Best jet size for BB
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,002
Likes: 0
From: Bay City MI.
Best jet size for BB
My 467 BB is running rich and I am going to try smaller jets. It has a Holley 780 dual feed carb, Crane 296-2 cam, 9.5to 1 compression. The jets are now 76 primary and 78 secondary. It runs good, but there is black smoke when you hit it. Its not in the car yet and I want to make the change now , much easier. Thanks for the input
Safety Car
Joined: Aug 2000
Posts: 3,909
Likes: 26
From: Clymer PA
Re: Best jet size for BB (467-Ratman)
The black smoke that you described whenever you "hit it" is normal. Personally I would have opted for a slightly larger carburetor, but yours should serve you fine. Does the engine bog at all whenever you give it a wide open throttle shot? If it doesn't then I would say that you are fine and I wouldn't change the jets.
Drifting
Joined: Jul 2001
Posts: 1,418
Likes: 1
Re: Best jet size for BB (467-Ratman)
Your actual jetting is close enough for now.You probably have a blown power valve if idle is rich or it might be opening too soon because it is not sized for the vacumm the engine makes with the camshaft.Maybe too large of a primary squirter.There are many ways to fine tune a Holley with power valves,pump squirters,accelerator pump arm/cam adjustment ect.My advice would be to run the motor in on the street then start the fine tuning first with the power valve.You will need a vacumm gauge for this.
In actual real world sizing of a Holley carb,if 5 steps up from stock out of the box jetting still shows a lean plug reading,your carb is too small.Assuming of course adequate fuel supply,floats are set correct,ect ect.
But I think you are near the right size carb now because of your compression/cam.
In actual real world sizing of a Holley carb,if 5 steps up from stock out of the box jetting still shows a lean plug reading,your carb is too small.Assuming of course adequate fuel supply,floats are set correct,ect ect.
But I think you are near the right size carb now because of your compression/cam.
