The Stovebolt Site Forums The Shop Area Engine Shop Custom Camshaft for exhaust port compensation?

Greetings!

Does anyone have any leads on special grind sources, or regrinds? I think that a little more overlap and lift on the exhaust lobes for cylinders 2 thru 5 would compensate for the Siamesed ports they share, the only camshaft options I can source cut all the metrics equally per cylinder.

Cost is a non-prohibitive issue with this topic.
Anyone?

How many stovebolt engines have you built so far, stock or otherwise?
Jerry

If I were including what's on the drawing board, 6. If no then 5. 2 were babbit-pounder 216's which didn't need a re-pour in the connecting rods, 1 was a mid forties 216 that still had dippers or slingers for the oiling and the most recent were 235 hydraulic lifter powerglide blocks, - non stock. Whats on the drawing board might be a 262. Or maybe not. I'm trying to source one. I also fool with the small Buick Inline 8 Fireball 248's and the MEL Y-block 368 from 56, 57,&58...and the Small Block Chevrolet.

OK, so you're not a novice with a pipe dream, which is what it sounds like when you talk about MSD ignition, fuel injection, and roller cams in 60-year-old engines that were designed to run under 3,000 RPM and rely on low-speed torque to move the vehicles around. Trying to reinvent the wheel on these old engines is like pounding sand down a rathole, but it's your sand, and apparently you have an unlimited supply of it. Good luck!
Jerry

Jerry

What I'm asking for is a collective conversation on the engines, experiences and so forth. Maybe you fail to realize that not everyone in the world has to think like you, or is entitled to your opinion,etc... I'd be willing to bet your 'Hot rod Lincoln' on that. If we did, then there would be no reason to live, because we would all have your opinion, which is the same opinion every old man had who told you how your ideas were stupid and crushed your tiny, adolescent soul.

Also, read: I would rather argue with an Idiot and be taken down to your level because I know something you don't, It's nobler to remain silent and be thought a fool, than to speak up, and remove all doubt. MSD ignition only works until 3000 RPM, after that just one spark. Add that to your lack of understanding about just what makes torque in an over square engine and, obviously, you would think that reducing internal friction would have nothing to do with reciprocating and or rotating mass.

Also, the 1953 and 1954 corvette was built around the same 60 year old engine which used side draft carburetors and special balancing to smooth out vibrations while accelerating.

And, finally, No novice here, plus I still have plenty of sand and life left, unlike you, perhaps? Maybe you should trade your Hot rod Lincoln for an annuity?

Or maybe you are just Jealous of Clifford racing's history and heritage - Might I suggest a beach boys song to sweat while creating a new handle, because old man you're going to drive ME to drinkin' if you still keep claiming that HOT ROD LINCOLN. Or responding to my posts with your written excrement.

Take your time thinking up your response, Free advise...

OK, kid, go ahead and ignore 50+ years of experience building successful racing engines on three continents, because you don't like what you're hearing. As I said, good luck!
Jerry

More caffeine anyone ?

Now boy's, taint really my place to speak up, but remember this is the 'Stovebolt forum' and not one of those ill mannered hot rod forums.

Might I suggest the Inliners forum which deals more with modified engines: http://www.inliners.org/
Denny Graham
Sandwich, IL

You might try Bullit Cams, they do custom grind work for V8's, they might be able to help with the inline as well. I think Lunati Cams also does custom work. Changing the cam on just a few cylinders might be pretty tough, but who knows, it might not be that big of a deal. Our high powered engine analizer won't let it happen so I can't run any engine combinations for you, it will only let you change the whole cam.

Whats the idea behind this? get more exhaust out or use the overlap to pull more fuel rich air in?

You might hunt up so custom made rocker arms, or alter some for higher lift on the exhaust, that would get you part way there. Our Pontiacs like to run with 1.65 exh and 1.5 int rockers, so maybe the Chevy would to.

Until its tried, we won't know if it works or not,

Joe

Good idea with the rockers. Or maybe a different intake would be easier. Or is it the head that is siamesed? Sorry, new guy here just kickin around ideas.

Joe

Both, actually. #1&6 run lean, so the first place I want to start is the Intake duration on those valves. I have an older Sun engine analyzer that will measure RPM drop across the cylinders, which is crucial for the correct data for before and after analysis. I was hoping to hear good news about higher lift rockers or rollers, funny that hasn't come to fruition yet, but I put a set on a 223 in a 57 F-100 when I was first getting into the classics, they were in a plain yellow box and just plain steel but they were 1.6 High lift and they recommended the oilier kit which plumbed oil thru a capillary tube under the valve cover into the supplied cap which went on the rocker pipe. It worked until the sludge clogged it. It was a road draft engine. Saw an electric system for that just the other day at a swap meet too. It sucked. Literally.

Torker:

The head is Siamesed but the exhaust ports on cylinders #1&6 are not, all intake ports are, exhaust is shared by #2&3 and #4&5 and the stock and Offenhauser 4bbl intake manifolds cause #1&6 to run lean due to central placement of the carburetor (or fuel injection throttle body). The best solution comes in the form of a triple 1bbl setup.

