Too Slow/Q-Jet question

[Doug Hoven]

Q-jets aren't really "cut and dry" across the board. Some carbs are good with a little work, and others are slow no matter how much effort is thrown at them. If the money isn't there to send a carb out to be built by one of the "gurus," then I would suggest buying the Quadrajet book by Cliff Ruggles. I surprised myself with how much I was able to accomplish with some basic mods to a bone stock Q-Jet. I believe what was meant by a "fast throttle plate" means the linkage was made to open the primaries and secondaries at the same time, unlike the stock progressive linkage that opens the primaries a decent amount first before opening the secondaries. The 1-1 linkage carbs tend to not drive around as well, but some swear by them being faster. As far as tuning goes, the car will tell you what it likes and doesn't like. MSDs can cause plugs to look good even when things aren't so good. I would suggest taking some "swings" at jetting, rods, and trying a few different hangers if you have some. Even if what you already have ends up being the best, at least you'll learn something.

[Mike Pearson]

Originally Posted by JP1738

Could not answer any of these question right now. I only had it apart long enough to replace the needle/seat and float. Set the float up best I could based on resources I found online. Is there a good resource on looking at what I have and determining what's in it? I'd be happy to take it apart and measure everything just so I could have a baseline starting point. I just worry about taking it apart so far I can't put it back together. Granted, I suppose that's about the only way to learn how.

What is a "fast" throttle plate? Also have not messed with the air flap but I know that it does open at WOT, just not sure how much or how fast.

If you come to Orlando I will be there. I wound glad to take a look at what you have. I can show you what a fast throttle plate is. And how it works. It is a linkage modification that brings the secondary in faster. You want the secondary and air flap to open as quickly as possible with out getting a bog. Sound like your carb is basically a stock Q jet. Even if you don’t bring the car come out and we can meet and talk

[JP1738]

Originally Posted by Mike Pearson

If you come to Orlando I will be there. I wound glad to take a look at what you have. I can show you what a fast throttle plate is. And how it works. It is a linkage modification that brings the secondary in faster. You want the secondary and air flap to open as quickly as possible with out getting a bog. Sound like your carb is basically a stock Q jet. Even if you don’t bring the car come out and we can meet and talk

As much as I think it is ill-advised, knowing I could get some help or expertise there would make it worth it. I have been planning on coming all winter so I'll probably bring it just to get a grade point and participate. I'll link up with you when I get there. Shoot me a PM if you don't mind.

[Mark Yacavone]

Don't really need to speed up secondary opening if you are two stepping it off the line.
I don't think we know that yet, either.

[JP1738]

Originally Posted by Mark Yacavone

Where are you? Division 1 ?
Mexico?
If we knew then maybe we could recommend someone that could to help you at the (1/4 mile) track.
Who was the previous owner of your car?
Who built your 350 trans?
Does it have a 2.74 low gear?
What rear gear?
What rear tire?
Where's the other tire and brake?

D2, and don't mind the ambiguous profile. I race out of Charlotte, NC and hope to go to the Darlington 1/4 mile test next Saturday.

The car has changed hands multiple times since it last ran, best I can tell it last went down the drag strip in 2015 or so. I do not know who last ran it. No idea on TH350 builder or first gear, but I know it and the converter came out from behind another 305 of similar combo so I'm 90% sure its 2.74 first gear.

5.38 rear gear on a Hoosier 30x9 C06 radial.

If you need any more info please send me a PM, I don't want to hash every minute detail of the car out and make the entire forum listen, but I do genuinely appreciate all the people who have reached out or chimed in!

[MR DERBY CITY]

Just gonna give it to you straight …. Just because your car runs close to the 1/8 mile index DOES not mean it will run close to the 1/4 mile index AND have you weighed the car yet ??? Number two ..:: stockers are all about RING SEAL .. just remember that. … Cheers…..

[JP1738]

Originally Posted by Mark Yacavone

Don't really need to speed up secondary opening if you are two stepping it off the line.
I don't think we know that yet, either.

Oh yeah, sorry. I am not using a 2-step at this time. I could switch to one if you thought that might help, but I've heard it's slower to use one.

[JP1738]

Originally Posted by MR DERBY CITY

Just gonna give it to you straight …. Just because your car runs close to the 1/8 mile index DOES not mean it will run close to the 1/4 mile index AND have you weighed the car yet ??? Number two ..:: stockers are all about RING SEAL .. just remember that. … Cheers…..

I have the car at race weight. Weighted class is N/SA and for my combo according to class racer info that's 3534 with me in it. Currently have it at 3560 with my 4 corner scales.

Mark Lewis put the engine together for me, I think he did a great job with what he had and I trust the rings are sealing properly. I haven't noticed any extra blow-by, the valve cover breather has 0 signs of oil comin out of it after 4 1/8 mile passes.

Also, I understand that this car will not backhalf and pick up time in the 1/4. I figured I'd have to go at least .10 to .15 under the 1/8 mile index to get under the 1/4 mile 13.00 index for N/SA

[JP1738]

Originally Posted by Doug Hoven

Q-jets aren't really "cut and dry" across the board. Some carbs are good with a little work, and others are slow no matter how much effort is thrown at them. If the money isn't there to send a carb out to be built by one of the "gurus," then I would suggest buying the Quadrajet book by Cliff Ruggles. I surprised myself with how much I was able to accomplish with some basic mods to a bone stock Q-Jet. I believe what was meant by a "fast throttle plate" means the linkage was made to open the primaries and secondaries at the same time, unlike the stock progressive linkage that opens the primaries a decent amount first before opening the secondaries. The 1-1 linkage carbs tend to not drive around as well, but some swear by them being faster. As far as tuning goes, the car will tell you what it likes and doesn't like. MSDs can cause plugs to look good even when things aren't so good. I would suggest taking some "swings" at jetting, rods, and trying a few different hangers if you have some. Even if what you already have ends up being the best, at least you'll learn something.

I really like this attitude. I'm absolutely not above trying to make changes. Like you said, at the very least I might learn something. I do not have any extra hangers or rods to try though, do you know where I can get more components to try?

[Doug Hoven]

Originally Posted by JP1738

I really like this attitude. I'm absolutely not above trying to make changes. Like you said, at the very least I might learn something. I do not have any extra hangers or rods to try though, do you know where I can get more components to try?

Apart from asking around the racing community, there are a few places to buy qjet parts. I bought primary jets, secondary rods, and needle and seats through jegs, with the brand being "JET Performance." Ebay is also a good resource for hangers, jets, and rods. Something I've seen done is if you don't use primary rods, you can screw in Holley jets in place of the rochester jets. The threads are very close, but not identical. This is not advised if you ever want to try rochester jets and primary rods ever again. So far I've only ever 2 stepped with a qjet. If you ever decide to "chill down" your engine, make sure to try it first when it isn't important. Especially footbraking, qjets sometimes need a little different tuneup when trying to leave the line at very cold engine temps.