830cfm dbl pumper with a GM part number for Trans Am?

[firstgenaddict]

I just saw this carb on ebay... has anyone heard of the part number? 3965736 List 4830

HELLO , THIS AUCTION IS FOR A CHEVROLET TRANS AM RACING HOLLEY CARB. IT HAS BEEN REBUILT AN NEVER USED SINCE THEN.FROM THE RESEARCH IVE DONE ITS A 830 CFM DOUBLE PUMPER AND WAS MADE TO USE ON 302 / LT1 350 MOTORS. THE GM NUMBERS ON THE AIR HORN ARE 3965736 LIST # 4830 AND DATE CODE 093 PLEASE TAKE A MINUTE TO LOOK AT MY OTHER AUCTIONS . THANK YOU !
https://www.ebay.com/itm/1967-68-69-70-71-72-CHEVY-CAMARO-Z28-HOLLEY-TRANS-AM-RACING-CARBURETOR-302-350/202668468852?_trkparms=aid%3D1110002%26algo%3DSPLICE.SOI%26ao%3D1%26asc%3D20190711095549%26meid%3Ded2a75510e784d64811e8b962c8ce5f2%26pid%3D100047%26rk%3D1%26rkt%3D12%26sd%3D203029964098%26itm%3D202668468852%26pmt%3D0%26noa%3D1%26pg%3D2047675%26algv%3DSellersOtherItemsV2%26brand%3DHolley&_trksid=p2047675.c100047.m2108

[cook_dw]

http://www.camaros.org/forum/index.php?action=printpage;topic=1822.0

[PHAT69AMX]

I only have an 'opinion' based on years of Holley research.
SCCA Trans Am Rules allowed two for barrel carburetors in the 1968 season, so the 302 crossram.
After that SCCA changed the rules to allow only one 4-Barrel Carburetor.
All the FIA SCCA Homologation Papers I have looked through, when it comes to carburetors,
only specify the number of inlet openings and the maximum diameter, and that's it.
The do not specify a brand, make, or model of carburetor, or a List Number, or a manufacturers part number.
The SCCA Trans Am spec was 4x 1-11/16" Diameter Throttle Blades or Butterflies.
The biggest Holley up to that time was a 800 CFM with 4x 1-11/16" Butterflies,
but it had only a 1-3/8" Dia Primary Venturi, a 1-7/16" Dia Secondary Venturi,
it's only difference to the 750 CFM was the secondary venturi was 1/16" larger diameter.
But there was what Holley, laughingly imho, called the 850 CFM, unlike all the other popular carbs
only the 850 CFM had all four 1/16" larger 4x 1-3/4" Diameter Throttle Blades / Butterflies,
as well as all four 1-9/16" diameter venturis !
A huge jump from a 750 CFM which had only 4x 1-3/8" Venturis and 4x 1-11/16" Butterflies.
So since the SCCA Trans Am Rules dictated ONLY the 4x 1-11/16" Dia max 'opening size'
GM had Holley 'mate' the 850 CFM Main Body with huge 1-9/16" Dia. Venturis
to the 'smaller' Throttle Plate that had 'only' 4x 1-11/16" diameter Butterflies to create the List 4830
and called it a 830 CFM, met the SCCA Rules, and flowed gobs of air.
But being as it resulted in almost no venturi shape it was impractical for use as an OEM carburetor imho.
It would interesting to see the bottom of the 4830 Main Body and see how it was reduced to 1-11/16.
1971 Holley Numerical Listing shows List 4830 as being 812 CFM.
Universal Holley List 4788 is very similar, but has no GM Part Number stamp like the list 4830.
Holley calling the 4781 a 850 CFM or the 4830 a 812 or 830 CFM is interesting since the
more modern Holly HP 950 CFM carburetor has the 850 1-3/4" Butterflies and the 750 1-3/8" Venturis.

[crossboss]

Phat-
It is my understanding the 830 cfm carb was as you mentioned a 'reduced' ventri, yet retaining the 1 11/16" throttle butterflies. This was done to make it 'legal' in the sense of the rules so to speak. However, as it is known many racers used carbs that were essentially 'legal' were no where near the 830-850 cfm 'ratings'. Far from it. Many were modified to be closer to around 950 cfm, some possibly around 1,000 cfm! 1970 was the year that ruled only a single carb can be used. Yes, it was noted that any carb could be used, not just a Holley. This also caused a controversy in the rules, that Ford had an ace up their sleeve with the infamous Cross-Boss intake and Inline carb. Ultimately, the SCCA got wise to this and banned it.

[firstgenaddict]

Thanks for all the information...