3811 Holley (67 427/390hp)

[Dave C.]

My 67 427/390hp engine is currently on the dyno and my friend tells me the engine is running a bit lean. I have a restored 3811 on the engine. But does it have the right jets etc. I understand the primary metering block should be 4796 but that is all. Is there an online resource that has any technical data, I tried Holley but they do not reference 3811 or the gm number 3906633EO. Thanks for any help.

[Dave C.]

Re: 3811 Holley (67 427/390hp)

Never mind found the info and we went from 65's to 68's and car runs great.

[William F.]

Re: 3811 Holley (67 427/390hp)

Dave,
What's the altitude where you live? I'm close to sea level and my same carb/engine may be a bit lean, also with the stock 65 jets. Do others think this carb/engine needs 68 jets instead of the factory jets due to today's gas formulation?

[Dave C.]

Re: 3811 Holley (67 427/390hp)

I live in Indianapolis and google says were at 862 ft. When we rebuilt the engine we used a newer design cam, balanced the components and improved the flow in the heads to a small degree. I think all this could have contributed and even though the holley carb is rated at 585 cfm, in reality it is closer to 560 cfm.

[Clem Z.]

Re: 3811 Holley (67 427/390hp)

if the engine dyno room had a cold air intake that could be the reason for the different jetting. remember you have under the hood temp of close to 200 degrees unless you installed a cold air intake on the corvette

[Dave C.]

Re: 3811 Holley (67 427/390hp)

Good point I will share your comments with the builder. Thanks