I bought some Nailhead stuff from interstate and when it got here this is some of it. As you can see not only did I get an intake manifold complete with Doc treatment, but a Quadrajet manifold as well !! I would never have believed a Q manifold could be secured in this country. So now what do I do. I was all set to use a new Holley square bore carb that I have. I have good reports regarding the Q carb, but a Buick specific one is not easy to come by here. Question is --- do I need one ? The engine is going into my street rod project so probably doesn't matter ? I can get a Quadrajet easy enough, but most are set up for local engines or 350 Chev and most are worn out by now. A complete rebuild is expensive. I don't know what trouble I have to go to in regard to jets / metering etc. for the Nailhead. So do I just go with the Holley on Doc manifold or go the extra effort / $$ to Quadrajet ? Engine will be stock.
I've liked and added the '66 Q-jet intake and carb to other nailheads previously running the AFB or 4GC. You will need to research a bit as the linkage from a number of later q-jets will interfere in operation with the intake itself. Sometimes, mix and match of the different carb sections gets you there if you don't source the actual Buick '66 Q-jet with the the integral choke-good luck.
If you decide Quadrajet, I could build one for you and ship it down there. Have shipped many your direction. The baseplate is wider on that early intake, so a late 69 or newer quadrajet would need an adapter to cover the intake properly.
Very rare manifold, dual plane mod it like this <input tabindex="1" title="Asset Usage" class="asset_attach_usage" id="upload_asset_usage_244455" style="display: none;" type="button" value="?"> <input tabindex="1" title="Delete" class="asset_attach_delete" id="upload_asset_delete_244455" style="display: none;" type="button" value="X">
My experience with the Q-jet on a Nailhead is kind of bittersweet. (1966 401, recently rebuilt to essentially stock specs) I found and bought an original set up, had the carb completely stripped and rebuilt for a small fortune. It looked like new. It worked "ok" for a little while, and then it started to run stupid. Now it runs like there's a huge vacuum leak happening. Have no idea what's going on as of yet. The problem with the early Q-jets is that the diaphragm for the secondary upper butterflies was cast in the body. Once the diaphragm quits the carb is more or less junk, there's no way of taking it apart. Another popular problem with Q-jets is well-plug leakage; a lot of rebuilders pack the cavity full of epoxy and hope it holds. One backfire and that's over too. So now until I get the Q-jet bugs worked out, I'm swapping the AFB back on. Try to find a 67 model Q-jet; the diaphragm is divorced like the later ones but the base plate is the same width. Look it over very carefully, loose throttle shafts and burnt well plugs can cost you. The base should be pit free too. Carter actually jobber-built some Q-jets in 67, those are the ones to get, they're the most like the 68 and up series which are much better than the early lot. Also; I'm not sure whether the stock AFB style linkage is useable on the Q-jet. I just reset mine and I lost the use of the secondaries. It seems that there might be some differences between the two and it's just not a matter of screwing out the linkages to fit.
carmantx Mark ---- is there a specific casting number for the pre-69 carbs ? Snake, what carb would you use with that modification, still a quadrajet ?
Besides Mark, TechG8 has been building hybrid M4M carbs for Nailheads - he built my base plate and if I remember correctly it was a bolt on two tenths. I think he just got a SP linkage throttle arm in stock for the next conversion, so PM him for prices and availability. The 76-79 M4M works great as it has 800 CFM, a better casting, adjustable part throttle and other generational improvements. We just did a Everyday Performance 750 to 800 CFM carb swap on my buddy's RAIII Trans Am, and found that the extra CFM was worth .2 tenths and about 4 MPH - sounds ridiculous, and the original carb may have had some issues but the car is bone stock with no other modifications and unopened motor, 70k miles and running 13.8's @ 104 from a prior 14.2 @ 100..Thats faster than they ran new, so Buicks arent the only cars that ran CFM's. So look for a 17059247 or 249, or any 76-79 Buick Q-Jet....I have a thread on here somewhere about my back to back race results, it's worth the effort. Keep us posted, and NICE FIND!
why is a q-jet better than a afb, because of cfm. the stock afb is 575 cfm and the stock q-jet was about 725 cfm. nailheads like big cfm carbs. if you put a bigger afb{edlebrock 750} on it will perform just as well as a q-jet. its about cfm does not matter if its a afb, q-jet or even a holley.
I agree with this statement in the terms of raw power. However, I feel that the Q-Jet is better suited for a cruiser over the Edlebrock or Holly just due to design. I don't have any raw numbers to personally back that up, but it is just my belief. But you are absolutely right that nailheads love cfm. I don't think you can ever give them too much cfm. Your restriction will be how much cfm your intake itself and the heads flow. But like said above, a Edlebrock 750 would work as well. I plan to use a Q-Jet on mine for now, will see what happens later if I change my mind when I hit the track later.
yes if you are looking for a little better gas mileage and can tune a q-jet. I would use what ever you have or what would hook up easier, point is don't worry about difference in performance. on a stock 401 nailhead I changed a stock afb to a 750 edel and a open air cleaner it was worth 2.5-3 tenths and pulled to 4800 rpms , the stock was all done at 4400 rpms
He's probably referring to the the AFB based series of square bore carbs they currently sell. They work just fine, and will bolt in in place of an AFB. The do not have a hot air choke (or at least the ones I've seen) so you might have to rig a manual or electric choke if you want to use one. I had one on my 71 when I bought it, and it worked just fine... The only spread bore design by Carter was the Thermoquad, and we dont have enough space here to discuss the Pros and Cons of those!
carmantx Mark ---- is there a specific casting number for the pre-69 carbs ? Snake, what carb would you use with that modification, still a quadrajet ?, it's a BBB 1972 quadrajet 800 cfm , just need to tweek the throttle linkage a bit and hook up the kick down
I second gsgtx, in the 750 cfm edelbrock statement.. Mine original afb Carter was begining to run poorly, so stuck a 750 edelbrock with manual choke on, and out the box it ran much better and stronger, and got rid of the bugs.. Aussie, mine's a #1407.. My sparkplug color is spot on, out the box.. It's on a 401" that's stock other than 2,5" exhaust, recurved dist and open filter.. Car is an 65 Electra..
I run a 1411 Edelbrock. It was way rich out of the box for my stock 64 401 and my elevation of 2900 feet. Search my threads for the tuning specs I came to. Performance is great. I get about 16 mpg highway and 10 city. Sell the qjet manifold to the racers and use the $$$ to tune your Edelbrock.:beer
Isn't there somerhing about the electric and manual choke carbs is different jetted? I live at sea level, so that and probely the different jetting makes my #1407 work perfect..
