What Jets do you use?

[SuperHart]

Finally I have my Cobra Fibercraft Bodied car on the road. I am running a 1969 351W motor with GT40-P heads, 1.7 roller rockers, Isky cam, and an Offy dual plane manifold with a Holley 4777 650 DP carb jetted 67 primary and 73 secondary. The motor seems to run somewhat rich. I am wondering if other club members are using this carb and if they have done any rejetting. If so, what jets are you running that work well. Thanks for any input.

SuperHart's Cobra Project Page

[Dominik]

No reply?

The best you could do is buy an oxygen sensor to ínstall into your exhaust and monitor the air/fuel ratio during all driving conditions.

There are various setups on the market indicating A/F ratio via LEDs.

There is no straight answer to your jet question. It depends on all parts that went into your engine and exhaust.

It is said that the manufacturer' jetting is not too far off from real life.

Dominik

[niles]

O-2 sensor a very good and accurate way.
The old basic way is to do a plug check.
You have to drive the car for several second at the rpm your interested in; ie, 3000 light throttle on primaries, or WOT with a four barrels operating. Jam cluthe in, at the same time cut ignition off; roll to stop. Pull two plugs and carefully inspect. look at a good book for color pictures of what the porcelain looks like. It should be light brown/tan; if its black or sootie-too rich. white too learn. You can't slow down and drive back to garage before pulling plugs as the slow driving and idling for just a few second will mask the previously plug temperature.
grover

[JAM1775]

I have also done what Niles suggests at 5500 rpm. I held it for 1/8 mile in 2nd or 3rd gear, pulled over, read my plugs and made jet changes at home. A few pases di the trick for me. Now...if I could only idle !!!!

[dalola]

Guys,
If you are running an MSD ignition, or equivalent, reading plugs is difficult, as everything tends to get burned off.

O2 sensor is the most accurate way.

Dave

[JAM1775]

Dave..I am a pen stroke away from orering my 02 sensor.
It is defintiely the best way to see what is going on.

[dalola]

JAM, you da man!