I'm baffled! In the fall I run 11.90's. During winter I pull the engine and replace gaskets and seals to stop oil leaks. Install new timing chain cover so I pull timing chain set, not crank gear, to trim my cam button for new cover. The chain is only off for maybe 5 minutes at the most. Also I replaced my old points dist., which had the unilite conversion in it, with a brand new Mallory Unilite distributor. Put it back together and started right up and runs great. Next, I change my rearend gear from a 4.88 to a 5.13. Take it to the track and it runs 12.40's. Went from running 1.72 60' times to 1.82. Just checked my cam timing and its perfect. I don't think its the gear because the motor just doesn't want to rpm, like the ignition timing is retarded. Full advance is around 40 to 42 degrees when I race it. Never touched the carb. At least I fixed the oil leaks!!!
Thanks in advance
Jeremy

BTW; 327 with domed pistons revs to 7500 rpm. turbo 350 with 4500 stall, in my 66 chevelle

The only thing i can think of is maybe your advance is different in your new distributor! Good luck ,thats a tuff one.

Degree the cam, check TDC zero?? I'm thinking the cam is phased differently, Use UD harold's quick and dirty method to check it. Roll the motor to #6 TDC and measure the height of #1 valve retainers from head deck. Exhaust closer = retarded, intake closer = advanced.

The easiest would be to put the old dist. back in & try it.

Maybe your engine doesn't like the new rear gear. Was it lazy on the top end before, or pull hard. Does it feel like it's lazy now, or does it pull harder?

I second the advance curve, don't know why anyone would run a 5.13 gear in a 1/4 mile car, and the air (density altitude) can be worth at least 2-3 tenths from best to worst conditions.

OK, its not the cam timing, positive about that now. The engine just doesn't want to rev fast like it did before, to put it simple, the tach is slow. I've been told by the local gearheads that its not the gear either. If it was, I would have had better 60' times and less mph and slower time at the end. It would rev faster and run outta gear. I know its not going to run out of gear. They use to run a 5.57 gear in their 327 chevelle street cars and run 11.50's and 60's with themin the 1970's. That is why I am running a 5.13 gear. I may even go to a 5.38 when I get this all figured out. Once I know its reached its potential I may put a highway gear in it with a 4 speed, who knows! Thanks for all the input, the distributor will be the next thing I check. The car rolls very free so I don't think anything is binding in the rearend or tranny. I don't think it was the air either because I raced it at the track 4 different times last year with no change. The nice thing was it was darn consistent.