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Discussion Starter · #1 ·
My motor has developed a slight skip. It has not hurt the cars consistancy at all but it skips and you can hear it. I've won a bracket race and 2 dash for cash events with the miss so it hasn't hurt much. It is slightly worse as time goes along. Been working on it the past 5 races. I have checked everything and it still has this slight skip at higher RPMs. I'm obviously missing the problem so what can cause a high speed slight skip? 565 BBC, 14.7 compression, 800 lift roller, 1050 Dominator, crank trigger, MSD 7al, plugs gapped at .035. I added 2 numbers of jet to the carb last night and it didn't change a thing other than drop the EGT a little. All help is appreciated. RM
 

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Got a wounded valve spring possibly?
 

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Discussion Starter · #3 ·
None broken but the intake springs have fallen down to 260 from 310 when new. The exhaust are all 300 yet. It has crossed my mind it could be the springs but others with a similair cam are running less with no problems so I just don't know. I may swap the int and exh springs just to see. Been thinking all day about it. Now I'm leaning toward low voltage. Never had a problem with 5 yr old batteries last year and I replaced both batteries last Oct and it was fine earlier this year. But it didn't skip the first couple passes two weeks ago and I thought I had fixed it. Then it skippped later after the batteries had been short charged. May add a volt meter for next race. Thanks, RM
 

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Discussion Starter · #5 ·
The car hasn't lost any ET I can tell. The best ET ever was 5.32 and in the heat on 50 pass tires it's running low 40s high 30s. I can't feel the skip at all but I can hear it real well. My crew man can hear it when it does it in the water box too. The engine is just humming and then it does a DUH,DUH thing. Last night in high gear about 7100 or so it skips often and got more rapid. Since this started I have checked, Valve springs, valve lash, ohmed the plug wires, checked rotor phase, timing, cleaned the cap and rotor, Changed the plug gap from .040 to .030 then replaced the plugs and gapped them at .035, AR3933 plugs, added ground wires to the motor, checked crank trigger gap, added 2 numbers of jet to the carb as well as cleaned the carb and replaced the gaskets, checked float levels and checked all the wiring as best as possible for loose or broken wires. RM
 

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Discussion Starter · #7 ·
My coil is inside the car and the wire goes through the firewall. I did not check it either. I'll check that tomorrow. Thanks, RM
 

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what wires are you running? have you done an ohms check on all the wires? wouldnt be the first time ive seen them arc at higher rpms, while not common with good wires anything is possible. plus that'll tell you if the wire is going bad, most good wires are about 40-50 ohms per foot or 3.3-4.1 ohms an inch.
 

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Discussion Starter · #9 ·
They are MSD wires and I ohmed them last week except for the coil wire and I'll check it tomorrow. Everything on the motor was brand new last spring and the engine only has 144 passes on it now. The car stays in a heated shop so it hasn't seen any severe stuff. RM
 

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i totally missed that you said that already lol, the only other thing that comes to mind is a problem i had with one of the cars, similar problem but it happened around 6000 after it got to the point of be constant i tracked it down to the pickup in the dist. going bad. since youre running a crank trigger have you checked the pickup there?
 

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Discussion Starter · #12 ·
7Al2 and I haven't tried a new pick up cause I don't have one and they cost alot just to test......LOL. I ran the plugs at .030 all last year and stretched that to .040 earlier this year with no skip. I went back to .030 a couple weeks ago which didn't fix it so I bought new plugs and gapped them at .035. Why you think going to .026 is a good idea? It does have 14.7 compression. RM
 

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you can do an ohms check on the pickup, you should have 65-85 ohms. a tip i found out from mine, sit there for a few sec. with the meter on to be sure the ohms stay steady.
 

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Discussion Starter · #14 ·
Just checked the pick up at 78.3 ohms and steady and the I ohmed the coil wire and it's good. Turned everything electic on in the car and checked voltage at the power terminal and got 11.93 volts. That was with the headlights on too and I never race with them on. Going to pump the fuel pump again and see what it does. Last time it pumped 1 gallon in 14 seconds. RM
 

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I was thinking the compression was blowing out the spark with the 7AL 2,so tightening up the gap a bit more may make the spark more stable.Are you running the sheilded cable from the crank trigger pick up to the 7AL 2? There should be 3 wires there.Could be getting interfearance from water pump,fan,alt, fuel pump, spark plug wires,etc.That wire(sheilded) shouldn't be run amoungts the others,the crank trigger wire.As this will lead to miss-fires

Check the gap of the crank trigger set it about .060
 

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Check the MSD chip

I would recommend trying another chip in the high side rev limiter. I've seen them go bad many times in my car and others. Sometimes they operate either higher or lower than labeled. The most recent time it was not working at all.:(
 

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Discussion Starter · #18 ·
I'll try closing the gap up but it has been fine at .040 til this skip developed. Since it some passes doesn't skip I doubt it's a header gasket plus the thing has never had a header leak problem. There is no high side chip in it. All the wires are where they have been since I put it together and it's been fine til lately. The trigger wire is the twisted dual wire not shielded one. But it is run alone not with or around other wires. I'm moving the line for the fuel pressure guage and idiot light now. It was at the back of the fuel log and I am moving it to the front just to insure it's not been lying to me.
 

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Hiya Mac It's me TomK57 from years back. I did some welding on my car with the battery disconnected, but the wires on my MSD6digital and distroyed it car ran great cold, box got heat in it it skipped at high rpm only, what i did was put a test plug on the coil wire right out of the coil, when warm it had a white spark, when the box was cold it was blue.. Low and behold i replaced the box skip went away.. I called MSD and told them my problem and this is how i found problems, just try checking the spark with the 7al at running temp.. I hope it's that easy Mac TK
 

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Discussion Starter · #20 ·
Hi Tom, been awhile. I ordered a new fuel log system. While playing around moving my pressure pick up I found a possible restriction in the present log which I think is my problem. That also makes sense cause as I added jet the skip got worse. Used more fuel so it ran out worse. I planned to borrow my buddies spare box and pick up just to try that if this don't work. We'll see what happens. RM
 
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