put a qjet on my car today, it runs horrible
05-24-2003, 12:43 PM
#1
Senior Member
Thread Starter
Join Date: May 2000
Location: Woodbridge NJ
Posts: 571
Likes: 0
Received 0 Likes
on
0 Posts
put a qjet on my car today, it runs horrible
I bought it off ebay and rebuilt it. Its my first rebuild but I dont think I screwed anything up. It starts fine, idles ok and all. When I give the throttle a nice crack (enough to open the secondaries) it stumbles, revs up then usually idles pretty high (2000-3500)even though the throttle spring pulls the linkage etc back to the idle adjustment screw. Its relatively smooth at idle, but stumbles off idle and the idle speed seems to vary by itself after I give it slight revs. It's a non-cc qjet btw, the idle mixture screws are out about 1 1/2 turns. Much more than that and it idles too high even with the idle adjustment screw turned out completely. BTW I dont have any vacuum leaks. Is this thing just screwed or something? Worn out internals, something warped, or am I a moron??
05-26-2003, 02:28 AM
#5
Senior Member
When I put a Q-jet on my car (JUST for ****s and giggles) it wouldn't let my motor idle!! LOL Needless to say I put my Holley back and wrote it off as a bad choice for a very healthy motor.
Trending Topics
05-26-2003, 03:53 PM
#8
Supreme Member
Join Date: Jan 2001
Location: Rock Hill, SC
Posts: 1,411
Likes: 0
Received 3 Likes
on
3 Posts
Car: 1999 Pontiac T/A Firehawk
Engine: ***'s Engine
Transmission: T56
I actually didn't look at the cam to start with, just the motor...
Depends on if those are advertised durations or @ 0.050"... I'd assume at 0.050 with that kind of lift. At any rate, it shouldn't be that hard to mod a Qjet to get it to idle on that motor if he can pull at least 5" of vacuum.
Getting it to work well everywhere else would be quite a challenge though
. I certainly don't think I'd recommend a Qjet for that motor.
Depends on if those are advertised durations or @ 0.050"... I'd assume at 0.050 with that kind of lift. At any rate, it shouldn't be that hard to mod a Qjet to get it to idle on that motor if he can pull at least 5" of vacuum.
Getting it to work well everywhere else would be quite a challenge though
. I certainly don't think I'd recommend a Qjet for that motor.
06-02-2003, 09:13 AM
#9
Senior Member
Well remind me to shoot myself if I ever put a 252/262 ADVERSTISED duration in my engine. I think even the LG4 cams have more then that! That'd definitely at .050 ... And yes, I'm sure the Q-Jet would have been okay if I actually bothered to try to make it run my engine, but I didn't.
06-03-2003, 10:41 AM
#10
Member
Join Date: Mar 2003
Location: Central Illiniois
Posts: 282
Likes: 0
Received 0 Likes
on
0 Posts
Car: 89 Formula 350
Engine: 409 nitrous' small block
Transmission: 700r4
Are you sure you have your vacuum advance hooked to the right port? I fixed a friends car that had almost exactly the same problem the other day, his problem was that he had the vacuum advance hooked up to regular vacuum instead of ported vacuum
.And check your timing, remember that a lot of ignition issues are misdiagnosed as carb problems.
Another thing that causes a similar affect is that the throttle lever may be hitting the stop, but your secondaries may be hanging slightly open. When you get the high idle grab the secondary lever and pull it forward, if the idle goes down, that's your problem. To fix this you need to tweek the secondary actuating rod a bit so that it hits the stop as well. It may require welding (Use JB Weld, regular welding can warp the carb if you're not real good) a tab or something on to gain the needed contact.
And I doubt that your this far off, but I saw a guy once get his PCV and charcoal canister hoses backwards, so his pcv was sucking air in through the canister, and man that b*stard ran funny.
If that's not it there are a hundred different things you could do. But I'd make sure about the vacuum leaks, because if the idle just keeps getting faster the more you turn the idle mixture up it would seem to indicate it's getting a lot of air from somewhere, you may need to drill out the idle passages because you're not getting enough fuel to feed the engine. Before you go drilling check the throttle shafts for play, they could be worn and leaking air past. Also check your baseplate for flatness, they get warped lots of times and won't seal up properly.
If all that checks out then you can think about drilling out the idle passages. You can of course drill out the hole for the idle screw, usually to around .095. Some later carbs have a restriction back in the idle circuit though that is a little harder to get to but may be necessary. Then you should be able to get a rich stumble out of the engine when you turn the idle screws out.
BTW a quadrajet can make a very fine performance carb, the problem is they're not set up that way out of teh box usually (unless you buy one from edelbrock or JeT) so they take some tuning. I've built 10 and eleven second street cars using quadrajets on built big blocks, and I got started using 'em because Joe Mondello told me then on an olds 455 he recommended them over holley's or edelbrocks. He warned me that it would be some work to get it dialed in, but I'd be happy when i did, and he was right. I even have built them for fords and dodges and got them to run great.
.And check your timing, remember that a lot of ignition issues are misdiagnosed as carb problems.Another thing that causes a similar affect is that the throttle lever may be hitting the stop, but your secondaries may be hanging slightly open. When you get the high idle grab the secondary lever and pull it forward, if the idle goes down, that's your problem. To fix this you need to tweek the secondary actuating rod a bit so that it hits the stop as well. It may require welding (Use JB Weld, regular welding can warp the carb if you're not real good) a tab or something on to gain the needed contact.
And I doubt that your this far off, but I saw a guy once get his PCV and charcoal canister hoses backwards, so his pcv was sucking air in through the canister, and man that b*stard ran funny.
If that's not it there are a hundred different things you could do. But I'd make sure about the vacuum leaks, because if the idle just keeps getting faster the more you turn the idle mixture up it would seem to indicate it's getting a lot of air from somewhere, you may need to drill out the idle passages because you're not getting enough fuel to feed the engine. Before you go drilling check the throttle shafts for play, they could be worn and leaking air past. Also check your baseplate for flatness, they get warped lots of times and won't seal up properly.
If all that checks out then you can think about drilling out the idle passages. You can of course drill out the hole for the idle screw, usually to around .095. Some later carbs have a restriction back in the idle circuit though that is a little harder to get to but may be necessary. Then you should be able to get a rich stumble out of the engine when you turn the idle screws out.
BTW a quadrajet can make a very fine performance carb, the problem is they're not set up that way out of teh box usually (unless you buy one from edelbrock or JeT) so they take some tuning. I've built 10 and eleven second street cars using quadrajets on built big blocks, and I got started using 'em because Joe Mondello told me then on an olds 455 he recommended them over holley's or edelbrocks. He warned me that it would be some work to get it dialed in, but I'd be happy when i did, and he was right. I even have built them for fords and dodges and got them to run great.
Thread
Thread Starter
Forum
Replies
Last Post
86IROC112
Engine/Drivetrain/Suspension Parts for Sale
4
08-17-2015 02:00 PM
