Large inch NA build
03-15-2023 | 04:58 PM
#21
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From: Pa
The length and weight of the boat may be a factor in what size engine you build. I thought Big cubic inch is when you're heading for 800 or so.SAR 820 EFI Marine Engine - Sonny's Racing Engines (sonnysracingengines.com)
Last edited by GPM; 03-15-2023 at 05:05 PM.
03-15-2023 | 06:52 PM
#22
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From: St. Pete Beach, FL
So we're actually talking "large inch SHORT 9.8 deck , STOCK 502 gen 6 block build" to narrow things down a little? There's been quite alot of debate/claims/information thru the years of 'how far you can bore a production gen 6. I will say this as far as boring a stock block to its "end", only do it IF it needs done because of bore wear/damage. doing it to gain 5 cubic inches isnt a great plan.
I had plans on building a pair of maxxed out 548s for my 33 scarab AVS, 13-1 or so compression, try a bunch of different heads and intakes while on my dyno on engine one, etc. Actually built engine one most the way, I had the cncd afr heads and ported promaxx heads to try. Then after dynoing several other E85 engines, saw how atrocious the BSFCS actually were even with the BSFC gain from the compression and abandoned the idea because of fuel tank size/fuel range. Sold that later, Smitty
I had plans on building a pair of maxxed out 548s for my 33 scarab AVS, 13-1 or so compression, try a bunch of different heads and intakes while on my dyno on engine one, etc. Actually built engine one most the way, I had the cncd afr heads and ported promaxx heads to try. Then after dynoing several other E85 engines, saw how atrocious the BSFCS actually were even with the BSFC gain from the compression and abandoned the idea because of fuel tank size/fuel range. Sold that later, Smitty
always love your input smitty. Really looking forward to seeing what you do with the 33.
I agree, an NA E85 motor is a bad idea in a pleasure boat due to range anxiety.
If I had to have a compression motor in a boat, I’d go with 100LL, maybe spiked with a little additive. You could bump up to 13 to 1. I’d also seriously consider EFI to lean it out a bit at cruise rpm to help your range out.
I think if you’ve got a blower motor, it would be fun to have a set of E85 carbs and a party pulley for your shoot out or poker run days.
If I was building NA it would be straight to a tall deck 632 with SR20s and a profiler sniper ram. Exhaust is still a problem, I’d love to see eickerts/lightnings vs stainless gen 2 vs CMIs dynoed at 1000hp.
03-15-2023 | 06:54 PM
#23
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From: East Tennesseee
The length and weight of the boat may be a factor in what size engine you build. I thought Big cubic inch is when you're heading for 800 or so.SAR 820 EFI Marine Engine - Sonny's Racing Engines (sonnysracingengines.com)
03-15-2023 | 06:55 PM
#24
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From: St. Pete Beach, FL
The first engine builder who was a nervous nelly and wanted me to buy the best of the best was having a stroke when we had to go 4.530 on a Big M block.thought there wasn`t eanought meat on the bone
As far as I know 4.600 is the limit ..... Dart sais
If you go 4.600 and it gets hurt you`re out of meat on the bone and you have to buy a new block no ?
Thats the issue I see with your plan Brad.
As far as I know 4.600 is the limit ..... Dart sais
If you go 4.600 and it gets hurt you`re out of meat on the bone and you have to buy a new block no ?
Thats the issue I see with your plan Brad.
4.6 is pretty standard now. The bullet boys claim they will go to 4.63.
apparently good machines like a rottler can do .005 or .01 overbores, and line to line coatings can even save pistons
03-15-2023 | 07:34 PM
#26
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From: East Tennesseee
Smitty,
So, I've got this hair-brained idea (not that I have any immediate plans) of starting with a BigM tall deck, 4.25" stroke, bored to 4.6 (565ci) with 6.7" rods. My math puts CH at 1.575". Too much? 4.375" stroke and 4.54" bore gets you to about the same displacement (566ci), and a CR of 1.3125". It would seem Molnar sells rods of just about any length, that would allow the "fixing" of any CR stack-up. Is it that simple?
Anybody ever done this? Morbid curiosity.....
Thanks. Brad.
(937)545-8991
So, I've got this hair-brained idea (not that I have any immediate plans) of starting with a BigM tall deck, 4.25" stroke, bored to 4.6 (565ci) with 6.7" rods. My math puts CH at 1.575". Too much? 4.375" stroke and 4.54" bore gets you to about the same displacement (566ci), and a CR of 1.3125". It would seem Molnar sells rods of just about any length, that would allow the "fixing" of any CR stack-up. Is it that simple?
Anybody ever done this? Morbid curiosity.....
Thanks. Brad.
(937)545-8991
03-15-2023 | 09:18 PM
#29
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From: St. Pete Beach, FL
If you put those pistons in a 10.2 how much stroke could it swing?
03-15-2023 | 10:20 PM
#30
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From: Traverse City MI
So your main question, is it feasible? Can it be done?
Short answer, it's just not worth it.
To properly build a reliable 700+hp with good torque costs just as much or more than a blower motor. Especially starting with a used up 502. So why do it?
The only reason I went NA is because my boat originally had 750hp supercat engines, it's a race boat with tractor pipes, and just "fits" the theme. Unfortunately they were extremely expensive and are less reliable than blower motors. We love them though! But we started from scratch, 572cu/in Dart blocks, lots of High end parts, dry sump, etc.
I know you are not going to believe me nor listen, people never do with offshore boating advice. The "Hope" to be able to do whatever they have convinced themselves that they want to do clouds judgement. And unfortunately, most people's budget isn't even close to their goals or dreams.
Short answer, it's just not worth it.
To properly build a reliable 700+hp with good torque costs just as much or more than a blower motor. Especially starting with a used up 502. So why do it?
The only reason I went NA is because my boat originally had 750hp supercat engines, it's a race boat with tractor pipes, and just "fits" the theme. Unfortunately they were extremely expensive and are less reliable than blower motors. We love them though! But we started from scratch, 572cu/in Dart blocks, lots of High end parts, dry sump, etc.
I know you are not going to believe me nor listen, people never do with offshore boating advice. The "Hope" to be able to do whatever they have convinced themselves that they want to do clouds judgement. And unfortunately, most people's budget isn't even close to their goals or dreams.
