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07-08-2019, 06:01 PM | #1 |
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high rpms breaking up
My 39 coupe - EAB engine - all listed below 2- closer to 3 years old
dual Edlebrock 94s built by Charlie Disto built to 11A by Bubba Coil built by Skip Radiator pulled this winter and had it cleaned. Car @ 95F runs no higher than 190 which to me is perfect. ALL TOP SHELF BUILDS - and money well spent Car starts right up Idles nice Runs smooth at 60 even 65 highway Issue is when I get on it - like up a hill or just for heck of it - upper RPMs it breaks up. Where so I start? Condenser? Stop break? or??? BTW - I already changed fuel filter....which is just before electric pump...
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07-08-2019, 07:17 PM | #2 |
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Re: high rpms breaking up
Mine will do that if I really stand on it and rev it up between shifts. I pretty sure mine is a float or fuel pressure issue causing it to lean out.
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07-08-2019, 07:27 PM | #3 |
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Re: high rpms breaking up
Do you have any idea of the RPM you are turning when it starts breaking up? I have seen 5500 from my 258" 8BA with a MAX-1 cam, Isky 185 springs, prepped Edmunds heads, a Mallory dual point, and one 2G carburetor. I don't think I'd want to see more than that. The engine was also balanced when it was built.
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07-08-2019, 07:43 PM | #4 |
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Re: high rpms breaking up
No I don’t. no tach. I’d guess 3500-4000 but that’s just a guess. I’m all stock with exception of what I’ve mentioned above. Build is 30+ years. If they zero’d odometer at build I’m reading 37,000 miles, of which I put 11k
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07-08-2019, 09:16 PM | #5 |
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Re: high rpms breaking up
The missing occurs under conditions of high rpm and low vacuum, which is also the occasion of high cylinder compression pressure. That raises the voltage needed to jump the plug gap. Maybe your spark is not strong enough to jump the gap at those pressures. Whatever in the ignition is 30 years old would be suspect, especially the ignition wires. Maybe the coil.
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07-09-2019, 12:39 AM | #6 |
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Re: high rpms breaking up
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07-09-2019, 05:34 AM | #7 |
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Re: high rpms breaking up
Thanks guys all good advise. I’ll check plugs and wire connections. Then replace condenser it’s a cheap fix if that it.
Gonna check choke rod too maybe that’s it. I have K&N air filters cleaned end of winter but will check that as well.
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07-09-2019, 06:22 AM | #8 |
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Re: high rpms breaking up
Sounds like weak point springs. G.M.
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07-09-2019, 07:18 AM | #9 | |
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Re: high rpms breaking up
Quote:
my experience is that if it starts coughing under full throttle it's getting to much fuel or not enough timing if it start's to lay down it's not enough fuel or to much timing Just be careful with the timing!! tinkirk |
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07-09-2019, 12:00 PM | #10 |
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Re: high rpms breaking up
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07-09-2019, 12:04 PM | #11 |
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Re: high rpms breaking up
One of the reasons for dual points was better coil saturation at high rpms. Might be worth putting it on a machine and see what is going on.
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07-09-2019, 12:09 PM | #12 |
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Re: high rpms breaking up
Thanks Bubba Guaranteed for life. But knowing his situation, I hope it’s one of the other suggestions
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07-09-2019, 12:34 PM | #13 |
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Re: high rpms breaking up
We run all distributors on our Sun machine to be sure the points retain contact. It plainly shows on the strobe. The quality of the point sets being sold today is very low. Of the last six we checked, four were unusable. As said above, point "float" is a likely problem. Another is low dwell, preventing full saturation of the coil. A weak condenser will also do it. Find a shop with a machine.
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07-09-2019, 01:09 PM | #14 |
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Re: high rpms breaking up
I had the points out of my Mallory dual point a couple of days ago to check for wear and pitting, and they seemed to me to have a lot more spring pressure than some ordinary point sets. I'm wondering if the "points float" guys might be on to something. It might have just been my imagination, but I noticed right away that they seemed real stiff.
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