The Stovebolt Site Forums The Shop Area Engine Shop shot 235 now trying 261

hi chaps, inspiration or drugs required?!

after stripping and taking my 235 to the engine shop they confirm that my cylinders need a +40 rebor, and loads of $$$$..this is not what i need, ive my panel truck body off,,,and have painted and rebuilt the frame over the last 5 months...im almost ready after this weekend of piping the brakes up to put it back together.
to say the least..im exhausted!.

ive have a 261 sitting around waiting for a day like this. which i purchased last year from a chap who only ran it for 20 miles, home...ran out of oil...and put a v8 in??!!

im trying to get it road ready,for the summer...as just need some good times in it!

what ive found is the engine had the wrong head on (235)..and no-one drilled for the steam hols...and engine looks a little cooked..they also blocked down draft breather to the sump.(oil crusty and looks a little hot)

the head was 3835913
im going to use the head of my 1956, 235 which is a 3836848 ?and will drill the steam hols

the 261 block casting 3837012 and by distibutor f3IIK

what im unsure of apart from everything..!!!.is;-

will my old 235 clutch and flywheel fit? the bolt hols line up ok, but the timing dot on the flywheel is 1" out?

both fyhweel's are unknown as my old engine 1956 was a bit and pieces job but ive done 10,000miles on it ok,

my flywheel has stamped GMC - 838764-777, and by the timing dot ;- "UIC 5"

the flywheel from the 261 has GM2 3704832 and by the timing dot;-" 2 10C"


what we think?!

Forget about the timing marks. The 261 and 235 engines had a variety of different timing marks. Use whatever timing mark you have for setting initial timing. Set the timing on a running, warmed-up engine using a vacuum gauge.

Use whatever flywheel matches your starter (6v vs 12v).

Use whatever clutch assembly that fits the year of your clutch housing (clutch plate, pressure plate, throughout beating). Put in a new pilot bushing (check that bushing out on your transmission's pilot shaft before installing it)

Maybe someone will post a link to an old discussion of how to drill the coolant holes in the 235 head? There is a recommended drill angle.

hi Tim thanks for all that. ive looked for the drilling the head found alot of info on here..going to get the rest of the motor in shape first then take on the head in a week or so

Daniel-Rose,

I'll search for the drilling information tonight.

It might have been posted over on the oldGMCtrucks.com discussion board.

Just think of everything at back of your 235 as a unit, bellhousing, flywheel, starter, clutch etc, if in good shape can all be left as is when slipping in the new motor. I went with a 261 in my 46 pickup, still using ALL the '46 components, even the foot starter.

Use your 261 head gasket as a guide to drill those steam holes, easy deal. Also with the 261, my 1961 year motor has one 'bastard' head bolt that is drilled to allow oil to top for rockers, it's center bolt on distributor side, don't lose this bolt. Not all years of 261 have this drilled bolt, just be sure you have oil going to top end.
Best of luck
Jim

Hi Jim, dont think i have this bolt? any way i can check?

i did run the engine quickly before getting it into a load of pieces...i also around six months ago complete a compression test on the 261, they where all in the 100's..but didn't set the tappets, (cant find the exact results) thats was good enough for me.

the plan was to put my old 235 in and work on the 261 ..when the trucks on the road....not possible now...

ive spent out on everything getting the frame and running gear sorted! its all new / reworked..only thing i couldnt do was straighten the springs...

http://i995.photobucket.com/albums/af75/hootschc/truckframe_zpsc9ae3c66.jpg

What I would do is pull the distributor and with a long screwdriver turn the oil pump and make sure you have oil coming out of the rocker arms. This 'drilled bolt' is the center one on distributor side as I mentioned, you could pull it out to see if it has this small hole in the end, hole exits up on the side above the thread. Hole is under 1/8 inch. Again not sure what year your 261 is, different year motors accomplished this oil route not using the drilled bolt.

Very nice job on the chassis. Post more pics of the truck.
Jim

thanks jim, just cleaned all the bolts and no hole..sadly ive stripped the engine down to the block with just crank/pistons/cam in..ready to do all the seals and paint it up a little.

got to order a load of stuff for it..
here is what the old girl looks like;-

http://i995.photobucket.com/albums/af75/hootschc/261961_2028079136069_5122192_n_zps010229da.jpg

http://i995.photobucket.com/albums/af75/hootschc/208703_10150507433470231_1929100_n_zps381099e0.jpg

http://i995.photobucket.com/albums/af75/hootschc/148262_1672202559377_7771533_n_zps7beeddc9.jpg

http://i995.photobucket.com/albums/af75/hootschc/259881_2028066815761_6747438_n_zpsdce76e76.jpg

tim has a picture of my bolt with the hole in it. maybe he can post it. my hole is on the shoulder just under the head.

Mike,

Pre '68 Dave thinks your bolt is an oddity (no offense - I hope I am using the correct word): here is an entry on that bolt on Dave's blog site

The drilled head bolt is only needed when you are using 1958 or earlier rockers on a 1959-62 engine.

As per Pre '68 Dave, would stand to reason from what i've seen. BTW, I do have one of those bolts.

none taken



the one in my engine or the one in my neck

You'll need to keep the ones on your neck, for a quick and easy energy boost.

Here's a discussion regarding steam hole angle/placement.

Daniel, sure is nice to have a 261 just sitting around. I put a 261 in my panel, it also has the 848 head on it. I've had no issues at all; my bellhousing/flywheel all fit, my waterpump/fan fit, it runs at 180 degrees all the time, 3 years now.

Thank you all very much for your input, sadly I've got to go to work for a few days, so will be back on the engine next week, as weekend I will be piping the brakes up!