Okay, so after waiting and watching for a long while I have acquired a set of 1954 Corvette Intake, carbs and an exhaust manifold. This will be going into my 1958 3200 Apache. Now I am trying to decide what Camshaft to go with the combo. From my research on here, and the rest of the net, the cam used in 1954-55 was not so great according to McGurk. What recommendation would y'all have for a camshaft that will be having this set up? I'm looking to have a happy medium of torque and hp, with a good idle. So really a good all around Cam. Thoughts and suggestions please? Thank you!
Have you done a trial fit of the assembly yet? I seem to remember there are some serious interference problems with the steering column and/or the shift linkage when that manifold setup is installed on a pickup. When you start trying to rebuild those carbs, the parts cost will give your checkbook a coronary, too! 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!
Presumably you are referring to the 1958 235 that came with your 3200?
"I'm looking to have a happy medium of torque and hp, with a good idle."
Use a 261 cam (the later 235 Corvettes used it).
Yes, I forgot to specify, the block and head are the original 1958 235, bored 0.40 over on this rebuild.
I know the original Corvette's used a 261 cam, I was curious if anyone had ideas of one that's a better choice? I suppose McGurk was building more for racing and that means looking for peak HP?
Originally Posted by Hotrod Lincoln
Have you done a trial fit of the assembly yet? I seem to remember there are some serious interference problems with the steering column and/or the shift linkage when that manifold setup is installed on a pickup. When you start trying to rebuild those carbs, the parts cost will give your checkbook a coronary, too! Jerry
I have not been able to do a trial fit since the motor has been out for a while. I have been scouring the internets for as many pics and info on this exact issue. Found that people have put this in AD's, only one I can see anyways. On that issue it does fit with a little modification to the steering column and shift linkage. From what I can see in the photos, the steering column is set further back into the firewall on the TaskForce series. We shall see!
And I knew it wouldn't be cheap to get these carbs, intake and exhaust, so of course the carbs wouldn't be real cheap to rebuild either. But I have been wanting this setup for a long while, so it's time to chase after it! I plan to rebuild them myself with good kits to try and keep some of the cost down.
When you get around to buying repair kits, be careful. There are four different bowl cover gaskets used on the YH Carters. Both of the 2 in the aftermarket kit available at the FLAPS are incorrect for the 2066s Corvette carbs. Also, fuel valves SHOULD be the spring-loaded variety. The solid type will run the engine in the shop, but will leak when driving.
Main jets are the same type as genuine Carter AFB, so the 10-201 Carter strip kit has a good selection of different size jets. Since you have 3 carbs, and there are only 2 primary jets in the AFB, you will require 1 1/2 kits (or buy individual jets).
Jon.
Good carburetion is fuelish hot air The most expensive carburetor is the wrong one you attempt to modify. If you truly believe "one size fits all," try walking a mile in your spouse's shoes! The Carburetor Shop
As Tim stated, the Corvette 235's used a stock 261 cam. Another option that you might want to look at is a cam referred to as a Bulldog or a .254./.264. It is made by Delta and sold by a few vendors including Tom Langdon.
I'll be installing a new 261 cam this weekend, and I'm planning on doing a timing and lift check on it in the process. Some of the numbers the cam grinder has provided make it look like it might be a little more radical of a grind than some folks think. I'll know for sure in a few days. 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!
IMHO the 261 cam is too quiet, but it does offer an advantage: the likelihood of extensive jetting mods is much reduced (compared to a hotter cam). More overlap and later intake closing changes the vacuum characteristics of the engine, which affects low speed mixture quickly.
The internal passages in the intake manifold is a terrible "S" curve (Brits call this a "swan neck"), done for space considerations. I would be temped to blend and radius every shape change or interruption I could reach, but there's no way to insure doing all three the same.
I would definitely port the interior of the exhaust manifolds, beginning with matching the flange openings to a new exhaust gasket.
The 261/Corvette cam is ground for solid lifters. Somebody else might be able to tell us if there's a performance ground cam with hydraulics for stovebolt engines, but I've never heard of one. 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!
Maybe a Canadian member has specs for the hydraulic cam used on 261-equipped Canadian Pontiacs?
I am not recommending changing/keeping the "modified"-lift mechanical-lifter cam that was used on USA truck 261s (and many 235 Corvettes).
My original cam 1960 261 (bored 0.060, resulting in around 270 ci displacement) has plenty of "oomph" (using a GMC 302 2-barrel carburetor with adjustable main jets).
Running a cam a few degrees advanced from its normal timing increases low end torque. We used to use an offset Woodruff key or an eccentric dowel pin bushing on the small block Chevy V8 round track engines to advance the cam 3 or 4 degrees and get a better hole shot off the turns. Since the stovebolt intake and exhaust port shape pretty effectively chokes off high speed gas flow, I wonder if advancing a 261 cam a few degrees would give a noticeable improvement in the torque department?
When and/or if I get my dyno back in operation, I might try experimenting a little with cam positioning. 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!
