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.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.
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.
I'm not sure - It's got the coiled spring that's mounted on the manifold under a shield.Free Shipping - Holley 4165 Carburetors with qualifying orders of $99. Shop Carburetors at Summit Racing.www.summitracing.com
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 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.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.
Thanks! I've got a manual 4-speed so should be good.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..