The Stovebolt Site Forums The Shop Area Engine Shop hotter cam in 235

This is where I'm at with my 235 in an AD truck. Rebuilt short block, 848 head with solids.Holley 2 barrel carb fron Langdon's stovebolt, Fenton headers, and Mallory electric distributor. I'm wondering how much I would gain with a 3/4 cam from Patrick's Antique auto parts. It runs well now, just want to get all I can and a cam isn"t a lot of money $250 with new lifters from Patrick's. Opinions? Warnings?Better ideas?

A cam is a good idea if it is not over done which quite often is the case. The popular one for this engine is the 261 cam. In fact that was what GM did when they came out with the 6 cyl. Corvette. I would check with Patricks & see if there cam is similar to this.

The 235 in Corvettes was available from 1953 into 1955. The 261-style cam was used in 235 Corvettes from mid-1954 until they ran out of 235s for Corvettes (sometime in 1955).

I'll be putting one of those Corvette cams into my 1954 truck 235 when I rebuild it (and, it will get an "848" head).

I just built a 235 with an 848 head, langdons hei, and Patrick's "hotter" cam. The plan was to end up with the two barrel conversion setup with headers in the future. Right now I'm saving up for the intake and exhaust so I'm running the stock stuff, rochester B, etc. It runs okay now but the carb is really holding the setup back. When I called langdons to order the hei he suggested that the dual two barrel setup would "really make the combo sing". I have no idea of how that translates to horsepower numbers, others can comment, but I hope to feel it in the seat of my pants.

Keep in mind if you like a smooth running 235 the hotter cam from Patricks isn't for you, it's a bit on the lumpy side. I know I haven't answered your question but I guess the point is that I'm on the same track and I feel it's the right one for where I want the look under the hood, the sound out the back, and the feel on the road to be.

The Corvette and 261 truck cam has less duration than the stock 235 Powerglide cam. Quoting Frank McGurk: “This cam has proven to be unsatisfactory for modification work”.

Regardless of what buzzword is used (3/4-race, etc.) the bottom line is that a street-driven engine doesn't work well with a cam with more than about 270 degrees of lobe duration, intake or exhaust. Stovebolt engines don't play well with high lift because of the close clearance between the intake valve and the top of the piston. Flycutting the piston for valve relief reduces compression, and the combustion chamber shape limits the options for making a domed piston.

Because super long-duration cams MUST have increased compression to work right, the stovebolt's combination of oddball valve geometry and combustion chamber shape makes it difficult to benefit from a radical cam.
Jerry

According to Patrick's catalog, there are three "3/4" cams available. Here's the numbers for comparison: (I'll just post the I and E duration numbers and the lift, the catalog has more info as to when the valves begin to open or close)

Stock 261/Corvette cam: I = 244, E = 244, lift .414
Patrick's "3/4 mild": I = 245, E = 256, lift .425
Patrick's "3/4": I = 252, E = 264, lift .436
Patrick's "3/4 rumpy": I = 277, E = 270, lift .436

You might want to give Patrick a call and ask his input (I know, I know, he probably wants to sell you a cam) but I've found him to be a straight-up guy and he does have a ton of experience with 235's.

I have the Patricks 3/4 std w/252I / 264E and it runs OK but is a little rough and not as smooth as I would like. Also have the Offy 2x2 intake w/ Holley Webers and I would not do that again.

235 or 261?

What was the problem with the Holley-Webers?

Wow, lot's of information. Right now, with the Holley weber 2 barrel from Langdon and a stock cam, it runs very smooth, I guess I need to talk to Patrick's, but it sounds like the jury is out on positive results with a longer duration cam on the 235. Maybe I should just be satisfied with the factory setup in this case?

With a good 5-speed OD transmission and the right rear end gear, a slightly over-stock 235 will have as good or better performance over a wider torque band than a peaky cammed-up engine with a narrow power range. That's what a lot of the Diesel engines have going for them- - - -plenty of torque and enough gears to stay in that area over a wide range of road speeds.
Jerry

It's going to be faster with a mild cam, but too hot is a common mistake and makes driving in traffic (especially when cold) miserable.
That "kewl" idle quality is not power, it's LACK OF POWER. If you have a stock Powerglide be very careful.

The 235 and inline 6's in general seem to have a wide torque range, lugs down very well. The worst big diesel engines were the Detroit diesel V8"s, rev fast but no low end guts. So I think the hot cam would take away one of the best things a 235 has to offer. About the 261 cam tho, wonder if it would be a slight improvement without sacrificing the low end.

