Holley jetting

[John G.]

Could someone please confirm stock jetting for my holley on 72 LT1 and the jettings for 70 and 71 LT1's.
thanks john

[William C.]

Re: Holley jetting

If you give us the carb list numbers, it will save us looking them up.

[Terry M.]

Re: Holley jetting

John,

This is one of the "joys" of Holleys. One can easily change enough on them to get then all F*&%ed up.

There is more to the differences in those year carburetors. The metering blocks are different for each of them, and I suspect those differences are more than just the jets -- but I will bow to those with superior knowledge.

If you are really going to dig into this information the list numbers are in the latest version of the 1970-72 TIM&JG -- including BOTH list numbers used in 1972. The TIM&JG also lists the metering block numbers because those are judged.

[Terry M.]

Re: Holley jetting

Could someone please confirm stock jetting for my holley on 72 LT1 and the jettings for 70 and 71 LT1's.
thanks john

I can't believe I am the only one with a 1970-72 TIM&JG reading this who is willing to keyboard all this. Am I missing something? Oh, I know the list is very long.

BTW: Columns never come out right in these posts, so you will probably have to use your imagination somewhat.

From page 59 of the 4th edition, 1970-72 TIM&JG:

LT1 Pri metering block Sec metering block
1970 List 4555 6333 4519
1970 ECS List 4489 6335 6192

1971 List 4801 6808 4519

1972 List 6239A 6828 4519
List 6239-1A 7102 7101

John, You are probably now asking what you are going to do with this, since it doesn't give you the jet sizes. My Holley books are in the cold garage, and it is past my bed time so I am not going after them tonight. I have had enough keyboarding for the day. Let's see if this is enough to prime the pump and where this thread goes.

[Joe C.]

Re: Holley jetting

Could someone please confirm stock jetting for my holley on 72 LT1 and the jettings for 70 and 71 LT1's.
thanks john

68/73

see the following, and find your list number (6239):

http://www.holley.com/data/TechService/Technical/Carb%20Numerical%20Listing.pdf

Those are great starting points, but remember, all carburetors were employed for numerous applications. Your ideal jetting may vary somewhat from these, based on your engine/climate/altitude.

Joe

[William C.]

Re: Holley jetting

Since Terry was good enough to ID the carbs, and my Holley book is handy I'll finish the question, Jetting for the 4555, 4489, 4801 was all the same at a .070 jet in the Primary and .076 Jet in the secondary. The 6239A and 6239-1A both used a .068 Primary and .073 secondary jet. At least per my 1982 edition Holley specs manual.

[Joe C.]

Re: Holley jetting

Since Terry was good enough to ID the carbs, and my Holley book is handy I'll finish the question, Jetting for the 4555, 4489, 4801 was all the same at a .070 jet in the Primary and .076 Jet in the secondary. The 6239A and 6239-1A both used a .068 Primary and .073 secondary jet. At least per my 1982 edition Holley specs manual.

Bill,

Jet numerical sizes do not necessarily correlate directly to orifice diameters:
It is more correct to say that the 6239 requires:
68/73 jet numbers, actually 122-68 primary, and 122-73 secondary.

[William C.]

Re: Holley jetting

I agree, but those numbers are the numbers stamped on the jets themselves, not the longer number. Although from my racing days I remember the sizes to be very close to the stamped number, I believe Holley claimed to flow calibrate them.

[Joe C.]

Re: Holley jetting

Holley Jet Sizes