The Stovebolt Site Forums The Shop Area Engine Shop 292/89mm 4 speed first drive results

Well the 292 is in; the 4 speed overdrive is in and the first drive is out of the way. Here's what I'm feeling after the first run:

Engine feels about half as powerful as the old stock 250.

Overdrive is nice, but the tranny is not nearly as smooth as the old stock 3 speed.

The speedometer is waaaaaaaaaaaaaaaaaaay off.

Rear tube header leaks. Leak is a result of a mishap that happened during engine installation (long story). Front header is airtight.

Engine is running a little rich with the 500 cfm Edelbrock. Engine starts quickly and the electric choke is absolutely great.

Flowmaster exhaust sounds simply awesome. At idle it could pass for a bent 8. I went with a single muffler with 3 inch inlet and dual 2 1/2 inch outlets all the way out back.

For some strange reason the temperature gauge doesn't work.

Throttle cable setup works horribly. Will need lots of adjustment. Lots!

Whining noise coming from timing area. Is this common for new straight six gears? My uncle seems to think this will disappear as the new crank and cam gears wear together.

My priorities to fix things are (in order)

1. Exhaust header leak.
2. Throttle cable.
3. Fuel distribution (lean out or hotter plugs).
4. Temperature gauge.
5. Speedometer.

Any advice or feedback you guys could share would be highly appreciated.

Thanks for all your help!
-ftyler

For what it's worth... I am a believer in a bead of high temp silicone sealer around exhaust ports on both sides of gasket and installing while it is still wet. I thought it would burn out but a friend convinced me to try it and proved me wrong.

Just wondering,,,,, did you re-install the cam thrust-plate screws? was the engine block allign bored?(wondering about the whining noise).
-
Did you make sure all the air is out of the system? If so, I would try another guage.
- as for the carb adjustment, I would suggest the artificial enrichment method >> using a tachometer and an unlit propane torch, with the engine running and warmed, aim the unlit torch down the carb for about 3 to 5 seconds. You will want to see about an rpm gain of around 20 to 25 rpm per each side of the carb primaries.

Fred,did you buy the timing gears as a matched set?I am told there are two different timing sets available,a slightly different pitch on the gears.My experience with the Edelbrock Carb is it may run rich on normal driving,you probably have to change the metering rods and or main jets.The tuning guide that comes with the carb is helpful.On a modified engine, your engine may need a more aggressive mechanical spark advance to improve throttle response.That along with a rich mixture will make the engine doggy in normal driving.On the A833 trans;my wife said the one in her 51 truck is more "trucky" than the Saginaw 3 spd it replaced, but the OD gear is worth it.

Luke,

I'm not sure about the align boring. I bought the short block from an Atlanta engine retailer. The only thing I can say for sure is that the noise is definitely coming from the front timing cover area (which, of course, is where the gears are located).

Yes the thrust plate screws were installed securely, so that's not an issue.

You know what? I didn't even think about "air" in the system. That might explain the "hissing" sound we heard each time the engine was shut down. How do you remove the "air" from the system? Should the engine be turned over several times with the plugs out?

FT - half the power of your stock 250? Don't tell me that!!! What is your distributor out of? Stock, HEI? As Tony said, sounds like your timing may be retarded.

As for the temp guage, if your cooling system has an air pocket in it, you should have still seen something on the guage. Did your thermostat have a bleeder hole in the upper quadrant to let air pass through? Are you getting flow through the heater core?

Did you use teflon tape on the threads of your sending unit (assuming you have an electric gauge/sending unit)? If so, the sending unit is not grounded, so no gauge action. Use a paste sealer or none at all.
What rear gears do you have? You didn't put anything lower (numerically) than 3.55 did you?
These guys will talk you into 3.08's if they can, so you gotta watch them :p .
Most guys don't like the rpm's in GM trucks (from the high numerical gears), so they gear them "up" to reduce freeway R's, save fuel, engine wear,etc.........
Those stock gears are why you can out pull a F O R D any day...........F O R D's always have "tall" (low numerical) gears. Great on the freeway, but not worth a %^&* off the line or pulling/carrying a load.
Glad to see you went OD........

Ken,

The "half power of the 250" is a tad of an exaggeration. But the improvement is not on the order of magnitude I expected given the increases in cubic inches (50+ more at .060 overbore), camming, carb and exhaust. I realize that I've got to get things tuned and get the engine broken in. I also took care not to get too deep into the throttle. I expect improvements in performance as things are tweaked and the "bugs" are worked out.

