Chris Fowler

My q-jet apparently has problems. Possibly cracked internally. My mechanic said he can turn the jets all the way in and the car keep running.

so...it's looking like I've gotta get a new carb at some point.

What's recommended? Q-Jets are expensive. Are they even the best way to go?

Holley? Demon? Mechanic says Carter

Guess I'll start pricing...

This is on a 350 with performer intake. I'd like to upgrade to an RPM intake at some point, so I'll probably take height of the carb into account.

lars

Chris -
If the carb is not perfroming correctly for you, please feel free to send it back to me and I will correct it and cover shipping. Just let me know if I can help.

79MakoL82

I've heard nothing but good things about the Demon's I was going to send my Q-jet off to Lars for a re-build, but with all the posts lately, I'm starting to think of replacing mine now with a Demon. I think the Demon's are around $400. I was told the Q-jets give you a little better gas mileage.

Chris Fowler

Lars, is there really anything that can be done about this?

He said he's seen several rochesters do this...where they've got a crack allowing fuel and air through even when the jets are all the way closed.

Is he full of it?

He has been unable to tune it. The idle is a bit random. Sometimes it idles at 1000 and if you tap the gas it drops down to 600. Then if you hit the gas again it goes to 1000. Also really hard to start (always starts, just takes a while) and diesels once when you shut it off...

I asked if this was something that should have been noticed with a rebuild and he said no. You can't tell without putting it on an engine and trying to tune it...which is the one thing you said you couldn't do...

Joe Lucia

Chris-------


If emissions legality is an issue for you, then you're pretty much stuck with obtaining another unit like the one you have. The last GM SERVICE carburetor for your application, GM #17066425, is discontinued.

If emissions legality is NOT an issue for you, then I'd suggest going with the Edelbrock Q-Jet. When it's in good or NEW condition a Q-Jet will give better OVERALL performance for the street than any other carburetor.

lars

Chris -
If you can stand the down-time on the car, send the carb back to me. I haven't seen one with a crack in it yet, so I just have a hard time imagining that the carb is irrepairable. Also, send the base gaskets that you're using along with the carb, and I'll bolt the whole thing up to an engine and run it until I figure out where the problem is. I'd hate to see you fork out $400 - $500 for a carb if there is an easy fix to the one you have.

Chris Fowler

We don't have emissions testing here, so that's not a worry.

Last inspection the guy couldn't have looked close enough to tell what kinda carb was on there...

Chris Fowler

Well...I've got some time to figure out what I'm gonna do.

I can't afford to go out and buy a new carb at the moment.

I really don't want the downtime, but if it could save me money, it's a shot I might take...

I'll have to see how everything rolls around...

The Wanderer

Chris... Go with Lars ! He just did my carb & distributor and it is perfect !

BSeery

I will be selling the stock 4 BBL Q-Jet from my 1980 in October when I do a motor swap.
Let me know if you interested.

Chris Fowler

He's actually already rebuilt this one. ;)

I'll probably let him take another look at it in the coming weeks.

Chris Fowler

Depending on how this works out (if I send it off to lars and he can't fix it, etc...) I'll likely be very interested.

thanks! :D

The Wanderer

hummmm ... well either way, I hope you let Lars look at it. I know he will make it right, or at least see what really happened. He has a way of explaining the complicated in easy words.

Chris Fowler

Believe me, I want him to look at it.

I just hate the downtime. ;)

SteveG75

Chris,

I would definitely have Lars look at. Worst case, he can probably get a base from another carb and swap it if necessary. He did a great job on my carb.

Lars,

Car ran great from Denver to Newport (RI). Even with the new cam, got 19ish mpg on the highway. Even hit 20 once. Thanks for the excellent work. Did you ever publish that Q-jet tuning article. Got the geek data, just collecting info now.

Gerry

I remember hearing or reading someplace, that a lot of times the Qjet will still run with the jets screwed in all the way. Maybe your mechanic is a Holley fan?

Smokehouse69

I've seen Q-jets run with the idle mixture screws all the way in. This can happen when the idle speed screw is screwed down to the point that the carb is no longer operating in the idle circuit. It this is the case the car won't run worth a darned. It won't idle for beans since idle is entirely dependant fuel and air coming thru the primaries. I'm not a carb expert in the least, I've just experienced the same problem with my carb.
If Lars can't get it right, then it can't be fixed. Give him another chance.

Chris Fowler

Yeah...I've basically gotta find some time for downtime with the vette. I'll probably contact lars and find out when is best for him so I can minimize my downtime as much as possible.

I go nuts without my vette...been in the shop the last week working on a few things...I need to drive it for a bit before I can dismantle it again ;)

Chris Fowler

He was recommending the Edelbrock Carter carbs...might just be that he doesn't know Q-Jets very well. Which is why I'll go with a second opinion from lars before I do anything drastic.

lars

Chris -
I'll be more than glad to take a look at it any time you can get it back out to me. Once I get it, I'll put it "as-is" on one of my engines out here and verify that I can duplicate the problem. Then we can see what's going on with it and get it squared away. Just make sure you send it out with all of the gaskets that you're using on the base so I really am duplicating your exact setup when I run it. I'll re-imburse you for your shipping costs if you ship via USPS Priority mail, and I'll cover return charges. Just let me know...