The Stovebolt Site Forums The Shop Area Engine Shop are 235 and 261 cams interchangeable?

Hi folks,

I imagine this question has been addressed in these forums, but darned if I can find anything with the search... I figure some knowledgeable members here will know this off the top of their heads:

I have a 1958 261 engine at the machine shop now, being rebuilt to go into a 1950 1 ton (3800). My rebuilder told me I need a new camshaft. I have a few 235s in my shop that I could scavenge cams out of--one's a 54 and one's late 50s.

If a 235 cam won't work, perhaps somebody can tell me where to go shopping for a 261 cam.

Much appreciated!

They are physically interchangeable but the grind is different to match the difference in displacement. The 235 corvette engines used 261 cams for more horsepower.
You shouldn't use a used camshaft anyhow unless you use the same lifters & they stay in the same position.

George

A used cam is about as practical as a recycled piece of toilet paper. Unless you also use the same set of valve lifters from exactly the same camshaft lobe they were running on, the cam will wear out in a matter of a very few miles. The Elgin E-293S cam or the very slightly more radical Melling CCS-1 would be a good choice. Both are usually available on Ebay or from local parts stores like Auto Zone, Advance Auto Parts, or O'Reilly's. The Elgin cam is an exact copy of the solid lifter cam used in the 6 cylinder Corvette and the 261 truck engine. The Melling cam has a little more exhaust valve duration for better cylinder scavenging. Neither one causes low intake manifold vacuum or a choppy idle like some of the "performance" cams sold by the resto-ripoff places. RUN- - - -do not walk away from the cams sold by Clifford, and ALWAYS install a new set of lifters when changing cams.
Jerry

Thank you George and Jerry!

I will be cam shopping tonight.

Those same cams can be used in 216 and spray-oiler 235's by machining the bearing journals down to the smaller diameter used by the earlier engines. I'm in the process of building a spray oiler 235 with the Elgin cam now.
Jerry

New cam cores have been hit or miss as of late. If you are haiinving trouble finidng a new cam, the other alternative is to take your late 50s 235 cam and have it reground to 261 specifications. Any of the cam grinders cam regrind a cam. Just another option.

Both cams work well- - - -use either one. Occam's razor applies here. Don't nitpick things.
Jerry

Warren Foster wdoftexas who has long passed once said "I think you are trying to seperate the fly [censored] from the pepper" when referring to nitpicking.

Bought 261 cam & lifters from local NAPA.

Good point, Greg, as if it would make a difference out in the real world. I'd like to see some dyno figures comparing all those so-called "different" cams instead of all the pontification- - - - -most likely a small change in temperature or humidity would skew the numbers to make any supposed differences a moot point. At least that's what we found when dyno testing round track engines.
Jerry

Are the Melling and Elgin part numbers referenced in this thread…..for use with solid lifters only?

Yes, they're both solid lifter cams. The Elgin cam has the same timing and lift as the 261/Corvette cam, but a slightly different lash specification. The Melling cam has a somewhat longer exhaust lobe duration and a very similar intake lobe profile to the 261 cam. I'll be doing a degree check on the cam I'm installing in my 261 stroker engine, and probably doing a bit of timing tinkering by broaching a couple of extra keyways in the cam gear at slightly different positions than the original slot. I'll also make the timing cover removable without pulling the oil pan, and make the cam gear a snug slip fit, retained by a center bolt instead of a press, so I can tinker with cam timing during dyno runs. Advanced cam- - - -more low end torque- - - - -retarded cam, more top end HP. "There's no free lunch", at least without computer controlled cam timing!
Jerry

Jerry:

I'll be quite interested in your degree-wheel checks. I stared at the CCS-1 and Elgin cam specs till my eyes blurred. I couldn't figure out how theit published specs relate to the factory specs from the manual. Which specs include the clearance ramps? What would be the duration at 0.050"?

Anyhow I used the Crower cam I already have along with its lifters. That cam is at the hairy edge of what's usable for my purposes -- hauling a camper at highway speeds. It's a split-overlap cam, advanced 4 degrees when ground. Duration at 0.050 is 220 degrees while advertised duration is 252 with 0.020 valve lash.

The result is that at 2500 RPM the engine is just barely "up on the cam" and is much happier running at 2800. Sixty MPH is 2500 RPM in overdrive. Before I changed axle gear ratio from 5.13 to 4.57 sixty MPH was 2850. Since I can't go back to the 5.13 (it is worn out) I'm thinking of changing cams, but to what? I want one that pulls at 2500.

I just finished a 4,000 mile road trip with the camper here in the Western US -- Washington State to Southern Arizona and back. Lots of mountains, lots of flat straights, lots of wind. So on-the-road experience is now well established. I'd like to get the fuel consumption down before I head for the Civil War battle grounds in your area. It's 10MPG now.

