Race Cam selection

1795 · #1 (**permalink**) 04-19-2021, 06:00 PM

It is interesting to see the variety of flow numbers that people get from SBF heads. Found a chart online that listed results from a variety of manufactures.

https://www.google.com/url?sa=t&rct=...1SqRFtb-QkdRfS

The results vary significantly from a stock 289 head at 166 cfm Intake (.600) and 125 cfm Exhaust (.600) to a Kasse SVO head at 374 cfm Intake (.600) and 273 cfm Exhaust (.600).

When I was discussing my heads with the engine builder at Cobra Automotive he was saying that their ported race heads are producing over 300 cfm at .700 intake. Heard from several people that my heads in their old form with flowing about 260 cfm at .700 were the limiting factor in my engine. In addition, you have to factor in the carburetor's flow capacity, as while the head might be able to flow a certain cfm, a restrictive carb system will have an impact and the head can only flow what the carb provides.

I have settled on getting cam options from three sources based upon my discussions with them. They are Brent, Cobra Automotive and Shelby Racing Engines. Dema Elgin supplies the cams for Shelby.

Should be able to make a decision soon, as I need to get this engine together.

Jim

talos · #2 (**permalink**) 04-19-2021, 09:34 PM

Just remember, you get what you pay for. Mr. Blykins had a special camshaft ground for my side oiler with the combination I had given him and the results I was looking for. It was perfect for what I wanted. A lot of people asked for my cam specs. His years of experience is worth the investment alone. I went through two previous cam grinds with unsatisfactory results, from other sources, before he assisted me.

1795 · #3 (**permalink**) 04-20-2021, 05:12 AM

Thanks for the input. Money is not a consideration, they are all within a $100 of each other. It's just sorting out which one will be the best one for this application. Without going into specific grinds, the lifts for intake and exhaust are all in the low .600's, but from there the departures begin. LSA has a range of 6 degrees between lowest LSA and highest. There is quite a variability in duration @.50 and in lobe shape.

Have to consider multiple factors in determining which one. All of the people giving input and making recommendations are well respected with years of race cam development; there are no slouches in this group.

Jim

blykins · #4 (**permalink**) 04-20-2021, 05:26 AM

Unless you have advertised durations, .200" durations, and .050" durations, the lobe shape would be undefined. I purposely do not give out all of that information.

cycleguy55 · #5 (**permalink**) 04-20-2021, 02:34 PM

Quote:

Originally Posted by blykins

Unless you have advertised durations, .200" durations, and .050" durations, the lobe shape would be undefined. I purposely do not give out all of that information.

Having that information would allow someone to reverse engineer your cam designs. It's certainly understandable why you wouldn't be giving that out.

1795 · #6 (**permalink**) 04-20-2021, 04:18 PM

Quote:

Originally Posted by cycleguy55

Having that information would allow someone to reverse engineer your cam designs. It's certainly understandable why you wouldn't be giving that out.

That is true, if someone were so inclined. I am not. I will not be sharing any cam design information, and have not, with any cam designers or anyone else other than the person building the engine (who is not and does not design cams) and ultimately the final decision is mine. My expectation is that they provide me with enough information to make an educated decision based on the merits of their choice, not due to why the other choices are deficient.

As with any field, there is a great variability in opinions and it is up to the buyer to do due diligence in examining the merits of all opinions.

Jim