Thread: 383 Stroker low vacuum and sluggish

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Originally Posted by Devon32

36sedan, Thanks for the procedure for finding TDC. Just bought the piston stop tool but think I might try your way instead since I’ve never done it.

You’re welcome, I can’t take the credit for it though, it is just a modified version from others, I just re-did it to suit me.

Originally Posted by Devon32

Just did a compression test and every cylinder came back at around 120. Lowest was cylinder 8 at 118 and highest was cylinder 7 at 122. Should I be worried that they are very low but are all consistent?

Compression is equal that’s good. However, the numbers point towards a lower compression motor (below 9-1) and this surprises me for a stroker kit, they’re usually 9.5-1 > 10.5-1 and occasionally higher depending on the heads and deck heights.

Originally Posted by Devon32

Cylinder 5 and 6 have extremely tight clearances for the spark plug boot and they were slightly melted so I replaced all the spark plugs with NGK UR5 shorty plugs and gapped them to .035 and have new wires on order. The plugs didn’t look bad, slightly fouled.

This is not unusual with tight motor spaces. I have to use ceramic boots on mine or they arc out, and this may be part of your problem. If these cylinders are arcing out then they are not firing and performance will be way down. Picture of the plugs would help.

Originally Posted by Devon32

Before pulling everything I played around with the carb and timing some more and got vacuum to sit at a steady 11.5-12 inches, timing was still around 55 though. The idle isn’t rough and don’t hear any pinging or knocking.

What is the idle rpm?

Originally Posted by Devon32

Distributor is a pertronix flame thrower.

Does it have a Pertronix ignition box between the distributer and the coil?

36sedan,

Idle rpm is about 900. And I don’t have an ignition box between the distributor and coil.
New wires and heat shield for them should be in tomorrow and I’ll hook everything up and see if that makes a difference and get back to you.
Is the PDF you attached to check the condition of the timing chain? 3F27FBBD-5562-423A-9392-9643C1359F28.jpg6513E97A-9E7B-4846-9BCB-55C782F4AA19.jpg