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I recently swapped a '56 235 into my '53 GMC 100. There were a few issues to sort out, including a carb rebuild. I took care of that and now it's overheating and running at a faster idle. I'm thinking its running lean AND has crud in the cooling passages because it didn't heat before the crab was touched (Rochester) and NOTHING comes out of the rear block drain plug (driver side). Thing is, it starts up pretty well cold, which makes me second guess the lean condition. I put in a bottle of rad flush today and messed with the timing a bit. Any other tips/ideas???

Take the drain plug out of the block & push a long thin screw driver in the hole. If you get it open put a water hose in the rad. fill & run water with the engine running. When it starts running out clear you have got about all of it out that you can.

Or put the water hose in the drain fitting, more pressure, float big pieces out top with larger holes.

Ed

I tried a combination of both of these without success. I removed the drain fitting and prodded around with a scribe as well as shooting some water in there. I would get a trickle and that was it. Granted, I wasn't too persistent with the scribe or forcefull. Perhaps its time to get a little more violent with it... I'm going to pull the thermostat just in case it's sticking or causing some other trouble and try again.

Gustave, GET aggressive with a piece of coat hanger wire. Just route that out and keep working it until the GUSHER that happens when you break it loose. Work on it until it happens. No matter how long it takes.

Not sure if that will help with your overheating. Be sure you have a 180 degree T-stat with a 1/8" hole drilled in the side of it just for good measure.

Lean, check the mixture screw. Start by turning it all the way in, then backing it off 1-1/2 turns. Go from there.

Thanks for the help fellas! I'll give it a shot Sunday evening... if I finish my 2500 word assignment by then...

Search this forum, there were several recent threads about this.

I spent the majority of the afternoon on this to no avail... I rinsed every which way with a garden hose after removing the thermostat.I poked around the block drain plug and got a tricke; not much water at all. I suspect there is something obstructing water flow or maybe the pump is bad. I'm not sure if this is normal, but when it starts to heat up and I shut it off it spews its guts out. Any ideas??

I've used muratic acid , been a long time ago. Here's a link that might help, you'll need to modify for your engine but I think it provides some good information.

http://www.moyermarine.com/forums/showthread.php?t=127

You may have to pull the freeze plugs out. You must have a lot of junk in there.

For $26 (cost of a head gasket set) should I just pull the head and see what's going on in there??

Gusco, the muratic acid is very inexpensive. What you'll likely find is built up rust, scale, and calcium or other minerals that will be difficult to remove by manual methods. Good luck and let us know what you end up doing to solve the issue. Knowledge is power.

What finally worked for me was to warm up the engine, take out the drain plug, take off the thermostat, get an air hose with one of those small conical rubber ends on it so you can get a good seal in the drain plug hole and give a good blast of air into the block alternating the thermostat opening and the drain plug until it breaks loose. Kind of rocking the crud plug. Get it flowing, then use the Muriatic acid to clean things out.

Interesting... I was thinking of getting an air gun and blowing through the drain plug in the back of the block. I'll give it a shot.

So I had a little time today and I pulled the carb and took the rad to get checked. The rad had a minor crack by the drain valve that was repaired and the guy also put on a new overflow tube. The carb was another story. The retainer had come off the top of the plunger and that somehow resulted in the rod getting jammed up and bent. I was able to straighten it back up and put a new retainer on. I'll report back once I get those back on there.

Remember that if you use air to clear the rear drain crud, at least take the rad cap off if you don't take the thermostat housing off....don't want to damage the radiator and that crud plug need somewhere to go. If the engine is full of water , which is not compressible, and sealed will not be as effective.

Correct. The rad is not reinstalled and I'm still going to try to clean out the passages before reassembling.

Freeze plugs need to go and not difficult to replace. Or just knock out the rear one and see what's going on in there. Every old motor I've taken apart had at least a coffee can full of krapola inside the cooling passages. Best of luck

I worked on the motor for a little while last night. I put some air through the rear drain plug and I could hear it gurgling, but there's definitely an obstruction. After working it for a while I got a more consistent trickle, but it's still a trickle. I was unable to get the freeze plug out because the throttle linkage was in the way. I left about a half gallon of vinegar mixed with a half gallon of water in there and I'll drain it tonight and rinse with water with sodium bicarbonate to neutralize. Lastly, I will try to get the linkages off and rinse through the freeze plug opening on Monday.

