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

Gene, is it possible to use flat tappet lifters and flat cam or must one stick with the hydraulic?

All lifters and cams for this engine would be of the flat tappet type.....an non -flat would be a roller lifter.
Yes, you could put a solid lifter cam and lifters in the engine.
The other cam sold by Chevrolet was the solid lifter cam used in the 6 cyl Corvette, 261 trucks, and 1956-1958 235 trucks. But its lift, etc. was no better than the hyd cam you have. You could find some other brand but make sure it was NOT made in China, its properly hardened, installed as per instructions and has a gaurantee not to have lobe problems.

If it had hydraulic lifters, wouldn't it have had hollow pushrods and special rockers? Or is that a more recent thing?

The Hyd and solid lifter engines had the same push rods, rocker arms, etc.

Thanks Gene

No the hydraulic lifter rockers and the mechanical lifters all have the same pushrods. tubular pushrods were introduced on the small block V/8 engines and were introduced on the sixes after the 235 and 261 engines were discontinued. The new single stud rockers were the first stock Sixes with hollow pushrods that oiled the rockers.

Thank you Mack!

One more thing. I was told that I must use VR-1 Valvoline, cause of the zinc. Supposedly, the zinc was removed from alot of other oils. Have you heard this?

I don't think that is so, unless of course you are building this engine up for 100% full bore racing. Will you be running a very agressive cam and double strength valve springs and expect to have most of your trips at max RPM under heavy load of racing slicks? However if you feel better using $5 a Quart motor oil I am sure it won't harm the engine. Just remember that Chevrolet recommended using 20 Wt. oil up thru normal temps for most of the US and 30 Wt for areas of extreme temps back when the engine was original. I would use modern SAE 10W30, SAE 5W-30, SM, SL That is what Mr. Goodwrench oil for a modern Chevrolet is.

Well, It is my daily driver from spring till fall, and I take it on the hwy's. The cam is a #264 3/4 grind from Patrick's and the head was done by Clifford's. 1/16" over bore on the 235 HD Motor. It still won't be faster than a Volkswagon bug, but, I just don't feel like lunching another motor. It was not real pleasant pulling that 216. I want this to be the last time that motor has to come out. The 216 radiator should be okay, dont you think?

So flat tappet cams do not need appreciable ZDDP?

In general engines only need a zinc supplemented oil on initial break in. Most assembly lubes have what is needed. Once the parts are coated then additional zinc does little good.

There is still zinc in 10-30 etc SM oils. The amount of zinc has been reduced by about 20 percent, thats all. A special camshaft break-in additive should be used for cam break-in. This was recommended by Chevrolet as far back as 1958. GM sold EOS (engine oil supplement) for this purpose but it has been discintinued.
The racing oils have more zinc but because they are used for racing they lack other additives required for a passenger car engine. A 10-30 oil is still best for mormal service. If I were breaking in a new engine today I would used 5-30 and nothing heaiver than 10-30. Most racing oils like a #40 or #50 which is way too "thick" for the tight fitting parts in a fresh engine.

At one time you could buy hollow push rods for 207, 216, and 235 engines. They were stronger and will flex less and lighter for high RPM use. I have them in my 1934 and 1939.

Would the McGurk tubular pushrods from my 216 be OKAY?

Also, I've noticed on the 235's and 261's there aren't any front and back exhaust bolts, just the smooth studs. Is it a bad Idea to remove those so that one might put in bolts, I am intending to use my headers on it, and I thought it was probably so the stock exhaust can expand and contract without cracking, as I have seen many stock manifolds that are cracked.

Why would you want to remove the alignment studs and replace them with bolts? When you tet one of these ideas, maybe it would be a good idea to go out to the shop and work on something, less important. I for instance often get out the Brasso and get to polishing up some lenses, parking lamp, instrument panels, etc.,etc. or hunt up a manifold or bell housing to detail and paint. I also have my mechanical whatchmacallit that I am always modifying. Last thing I do is look over at the big lever on the whatchamacallit and wonder if.....I should pull it or not. I named it lever "B" and once I understand it's function I am OK! :vcca:

Just kidding, I know that when we are getting more and more anxious we find something else to wonder about!

The push rods for a 235-261 are a different length.
The end studs were only guide pins on that later manifolds. For headers I would remove the guides and install studs.
The 1947 radiator should be sufficient if its in good condition and cooled the 216 OK.

Gene, if you ever listen to Oconomowoc Radio on Saturday Morning, They have an "on air rummage sale" Last fall I found a NOS Radiator for $50. I have been saving it for this moment.

Next, I have a 235 starter off of that 50-51 235. Is that okay to use on the flywheel from the 55' 235, and if so, was that still 6 volts?

Mack, if it weren't for those ideas, where would we be?! For instance, I own a diner, I serve 500 eggs a week. Now, can you imagine, the first dude who saw one fall out of a chickens Rear, and said "Hmm, I should eat that" OR, when you learned about the birds and bees, and you thought..."I AM SUPPOSED TO DO WHAT?!?!"

The starter will fit , etc but MAY be a little low on power. You can see ow it turns over the engine when hot. The best starter is the one from a 1954 Power Glide.

A friend/VCCA member from Lodi has a 1947 Fleetline 4 door, 216 but with dual carbs and exhaust. HE had an over heating problem for years. Would heat up if he drove it at 60 MPH. Had the radiator recored etc. and the problem continued. Then he found a NOS core and has no more heating problem. There is no substitute for a NOS radiator.

Is you resturant on HY 19 ?

Yep, Right on the corner of HWY 89&19 Got a great Napa Right next door. Lots of Bartering! If you ever feel like taking a nice cruise over here I'll buy your Breakfast for all your help. Same for you MrMack! Just avoid Tuesday Mornings at 7am. I host the local Model A restorers club. And let me tell you, they are a different breed. They gave me hell for putting on steel belted radials. But, when I ask them why they all have Delco Alternators on their Model A's they change the subject! They gave the business when I put Mallory Dual Distributer on. I asked why they all have batteries invented by GM Delco (Maintainence Free) They told me Henry had the Idea first!

Also Gene,

I am supposed to say hi to you from James "Skip" Archie here from town. He's got an Original '41 with the paper still on the inside of the doors. He's been swearing for the last 10 years he will start it... Never happens

Is that the black Fleetline 4 door? I haven't seen that car in well over twenty years but often think about it. Was as nice of an original car that you could find.

Thats the one. His wife bought it for him back in the 1960's, for a anniversary present. It is everybit as great now, as it was then. He's also got a '28 Buick 8. And a later Buick. He was a Chevrolet accesories salesman for awhile.