FWIW, when I changed cams from a mild Howard's grind to the Crower my gas mileage went up 25% with no other changes. My theory is that I was running so far above the torque peak that specific fuel consumption was way up. Now I think I'm 3-400 RPM below the torque peak so fuel economy suffers.

I don't give a concrete water barrier about ".050 lift duration"- - - -it's a cop-out for cam grinders who have lousy quality control or machinists who can't read a dial indicator or a degree wheel. When I degreed the Elgin CCS-1 cam we installed in John's engine, it was dead-on accurate on every lobe we checked. Since I've slept a few hundred times since then, I don't remember specific numbers. Yes, they include the clearance and deceleration ramps in their advertised duration, which, IMHO, is ridiculous. I haven't had an opportunity to degree the Melling cam I've got stashed away, so the jury is still out on that one.

Getting anal-retentive about "original" lobe profiles for cams that haven't been manufactured for decades is counterproductive, and borders on having an obsession with useless minutiae. The Elgin cam is a good one, judging from my own experience, and John's testimony about how well his truck performs compared to his previous engine and the 4.56 gear it had when it was running the 216. He's running a 4.10 behind a direct drive SM-420 in a 3800 pickup. I'm hoping the Melling cam will also provide good results. "Stay tuned" as the oldtime radio announcers used to say!
Jerry

I wish you were a little closer to Tennessee- - - -I've got a complete 5.13 center section in what appears to be excellent condition, and I'd make you a racehorse deal in a swap for that 4.56! Do you ever get on the east side of the Big Muddy Mississippi?
Jerry

Jerry,

Clearly, since I'm running a Crower cam, I dont give a rip about original profiles either. I just want one with a torque peak 300RPM lower than what I've got. Maybe the Melling CCS1 is the ticket. But it's enough work to deal with rusty bolts to get the grill out that I don't want to do it every weekend. Back in the day a buddy or mine did just that to his 55 Bel Air. He cut a neat hole in the grill so the cam would slide through. He had a cam for every occasion. The AD grill won't accommodate such a hole.

I want to get it right the second time. The first it in the engine now and the cam that came with the 261 is marginal at best. I suppose I could have it reground.

Yes, I know. Worked well with the previous gearing giving 2850 @ 60MPH in 4th over. This setup pulls well in 4th direct or 4th under pulling a 6% grade, like, say, Siskyou Summit but at 60 on the flats into a stiff headwind all day across southern Idaho it sucks but it only sucks about 2inches of vacuum if that. Of course, if I run it in 4th direct at 2900 instead of 4th over at 2400 all is well except for the noise and fuel. That leg of my trip got only 7.5MPG. I blame that on the wind... and an attempt to avoid being run over by trucks with Idaho's 80MPH speed limit. As they say, its' complicated.

About 0.047". It is ground with 4 degrees advance already.

It has noticabely more low end torque now with one point higher compression ratio and an extra 20 cu. in. and now I'm working on fuel consumption. I think a shorter intake duration cam would help that. If I lean out the carbs any more I get exhaust valves sticking in their tight guides on a cold morning at sea level.

Quieter valve-train operation would also be a plus. Valve lift is 0.450." Don't need that much lift and that radical a lift rate.

After all is said, the current setup has lots of power to make the next gear but for longevity sake I don't turn it much over 3,000, with 12 speeds I don't have to. I got over 200,000 out of the 235 that the cam came out of. Don't lug it and don't over-speed it that's my motto.

By the way, does anybody know of a source for valve rotators? The ones that came on the 261 I bought were unusable. I couldn't find a listing by that application.

I'm pretty sure small block Chevy V8 valve springs and rotators will work on a Stovebolt. The exhaust valves are identical, so I can't think of a reason the rest of the assembly would cause any problems. The intake valves don't need rotators. I just happen to have a couple of heads on the workbench right now, a 261 head with rotators, and one for a 350 V8. If the incoming severe weather that's predicted for tonight and tomorrow doesn't blow me away, I'll be happy to make some measurements and post the results soon.
Jerry

Stainless steel spring seat washers are available by the thousands, last time I checked with my machine shop jobber.
Jerry

About 5 minutes per washer on the lathe. Start with a 1/8" thick fender washer with a 1 1/2" OD and machine a step 1/16" deep, or just modify the existing lower spring washers. Experienced race engine builders have done similar stuff many times. Any wrench jockey can assemble OEM parts. Small block V8 springs offer a lot more selection where seat loading, lift capacity, and max RPM is concerned.
Jerry

I just bought some rotators off Ebay. GM group 0.309. My parts books says 47-62 all. That should cover it.