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High RPM miss


axoid

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I'm out of ideas. My SBC starts to miss once it top 4800 rpms. The fuel is fine, I've confirmed that on the Brian's dyno. I have check and replaced everything in the ignition system: coil, HEI module, plugs, plug wires, distributor. I've played around with the initial timing and the timing in the computer. The miss has gotten better, but it's still there. Does anyone have any useful suggestions? Thanks.
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The S/R Torquer 305 heads are also new. They came with the valve and springs pre-assambled on the heads. There have been no modifications made to the heads. The lifters, rods and rockers are stock GM.
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The spec is for 0 valve lash. I tightened each rocker nut as I twisted the pushrod. Once the rod stopped twisting I added a quarter turn and moved to the next rocker. There is definitely popping when I let off a 5500 and there has been some popping below that in the past, but not consistently.

 

I don’t know if it has any thing to do with it, but I had some intake backfires when I was first tuning for the new heads, cam, intake, but that went away when I added timing to the ignition map in the ECU.

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Maybe try the pick-up coil? I know I had a miss in my GTA that kept getting worse and worse.. Of course it was throwing bogus codes when it went out. I know this is quite a few years ago but it was only 13 bucks. Problem is you have to take out the distributor...
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