Chevy truck per all the good info y'all have provided (Gord, BC & Jerry), so I'm going to call it a 79 250 truck engine which should have a 2bbl intake hidden under that Q-Jet.

With that ciphered I moved on to the Q-Jet carb. The ID is: 7042210 QE2711 That translates out to a Federal standard 1972 Q-Jet with a divorced choke thermostat that came on truck 350ci engines.
On this engine theres no choke thermostat of any kind much less a divorced thermostat. They've got it rigged to be fully closed and use the choke vacuum pull off to fully open it once it starts. This might explain the loss of power when I opened the throttle and also why it wouldn't "kick down" to a lower rpm when I goosed it to get it off high idle.
Curiosity is killing me so once I can get back on it in a couple days I'm going to rig up a manual choke 1st then try it out. I'm also going to go through all the vacuum taps as I don't think they've got those connected correctly either. Basically go through all the easy stuff before going deep. If that doesn't get it going right I'm going to pull that Q-Jet, see how it's adapted and either marvel at it or laugh at it then determine the next course of action. I'd like to see if that engine can run good with that big mutha hanging on it LOL. Course I'm not adverse to putting the correct Vari-Jet 2bbl on it if all fails.
Engine casting number
Engine date and Con number
Q-Jet choke side pic
Engine serial number

The Vari-jet carb is the spawn of the devil- - - - -it has a secondary air valve with a metering rod attached to it that works like half a Q jet 4 barrel, and the metering rod has a nasty habit of coming adrift and getting sucked into the engine. It makes for some interesting knocking noises when it gets imbedded in the top of a piston. The carb that's on it now is built for an engine 100 cubic inches larger, so it's going to run VERY lean. Have a fire extinguisher handy for the inevitable backfire that's bound to happen. I think I've got a vari-jet stashed away somewhere that I picked up on a horse-trade- - - - -not even sure if it's rebuildable!
Jerry

Duly noted Jerry. btw you talked me out of a trade for that vari-jet LOL. I'll keep my eye out for a Duo-Jet.

Been studying on that Q-Jet setup and it appears it may never have opened up those huge secondaries and operated as a 2bbl only. Since theres no choke control (other than the vacuum pull off) there was no way to move the choke controlled secondary throttle plate stop. Seems the OEM's didn't want those secondary bbls kicking in until the engine was good and warmed up and the choke linkage fully in the open position. The vacuum pull off doesn't do that, only the thermostat does.
In my previous post look at the pic labeled Q-Jet choke side pic and you can see how the choke linkage locks the secondary throttle plate closed (roll pin in the throttle plate shaft locks it closed). In any case since all I can do at this moment is sits and thinks so I'm reduced to just ciphering LOL.

Some other good news is I left the battery still connected and it hasn't discharged so theres nothing draining it down, at
least over the last couple 3 days anyways....

I attended one of GM's first training sessions on the Qjet at the General Motors training center in Memphis in 1966 or so. It's really a very well-engineered carburetor, with a 3-stack venturi that transitions very smoothly through all the RPM ranges before getting enough airflow to move that huge air valve and start flowing secondary mixture. Depending on how far the secondary air valve is allowed to open, the carb can flow up to about 800 CFM. Its midget half-brother the Dual Jet would probably be a good choice for your engine, as most of them were designed for the 3.8 liter (231 cubic inch) engine and it would only be jetted slightly over-rich. Adapting it might not be be a big hassle, since the manifold already has a fair-sized squared-off hole in it.
Jerry

Found a picture of the LE3 head:
Ugly head

According to these guys, earlier non-integral heads can be bolted onto the block to replace this one.
Jalopy Journal

