cfm carb for Buick 350...places sell 600 and 650...is that enough?

I stand by my original statements. Disregard Sean, he must have hit his head on something at work today.

We still love ya Sean.

To the OP: you can't cram more CFM through an intake runner that flows less CFM unless you force it (boost).

The REAL reason the Buick 350 'needs' a larger carb is that it benefits from it because the intake velocity is already good with the runner design. It's not a flaw, it's a feature. It's designed to perform better at lower RPMs while still being capable of turning higher RPMs (This is why the Buick 350 has such a wide power band). Even so, it will only draw so many CFMs at any given RPM, and while it is technically true it will 'use' more CFM at higher RPMs, the engine as a whole won't benefit because the cam has long since died off at lower RPMs.

This can give the illusion that the engine 'needs' the bigger carb. The power will trail off more slowly as the Qjet opens up further to accommodate the higher RPMs, so it doesn't feel like it's falling on its face so much, even though the camshaft has long since died.

The stock intake has a 4 hole spacer built in to it. The TA intake doesn't have this, and has larger plenum and runners. The smaller carb will help to compensate for this by having the larger plenum draw harder on it, and with the spacer I showed you, will enhance this effect further.

Circle track racers use this trick who are limited to 2 barrel carbs. The spacer design creates more draw on the bottom of the carb like a venturi, making the carb seem larger than it is, and still maintaining good charge velocity.

Jim W. built a Buick 350 with ported stage 1 heads, TA 212 cam, and big headers and used a 750 Qjet. He said the carb wasn't taxed enough to warrant putting on an 800. This engine would flow waaay better than a bone stock 350. So you be the judge. Reread what I said in earlier posts.

You can still opt for the Qjet too, but I would get a 4 hole spacer for that as well to aid in charge mixture.

The secondary flaps (on the Qjet) will hang down into the intake plenum without it. This will cause drag as the charge moves back and forth with intake pulses.

But whatever, you know? People will blow me off as being full of bs, like I just pulled this info out of thin air or something. Just because an engine has a 750 or 800 Qjet on it doesn't mean it's flowing the full CFM. GM put Qjets on v6's...

I'm just trying to help. Listen to whomever you will.

Wish you all the best.

---------- Post added at 12:22 AM ---------- Previous post was at 12:21 AM ----------

Ok Sean. I believe you. You have your reasons and I have mine. You don't have to explain anything.

Have a drink and relax.

 

to confuse you more, t/a recomends a holley with its intake. it does work. it is right, don't know, never tried it and i have all the parts to do it. i built my own single plane and ended up using a holley 600. i tried a bunch of bigger carbs but they didnt work as well. actually terrible. and then again, nobody has an engine built like mine. if i were you, stay with the qjet.

 

Hmm what about if I bought GS ram air parts, air cleaner setup...cant use them? I have a fiberglass GS hood.

---------- Post added at 08:34 AM ---------- Previous post was at 08:30 AM ----------

I already spent well over 400 bucks getting this Qjet built by Cliffs high performance. Sure it idles and cruises well, thats about it. 14mpg I wasnt impressed with.

---------- Post added at 08:39 AM ---------- Previous post was at 08:34 AM ----------

It is interesting. I emailed TA and asked, they recommended the Edelbrock 650, however they dont seem to list one for sale, only a 600 and a 750.

 

Mpgs what's that??? I'd you have any kinks cam other than stock Mpgs shouldn't be considered as you opted for more power

 

Well if MPG numbers are your concern with your Qjet, you might have mentioned that up front. 14 doesn't mean much if you don't tell us where, how, and how fast you drive typically. If you get into the secondaries a lot with the Qjet, you're going to go thru a lot of gas. If you drive mostly around town, you are going to burn a lot of gas. Accelerate hard at stops... down go the mpg's, regardless of the carb.

Owning a driving an old V8 car doesn't typically mix well with being concerned about your mileage.

---------- Post added at 10:28 AM ---------- Previous post was at 10:24 AM ----------

 

nice discussion. lots of good points for different options. My last 2 cents on the matter are for the edlebrock. Cant speak for the 350 because Im not currently using one on a 350 but I use an edlebrock 850 on my mildly built 455 (actually its a 462) and I am quite sure I am not running out of steam at full throttle. It pulls hard all the way up to burying the speedo needle and thats not too shabby for a 4000 pound car with no race goodies and a bone stock automatic that chirps ALL gears from a dead stop when you mash the go pedal. Call it what you will, but I call it Gitting R done! :laugh::3gears:

 

Check to see if your gaskets are sealing properly.

If you already spent that much on your Qjet, keep it and get the 4 hole 1" phenolic plastic spacer from Mr. Gasket.

Your mpg shouldn't have gone down that much from a 2 barrel switch. In fact, it should have improved.


TA says their intake improves mileage, but well...we know how much the other info on it is true, so who knows.

If you didn't mess with anything else and just bolted on the exhaust and intake, I'd be checking for vacuum leaks first and foremost. Start with the carb gaskets then check the intake.

Which gaskets did you use for the intake? How did you torque the intake down?

---------- Post added at 02:22 PM ---------- Previous post was at 02:12 PM ----------

The reason the smaller carb works is plenum and velocity. A larger plenum (such as that found on the TA intake) will draw harder on the smaller carb, making it act larger than it is, plus keep velocity up.

This is why it works. Put a larger carb on it, and it'll be bog city because velocity takes a nose dive. It's also why TA recommends square bore carbs, since the velocity will remain equal on each barrel.

