Quadrajet Replacement and HEI Options

Bent77

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Yes there’s different sets for different years. We’ll see where @Entropy goes with it
 

Entropy

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I know quadrajets fairly well, if you replaced yours with a commercial rebuild it's probably no good. Any rebuilder that removes the bronze colored coating from a carburator doen't know what they are doing, and just ruined that carb for ever more. Pass them by. 1 mistake that is common people tend to over tighten the front two bolts this warps and distorts the carb, causing all kinds of issues. Hopefully your replacement is decent. I would do the HEI conversion then see how thing go. 7200 feet, i am guessing you could leave the choke off except on the coldest mornings. Most common main jet for 350 Qjet is .69 with 37B rods and who knows what primary rod spring. For yours if not already I would 67 jets leave the rods alone, use the blue spring in the metering rod piston. maybe lower float level. I found mine wasn't getting enough fuel no matter what mechanical pump I used, I finally went electric with a return to tank, dead heading the electric pumps caused them to over heat and die.
Mine is still the original, but it has been rebuilt I'm guessing 4 times (twice during the time I've owned it). It seems really likely to me that one or all of the issues you mentioned likely happened to it over the years.

Intake choices...I would suggest a dual plane for the best low end. Single plane will make more power at the top of the range, but at the expense of the low end power/response. For a mild small block, I'd consider the RPM Air Gap from Edelbrock.

Thanks! I will check that out.
 

Wes Harden

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Oh and I forgot when you search for your hei stick with ac delco, I know these days isn't much better than others. I had a Proform hei fail in as little as 6 months wasn't oiling properly
 

Entropy

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this bad boy will bolt on to your manifold. will be jetted way to rich for your alt. what style choke do have now? manual or divorced ?
I'm not sure - It's got the coiled spring that's mounted on the manifold under a shield.
 

Wes Harden

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that would be a divorced choke. you could go to an electric choke, will need to add a keyed hot circuit. I personally would look for a carb that accommodates the divorced choke.
 

Bent77

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The spring for that divorced choke is replaceable, too
 

6872xtc

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Having owned a couple of regular Edelbrock carburetors, I like the Quadra-jet better if you get it ironed out. It doesn't care anywhere near as much about angles or larger bumps.
BUT I did get my throttle shaft bushings done, and then later, when I went to a roller camshaft, I had to send it to Sean Murphy Induction to have him work it over. He did a great job, and I don't mess with it. He wanted to know as much as possible about my truck specifications and my use of it, plus my general elevation. Great work, but it wasn't a quick job.
I used Ethanol free gas mostly, and especially if it sits a lot.
No matter what one, a carb spacer to lessen heat soak is a great addition.

Stock HEI should be perfect, you may have it fit tight against the firewall, I had just enough room with mine, but I have heard of guys needing some massaging of the firewall, even though they had a small block.
 

Entropy

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Having owned a couple of regular Edelbrock carburetors, I like the Quadra-jet better if you get it ironed out. It doesn't care anywhere near as much about angles or larger bumps.
BUT I did get my throttle shaft bushings done, and then later, when I went to a roller camshaft, I had to send it to Sean Murphy Induction to have him work it over. He did a great job, and I don't mess with it. He wanted to know as much as possible about my truck specifications and my use of it, plus my general elevation. Great work, but it wasn't a quick job.
I used Ethanol free gas mostly, and especially if it sits a lot.
No matter what one, a carb spacer to lessen heat soak is a great addition.

Stock HEI should be perfect, you may have it fit tight against the firewall, I had just enough room with mine, but I have heard of guys needing some massaging of the firewall, even though they had a small block.
I might stick with the Quadrajet if I could find someone that knows them well enough to do a competent rebuild - or at least be able to evaluate mine to see if it isn't permanently jacked up. After googling Sean Murphy Induction, it seems like they fit that bill.

And thanks for the carb spacer tip as well.

I really appreciate all the comments and advice everyone's given - thanks!
 

diesel4me

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If you use a spacer or adapter (to put a square bore carb in place of the Q-get spread bore) ,and you have a 700R4,be sure the throttle valve cable geometry and adjustment stays within specs or it can burn the clutches up in a few miles..
I saw quite a few GM vehicles that needed a 700R4 rebuilt not long after a aftermarket intake & carb was swapped on back in the 80's...most blamed the "added HP" ,but some had it happen twice because that was the cause and it wasn't corrected..

