How to tell if gt40 or not?

[c43amg]

I have a 85 comp, how do u tell if the motor is a gt40? Both speedos say almost 45mph. what should the top speed of a 85 comp be?

[chautauquasun]

Check with Irish Jack or Knoble on this site...both are experts on the markings to identify GT40 heads. Not sure but there maybe a thread on here that describles how to tell what you have.

[DKJBama92Mariah]

On the aft end of the heads there will be a number of bars cast into the head. 2 bars is std heads with hardened exhaust seats, and three bars are the cast iron GT40 heads.

[c43amg]

On the aft end of the heads there will be a number of bars cast into the head. 2 bars is std heads with hardened exhaust seats, and three bars are the cast iron GT40 heads.

thanks for the help. I checked it today and saw there were no bars. Ill take a pic of the heads where you are talking about and post them. I would like to have more power but dont know if i want to tear apart a motor that runs so well.

[DKJBama92Mariah]

Since yours has no ribs, it does not have hardened exhaust valve seats. See http://www.skidim.com/marinization.asp

You should use a lead substitute from an auto parts store in your fuel.

[c43amg]

Since yours has no ribs, it does not have hardened exhaust valve seats. See http://www.skidim.com/marinization.asp

You should use a lead substitute from an auto parts store in your fuel.

ok, thanks for your help.