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Old 02-17-2011, 04:46 PM
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Originally Posted by F-BIRD'88
Seems you are jumping to conclusions based on the appearance of the specs and some negative internet opinions from some that had a less than favourable first experience mostly from lack of knowledge of the setup and tuning changes required for these cams. Or couldn't be bothered to do it.
The thumpr cams and all other high overlap cams need a few setup things that most are not aware of.

To make the most of the cam in your motor will needs some specific set up changes. You have the right 3500 stall converter.

The small 670cfm carb is costing you more performance than the cam is.
Its too small for max performance
A 750 to 800 cfm carb is better. A Proform 750 HP style carb centerbody is a cool upgrade.

The engine compression ratio is way too low.

You need to raise the real compression ratio up as much as is practical.
Your truck motor probabily has factory dished pistons.
Remove the heads, shave them by .040"-.050" reinstall with thin .015" felpro 1094 shim head gaskets.
The closer you can get it to a real 10.50:1 cr the better.
The distributor advance curve will need to be set up for the cam.
See my post on big cams and timing curves.
Start by locking out the timing and try it. (34-36 deg)
4.10's aren't much gear for this 350, heavy vehicle combo for drag racing.
a 4.56 to 5.13 would be better.
Make the best of what you got by using a very short diameter BFG drag radial to max the effective gear ratio. EG: P225/50-15

To make the thumpr cam work best (at the track) you want to open the exhaust and add collector extensions (approx 18 to 22")
The cam has to work with the exhaust system. The engine has to breathe deep and freely to use the high exhaust header scavaging effect to make power.

All these changes need to be done even with the Lunati BM II cam try the cam you got.
Thanks F-Bird, i will try this before i do anything else, i honestly dont mind this cam, but i think its just my combination of stuff thats making it not perform.

Question, is a 850DP Holley too big for this. all i have are 650's and a lonely 850.
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