Holidays and recuperation aside, I haven't been able to wrench the GMC for awhile but finally got out for a quick looksee and checkout some parts received.
Among a few drops of red and green colored fluid collecting under the truck was a large puddle of clear fluid that passed the brake fluid smell test. Further observation concluded the master cylinder is leaking, probably from the rear seal(s). The power brake setup looks alot like pics of kits I see of classic part conversions. So now I need to ID this OEM looking master cyl and determine if a rebuild kit or complete MS is needed. Anyone with a similar setup may know what yr/model this MS came on...
I picked up a DualJet for next to nothing and it ends up being worth about next to nothing. It has the mixture control solenoid which means it needs an ECM and other sensors in order to work properly. As is it would run way too rich (in it's default state) and not worth adapting. Shame, it's very clean and looks NOS. I cleaned up the MonoJet and depending upon what I find under all those manifold adapters it may get bolted on. The dual pulley for the alternator arrived and looks like it'll work. The plan is to get back on it after the holidays.
Master Cyl 1
Master Cyl 2
pic
Carbs

Based on the type of work that has been done, I would check and see if the engine mounts and trans. mount crossmember might have been moved forward, causing the reduced pulley clearance. Easy to check.

Ed

Ed, good idea, the more I discover the more I need to dig deeper.

Well, I've ID'ed the power master cylinder and combo valve. Now don't shoot the messenger LOL. They are from a, gulp, 70-72 FORD Mustang/Merc Cougar!!!!! Took awhile to cipher that out.
Looking like Johnny Cash's Cadillac ain't got nothing on this truck LOL.
Wonder if this thread should be moved to the project forum as it's turning out to be quite the project....

Got a little done in the cold shop today.
Installed the dual belt pulley on the alternator and got it lined up with the middle drive pulleys on the HB and water pump. Good news is it still uses the same belt for a 79 C-10 250 with P/S and AC and I didn't have to jack the engine up to install it.
Pic
Pulled the QuadraJet. The 2bbl to 4bbl adapter looked to be home made and I've got to admit they did a pretty good job on the design. The large amount of form-a-gasket indicates they must not have spent as much time trueing up the surfaces.
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Best I could tell in the limited time I ran it was it probably worked but how well is up to debate. It's not going back on.
Good news is the integrated manifold is for a 2bbl which matches what the numbers say was a 79 truck engine.
2bbl intake
So I'm in the market for a 2bbl. Bad news is the Monojet that came with it won't work and neither will the electric controlled DualJet.
So I have 3 carbs to trade LOL. I'd like to get ahold of a Holley 350cfm 2bbl .
I've verified via the pan shape and passenger side kickdown cable that the tranny is a TH350 and not a 400. Thats OK. I wouldn't have cared if it was a Powerglide or straight stick, I'm gonna play the hand I'm dealt lol.
I'm including a pic of the manifold heat actuator which is vacuum controlled. My MightyVac indicates it'll work and the flapper moves with vacuum.
Actuator
Best I can tell there should be a vacuum switch somewhere in the coolant system that will pass vacuum to the actuator and once it's heated up will probably close/stop vacuum to the actuator. Some pics I've found on the WWW show a switch mounted in the thermostat housing. This engine's thermostat housing doesn't have this capability.
I found this vacuum switch on the other side of the engine in the head. I'm going to test this once I get it running again and use it if it works.

I tried the 235 fan and it's bolt holes weren't wide enough but they looked like they lined up. This 250 used a clutch fan as OEM and unfortunately theres not enough room between the radiator and waterpump to bolt one up. No doubt the original builder ran into this hence the addition of the electric fan. While holding the fan on the hub it was noticeably too low and not centered on the radiator. So if I were to adapt a fan it would probably have overheating problems so it looks like I'm going back with an electric fan. I've found several thermostatically switched relay kits and will probably go with a 200 on and 180 off switch. Mounting the switch in the head coolant passage seems to be where it should go. This head seems to have several places it could install. I do want to try the 49's old temp gauge too. Theres enough clearance to make it a puller and center it on the radiator. I've already got the fan which came with the truck. It uses some kind of tyrap and plastic holders that fish through the radiator vanes. I'll study up on that more.

I'm gonna have to reinstall my old wood burner as that kerosene is mighty pricey....

Dave

The actuator is for the EFE system which is designed to make the engine heat up faster to reduce emissions. The actuator should close when the engine starts up and open when the engine has warmed up. Apparently the V8s switched the vacuum on/off to the actuator using water temp while the L6 used oil temp. The oil temp vacuum switch (TVS) should be found just above the starter.