The distributor is stock HEI out of an early 80s chevy van. The top is brand new (cap, coil, rotor) but I didn't replace the vac advance. That I can (and probably will) do easily. I haven't checked the water flow to the heater yet. Will do.

Tony,

I've heard the Edelbrocks are extremely easy to tune. So I'll take your pointers and play around with those once I get back to the truck (it's an hour away). The timing gears were already installed by the rebuilder when I bought the short block. It was all put together. So I'll assume they are a matched set.

gmc248,

I used a "paste" type sealer on the sending unit. But you know what? It's almost like a liquid teflon tape. So it might not be grounded. I'll check into it. Thanks!

Any suggestions regarding the speedometer? Will I need to find another cable to make the speedometer work on my 66? What do I ask for? The one that matches the transmission?

Thanks for the advice guys. If you think of anything else please reply or email.

-ftyler

Removing air:

The best thing is to drill 1 or a few 1/8" holes in the flange of the thermostat itself, so that even when it's closed a little water can flow. Re-assemble, fill with water, and idle the engine until it's warmed up. As it pumps water, it will clear out any air bubbles. Add more water as needed.

(I don't usually put anit-freeze in the first time. Seems like you always wind up opening up the cooling system for one reason or another; why create the drainage hassle? Once everytingis good, drain and refill w/ antifreeze.)

As for the power level, rich mix = less HP. Likewise, if the timing is off you will lose power.

But overall, congratulations!

Cheers!
George

Speedometers are geared off of the output shaft of the transmission, so unless you changed the rear end, it should be the same. I don't know about 66, but old speedos have to get new gears to adjust them, while new speedos have some sort of adjustment on them. Changing your speedometer cable won't do anything at all. Good luck on getting the bugs worked out.

The 80s HEIs have a horrible advance curve. Short and sluggish. Bleah. You're gonna have to recurve the dist advance to get any pep.

And the speedo gear is setup for whatever rear axle ratio the donor vehicle had. Gonna have to figure out what tailshaft drive and speedo driven gears you have to correct speedo reading.

Gonna need more info to chase the gremlins out of your dash gauges. Electric? Stock? what?

On the HEI, I would replace the vac advance with an adjustable unit, also replace the weights and springs. Hotter coil and module will help, too. Then you have to have the balancer set up for advance timing, easiest way is with a timing tape that wraps around.

One problem you have with power is that you have loweer the bottom end torque with the larger carb and headers. To seal the leak, use ultra-copper RTV on both sides of the gasket, and let it cure at least 24 hours before starting.

On the timing gear noise, I would call the engine builder and ask why it's so danged noisy. It shouldn't be.

The timing gears in my 292 were noisy at first. Don't know why for sure, but they did quiet eventually.Sounds like you are having fun. Maybe I will get mine on the road this year, depending on how many more kids around here need braces on thier teeth.

Use the Moroso mech advance curve kit. The Mr Gasket parts store kits are useless. Shoot for base timing of 12-15 degrees, 34-38 degrees all in by 3 grand. Vac advance will add an additional 10 or so on top of that when cruising. Timing tape or a dial-back light is essential.

The larger cam, manifolding and exhaust system has cost you some low-end. But properly tuned, the 292 should still outrun a healthy stock 250.

Guys,

Thanks for all the advice. But if you'll notice near the bottom this post was "resurrected" after 4 months of inactivity. So some of these issues have been resolved. Specifically.

1. The timing gear noise has disappeared (nothing changed - just normal driving).
2. The engine feels more powerful now than it did before.
3. The throttle cable issue has been resolved. Replaced the expensive Lokar cable with a cheap one from AutoZone. Throttle now works like a charm.

The only other issue I'm still concerned about is the temp gauge - and I have that one figured out (bad gauge - the new higher voltage alternator must have fried it). The others I'm not too concerned about. Still running a little too rich and now the speedometer doesn't work at all . But I can easily cruise with the state highway traffic and push cars out of the way on the local interstate, where traffic averages 75 mph. I have a new speedo cable, yet to be installed. If that doesn't work forget it!

-ftyler

guess we're desparate for a truck thread.

thaaaanks Ftyler for stoogin' us

Chiphead,

Since the ignition issue has been brought up I've been wondering. Won't the stock GM 6 cylinder HEI be plenty for my application? I would think it would be even a little bit of overkill for a 292, .060 over, with a small cam, headers and 4 barrel.

Will the changes in ignition that you and others have suggested really make that much of a difference in performance?

