Author Topic: Spread- to square-bore adapters?  (Read 7268 times)

Offline dave

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Spread- to square-bore adapters?
« on: January 13, 2009, 03:48:41 PM »
First off, great book! Got a question for you - anyone have experiences running a Q-Jet on a squarebore/4150 manifold, using one of those adapters? Any real adverse effect on flow/performance? How about open vs. 4-hole adapters? I've got a 489 Chevy stroker and a 1708-series Q-Jet I'm thinking of prepping for it (you can almost certainly expect a parts order in the near future). Thanks in advance, guys!

Offline Cliff Ruggles

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Re: Spread- to square-bore adapters?
« Reply #1 on: January 15, 2009, 04:45:41 AM »
Dave, we've done quite a bit of dyno testing with single plane intakes and spacers/adapters topping them off with q-jet carburetors.  The open spacers are best, and it helps to blend them into the plenum area of the square flange intake.

There will be a small HP loss, most of which is simply from the narrower plenum on the square flange intakes and the fact that the q-jet is pretty wide across the rear throttle plates.  This slight missmatch will cost some top end power, but not really very much.

We see the same thing on dual plane spread bore intakes when they are topped off with square flange carburetors, as the spread bore carbs line up better with the wider plenums and make more power at high rpm's.

Keep in mind, were are not talking about a lot of power with a good spacer/adapter.  If you want to loose a lot of power, bolt a 600cfm Holley on a factory spread bore iron intake with a 4 hole adapter.  We've been watching folks do this for over 30 years!......Cliff

Offline dave

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Re: Spread- to square-bore adapters?
« Reply #2 on: January 15, 2009, 07:34:58 AM »
Cliff - thanks for the quick reply! I'll probably be back to you in a couple weeks looking for parts. Thanks again

Dave

Offline Cliff Ruggles

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Re: Spread- to square-bore adapters?
« Reply #3 on: January 16, 2009, 06:04:45 AM »
Sounds great.  We stock everything you would need for the later model q-jet, and prefer to use them for high performance work.  Best to call the shop directly for parts orders, so we can go over specifics and get all the parts required to do the job right the first time....thanks....Cliff