Spent most of the morning hooking the wood stove back up and it had it good a toasty. Kerosene is way too expensive and I've got free easy access to wood, just need to cut & split it up lol.
Gord, looks like someone installed an oil pressure switch where the TVS is supposed to be.
Oil pressure sender
Thats alright tho, I'm thinking of installing a Tee there, might try the OEM oil press gauge and a new electric gauge in a 3-gauge cluster under the dash.
Got a few questions on the temp gauge senders and their locations.
Theres a very small electric temp sender (9/16's socket removed it) on the head towards the rear. Did this one work the temp gauge?
Small sender in head
Small sender next to normal sized sender
Theres another electric temp sender below the thermostat. Would this be a good location for the fan control thermostat?
Sender below thermostat

Received the 2SE Varajet Sat. It appears to have been cleaned and rebuilt. I opted for the elec choke. It's spec'ed for a 75-79 Pontiac/Buick but should work fine on the 250.
2SE carb 1
2SE carb 2
2SE carb 3
Bolted right up. The trucks throttle is cable controlled and I'll have to make up a bracket to bolt the cable to it. The bracket that worked for the Quadrajet won't fit on the 2SE . That and an air cleaner to fit a square carb mouth is minor at this point.
This 2SE had the same problem as the Quadrajet, fast idles fine bit won't slow idle. I'm suspecting the PCV mount in the intake manifold has a massive vacuum leak. Someone has siliconed the vacuum pipe back down onto the manifold after apparantly breaking it off.
I would have played with it more but I had the shop shut up tight to keep the heat in and after running it for a couple minutes the cleaning fluid I sprayed all over the engine and washed the gunk and grime down around the exhaust manifold and pipes started smoking like crazy. So I ran it enough at fast idle to hopefully burn it all off and quit for the evening.
Later....

Found a partial answer to the sender question. That small sender is the fan controller temp switch Temp switch
At what temps it cuts on/off is still questionable. The threads are too small for the new sensor included in the kit I ordered so the new plan is to test and use it if it's GTG. It reads open now so it must go to ground when it hits it's designed temp mark.
It's cold and a rare snow day around here.
Dave

Mounted the 12" fan that came boxed with the Jimmy and the fan controlled kit I had ordered. Disconnected and plugged all vacuum ports except to the dist. Started it up, let it fast idle a couple minutes then kicked it down-- and -- it idled... Ran it for approx 20-25 minutes. No knocks, pings or metal on metal sounds and no smoke.
The 49's OEM oil pressure and temp gauges weren't hooked up and don't look like they've been in a long long time. Going to order a mechanical 3 gauge under dash cluster now that I think the engine is good.
Once the electric fan kicked on it never turned off. It's got a 200 on, 180 off sender switch which is probably too low. This 250 probably normally runs around 200, will research that. The 12" fan may be too small too. I tried the small OEM sender switch and it wouldn't turn the fan on. It's either bad or that small 12" fan kept the temp down just enough to keep it off. At $8 I'm going to order a new OEM sender switch as I need the larger port where I installed the new sender switch for the temp gauge. It idled, didn't overheat and I didn't see any air bubbles in the radiator so I'm calling it a good day.
.Running and idling

Keep an eagle eye on the metering rod for the secondary venturi on that Varajet- - - - -that's the one that can come adrift and get swallowed by the intake. It's attached to the air valve flapper in the top of the carb, so it's easy to inspect anytime the air cleaner is removed.
Jerry

