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Chris Craft 350k engine build

68L71

New member
I’m having my 350k engine rebuilt out of my 1981 ss170. Is there anything I should know going into it? Cam recommendations? Rebuild the stock heads or is there a better option? The boat is used as a runabout and not much for towing. I’d love to get some more speed out of it. It was topping out at 45mph, but ever since I’ve had it, it has always had low compression in one cylinder.
 
If you want more speed put a big block in it. That will allow you to push a prop with more pitch and diameter. However if you want to keep the engine you have the only option you have is supercharging. There are several available for small block chevy. Whipple, Procharger, and some others.
There's no point in hot rodding a stock engine. Gaining 30 horses won't result in higher top speed. That is limited by the shaft rpm at the prop and the pitch and diameter of the prop itself. Factor in wind waves cargo and you are probably looking at zero gain after dumping a ton of money into parts.
Build it stock, and go enjoy it for what it is.

PS don't run it wide open. That'll kill it right quick.
 
Thanks for the reply. I admit I know very little about what makes a boat go fast. I did figure I would need to change the prop in order to see any appreciable difference. It seems like a small block 350 should be able to make enough power to turn a prop with more pitch. I would not and do not run it at WOT for more than short runs.
 
..... turn a prop with one more pitch...

Props come in 2 inch pitch increments.

sometimes going up one prop size (+2 in pitch) results in lower rpm, but not more speed ( engine torque curve!!.)

All the "tables" indicated that I should be able to turn a 15x21 prop. I can't.
I ended up with a 15x17. wherein a 15x17 prop resulted in my engine reaching its
specified maximum RPM @ full throttle and normal load.

What did gave me an additional 450 RPM @ max, is when I scrapped the thru drive exhaust path and went to a pair of 3" Centek "shortys" fiberglass mufflers and thru transom 3" ports.
KIMG0423.jpg
 
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