anyway to tell the cfm of a quadrajet carb?

[monte85]

is there anyway to tell the cfm of a stock quadrajet carb? if i have to i could use the part number, but i was wondering if there was some measurement or some kind of telltale sign. i know they made 750's but edelbrock was making some 795's back when they made those quadrajets. i want to find out what the one on my truck is.

[VileZambonie]

What's the part #?

[HAULIN IT]

Monte, The simple way is to look down the primaries. The 750's are completely round on the outer edge, the 850's have a rounded lump intruding in on one spot about an 1/8" in by 1/2" long. Hope this helps, if you need a picture I'll post you one. Lorne

[monte85]

Vile,
the part number on the side of the carb is 17085213 and under that is 0435  hpb.


Haulin,
i looked down the primaries, and about half way down there was a stepped lip that went all the way around. on that lip, there was a bump (in the drivers side barrel, it was more towards the front, passenger side was more toward the back). i think this is what you meant, but could you post a picture anyways, if its not to much trouble?

thanks to you both.

[VileZambonie]

It's most likely a 750 based on the year.

[monte85]

that carb should be enough for my mild 350 right?

[VileZambonie]

Oh yeah

[monte85]

good that's what was hoping you'd say.

[HAULIN IT]

Monte, Here is a couple pictures, they're not real good though. I incorrectly called the large bore carbs 850 cfm in my earlier post. The ones with the "lump" are 800cfm. There is only 750 & 800 q-jets. Hope this helps, Lorne

[monte85]

well i definitly have that bump in the bore. i wish i could read that caption underneath. i looked at another q-jet in my garage and i could see the difference between the 2. thanks.

[HAULIN IT]

Monte, The caption basically reads: In the early '70's the big bore carbs came out, able to be identified by the "bump" inside the bore in the left picture, also noticeably bigger diameter & less pronounced "ring" than the small bore on the right. I found another picture in an other book It says: Big bore primary size (800cfm) is 1 7/32" (top) & 1 3/32" for the 750cfm (bottom)

[monte85]

yeah it looks like the 800 cfm

[75gmck25]

Even the 800 CFM quadrajet might be set up at the factory to limit the total flow.  With certain engines they may have used the larger bore carburetor, but limited the plate travel and/or made other mods to meet emissions control or horsepower rules.  Based on the Ruggles book, you can remove or adjust most restrictions and get the full 800 CFM. 

This discussion on Ruggles site is from a discussion of the 17085213 https://cliffshighperformance.com/simplemachinesforum/index.php?topic=2519.0 .  If you read through the Ruggles book in detail and look at all the performance mods you can make for a Quadrajet, it will make your head hurt.

Bruce

[VileZambonie]

His post was over 10 years ago

[fitz]

His post was over 10 years ago

I hope he's not stuck on the side of the road waiting for an answer.