1992 Miata, LS1, then LS3 swapped

[mazpower]

I haven't updated this thread in a while, all sorts of new stuff for the Miata.

I got a hardtop for cheap. Painted it satin black and called it good.


Then I had a mini catastrophe. I let a good friend drive the car, who had driven it several times in the past, and during a hard 2nd to 3rd shift the passenger side diff mount stud ripped right out of the subframe.













I had the diff repaired and picked up another subframe and reinforced it.









Then I finally got to get started on the set of Z06 243 heads I'd been sitting on for a while. I cleaned up the ports a bit and had them flowed on a bench. At .550 lift, the ported heads flowed 286 cfm on the intake side, stock is 275 cfm. Exhaust was in the low 200s. In comparison, the 853 heads that were on the car before flowed 247 cfm. That's an increase of 39 cfm on the intake side and the mid lift flow is much higher in comparison as well. With the increased port volume - 210 cc versus 200 cc on the old heads - these heads are definately an improvement.





I had a full valve job done on the heads and took .015" off to maintain compression near 11.4:1 static. Since the heads were coming off, I decided to go with LS7 lifters. This helped tremendously with the "sewing machine" noise this engine has had since the beginning. Lifter preload was in the .040"s before, now its at .090".

Bores are still in great shape, pistons look new after 12k miles of HARD driving.



But then disaster struck. Trying to bolt down the new heads I pulled head bolt threads on both banks.



I picked up a Time-sert kit to repair the holes and get the engine back together with ARP head bolts.



With the new heads I have definately picked up horsepower but the bottom end torque is a little weaker now. As I haven't taken it to a dyno yet, the only measurement I could make was a freeway run with my friend's supercharged C5 Z06 making 636 rear wheel HP. We ran 50 - 150 and before the heads I would hang for about 3 seconds and he would pull by about 5 cars. Now with these heads I pull on him until I get into 5th, and he barely starts pulling away, to about 2 cars at 150.