I saw this kit that Gregg offered for the primarys, looks to be solid. http://quadrajetparts.com/rochester...for-jet-primary-throttle-shaft-516-p-286.html Thank you for clearing up the secondary bushing question, I had always wondered that. Well... for a few weeks anyway.
Yep, that's the ticket. I bought the same kit, and a whole lot of other stuff while I was at it. Got lots of q-jet goodies in the garage now, waiting to go into some of the cores I have ready. I have 2 complete 7027241 carbs, and I'm almost finished assembling the 3rd which is a 7027248 (newer needle/seat design). One step which is very important is to file off the staked screws holding the primary throttle blades to the shaft. Those screws need to be filed down all the way flush to the shaft before loosening/removing them. I tried removing them after I'd only filed down the staked ends, and one of them broke off in the shaft. It was impossible to get it out, even with drills & extractors. Luckily I was able to salvage the rest of the baseplate for parts.
Sounds like it's running out of fuel for some reason. After it stalls, if you work the throttle open and closed, do you see any fuel from the accelerator pump?
That did happen to me! Luckily greg offeres a tap for the primary shaft and told me what bit to use, some drilling and tapping then the shaft was fixed. Never thought about filing down the protruding bits to prevent that. Larry, I have verified the accelerator pump still functions after a stall. I havent checked every single time after a stall, but I have visually verified a few times that the accelerator pump still gives a nice stream. I only give 2 half-bumps of the throttle between startups, but that seems to be plenty to get the motor started again.
I know on my performer intake they include a plate that you have to use with edelbrock carbs to prevent a vac leak. It says that even though the intake accepts both square and spread bore carbs that if you don't use the plate it will cause all kinds of issues. Maybe switching between carbs means you need to use or stop using one of those plate.
Just got back in from the garage, put the edelbrock straight on the TA intake and it starts up just fine. Revs, idles, all around happy motor. Not so much with the Q-jet That was the thought of Mr Gessler as well, parts are on oder and I hope to kick this problem. I am glad I am trying this out, but if I ever had to do a Q-jet rebuild again I would send it out to one of the board members.
Glad you got it running okay, now, with the Edelbrock. The Q-Jet, when fixed up, will serve the motor well, but in its present state it seems to have lots o' vacuum leaks. The bushings will be a big step in the right direction.
That is good news, you give me hope Lemmy :TU: Now just wait till the parts arrive. I am hoping that the Q-jet will make a positive difference, the Edelbrock ran fine but with all of the recommendations from the board, I cant help but see what can happen.
I'd just stay with the E-brock. Many of the people who oppose them have little experience or are making money off the other carbs out there. If your engine runs good with it than leave it alone. It's a great carb and, as you've seen, very easy to deal with. Leave the Q-jet for those with the cash it takes to deal with it.
Now you have me scratching my head over my stalling issues. I'm going to throw on my edelbrock and see what happens
If things dont work out after this next round of parts and tinkering I am thinking I may have too, this adventure of mine has set me back quite a bit already.
The factory q-jet is application specific. Your engine combo is FAR from the factory set-up. Once you get the idle system up to par, it will idle perfectly in and out of gear. Edelbrock and Holley carburetors are "non-emission", so they have very generous idle fuel delivery set-ups. The idle system used on the q-jet is superior to either one of those designs, as most used a built-in idle air-bypass system. This is basically a controlled vacuum leak, to keep the throttle angle low, and off the main system at idle speeds. The Edelbrock Performer series carburetors are OK, easy to tune, and plenty of parts support. They are not very efficient, lacking sensitivity to the primary boosters, so you really have to be on your "game" to get them dialed in for fuel economy, without sacrificing throttle response and driveability. This statement holds true for all "high performance" carburetors with large primary bore area and small boosters. Doesn't mean they woln't work, but there is always comprimise to those designs. Huge airflow capabilities reduce "signal" to the boosters at low engine speeds, so they are never as efficient as spread bore designs. We don't use or recomend the Edelbrock Performer series carburetors here, simply because there is no adjustment whatsoever for the opening rate of the secondary airflap. If it works good on your set-up, you are a lottery winner. Most stumble/hesitate/bog when going quickly to full throttle. At least on cars with excellent power to weight ratios. The ones I've tested here are usually OK, if you have a small engine pushing around a really heavy car, and not a lot of gear or converter. My engine absolutely HATES them, and it is impossible to go quickly to full throttle in any gear, vehicles speed or engine rpm without some SERIOUS stumbling. The slower the engine rpms' and vehicle speed, the worse they "lay down". I can bolt the same carb on a 305 SBC engine in a pick-up truck with big tires and 3.08 gears, and the owner will love it so much he'll take it off the engine at night and sleep with it! In any case, the q-jet will work as good as or better than anything else, IF you take the time to set it up exactly for what you are doing. I would NOT install bushings on the secondary side of the throttle body, but I would make sure the huge throttle plates are well indexed and FULLY seated when closed, with some clearance in the linkage so they aren't tipped in slightly. Go after the idle tubes, idle down channel restrictions, and idle bypass air, when you use the right sizes, it will idle perfectly in and out of gear. It also helps to make sure the distributor is working like it's supposed to, and not adding any additional timing from the mechanical advance at idle speed. I see this a LOT, and it is difficult, if not near impossible to tune a carburetor when this is occurring.....Cliff
Thank you for the advise Cliff, waiting on drill bits to arrive and tweak those systems per the recipe. This next round will consist of: Primary bushing R&R 74 jets and .045 primary rod Idle tube, idle down channel, and idle bypass modifications. Keeping my fingers crossed! ray:
youre doing the right thing. Kudos to you for diving in and doing it.:TU: I ran a TA 294 cam in my 350 with a modded Qjet and it did just fine.
Thanks Ken! Does my plan sound pretty similar to what you ran on yours? I am excited to see what happes, but it is one steep learning curve :error: Thanks again to all who have helped me so far. The adventure is not over yet!
I think i had 73 jets and 44 rods , big idle tubes and channel, big idle mix screw holes, and some mods to the air bleeds. Secondary rods too Youre headed in the right direction, its a question of what your engine likes. start small and get bigger. Cliffs book and the Doug Roe book are invaluable resources for this kind of operation.
It worked!!!!! I did the above mentioned modifications, had to add idle bypass but everything seems to be working. Starts right up, idles very well, and it PULLS! It is dark outside and I blew a bulb in my temp gauge so I didn’t want to get too crazy, but cruising to the store and back was great. I have to comment on the bushing replacement. I was very intimidated to try for fear of messing up the carb, but Greg’s kit was very straight forward and very simple. I am glad I have my car back, and I can not believe that it worked. Thanks to all who helped! :beer
