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Rochester Quadrajet questions

Babaganoosh

Babaganoosh

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I'm in need of a rebuild most likely and was wondering where I could purchase the rebuild kit and which one you would prefer for a stock 1978 350. I looked on summit and jegs and they didn't list one for the rochester. Would this book from summit be worth it? http://store.summitracing.com/partdetail.asp?autofilter=1∂=SAD%2DSA113&N=700+115&autoview=sku

I found one for sale but he doesn't know what it is, he listed the numbers 17080560/2130 for a reference, can anybody tell me what this is?




Thanks Guys
 
Just get a rebuild kit from NAPA, Checker (Kragen), etc. Make sure you write down the number off of the side of your carb (or bring it in) to make sure you get the right kit. Get a float too (most rebuild kits don't come with this).

I don't think you need to buy a book to rebuild one of these. The kit should come with instructions, make sure that you take pictures as you are disassembling it to make sure that you put it back together correctly.

Clean everything REALLY well with solvent (laquer thinner, etc.), that's 90% of rebuilding a carb IMO. Blow all of the passages out with compressed air.
 
Also there are 2 (I should say 4 plugs in 2 locations) casting port plugs at the bottom of the carb that need to be epoxied so they dont leak. I dont have any pics right now but maybe someone else here knows what im talking about, and has a pic to show you.

Balzer

Someday I should rebuild one and document it just for CK5 tech.
 
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Thanks for the tips guys, as you probably already know this will be my first rebuild.


Keep them coming. :D
 
Ok, the carb I found for sale is a 1980 Pontiac, would it work on a Chevy 350? also how do I go about getting the right cfm.


Sorry for my questions, I really don't know anything about carbs.
 
yeah most local parts houses will carry the kit you need. like said you will need the number so they can look it up and get the right one. there will be two numbers on the side of it though, of the numbers you posted it will be the long one that starts with a 17.

Ive rebuilt a few and like mentioned cleaning them is the most important part, epoxy on the fuel well plugs is also fairly important. another thing that a lot of people I know over look is setting the float, be sure to follow the instructions and set your float correctly. I always set mine a little low cause its not a hot rod that needs the extra fuel and it helps when you get a little sideways.

I was scared with my first q-jet rebuild but its actually fairly simple as long as you pay attention to where all the pieces go when you take it apart and get it clean.
 
Thanks for the picture reference. Before I do this, it sounds like I need to stock up on carb cleaner and brake cleaner.
 
Babaganoosh said:
Ok, the carb I found for sale is a 1980 Pontiac, would it work on a Chevy 350? also how do I go about getting the right cfm.


Sorry for my questions, I really don't know anything about carbs.
Click to expand...

yes it will work. as far as I know all of them match up the same. as far as cfms the biggest majority were 750 with a few of them being 800s but I dont really know how to tell.
 
Babaganoosh said:
Thanks for the picture reference. Before I do this, it sounds like I need to stock up on carb cleaner and brake cleaner.
Click to expand...

the best cleaner I have seen so far is a 5 gallon bucket of b-12. it may be a bit much if you dont build them very often but you can take the carb apart and dip the whole thing in it. after a few hours pull it out and blow it off. castrol super clean also does a really good job too. you can get a couple gallons of it pretty cheap and put it all in a bucket and let it soak for a while.
 
I had the same idea, glad I'm not the only one that thought of letting it soak in a bucket for awhile.
 
An 80 pontiac would be useing the chevy engine so you should be fine.
Basicaly there are 3 differnt CFMs on these carbs 650 750 and 795. I would guess about 99% of the ones you will find are the 750. The 650's are alot older and less common. The 795(800 in some peoples minds) was available on big block trucks and all corvettes with a carb. The thing about q-jets is they can be built almost anyway you want as long as you know the right combination of parts. But that alot more detailed than a first timer wants to get into. the 80 pontiac most likely has the 750 witch will be fine under about 500 horse power.

Some things to be sure and check are the bushings where the butterfly shaft goes through the side of the carb. if its loose find another carb cuz you wont like trying to replace them.

The casting plugs I mentioned b4.

And be sure you adjust your float corectly.

Balzer
 
OOPS one more thing often overlooked is the secondary jets. they arnt like the primary jets. Rather they are tiny brass washers pressed in at the bottom. Use an awl to pop them out and get new ones. Unfortunatly the only place I know where to get them is a GM dealership. To instal them you have to find something thats just slightly smaller than the outside rim, place it in its groove and use the above mentioned idem and your hand to tap it in.
DO NOT use an awl to install them or anything that fits in the hole the hole is the inportant part. Most of them I have changed are egg shaped from the wear.

Best of all heres a pic even if it is a crappy pic.

Balzer

vc-590f.jpg
 
You are being a big help, I really appreciate it.:bow: If I can't snag that carb cheap I'll be rebuilding mine. It fires up and everything I just believe there is something stuck causing it to idle at 2500-3000 rpm.
 
any of them are fine to rebuild as long as they are not the computer controlled version you can tell this by an electrical plug in this area pictured below. If it has an electrical plug in that area throw it away. They are rebuildable but just flat out are not worth the time.

Balzer

vc-582f.jpg
 
majority were 750 with a few of them being 800s but I dont really know how to tell.
Click to expand...

and the cfm number will probably never matter to you, since a semi-stock sbc doesn't need 795 or even 750 cfm of air. where you might notice a difference is in the jetting and rods.

and if you're idling that high, and the throttle isn't stuck open, start looking for vac leaks or timing problems.
 
OK, some quick clarification.

Q-jets are either 750 or 795 (800, whatever) CFM. 800's are much more common later on, 305 trucks got 800's exclusively from what I've seen, while the Monte SS's with 305's didn't, go figure. Oldsmobiles with 307's typically got 800's as well. The CFM difference is on the primary side, my *speculation* is that they were going for more torque down low, which is why you see many more 800's later on with the smaller engines. You do not see very many 800's from the 70's, nowhere near what you do in the 80's.

Electrical plug that confirms it's a CCC (computer) Q-jet is on the drivers side of the carb, TPS. Passenger side plug on carb does NOT mean it is computer controlled, because that can be a dual capacity solenoid and/or one other piece of something I can't think of. :) I agree though, I wouldn't mess with any of those, it's not something you NEED, and does complicate the rebuild kit, and probably drives up cost.

What year did the Pontiac 301 die? 1981? I'd make sure before purchase that it IS the chevy pattern, and not a CCC model or 301 as mentioned. Chev difference is mainly going to be the fuel inlet (believe Pontiac was like Olds, straight in, not from the side like Chev someone can correct me that knows Pontiacs) but also important is the choke. You need the choke style to match your intake. If mechanical, it has to, or you will end up trying to swap parts around, which is not always easy, OR go with the electric choke, which is very pricey to fix if it's bad.

I don't think I've ever even looked closely at the secondary throttle jets, that's a good tip. I've certainly seen secondary rods with rings worn in them.
 
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