Rescue Rogers

Step 1. Make sure you have a carb that is specific to your application and in good shape. I have a 68 and I found an unmolested 69 divorce choke carb that had good coloring, nothing was seized and all the parts were there.

step 2. Email Lars and set up an appointment and send it to the PRO for excellent repair and tuning.

step 3. Pay the man what ever he wants, he is completely worth every cent.

step 4. Install your awesome Quadrajet and go test it out. He warned me that he couldnt do a WOT test under load so I was prepared for that

step 5 Do minor tuning to dial it in and get a gigantic grin when that quadrajet 4 barrel "kick in" roar gets louder than your sidepipes.



But seriously, I had an Edelbrock that I had dialed in with an AFR gauge and I had a big dead spot under hard acceleration out of the lights or after WOT down shifts. Everything else was easy to adjust and setup, it just had a dead spot that I could not adjust out. I kept hearing about how the quadrajet was a much better design of the air valve style 4 barrel carbs (like the carter design) and I remember the big 4 barrrel roar as a kid so I decided to go to the quadrajet. I did find a 69 QJ from a guy that had it on a chevelle and he must have done some tuning as I had to straighten some linkage and bent stops before sending it to Lars and Lars did have to replace rods and jets. Lars pointed a few things out and what to expect so I knew that it may need tweaking when I got it but I really only needed to do 1 thing.

The 1 thing isnt really talked alot by anyone as a big solution and I did find a small reference to it in one of Lars tuning papers. I wish it was more prominent like a tuning tip
My carb would have a dead spot like I just turned the volume of a loud stereo to mute for a second, then back to full blown gonzo when the carb recovered. My AFR gauge would go from 12 to full clockwise past 17 to full lean, then fly back and the car would jump like a cat after I stepped on the cats tail. This happened if i down shifted or was at a low RPM in a low gear and partial throttle and THEN would stab it to WOT in a snap of a finger. Then came the silence, the hesitating silence, then the explosive roar as the carb recovered. I thought it could be the distributer not getting to 36* all in fast enough.

IF I had the same driving situation and instead went to WOT over a second or 2 the carb wouldnt lean out and I could get the 4 barrels in with out the flat spot. I realized this was the Air Valve slamming open as the engine just gulped in a boat load of Air all at once, but the spring pressure of the air valve was high enough that it wasnt bouncing the air valve enough to cause a big bog. It was just openning a hair too fast. So this evenning I grabbed a small allen wrench and a small screwdriver and holding the air valve spring screw in its current position I loosened the allen set screw. Once the screw was free I adjusted it an 1/8 of a turn clockwise and tightned it up. I took it for a short ride, stabbed the throttle, noted the result and pulled over. I did this about 4 times and after the second time i noticed a slight decrease in the flat spot. By the forth adjustment the flat spot was gone if I down shifted and flattened the pedal. If i was in 3rd at a higher speed and just flattened it it would increase speed with a barely noticable stutter.

I hope that anyone with a quadrajet would seek Lars guidance and knowledge in getting their Rochester straightened out and I hope my little adjustment story will help someone get that fuel injection feel if they experience that minor dead spot on hard acceleration. Its Such a great carb that I have a second one I'm going to try and rebuild myself just for the experience of rebuilding it. Then I will probably send it to Lars to straighten out the mess I make of it.

The only problem I have now is unrelated to any rebuilding. Its the gas in the carb boiling off if I let it sit overnight after a good long drive. My Edelbrock did the same thing and was mostly solved with the wood spacer. I have the 1 inch spacer under the Rochester and still have a long term boiling issue.The current solution is to leave the hood up and the air cleaner off so it doesnt create a little heat sink and trap the heat around the carb. Last night I did this little experiment and it started a bit easier after pumping the carb, letting it spin a few times, let the starter rest then crank again. So it is a heat problem and with a 1 inch spacer there isnt much more I think I can do about that. If I just spray some starting fluid in it, it fires right up. My last 2 fill ups were with Sunoco 93. I may try a different brand and see if thats a solution. Letting it sit for hours at a car show doesnt create any starting problems at all.

And I did find a remote electric divorced choke that I had to slightly mod to get it to fit and rotate in the right direction to get the choke to close. Its working pretty good right now. When I get a video of the car running I'll add it here

speedreed8

Milan454

So....how much?

Rescue Rogers

how much what?

mobird

I can definitely vouch for Lars helpfulness. I'm more of a DIY guy (out of necessity due to lack of money to spend on this car) so I have been tuning my quadrajet myself. Lars was very helpful over email and got me on the right track, and I've never heard someone complain about a Lars tuned Quadrajet!

I will say that my Qjet runs the best it's ever run now after buying Cliff Ruggles book and making some of his recommended modifications. If you are really wanting to learn to tune your Qjet yourself, my biggest recommendation would be to get a cheap wideband 02 sensor (I am using the AEM UEGO) and Cliff Ruggles book. I can't tell you how much help it is to be able to see the A/F ratio at every RPM and throttle position so you can know WHAT you need to tune.

JasonAndrew

I think you would have better luck with a Holley carb.

Milan454

how much did it cost for the carb rebuild?

Rescue Rogers

It was $250 for missing or incorrect parts, the rebuild kit and labor. Well worth the price for a nearly plug and play carb. I really just put it on and fired it up and it ran great. The hesitation was something I had to determine was on my end before asking Lars if it was something he could help me figure out. I had a bad fuel pump that I had to replace and my AFR gauge was telling me it was going lean when I floored it rapidly. I like to figure stuff out myself and if I couldnt, I know Lars would have easily been able to tell me what was up with the info I had.

Rescue Rogers

I have Cliffs book as well and the same AFR gauge. The gauge is why I knew it was going lean. I wanted to figure this out as best I could before bugging Lars and replacing the fuel pump narrowed down my possibilities. If this hadnt worked I was going to look a the distributor since the problem was only at instant acceleration to WOT and not a controlled acelleration to WOT. I also have a second carb I'm going rebuild myself and tune to see if I can do as good a job. Most likely not, but if I screw it up Im hoping he can make it right.

I've had Holleys in the past and they are more of a pain to tune than Edelbrocks since it has to be taken apart to replace the jets although I didnt have an AFR gauge back then to tell me which way to go.

Hamerdown

Give me a Holley 4150 any day...I know those like the back of my hand and very easy to tune.

Rescue Rogers

We all have our favorites and our preferences. I 'm really happy with the Rochester, cant say any other carb, set up correctly, would be any better other going to fuel injection (which maybe in my future plans) something similar to this for a SBC https://www.ebay.com/itm/Small-Block...oAAOSw~xlawE-W

TedH

Lars-rebuilt over 15 years ago and still going strong. Other than 'touching' the carb when I may remove it to work on the top-end, the carb hasn't required any adjustment since.