Quadrajet Jetting Question.
Thread Starter
Racer
Joined: Nov 2009
Posts: 289
Likes: 0
From: Franksville Wisconsin
Quadrajet Jetting Question.
Hi I have a '81 I'm decomputerizing and I put a new HEI dist. and have a 1978 Quadrajet carb i'm rebuilding before installing. It appears to have been rejetted and I was looking for info on stock jetting or jetting used on a 1980 if different. My engine is bone stock build with new stock cam. Thanks in advance!
Thread Starter
Racer
Joined: Nov 2009
Posts: 289
Likes: 0
From: Franksville Wisconsin
I found what i needed to know. I came up with 77 main jets with 53 main rods and sec rod CH for 1978-80 and 1976 same except 48 main rods. I will probably go with 78-80 combo. If anyone has any info or better ideas please let me know. Thanks!
Thread Starter
Racer
Joined: Nov 2009
Posts: 289
Likes: 0
From: Franksville Wisconsin
What color power piston spring should be used.The original # listed seems to be N/A
Edelbrock make a replacment set of four 4" hg 6" 8" and 10". From research looks like either 6" or 8" but not sure which one to go with leaning toward 6" to start. Any help would be appriciated. At this point I'm pretty much committed. I should have bought a untampered (not rejetted)carb.I may go to a Holley in spring time if all else fails.
Edelbrock make a replacment set of four 4" hg 6" 8" and 10". From research looks like either 6" or 8" but not sure which one to go with leaning toward 6" to start. Any help would be appriciated. At this point I'm pretty much committed. I should have bought a untampered (not rejetted)carb.I may go to a Holley in spring time if all else fails.
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
Give Cliff a call or email him, he has rods if you need them and can give you good advice.
http://www.cliffshighperformance.com/
http://www.cliffshighperformance.com/
Racer
Joined: Nov 2004
Posts: 485
Likes: 1
From: Oakville ON
Doug Roe's book suggested 73 jets with 41 rods for a "street rod". This gives 13% more metering area with rods fully down and 12% less metering area with rods fully up. Adjust APT for smooth cruise mixture which I found to be 3.5 turns up from bottom (with headers and full duals). Start there and decrease turns up until you get surge on steady cruise, then go back up 1/2 turn. Make sure you are hitting full bottom of APT adjustment screw - they tend to stick after a while. Carb cleaner frees them up so it goes all the way down as your baseline. Full APT screw travel is 8.5 turns.
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Thread Starter
Racer
Joined: Nov 2009
Posts: 289
Likes: 0
From: Franksville Wisconsin
After research it looks like edelbrock replacment spring kit orange spring is same as original spring. But to get rods for the main jets is a problem edelbrock make some but have wrong tip diameter .36 instead of .26. My '81 ran very lean and if i'm correct it only matters in WOT which I rarley do and if so very breifly. I'm trying to find another actual corvette carb with original jets so I can rob the rods out of it.
Racer
Joined: Nov 2004
Posts: 485
Likes: 1
From: Oakville ON
rods
After research it looks like edelbrock replacment spring kit orange spring is same as original spring. But to get rods for the main jets is a problem edelbrock make some but have wrong tip diameter .36 instead of .26. My '81 ran very lean and if i'm correct it only matters in WOT which I rarley do and if so very breifly. I'm trying to find another actual corvette carb with original jets so I can rob the rods out of it.
Thread Starter
Racer
Joined: Nov 2009
Posts: 289
Likes: 0
From: Franksville Wisconsin
Well I ran the beast with the replacement carb. using 77 jets 52 rods and orange power piston spring.Ran pretty well I think I need to use the black spring it seemed slightly rough (lean) at speed.Does anyone know what color of edelbrock replacment spring is comparable to original part number 7029529 ? Orange seemes to be 7036019 from my research.
