Kerrmudgeon

How many CFMs were the carbs that came on big block engines from the factory from 396s (65s) to the last 454s? Thanks.

1986coupe

All of the Rochester carbs would have been the same for all 8 cylinder GM vehicles.

Kerrmudgeon

.....but what size are they!

74modified

If I remember correctly, 750 & 800 CFM. I think the 800 version is not so common

Jeff_Keryk

I believe the Holleys were 3310's and were rated at 760 CFM.
I had one on a 70 454 LS6 transplanted from a Chevelle.
Others will chime in.

lars

The Q-Jets used on all Vettes were 750cfm - both big block and small block. No 800 Q-Jets were used on Corvette.

Lars

MelWff

The old 3310 was rated at 780 CFM. Other Holleys were as large as 850 CFM. If you have the carburetor list number you can find it on the Holley site under Technical and get all the specs.

63mako

The highest HP factory rated Chevy engine was the 1970 454 LS6 in the chevelles. 11.25 to 1 compression, solid lifter cam. This was pretty much an all out racing engine. 780 vacuum secondary holley.

Jeff_Keryk

The engine in my 70 Coupe was stamped CRR, which is the 70 Chevelle LS6 450 HP / Turbo 400 combo. The car was not safe as the suspension was worn, and the brakes were, well you know. I was lookin' for Vipers. The engine was worth more than the car; if I only knew... 4 to 6 mpg...

restoman1

Close. The 66 L72 was also rated at 450HP until approx mid October, 1965. It was then downgraded to 425HP because insurance companies were having cows! Same engine, same car, but marketing decided to apease the insurance companies, so it went to 425HP.

Then there was the 69 ZL1 rated at 600HP. Two produced and VERY expensive. 12:1 compression, aluminum block, aluminum heads, 850CFM Holley... all the go fast stuff Chevy had available.

Ed

Ironcross

you forgot the LS-7 and L-88`s both used a 850 cfm Holley

MotorHead

This man would know he had 2 in his boat !

restoman1

Here's a good one for you. The 1966 L36 427/390 used a Holley 3370, rated at 585CFM! I'm amazed they were able to get that much HP out of such a puney carb.

Ed

Mike Ward

Not that the flow ratings mean much or have a direct relationship with performance, but I remember reading somewhere that Holley and Rochester did not use the same method for rating their carbs- so there was a slanted playing field.

63mako

Factory rating on the 1967-68-69 L88 and 1969 ZL1 was 430 HP. We all know better. You are right, all those and the LS6 were rated at an RPM much lower than peak HP to keep the insurance co's off their back.

restoman1

Good point Kevin. As a matter of fact, I just had this conversation with John Hinckley (JohnZ) and although Dobbins states the ZL1 was a "600HP monster", it was still factory rated at 430HP like the L88. In reality, with headers and an open exhaust, both produced more in the neighborhood of 560-580HP. Still much more than Chevy wanted to let on about!

Ed

Ironcross

remember these?.........Motorhead does....

.....1200 HP 18 ft. Drag boat

63mako

Myth has these @ 550-600-650 HP. These were actually 450 hp at best with the factory exhaust systems. They were built to take the exhaust off and run open headers on the strip. Some of the F.A.S.T. guys are pulling 560-580 hp out of these but 525 is about all you will get out of one built to true factory specs on the dyno with open headers according to my research. Those F.A.S.T. engines are $30-50,000. They are totally **** about every aspect of the build and are allowed certain "revisions". Do a search on 1969 ZL1 dyno results and l88 dyno results. When I built Elle88's engine we expected more than the 505 hp we got due to the myths. Then came the research. I have numerous links in his build thread to actual dyno tests on the stock ZL1-L88 engines. Modern heads, intakes and cams will allow a lot more streetable power but in the day these were the king of the track running 11's with slicks and open headers. http://forums.corvetteforum.com/c3-t...ile-times.html

Easy Mike

C2 big blocks used Holleys. C3 big blocks used Q-Jets, with the exception of the tri-carb cars and the exotics (L-88/ZL-1).

resdoggie

I recall something about wet and dry flow testing methods. Holley used wet flow and QJ used dry flow. The dry flow would show a higher cfm flow because the medium was less dense when compared to wet flow testing that Holley uses. Anyone else shed some light on this?