[BRUTAL64]

Originally Posted by enkeivette

So do these posts infer that 200hp is the limit for an L48?

I've taken base L48s and built them to 450 - 500 hp. Not a problem.

[94cobra69ss396]

Originally Posted by enkeivette

Stock heads, mill em down as far as they'll go and a simple garage dremel tool port job, stock valves. Any flat tappet cam, any intake. Open headers.

And what size cam will it take/ make use of?

I did some research and found that the L48 engines came from the factory with only 8:0:1 compression. They have dished pistons, 1.94/1.50-inch valves, and 76cc chambers from the factory and a hydraulic cam that has 195/202 duration at .050 and .390/.410 lift with 1.5 rocker arms. The compression will be your biggest downfall to making good horsepower. I read that if you use a 58cc head and factory thickness head gasket that it will give you 9.6:1 which would be perfect for use with pump gas and cast iron heads.

Now the question is what car is this engine going to be in, what is the intended purpose of the car, what gears ratio and trans (if auto what stall speed)? If you can give me this info I'll suggest a cam and intake for it.

[BRUTAL64]

Originally Posted by 94cobra69ss396

I did some research and found that the L48 engines came from the factory with only 8:0:1 compression. They have dished pistons, 1.94/1.50-inch valves, and 76cc chambers from the factory and a hydraulic cam that has 195/202 duration at .050 and .390/.410 lift with 1.5 rocker arms. The compression will be your biggest downfall to making good horsepower. I read that if you use a 58cc head and factory thickness head gasket that it will give you 9.6:1 which would be perfect for use with pump gas and cast iron heads.

Now the question is what car is this engine going to be in, what is the intended purpose of the car, what gears ratio and trans (if auto what stall speed)? If you can give me this info I'll suggest a cam and intake for it.

So will I. It will be interesting to see what two different engine builders come up with.

No, I'm not forgetting you Adam. But, you asked the question.

[enkeivette]

The car has no wheels or tires, no diff, no trans. In place of the trans will be a jet drive. And in place of the frame and body will be a 17' fiberglass hull. Weight... 1K lbs? Who knows.

Limitations. Stock heads, will mill them as much as possible till the edge of the valve starts to get eaten away. Will port them as much as I can with a dremel. Open headers, upswept, possibly a header muffler.

I'm cool with a solid flat cam. I believe this motor was 8.5:1 stock.

[94cobra69ss396]

Originally Posted by enkeivette

The car has no wheels or tires, no diff, no trans. In place of the trans will be a jet drive. And in place of the frame and body will be a 17' fiberglass hull. Weight... 1K lbs? Who knows.

Limitations. Stock heads, will mill them as much as possible till the edge of the valve starts to get eaten away. Will port them as much as I can with a dremel. Open headers, upswept, possibly a header muffler.

I'm cool with a solid flat cam. I believe this motor was 8.5:1 stock.

What design is the hull? Also, what jet drive is on it or going to be and what impeller? Do you know what rpm the impeller is designed for?

[enkeivette]

Haha. Wow, you're a master of all trades. Don't have the boat, just flirting with the idea. I have the SBC, but no drive either. Boat will most likely be a Tahiti.

[94cobra69ss396]

Originally Posted by enkeivette

Haha. Wow, you're a master of all trades. Don't have the boat, just flirting with the idea. I have the SBC, but no drive either. Boat will most likely be a Tahiti.

No, but my dad built an engine for his 21ft tri hull that had a jet drive and I know what mistake he made. He built a 460hp 355 SBC that made it's peak horsepower at about 7000rpms. The problem was the impeller was designed for lower rpms and the engine wouldn't rev past 5200.

What is the boat going to be used for? If it's just for going out to have fun and to ski with I would build the engine to make peak horsepower in the 5500-6000rpm range. If you just want to go as fast as you can then move it up to the 7000-7500rpm range. Unlike my dads boat that 17ft boat is light and with the V hull will get up on plane quickly.

If you just want it to ski and cruise with I would go with an Edelbrock Performer RPM intake and the following Comp Cam cam.

Part Number: CCA-12-240-4
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 1,600-5,800
Duration at 050 inch Lift: 226 int./236 exh.
Advertised Duration: 270 int./286 exh.
Valve Lift with Factory Rocker Arm Ratio: 0.480 int./0.489 exh. lift
Lobe Separation (degrees): 112
Grind Number: XM270H

It should make around 350-370hp and 400-420tq.

[BRUTAL64]

Originally Posted by enkeivette

Haha. Wow, you're a master of all trades. Don't have the boat, just flirting with the idea. I have the SBC, but no drive either. Boat will most likely be a Tahiti.

Back in the 70s we ran a 17 ft Hull with a 327 and Isky 505 cam. It would run with Big Blocks all day long. The Jet Drive was blue printed to run at about 6500 rpm.