High RPM pops thru new summit carb - Hot Rod Forum : Hotrodders Bulletin Board
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Old 09-06-2009, 02:34 PM
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High RPM pops thru new summit carb

So I recently got a new Summit 600cfm electric choke carb. I never had a problem like this w/ the old Q-jet it replaced. I have a weiand intake, made for a spread-bore carb. So i got a Mr.Gasket spacer/adapter to make it work. From the first test drive w/ the new carb, i get a pop thru the carb around 4000, depending on the timing it pops closer to 3000. I have not been able to get rid of the pop w/ just adjusting the timing. I should say, it doesnt overheat, and i drove all the way from greenville sc to st augustine FL w/ it like this. No problems while crusing, just during hard acceleration.

I never had any problems like this at all w/ the old carb. So i dont think it's a ground down cam, or broken valve spring. Does anyone know if doing something as simple as changing the secondary jets would help me?

I had a set of NGKs in it, they were super gunked up after about 5000 miles. Changed them for some R44ts, and it ran even worse than it did w/ the gunked up NGKs. I havent changed them again, i bought a set of R43s, thinkin i might have too hot of a plug in...

I dont know much about tuning and choosing plugs, so anyhelp would be greatly appreciated!

Engine is a SBC .030 over 350. Rebuilt at least 5 years ago. Has some stock heads, if i'm not mistaken the casting # is 166882, i dont think they're anything special. It's got a Weiand intake. Exhaust manifolds. HEI dizzy, not MSD or anything special... True duals w/ cats n cherrybombs... Oh yeah, I have a dial timing light, and when it runs it's best i have to have to dial up to near 60 to line the marker up w/ 0 (make sense?)

I cant think of anything else you guys might need to know

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Old 09-06-2009, 02:56 PM
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Check the fuel filter. Also check the secondary side, it maybe too lean.
Let me get this straight. You are using a Square bore carb as it replaced a Quadrajet, and your using a Action plus intake, why did you need a adapter? the action plus like the Performer bolts on both styles of carbs, the adapter is junk, it disrupts the vacuum and flow signal. All you need is a metal plate that goes under the carb to cover the spread bores wider opening on the secondary side. Get the adapter off and start over, you`ll have to retune it and it`ll run far better.
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Old 09-06-2009, 05:08 PM
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The intake is a spreadbore, the Q-jet fit perfectly. The Summit carb wouldnt fit w/out the adapter. ...It's an older intake,(it doesnt have anything but a part #, fireing order and Weiand stamped on it) I believe it only had 4 bolt holes, they were spread out too far for me to just bolt it on...(It's hard to remember, i know it wouldnt fit right w/out it)
And you're right, the secondary openings on the intake wouldnt be sealed properly w/ this carb alone... Where would i go about finding a plate like that?

I have one of those clear fuel filters (the solid kind. no replacable element) in between the fuel pump and carb, it was replaced the same day the carb was installed.

(dumb ?) How do i go about checking the secondary side? Carbs are like high voltage to me, i'm scared to mess w/ them lol@me

Also, do you think it could benefit from changing the springs and weights in the dizzy? I bought a ignition curve kit, and havent installed it yet; should i bother?

Thanks for reading and replying. I'm learning new things everyday.
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