As always other projects tend to get in the way.
Pulled the carb and went at those vacuum leaks. Cleaned the goop from the PCV stob and it was pretty loose. Pulled it, cleaned it up, applied some Aviation permatex, pressed it back in and put a coating of JB Weld around it to seal it up.
Pic
Removed the vacuum fitting in the intake under the carb, determined it was in pretty bad shape and plugged it with a threaded plug. The Carb has a large constant vacuum port and I'll use it for the power booster. I may track down a new barbed fitting later...
The gauges I ordered finally arrived (free shipping did take 8 days)
Pic
The water temp and oil pressure gauges are mechanical with adapters. The fuel gauge is a 0-30 ohm. I determined when troubleshooting the electrics that the gas gauge was bad.
I'm going to end up installing a new fan control switch (on order) as I need one that will thread into the small sender port in the head. 1/8NPT is whats needed and the one that came in the kit I'm using is a 3/8NPT. The temp probe will install in the port below the thermostat where the current fan control switch is. I'm thinking the small sender thats installed in the head is for an idiot lamp and not a fan controller as the 79 engine ran a fan off of the water pump.
I found this fitting Pic and pulled it thinking it was tapped into the coolant jacket. It isn't. What gallery or void it's taped into is the question. There was some sooty dry oil like deposits in it and the fitting passes either vacuum or hot air through all 3 ports. At this point I'm just going to plug it with a threaded plug. Anyone know it's function?
Spent a couple days on the electrics. Removed the regulator and installed a terminal strip and a 12v to 6v resistor in it's place.Pic
Started going through the rats nests of wires. I now have hi/lo headlites, parking lites, turn sigs, tail lites, brake lites and dash lites. I've decided to add a headlight relay.
As for the OEM gauges. The ammeter works. The oil and temp gauges weren't hooked up and would read to low for this 250. At this time I'm leaving them be and will be using the new gauges. The gas gauge shows no deflection with 6v applied to the correct terminal, with and without the sender connected. The sender does show approx 10ohms. Going to use a new gas gauge for now. The overhead electric wiper is only 1 speed but at least it now works. I'm leaving it as is for now also.
The more I do, the more I find.....

The mystery fitting is a constant dual vacuum source. It's a little unusual to be cast out on the opposite side of the head but it's par for the course on this odd ball integrated head 2bbl 250.....

Discovered why someone applied nearly a full tube of gasket sealer on the thermostat housing. It seems the upper housing was correct but not a correct match for the bolt on lower housing. The upper half has offset bolt holes and the lower half has in-line bolt holes which just so happens to match the upper housing on my freshly rebuilt 54 235. Not only were the housings not matched up correctly but the thermostat wasn't centered in the upper half. How it didn't leak is amazing. It's a testament to powers of permatex...... So I bolted up the 54 235's upper housing and it worked perfectly. Had to find a new upper radiator house with differing sized ends....
Pic
Pic 2

Removed those smog pipes and plugged the exhaust holes with M18x1.5 bolts.
Pic

Installed the 1/8NPT fan switch in the head and installed the new temp gauge probe in the lower thermostat housing. Both worked pretty good. The fan cut on at 200 and dropped but the temp didn't drop below 185 so it stayed running. It avg about 190 degees during testing. Removed the electric oil pressure sender and installed a new copper line for the ne woil pressure gauge.
Pic 1
Pic 2
Pic 3

Got the gauges installed. Oil pressure cold was 35 at idle, hot was 20 at idle. Temp avg'ed 190 degrees.
Volts = 13.5.
Pic

With all that said and done, I'm still chasing either an elusive vacuum leak or too lean condition. I finally got a double D adjustment tool to see if I can make the idle/low speed mixture richer to see if it makes any difference and the danged bit dropped out of the flex tool and found it's way down in a void somewhere between the intake and exhaust manifolds from which there is no return. Perhaps I'll try to retrieve it once it's cooled off or just go pick up another.

Volfandt, congratulations on the great progress you're making. Just one comment, I'm betting you will do a mild wire tuck... yes? I don't believe I've seen a better opportunity to clean up the previous owners wiring and plumbing.

Keep plugging away, you'll get there.

