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thinking about LS swap from twin 454???
Hey guys, i have a scarab panther 30' that i have the twin 454ci motors out of it, i was going to build them up NA to make about 680ish hp.
Im a LSX guy here and prepare many LS builds, head porting and specialize with the LSA's LS9's LS7's, LS3's and so on, big with the cts-v's and zr1's. So im up in the air if i should just keep it simple and build up the original motors or swap out for the new tech....i can put together a pair of stock bottomend ls3's that make roughly the same in power, but just curious if others have done the swap and what have they seen different with their boat in performance and economy? Im sure the ls motors would use half the fuel, but will the boat be a total dog and not have enough ass behind it to get it up and going. Any insight would be great. Thanks Tony |
I have nothing of value to add but do think that would be a killer project that I’d love to see the results on. On a side note since you deal with these small blocks in cars is can the stock LC9 handle any boost good for towing in my Z71? Whats your plan for outdrives? Sounds like you’re aiming well above what a Bravo can handle but a beefier drive may need more torque than what the small blocks can give? |
those little 5.3's love boost...are you thinking of using one of the lsa take offs and adapting to the cathedral heads? that combo is very common with trucks, those blowers make a ton of instant torque right off idle.
Keep the boost like 9 or 10lbs, good tune and it will make reliable power. Only issue really is the vvt and dod with those motors, also with the flex fuel setup your injectors should be good enough to cover the bump in power too. here is some pics of a 81 camaro we are installing the lsa on a ls3 with truck accessories, we utilized this bracket by lsx innovations, very simple and great price. oops, cant post pics till i have 10 posts Tony |
I’ve never heard of using an Lsa take off (I’m just helping you get to ten post here;)) Is it fairly simple to adapt? |
A guy posted on that Facebook thing that he swapped his 454 for an LS and gained 5mph on a 21’ open bow. If you were talking 33’+ than I’d say that wouldn’t play out well but I’d think a 30’ would welcome the diet. |
I'm just curious of the 454 CI 680 ish HP recipe? |
combo would be basically 11:1, hyd roller cam (thinking something in the 234/242ish), aftermarket alum heads (ported), leaning towards dual plane intake with hp950 carb and dry exhaust should do it
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You should just stick with your BBC's and stroke them 489-496 and with the right components and CR (so you don't detonate it to death) and aim for a little more realistic power. 600 + or -. Are your current engines 330's or 365 mags. (2 or 4 bolt mains). And lastly forget about fuel consumption. |
yeah with the dual plane intake option i would say closer to mid 6's on them maybe alittle more,,,but yeah i'm not liking the fuel usage...with reworking the chambers i can make them detonation friendly.
i want to say these were 420's |
Sucken gas and haulin azz! :bong:
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Does anyone make an affordable LS exhaust manifold yet? |
I’m dying to see a 650+ 454 cu in engine live in a boat. There is someone in the swap shop and on Facebook selling a pair of LS marine engines. Think they were in a sunny. Might be a good person to talk too here it is https://www.offshoreonly.com/forums/...otors-25k.html |
Originally Posted by Crude Intentions
(Post 4656355)
I’m dying to see a 600+ 454 cu in engine live in a boat. https://www.offshoreonly.com/forums/...otors-25k.html I ran 600HP 454's for 6 yrs with no issues.(cruise@4800 RPM, 6500RPM@WFO) I then detuned them to ~550-575Hp for another 5 yrs. Fully refreshed them this summer and I run 87 octane. https://www.offshoreonly.com/forums/...otors-25k.html And Dennis's engines are a good package. |
Interesting. N/A? I mean naturally superchargers would live. If N/A please share the specs and do tell what exhaust you ran. Also I will correct but I meant to say 650+. |
Originally Posted by Alwhite00
(Post 4656354)
Does anyone make an affordable LS exhaust manifold yet? |
Originally Posted by XtremeCFM
(Post 4656317)
Hey guys, i have a scarab panther 30' that i have the twin 454ci motors out of it, i was going to build them up NA to make about 680ish hp.
