Im building a 400sbc with stock pistons and rods. Im going to try to use my tbi for know and see how that goes. I have bigger inectors and I'm going to buy a spacer. Does anyone know what compression I would have with 72cc heads. Any cam, intake, head, header suggestions are greatly appreciated. Should I have anything done to the stock rods and pistons? Thanks.

 

Your CR will be about 9.2:1 more or less if you have the stock dish pistons and typical .039" head gaskets.

TBI is speed-density; it meters fuel according to throttle position and vacuum with minor corrections for things like air and coolant temp. You will be so lean you won't believe it, since your chip has no idea how much air will now be flowing compared to how much used to be: your A-F ratio will work out to somewhere about 18:1 at WOT. Prepare yourself for a major disappointment.

I have a friend who struggled for years to get a 400 to work with TBI, all the time telling me what a great system it was. He went and bought a Holley 900 4-barrel TB, and I don't know how many chips; finally he gave up and threw all that garbage away and got a Pro Ram and a Haltech, and we smashed the Holley TB to powder with a huge sledge hammer What fun!! I was picking up fragments of chinesium from around my yard for days after that one!

Seriously, get that TBI off of there the first available opportunity, it is basically wasting most of the potential of a partially semi-decent motor.

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"So many Mustangs, so little time..."
ICON Motorsports

 

From what I have read, I think that if you learn to program your own chips you wont have that problem. Most people that have actually looked into the aftermarket chips programming say that their is no fuel changes or they are very minimal. To find out more about this I would suggest reading up on the diy prom board.