The Stovebolt Site Forums The Shop Area The HiPo Shop Cadzilla 261

...anyone have any experience building one of these? For those of you that don't know what that is, it's a 261 block, 292 rods, Cadillac pistons and an offset ground 235 or 261 crank to give it a 4.125 stroke.

Any information would be helpful. I'm trying to round up parts and give it a whirl.

Thanks,
Greg

I built my first stroker engine in 1963, a flathead Ford with a 49 Mercury 4" stroke crankshaft, and I've changed strokes up and down several times since then. Just be sure the engine works on paper before you start whittling on the crankshaft. One of my most successful stroke-change engines was a destroked 305 that ended up at 255 cubic inches. That one would run close to 8K RPM on a small Holley 2-barrel carburetor, about 1,000 RPM faster than the guys running 350 Chevy engines on the same carb. Nobody could figure why I could outwind everybody else down the straightaways, and the tech inspectors were too dumb to figure out what I was doing.
Jerry

Have not built one, but have a couple 261's set back for a future build. I've got some bookmarks of stuff I've read..
http://www.angelfire.com/nv/conv/stovebolt.html

http://webrodder.com/article/stovebolt-stroker-chevy-six-part-1-history-of-the-stovebolt-chev

Good luck on your build..
Mongo

Jerry,

That 255 sounds like a slick little tricky screamer....never thought of that combination. My favorite when running short track, which required a Holley 2bbl was a 377. A 350 crank in a 400 block. Pretty cheap cubic inches with all off the shelf parts and it would run 6,500 rpm's all year long.

Anyway, back to the "Cadzilla 261" the part that sounds a little sketchy to me in the first article Mongo posted is " using the grind of the offset to create a collar for side clearance " huh? really? so the edge of the bearing is riding on the edge of the crank offset to control the side clearance between the rods? I don't like the sound of that. I'd like to hear from somebody that has done it and says it works.

Thanks,
Greg

Look at the picture layout that accompanies the tech tip. The offset grind actually creates enough of a shoulder that the side of the rod is running against the crankshaft- - - -not the bearing. The 292 rod is considerably thinner than the 235, so the undersized area is centered on the wider 235 rod journal, creating two shoulder areas. It's not an ideal situation, but the alternative is welding up the sides of the un-ground area and finish grinding it to create a shoulder all the way around- - - -welds in 12 places on the crankshaft. I would be a little concerned about stress risers and possible bending.

The tiny engine was made by using a 3.100" stroke 262 V8 crankshaft in a standard-bore 305 block. A Holley 7448 350 CFM carb was required by the track rules. Sneaky trick #2 was a .100" angle mill of a set of 58 CC 305 heads to bring the compression ratio up close to 10:1 with flattop pistons. We also installed 1.6" exhaust valves. The only hard part was finding a stiff enough stock-appearing single valve spring to make it to 8K without valve float. The engine wouldn't pass a teardown inspection, but all the visible casting numbers said "305"!
Jerry

It really is a build that says "because I can" as the cylinder head can't really provide enough air for a well built 261 inch engine, much less for an engine with more cubes and more output.

I look at it as a build that says "more cubic inches". It's only going to turn 3,000 rpm tops. You're right, I'm limited to an 848 head. And, on top of that I'm limited to an updraft carb since it's going into a COE. So a longer stroke and more cubic inches is about all I can do. Unless it's not a dependable combination what can it hurt?

Greg

I'm not really sold on the build either. If you want a 261 with more cubic inches, just buy a 292. Way more reliable, alot less machine work involved.

Agree with all, but don't forget the "cool" factor. You'd be one of darn few.

Yup! That's why I drive a shabby '37 with a hopped up Jimmy 302 and am building a Buick nailhead 322 with vintage performance parts, etc. Secretaries drive pacific rim scrubbing bubbles to work with more horsepower than I got but it's the "cool" factor.

I think an inline 6 is pretty cool by itself, regardless of what vintage or era.

I agree with you about a 292. I put one in my 61 Apache K10. I love it. A 292 won't fit in a COE. It's too long, it's too tall and the big gotcha is an updraft intake, don't think there is such a critter for a 292.

and that too !

302 swap might be a good compromise. Its pretty easy to get a little more cubes from a big bore in one of these. Plus you keep the vintage "cool factor".

As 12 port pointed out improvements that exceed breathability have no benefit. Larger valves with 3 angle grinding, mild porting, .060"+ overbore, zero decking, taller cam, and designing/fabricating a 2 barrel intake are gonna give you the best bang for the buck.

Here you guys go

improvements that exceed breathability have no benefit


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That sounds profound but I respectfully disagree. I know the heads are crappy. They are what they are. I suspect ( don't know of course because I haven't done it ) a 235 compared to a 285 with the same 848 head, will have a way different torque curve with the 285 being much more impressive. It just makes sense, more stroke and more cubic inch makes more torque, even with a crappy head.

I'm not really sold on the idea, it just seems like a reasonable option. Just looking for input and I appreciate your thoughts and comments.

Thanks,
Greg

There are two factors involved in performance- - - -RPM and torque. Build in enough low end and midrange torque, aid it's not necessary to have enough breathing room to ventilate an average-sized Kentucky coal mine! Long strokes and plenty of compression combine to allow plenty of performance without astronomical RPM.
Jerry

you'll be just fine your after torque not hi rpms. you don't need port work or big valves and a big cam, save your money. when stroking this what are you going to do to about the distance between the rod and camshaft they get very close
Jay D.

The 292 rod has a much smaller big end than the 235/261. Even with the increased stroke there's not much of a cam clearance issue.
Jerry

I've got a pretty good lead on a 261 or two in western New Mexico. I'm heading over there tomorrow.

I plan on running a stock(ish) 261 cam, a stock updraft carb and an 848 head. The effective RPM range will be lowered by the added stroke and bore ( more cubic inch ) but the torque and cool factor should be sky high under 3,000 rpm"s

...and now I can't find any 80-84 Cadillac 368 pistons. Anybody have a lead or source?

Thanks, Greg

You should be looking for 368 cu.in. Cadillac V-8 pistons (1980-1984) not 268.

Here is the closet i came to it http://m.ebay.com/itm/141013203948?nav=SEARCH

Sorta pricy.

YUP. typo. meant 368. I found the same thing. $720 is a little steep

I just found this the pistons are 47 bucks a piece only sold in sets. Its a little better.

http://www.flatlanderracing.com/trwcast.html

Thanks. I can deal with that...best lead so far.

Greg

Check out the piston for the 5.3 L Chevy Vortec engine. It looks like it might be a pretty close match for the Cadillac, and it's a lot newer engine- - - -just might be more available and less expensive. Not sure about the compression height, but the other numbers look pretty close.
Jerry

OOPS! scratch that idea- - - - -WAAAYY too short on the C H!
Jerry