Quadrajet

summitXMK · May 10, 2001

I was wondering if anyone new where to get a good book about a quadrajet. I have one on my 78 blazer and I want to rebuild it. I am also missing some linkage around the outside. It won't open all the barrels, choke etc. Anway any info on a good book preferably with lots of pictures, would be great.

May 10, 2001

HP has a book on all Rochester carbs.

76BBSub · May 11, 2001

The book is by Doug Roe, and is published by HP books. It covers alot of stuff, but if you need choke stuff, well, it doesn't get that specific. The Haynes Carburetor manual sucks...really...I have both.

If you are missing parts it may not help much. All the parts may be there, but if it's not adjusted correctly that can cause the problems you mentioned.

Can you describe what you are experiencing, we may be able to help fix it without a bunch of new parts.

Jeff

summitXMK · May 11, 2001

Well to start out with it has been sitting in a field for the last 4 years. It is a quadrajet 4 barrel on a 400 small block. Right now it idles pretty high which I am sure I can fix. But I can't get the last two barrels to open no matter what. I figure some of the linkage is out of adjustment or missing. I was also going to try and fix the cruise control. I know that is missing some linkage. My plan was just to take an entire day and dismantle the thing and rebuild it. I did that once before in high school and it worked wonders. Of course right now I am getting darn good gas milage. I just sold my other truck to use as a down payment on a house so it was either the 78 blazer or the 67 chevelle to bring back to life. The chevelle would have been easier but the blazer is more fun. It is a convertible!!

May 11, 2001

If your secondaties are not opening, the mileage will be great. Kinda lacks power though. I've never had any luck with QJ's. But that is mostly because I won't take the time to learn them since Holley's are so simple.

76BBSub · May 12, 2001

The secondaries on a QJet are vacuum actuated, meaning that they open against spring tension when you are under a heavy load.

There are a couple of things to check...first, have someone hold the gas pedal to the floor with the engine NOT running. Push open the secondary butterfly and make sure that the lower throttle blades are opening mechanically.

Next, check the vacuum pull off. It is part of the choke system on the passenger side of the carb. When the choke is actuated the vacuum pull-off prevents the secondaries from opening. If you choke is misadjusted, which can cause the high idle you describe, it will also prevent the secondaries from opening.

Finally, there is a spring on the side of the secondary butterfly, passenger side I believe. The spring tension is adjusted with a screw, which you can see from the side of the carb. There's a small allen-head bolt that prevents the screw from turning. Loosen the allen-head bolt, then let the screw rotate itself to zero tension on the spring. Next, turn the screw about 1/2-3/4 turn, and tighten the locking allen screw. This is approximately the tension required to open the secondary butterfly normally. If it opens too soon, tighten the screw by 1/16-1/4 turn until it is right. If opens to late loosen the screw by the same amount.

Post here if you have problems, maybe I can help.

Jeff

summitXMK · May 15, 2001

Thanks I will try that as soons as I get a chance. I have to leave town this weekend so maybe the next? He I still have the seats for that suburban I don't know what kind of shape they are in I will look this weekend if your interested let me know. I forgot that I put them up in the roof of the shop at my dad's.

76BBSub · May 15, 2001

Let me know how it goes...alot of carb stuff is just tweak and drive it and then tweak it again...sometimes for several days. I've got my '76 dialed in so that one pump in the morning, turn the key and it fires up instantly. When hot, just turn the key once and go. But it took a week or two of slight adjustments and then trying it out.

On the Suburban stuff, my seats are pretty good, but I really could use a set of shoulder/lap belts if those are around. I bet they went to the scrap heap with the rest of the body, though.

summitXMK · June 11, 2001

I found the seat belts. I think that they are all there. They are green if that matters. I haven't gotten to the carb yet (work sucks) But I'm still getting good gas milage.