[Pampered-Z]

330s and 1/8 are on par for a low 14 second pass. It was a hot day and you were on a prep'd track, your not going to spin and in fact, you have to overcome all the VHT that is sticking your car to track and that takes HP, so your car could be slower on the track. When you ran before on street tires you probably were spinning. Your 60' were probably down even though your ET was quicker because when you spin you somewhat get a running start. Sticky tires on a sticky track use HP.

You say you have an LT4 conversion, is that the cam or the entire head/cam package? What do you mean by full exhaust? All stock?

I see a few things I'd change: As already stated, your convertor and gear combo is hurting you. Along with what everyone else said I would try dropping down to a 52MM TB. 58 is probably too large for your set-up. I lost .2 when I went from 52 to a 58 TB on a motor with shorty headers, lingenfelter cam and stage II heads. Switched back to the 52MM and the car picked right back up. If your still running the stock exhaust manifolds then thatis holding the motor back allot as well!

I would put the car on a dyno and see where you're peaking, and also look at your data log for things like timing and injector pulse. Could be that your're getting false knock and as a result allot of timing is getting pulled out??

Properly tuned a LT4 should go 315 - 320 RWHP. But that is a small cam for racing. It makes good torque below 5,000 but runs out in the upper RPMs. You may just be spinning too far past the HP peak on the shifts?