My complaint on the Holley Webers is that two carbs may be too much fuel and the linkage is always requiring attention. I don't like engines that need a lot of looking after. I want to check the oil and drive it with the power I require. It would have done as well or better with one carb. The H-W's are good carbs however and parts are not an issue. Just one too many.

I ended up with an RV style cam which I have yet to try, I just got it in the engine last night, maybe next weekend I can have it actually in the truck and running. I have the specs some where, but it should run well at least according to the numbers...Yeah I'm thinking the clifford intake with a small holley or their weber setup would be best, but I have so much time and money in this mess I am going to at least try it.

how did your rv cam work out

Carburetors, too many or too big = too much AIR, not fuel.
Any dual carb app should not need any linkage geo or adjustments: they idle, open, and reach WOT simultaneously.

Detroit Diesel is not a good comparison as they were 2 cycle engines.

235 motors are susceptible to all the same kinds of performance enhancing work that other motors are, within the limits of the design. Can you put big giant cams in them? Sure you can, I have, but they react just like any other motor with a big giant cam, the power band goes higher, idle quality goes out the door, all kinds of stuff. Will they make the motor breath like a wind tunnel, nope, the design restricts the breathing and there is no real work around for that. Can you go too far, yep, I have and learned my lesson. That being said, there are more then enough enhancements you can make to a 235, big and little, to suit your needs from a stock motor to wild (relatively speaking, lol).

Mild performance cams in the range of 264 degrees with lifts in the .450 to .480 range have been sold for years by most of the old line cam companies. Very good idle, improvement in breathing, better performance. I would have to dig out my vintage Clifford catalogues but I am nearly certain that Jack Clifford sold his 264 hydraulic cams as a nice entry level cam for an essentially stock motor (he may have even referred to it as an RV cam). Cams in the 270 degree to 280 degree are more testy for a street car with rougher idle and increased power bands (read higher rpms to start making power). At the moment, one of the motors I have is pretty modified and I like a rough idle so I run a cam that is 280 degrees and 492 lift on the street. Ran that motor all over Bowling Green Kentucky a couple of weeks ago, ran perfect, sounded great, no over heating, idles just fine. Did it idle like a stock motor, well, no it did not, lol, but its what I want for right now. Some day I may very well tire of all that and go back to a stock motor.

As for using the 261 truck cam, sometimes referred to as the corvette cam, I have never thought that that cam was a very good performer. The specifications are only slightly more performance oriented then a stock cam, and I mean only slightly. But some really like them and swear by them. Good idle, little tiny performance improvement, but I think there are better grinds on the market that will run way better then that cam and idle just as well. If you are not sure, call the cam manufacturer and see what they advise. I like Schneider cams because they treat me well every time I need a good cam, but there are other companies out there as well.

Dual carbs and triple carbs, I have run triples, they can be a big pain to get them to run right, especially on the street. Not impossible but they can be a challenge. When I have run them, I usually went with the small 216 version of the Carter YF carb. Nice simple carb but still very difficult to get them to idle well or run clean. I prefer dual carbs, and I have had very good luck with them over the years. For a stock 235, or a slightly modified motor, I have had the best luck using a pair of Holley Weber 5200 1974 Ford Pinto carbs. Nice progressive two bbls with small primaries and progressive secondary's. They sometimes require a little tinkering here and there, and you have to sort out a little linkage, but in general, you can bolt them on and they will run pretty good right out of the box.

On the other side of the coin, if you don't want to tinker a bit, and you want the most reliability you can get, then modifying a motor is probably not what you want to do and so a well built stock style motor will be the right ticket. There are no real absolutes here so there are no right or wrong rules, lots of alternatives, except replacing you 6 motor with a V8, which is blasphemy, lol.

A camshaft is one link of a chain of components that starts at the air cleaner and ends up at the tailpipe. Simply tinkering with the cam doesn't help unless all the other stuff is improved, and all the components are compatible with each other. Putting one bigger link in the middle of your chain doesn't improve its overall strength or usefulness. A stovebolt's weak link is the design of the ports in the head and the convoluted path the intake and exhaust has to take to get the mixture in and the exhaust out. It's easy to over-cam and/or over-carburete these engines and end up with less overall performance while getting a more or less imaginary improvement in one specific RPM range. That's not a good trade-off for most street engines.
Jerry

The 261 cam was used in many (most? all?) Corvette 235s.

