75hp johnson 1977

[Dodgeviper80]

Trying to replace a damaged head part #320389. Will the 70hp part #319335 suffice. Is there a compression difference in the heads?

 

[fdrgator]

Not a betting man, but I'd almost be willing to bet a buck that the 75 is a higher compression engine.

EDIT: Hm.m.m., I just noticed that they take different cylinder & crankcase assys. That raises a flag on compatibility. Better wait for a more expert response.

 

[faztbullet]

It will fix and is lower compression than your 75 head

 

[Dodgeviper80]

How much lower we talking, the reason I'm replacing is last owner snapped a bolt in the water jacket then did a jacked up drill job.

 

[faztbullet]

Around 10psi...

 

[Dodgeviper80]

Thanks for the advice, I was at work and wanted to ebay it there. Got home checked the part number on the original head (should of already done that)and I'll be damned it's the 70hp head not the 75hp. I have two stingers same vintage and both have the 70hp head. Makes me think it was original and the high compression 75hp head was an upgrade. That would explain my difficulty in finding a replacment.