Originally Posted by XtremeCFM
(Post 4656342)
combo would be basically 11:1, hyd roller cam (thinking something in the 234/242ish), aftermarket alum heads (ported), leaning towards dual plane intake with hp950 carb and dry exhaust should do it
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680 is a stout number for a NA 454/468. Your asking for almost 1.5hp per cubic inch. I doubt that setup will be very user friendly.
Most marine high performance endurance builds, are usually in the 1.0-1.2hp per ci range. I certainly dont see 680hp with that cam, dual plane intake, and marine exhaust manifolds. At least not on a dyno thats actually calibrated. |
Originally Posted by MILD THUNDER
(Post 4656412)
680 is a stout number for a NA 454/468. Your asking for almost 1.5hp per cubic inch. I doubt that setup will be very user friendly.
Most marine high performance endurance builds, are usually in the 1.0-1.2hp per ci range. I certainly dont see 680hp with that cam, dual plane intake, and marine exhaust manifolds. At least not on a dyno thats actually calibrated. |
Originally Posted by compedgemarine
(Post 4656415)
you just have to use the right correction factor and they make all you want.
that seems the way to do it here. Awesome power claims but boat is no faster than another one with a 500efi. Of course they have all the excuses in the world as to why it isn’t as fast. Lol. |
After doing the 600HP to now ~550-575HP my boat is faster with less HP. I believe this is because I brought my pk TQ and HP down and closer together. I couldn't believe how far the splits would be on a 680HP 454. When cam testing in the race boat the highest HP dyno "King" camshaft wasn't always the best or fastest in the real world boat.
Oh, and my 454's are so far 4mph faster than the 500efi's that were original to my boat. |
Were your old cams making less torque at the wot rpm than the new cams?
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Originally Posted by MILD THUNDER
(Post 4656429)
Were your old cams making less torque at the wot rpm than the new cams?
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Originally Posted by SB
(Post 4656365)
I mentioned KEM's many times many years ago. They where like $700-800 back then, Sure they are more than 1k now,but have not checked in a few years. Give'm a call.
I looked for KEM LS manifold and not seeing any. Happen to have a link. |
Originally Posted by compedgemarine
(Post 4656415)
you just have to use the right correction factor and they make all you want.
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Originally Posted by Alwhite00
(Post 4656438)
I looked for KEM LS manifold and not seeing any. Happen to have a link. KEM Equipment, Inc. |
Originally Posted by Alwhite00
(Post 4656438)
I looked for KEM LS manifold and not seeing any. Happen to have a link. |
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Originally Posted by Rookie
(Post 4656437)
Can't honestly answer that haven't dyno'd the latest combination, but I believe so. Dyno sheet says 559@5250 and 477@6500 on old setup. I'm propped to 5400 currently on my latest setup. I went from best speeds; 79-80 to 82 from the different setups.
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ExtremeCFM, with your 5 posts here its sounds like your engine(power) knowledgeable. While there may be an example or 2 of making the kind of power you want with 454's its not common and again maybe there is an odd ball out there, but in general that amount of power from a NA454 will not be user friendly. Also what outdrives are you putting with these motors? Even if you can reliably make that power...say goodbye to your bravos or TRSs.
In short, I say build the 454's to 550hp and let them eat. My personnel experience, I had a pair of 509ci 650hp(in dyno trim) engines in a 32 Sunsation. They were built right, ran awesome and lasted over 10 years, but. Honestly, yeah it was fun to blast up to 90 or so with the bigger power but, it was a pain in the ass other wise. Had to run high test, 900cfm holleys drank fuel, was a pain to dock because of idle characteristics(possible reversion) etc...etc. The boat had 496 ho's from the factory and was perfect. |
Originally Posted by jadento
(Post 4656499)
ExtremeCFM, with your 5 posts here its sounds like your engine(power) knowledgeable. While there may be an example or 2 of making the kind of power you want with 454's its not common and again maybe there is an odd ball out there, but in general that amount of power from a NA454 will not be user friendly. Also what outdrives are you putting with these motors? Even if you can reliably make that power...say goodbye to your bravos or TRSs.
