Went to the drag strip last night and noticed a huge loss in trap speed. The car previously went 122 but the best I could get out of it this time was 113.

I changed from a cai and 1le elbow to a ws6 intake and hood setup an from 1-3/4 headers to stepped 1-7/8 headers and 3in true duals, and from a 26in radial to a 28in bias tire.

The motor still runs smooth. Anyone got any ideas?

 

Might need a tune.. Maybe the change in tire size causing the trans to short ****.. Just a guess..

 

That's a **** ton of lost power. I'd first look into a dead cylinder.

 

Valve float on the top end maybe? To drop ~10mph is pretty big.

How did the times compare?

Can you throw the 26" tire back on it and see how it runs?

 

It's an M6

The motor still runs very smooth for having a .582 cam.

Top end was still very smooth

I don't have the radials anymore.

 

Was there a big difference in weather conditions? Clutch slipping?

 

I failed to see that you went up to a 28 inch tire. As stated from someone else in the other thread that may be your problem. Changing the final drive ratio can make a hell of a difference.

 

Can you post up the timeslips from the two runs?

 

The timeslip showing 122 is long gone. But it has a 1.6 60ft, 11.56, 122.
The latest one was 1.7 60ft, 12.1, 113.

Weather conditions weren't too different. If anything, the older timeslip was taken in worse conditions.

The clutch is freshly broken in. No slipping.

I knew I'd loose a few MPH going up in tire size but this seems a bit extreme. I'm running 4.10 gears btw

 

Well dude I was in your same shoes when I had a dead cylinder from a cracked spark plug after changing out headers.. I lost 9mph and a full sec. in et.. Fixed the problem and all was well.. I found the problem by poking a hole in the top of a water bottle and skeeting water on each primary and bingo...

 

I did just replace all the spark plugs. I'll give that a shot when I get a chance.

 

Just went out and sprayed water all over my headers and plug wires. Didn't see any arching anywhere.

 

I don't think he was looking for arcing when he was spraying water, a dead cylinder would cause that primary to not be hot, so the water wont flash boil on that primary like it would on a good cylinder. Pull plugs and inspect?

 

Exactly ^^^^^

 

That's actually a pretty cool trick, I'm gonna save that in my idea box if I ever need it.

 

Temp guns work really nice too if you dont want to use water.

 

Ah, I misunderstood. I'll check that with a temp gun tomorrow.

 

Checked each runner after a 30 min drive. All were roughly 300 degrees

 

You need to do it from a cold start. I just use my finger to test the primaries, but obviously this only works on a cold start when its not scorching.

 

My guess would be a dead cylinder as well or maybe it idlles on all 8 but dropping one under wot.