It is too bad there aren't still new Q-jets being sold that don't cost so much..set up properly,they work the best both off road and on the street..
I'm not a big fan of Holley carbs...Carter AFB and AVS are now Edelbrock clones,better for street use than off road though..
 

Entropy

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If you use a spacer or adapter (to put a square bore carb in place of the Q-get spread bore) ,and you have a 700R4,be sure the throttle valve cable geometry and adjustment stays within specs or it can burn the clutches up in a few miles..
I saw quite a few GM vehicles that needed a 700R4 rebuilt not long after a aftermarket intake & carb was swapped on back in the 80's...most blamed the "added HP" ,but some had it happen twice because that was the cause and it wasn't corrected..

It is too bad there aren't still new Q-jets being sold that don't cost so much..set up properly,they work the best both off road and on the street..
I'm not a big fan of Holley carbs...Carter AFB and AVS are now Edelbrock clones,better for street use than off road though..
Thanks! I've got a manual 4-speed so should be good.
 

Entropy

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Again, I appreciate everyone's responses!

I decided to go with the 650CFM Edelbrock AVS2 offroad with an electric choke, which I'll have to wire up. I'd love to be able to have a divorced choke option, but was unable to find one unless I was willing to stay with my existing quadrajet. I'm sticking with the stock manifold for now and got the adapter plate. I plan to look at a new manifold and some other upgrades at a later date. I also ordered an MSD HEI replacement distributor, new wires and plugs, etc.

I'll post some pictures when I get everything in and get it installed.

I've also been talking to various body shops about getting at least some of the bodywork done, especially the rusted parts. Not much has changed since I last looked into this a decade ago - most shops aren't interested in this kind of work on old vehicles, and most that are interested only do high-end work where even a prep and exterior paint job on a solid body costs the same as a new mid-sized sedan. There isn't much middle ground that I can find. Still looking though.
 

Entropy

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I'm also looking at wheel and tire options. I plan to keep the original wheels and hopefully - eventually - get the hubcaps restored as I still have all four of them and they are original. I've got 31's on the stock rims now.
 

Wes Harden

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31" is @2" bigger than the stock optional tire . Do you know the gear ratio in the differential's? What lift if any are planning changes or want any changes in the suspension?
 

Entropy

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Gearing is 3.73 (stock I think, unless my Dad special-ordered that) and I have the NP205 with the 4-speed manual (really a 3 speed with a granny gear). With the 31" tires it doesn't like to go past 70 (showing ~65 on the speedo), but I'm not planning on a lot of highway driving. I had the suspension and front-end redone and tightened a couple of years ago, so it is pretty stable for a 50-year-old truck and I splurged for Bilsteins as well.

Right now I'm not planning a lift or any major changes at this time. My near-term goals are:

- Get the engine shaped up. That should be done soon, hopefully this weekend if the weather cooperates.
- Get new wheels and tires - The current tires are 7+ years old and two of the original steel rims are a bit warped and difficult to balance.
- Hopefully find someone to do some bodywork and fix the floorplans and some other areas that have rusted through. Right now all I'm finding are shops that only do insurance work or high-end restoration outfits where a basic paint job on a clean body starts at $30k. Nothing in-between.

Edited to add: However, if a lift makes sense for a better wheel/tire combo, I'd definitely consider it. I'd just want it to be pretty modest.
 
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Wes Harden

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You might be able to get 33's on there, 32" would prop work w/o a lift. I saw @Capt Ron had a bunch of rally wheels for sale. You might talk with him. I'm not well schooled on 1 gen tire clearance so someone may come along and say different.
 

Burt4x4

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One mod I remember from my carb days wheeling = Add a 2" long piece of fuel line to the float bowl vent breather tube. This will help prevent fuel from sloshing up and into the carb! It works :saweet: :pimp:

Edlebrock use to sell their own Q-jet version. I bout the 1901 divorced choke cuz my Edl, manifold had a landing pad for it and all my stock stuff just bolted right up so win win

Burt

vent.JPG
 
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