I too was thinking about checking into a custom grind cam for the 235 thats in my 37,those motors are designed to run at higher RPMs then the later sixes and would like to get one in a RV or higher torque at a lower RPM grind. I have been trying to get my 235 to run good since I put taller gears in it and the gas mileage has suffered,granted I have way too tall gears and will be fixing that before any more tuning happens but would like to get the engines sweet spot at 2200 to 2400 RPMs down to around 1800.

Less duration than stock, with .500" lift?

Even if they can not gring the lobes different, you could just add lift to the intakes in question by cutting the base circle smaller. Over on the HAMB site ( Jalopy Journal.com )there was a post about custom cam regrinders. There were still two or three left around the country that could repair and grind old cams.

You could just bypass all this and turbo it!

Joe

I was wondering if a split duration cam would help those motors,a little more on the exhaust side then the intake.

We have a place in Wichita. Chet Wilson Engine Service. Not sure if on the web but they chop v-8s in half and make v-4 midget motors and grind their own cams. I run one in my 60. Might give them a call.

316-264-5155

[url=]http://www.chet-wilson.com/[/url]

I believe this is commonly called a "Bulldog" cam which is dual pattern with longer duration on the exhaust and I think Tom Langdon still sells them.

As for the rest of this topic flowbench research I have been involved in shows flow stall to be the bigger issue negating benefit of more lift either by cam or rocker ratio. The Webshots link in my signature has an album of the head sectioned thru the ports if interested.

Master Delukse: I'm sure your aware of the old timers who used the lump port design to improve airflow and it works if properly done. Unfortunately there are few who are capable of doing it. So many people have abandoned the tried and true inline engines of yesterday which is unfortunate. Jim Headrick's work on head development lead to his original idea ( I think it was his) of using different centerlines on the cam. Regardless, it has produced some astonishing results with modified factory heads. Others have pursued what is held as the Holy Grail of StoveBoltdom, the Twelve Port head. But who can find one or afford one? So I find your ideas interesting and worthwhile. I hope you are successful.

The lump installed in the heads are for the 230-292 heads, never heard of them in the 235 head. Joe

I believe that the cams ground by Frank McGurk back in the fifties were all dual pattern, with the exhaust usually having 10 to 20 degrees more duration than the intake. I believe that there was no cylinder-to-cylinder variation. On the the inliners' BB a couple of years ago there was discussion about the merits of changing the intake timing for 1-2 and 5-6 to compensate for the unequal firing increments for those siamesed port pairs.

The discussion was all for the 230-250-292 heads. It sounded like Jim Hedrick and others have tried the tailored cam timing with some success. Nothing was said about the exhaust timing, but, as the same 240-480 degree differences in firing exist for the exhaust in the 2-3 and 4-5 exhaust ports, there may be some benefit in changing the timing for those lobes. Would this also be beneficial for a 235-261 head? Has anyone ever measured the benefits on a 230-250-292? Certainly an interesting project, if one has the smarts, time, and other resources to see it through.


Hoyt

Here's the air flow on a 235 (216, 261) with a factory oil bath air cleaner. Air comes in horizontally, makes a 90 degree turn to go verticaly down to the surface of the oil, then makes a 180 degree turn (the oil is below the carb top) and then a 90 to get over the carb throat, a 90 to go down through the carb, a 90 to go along the intake manifold, a 90 to turn into a runner, a 90 to go up to the underside of the intake valve, and finally a 90 to go out into the cylinder. I would think a custom intake that held Webers or Mikunis to make a straight shot to the intake valves would make more sense and be way more tunable. The carb on the siamesed port could be adjusted to give the same air/fuel ratio as the individual runner ports. Years ago on our sprint car the injectors could be tuned so the front to rear and right side to left side cylinders gave the same plug readings.

Not that easy.
#1 & 2 intakes are common, but #1 exhaust is individual, and #2 exhaust is paired with #3 exhaust.
How could that carburetor be adjusted to give different mixture to 2 very different cylinders?

Chevrolet installed 3 side draft carburetors on the 235 1n 1953 and 1954 on the corvette. Probably the best state of tune possible without the '12 port head' previously mentioned. The camshaft profile re-engineered is the next best thing to it. Otherwise you could just get busy with a welder and separate the siamesed ports and fabricate runners for 6 sidedrafts and then the same for the 4 shared exhaust ports but that would be.... ridiculous. For all that effort you would constrict airflow...Square Zero

Your right, it wouldn't be easy but since there are no consecutive exhaust pulses into any of the siamesed ports headers could be (maybe) designed to get the approximate same flow between single and siamesed ports. Strictly a guess would be the primary tubes on the single ports would have to be BIGGER to drop the velocity and diminish the scavaging effect to that of the siamesed ports. It would be fun to play with this on a flow bench.