I was only able to make 3 passes and they were not even full passes. Each time I had a back fire in the top of 2nd or the top of third....not sure why. I can only speculate.

AFR was 11.7:1 on 2 of the passes. Not sure on the other
temp was 48*f outside
no wind
100% 110 octane fuel
timing 20* locked
100% meth starting @ 4psi

new plugs = rn9yc @ .024" (maybe to wide...didn't have time to regap at the track) to many track delays. A newer Corvette exploded the rear and put gear lube down. They were kicking parts to the side of the track.

Old head from last year and old springs ( to weak for 25psi?)

2nd-darys to lean? I have an 87 jet in there now.

Best pass was:
1.934 60'
1/8=8.362
1/8mph=89.14
1/4=13.43
1/4mph=84.04

Nice 1/4 mile speed vs 1/8mile speed

After thinking about this more. The "backfire" I'm experiencing may just be the intercooler hose blowing off at high boost conditions and making it sound like a backfire. I'm going to scuff the smooth (painted) intercooler pipes and double clamp them as well. I'm also going to put the 340 springs on this head too. Everything else seemed fine.

Retooling for maybe 11/23 or 11/30

I did some investigation and the issue is probably the slant six valve springs.

On an inefficient setup the pressure ratio can be as great as 3:1.....meaning the exhaust may have as much as 75psi of back pressure (vs my 25 on the intake)on a spring that has maybe 65psi on the seat.

I have had valve springs go bad on an NA motor and kill perf over 3500 RPM. Nice times and progress anyway!

Lou

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Home of Slant6-powered fun machines since 1988

Looks like you're making good steam at the 1/8th.

Should be fun when you can get it all the way to the end under power.

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Official Cookie and Mater Tormentor.

Should be interesting if I can get it down the track. Anyone have any small block heavy duty valve springs? Used is fine.

I'll have 2 more chances if the weather holds. 11/23 & 11/30