Rebuild or replace?

« **on:** May 02, 2018, 10:22:44 PM »

I’m kind of stuck on this decision. My jet boat has a tired 4bolt main 350 in it. (Burns 2 qts of oil per 15ish gallons of fuel). I can’t decide rebuild the 350? Build a 383 stroker, LS swap it (I happen to have a truck 5.3 with an aluminum block) or trade the LS for a big block...
My boat is a 78. Challenger with a dominator pump.
Any input, advice, opinions, are appreciated thanks in advance!

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« **Reply #1 on:** May 02, 2018, 11:25:54 PM »

Quote from: Jasonn90 on May 02, 2018, 10:22:44 PM

I’m kind of stuck on this decision. My jet boat has a tired 4bolt main 350 in it. (Burns 2 qts of oil per 15ish gallons of fuel). I can’t decide rebuild the 350? Build a 383 stroker, LS swap it (I happen to have a truck 5.3 with an aluminum block) or trade the LS for a big block...
My boat is a 78. Challenger with a dominator pump.
Any input, advice, opinions, are appreciated thanks in advance!

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So, just to get this party started....

What do you use the boat for?

What are you looking for as far as performance?

Do you have the funds to be scaring up parts for an LS swap?

Do you have all the crap for a big block?

If you want to get on the water quick and on the cheap, build the mouse with 10:1 compression, proper cam and carburetor and let her buck. You are talking the difference of 10MPH (at the most) between the big block and the mouse and I could build that small block to 350hp for under a grand....JMHO...

GT

« **Reply #2 on:** May 03, 2018, 07:04:35 AM »

Quote from: GT Jets on May 02, 2018, 11:25:54 PM

So, just to get this party started....

What do you use the boat for?

What are you looking for as far as performance?

Do you have the funds to be scaring up parts for an LS swap?

Do you have all the crap for a big block?

If you want to get on the water quick and on the cheap, build the mouse with 10:1 compression, proper cam and carburetor and let her buck. You are talking the difference of 10MPH (at the most) between the big block and the mouse and I could build that small block to 350hp for under a grand....JMHO...

GT

Thank you GT

I use this boat as a river/lake boat. We use it to pull tubes and other water toys, usually loaded with 5 adults. but when it’s just me and the wife I’d like to keep up with our big block friends a little better.

With that said. If I did the LS swap it would probably be after this rapidly approaching boating season.

Big block it would probably need rebuild, intake, carb, front motor plate and exhaust( found used exhaust and motor plate for $300 )

Rebuilding this 350 sounds like it would be my best bet. I still eventually would need new exhaust but I can run the truck headers the previous owner put on it for now.

Any recommendations on what cam, intake, and carb to use?

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« **Reply #3 on:** May 03, 2018, 09:11:03 AM »

Quote from: Jasonn90 on May 03, 2018, 07:04:35 AM

I still eventually would need new exhaust but I can run the truck headers the previous owner put on it for now.

Any recommendations on what cam, intake, and carb to use?

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Truck headers???

Scoggin Dickey L31, $2195 delivered. New, not a remanufactured or rebuilt engine.

Add a vortec style dual plane manifold, 750 Holley, and 1.6 rockers.

325+ hp...All day long.

Still curious about those truck headers, post a pic?

Schoenfeld Sprint car headers work pretty well for 'off the shelf' headers. ,(Down side up).

https://www.speedwaymotors.com/Schoenfeld-1014L-Sprint-Car-Headers-1-3-4-3-1-2-Standard-Port,3488.html

Dan'l

« **Reply #4 on:** May 03, 2018, 09:22:20 AM »

Big block for what you want todo.... it ain’t cheap tho lol.. as I’m sure you already know!

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« **Reply #5 on:** May 03, 2018, 11:16:01 AM »

Quote from: mash on it on May 03, 2018, 09:11:03 AM

Truck headers???

Scoggin Dickey L31, $2195 delivered. New, not a remanufactured or rebuilt engine.

Add a vortec style dual plane manifold, 750 Holley, and 1.6 rockers.

325+ hp...All day long.

Still curious about those truck headers, post a pic?

