The Stovebolt Site Forums The Shop Area Engine Shop HRL engine(s)

On Stewart Stewart's engine: making progress- - - - -got the pistons oiled up and the engine is turning. I'll be doing a disassembly and inspection/measurement of all the reusable parts soon. If the camshaft can be reground, do you want a 261/Corvette solid lift lobe put on it? Schneider cams in San Diego can do that.
Jerry

What is the purpose and benefit of installing a 261/Corvette reground cam profile in a 54 235 truck engine?

It has a little more duration and lift than the regular 235 cam, without causing the rough idle and low intake manifold vacuum associated with more radical cam grinds such as the popular "Bulldog" cam that some of the resto-ripoff places sell. Back before the supply of new camshaft cores dried up, the Melling CCS-1 cam, and the Elgin E-323S cam were both very similar to the cam that GM installed in the 261 engine. Those cams are almost impossible to find new, so a reground cam is just about the only way to go. Used lifters can also be resurfaced to prevent damage to a new or reground cam.
Jerry

Jerry, I WAS REALLY kidding. You told me it would be 3 or 4 months to do. Was just giving you a hard time. But you said the engine was turning..... it wasn't turning before? As far as the camshaft; if the price is reasonable, say $400-$500 more than your original guestimate then yes, let's go for it. Also, have you been able to figure out what the deep TTTHHHRRRUUUMMMPPP was, Spun bearing? Thank you, Jerry.

S2

Yes, it was pretty tight to start with- - - -wouldn't make a full turn of the crankshaft. Rusty cylinder walls. That happens when one sits idle, even for a short time. Especially in the coastal area where you live. John's 4 cylinder is MUCH worse- - - -it won't turn at all, and I've been soaking the cylinders with Diesel fuel for a few weeks. Going to use an acetone/ATF mix next. Haven't gotten into the bottom end of yours yet, so I expect to find bearing and/or crankshaft problems.
Jerry

Would there be a measurable gain in performance with this 235 Corvette/261 cam in a 54 235 Thriftmaster truck engine? The Corvette 235 engine was a very different setup, with three 1V Carter YH side draft carburetors on a triple intake manifold and a split exhaust manifold.

If you have performance data to compare, would be interesting to see it.

The 6 cylinder Corvette was mostly hype and advertising, not "performance". Chevy used a 53 Bel Air sedan frame and suspension system, cobbled together a 2-seater fiberglass body, and used their then-new 235 engine with insert rod bearings and a 2 speed Powerglide automatic transmission to market a "sporty" car to people who wanted something to enhance their social standing. They used the camshaft for the 261 cubic inch medium duty truck engine to give the 235 more torque to overcome the power loss caused by the Powerglide trans. The 3 carb intake was mostly eye candy- - - -it gave a little bit of a power gain over the single carb at wide open throttle, but it was horribly expensive, and it was an absolute nightmare to keep in tune.

Yes, there will be a slight improvement in low end torque and a small, but measureable increase in horsepower over the standard 235 camshaft- - - -assuming you can find one to install. Right now, that's about as likely as finding a chicken with lips, unless you get someone to do a regrind. I'm not even slightly interested in playing the numbers game on some theoretical engine built on the drawing board. There are plenty of other people here who like to play those silly games. I like to hide an extra 30+ cubic inches inside these old engines and leave the exterior looking original. A "216" becomes a 258, the 235 goes to 270, and the 261 approaches 300 cubic inches.
Jerry

Jerry - I didn't work on my first triple YH set-up until the mid-1960's.

I never had a dyno at my disposal, nor did I ever do a back-to-back run against a single carb so cannot make a comment on performance gains; but my customers were quite happy with the rebuilt system.

Horribly expensive? YES!

Nightmare to keep in tune? Well, maybe, and maybe not. Why?

When I did my first set in the 1960's, there were only 3 sources for rebuilding kits: (1) Chevrolet dealer (special order, no one wanted to wait), (2) a parts house handling Carter kits (not in my locality), and (3) the only aftermarket carburetor kit company (not to be named) that at that time had a large share of the aftermarket kit business.

So I bought kits from source (3). I quickly determined that the bowl cover gasket was wrong for the Corvette (it was correct for the turbo Corvair YH carbs and the late 1950's marine YH's), and the fuel valves were the large orifice, solid needle. I cut my own bowl cover gaskets (not the easiest gasket I have ever cut), and surfaced the original fuel valves.

As far as initial tuning, this was a time in my life before I was bitten by the "buy American" bug; I tuned hundreds of imports with dual and triple SU carbs, so the three YH's were no challange.

We had no customer complaints about keeping the carbs in tune. We did receive calls from others, many of whom became customers, that were experiencing flooding issues. The use of incorrect fuel valves will do that.

As in the second sentence in this post, I have no real data, but would GUESS that by far the best performance bang-for-the-buck on the 6 cylinder Corvette would be to swap the dogmatic transmission for a real transmission. While I don't believe everything I read on the 'net, several sites suggest that the powerglide will lose about 25 percent at the rear wheels, where a stick about 15 percent.

Jon

Jon, as I'm sure you're aware, doing modifications to the intake and/or exhaust systems of a stovebolt engine is like joining two pieces of heavy duty tow chain with a paper clip. That would include the camshaft. The shape, size, and number of the cylinder head ports, and the position and size of the valves is the real limiting factor. It's like trying to squeeze the traffic on a six lane freeway through a 2 lane tunnel. No matter how many traffic cops are assigned to making the flow improve, the infrastructure just isn't there. Maybe the project I'm working on to install a 12 port dual overhead cam 24 valve cylinder head on a 300 cubic inch "261" engine will help out with that little issue!
LOL!
Jerry

Doing high tech modifications to these glorified tractor engines with 1920s design features is sort of a "lipstick on a pig" approach. No matter how sophisticated the peripherals are, we're still dealing with an antique. That would include pressurized intake systems- - - -turbo or mechanical boost- - - -and fancy headers, dual exhausts, etc. Unless the base engine and/or cylinder head is upgraded in the process, the primary purpose of the whole procedure will be to impress people who don't know any better. The actual gain will be minuscule, but the alleged engine builder will be able to brag about his "accomplishments" on some website without providing any dyno figures to back up his claims. I'd suggest adding a billet crankshaft, forged pistons, H beam connecting rods, and a main bearing girdle to the build, along with a 12 port cylinder head- - - - -then post dyno run figures to back up your claims.

That will impress me.
Jerry

"1920s design features": the chamber shape is very similar to the Mercedes 1955-1963 L4 Mercedes-Benz 190 SL and 230, 250, & 280 SL L6 SOHC engines.
The 261 cam has greater duration but 8° (significantly less) overlap, perhaps to reduce reversion, and increases torque and CCP from very early intake valve closure (39° ABDC).
"billet crankshaft, forged pistons, yatta" means that only the block casting is original.

Doesn't the larger 261 stroker receive most of its increase from the bore size?