RonR

Spent a past couple days troubleshooting that elusive vacuum leak and am reaching the conclusion that this integrated head must be suffering form the same affliction that they've become notorious for, it's either cracked, has a burnt valve in cyl #3, leaking head gasket or leaking intake to exhaust gasket (that tin can looking separator visable down in the intake manifold to exhaust manifold preheat chamber).
I can get it to idle at 700 rpm with a wavering vacuum reading of around 19" but the rpm is hunting and can't be adjusted out via the mixture screw. At fast idle it'll draw a steady 21".
When I place my hand over the primary venturi it will increase in idle and smooth out (classic vacuum leak indicator).
I made up a plate to block off the EGR, disconnected & plugged every vacuum and still get no change in the idle fluctuation.
Using brake cleaner, I can spray it around the intake to head casting at cyl's 3/4 and 5/6 and get a rise in rpm. No cracks are apparent but the rpm will rise when spraying what looks like solid casting. There are head bolts in the area but it doesn't seem to be in that particular area. (very strange.....)
I adjusted the timing to get max vacuum at idle and got it around 19.5". No change. Retarded it 1" then 2" and even 4" of vacuum with no change. Verified there is no ported vacuum to the dist at 700 rpm idle.
It's possible that Varajet carb has problems but spraying around the manifold casting at the head and it increasing and smoothing out the idle is telling me theres problems with the intake in areas no where near the carb (again, very strange...)
Lastly I did a compression test and it returned the following:
#1-130
#2-145
#3-100 (wet and dry)
#4-155
#5-150
#6-130
All but #3 look good.
So, I'm looking at 2 differing plans of attack, try to find a good older non integrated 230/250/292 head and manifolds or just go ahead and do the more common swap to a SBC. Either will require reworking the exhaust which is one of the nice sub assemblies on this danged thing.....
The good news is all the new gauges, electrics and the TH350 works and will bolt up to an SBC.

Over the 250 Dave...

My unwanted 2 cents: Swap heads on the 250.

This has been interesting and unique reading. Tons of info here and everywhere else about V8 swaps. Not so much when it comes to the 230/250/292. Plus, I think an in-line 6 of any sort looks much more at home in an AD truck.

Then again, it’s not my truck or checkbook.

Alright, decision has been made. Will be pulling the 250 and going with a SBC 350.
At this point I have 2ea 350 candidates, a 70's version thats currently in a daily driver with no major problems except it doesn't produce enough HP for the owner. He's got a brand new 383 stroker awaiting to swap within the next week or 2. He'll keep the carb & headers but otherwise the 4-bolt main engine will be complete and ready to drop in the Jimmy and bolt up to the TH350. I'm liking this solution as it's a quick turn around but the cost is higher. I've got a QuadraJet and adapter plate just itching to bolt up to a V8.

The other is a nearly complete 96-98 5.7 Vortec w/the fuel injection intake and roller cam. The injectors have been removed but has the distributor, all the pulleys & brackets and manifolds. It was supposedly pulled from a wrecked vehicle (model unknown) and has been sitting on a pallet in the dry for ? years. It'll need to be gone through before I'd drop it in. It's got the 4 bolt per side fuel injection manifold to head config which my research indicates that these should be the very "good" factory 906 or 062 Vortec heads. This engine can be had pretty cheap and is probably the better long term solution but since I'm not leaning towards going with an ECM for the truck it'll need to be "down graded" to run a carb, and at this point the carb in question is the afore mentioned QuadraJet I just happen to have. Aftermarket intake manifolds are available.

I can also get a 700R4 on the cheap which I'll probably do for the future. It's been sitting for ? years in the same dry as the 5.7 so it'll need gone through also before it's put into use. I'll be researching that.

I thought I knew SBC's until I started researching them again. Theres just enough "gotcha's" to where one just can't go willy-nilly into the world of SBC's unless one has a ton of $$$'s. I don't LOL....

I'll be pulling the 250 soon and will make anyone who may want to try a later model 6 banger in a Stovebolt a great deal on it.
Since I've already got a Stovebolt 6 Chevy thats going to stay that way, I'm going top have alittle fun with the Jimmy.

Dave

Thanks for the update!