Got that plug pulled out and cleaned up what I could in there and still could not get a flow! BUT I stayed with it for about two hours; poking, prodding, and getting in there with a magnet, welding wire, screw drivers, etc. After a good while, I finally got it to flow!!! Now I'm just waiting on a new gas tank to come in today and we SHOULD be back on the road.

I decided to run the truck for a bit on the old tank to get it closer to empty and was running very rich (black smoke). I took the carb apart a few times and the only thing that caused an improvement was going with the float set parallel to the carb body. Right as it started to improve, it ran out of gas. I'll get some fresh fuel in the new tank and report back. The temp has definitely improved (180-190F).

Got 5 gal in there and fired it up. It is not running well and I suspect the carb because it was running better without being rebuilt. Now the idle fluctuates and Im getting less vaccuum (15 vs 20 inHG). The idle will suddenly get healthier and vacumm increases to 18-20 inHG, but then it will go roght back to crappy after a few secs. I also know I have an exhaust leak between the manifolds... Any suggestions?? Should I just go for a Carter?? If so, what models fit and have a manual choke?

Ps- I messed with the timing going both ways and the situation did not improve going either way.

I need some help here, fellas!! I went out for a short drive yesterday and it ran...ok until I hit 3rd. Then it would just shudder like crazy and surge. I think I'm running lean. Something isn't working right in this carb. I found a Carter on ebay that needs rebuilding. It doesn't have a model # posted, but the owner claims he found it with a tag that said "53-57 Chevy truck" on it. I should've kept my Zenith carb

Gusco,

If the carb is your problem:

1. You should have kept that Zenith carb.

2. Measure distance between the mounting holes/bolts on your car/manifold and make sure the "53-57" Carter (replacement) carb's mounting holes match (it should).

A Carter carb seem to be a good choice - get one from/for a 235, if you can.

I'm leaning that way (carb) since that is all I messed with (aside from the cooling system). The problems began once I rebuilt the carb. I've gone over it about 5 or 6 times now and it all looks ok... I'm hoping you more experienced guys will chime in on if this sounds like a carb issue or not.

Not sure why I keep updating despite no feedback, but here's the latest: I found a cheap Carter on eBay that will hopefully fit AND clean up nicely. About $26 including shipping. It's supposed to have had a tag reading "'53-'57 235 car or truck" on it. We'll see when it comes in.

With 1622 Views a lot of folks are surely following along with you. I'd post but not sure what I can contribute to this?
Rest assured, we're watching, and reading. Thanks for the updates.

Good luck with the carb. I looks like it should be a good fit.

Let us know how this works out. We have our fingers crossed (as do you, most likely).

You seem to be researching and plowing along just fine on your own thus the reason for minimal feedback. Keep at it, your doing fine and educating yourself along the way.

Thanks for chiming in. I don't know a whole lot, but I try to contribute what I can to the forums I participate in for the sake of those who may have the same problems down the road. Hopefully Google will direct them this way.
This truck sure doesn't seem to want to come back to life...

Sure it does...
Is this only an exhaust leak (or, how was this determined---I might have missed this if it has been explained already)?

Keep charging!
Brad

I had noticed some soot on the block when I purchased it. It was contained to pretty much the center of the block where the intake/exhaust manifolds bolt together. While messing with the carb I witnessed a backfire through the gap between the manifolds and the soot has been ever increasing through there as well as the popping/noise. I have sprayed around the manifolds to see if there is some sort of intake leak leading to a lean condition, but the motor did not respond. So, I am thinking it is strictly an exhaust leak.
I tried to separate the manifolds since I have a new gasket laying around, but the bolts aren't having it. I do have my set of manifolds that haven't sold from the previous 235 and have been considering installing those. What do you you think?

(edit- I may be confused on which set of manifolds you tried to separate, but...)
Leave them together then. It might be a bear of a task to obtain correct Alignment, seal, and to not break the bolts when installing your old manifold if you do take them apart.

