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Misfire at 2500 rpm

2866 Views 9 Replies 6 Participants Last post by  Motorhead
Misfire at 2500 rpm in #1,4,5,8 piston. worst of them all is #1, it doesn't fire until engine warms up and it will skip all the way to 5000 rpm.
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How about some more info about the engine. What size, what intake, what carb, what ignition, what cam, what, what, . . . . . ?

It is suspicious that the misfires are all on the outer corners of the engine. With limited info, I'd say it might be a fuel problem?

Have you recently changed something or moved the plug wires?


65' Stang

393 stroker, Toploader 4 spd, 3:50 rear.

Victor Jr. knockoff heads, 282S cam, Stealth intake, Bigs Stage 5 750DP, Accufab headers, Scattershield, Caltracs.

<font size=-1>[ This Message was edited by: dennis111 on 3/23/06 7:58pm ]</font>
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It is a 302 bored 30 over with f303 cam, Unilite, blaster 3, Air gap intake, Holly 650 dp, windsor jr heads and 10.13:1 CR.
I think I'm expleaning my self wrong. The engine sounds good, but when I check it with the timing light it will skip sparks around 2500 rpm and up. #1 is the worst. At cold start skips like creasy at any rpm. I can confirm it because #1 spark plug looks dark. The rest of them look right in the money.
Anybody has an idea of how much power this combo sould make?
Only running good on four cylinders, I'd say about 150hp...
Check plug gap, condition of cap, rotor and plug wires, try moving the plug wires while observing the 'skip' condition to see if it changes, that will tell you if the plug wires are leaking/arcing. Are you running a ballast resistor to the coil? Is your unilite's power lead hooked to the +12v or coil side of the ballast resistor? It's supposed to be hooked to the coil side IIRC, to keep from burning up the module. The fact that you are observing the problem with a timing light means it has to be a problem in the ignition system, so worse case if you can't find it then start swapping out components, starting with the plugs, then the wires, then the distributor.
150 HP!
I ment with everything running good.
I'm going to get another set of cables to see what happens.
My other question is: I only get 10 to 11 psi of vacume at idle around 900 rpm. Is that good with F303?
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11" of vacuum sounds right on a 302 with those heads. Might gain a little more with some tuning.

As for the spark problems, check all the components as suggested. Try another coil if you have one, just to rule it out.
On 2006-03-23 10:41, Yaap wrote:
150 HP!
I ment with everything running good.
OH, well in that case...

I'd guess around 325hp at the flywheel, if the heads are box-stock... if they've been cleaned up a little, closer to 350hp.
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