Thread: Tuning help

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I have bult a sbc bored .030 over size. Stock internals and heads . edelbrock performer intake. It has a comp cam 12-242-2 I am having trouble with vacuum. It is very erratic the needle jumps up and down between 5 and 15 inches of vacuum i have adjusted carb and still does this checked for intake leaks and can't find any. timing is set at 10 degrees BTdc .I have broken in the cam and proceeded to adjust idle speed, carb settings, etc, that is when i noticed the vacuum doing this .Any help would be appreciated.

Welcome to the site-
Where in Bolingbrook??

i am in the southern most part of bolingbrook. More like Plainfield actually. naper/plainfield and 126.

That cam wants 10.0:1 to 10.25:1 static compression ratio and I'd guess you don't have a clue what your SCR is. It's probably somewhere around 8.0:1. Hot rodding a motor is not just conjuring parts out of thin air and hoping for the best, it's measuring and choosing the correct parts that will compliment each other to help make power. Please read this tutorial....
http://www.crankshaftcoalition.com/w..._compatibility

The erratic vacuum could be a number of things, from valves adjusted too tight to leaks at the gaskets between the heads and intake manifold (which you will never find by spraying around on the intake) to burned valves. Small block Chevy parts have been around for over 50 years and you have no idea what the guys who had the parts before you did to them. They could have angle milled the heads and cut the manifold to fit, then you came along and used an uncut intake manifold and there is the vacuum leak. You'll never seal it up. I have no idea what has happened with your parts, I'm just trying to get you to see the importance of measuring and matching each and every part before you put the motor together.

The Edelbrock Performer intake is not a performance piece. Its only saving grace is that it takes a few pounds off the front end of the vehicle. Other than that, a bone-stock production iron piece will do the same job. The best intake manifold for a small block 350 Chevy on the street is the Edelbrock Performer RPM #7101, matched up with a 750 carb, vacuum secondaries for auto trans with converter stall of less than 3000 rpm's or double pumper for manual trans or auto with 3000+ stall. The Edelbrock #7101 or the Weiand #8150 are both currently available new and will make more power 1500 to 6000 than any other manifold, including single plane designs. The same design can be found used under Holley #300-36 (Street Dominator) or the Weiand #8016 (Stealth).

Also, you have no clue that the ignition timing is what you think it is without finding top dead center. Refer to this tutorial....
http://www.crankshaftcoalition.com/w...op_dead_center
Once you have done this, re-time the system with 16 degrees at the crank and 20 degrees in the weights, all in by 2800.

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PM me a phone number-I'm up near 59/64

Thanks for the help. Its nice to see that this is a friendly forum.