If you want to brag about a having a higher-lift/modified-cam in your 235, use a 261 cam; and, you can then say that have a higher lift Corvette cam in your engine.

You will not be moving into the arena described by Jerry; you will not:
over-cam & over-carburate
and end up with less overall performance
while getting a more or less imaginary improvement in one specific RPM range

You'll get a little better performance and, you will either get eye-rolls, or some people might say "wow" or "what".

When we assembled John's 261 last fall, we installed and degree-checked a "261/Corvette" cam made by Elgin Industries. It's their part number E-293S. The "advertised duration" is 290 degrees, which would indicate it's a fairly radical racing cam. Actually, the duration of the valve opening is around 260 degrees, making it equivalent to an "RV cam" which increases low to midrange torque and gives a slight, but noticeable improvement in cruise power without adversely affecting idle smoothness or manifold vacuum. Their "290 degree" specification includes the clearance ramps on both ends of the cam lobe, when the valve isn't actually open. The only difference from the OEM "Corvette" cam I can see when checking the cam with a degree wheel and a dial indicator is a slightly different valve lash adjustment.

John can give you a "seat of the pants" evaluation of the difference in performance he has seen, as we didn't have a dyno handy to document any "before and after" power measurements.
Jerry

IMO, the RV style cams are worthless. The ones I have been familiar with resulted in less power and reduced mileage.

When I built my 235, I used the 848 head with a mild port job that has now been milled twice to get flat. Got one of Patrick's 252/264 grinds Checked the valve to piston clearance with clay. It was close, but I have forgotten the number. Left the points distributor in along with stock manifolds and Rochester 1 bbl. Eventually I put 4.10 gears in the old gal, later a Pertronix ignition. She has a rumble known only to those with a good ear. Idles at 500 rpm. Will haul 2 yards of soil down the interstate, in the summer, at 55-60 mph without overheating or straining. And she will turn about 5,000 rpm, with a top speed of over 100 mph.

At the opposite end of the spectrum, my friend has built a 1/2 ton with a 261 that is about 300 hp. Professionally ported head, an old full race cam, Fenton headers, Offy dual carb intake, dual Holley-Webers, Uni-Lite distributor. Idle speed is about 1,000 rpm. Tranny is a Saginaw 4 speed. He once lit her up, and was soon over 6,000 rpm in 4th gear when he shut her down. His only complaint is not enough carb, looking at going with dual Rochester 2G setup, which we will need to do some engineering to make it work.

You don't have to have all of the add-ons to have a good running truck. They do have their place, but need to be balanced.

I grew up with guys who pulled the 261 out of the farm truck, put in a 3/4 or full race cam, hand sanded the ports in the heads, and opened up the B model carb to put in a car that would beat the newer cars. We learned how to make power on a shoestring budget.

hi jerry its dj aka dave. i was wondering what your opinion would be on my 261 with the corvette manifolds and carbs, using a cam with 4 degrees advance built in and 210/218 dur @ 50 cam lift at 290 and max lift at 435 c/l .006" / .018"

Advancing a cam increases low end torque. We used to do that on the 1/4 mile dirt track cars to help the hole shot off the turns. Stovebolts have plenty of grunt, even without the cam being advanced. I'd retard the cam a few degrees to help the top end HP if I moved it at all.
Jerry

A 261 @ 100% VE, 6,000 RPM needs about 498 CFM @ 1.5" Hg. The 1978-* (largest of 3) DGV is about 332 CFM per pair, so more carb will help.
What 2 X 2 manifold is he using - the original (obs) Clifford with L & R carbs? Or adapters on a 2 X 1 manifold?

3 carter yh side drafts from a 1953 corvette

Dave you have a very important Private Message from the Stovebolt Staff.

You've got an even more important one from me! LOL!
Jerry

I am building a 261 (1958) eng .060 over ,848 head. I will polish the ports a bit, 5speed S-10 trans 373 posi. I am wondering if the CCS-5 Melling hydrolic cam is the same as the 53-54 vette cam in specifications. The CCS-5 lists 185 intake and exhaust. I want good milage and torque low and mid range . What do you think . I need lots of info like advancing valve timing or retardingvalve timing. I have dual 2 barrel webers and headers as well. Thanks Dwight