Old airboat, new driver, and problems

[Duff0113]

If you go with the plan of rebuilding the junk yard motor the I would definitely change to a 383 stroker. If I were doing a basic 350 build I would pick up the motor that jegs has for sale, change cams and run it with whichever intake and carb I decide.

[StrongVet]

Yeah, I'm going to talk to my builder tomorrow. He's got my engine cleaned and bored out 0.040". Gonna make a stroker build. Planning aluminum heads, stainless headers, mild roller cam, and steel drive shaft. Just trying to decide EFI vs Holley Carb. Need reliability above all else, then performance. Thoughts?

[Duff0113]

Depends on how deep your pockets are. A carburetor is for the most part simplistic and if/when it decides to sink you don't have to worry about electronics and etc. however efi offers a wide range of tuning that is unmatched by anything else. I myself just vote for simple that way if something happens while you're out you have a better chance of fixing it to get you home.

[StrongVet]

UPDATE:
So the hull is ready and in my yard. The engine stand/cage/etc. is all welded and primed awaiting final coat. The engine. . . .

Ever since the BBC was pronounced "dead" I have been moving toward making this a stroker SBC build with reduction. But, I am at the point where I don't think that will happen without a significant investment of $$$ (I know - "welcome to airboating"). By that point I will be so upside-down in this boat that it's just not doable. However, I have found another BBC that I think I can make work and return the whole thing back to being a DD setup instead of adding reduction. So that's the direction I'm going to move. Back full circle!

So, if I go back to a DD BBC 454 setup, what's your favorite prop? I was thinking maybe a 68" 3-blade, maybe a 70"? Want to try to find one used that will work if possible. Thoughts?

[StrongVet]

So, a long-overdue update:

Motor is almost complete! Went back to a 454 DD system. Trying to add reduction and a motor both was going to put this project WAY upside down. Got into a completely rebuilt 454 with aluminum heads, torquey cam, and a new carb for $4500 built by a local performance shop that has a sterling reputation. Dynoed just over 500 ft-lb at 2900 rpm. Should be enough to push my rig using the 68" 3-blade Whirlwhind I bought. Just waiting for the engine stand and seat stand to be done - my welder had a heart attack and died mid-project, which was very sad but also created a bit of a delay. Almost there!

The old 454 DD was set up with a flex plate and my engine guy is wondering if we should go back with that or upgrade to a flywheel. Any thoughts? Also, does anyone see any need for an oil cooler up front, or just wait and see if oil temp gets too high? Original rig did not have one.

Teal season is almost upon us and the boat is not assembled yet, much to my disappointment. But we're making progress again!

[kwanjangnihm]

using the 68" 3-blade Whirlwhind I bought

did someone recommend this size prop?

[StrongVet]

I called and spoke with Whirlwind. The prop I have is a 3-blade 68" Whirlwind Super Snapper with a face that measures a bit less than 11" across. Whirlwind had suggested a 2-blade 72" Whisper Tip but it was 50% over the price as the SS and they said that either would be a good choice.

[Deano]

. . . The old 454 DD was set up with a flex plate and my engine guy is wondering if we should go back with that or upgrade to a flywheel. Any thoughts? Also, does anyone see any need for an oil cooler up front, or just wait and see if oil temp gets too high? Original rig did not have one. . .

I would think not on both counts. Someone will correct me if I'm wrong, I'm sure.

Not sure what advantage a flywheel would offer, but on the flip side it could be expected to introduce unneeded weight/mass
that would only diminish 'snap'. Many guys seek out and/or go to additional expense to acquire lighter pulleys for that reason.

An oil cooler ought not be needed if the cooling system is operating as designed/intended.
Nothing wrong with overkill, but in this case, some folks would view it as such.

- - -

Where your prop is concerned, I would have made the same choice, for the same reason(s). While a 72 Signature two blade would be the first recommended prop for a 472, a very effective substitute can be a 68 Cypress three blade. While the Cypress may be little narrower than the SS, I would still expect these two scenarios to be nearly the same.

When you get that far, please report back with how you have them pitched, I will be more than passively curious.

[oleman]

Me too

[jimbo_jwc]

My dd 500 cui caddie spins a 74 x34 wide wood up to 3000 rpm .

[StrongVet]

Not sure what advantage a flywheel would offer, but on the flip side it could be expected to introduce unneeded weight/mass
that would only diminish 'snap'. Many guys seek out and/or go to additional expense to acquire lighter pulleys for that reason.

Is this why the original build had a 350 pulley on it? I was planning to go back to a 454 pulley. I figured the larger diameter of the pulley would be advantageous. Should I be looking for a light-weight pulley? Go back to the 350 pulley?

Thanks for the help!

[SWAMPHUNTER45]

It very well could be the effort to shed weight off the rotating assembly or a desire to under drive or over drive the speed of the alternator and water pump.

[Deano]

I have no doubt at all about Swamphunter being correct with his estimations. Unless I had a trusted confirmation
from somebody who claims to know more about those specifics than I do, I would use the correct 454 OEM pieces.
They may well be the same and then again likely they are not; I don't know either way, and wouldn't claim otherwise.

From Chevytalk.Org :

06-16-11 05:05 AM - Post#2104113
In response to al72

Both the balancer and flexplate have counterweights. They are a 'standard' as set by GM when the engines were designed. The
rotating assembly is balanced using these 'standard' pieces. That way, you can replace them later without affecting overall balance.

[StrongVet]

I have no doubt at all about Swamphunter being correct with his estimations. Unless I had a trusted confirmation
from somebody who claims to know more about those specifics than I do, I would use the correct 454 OEM pieces.
They may well be the same and then again likely they are not; I don't know either way, and wouldn't claim otherwise.

Glad to hear I'm not the only one thinking I should use the parts made for the motor and not get too creative. Thanks!

Just checked on metal work - heading to paint when they have an open bay. Hopefully I'll be starting assembly in a week!


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[One Eyed Gator]

I ran a 70" 3 blade cypress on my 472 was a recommendation from chuck at airboat pro's many years ago. It ran great had good snap.

I can say that I changed my pulleys to a lightweight set, really didn't get any more rpm but had better snap. Loosing mass in a rotating assembly is a good thing unless it is need for balance.

Remember to that BBC have to options for spacing based on whether you use a long or short water pump.

[StrongVet]

I ran a 70" 3 blade cypress on my 472 was a recommendation from chuck at airboat pro's many years ago. It ran great had good snap.

I can say that I changed my pulleys to a lightweight set, really didn't get any more rpm but had better snap. Loosing mass in a rotating assembly is a good thing unless it is need for balance.

Remember to that BBC have to options for spacing based on whether you use a long or short water pump.

Good to hear. Engine builder is looking at pulleys he has around the shop - I'll see what he comes up with.

Regarding spacing, the old pulley was spaced using washers - 3 each per bolt. I am not a fan of that setup. Is there a spacer plate or bushing set that can be used instead?


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