The Stovebolt Site Forums The Shop Area Engine Shop is it a 261?

I always thought I had put a 1957 235" in my 49 a few years back. It was rebuilt so I didn't do anything internal. I have since changed the water pump and done tune ups using 235 parts. The water pump impeller goes into a large diameter whole on the front of the block. I have what is called an 848 head on it.
Today a very knowledgable old time hot rod guy came by and looked at the motor and said it was a 261. I was surprised and asked how he could tell. He said the oil filler/breather cap would be half way down the valve cover if it was a 235. Mine is at the front. He mentioned a few other things such as the front motor mount and the bell housing. Incidentally it has the 4 hold down screws and the other things that a 235 has over a 216. Any ideas or comments?

The location of the breather cap is in the same place on later 235s and 261's. My 62 235 is stock and the breather cap is in the front. Check the casting number on the block. It will be a 7 digit # between the starter and the fuel pump, kind of behind and under your mechanical advance. Then match your numbers on www.inliners.org You'll know what you have then.

".. a very knowledgable old time hot rod guy .."

"Any ideas or comments?"

I think the guy might be talking about Chevrolet passenger car 235s? It does not seem prudent to try to identify an engine based on parts (valve cover, motor mounts, bell housing) that are easily swapped around.

Doesn't the 261 have the "Captain" bars casted on the side of the block? When I removed mine from the Burb, that was one of the casting marks that the buyer wanted a pic emailed to him to confirm that it was a 261. He drove from southern CA to pick it up and was elated to have found one so close to him...400 miles..wow.

I think your friend was talking about differences between a 216 and a 235 not a 235 and a 251. 235 and 261 are so similar that the clues are tougher. The captain's bars is a good identifier. I sure wouldn't try to distinguish between those 2 by looking at bolt on items. Kinda like trying to figure out which way a train went by looking at it's tracks.

A great tech article thanks to old chevy trucks
http://www.oldchevytrucks.com/Tips/261_six.htm

261 has large 1/2" NPT holes for the oil filter lines that MUST be used cause that motor is full flow. The 235 is bypass and you can just plug the 1/4" holes and run it without a filter.

A minor correction to the last posting: the 1958-1962 USA Chevrolet truck 261 engines had the 1/2" NPT threaded holes for the full-flow oil filters.

What does "NPT" mean?

NPT=National Pipe Thread

thanks.

It is a Canadian motor/engine (!) so the stampings on the boss near the starter mean nothing to most lists. I have tried before to identify it. did the "848" heads come on the 235 and the 261?

olblu49,
Canadian 261's all came with the 848 head from the factory but never in the U.S. They all had hydraulic lifters , a fiber timing gear , and bypass oiling only. Check the block number in front of the fuel pump against this link to see if you're a winner. I found my Canadian block number on the list. I'll guess 3837012 is the number you'll find if it is a 261. They were also painted a bright green.


http://www.oldchevytrucks.com/cgi/htmlos.exe/003545.11.2762741477700028414?


Curt B.

I don't know about the 261 but my stock head is an 848 and were that way on 235s in the last few years it was produced.

If the Canadian 848 head was factory-installed on the Canadian Pontiac and/or Chevrolet truck 261 engine, was the 848 head factory-drilled for the extra water journal/passages in the 261 block?

In what years was the 848 head available on 235 engines in USA and Canada and on 261 engines in Canada?

Also, the Canadian Chevrolet/GMC 1954 Truck Maintenance (Shop) Manual has a section for the truck 261 engine. It had mechanical lifters, metal timing gears, and bypass oil filter (it looks like the oil filter was optional). As was the case on the 1954 USA Chevrolet truck 261, the Canadian truck 261 engine had a lower compression ratio than the truck 235.

Was the 261 truck engine used all the way to 1962 in Canadian Chevrolet trucks?

Oops, My previous post was referring to the Canadian Pontiac 261 which went from 55-62. 848 heads were factory drilled in the car application but I have never seen a 261 in a truck in Canada. I assume they would have had the mechanical valvetrain and the lower compression head as in the U.S.

An interesting point about the 261: John Gunnel, in his book, Chevrolet Pick-ups 1946-1972, he sez that the 261 was available as an option in C10s and C20s in 1962, also the last year that motor was produced. My 62 owners manual doesn't have anything about the 261. Can anyone confirm this?

My motor/engine is a 1957 vintage. It has hydraulic lifters, the fiber timing gear and the 848 head. The oil filter is a cannister mounted on the intake manifold. I bought it as a rebuilt 235 but I am going out now to check the casting number. I did at one time own a 58 Pontiac Stratochief (Canadian model) with a 261. It was a fast car and seemed to have more power than my truck.
Bill

Checked all the numbers I could find. Nothing near the fuel pump. On the boss in front of the starter is a stamped number 166942. There is no other visible number, cast or stamped on the block. The head has a casting number near the middle of it on the drivers side and it is 3836848.
Thanks.

Bill, they are hard to see but I'll bet they are there. Look at the area where the distributor goes into the block. Just ahead of that and a little bit lower you will find the numbers. The numbers became visible after I did a little scraping and then sprayed with gunk. I could see them best while actually praying the stream on the numbers. Part of the block sticks out a little and kind of gets in the way. It will be 7 digits. The light held a diff angles will help you to see. You may have to move the vacuum line that goes to the mechanical advance out of the way. Good luck.

OK! The number was tight between the starter and the block and it is 3887004. The previous stamped number 166942 was on that flat boss just behind the distributor. Now I should find out what I have - hopefully.
Bill

Bill, 3837004 is a 55-57 235. Are you sure that second 8 isn't a 3?

I was wondering the same thing. I found a 261 casting list and there is a 3837012 which would again cause some confusion if my number is indeed 3837004 thinking mine might be in some sort of sequence. However I am still inclined to think I have a 235 and will check the number again tomorrow in the daylight. Thanks for the help, I'll be back.

My book says the same but doesn't list an engine code for them, just says "N/A",
Scott

Tried to see that number again but it is mostly hidden by the starter. If I ever take the starter off it will be easy to see. So for now I am going to consider it a 235 with the number 3837004 instead of what I thought I read 3887004. Thanks to all.

I pulled my 261 out of a '62 suburban, and it was/is factory original, so I can believe that it was available in trucks too. It came with an oil filter and bypass thermostat, and was in front of a SM420 with a hydraulic clutch.

I am building a 261 right now that has a date code of 1963. I understand they were in some four wheel drives in 63.