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i have a 2300 stall on motor convertor now on my 355 that is a nitrous motor. On motor it runs 12.87@111 with a 2.0 60'
I was spraying a 150 shot and was trapping 6000 rpms with a 28" tire and 3.89 gears in top gear on a th400. 10.5:1 motor, brodix Race Rite 200 heads, solid roller 4/7 swap 252/264@.050 .624/.650 lift FAST XFI EFI. The qtr time was 10.87 @125 mph with a 1.60 (slight wheel spin)

So i have two questions:

1. I calculated my slippage according to TCI's site and it was like 3%. Should i go the next convertor up in stall speed (3000) on motor and gain time in the 60 ft time or would i lose the top end pulling?

2. I plan to run a 175 and maybe a 200 shot on the system, how much more would that affect my slippage?

Your bad 60 ft is mostly the converters fault ! your ultra high trap mph for et is a good sign. at 3-4% slip it is locked up good . most nos cams/engines will give you a wider lobe separation and delayed /extended ex. events .and make them more streetable . sounds like you need to advance /deg. the cam to better than +4 and have the converter loosened up alot . getting 2 sec. out of a 150 shot is extremely good .what manifold and carb r u running ? sounds like a big single and 850 + if it is not your really in the hole . what is the timing on the motor w/ and w/o nos ? Pm me your combo and i can sort it out for ya i would thin that 3200 /3600 on motor should get ya to goals but i need to know what ya got!

I have similar combo just a way smaller 480 lift cam and 4.10 gears
when i built the car initially it had a 2800 convertor and ran
13.10 at 110 mph 1.92 60 foot.
Then i put in a used 4500 pats convertor the very next week
and ran 12.37 at 106 mph and 1.69 60's with no other change.

With that size cam you have you should have like a 4000 -5000 convertor.
that car and motor should be in the mid 11's on motor

you want the converter just loose enough to get it up to speed with the bottle on kill . that makes for a notso ideal n/a converter . a 2800 stall is most likly an 11" and cant be loosen to beter than 3000 . put it into stock or sell it off. dont want to bust ya bubble but your motor wants a 5500+ converter for max et n/a and that will suck on the street and be way loose for the bottle . a 3.5-4k will get it into the dual zone . your 3.9 gear will want a big cooler for low speed hyway driving . and i would use a good synth trans fluid . your gonna beet it up good!!!!