holley spreadbore
Thread Starter
Racer
Joined: Aug 2022
Posts: 315
Likes: 475
holley spreadbore
hi guys looking for advice. i picked up a holley 4175 650cfm model 9895spreadbore to replace the leaking reman quad jet that i was informed not worth rebuilding. i’m in the middle of rebuilding the holley an not having a lot of knowledge on jetting and looking for a good base line. my vette is a 80 l48 with summit ram horns 2.5 collectors 2.5” true dual exhaust an a weiand 8004 intake. i researched holley’s site and found master spec sheets but doesn’t specify what size jet was factory. the carb has 59’s in it but it’s from 1986 so who knows how many times it’s been changed. guy i got it from said he had it on a 75 vette.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
The list 0-9895 spreadbore uses the close-tolerance jets from the factory, identified by the 3-digit jet numbers. This carb came stock with 122-592 primary jets, which are a close-tolerance #59 jet. Stock accel pump discharge nozzle (aka, "squirter") is 37. The biggest problem with this carb is that is comes with the "black" secondary diaphragm spring, which effectively prevents any operation of the secondaries. Switching over to a "purple" or "tall yellow" will get the secondaries working for you.
Lars
Lars
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
You will most likely need an LT-1 style base.....it has ears on it to clear the float bowls.......a lot of cheap aftermarket ones do too.....I believe the old stock twin snorkel air cleaners have a Q-Jet cutout at the airhorn that isn't full round.....it has a small ear on it to hug the Q-Jet airhorn to locate it.....
Jebby
Jebby
Drifting
Joined: Oct 2020
Posts: 1,567
Likes: 576
From: Wisconsin
Early C3 Stock twin snorkel Q-jet air cleaner assemblies are crazy expensive for some reason, and out of stock.
I wanted to get one to replace the aftermarket assembly on mine, but I might just have to go with the open style.
I wanted to get one to replace the aftermarket assembly on mine, but I might just have to go with the open style.
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Drifting
Joined: Oct 2020
Posts: 1,567
Likes: 576
From: Wisconsin
Mr. Gasket (I think?) makes a air cleaner spacer kit with 3 or 4 different height spacers that you can also stack if you need it to get the right height.