I've been racing the 1/8th mile @ 6.29 to 6.32 seconds until I lost the rearend will making a run. I was finishing a run when the pinion gave way. We replaced the gears using the same ratio. When I went back out we were running low 6.50's. That trip I broke the roller off a rocker arm and it cut into a retainer. When I was was replacing the retainer I noticed that I had a broken valve spring also. I replaced the spring and retainer and went out for test and tune last night. We ran low 6.50's again. Is it possible to have lost time due to gear change even tho they are the same ratio or could there still be something wrong with my motor?

How long have the valve springs been in the motor? Either way i would check and replace all of them they may be getting weak.. Do not make too many changes at once or you may miss where the problem was. If that does not do it relook at the rearend..... JMO

The valve springs have less than 100 passes on them. Could I have broke it when my car hit the rev limiter.?

Not sure where your rev limiter is set but just hitting the limiter itself should have no effect on the springs.Springs can break for any number of reasons including fatigue, coil bind an because you are wearing a yellow shirt. They just seem to break for no reason some times. Not saying this is your problem but i personally would change them all and be sure i have correct spring heights and verify there is no coil bind.Check your cam specs and spring specs to be sure they are compatable components.This way you know that any time loss that occurs after the change is not due to springs and you can look elsewere.Not sure if this helped but thats how i would proceed.....

x2 Change all the springs...

Did the motor hit the rev limiter if so there's a good chance you laid some fins over in the converter.
we had it happen when we broke a rear one time.

Have you checked the timing, to see if it flucuating, it's possible that if you are running a bronze gear, it could be wearing. If it is it's easy to lose a couple tenths.

Zip.

Run a leak down test. If you broke a spring you could have bent a valve.

TS1955

I think the converter also. Sometimes when the rear end breaks it takes out the converter..

I got to thinking back on this post and I had a simlier problem after breaking a valve spring which in turn bent a push rod..etc...replaced this stuff and still lost 3+ tenths...it actually felt like the car gained 600 lbs.
Come to find out after pulling off the intake I wiped out a lope on the cam shaft....
it never popped skipped or anything just became real sluggish..

i'm sure by now you found it..just thought I would post this to help someone in future