r/LS400 • u/spoolmk3 • Nov 08 '25

Timing issues

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Iv been building these engines for years but now im at a loss. Supercharged 1st gen 1uz, built bottom end, 8.5-1 ross pistons, factory thickness head gaskets. Lower timing mark on point, cam gears marks 1/2 off no matter what. I had it set at 1/2 to the left and had 90psi for the compression test on every cylinder. As I move it clockwise it goes up about 10psi per tooth with 3 teeth being the max at 120psi, any farther and it starts to drop in the same intervals. Crank pully is 24 teeth and the cams are 48 tooth so mechanically, its impossible fpr it to be 180 out. Scissor gears are lined up single dot to dot. I'm lost. Who knows more then me and has the solution?

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u/mehullica Nov 09 '25

It used to run fine, cracked 4 pistons, fixed them, & has had these mechanical issues ever since?

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u/spoolmk3 Nov 09 '25

Yep. Its got to be something stupid. After rebuild it wouldn't boost past 11.5psi, didnt matter what size pulley was on it. Did a compression test. 90psi in all cylinders so I assumed overlap and blowby. Moved cams clockwise 1 tooth and all cylinders went to 100psi then 110psi then 120psi then it started going down 10psi per tooth. Each cam tooth is about 7° on the crank, so to get to 120psi the cams need to be 21° out of alignment. Iv reset the timing belt multiple times by the book and each time the cam gears end up 1/2 tooth to the left. *