VCCA Home Forums TECHNICAL - GENERAL Trucks and Vans dual pattern/profile cams for the 235 cu. in. six

I will be re-building a '56 235 with mild cam, dual 216 Rochesters, dual exhaust, etc and since there is not a lot I can do to the exhaust in the way of reasonably priced porting, was hoping I could use a dual profile cam to advantage. A longer open time on the exhaust would seem to be a good thing. Are these cams a reasonable move, and if so, are they available and from whom. Anyone have any experience with these cams on the 235?

I was also thinking about one for the 235 in my 37 but I still have a noise in the motor and if its replaced its V8 time.

The 1956 235 already has a high lift cam.....same cam as used in a 6 cylinder Corvette and 261 truck engine.....That being said what is a dual pattern profile cam?

Basically, a dual pattern camshaft takes advantage of science not available back in the day. Hypothetically, if the exhaust ports are weaker and can only flow say 80% of what the intake ports are capable of, the cam is ground with a different pattern on the exhaust to "balance out" the two instaed of the original design where intake and exhaust lobes were ground with the same lift and duration specs.

Greg

If you already know the difference in flow from intake and exhaust ports, wouldn't it be simpler to open the exhaust ports to match the intakes instead of a different cam??

Some years ago, there was Branch Flowmeterics, a well known machine shop in Calif, I think, that did wonderful work on motorcycle heads. Don't know if they are still in business or if they also do car engines. Sounds like you are going to build a good runner and having the head flow tested and balanced would do a great justice to the overall preformance.

I am just thinking aloud here and am not trying to tell you what to do. Just wishing you the best in your eng rebuild.

Jim.

It's not my project. I was just trying to explain the theory behind a dual pattern camshaft. Looking at the changes in science since the original internal combustion engine, I am sure there is much greater understanding of flow patterns. It makes sense to me that intake charge is drawn in under vacuum and exhaust is pushed out under pressure. With the exhaust actually helping to draw a fresh intake charge in. The engineers that understand the dynamics of the process are well beyond any level that I will ever comprehend and I think that more is known today than was when the early engines were rolling off the assembly line.