I believe we (the machine shop) had to machine my engine block to get my manifolds to seal perfectly (on re-install). The machinist/engine builder said, "I wish you'd have just left them together."

Handle the carb issue first; I am not experienced enough to know if a leak on your exhaust manifold would cause the engine issues you're having-- Good Luck!

Brad

I have been following this so far. You fixed the water flow issue. Good work. The surge and stumble issue would have me looking at air leaks and..Vacuum leaks. A simple test for a Vacuum advance leak: Pull the vacuum line off the carb. Apply a vacuum(yep, suck on the line) and block the line(yep with your tongue). If the Vacuum holds(you can tell) it is OK. If it does leak(and you can feel it leaking) it needs to be replaced or the fitting at the advance is leaking. When the carb is apart(Rochester) make sure the "power valve" piston is free and will move in the cylinder. A caution: The ball bearing in the top of the stand off( the one on top of the power valve must be one of the smaller ball bearings from the kit. The bigger ball will fit(sorta) but it will stick in the cover nut(not fun to remove) and the power valve will not work. I have seen some with the top of the piston rod deformed. Again not good(it can be fixed but is a pain) Setting the float is not too hard. Parallel to the cover. Drop set as instructed and then the close point. Again watch the floats move, they both must clear the gasket and...not rub on any thing. Not a lot of room but a bit of tweaking and it should be good to go. After all is done recheck the measurements A lot can move while you focus on each issue alone. Note: Some carbs require the gasket to be under the standoff(power valve support?) and some, do not. A gasket under when the carb does not need it will make the standoff tilt, or be too tall. No gasket under the support when it is needed will make the power valve non- working(only a small vacuum signal to move it. All of these things can cause the surging and stumble you have described.
Does the heat riser valve move? It is in the exhaust manifold and helps the intake get warm. If stuck open it takes forever to get the intake warm( driveability sucks) Cold intake allows fuel to puddle and (the mixture is unstable), can cause some Stumble and lumpy idle issues. If it is stuck closed, you will over heat the intake and most likely "vapor lock when the carb overheats. It must move and the "spring" should open the valve as it warms up. One more thing to look at: The base gasket and isolator(plastic thing between the carb and intake manifold). Is the isolator in good shape? Some get cracked(I have no idea how this happens) if it is cracked find or make(if you can) a new one. If it is chewed up on the mating surface(either side) you can clean it up with a plate of glass and some sandpaper. The base gasket, in most cases has a notch or 2, sometimes 4 on the inside of the big intake opening. This must line up with the hole in the base of the carb. Turn it around or flip it over until it matches. Then install so yo know where it fits best. Idle mix screw is set about 1 and 1/2 turns out to start, then adjusted for max vacuum( book says to turn in till RPM declines or it stumbles then back out 3/4 turn) Most of the time the setting with the gauge is very close to the book procedure. remember, the above long winded applies to the Rochester B only. With all of those things out of the way, I would look close at the exhaust leak. Not critical all by its' self, but it might be as good a time as any to replace the gasket. Watch for the alignment rings you will need them to reassemble. The last thing I would look at is the points. Spring tension good? Gap good? Is the rubbing block stable? Contacts clean? Simple stuff I know. But it all matters. Post any progress, and know these and other suggestions are to help as best we can.

Interesting that you mention the gasket. I originally replaced the gasket with one that looked like the one I took out (no gasket under the standoff. Since it didn't work, I switched gaskets a few times. Perhaps the issue lies somewhere in the power valve...

The Carter came in and it is in about the shape I expected it to be. There definitely is a tag on it that reads "Chevy Truck 53-57". The Carb has a "1895" stamped on the float and "YF4375S" at the base near the throttle body. The throttle body is quite rusted, there seems to be a linkage missin at the bottom to the accelerator pump, and the screw for setting the idle is missing. I'll give the powervalve another shot and if it doesn't cooperate, I'll get on this YF (once I verify that the throttle body fits the manifold.)

According to that list I have a 230/250 carb. I put it on the manifold and it fits. Can anyone confirm if it will work on there ('57 235)??

I can't confirm anything, but if it bolts on and the linkage can be easily connected, I'd give it a try on a 235 (In my case, ignorance is bliss).