What if...? Question on retarding cam...

andy669 · 09-14-2002, 08:07 AM

Chris I have tested that method on two different cars and I have had mixed results.

The first car was a friends 83 with a 351w. It has 11:1 static compression ratio (approximately) and a cam similiar to the TFS stage 2. The further we advanced the cam, the more cylinder pressure we obtained. We ran the car on the street with the cam at -4 and +4. The car ran much better at +4!

The second car was another friends 91 lx. It is a NMRA Real Street spec car. Its a .030 over 302, stock cam, custom flat top pistons, zero decked, 58cc chambers, and a .037 squish distance. The static calculates out to about 10.2:1. Also in that case the further we advanced the cam the more cylinder pressure we got. We know from all the NMRA Factory Stock, and Real Street stuff we have done, that isnt where the cams like to be. 4 degrees advanced (where we got the most cylinder pressure) is exactly the opposite of where we know they run best.

I'm going to have my Pure Street engine on the dyno most of the winter. I will be testing multiple cam grinds, and also the position they are installed. I believe theres more to be learned, yet.

Andy

09-14-2002, 08:07 AM	#7
andy669 Registered Member Join Date: Jan 2001 Location: Moline Il Posts: 901	Chris I have tested that method on two different cars and I have had mixed results. The first car was a friends 83 with a 351w. It has 11:1 static compression ratio (approximately) and a cam similiar to the TFS stage 2. The further we advanced the cam, the more cylinder pressure we obtained. We ran the car on the street with the cam at -4 and +4. The car ran much better at +4! The second car was another friends 91 lx. It is a NMRA Real Street spec car. Its a .030 over 302, stock cam, custom flat top pistons, zero decked, 58cc chambers, and a .037 squish distance. The static calculates out to about 10.2:1. Also in that case the further we advanced the cam the more cylinder pressure we got. We know from all the NMRA Factory Stock, and Real Street stuff we have done, that isnt where the cams like to be. 4 degrees advanced (where we got the most cylinder pressure) is exactly the opposite of where we know they run best. I'm going to have my Pure Street engine on the dyno most of the winter. I will be testing multiple cam grinds, and also the position they are installed. I believe theres more to be learned, yet. Andy __________________ 88 coupe 91 LX NMRA Pure Street 5120

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