Head question 110 hp v4

[DCHOPPERZ1]

I have an engine that was recently rebuilt. One of the origional heads was damaged so i found a good clean used head that was exactly like my damaged one, so i thought. Turns out it had more compression on the side with the replaced head after i ran it and checked comp. I pulled the head for another comparison and found that it is decked slightly different than the origional head. That gave me the higher compression numbers. 110 psi port side 125 psi starbord side. My question is i was told that a thick head gasket would bring my compression down to be balanced with the other side. Any truth to this? Is 110 psi vs 125 psi a big worry. I would think so. Any input on this matter will be appreciated.

 

[bonitoman]

Re: Head question 110 hp v4

I built an 86 110 johnson three years ago and it still runs great comp. was 110 in all four and is still 110. You might have higher compression on the most recent head because that head might have been shaved alittle thinner than the other. There are numbers on the heads. Odd for one side and even for the other. Make sure you replace the odd number with the odd number. Good tough engines.

 

[DCHOPPERZ1]

Re: Head question 110 hp v4

Yes it is cut more than the other. Looking at it close i can see the difference. I do not know what motor it came off of. It was on a shelf with some other heads at a salvage dealer. It was the only one that looked the same as mine.

 

[Dhadley]

Re: Head question 110 hp v4

On a crossflow V4 you cant put a port head on the starboard side or vise-versa. However, there are many different versions of those heads. <br /><br />Look at the number cast in on the good head you are trying to match. Not the number on the original bad head -- it may or may not have matched the good one to start with. <br /><br />A matching set will be ones that the port head is 1 number lower than the starboard head. IE, 323456 (port) and 323457 (starboard). <br /><br />If they dont match up like that, they arent a matching set. By the book, thats not good and I personally dont like to run motors like that. In the real world there are a bunch out there that run like that for years.

 

[DCHOPPERZ1]

Re: Head question 110 hp v4

I understand that part. My main question is, can i install a thicker (low compression) head gasket to compensate for the milling on the head i want to use. I am trying to get balanced compression on both sides of the motor. I cannot find a replacment head with the casting # i need. I do not want to run with 1 side 125 psi and 110 psi on the other.

 

[phatmanmike]

Re: Head question 110 hp v4

why not just shave the old head to match the new head?<br /><br />or install TWO head gaskets, if that would even work, ida know?

 

[DCHOPPERZ1]

Re: Head question 110 hp v4

I thought about that. The OMC tech said that if i run 125-130 psi i may run into a detonation problem. And the motor will run hotter. I am looking for 110 psi on all 4.

 

[ledgefinder]

Re: Head question 110 hp v4

DChopper-<br /><br />I can confirm that there is a thicker head gasket commonly available, from OMC & the aftermarket. Should just about do it (125 -> 110), and may help - though if DH says there're other differences in the chamber shapes, as he says she still may be out of balance.

 

[DCHOPPERZ1]

Re: Head question 110 hp v4

I looked very close at the chamber shapes of the replacment head.That was another concern of mine. They are identical. I am going to try a thicker head gasket tomorrow and see what i come up with. Thanks for all the replies.