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Autocross 85 RX7 GSL-SE Racing Beat (int/exh Holley 650) cornering sputter

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Autocross 85 RX7 GSL-SE Racing Beat (int/exh Holley 650) cornering sputter

Old 11-08-07, 03:05 PM
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Autocross 85 RX7 GSL-SE Racing Beat (int/exh Holley 650) cornering sputter

Okay, we were told that we might encounter a hesitation on corner exit but this is a joke!

We just installed Racing Beat's 6 port intake, carb and header onto an 85 Rx7 GSL-SE.

We've done two events now. The first time out it would sputter, pop and flood out in any corner. And sometimes even under heavy braking. When it would finally fire again (keeping it rolling while in gear) a huge flame shot out of the tailpipe. So we think there's a good chance it's flooding rather than starving. The A/F guage reads way rich too. We adjusted the float levels and it seemed to get somewhat better but it's still sputtering in the corners. The straight line power is quite nice though.

Before the second event we made sure that the whistles and side pivot floats were installed correctly and extended the vent tubes. It's still getting better but I spent at least 5 seconds every run waiting on it to fire again. Seeing as how I was <4 seconds from fastest time overall and <0.6 seconds from winning my class, that sucks! The way it sits now after adjusting the throttle squirters down, I can hold a constant pedal in the turns and it won't cut out much. But feed it any more gas and it'll puke.

We noticed when we put it together that the intake's runners were isolated and the inner intake ports never crossed paths with the outers which means that the a/f mixture from the carb's primaries never mixes with the secondaries until it hits the rotors. Wouldn't it be optimal for us to port the intake so that they have a common mixing area? I've seen some in the past where there was a point in the center (top side) that seperated the four runners. All the runners were angled cone-shaped and smoothed out. Is that a common method?

It's so close! While we are finally competitive in our class again, we are leaving a lot on the table due to a carb issue. I have gotta get this fixed before the new season starts in January. I'll be driving something else for our December event. But I want to make a run for a championship in 2008.

The RB carb was supposed to be a 600 cfm model for the 13B 6 port but we think this one is a 650. It is definately a double pumper. We have also converted the ignition to the 3 coil deal where the leading plugs run straight off of the coil and bypass the distibutor cap. One area of ignition concern however is that the parts store didn't have the 4-prong spark plugs like what we pulled out so a set listed for a 2nd gen were used. Those were flat on the bottom with 4 grooves in the outer ring. So that could be causing a problem too.

Old type: / Type now installed:

Has anyone ever had a problem with those. We're planning on putting the old ones back in.

Should we rejet the carb?
Should we try jet extensions?
Should we port the intake so all 4 runners have a common area beneath the carb that's open to primaries and secondaries?
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Old 11-08-07, 04:14 PM
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The second gen. spark plugs will run fine on any carbed first gen.

As far as the sputtering issue, IIRC there's something in the 1st gen faq about adjustable fuel bowls that drastically improve out of turn response maybe do a search on that.

You should def re-jet the carb if you're running a 650 with the Rb jets on a stock ported 13b. You should be running rich because of it.

Adding a carb spacer between the Holley and the intake manifold alleviates a little of the sputtering also.
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Old 11-10-07, 11:31 PM
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the 650 Holley should be center pivot floats not on the side. you sure it's a 650 or maybe it's a 600?
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Old 11-11-07, 08:57 AM
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Yep, we upgraded to center pivots. I just said it wrong. I guess I'll have to find some numbers on the carb and do some research to find out if it's a 650 or a 600.

So if it's a 650 (or even a 600) I probably need to rejet it. Am I gonna have to just see what's in there and go smaller until I get it right or is there another source of information out there that might already have the magic number I so desire?
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