I have a DSS 306 Pro bullet, Edelbrock RPM II intake, and TFS track heat heads. Planning on getting a custom cam from Anderson Ford. Should I use 1.6 or 1.7 RR?
Thanks,
Brian
If your getting a custom cam, it won't matter really because they will just machine the cam differently. Although OTS cams are usually grown to 1.6 specs and with some cams the lift would be too high with 1.7's. However, with some cams, the 1.7's give the extra lift the cam needs, like the B cam that I have.
90Mustang is getting at the issue - talk to your cam grinder about the appropriate ratio before you buy. The custom specs should specify a certain lift - they should be able to spec a lobe that will work with either ratio. If you're using stock base circle cam and stock length pushrods, the valve train geometry may be a bit better with 1.6's since that's the stock ratio. Piston to valve clearance is impacted very, very little by the difference between the ratios (something around 3 to 4 thousandths). With changes like yours absolutely should be measured, but inless you're right on the edge of minimum clearances, the ratio change won't hurt you.
I have a crower cam part # 15512, its lift with the 1.6 are .496/.512
but since 93 cobras come w/ 1.7's my lift is .527/.544 ... This is used in a 331.. I had this cam in my stock 5.0 and i had my pistons notched, plus it was way too big for my stroke which caused a huge drag in the lower rpm's...But The way you figure your lift for the 1.7 is by using this equation..
Intake lift / 1.6= X , X * 1.7= Intake Lift , same for the exhaust side..
so if you want to figure out what your lift is for 1.7 r.r thats how you do it.. Then from there you can figure if the cam is too big for your engine, having clearence issues, which means you would have to notch your pistons. But like everyone said, if your having a custom grind cam, then you dont have to worry about anything...good luck
Since you are going with a custom grind, I would say just go with the 1.6's. There will be no need to alter the lift of the cam, since it will be ground to certain specifications designed to your setup. I don't know if it is true, but I heard that the higher ratio you go, the more stress you have on the valvetrain? I don't know about that though. I would just go with the 1.6's in your case.
Chris
p.s. 93cobra12: How much for the stock cobra intake?