Running a cam a few degrees advanced from its normal timing increases low end torque. We used to use an offset Woodruff key or an eccentric dowel pin bushing on the small block Chevy V8 round track engines to advance the cam 3 or 4 degrees and get a better hole shot off the turns. Since the stovebolt intake and exhaust port shape pretty effectively chokes off high speed gas flow, I wonder if advancing a 261 cam a few degrees would give a noticeable improvement in the torque department?
When and/or if I get my dyno back in operation, I might try experimenting a little with cam positioning. Jerry
I have always been intrigued by that cam advancement mod since I first read about it in the early '80s in Car Craft magazine. I don't understand what is going on with it however. I am guessing that like most modifications, there is no such thing as free lunch. Makes me wonder when the engineers will find a way to create an engine which has a variable cam advancement feature, allowing for economy, or higher performance when needed. Carl
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
when the engineers will find a way About 30 years ago.
Variable cam timing was probably squelched about 28 years ago by the bean counters for being too complicated and expensive.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
The 4.6 Triton (Romeo engine) has VVT in my 98 F150. Same for the 2AZ-FE I4 my the Mrs's 2006 Toyota. Both utilize mechanical and hydraulic pressure to vary the cam(s) valve timing.
OTOH: many systems use rocker arms to achieve the alternate cam events, and getting rid of them was always an advantage to OHC - less reciprocating valve train mass.
Back on topic- - - - -sort of! We degreed the Elgin brand cam we installed in John's 261 over the weekend, and it was a real education. The "advertised" duration of 290 degrees had me thinking somebody had mislabeled a full race cam as a stock 261, but they're playing games with the cam lobe ramps and counting the degrees the cam is turning to take up the valve lash as part of the total duration. That adds close to 20 degrees to the advertised duration, turning a cam with about 252/260 degree intake/exhaust lobes into a "290". From the specifications I've been able to find on the original 261 cam, the tech guy's claim at Elgin appears to be correct- - - - -they patterned the master cam for their grinding machine directly from a "new old stock" GM 261 cam.
The quality of the Elgin cam appears to be excellent, so if anyone is in the market for one, they offer a good alternative to the terribly expensive cams the resto-ripoff guys are offering! Good to know! 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!
GM Shop Manuals do show any 261 cam specs that you refer to (they do not show any cam specs)? Do you know if that info is on-line (maybe even 235/261 specs side-by-side)?
From some of my last research it looks like the same cam was used in the 235 and 261 from approx 1956 forward. Can anyone else collaborate this? Even my Shop manual for my 1958 doesn't show different cam specs, but just one for the 235 and 261.
The 235 and the 261 had different cams. I can't find the specs, but attached a cut and paste from the 1960 shop manual showing that the two engines and different valve lash specs.
Do the notes below that chart specify to run an intake clearance of .008, if 261 will be used for "severe duty"? I seem to remember reading something like that somewhere...
My Delta cam specifies a .008 intake clearance, which I assume has to do with the lobe ramp design- but am not sure. It definitely makes the valve train a little noisier.
McGurk was running .015 for intake and .016 for exhaust lash in that Soup That Chevy article.
Last edited by Norcal Dave; 11/01/20172:11 PM.
~ Dave 1950 Chevrolet 3600 3/4-ton with 261 engine & T5 Transmission
Different valve lash specs could be related to the type of work done by the engine? Big trucks might have worked at higher RPMs, had higher thermostat temperatures, and might have needed wider valve lash settings?
The 235 and the 261 had different cams. I can't find the specs, but attached a cut and paste from the 1960 shop manual showing that the two engines and different valve lash specs.
Matt
In late 1955 (Task Force) trucks the 235 cam bearings were changed to match the 261 cam bearings. I bet the "261" cam was used in all 235/261 engines sometime in 1956, as ApacheFiend" suggested.
The 1957 Chevrolet Truck Shop Manual explicitly states that the same cam is used in the 235 & 261.
Different intake&exhaust valve lash settings were used on 235 and 261 engines that used the same cam.
My 1958 Shop Manual does not make a distinction between camshaft specs for the 235 and 261. The whole rebuild section treats them as the same. Going back to the idea of the Corvette Blue Flame 235, which started in 1953, I concur that originally the 235 and 261 had different cams. I would appear though, in 1956 or later, that Chevrolet engineers said, "Hey, lets use the same cam in all the 235's and 261's cause it creates better numbers!" That is what I am seeing.
235 261 Camshafts from Chevrolet Master Parts book:
3836490 1941-1953 235 S/T
3836485 1950-1953 P.G.
3836484 1953-1955 Corvette 1954-1955 Utility 261 S/T 1956-1957 Series 3-4 S/T 1958 Series 3-4 (except D.D.)
3836482 1954-1955 All 6 cylinder (except P.G.) 1958 D.D. (2nd design) 1959 Series 3-4 1960-1962 Series 10-40 1960-1961 Fleetmaster except P.G.
3836483 1954-1955 passenger with P.G. 1956-1958 passenger
Jon.
Good carburetion is fuelish hot air The most expensive carburetor is the wrong one you attempt to modify. If you truly believe "one size fits all," try walking a mile in your spouse's shoes! The Carburetor Shop
