I have a later, full pressure 235 in my 57 GMC with an “848” head and upon initial startup there is no smoke out of the tailpipe until maybe about a mile down the road, then it smokes like mad for a bit and at a constant 50mph there is minimal smoke, noticeably more upon deceleration and after a few moments of idling it pours smoke!
I have not conducted a compression test yet but thought I would pill the collective wisdom here before digging in!!
Probably loose intake valve guides, but also check the drain holes in the cylinder head. A bad sludge buildup can clog the drains sufficiently to make oil puddle around the valve guides. Valve stem seals don't fix worn out guides! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Not terrible, I’m really thinking the oil burning is a problem in the head, the 261 with an 848 head showed up Saturday night, degreased, stripped and buffed everything yesterday, New valve stem seals and gasket set is supposed to arrive tomorrow. All the exhaust valves have the slightest bit of “wiggle” in this new head but the intake valve “wiggle” while in the guides is barely perceptible
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
Ask HRL Jerry about drilling an 848 head for a 261. Needs coolant flow above and beyond that necessary for a 235.
~~ Jethro 1954 3100 Back to Life In the Dity Gallery 1951 3100 (gone) / 1956 4400 (still in the neighborhood) / 1957 6400 with dump body (retired) / 1959 3100 panel (in the woods junked) / 1978 Custom Deluxe K10 / 1993 S-10 4.3 / 2004 Chevy Crew Cab / 1945 John Deere H / 1952 John Deere B / 1966 John Deere 2510 / 1967 John Deere 1020
Now I’m really curious how much better it will run when #1 & #2 intakes actually open!!
That's an interesting question. I'm guessing it would run a lot better.
So what happens within the cylinder during the intake stoke if the intake valve is stuck closed ( exhaust is already closed ) ? Does the cylinder attempt to pull air/ oil from the crankcase , compress it , and then kick it out into an extremely hot exhaust manifold on the exhaust stroke? Would that explain some of the "oil burning? Hoping someone ( Jerry ? ) would provide an answer. Turn this into a teachable moment for an old guy like me.
Last edited by Dusty53; 05/02/202312:14 PM. Reason: added info
Ron - - Dusty53 1954 Chevy 3604 In the Gallery Forum "You can't dance with the Devil and then wonder why you're still in Hell." "They will forget what you've said, and they will forget what you have done but they will never forget the way you made them feel."
I think you are really on to something with this, all that vacuum has to be satisfied somehow!! Judging on how wet #2 was with oil I think that might be exactly the case!!
Speaking of pulling the head…. As soon as I lifted it off the block I saw the telltale steam vents and thought “oh yay” followed by “oh crap” I immediately set to scraping off grease on the side of the block to reveal the “captains bars”! Yep my 235 is a 261! Another set back while I now await the only 261 head gasket in Canada to arrive from Orillia, Ontario!!!
The head has been completely torn down, valves and seats buffed clean on a brass wire wheel, new valve stem seals installed and reassembled.
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
Those cylinders with valves not opening or in some cases with valves that are not seating will become oil pumps.
"oil pumps" - that is valuable information, thank you for the input.
Ron - - Dusty53 1954 Chevy 3604 In the Gallery Forum "You can't dance with the Devil and then wonder why you're still in Hell." "They will forget what you've said, and they will forget what you have done but they will never forget the way you made them feel."
Compression rings use the pressure of combustion to help seal them against the cylinder walls on engines that are actually burning fuel. Pulling a vacuum against a cylinder with a closed intake valve will definitely draw oil past the rings. If the 848 head was originally installed on a Canadian Pontiac 261, it will have the coolant holes drilled into the head to allow the flow of coolant past the siamese-cast cylinder pairs. There will be a total of six holes. The 261 head gasket is also different than the 235 because of the 3 3/4" bore size. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Jerry , thank you for clarifying the drawing of oil past the rings in the case of a closed intake valve during the intake stroke. Good information to know and add to the knowledge base.
Ron - - Dusty53 1954 Chevy 3604 In the Gallery Forum "You can't dance with the Devil and then wonder why you're still in Hell." "They will forget what you've said, and they will forget what you have done but they will never forget the way you made them feel."
Because of the larger bore size (3 3/4" VS 3 9/16") there is no room for coolant to flow between the three pairs of cylinders which are cast in a figure 8 shape (Siamesed). The same process is used on a Chevy small block 400 V8, with 4 1/8" bores. The coolant holes in the block and the head are there to let coolant flow up the sides of the cylinders instead of flowing between them. An 848 head for a 235 will bolt onto a 261 block, but unless the extra holes are drilled into the head, hot spots will develop where the siamesed cylinders meet. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Well, after 2hrs of reassembly the 261 is alive and not appearing to burn oil!!! Downside is the starter has now packed it in!! Maybe too much of a workout conducting the compression test??
Glad to hear about a possible cure on that oil burnin ! Anxious to hear the results after a test drive. That “oil pump” situation is fascinating, if that’s what was causing it! Hope you can get a new starter on there easily. C
~Charley 1954 Chevy 3100 with 235 “Bud” Follow along in the DITY 1963 Chevy half ton stepside short box 230 1954 GMC 3 ton 302 And several more Chevy camper and work trucks 1979 1987 1996
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
