Technical 292 question

I'm working on a 292 thats in a 35 GMC 1 ton, serial number Fo315ut1, this is off the pad by the dist, I'm guessing it might be an earlier block but don't know for sure, it has a stumble and I checked the vacume advance and it didn't pull in with the hand vacume pump so I ordered a new one,it also won't pull in at 20 IN of vacume,both are hard to push the lever and diaphram are both defective or does this engine make 30 in of vacume, the dist plate turns freely.
Thanks Aaron

 

The UT1 suffix code sounds like later production, 1980s? maybe

It should get vacuum advance with less than 20 inches of vacuum. It's not easy for us to tell how hard is "hard to push". You might need to disconnect or take out the diaphragm, and see how things move when it's not connected.

Whether or not this is the cause of the stumble...well, it's not too likely.

 

Squirrel your new picture makes you look like someone who developed rocket engines for NASA in the 1960s!

 

It's my Egghead picture. And it's from about 15 years ago.

 

You always give good advice -so now you have the picture to back it up.

 

Jim, I had it off the dist and the point plate moves freely, I have n o idea what vintage this is, although it has a pretty new dist and I wondered if that replaced the later module type of the later, although that would have nothing to do with it, when you try to compress the lever/diaphram you know it is hard when it leaves a mark on you finger,20/25 un won't begin to move the old one nor the new one got, I most likely am missing something here, most diaphrams I've replaced the lever/diaphram moves easy and with very little vacume.

 

It could be in bad shape inside?

There are probably some clues on the engine and distributor, to it's age, but all I can see is what you show me. Pictures are a big help. So are numbers.

 

Or is a current-day serial killer...

 

Where's the distributor located? At the front of the engine (later model), or at the center of the engine (early model)? And, how did you arrive at it being a 292? Do the motor mounts look "home-made"? Might help knowing exactly what engine it is, early or late. I am Butch/56sedandelivery.

 

Oh "that" 292. I opened this up expecting to see God's 292 made by Ford. LOL

 

nope , just a stump pulling chev

 

Butch, its the tall deck 10.78 in from pan rail to top of block, dist is towards the front,number on the dist side of engine by fuel pump is 3921970 with GM under it,all in raised letters. I didn't know the early late position on the dist.
Pictures:

 

That casting number was used from 63-76, apparently. There should also be a casting date code around there somewhere, near the starter possibly, the last digit will be the last digit of the year it was cast.

The suffix codes were one or two letters through 1969, and three from 1970 on. So if the suffix code is what you say, then it would be from 1970-76. The two character UT suffix was used in the late 60s on the 292.

HEI ignition was used starting around 1975. but it's easy to change the distributor.

 

It is easy to do a quick check of the vacuum cannister. Just push the plunger on the right hand side all the way in, and at the same time, block the end of the tube on the left had side with your finger. If the actuator lever does not move, the diaphragm is fine.
Assuming that the engine does not have a miss when the engine is idling or cruising and is only stumbling under acceleration, the problem could also be that the accelerator pump on the carburettor is leaking, or that there is a blockage in the accelerator pump circuit. It could be that you are just not getting a large enough shot of gas from the accelerator pump and the engine might be just running too lean under acceleration. This is a common problem that often gets blamed on the ignition system.
Bob
Bob

 

I swap a HEI in all my 63 and newer chev & GMC six cyl engines. Most times carb problems turn out to be ignition. However every so often a carb does need attention.

 

Thanks everyone for the input, I learned things here today and will make notes to go with the truck.
I have got into the habit of checking the vacume diaphrams of the old stuff I work on and quite often they are shot, the OT Ford I'm working on had a bad diaphram, this one though is good, the operator is what was haywire this time, I had grabbed my vacume pimp and an adapter outa the box to pulg into the diaphram,dumb ass didn't look at the adapter till it fell on the floor today and when I picked it up I notice there is no daylight thru it, turns out it is a tapered plug not an adapter, boy do I feel dumb.
Generally on a stumble like this I would've checked the carb but when I thought I had a bad vacime advance I got stuck on that, tomorrow I'll make a run for the carb.
Thanks again