Compression Test Results

[Guest boggie]

Hi All,

 

I don't think I have a problem but it's more a point of personal interest: What is the exceptable divergence between cylinder compression? I have a lightened / blueprinted / overbored pinto fitted with a brand new Maxiflow 2 head, skimmed to 10.5:1 with a Kent RL31 cam. Just bought a compression tester to investigate a friend's sick engine so I thought I would try it on my newly rebuilt engine. Here are the results of my compression test cranking on the starter with throttle wide open:

 

Cyl 1 = 167psi / 11.7 KG/cm3

Cyl 2 = 170psi / 11.9 KG/cm3

Cyl 3 = 176psi / 12.3 KG/cm3

Cyl 4 = 174psi / 12.2 KG/cm3

 

The largest differend between cylinders (no1 and no3) is a little over 5%. Is this within normal accepted tollerances? I would have thought they would be closer but I am clearly no expert.

 

Many thanks, Boggie

[Guest chris brown]

God I’ve seen lots of rebuilt engines worse than that. I would suggest yours is as near perfect as you are likely to get BTW better than 15 psi deviation is the accepted norm

[miikae]

God I’ve seen lots of rebuilt engines worse than that. I would suggest yours is as near perfect as you are likely to get BTW better than 15 psi deviation is the accepted norm

 

 

I too have seen worse and would be very happy with those results .

 

Mike

[Big Jim]

No problems there, just hope you've torqued the cylinder head correctly.

[Guest salty_monk]

Looking good... get out & drive it

[Guest boggie]

Thanks Guys,

 

Glad to hear that! I made a schoolboy error timing the cam (timed it to exhaust not inlet). Luckily I tried turning the engine over with a socket on the crank before turning the key (I always do this, just in case). When I found I could not turn it, I tried rocking the car in first gear. Then I noticed my dial gauge was sitting on the wrong rocker! I was worried that I may have done some damage but now I know that I got away with it!

 

Nearly there now. All I have to do now is brakes (4 discs, 4 calipers, change the brake fluid), MOT and then try and finally sort the cooling system properly!

 

Cheers, Boggie