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Old 05-22-2019, 05:58 AM
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I've run carbs for 50 years and now that I have a good understanding of EFI, I'd bite the bullet and go aftermarket EFI. A carb is a compromise at best. Carbs can't compensate for engine temp, air temp, air pressure, altitude, and they can't maintain a constant air fuel ratio. Carbs died with Elvis. Opinions will vary.


Last edited by '48 Austin; 05-22-2019 at 06:16 AM.
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Old 05-22-2019, 08:22 AM
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Originally Posted by vinniekq2 View Post

could you explain to me how weight,gear ratio, how many differentials,or transmission affects how the carb functions? An engine on the stand should run the same when installed into something I always thought?
The engine is freewheeling. It is not loaded down. To produce torque you need a large displacement engine. A 327 is not going to make a lot of torque at low RPM. Once you exceeded to torque of a engine it is going to bog on you. horsepower will collapse. Ever wonder why a 4 cylinder can take off fast at low RPM. It's light weight and geared down then they add OD for top end.
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Old 05-22-2019, 08:28 PM
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Here's another vote for the 3310 Holley 750 VS.
You can tune the heck out of them.

I'd add an electric choke and a "quick-change" vacuum secondary cover.
I liked the purple secondary spring, but I was running a 351C with a 2500 RPM stall convertor. You can also mess around with accelerator pump cams and squirters to work out any hesitation off the line. All Holleys are jetted for sea level out-of-the box, so you might want to test a few smaller jet sizes more appropriate to your local altitude. Read your plugs to tell you if you have it right.

Engine Labs has a pretty good article on this.
Carburetors at Different Altitudes

For small changes in altitude, carburetors will compensate without any modifications. For larger altitude changes, carburetor jetting adjustments may be needed. A rough estimate is one to two jet size reduction for every 1,000-foot elevation increase. That is dependent on various factors including the carburetor manufacturer, the method of mid-throttle transition, and any added provisions for smog control that may alter the carburetor operation. For carburetors equipped with intermediate circuits that are vacuum dependent, changes in engine vacuum from altitude changes may necessitate modifications to the intermediate circuit. Changes to float levels may also be needed.
"Intermediate circuit" on a Holley translates to "Power Valve", and there are several types and tunes there, too. If fuel economy is the goal, maybe a 2-stage power valve. At the strip, a single stage "Picture Window" power valve is the better choice. All Holley power valves are available in a variety of configurations and vacuum increments.

I liked it so much, that I put the same carb with the same tweaks on my 454 in my 66 GMC. I never had a chance to actually drive it, but "blipping" the throttle was very crisp.

A 327 is a really "snappy" little engine which responds very well to a proper tune.
The very low first gear should give you a huge "kick in the pants" and will likely be a LOT of fun to drive.

Last edited by 66GMC; 05-22-2019 at 08:38 PM.
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Old 05-22-2019, 08:44 PM
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explains proper power valve selection.

All of the power valves shown in the video are the single-stage, and here is the drilled versus "picture window" types

Here is the 2-stage type:

Last edited by 66GMC; 05-22-2019 at 08:58 PM. Reason: Youtube
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