My buddy had a compression test done today and the numbers were 190 across the board.The shop told him the motor is bulit and they also said to him, due to the high numbers it read there's a bump up in compression ratio..Is this true??Also do bulit motors read higher then stock ones?Thanks.

 

Depends on the compression ratio rating of the pistons. 190 sounds about right for a built motor with pistons that are rated around 9.x:1

 

??anyone else.

 

i would say those numbers sounds very high for 9:1.closer to 11:1 imo.

 

Every comp tester is different also. I have seen the same brands read high/low on the same motors.

 

Your wrong,that the same gauge is used and tested on every motor in that shop.

 

My stock Motel was 185 so 190 should be around 9:1 which is fine. 11:1 would be well over 200. My flat too 10.5:1 did 225.

 

The test was done cold ,was yours done cold ??With that gauge on stock motors get 165 or less when tested at the shop..

 

Operating temps with throttle held open.

 

Well this test was cold no throttle ..The race head on the car was a bit of a giveaway thinking the bottom was bulit too ..Wonder what it would read hot ?

 

Your cranking compression #'s are influenced by the camshafts being used.

 

Thats not 100 % true ..there's stock cams in the car

 

Ive got JE 9.1 pistons and mine 190, thats not high , its normal for a good motor.

 

You misread what I said. I didn't say every comp test "shows" different readings. I said the "Same Brand" comp testers can show different readings.

 

Ok, but aftermarket cams will affect the results on a compression test.