75-85 hp carbs on 90 hp?

[cowboy450]

I am picking up a 90 horse Chrysler Sunday. The carbs are missing but there is a set of 75-85 hp on Ebay. The carbs are stamped WE4-1 2/83. I don't know what year the motor is but it is identical to my 1975 or so 75 hp. My question is can I drill the main jets out and run them? Does anyone have an idea as to size? We have a auto carb specialist at work so I have access to small jet drills. I searched the forum and someone said that the 90 was extremely optimistic, would I even have to enlarge the jets? Thanks in advance for any help.

 

[Frank Acampora]

Re: 75-85 hp carbs on 90 hp?

You can NOT drill out the jets. It only makes the engine run worse. Before you buy the carbs, ask the seller the venturi diameter. 75 horse usually had 1 3/16 venturis and 85 and 90 had 1 5/16 diameter venturis. Ask him to remove the bowl and either lift up or remove the float. The venturi diameter is stamped into the casting there.

Don't get me wrong--either will work but the 75 carbs will restrict your 90 a bit. Not a lot, but maybe 1-5 horsepower. why not get the maximum your engine is capable of delivering.

Now, If you have followed the discussion on 40-50 HP carbs, you will note that I have in the past said that changing carbs will not yeild a noticeable increase in power. TRUE, But in your case, the exhaust ports on the 75 are smaller, compression ratio is lower, and the 90 has a lower ratio lower unit gear--2 to 1 versus 1.78 to 1 and develops its power at a higher RPM. Thus putting on a smaller carb will affect performance. If, however, you put 90 HP carbs on a 75, you get exactly-----75 HP.

And yes, on the Chrysler engines, 90 HP was a bit optimistic. When they went from crankshaft to prop shaft rating, the 4 cylinder 105 was de-rated to 90.

See my private message to you.