When you get the TH700 rebuilt, upgrade to the "Corvette" clutch drum for the overdrive unit- - - -it carries a couple of extra clutch discs and makes for a much stronger OD system. Don't let the old 250 wander off to scrap- - - -I could probably use another one to add to my stash of "one of these days" projects!
Jerry

Good info Jerry.
Got to spend alittle time on the Jimmy today. Pulled the front clip to get better access. It had been off before so the bolts came out pretty easily but it was missing a few..... Found a few bad spots but nothing major. Got the engine ready to pull, gonna pull the engine and tranny as a unit.
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Took a few pics of the 250's motor mount setup, perhaps those thinking of a 230/250/292 may find them useful.
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While awaiting the replacement SBC, I've moved on to the brakes. I knew there was a problem as shortly after I put it up on brake stands I noticed a puddle of brake fluid collecting directly under the Master cylinder (M/S).
Best I can tell the power booster is an 8" universal single power booster and the M/S & Proportioning valve (combo valve) is for a 71-73 Mustang/Cougar. I'm going to post a few pics of the disc calipers as they appear to match what I see on Rock Auto for an 82 C10/Caprice/Impala. So it's looking like a hoge-poge brake setup.
Besides the leaking M/S and a power booster filled with brake fluid and not able to hold vacuum, the disc pads are too tight against the rotor making it pretty hard to hand spin the rotor. Upon disassembly the shoes look almost new and the rotors look to be in good servicable shape. It's possible the piston could be sticking in the caliper so it looks like a rebuild of the calipers are inorder.
Since I'm going to have to replace both the M/S and booster I'm debating whether to go with a new GM/Chevy booster kit (new booster, M/S & combo valve) or just replace the booster and M/S with the same Ford units. I've found a full Chevy kit on ebay for under $200 and can stay Ford for under $150. Either choice will be a rebuilt OEM or new Chinese....
It's hard to tell what the original rebuilder did and what some later owner did as I think this truck had an SBC at one time but I'm inclined to think the brake setup was in the original rebuild and that it worked. Unfortunately it no workie when I got it......
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A couple steps forward and a 1/2 step back.....

Spent a good part of a day and a 1/2 searching for booster rebuilders and calling/talking to many of them and awaiting pricing from them. The cost to rebuild a booster is about double the cost of a new or already rebuilt booster from a FLAPS. Think about it for moment, kinda crazy isn't it...
One of them shared what model the booster came off of, a 1975 Pinto and he even said to try and find an already rebuilt one. Good fellow, I owe him a lunch......
So I ordered a 75 Pinto duo diaphragm booster & master cylinder from a FLAPS and got it in 2 days, free shipping and a 20% discount....
The booster and master cylinder will bolt up to the under dash subframe that I didn't want to replace, has the proper length input rod and is basically a direct replacement, no modification needed. I decided to go with the Pinto powerbrake M/S since logic would dictate that they'd work pretty good together, and it physically looks just like the bad one on the Jimmy.... I'm going to guess whomever made this kit up back in the day liked the compact size of the Pinto power brake setup. Thats the 2 steps forward.

The 1/2 step back is I'll have to replace one of the short brake lines from the M/S to the Combo valve (proportioning valve and residual valve). The bad M/S uses a 9/16 X 18 primary port and the new M/S's primary port is a 7/16 X 24. Both have a 3/8 X 24 secondary port. I don't have a tube fitting kit so I'll have a local hydraulic shop make it up for me. I'll guess the kit M/S was replaced at one point with either a Mustang, Galaxie or whatever Ford model M/S they found. A 3/8 to 9/16 adapter made it work.
In the whole scheme of this project it would appear to be small potatoes but I've got atleast 2 full days (16 man hrs) in just this small part of getting the brakes serviceable....
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And we have brakes! When I pulled the original booster & M/S a couple washers fell from between the booster and firewall. I took note and carried on. On reassembly I didn't include the washers and soon discovered the rod that inserts into the M/S was sticking out way too much. So much that it couldn't be adjusted out which kept the M/S from seating in the booster. So yep, those 2 washers plus 2 more and a couple R&R's of the booster & M/S finally got it right. A little free play on the boosters input shaft and a little free play in the boosters output shaft was alot easier said than done.... A local hydraulic shop charged me $9 for a new 10" steel line w/new fittings. After bench bleeding the M/S, hooking it back up to the combo valve, cleaning up and reinstalling the calipers I got full pedal w/o having to bleed the system.
That quick fix wireing terminal just doesn't look good so I'm going to cipher out a way to hide it. A way other than putting it under the dash where contorting skills I no longer possess are required...
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