i have a small block chevy 12.5:1 compression just recently i had my starter go out so i returned it to summit they send me a Mastertorque 9600 part number pwm-9600 so i put in with 2 shimms now the car wont start it will start to turn my motor over but then it just stops it wont keep a constant crank. i have to turn thekey off and then back on then it will start to do the samething but i leave the key on it wont even try?i reduced the shimms thinking that was the problem but it only made it worse if someone could help me that would be great. i havent yet got the starter tested that will be my mission tommorrow but this is the second mini starter i have went threw in the past 2 years, also is it possible if i could just use a stock starter from autuzone or somethin? O yes the motor only has 20 minutes running.with a brand new battery.

 

If it's a loose gear mesh problem, you would be hearing a bad grinding gear type of noise. Too tight and the bendix gear won't kick back in. Do you think it's a bad mesh, or a lack of starter torque problem?
Try to crank the engine over with the ignition coil wire disconnected so that it won't be able to fire. If it will crank over, then the starter isn't strong enough due to the high compression. If that does work, you could wire in a kill switch to your coil's 12 volt supply line. Have it off when you start to crank, then switch it on after the engine gets zinging over. Also, is your timing too far advanced?

 

Did this happen after replacing the battery? May have a dead cell. Also like already said check the timing.

 

12.5 to 1 compression, well that is pretty stout but a good aftermarket starter shouldnt have any problems if 1) its installed correctly, 2) timing is correct and not too far advanced 3) you got a good starter. from your description id guess a timing or voltage issue so id suggest the removal of spark all togather as camaro 69 suggests and get back to us. Make sure you have a good quality battery and get it load tested. also make sure you have good size battery cables and check those connections!! ground should go right to a bare(no paint) pad on the block and then a ground strap to the chassis and voltage drops should be checked for. this isnt a 383 or a 400 by chance is it?? if you have a motor with those kind of stats its not in your best interest to go for cheap parts (cables, battery , starter etc.) kurt