2-barrel vs. 4 barrel on GPU

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2-barrel vs. 4 barrel on GPU

Post by rjonesboy »

I am interested if anyone has tested 2 barrel and 4 barrel carbs on a GPU. I would like to know the performance difference (if any) with no other changes (props or pitch adjustments). Thanks

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Post by jim »

Hi and welcome to southern airboat,

Check the 5th post in this thread by waterthunder:



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Post by hillrunnerfl »

I agree with waterthunder.
One thing that has changed on later model 500 CFM Holleys is the check valve in the power valve line. It completly stops backfires from blowing the power valve.
I run a stock Holley 500 CFM and it works great. Keep in mind that motor is only going to use so much air. A 470 running 2900 RPMS is still below 500 CFM. Most four barrels with vacuum secondarys will not open the back two barrels because the motor does not need it. If you change it to mechanical and force it to open the back it will not run at high rpm's.

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