Okay this might be a stupid question, and know it's in other topics, but I just wanna know one thing: can you take a plain 225 (that is currently 2bbl) and slap on a 4bbl carb and upper manifold? Do you really need to change any other internal engine parts?

Thanks


'68 Valiant 100 2dr 225/6 2bbl
'68 Valiant 100 4dr 273 2bbl
'69 Valiant Signet 2dr 225/6 1bbl
'69 Valiant 100 4dr 225/6 1bbl

Unqualified answers:

1) Yes

and 2) Yes

You could bolt two four barrels on a stock motor, if you wanted to (and made your own manifold! ), but you'd never get it to run worth a crap. You'd be adding supply potential without demand. The only way you can get by with that is forced induction (turbo or supercharge).

D/W

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If it ain't broke, fix it!

Tempest Sprint 6 cylinder: 230", QuadraJet 4 barrel 750 CFM.

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Are turbo's or supercharger's available for the /6?

If I remember correctly, the Pontiac sprint six was designed as a performance motor and had an overhead cam which was probably a bit hotter than the lil' ole' lady cam that comes stock in the /6. Also, I believe it was 250 c.i.d., not 230. Pontiac experts anywhere?

D/W

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If it ain't broke, fix it!

Yeah, a 4 barrel carb would be too much for the engine unless you reworked the head....it's just too much induction. I was thinking about adding a super six intake to my 76 Valiant, but even just the one barrel on it now seems more than adequate. I figure if I wanted to get more performance, I would've looked for a 318 car.

The OHC 6 was a John DeLorean idea that never got off the ground. The 326 V8 was a cheaper alternative.

quote: the "Sprint OHC-6" was outfitted with numerous factory performance upgrades. That included a high lift-longer duration cam, dual valve springs to control valve float up to the 6500 redline, 10.5 to 1 high compression head, lightweight harmonic balancer, dual exhaust manifolds (3 cyl. each to control exhaust pulses), high flow intake manifold, Rochester Quadrajet 4 barrel carb and a V8 clutch disc and pressure plate

It was a 230cid

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Yeah....Im the one who destroyed this rare, vintage automobile.....

It was both. They also had a lo-po version with a 1v carb and log style exhaust manifold. It was basically a chevy 6 banger with an overhead cam. For whats it worth, the Mercedes 6 banger used a Solex 4v spreadbore carb before they went to fuel injection. Both of these solutions had the secondaries facing the engine.

Even Frank has a q-jet on his \6. The primaries on the q-jet are about the same size as the BBDs, and the secondaries are vaccum controlled. On a stock \6 you may never open the secondaries. So I don't see a problem with running one.

Why is a four bbl.carb with vacumm secondarys to much for a stock slant and the Proline Fuel(which I have had installed on my 71 d100 with a STOCK 82 225 for almost 2 years with nary a problem) Dual weber setup is actually tuned for a stock slant?(I do have Clifford dual headers and an MSD6AL).The Proline is rated at 200cfm per carb and is not progressive(all four throttle blades open at the same time).
My truck idles nice and gets 13-14 around town and 15-16 hiway.
I do think that a better exaust would benefit a 4 bbl and the carb will have to be tuned for the application.You could tune a 390 cfm carb to run on a otherwise stock slant (including exaust)but the intake and exaust really needs to be upgraded together.
HyperValiant

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1960 Hyper-Pac Valiant(rolling test-bed)
1963 Valiant V2OO(Son's summer project,- he just turned 15 )
1972 Valiant 4dr(Daughter Kelly's repair in progress)
1974 Valiant (v8) daughter Kelly's work in progress

I've heard mixed opinions on putting a 4bbl on a stock slant six. Some say it's too much mixture for the engine to use..other people say it works wonders. But why bother spending all that money on the intake and carb if you're going to leave the rest of the motor alone? I'm not touching the intake on my 76 Valiant...1bbl carb, catalytic converter, EGR....it's the way the 75 yr old lady who ordered to be, so it's going to stay that way.

I don't think it is too much carburetor, per se, mainly because the secondaries are going to stay closed or just barely cracked 99% of the time. I just think you'll never utilize the potential of all that CFM since the stock head, cam and exhaust is still going to be wheezing along. Why bother? Select a carb matched to the engine, or upgrade the breathing characteristics of the engine then move to a bigger carb.

D/W

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If it ain't broke, fix it!

I have to agree with Dennis. A 4bbl remains a 2bbl until vacuum allows the secondaries to open. However, a properly sized 4bbl has the potential to give better fuel economy than a 2bbl because the small primaries may give better fuel delivery than the larger all-purpose barrels of the 2bbl. A bit more work than just bolting on a super six.

Engine modifications typically improve the volumetric efficiency of an engine. Horsepower is a function of engine speed so the faster an engine spins, the more power it will produce. Modifications for increased power always increase the air flow requirements of the engine.

With its air valve secondaries, a 750 CFM Rochester Quadrajet is not too much carb for the slant six. Until, the engine requires the additional airflow, the Quadrajet is a 227 CFM two barrel carburetor. My 225 slant six will never need all of the airflow of this carb but the 350 Chev it was originally installed on never used all of it either. On my mildly modified engine, the secondaries only seem to open up while cruising on the highway around 60 mph.

However, MTV asked if you can slap on a 4bbl carb. Yes, you can but, as with any carb change, the carb will not perform well until it is properly jetted. If the engine is too small for the carburetor, the carb will have to supply fuel from the idle circuits until the airflow has increased to the point where the main metering system can take over. It will run but not well.

Frank

Nobody's twisting your arm!

D/W

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If it ain't broke, fix it!

I just thought of a good way to put this concept in basic, easy to understand terms.

A big carburetor doesn't make (or cause) more power. It can allow a given engine to realize its full power (and flow) potential.

If the potential is not there, you're just wizzin' in the wind!

D/W

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If it ain't broke, fix it!