SBC Engine build

[Oriole]

Ok, I understand a marine engine is not like a automotive engine, But other than stainless steel headgaskets, brass freeze plugs, and the J1171 electricals, is there special main bearings that need to be used for thrust, are aluminum heads ok to use? I have a merc 4.3l now and was thinking of building a mild sbc 400 to put in my 16'er. Most of the accessories on that should swap. I know the alpha1 will need to be beefed up. What else am I missing?

 

[Mkos1980]

Re: SBC Engine build

Engine internals are all the same. You cant go real radical on the cam . You can use aluminum heads, but not in saltwater. Aluminum parts will last in freshwater but not as long as castiron. I would also stay with a 350 based block. My engine combo in sig has been flawless and has tons of power. I'm still running stock alpha as well.

 

[mkast]

Re: SBC Engine build

I know the alpha1 will need to be beefed up. What else am I missing?

The gear ratio change.

 

[ringmaster72]

Re: SBC Engine build

Engine internals are all the same. You cant go real radical on the cam . You can use aluminum heads, but not in saltwater. Aluminum parts will last in freshwater but not as long as castiron. I would also stay with a 350 based block. My engine combo in sig has been flawless and has tons of power. I'm still running stock alpha as well.

I have noticed your setup in the past and have been meaning to ask yo about your prop. I have a similar setup, 350 World Products SR Torquer heads, roller rockers, Comp Roller cam with 495/502 lift (similar to the hotcam). I am using the S/S prop that came with my boat(it had a 4.3 liter), but I did put a V8 Alpha on it.

I currently hit about 55-57 mph and am only turning 4300-4400 rpms. I notice that you have tried several props and was curious as to what your thoughts were as I figured I should turn closer to 52-5500, but did not know if this would actually improve my top speed??

 

[Mkos1980]

Re: SBC Engine build

Trough talking to Julie from Throttle Up , We tried a few props and ended up with the smaller diameter props. One would think that with my HP It should be able to turn a Mirage prop easily, but I tried a Mirage 23Plus and it was pulling 4400 RPM's and 56 MPH. I've tried a Hydromotive 22P 4 blade cleaver style and the boat pulled hard out of the water but topped out at 59 and 4800 RPM's. With the Small 13 3/4 x 23P Laser we were able to get 65.2 at 5000-5100 RPM's and then with the 13 7/8 21P we pulled 64.2 MPH.

I've since ordered a 13.5 x 22P Enertia to try out. I do have the 23 Laser for sale if anybody is interested.

Its all in the tuning too though. First run out withthe combo was 61 something and then I moved the timing from 8*, to 10*, then to 12* and 12 produced the most RPM's. I also keep the Edelbrock on stock settings EXCECT the secondary metering rods. I went with one step richer. I also found out this weekend it seems to run harder on 89* octane vs the 93 I've been putting in.

 

[gadget73]

Re: SBC Engine build

Honestly I'd be strongly considering a closed cooling system for a performance motor. Not only will it last longer since you won't have to deal with seawater in the motor, it will run a bit more efficiently since the motor runs hotter. Also, the closed system will let you run aluminum heads and intakes without any concern since you've got antifreeze in there instead of whatever gets sucked up by the pump.