-ftyler

The HEI puts out plenty voltage for a strong spark, thats for sure. But the spark timing at different RPM (advance curve) is even more important than raw output. The spark has to happen at the right time to make max power with a modified engine.

The stock HEI advance curve usually gives 17 to 20 degrees maximum advance. Thats pretty short (not much advance) This means that you'll get base + 20 for total timing. The advance curves were shortened when HEI came out, cuz HEI came out during the smog wars, when engines were designed to run lean with low compression ratios and poor fuel. Running an aggressive curve on these engines wouldn't help them much from the factory.

For example, lets say your engine needs 38 degrees total at 3 grand. Well, subtract 20 degrees from that and thats 18 degrees BTDC at idle. Thats usually too much base timing. So if you back off the base timing so she'll start and idle, you don't get enough advance at higher RPM. The motor's response can be sluggish, sloppy and inefficient. The engine can run hot and use more fuel.

Usually re-curving a distributor is done by replacing the center plate, weights and springs. The shape of the center plate controls maximum amount of advance. The moroso kits provide weights and a matched center plate that lets the weights travel further and give more advance. The springs set the RATE of advance.

In my pontiac, I removed my center plate and reshaped it with a grinder to provide more travel. Careful to not remove too much material, as you'll get too much advance travel at really high RPM. (more a problem on high comp V8.) Now my car will smoke first and chirp second. No kidding!

Extreme example. For a NOS application, you must retard the timing 2 degrees for every 50 HP shot of NOS. So if you're running a 150 shot, you've got to retard the timing 6 degrees. 6 DEGREES! Thats the differance between winning a race and scattering a motor.

You really would be amazed how properly recurving a dist will help the crispness of engine response and mileage.

Hi-- You said the 292 seems sluggish compared to the stock 250. You also said you were careful to keep it light on the throttle with the new engine and all. Well, we've been running some dyno simulations with different cams, and even a pretty mild cam moves your peak hp and torque quite a ways up the rpm scale. As soon as you move past about 236 duration or so you start losing bottom end torque and horsepower fast. One combo we ran shows just over 200 horses at 4700 but it's a dog under 3000. Betwen 4200 and 4700 it ROCKS. (We just don't get to have it all. That's my dilemna. Do I want a rockin' hot rod engine, or a really good driver?)

A 500 cfm carb is probably about right. You may have to play with jetting some, but I think that when you feel like it's okay to stick your foot in that thing you are going to get a HAPPY SHOCK!

The advance recurve should get you about a 10% improvement in highway gas milage, but that depends on a lot of other factors. Replacing the coil and module helps some. Usually allows you to gap the plugs in the 40-45 range. On the V8 the module upgrade also buys higher rpm, stock limits to around 5,000. Another change that makes an improvement is an MSD-6 box, gives longer spark durattion, also helps smooth out lumpy cams.

BTW - Like Chip, I am not a fan of Mr.Gasket parts. Very low quality from what I have seen.

Thanks guys. This is really been a good lesson. I didn't realize how big of a role ignition plays in an engine - especially a mildly built engine.

I'm not sure how much improvement I can expect in gas mileage I can expect, with an ignition upgrade. I mean, at 70 miles per hour I'm only taching 2300 rpms. That's right in the cams' cruising range.

Fred T,

Does the MSD box work with or in place of the HEI coil?

What gears are you running Fred?

I'm running the stock 3.73s in the differential. The truck has 235-70R15 tires. But the 4 speed transmission has a 0.73 ratio in overdrive which lowers the rpms considerably. I don't even use overdrive on the highway under 60 mph. RPMs are just too low and the engine lugs too much.

YES!! 373's are good news at my house! Luke has some 373's that I am getting from him in the next week or so so I can swap out my 411's. The cruising rpm range your getting is what I'm looking for. I won't have the overdrive advantage but considering what your getting I think I'll be very happy with the swap. I spend a good deal of time on the hiway, and the gearing being to low is one of the main drive-ability issues I want to address. The other is worn out suspension, but I'm putting new springs and shocks all the way around this week end. YAHOO!
Bob

fleetside,

Before I made the 292/overdrive swap, I ran a straight drive 3 speed trans (with a 1:1) final drive. I still drove 60 COMFORTABLY on the state highways for miles and miles. And 65 was about my maximum comfortable cruising speed.

So 3.73s aren't that bad, even without overdrive. But I wouldn't step back to a non-OD trans for anything! Being able to cruise with and pass interstate traffic with ease in an old vehicle is great. But shocking to the people you pass.

-ftyler