Measuring HP with a dyno and TH400 is a futile endeavor, just use it for tuning. Measure the performance by MPH at the track to get real results. Going from manual to th400 usually causes you to gain MPH in the 1/4 and lose between 10-500 rwhp on the dyno. In other words, you don't lose anything, ignore dyno numbers.

P.S. TH400 cars feel a lot slower than Manual cars.

 

700-800 hp on your motor is no sweat at all. It can be done on a stock crank and decent rods and pistons.

 

Your stock crank is good up to around 1300hp or so. Your stock heads will be finished before that though. Stock block is good for what the crank will handle plus some if built a prepped correctly.

 

What do you think the limit of the 243 heads is?

 

Have you considered a well built 350 turbo as opposed to 400? You will save a lot of weight on spinning parts as well as dead weight. If you stay below 800 fly wheel hp, a well assembled 350 will live. 350 is quicker through 1/4 with much lighter internal parts.

If you have lots of cash, look at the Kilgore Superlight TH400 - best of both worlds.

 

I'm going for 800rwhp through the TH400. If I switch it's going to be to a glide.

 

well you'll see more rwhp with the glide.

 

and more $$$ leaving your wallet

 

I'm going to keep my TH400 as long as I can. I will have Greg at FTI build me a glide if I decide to go that route.

 

I bet you "lose" (not the correct term, but the most understood) about 150 - 200 RWHP with the TH400 vs. a good T56. However, to get a T56 car to put 1000RWHP to the ground, you need a stout clutch so the loss gap may be less than that.

 

The limit of the head is the thin deck height. I have seen 900rwhp with the heads , but "pushing water" or "head lifting" occurs. They will make power just not a thick enough deck on them.