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Remember the "Cadillac 261"?
#1377589 Fri Sep 18 2020 11:15 PM
Joined: Feb 2004
Posts: 21,010
H
Boltergeist
Some time ago, there was a lot of discussion about increasing the stroke length on a 261 engine, using connecting rods for a 292 Chevy six, and a very scarce set of Cadillac pistons to end up with an engine very close to 300 cubic inches that looks like a 235 at first glance. Here's anther sneaky modification that might make a little more sense, and won't involve quite as much work and expense. By some sneaky parts swapping and a little machine work, I believe I can assemble a "216" engine with 231 cubic inches, aluminum pistons, 292 connecting rods with replaceable rod bearings, and eliminate the spray-oiled connecting rods in the process. The engine would be impossible to tell from an original 216 from the outside, since it would use the same engine block, cylinder head, and sheet metal as the original, with the exception of the oil pan. The pan would come from an early-production 235 with the same bolt pattern as a 216, minus all the spray-oiler hardware inside. It would use an oil pump from a 230 or 250 inline six, one that flows nearly twice the volume of a 216 pump. Other modifications would include a Melling camshaft that's slightly hotter than the "Corvette 235" cam, and a leakproof rear crankshaft oil seal. Even with these modifications, the engine would probably cost less than a stock 216 spray-oiler rebuild. I wonder if anybody would be interested in having a "modern" engine that looks like a bone-stock 216 and has 15 more cubic inches and 30-40 extra horsepower or more? It could probably cruise all day at 3500-4K RPM with no problem.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Remember the "Cadillac 261"?
Hotrod Lincoln #1377984 Tue Sep 22 2020 01:26 AM
Joined: Sep 2020
Posts: 4
K
Moderated
Wow. That sounds like a whole lot of work..BUT it will be a conversation starter and big fun to drive. Go for it.


Kenneth R Brown
Re: Remember the "Cadillac 261"?
Hotrod Lincoln #1378049 Tue Sep 22 2020 01:40 PM
Joined: Dec 2017
Posts: 806
D
Shop Shark
Its very clever and I can not wait to see how its put together and how it runs. Way more interesting then a V8 chevy!


Mike
Re: Remember the "Cadillac 261"?
Hotrod Lincoln #1378062 Tue Sep 22 2020 02:53 PM
Joined: Feb 2004
Posts: 21,010
H
Boltergeist
The backbone of the conversion is a 235 crankshaft, with the thrust bearing flanges widened to accommodate the 216 main bearing. That is a simpler conversion that machining the block web thinner to take a 235 main bearing on the #3 position, and it's something I can do on my lathe with a carbide cuter bit and a tool post grinder. The 292 connecting rod is somewhat narrower than the 235 rod, so it gets a spacer washer pinned and silver soldered to both sides of the rod cap to center the rod in the journal. The small end gets a bushing to reduce the diameter to the size of the 235 wrist pin and make the pin full-floating with Teflon thrust plugs to keep the pin centered. The 216 block gets bored 60 over to accept standard bore aluminum 235 pistons. Now, here's the sneaky part- - - - -since the 216 block deck height is shorter than a 235, the pistons would stick out the top of the block. The crankshaft will be destroked from 3 15/16" to 3 7/8", and the tops of the pistons will be machined down just slightly go give a deck clearance of zero, even with the top of the block. The final displacement with standard bore 235 pistons will be 231 cubic inches. I just finished fitting a 250 oil pump that will almost double the flow of a 216 pump. A "216" with 40+ pounds of oil pressure at idle????? Of course it's going to get the leakproof rear main bearing seal while I'm doing the machine work. An early 235 oil pan without the 216 spray-oiler plumbing will replace the original pan, or the spray hardware could just be removed from the original pan and the oil supply port to the pan will be plugged.

I've also got a 258 cubic inch version of the 216 in the works, using NASCAR H-beam connecting rods and a lot of modification to a 235 crankshaft!
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Remember the "Cadillac 261"?
Hotrod Lincoln #1378158 Wed Sep 23 2020 01:17 AM
Joined: Jun 2011
Posts: 3,628
E
Shop Shark
Jerry, have you thought of doing all that to a GMC 302?

Ed


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Re: Remember the "Cadillac 261"?
Hotrod Lincoln #1378164 Wed Sep 23 2020 01:40 AM
Joined: Feb 2004
Posts: 21,010
H
Boltergeist
302's are scarce as hens' teeth, and priced accordingly. People are using 216's for doorstops and boat anchors because they don't know how to work on Babbit rods, and I'm figuring out ways to make "original-looking" engines in 1940's and 50's trucks keep up with traffic without swapping to a 235 or a 261. The idea of modern internal parts in an original-looking package interests me, and I believe if I show up at car shows and swap meets with one of my engines on a trailer with a dyno attached, I could rake in orders for them like leaves in the fall.

Back when GMC 270's and 302's were plentiful, they got hotrodded frequently. but those days are long gone. My father said the 270's gave his flathead Fords a little competiton on the dirt tracks, but they were so torquey the Fords were halfway down the straightaways before the Jimmys quit spinning their wheels coming off the turns. On a long, high banked track, they had a lot better performance because they could stay above the torque peak RPM.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Remember the "Cadillac 261"?
Hotrod Lincoln #1378296 Thu Sep 24 2020 03:30 AM
Joined: Aug 2003
Posts: 100
T
Shop Shark
Jerry,
I'm intrigued! I have a '46 Aerosedan that your 216 mod would be perfect for. What would the final price be, provided I delivered a serviceable 216 to your door?


1953 3600 Pickup
1946 Fleetline Aerosedan
1950 Fleetine Deluxe w/ Powerglide
Re: Remember the "Cadillac 261"?
Hotrod Lincoln #1378311 Thu Sep 24 2020 10:56 AM
Joined: Sep 2001
Posts: 30,441
ace skiver
Tyler - that topic should be discussed in a Private Message.


Tim
1954Advance-Design.com [1954advance-design.com]
1954 3106 Carryall Suburban [stovebolt.com] - part of the family for 49 years
1954 3104 5-window pickup w/Hydra-Matic [1954advance-design.com] - part of the family for 15 years
- If you have to stomp on your foot-pedal starter, either you, or your starter, or your engine, has a problem.
- The 216 and early 235 engines are not "splash oilers" - this is a splash oiler. [chevy.oldcarmanualproject.com]
Re: Remember the "Cadillac 261"?
Hotrod Lincoln #1378313 Thu Sep 24 2020 11:55 AM
Joined: Jun 2011
Posts: 3,628
E
Shop Shark
Well, I'm glad I have a few spare 302's for backup.

Ed


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Re: Remember the "Cadillac 261"?
Hotrod Lincoln #1378318 Thu Sep 24 2020 12:35 PM
Joined: Apr 2005
Posts: 9,010
Grease Monkey, Moderator General Truck Talk & Greasy Spoon
Tyler Watts, Jerry (HRL) answers his PM’s. Buying and selling is not allowed in the garage Forums.


Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne 4dr 230 I-6 one owner (I’m #2)
‘39 Dodge Businessmans Coupe
USAF 1965-69 Weather Observation Tech (got paid to look at the clouds)


"I fought the law and the law won" now I are a retired one!
Support those brave men/women who stand the "Thin Blue Line"! Hug a cop!

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