142 supercharger on a stock 5.7 ?

[Junkyardroad]

Thanks everyone for the responses. This is what I’m thinking... this carb’d 350 might have made 260 hp at sea level, I bet it’s closer to 200 up here. And this boat is a big fat girl.
It has a Weber 9665 AFB, jets and rods are still available. Probably 625 cfm from what little I can find. It’s was running super rich with the stock .101 mains and 70/42 rods. That’s where I’d start with a blower under it and tune from there. These little superchargers are designed for stock 350 engines and fuel systems, and I don’t understand the difference between <5000 rpm marine / automotive application?
Overdriving them makes too much heat. So 4-5psi might add 80-100 hp tops, well within the 300 hp spec of an Alpha, and enough to pull my XL size up on a ski. (6’7”). I have several sbc cores from 283 to 400, but the original engine in the boat is in great shape. And it’s in there and it’s spotless.
With regard to fuel injection, I’ve tried a couple aftermarket units in automotive applications and they really don’t add much power over a well tuned carb, but they do add drivability under 3000 rpm.
Anyway, the blower snout looks like it would hit it thermostat riser, and if so, that would require enough effort to change that it might not be worth it. But I cannot be the first one to try it?

Edit to add: several companies make an adapter plate for adding a wide band O2 sensor to wet joint exhaust. Seems like just the thing for carb tuning. Anyone tried it?

 

[Scott Danforth]

EFI can't add power, never could. Changing engine architecture does

Your 400 and 283 blocks are old 2-piece RMS motors which is a 20 year step backwards. Useless in this application.

Vortec heads recommended

The 142 will most likely interfere with the marine T-Stat housing. You can't use an automotive T-Stat housing unless you switch to a heat exchanger.

You can't put a heat exchanger on a used motor unless you boil out the block

You may need an aftercooler (many blower motors do)

Your Webber carb is not blower friendly as the signal gets lost

You will need to read AFR which requires different exhaust than what you have or risk running lean and grenading the motor.

Your stock Webber calibration would run pig-rich at 6500' and is not enough CFM for a blower motor

If you want to go thru with it, don't assume it's easy. Mock it up. Make a list of everything you need and proceed accordingly.
Blower and manifold
Sandwich intercooler
Marine T-Stat housing for blower manifold
Marine Blower carb
AFR gauge
Dri-break exhaust modified for O2 sensor
New shift interupt bracket

My recommendation, vortec heads and a cam change will get you 60hp and you keep your carb and can simply read the plugs to see if you have the jetting right

 

[tpenfield]

My suggestion would be to check out the marine supercharger kits on the CP Performance or Hardin Marine websites. If you do go the SC route, it would best to start with something that is engineered for a marine engine.

Otherwise, find a new lake at/near sea level.

BTW - that is one advantage of ocean boating . . . you are always at sea level

 

[Scott06]

Thanks everyone for the responses. This is what I’m thinking... this carb’d 350 might have made 260 hp at sea level, I bet it’s closer to 200 up here. And this boat is a big fat girl.
It has a Weber 9665 AFB, jets and rods are still available. Probably 625 cfm from what little I can find. It’s was running super rich with the stock .101 mains and 70/42 rods. That’s where I’d start with a blower under it and tune from there. These little superchargers are designed for stock 350 engines and fuel systems, and I don’t understand the difference between <5000 rpm marine / automotive application?
Overdriving them makes too much heat. So 4-5psi might add 80-100 hp tops, well within the 300 hp spec of an Alpha, and enough to pull my XL size up on a ski. (6’7”). I have several sbc cores from 283 to 400, but the original engine in the boat is in great shape. And it’s in there and it’s spotless.
With regard to fuel injection, I’ve tried a couple aftermarket units in automotive applications and they really don’t add much power over a well tuned carb, but they do add drivability under 3000 rpm.
Anyway, the blower snout looks like it would hit it thermostat riser, and if so, that would require enough effort to change that it might not be worth it. But I cannot be the first one to try it?

Edit to add: several companies make an adapter plate for adding a wide band O2 sensor to wet joint exhaust. Seems like just the thing for carb tuning. Anyone tried it?

Yes on the AFR meter./O2 sensor stab in. I have moved the same meter between my 65 GTO and my boat. would not do this without it Will provide much better info than plug reading, especially in transition areas like rich/lean step up on rods, secondary kick in Etc

 

[Junkyardroad]

Hardin Marine may have the answer to the t-stat question

 

[Junkyardroad]

The Weiand blowers were discontinued after I made the post, so I used a Edelbrock E-force supercharger kit. The installation was not a direct bolt on but it is manageable for someone with experience. I had to change the aluminum lower pulley to a steel unit, grind the manifold for distributor clearance, and along the sides so it would mate with the heads properly. Also, the thermostat housing had to be offset right to clear the blower snout.
far, the timing is stock, as is the fuel mixture. It runs and idles perfectly.





I'll post updates as we get more time on it.