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TPI top-end on 305 carb motor?


C4RACER

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Has CMC considered allowing a spec 305 carb motor to run with a TPI top end instead of the holley / performer combo? I would think this would be a reasonable change that would not add any HP - it may add some tq, but should not go above the dyno limits. The TPI bottom end has several advantages that should net more power than a 305 carb motor: better flowing heads, roller cam, higher CR.

 

Why allow this? Simple. To make an easier and cheaper conversion from a carbed motor to TPI motor. For example - I have a carbed CMC car - and it runs pretty good in general, but I notice some bogging in corners like T14 and over the hill at THill that the fuel injection should fix. But I don't really want to buy a whole new motor, especially since my carb motor is fresh. And I do have a complete TPI top end sitting in my garage. So why not combine the two? Then if I blow the motor at some point I can install a TPI motor down the road and the electronics and fuel part of the conversion is already done.

 

Has this ever been raised in the past? Worthy of consideration? I could use my car as a test bed if needed and do before / after dyno runs to show the result of such a hybrid motor before adding it to the rulebook.

 

Scott

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i think due to update/backdate rules, any combination of of engine parts are legal as long as anyone one of the single parts are legal for CMC.

basically, all 305 motor parts from 82-92 are legal to use in any combination you feel you want. so, if you have a 84 305 TBI or carb motor and you want to put a 92 TPI manifold and EFI set-up on it, you should be able to.

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A few comparisons

heads changed to center bolt in '86,

as did location of dip stick from left to right side ( mucho faster )

and different cam for carb vs TPI

not sure of the crank

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I believe the angle for the intake bolt holes on the TPI heads are unique.

 

jb

 

Yes - that is true, but nothing a grinder won't take care of. Basically you just need an oblong hole and it will bolt to an early head no problem. That is how the aftermarket TPI bases are made.

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i think due to update/backdate rules, any combination of of engine parts are legal as long as anyone one of the single parts are legal for CMC.

basically, all 305 motor parts from 82-92 are legal to use in any combination you feel you want. so, if you have a 84 305 TBI or carb motor and you want to put a 92 TPI manifold and EFI set-up on it, you should be able to.

 

Is that true?

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modifing those parts from stock may cause that to not be legal. but the ford guys take the best of every year from 79-04 or something. they have some very nice cams to pick from as an example.

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The carb bog can be drastically reduced - mine was pretty much eliminated altogether like you are experiencing at T-Hill. The right combo of jet sizes and float levels are needed.

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Is that true?

Yes, read the rules!

 

Sounds to me like all you need is a cam and the gear already in your garage to convert back from a spec carb motor to the TPI.

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