Schoenfeld Sprint car headers work pretty well for 'off the shelf' headers. ,(Down side up).

https://www.speedwaymotors.com/Schoenfeld-1014L-Sprint-Car-Headers-1-3-4-3-1-2-Standard-Port,3488.html

Dan'l

Here those headers are

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« **Reply #6 on:** May 03, 2018, 11:48:35 AM »

Quote from: mash on it on May 03, 2018, 09:11:03 AM

Truck headers???

Scoggin Dickey L31, $2195 delivered. New, not a remanufactured or rebuilt engine.

Add a vortec style dual plane manifold, 750 Holley, and 1.6 rockers.

325+ hp...All day long.

Still curious about those truck headers, post a pic?

Schoenfeld Sprint car headers work pretty well for 'off the shelf' headers. ,(Down side up).

https://www.speedwaymotors.com/Schoenfeld-1014L-Sprint-Car-Headers-1-3-4-3-1-2-Standard-Port,3488.html

Dan'l

That's good chit...

A fairly well built 454 will make about 375 horse, you will need everything... Intake, carburetor, mount, exhaust, fuel pump, crank pulley, flywheel, completely redo motor mount location, which is alignment, the electrical is a little different...

I'm not trying to talk you out of anything, but that mouse is the way to go.

Looking at your picture, you have the worst carburetor on the market for a boat, I sort of dig the redneck vibe of those headers though...LOL

If you want to get on the water quick and cheap, I would build the 350 you have with some good parts. shoot for 10:1 compression, I have a few suggestions on carburetor and camshaft, but need to know how the pump is built. You don't want to hang the doors if there are no walls....LOL

GT

« **Reply #7 on:** May 03, 2018, 11:49:43 AM »

Quote from: 75 Southwind on May 03, 2018, 09:22:20 AM

Big block for what you want todo.... it ain’t cheap tho lol.. as I’m sure you already know!

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If you can't pull a tube with a small block, that's one anemic ass mouse LOL...

GT

« **Reply #8 on:** May 03, 2018, 02:30:32 PM »

Quote from: GT Jets on May 03, 2018, 11:49:43 AM

If you can't pull a tube with a small block, that's one anemic ass mouse LOL...

GT

That’s my brother in laws blown up 21ft Hawaiian back there in the pic

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« **Reply #9 on:** May 03, 2018, 02:32:25 PM »

Find out what heads are on your 350. (Casting #.'s)

You might be able to 're-ring and bearing' your short block.

Probably has 76 cc heads, at a dismal 8.5:1. Find some decent 64 cc iron or 62 cc alum heads and you'll be at 9.5 to 9.7 c/r, or so.

Summit 1102 (performer copy) or 1103 cam for 100 bux.

Use your intake and a Holley 750.

New timing chain and oil pump.

Speedway gasket kit.

Save for some sprint car headers.

Dan'l

« **Reply #10 on:** May 03, 2018, 10:05:53 PM »

My 2 cents:

Cheapest and easiest would be to build your 350. It might not give you the best performance out of these choices.

I think building the LS and big block relatively mild could give you similar performance (but better than the SBC).

Big block will probably be easier to find parts for and have potential for more power.

LS will be lighter with similar power, which is a bonus for a jet boat, and little better on gas.
just harder to find jet boat parts for. but there out there.

http://www.socaljetboats.com/projects/1970-weiman/

Steve put an LS in his boat and seems to like it (after getting all the gremlins out

).
Futs put an LS in his 18' Southwind V and has said good things about it.

If you've got the means, I like the idea of an LS. Good Luck.

« **Reply #11 on:** May 04, 2018, 09:16:03 AM »

Thank you guys for the input. I think I’m going to pull her out of the back yard this weekend if I get a chance

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« **Reply #12 on:** May 10, 2018, 10:56:27 AM »

Quote from: GT Jets on May 03, 2018, 11:48:35 AM

Looking at your picture, you have the worst carburetor on the market for a boat

GT

Why?

« **Reply #13 on:** May 10, 2018, 07:30:10 PM »

If your heads are still good I have a 350 block that was making 325-350 horsepower. Had about 5 hrs on it when a valve guide came out. I’d sell it from intake to pan.

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« **Reply #14 on:** May 11, 2018, 12:25:57 PM »

Quote from: Grimpala on May 10, 2018, 10:56:27 AM

Why?