Stock intake doesn't behave like the TA intake, and doing a direct swapover comparison using the same carb gives results that won't differ by much.

People don't seem to realize it's all about combination and matching parts up with each other so the engine performs as a unit.

:TU:

---------- Post added at 02:31 PM ---------- Previous post was at 02:22 PM ----------

I seem to remember reading about a 1" spacer, the TA intake, and a GS hood. Seems it will fit as long as you cut down the foam rubber insulators on the ram air. I would be checking and measuring before doing any permanent modifications to anything.

Get a 4 hole 1" spacer...

Your velocity will improve and so will your power and gas mileage. Make certain it seals properly and that the divider on the intake is sealed up. For a stock or mild engine, this is imperative to retaining low-mid range power. If you open the plenum up some, it will move the power band higher, losing low end and gaining top end. For a stock or mid cam, this is a self-defeating scenario.

 

Checking for vacuum leaks, I know it seems like a simple question, but if I have no symptoms like high idle, how would I check?

thanks

 

To check for vacuum leaks:

First, put something around the distributor to shield it so no gasses get under it and blow your distributor cap to smitherines and scare you out of your skin.

Second, locate a source of flammable gas. This could be acetylene, propane or even a can of starter fluid. It'll be easier with the acetylene or propane since you can adjust the nozzle where it's just barely trickling out. With the engine idling, move the nozzle around the intake runners where they meet up to the head or anywhere else you might suspect a leak. Move it around the base of the carb where the gasket is.

If the engine revs up at all, notice where the nozzle was when it increased RPM, and you have located your leak.


Be VERY careful using this method. Stay clear of the fan belts and blade! Don't wear extra clothing, baggy clothing, or if you have long hair (like me) ponytail that **** up and keep it out of the way.


If the leak is on the underside of the intake, I'm not sure how you'd locate that...ask yourself which gaskets did you use on the intake, and were the intake bolts sequentially tightened?


Does the engine idle fine and run off the primaries with no issues? Is your only issue when you open the secondaries?

A 4 hole 1" spacer on that Qjet will resolve velocity issues and eliminate the secondary flaps from reaching inside the plenum.

 

If its a street car little racing call everyday performance and get a qjet or you will just be wasting gas & $ I have a holly 600 ,a edelbrock 750 and 850 and still got better performance and mileage with the qjet with bigger secondary rods and the rear flap adjusted to light Vacuum

 

I'm reading that a carb spacer only helps a single plane manifold. Since the TA Stage 1 is Dual plane I will not see a benefit?

 

do not use a flammable gas . any stray spark will cause a fire. use wd40 or squirt bottle of soapy water. if it seals the leak it will raise rpms
yes a spacer does work on a dual plane buick 350 intake. but I don't think that's gonna solve your problem. I suggest proper tuning and electronic ignition upgrade with a new coil.

 

New coil is a possibility, an MSD maybe youd recommend? I currently haver a breakerlesss igniton under the stock dist cap.
What kind of gains have you seen from a 1 inch spacer on the 350 Stage 1 intake? Low end power?

 

Mostly upper end power gains mostly and minimal at best its not a big power enhancer .msd is good .I have a msd dist with a 6a box and blaster 2 coil .

 

Not all carb spacers are equal. Open will be good for upper end; 4 hole is low-mid range. Some people see substantial power gains, others not so much. It really depends on what your combination is. Most consider spacers to be a tuning tool.

On the TA intake, the plenum is a little larger than stock and is wide open on each side of the divider, and so for lower RPM cams a 4 hole spacer is better served to maintain good velocity as it enters into the plenum. The stock intake has a small 'spacer' already built into it, and is usually why it performs better for stock-moderate engines vs the TA intake on untouched heads.

The trick here would be to mimick the stock intake by adding a 4 hole spacer to improve low-mid range. Whether square bore or spread bore, a 1" 4 hole spacer would work better than no spacer at all, especially for a stock cam.

The more expensive spacers are usually aluminum and have flared openings on the bottom to aid in transitory pulses across the plenum. A regular 4 hole spacer will still be better than none, even without the flares. Flares also serve as a venturi of sorts under the carb, creating a harder draw on the carb, particularly with larger plenum beneath it, such as is the case with the TA intake. In this scenario, a 600 CFM square bore carb with that Hamburger spacer I listed would perform very well...surprisingly well, in fact. It will cost some money, though.

Mr. Gasket makes a phenolic plastic 4 hole 1" spacer fo cheap...around 30 bucks, and is good up to 300* fahrenheit. Can get one for either a Q-jet or square bore.



BTW...thanks for the tip on the 'no flammable gas for vacuum leak testing'...makes sense and is way safer! :grin:


Edit: I feel compelled to specify that the Hamburger spacer must be solid in the divider, and not the 'combo' spacer that flares out across the divider. For a stock cam, it would be imperative for the divider to remain in tact and well sealed.

 

I have found 4 holers, and adapters from spread bore to square bore, but none that are tapered ("flared"?). Tapered ones cannot meet the divider and keep it divided.. correct? The tapered Hamburger one you recommend and all like it seem to only be spacers, how would I also adapt square to spread bore?

I also found this, and it seems to be a 1 inch.


http://compare.ebay.com/like/400555300883?_lwgsi=y&ltyp=AllFixedPriceItemTypes&var=sbar

 

Ah, the V8Buick carb warsou:

Even when the problem is a Q-jet built by Cliff, the answer is still a Q-jet built by Cliff.:laugh: