Best carb for my 350?

[man]

I have a 1970 GS with the High Compression 350 that has some up grades such as ported heads, Thumper Cam .494/.480 lift, TA intake, Hooker headers, Stinger ignition with HEI.

I am having a hard time with Carbs on this engine, the Holley 750DP seems to be too much (can't jet it low enough to take the richness out) and the Q-JET is no where near enough. The performance of the Holley is out standing but it will burn your eyes out of your head it is so rich, (it is jetted in the low 60's in front and low 70's in rear) any lower and it will not run at all. Power valve is a 3.5 as Holley suggested (9.0 manifold vacuum at idle). I have tried a few other Holley's such as a 650CFM DP (suggested by Holley) and it ran but thats about it, a great power loss between it and the 750.

I need a suggestion as to what carb to try next because trial and error has got me beating my head against the wall.

[carmantx]

here is my .02 worth.
that 350 from buick had a 750 cfm quadrajet from the factory. i like qjets and howvthey perform, and build them all the time for buick folks. I run them on most my buicks, and they will work when built right. The 750 holley may be too small for you, and i think the rich problem at idle is something other than jetting. buicks flow a lot more air than a chevy 350, so the 600 cfm was an incorrect suggestion from them. That engine would handle a 1050 for racing. for street, I would run an 800 cfm quadrajet, built for your cam and work. or go to bigger holley type with power valve blocked and good metering blocks.

If you want an 800 cfm qjet built, let me know.

[man]

I located an early Buick 455 Q-Jet just need to get my hands on it, he says it is off of a 1970. Whats the charge to go through it?

[sabrerattler7]

Hey Texman, You can list me in the Quadraflood hater column, but I have an open mind. I've owned dozens of them on Chevy's and Rivi's and I've only had one that ran realy nice (better than from Detroit) after they rebased it in CA for my Big Block work truck. However that lasted all of six monthe before the float pounded out the float valve seat and it went back to flooding, hot start lock, and all the old tricks. I've never run one with a well regulated pressure regulatation which is one of the things I always suspected might be a problem. Many of the symptoms would be explained by gas pressure over powering the float valve.

So how do you fix that stuff, cause I've got boxes of the damn things laying around, some still charred from catching on fire.

[carmantx]

man, the 70 carb will be 750 cfm, and could work fine for your car with a few mods. I do this as a hobby, not for a living, so I charge $200 to work your carb. i use only the best parts, and build them right. Always using new parts inclunding primary choke pull off.

quads. the qjet cant take much fuel pressure. about 6 psi max. need to regulate down if it is higher than that. key is to get flow for the high horsepower apps, with high flow needle/seat, and sometimes, mods to the float hold down to allow more fuel in float bowl. good needle/seat is also critical. you dont get those from an off the shelf kit, and those will fail and not seal off. I have several of my qjets on 500 hp bbb and running well. we ran one on the red car, and dynoed at 525 hp, got 5 more hp with a 950 carb. same motor now is 633 hp, so we are running bigger carb now. but I have a qjet on my 462 in the convertible with mechanical fuel pump. no dyno time yet, but probably about 450 hp.

I like the streeabilty of the qjet with the smaller primary. and it will get best fuel economy with the performance when built right. If you have some buick carbs you would sell, I would be interested.

[sabrerattler7]

Where are the important numbers to identify a "Buick Quad" and what should I look for, (item you might want)?. Whats best way to maintain contact if I find something that might interest you.?

Interesting you should specify certain critical parts for specific quality, I just bought kits for Rochester until I gave up on the hope of success with those carbs.
What about bushing throttle shafts in the bodies?

Not to diss your work either, but running great for "flash dyno" or once down the strip is all different than 3 years commuter service. Do you get reliability for ordinary use also?

I have an old AC Delco diaphram pressure regulator/filter that we took off my Dad's 67- 396 Chevelle, it was a one owner car he bought in 69 and we never knew how it got there, but think it modulated the pressure and maybe pulse of the mechanical pump. Seems like it ran worse after we removed it at 100K rebuild. So maybe dealer or factory knew stuff that never made the papers.

[carmantx]

sabre, the carbs I build most, and like are coded 704xx4x. x's would indicate various numbers. the last 4 in this sequence indicates a buick carb. also has a straight fuel inlet.

I do always remove primary throttle shaft, drill out the base and install brass bushings.

I am not familiar with the rochester kits, but I havent found an over the counter kit that has good parts for long term success. I get parts put together for my spe ific needs with the components I need. It takes nearly $100 in parts alone to build one.

I mentioned the dyno for an hp number. a real number measured. We dyno for tuning only, or break in time. We build our cars to drive and race. After that dyno, the engine was in the red gsx, driven every day as an only vehicle, put on trailer friday and raced every other saturday for a season and half. My son drove it to school and work at the time. 20 miles to school for him, we live in the country.

Most qjet haters, are qjet haters. Its not the carb for everybody. But I like them.

[man]

The carb number he sent me is 17056244 which is far from a 1970 455 carb .

[carmantx]

yea, far from what you need in my opinion. That's a 76 carb. I have several good cores if you are interested, either 750 cfm or 800 cfm. Either should work well with your combination.

[sabrerattler7]

Thanks for carb feed back. Wished I lived next door I'd send you one for work up.

I'll look around when I get back to storage, couple months. Most of what I've got probably Chevy stuff.
Most stuff works if you know how to use it, just seems like there's so much sloppy work around and people ready to charge big bucks for second rate work,and knowledge.