A jet boat engine thrives on high RPM torque and the AFB type carburetor limits how much air the motor can pull in. They can be made to work better, but never work great. You would be much better off with a mechanical secondary Holley type deal. You also have to be careful with some of the Edelbrocks because they can have these teeny tiny little fuel filters in the carb top that restrict fuel flow when they are even a little dirty, causes an extreme lean condition.

GT

« **Reply #15 on:** May 12, 2018, 07:05:31 AM »

Quote from: GT Jets on May 11, 2018, 12:25:57 PM

A jet boat engine thrives on high RPM torque and the AFB type carburetor limits how much air the motor can pull in. They can be made to work better, but never work great. You would be much better off with a mechanical secondary Holley type deal. You also have to be careful with some of the Edelbrocks because they can have these teeny tiny little fuel filters in the carb top that restrict fuel flow when they are even a little dirty, causes an extreme lean condition.

GT

I guess that makes sense with that goofy air door at the secondaries. Any tips on hopping it up a little? Don't have the scratch for a holley at the moment.

« **Reply #16 on:** May 12, 2018, 10:31:44 PM »

Quote from: Grimpala on May 12, 2018, 07:05:31 AM

I guess that makes sense with that goofy air door at the secondaries. Any tips on hopping it up a little? Don't have the scratch for a holley at the moment.

Buy the strip kit, jet them up a wee bit, go down one needle size, pull the tiny fuel filters and discard, drilling the counterweight on the velocity door gains some much needed top end and allows the vacuum levels to get lower, this in turn equals more HP if the jetting can be made to match.

GT

« **Reply #17 on:** May 13, 2018, 08:25:39 PM »

Quote from: GT Jets on May 12, 2018, 10:31:44 PM

Buy the strip kit, jet them up a wee bit, go down one needle size, pull the tiny fuel filters and discard, drilling the counterweight on the velocity door gains some much needed top end and allows the vacuum levels to get lower, this in turn equals more HP if the jetting can be made to match.

GT

Any suggestions on hole size(s)/spacing/location(s) for the counterweight holes?

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« **Reply #18 on:** May 13, 2018, 09:14:33 PM »

Quote from: Grimpala on May 13, 2018, 08:25:39 PM

Any suggestions on hole size(s)/spacing/location(s) for the counterweight holes?

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It is really a trial and error thing. First thing I would do is to get a Wide open throttle vacuum reading and run a Go Pro on the upper velocity plates to witness the plates opening angle. If the carburetor is under demanded (like on a big cammed BBC) they will be WFO, but a mild small block may need that help to lower the vacuum pressure.

What's the set up?

GT

« **Reply #19 on:** May 14, 2018, 11:09:21 AM »

Quote from: GT Jets on May 13, 2018, 09:14:33 PM

It is really a trial and error thing. First thing I would do is to get a Wide open throttle vacuum reading and run a Go Pro on the upper velocity plates to witness the plates opening angle. If the carburetor is under demanded (like on a big cammed BBC) they will be WFO, but a mild small block may need that help to lower the vacuum pressure.

What's the set up?

GT

Stock BBC out of a 78 truck, peanut ports, logs and snails, Performer 2.0 dual plane and a 750 CFM Edelbrock 1407 on top of a 1" open spacer, turning an "A" impeller. It makes ~18 - 20Hg at idle and I figure ~225 HP.

« **Reply #20 on:** May 14, 2018, 09:10:44 PM »

Quote from: Grimpala on May 14, 2018, 11:09:21 AM

Stock BBC out of a 78 truck, peanut ports, logs and snails, Performer 2.0 dual plane and a 750 CFM Edelbrock 1407 on top of a 1" open spacer, turning an "A" impeller. It makes ~18 - 20Hg at idle and I figure ~225 HP.

You need the vacuum numbers at WOT... Closer to 0"hg the better.

GT

« **Reply #21 on:** May 15, 2018, 06:17:19 PM »

Quote from: GT Jets on May 14, 2018, 09:10:44 PM

You need the vacuum numbers at WOT... Closer to 0"hg the better.

GT

Going to try to hit the lake this weekend, I'll get some numbers and go from there. Thanks for the info.

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