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Carburetors and The Spook

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1 Carburetors and The Spook on Sun 03 May 2015, 12:54 pm

The Spook

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Admiral
Admiral
Gents and Ladies

I have just installed a new carby on The Spook.

Here's what the go is. The engine which is now 357 cubic inches is running out of air at 7200 rpm. That is with 750 cfm of air from a Holley vac secondary carb.

The 750 was good for the the engine when it was in 308 mode. When you apply the Holley air formula to the 308 and 750 carb the 750 will supply enough air to allow a 308 to rev to about 8300 rpm which I have actually had it to when I first built the engine.

However now that the engine has been stroked to 357 cubes and use the Holley air formula it works out that a 750 will only supply enough air for it to run to 7200 rpm. This is exactly the rpm which the engine stops revving at with the 750 carb.

The new carby is a Holley 870 cfm vac secondary carb which by calculation should be capable of running the engine to about 8400 rpm in 357 cu inch mode. This is actually more revs than I want to spin it to but the 870 is the next size up in vac secondary carbs.

Currently I have the rev limiter set at 7700 rpm (which I may increase later)  which the 750 will not allow the engine to reach. The 870 should flow more than enough air for the engine to reach those revs.

We will see.

Spook

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2 Re: Carburetors and The Spook on Tue 12 May 2015, 10:53 am

The Spook

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Admiral
Admiral
Ok guys

Last Sunday my mate Bill and I took The Spook to Tomago for a little outing. Nothing serious, but we wanted to see how the new carb would run on the trailer and if it would idle.

We hooked the water to the cooling system and it started instantly. After we had it up to running temp it needed a little bit of adjustment to screw the primary butterflies open some more and then settled down to a nice clean idle at 1250 rpm.

It's response to the pedal was good with no hesitation coming off idle.

Looking good.

Spook

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