Cam Theory Questions

How does cam lobe angle affect cooling? With the same duration and lift will a 110 degree seperation run hotter or cooler than a 108 degree angle? Will advancing the cam make it run hotter or cooler? Will a blower change the results?
Thanks in advance.
Pete

 

Hmmm. How technical an answer do you want?

I might ask it from a somewhat different point of view..."I chose a particular LSA to make the engine perform well under a specific set of conditions. By the way....what, if any, overheating problems might I expect as a result of those operating conditions?"

In practical use, the LSA has limited effects, if any, on the operating temps. I can say that a tighter LSA, on, say, a 350 SBC, could cause slightly higher EGTs at higher rpm levels as a rule...more efficient combustion & greater volumetric efficiency. There are so many variables to affect this, though...jetting would probably be somewhat different, as well as timing, so it's stretching things a bit to lay it all at the LSA's door.

To directly address your question, the difference between a 108 & 110 LSA is fairly small in the avg. 350, for the most part, both in terms of power & effects. Smaller engines will notice it a bit more, but it's still not a huge thing...four degrees is more noticeable. Advancing the cam can alter things, but it depends on the cam profile, how it was ground in the first place, and a lot of other details about the engine. I wouldn't concern myself about cooling when I chose the LSA, between the two.

A blower will certainly affect things in a general sense, but it doesn't have much of an effect on the LSA in terms of cooling, unless the LSA was wildly off from where it should have been in the first place.

All this is pretty vague....a few more details about the engine in question might help.

 

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Oh yeah, never heard cooling brought up in this way before

 

I need to clarify this- obviously the LSA can't be affected, it's a fixed quantity. What I mean is, the interaction between the blower & the LSA spec, whatever it may be, isn't an issue.....it's the blower itself that will affect the temps (unless the LSA is very "wrong" for the engine & its intended use.)

So far as "Jeopardy" goes....there's always the ever-popular "Anal Bum Cover".....(an album cover).

 

Let's try this example: A 454 Chevrolet is cruising for hours at 2200 rpm in a 3,000 lb coupe. It is jetted correctly. The timing is correct. Will it run cooler with a lsa of 108 degrees or with a lsa of 114 degrees? Both cams are set straight up. If you advance the cam 4 degrees will the engine run hotter or cooler?
Thanks again.
Pete

 

Best sources I know of for detailed discussion of cam variables and their effects is Vizard's "Small block chevy camshfts and valvetrain"
The head and crank books in same series are also excellent, even for people thinking about different engines entirely. On cams, this book is superior to Yunick's book, I think.

 

Vizard's book is exhaustively documented with dyno runs from a zillion engine builds and experiments, Yunick's is obviously the distillation of 50 years of high level racing...I have to read the cam sections very slowly, in small bites...half a paragraph and my head is full of stuff I never even thought of before. Both men are/were mechanical geniuses and relentless experimenters, miles beyond state of the art thinkers.