In short, I say build the 454's to 550hp and let them eat. My personnel experience, I had a pair of 509ci 650hp(in dyno trim) engines in a 32 Sunsation. They were built right, ran awesome and lasted over 10 years, but. Honestly, yeah it was fun to blast up to 90 or so with the bigger power but, it was a pain in the ass other wise. Had to run high test, 900cfm holleys drank fuel, was a pain to dock because of idle characteristics(possible reversion) etc...etc. The boat had 496 ho's from the factory and was perfect. |
Originally Posted by MILD THUNDER
(Post 4656501)
what kind of top speeds were you getting with the 650s compared to stock 496's?
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Originally Posted by jadento
(Post 4656505)
Best ever 94.3 on gps. 91-92 everyday. Stock Ho's, 80-81.
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Originally Posted by MILD THUNDER
(Post 4656513)
i noticed in the thread with the guy selling those LS engines, that made 651hp, he only saw 88mph in his 32 sunsation. Seemed kinda slow for 650's in that hull.
MT, Torque? big vs. small block? Maybe he was not propped right? I turned Stock 30 inch bravos to 6K. For another comparison, Bailey had blown 502's in his Dominator similar speed as the NA509's but he turned 32's. Tired his 32's one day and while cruise was up, top speed was down. |
I think like rookie said, sometimes the dyno king number isnt always the fastest setup.
then you have the whole dyno correction factor stuff, plus many dont dyno fully dressed in marine trim. Dyno headers vs manifolds can be significant, as well as sea pump, water pump, alternator, steering pump, etc. That stuff could add up to 50+hp losses |
i didn't think 650hp na was such a unicorn for a bbc lol we've done 800+ pumpgas friendly out of bbc's,,, but obviously that wouldn't work well in a marine application, too much loss in bottomend.
But anyways to my concerns,,,i'm going to just stick to the 454's,,,i think the ls's wouldn't have torque downlow to match the bb's unless i match the same ci, which then my build would be costly. I think i have to stop listening to my guys here that want to swap the world with LS lol |
Originally Posted by XtremeCFM
(Post 4656530)
i didn't think 650hp na was such a unicorn for a bbc lol we've done 800+ pumpgas friendly out of bbc's,,, but obviously that wouldn't work well in a marine application, too much loss in bottomend.
But anyways to my concerns,,,i'm going to just stick to the 454's,,,i think the ls's wouldn't have torque downlow to match the bb's unless i match the same ci, which then my build would be costly. I think i have to stop listening to my guys here that want to swap the world with LS lol John |
Originally Posted by XtremeCFM
(Post 4656530)
i didn't think 650hp na was such a unicorn for a bbc lol we've done 800+ pumpgas friendly out of bbc's,,, but obviously that wouldn't work well in a marine application, too much loss in bottomend.
But anyways to my concerns,,,i'm going to just stick to the 454's,,,i think the ls's wouldn't have torque downlow to match the bb's unless i match the same ci, which then my build would be costly. I think i have to stop listening to my guys here that want to swap the world with LS lol |
Originally Posted by XtremeCFM
(Post 4656530)
i didn't think 650hp na was such a unicorn for a bbc lol we've done 800+ pumpgas friendly out of bbc's,,, but obviously that wouldn't work well in a marine application, too much loss in bottomend.
But anyways to my concerns,,,i'm going to just stick to the 454's,,,i think the ls's wouldn't have torque downlow to match the bb's unless i match the same ci, which then my build would be costly. I think i have to stop listening to my guys here that want to swap the world with LS lol the issue isnt isn’t the ability to build it. The issue is making it live in a boat. Plenty of high horsepower apps out there for cars but making them last in a boat is a different animal. Water in exhaust, docking where you’re in and out of gear at low speeds, always at 3500-4500 rpm. Very different than an automotive setup. |
well aware of the constant abuse of a marine app...done many of them.
I actually think that a NA setup holds up far better then a boosted one...that constant wot for 5 to 10 min straight under boost is pure torture,,,god forbid you have a slight fuel distribution, its going to eat a piston real fast. i plan on running a dry exhaust setup in the boat also |
Boosted is by far the more reliable and safer setup once you get into the 600+hp range. Nobody sells more hi performance marine engines than mercury, and they know this.
biggest weaklink in a marine engine is the valvetrain. Boosted engines dont need radical valvetrains to make big power. |
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