VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc 261

This is getting to be a circus. My wonderfull 235 has a big crack in it. It was bondo'd and painted. So I turned it into a giant door stop. But, I got a late 261. Packed in grease, bored .020" But, it has a bad head. I intend to put my 235 #848 head on it. That should work right? Also the guy I got this 261 from gave me a box of new lifters. But, they are Hydraulic. The valve train on the head has tappet screws. Is this possible? Or did he just get the wrong lifters?

All 235 and 261 engines have tappet adjusting screws, as far as I know the rockers and rocker shafts are the same on both engines, probably different valves and valve springs. I would drill the 848 head and use all the 235 valves, rockers, and pushrods. The hydraulic lifters on 235 engines used a different cam than a mechanical valve lifter engine. Also there is a problem with using hydraulic lifters in a early 261. The early ones didn't provide an oil supply for the hydraulic lifter. The 848 head off your 235 will work on the 261 engine. Some guys say that you must use a 261 head gasket and drill out the two small water or steam holes in the 848 head. Once upon a time I built a 261 engine by buying a new 54 261 short block from the Chevrolet dealer and then replaced the 52 235 babbit rod block in my 52 Belaire. I used everything off the 235, head, pan, water pump, hydraulic valve lifters, pushrods, manifolds, starter, flywheel, distributor, carbs, motor mounts, generator. I was too ignorant to know that the hydraulic lifters and head wouldn't work. By the way it all worked fine. I think that I collapsed the hydraulic lifters and used them like solids. I ran the engine that way for several thousand miles before I changed out the lifters and camshaft for a mild McGurk street cam and Mallory ignition. I never did drill the 52 235 head. The only problem I had was with the old 6 volt battery and the threadbare battery cables, that would not start the engine after it got heated up, for the first few hundred miles. I rebuilt the starter put in a new battery and new battery cable. This is the 52, picture taken in 1961

I sure appreciate the info. When you say drill the head. Where and how far? It looks like the 261 head has spray nozzles like the 216 for cooling. Am I correct?

Are they hydraulic lifters or just LOOK LIKE HYD. LIFTERS. The later 235 and 261 engines use a different looking soldid lifter. They are thinner in the middle as the oil must pass around each lifter (from the end to the center of the engine) and in the center the oil passes up to the rocker arms.
The 235 and 261 heads are basicaly the same except the 261 head has a lower compression ratio (larger combustion chamber due to be used on a larger displacement engine) and had the steam holes....Nothing like the cooling in a 216 head. If you use a 235 head on a 261 the compression tatio will be incresaed to about 9 to 1.

The 848 heads I have seen used were drilled by placeing a 261 head gasket on the 848 head and marking the holes, they are drilled into the water jacket. Compare the 261 head closely to the 848 head and you can see where they are different. These holes are used on the 261 because the cylinders are cast siamesed, there was not enough room to cast in the same type of surrounding water jackets with the larger bore of the 261 cylinders.

Ok, I checked the differences on the head. I see exactly what you mean. Thanks Mack. Gene, From the top, the lifters have an internal Clip, and you can push the center in. There is a hole in the chamfered ring that goes inside the lifter. The little boxes are from about 20 years ago, but, the part number is HT-761. On the boxes it says "Hydraulic Valve Tappet Assembly" They are sealed power brand.

Mack, Which combination of starter/flywheel/clutch did you use?

I used the ones off of the 52

Then they are Hyd for sure. You will need a set of lifters for a 1959 and up 235 or 261 truck engine. The Chev part number was 5231800.
Are you sure its a 261 engine? Are you sure as to what camshaft it has? solid or hydraulic. TheCanadian Pontiacs used a 261 engine with hyd lifters. Cam must match the lifters. Can you see a casting number on the cam.....and block.

Mack, there are a total of 6 holes, right? Also, They are .160" diameter? And located between 1&2 3&4 5&6?

Gene, where would the # on the cam be found? It is still in the block. Would I be able to see it from a lifter hole, or fuel Pump housing?

You would need to remove the oil pan to see it.Its usually on the "rough" part of the cam, between the lobes and towards the front.

Ok. Here is the #'s from the block.Passenger side. 3837004
Then it also says, CON 4 A96. On the pad next to the Distributer it says. 0T34936F56U A. Stamped over the top of that is 61408. Driver side says 7 004.

I think thats a 235

Also, the motor was green.

The 1954 261 engines were green. The 1955-62 261 was yellow.
The heavy duty 1955-62 235 truck engine was green
Thats why the block casting number iis needed to identify for sure.
The later 261 also had a ful flow oil filter plumbed into the block with large pipes.

OOOO - just noticed you gave the casting number.....Thats a 1956-57 casting number.....could be a for a 235 or 261.
The stamped numbers don't compute. The U after 56 should teel the story but no U is listed for 1956.

I would still remove the pan, measure the bore and get the cam number so you know what you are working with

The motor was bored over, but, the cylinders are 3 5/8" exactly

The 235 had a 3 9/16 bore. Doubt if you could measure the .020" over bore with anything but a cylinder bore gauge.
The 261 has a 3 3/4" bore.

??????

Which means, it is a heavy duty 235 with a 1/16" over bore! Right?

Also, the old pushrods that came with the engine are solid. Thus, I have the wrong lifters. Correct?

If the engine was bores it was repainted at some point I would bet and the color means nothing.....I would doubt if it was bores 1/16".....but its a 235 for sure.
The type of cam is important as to what lifters it will use. If it has lifters in it now they probably are corect for the cam......whould need to get it running to determine if they are solid or Hyd unless you have the side cover off.

I am working getting the cam out. If it helps, the lifter bores have 2 holes, about 7/16" going through both sides.

Ok, on the cam, the only #'s I could find is as follows

E2 GM 56

3836386

That is a Hyd lifter cam used in 1954 and 1955 Power Glides and all 1956-1958 passenger cars. It was the highest lift Hyd cam made.
Increased the power in a 1955 stick with the low lift cam from 123 at 3800 rpm to the Power Glides 136 at 4200 rpm. In 1956 the engine was rated at 140 hp at 4200 rpm.
In 1959 they went back to a lower lift cam to provide better low end torque and fuel milage,
The proper stronger valve springs for that year must be used with that cam.
The GM56 probably indiactes the cam was made in 1956 and the E2 would be May 2nd.

If the engine was bored out the size will be stamped on top of the pistons....like .020