85 horse power head on 75 horse?

[bashr52]

Looks like I've got one dead cylinder and a second on its way out on my 75 horse. I've found a good 85 horse power head that had a bad lower end. Can I swap them, and add my carbs and ignition and such?

Thanks

 

[Frank Acampora]

Re: 85 horse power head on 75 horse?

What years?

 

[bashr52]

Re: 85 horse power head on 75 horse?

He said late 70's, early 80's. Mine is a 1979, and it looks identical. Same 3 carb setup, electrical system, etc.

 

[jerryjerry05]

Re: 85 horse power head on 75 horse?

Carbs will be jetted wrong.Not enough gas going through.Jthe other stuff will work if it's the same ignition system.J

 

[bashr52]

Re: 85 horse power head on 75 horse?

Any idea what jets I'll need? I've got a whole set of reamers I can use to open them up to the correct size.

 

[Frank Acampora]

Re: 85 horse power head on 75 horse?

The jets on the 75 carbs are probably around .066 inch. To enlarge them you need a set of letter drills or number drills.

HOWEVER: Since the jets are sized to limit wide open throttle mixture to about 16 to 1 air to fuel, and since the carb body is vented to match these jets, and the venturis are smaller than 85 carb venturis, AND since the extra air flowing through the carbs with an 85 block will be negligible, re-jetting is an excercise in futility. The carbs will work just fine if you install them as-is. The engine will still get its 16 to 1 ratio air to fuel, but just a little less, so the 85 block will not develop the claimed 85 horsepower.