Holley Carb install on 350 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mpierce9 · 05-23-2016, 11:13 PM

A friend of mine gave me a Holley Carburetor (80457-8) with adapter plate. I was interested to see what all I need to do in order to install this on a stock 1975 Blazer with a 350. The current quadrajet runs decent but I'd like to attempt and get the experience of installing a new carburetor. This again, is mostly for gaining the experience.

Currently in the box is a gently used Holley 80457 carburetor and an adapter plate. Thanks.

**MikeB** · 05-24-2016, 11:45 AM

Lots of work for little or no gain in driveabilty or performance over a Q-jet that's working well.

You will need to run the fuel line to the driver's side, which is a major headache with the side-hung float Holleys.

You might luck out and be able to connect the existing throttle cable and trans detent cable (assuming you have a TH350 trans).

These instructions should help: http://documents.holley.com/199r7948-5rev6.pdf

Let us know if you have any specific questions or run into trouble.

Dead Parrot · 05-24-2016, 11:47 AM

Assume nothing, check everything.
Will the air cleaner fit and clear everything on the new carb?
Bolt patterns and bolt lengths.
Studs vs bolts.
Choke connection.
Throttle linkage.
Transmission linkage if auto trans.
Cruise Control linkage if equipped.
Gas line connection.
Power brake vacuum connection.
As a 75, it could have near zero emissions or a full set. You will need to match all of the hoses currently connected to the qjet to matching connectors on the holley.
Do you have gaskets to fit between the adapter and the manifold and between the adapter and carb base?

May have missed a couple of things.

mpierce9 · 05-24-2016, 08:39 PM

Excellent advice. I'm curious about finding additional information for the quoted items (below). I've googled and searched through some installation guides but no advice on what fuel line adapter that would be necessary. I'd also like to understand the transmission linkage further. I've read several notes that a kick down isn't necessary. I'm running a TH350 transmission.

Quote:

Originally Posted by Dead Parrot

Transmission linkage if auto trans.
Gas line connection.

barry1982 · 05-27-2016, 11:38 PM

I guess I'm showing my age (and experience), but sometimes it's best to go with the old saying.... "If it works, don't ^@#@ with it ! "

In my opinion, If your original Q-Jet is working fine, leave it alone. Years ago I plopped a Holley on my 72' Cheyenne. Ran great for a week or so, than crappy. Took it in for adjustment, again ran great for a week or two.... than crappy.... Put my Q-Jet back on, and never looked back. I'm not saying all Holley's are bad.... but mine was.

05-23-2016, 11:13 PM	#1
mpierce9 Registered User Join Date: Nov 2013 Location: ATLANTA Posts: 223	Holley Carb install on 350 A friend of mine gave me a Holley Carburetor (80457-8) with adapter plate. I was interested to see what all I need to do in order to install this on a stock 1975 Blazer with a 350. The current quadrajet runs decent but I'd like to attempt and get the experience of installing a new carburetor. This again, is mostly for gaining the experience. Currently in the box is a gently used Holley 80457 carburetor and an adapter plate. Thanks.

05-24-2016, 11:45 AM	#2
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,465	Re: Holley Carb install on 350 Lots of work for little or no gain in driveabilty or performance over a Q-jet that's working well. You will need to run the fuel line to the driver's side, which is a major headache with the side-hung float Holleys. You might luck out and be able to connect the existing throttle cable and trans detent cable (assuming you have a TH350 trans). These instructions should help: http://documents.holley.com/199r7948-5rev6.pdf Let us know if you have any specific questions or run into trouble. __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!

05-24-2016, 11:47 AM	#3
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,519	Re: Holley Carb install on 350 Assume nothing, check everything. Will the air cleaner fit and clear everything on the new carb? Bolt patterns and bolt lengths. Studs vs bolts. Choke connection. Throttle linkage. Transmission linkage if auto trans. Cruise Control linkage if equipped. Gas line connection. Power brake vacuum connection. As a 75, it could have near zero emissions or a full set. You will need to match all of the hoses currently connected to the qjet to matching connectors on the holley. Do you have gaskets to fit between the adapter and the manifold and between the adapter and carb base? May have missed a couple of things.

05-27-2016, 11:38 PM	#5
barry1982 Registered User Join Date: Oct 2015 Location: Waskatenau, Alberta Posts: 259	Re: Holley Carb install on 350 I guess I'm showing my age (and experience), but sometimes it's best to go with the old saying.... "If it works, don't ^@#@ with it ! " In my opinion, If your original Q-Jet is working fine, leave it alone. Years ago I plopped a Holley on my 72' Cheyenne. Ran great for a week or so, than crappy. Took it in for adjustment, again ran great for a week or two.... than crappy.... Put my Q-Jet back on, and never looked back. I'm not saying all Holley's are bad.... but mine was.



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