Serious Durability Question here

[SyTy Speed Shop]

Ok, i have  a 90K mile Gen 6 454, i do not know for sure as i haven't torn down the short block yet, but im fairly certain it has a cast crank, 3/8 bolt forged rods and cast pistons.  The rods and pistons im 100% on.  The heads will keep stock valves, but everything else will be upgraded parts from Comp Cams and ARP Rocker studs and a set of 1.72 roller tip rockers since i already have them.  I'm going to have some port work done to them, nothing to drastic just some clean up and port matching and bowl work, as the heads don't do to bad in stock form if the flow numbers Ive found online are accurate.

In a HotRod mag online build they took a bone stock gen 6 454 and put it on the Dyno and it made 376HP 482TQ, with a comp cams 230/236 .547 lift on a 112 LSA it made 428HP and 507TQ, this is with a Dual plane intake and Holley 750 carb.  My Fuel Injection manifold and 90mm TB and 50lb injectors will match this with no problem once the tune is dialed in.

They also hot this same engine with a 150 shot of N2O and it made 530.  I think with the head work and a little more cam duration, lift is pretty maxed at .550 with stock pistons i can get closer to the 500HP mark, but my real question is what would be a real world limit on the cast crank and cast pistons?

I'm also looking at running the stock cast crank, upgrading the stock rods with ARP bolts and a set of speed pro hyperutectic pistons, 4.280 with a -10.50cc dome that with the stock heads and .040 head gaskets i have will give me 10.5:1CR, which is right where id like to be, and the speed pro pistons should allow more valve lift.  I can get the pistons with moly rings for 250. Am also considering a set of Scat I-Beam rods, cause after buying the ARP bolts for my stock rods and the machine work im over half way there. 

While this may not be the 700HP beast i had envisioned, and Ive realized what it really takes to build that and make it durable, id like to be as close to 500HP as i can get now, and also want it to be durable and reliable.  On a 468 with 10.0:1CR(110cc Chamber) and a 248/254 .560/.580 on a 110LSA hydraulic roller cam with stock 85-89 peanut port heads and only about 9.1:1CR due to the 117cc chambers it made 512HP 514TQ, so i was thinking about running a similar cam on Lunati VooDoo lobes and i know my heads will flow better so i can probably get alittle better power, maybe 520-525 and at this level, and keeping the RPM's under 6K i think the stock cast crank will be fine, plus according to the berkeley impeller chart, at 500-525HP i should be around 55-5700 max rpm.

Also if i were to get the tune dialed in and then run it in open loop and want to run water injection on the headers, whats the max duration you can run before you have to worry about reversion?

Is this is a good build plan?  Will i make the power i think i will?  Will this be reliable and durable?

 

[Last Mohecian]

Nice start to new thread.  Lots of info here.  I don't have any answers for you.  I am on my phone and had a couple of beers but there is one thing I am curious to see someone answer.  You asked what duration does reversion become an issue.  I thought overlap was the issue with reversion not duration.

The 5.50 lift limit on the gen 6 is the dog bone style roller lifter retainer.  You can run a higher lift cam if you switch to cross bar style lifters.

 

[Dry Dock]

Nice start to new thread.  Lots of info here.  I don't have any answers for you.  I am on my phone and had a couple of beers but there is one thing I am curious to see someone answer.  You asked what duration does reversion become an issue.  I thought overlap was the issue with reversion not duration.

The 5.50 lift limit on the gen 6 is the dog bone style roller lifter retainer.  You can run a higher lift cam if you switch to cross bar style lifters.

Mohican right on overlap ....... I have a good article but problem finding folder I filed it in.  in mean time here is Lightening Headers take on Reversion...

http://www.lightningheaders.com/tech-info(2).htm

 

[Patchman]

Sounds like a great build plan. You will find the 500HP level is a comfortable/reliable benchmark for your jet boat. Here is what i found on OSO about reversion and lobe separation.


A lobe separation angle between 104-108 will allow it to happen. A LSA between 109-112 might allow some water so mercruiser has suggested on their high per. engines that after extended periods of idling, the engine should be revved up a few times before it is shut off to clear any water.It is generally accepted that 109 degrees is the best LSA in a marine engine, but may have slightly too rough an idle for some boaters.

 

[Devilman]

I have "heard" over the years of being around these boats, that hypereutectic pistons were not a good choice in a marine engine. I couldn't remember why they had that reputation so did a little googling & found a couple write ups talking about it. From what I gather they are more prone to damage from detonation than forged, but they are ok up to around the 500 HP mark, so may be fine for your deal.

I have no personal experience with them just throwing it out there for informational purposes...

http://www.offshoreonly.com/forums/general-q/102390-piston-choice-hypereutectic-vs-forged.html

http://www.riverracer.net/forums/showthread.php?124494-Hypereutectic-pistons-in-a-jet-boat

http://forums.iboats.com/forum/engine-repair-and-maintenance/mercruiser-i-o-inboard-engines-outdrives/59002-forged-vs-hyp-pistons-in-4-3-v6

 

[Last Mohecian]

Not really a thread jack since one of the OPs questions is about reversion with headers.  It seems to me reversion would be more of an issue with through transom exhaust vs over transom with water injection.  A properly configured over transom water injection exhaust does not introduce water until a higher RPM.  Through transom typically has the tips sitting right at or even below the water line.  Can someone confirm or deny if my thinking is correct?

 

[Devilman]

I'm not sure if one would be more prone than the other, but I can confirm that if the water injection is not set up properly, especially so on an engine with an aggressive cam, that reversion can kill an engine. When I bought my boat, it had OT headers. The plumbing was not set up correctly & it was sucking water in through the exhaust the whole time. I being a noob was unaware of it. Burned a fresh stout 429 down on the third trip out, inside of the engine looked like Crisco, lol...

 

[Patchman]

OT if you have a functioning T-valve is great. But if said T-valve sticks open, or is non-existent watch out! I know from experience! :smile15:

 

[jimsplace]

How many over the transom headers, with water has anyone seen that worked properly?  There is a reason the headers have weep holes as part of the header.
Water may slow down the chrome headers from turning blue, but not for very long.

 

[SyTy Speed Shop]

How many over the transom headers, with water has anyone seen that worked properly?  There is a reason the headers have weep holes as part of the header.
Water may slow down the chrome headers from turning blue, but not for very long.

Well in my case im planning on running the EFI with O2's so ill be getting the headers ceramic coated and then header wrapping them to control the heat as best i can, as water injection and O2's dont mix.

I was mainly asking as a just in case, but the cam i am planning on running was going to be on a 110LSA, and was thinking around the same 248/254 but with alittle more lift depending on where the head flow numbers end up, but if they can make over 500 with the crappy peanut port heads and 9.0:1CR, surely i can do better with more compression and better flowing heads, maybe even get close to the 550 mark.

 

[jimsplace]

How many over the transom headers, with water has anyone seen that worked properly?  There is a reason the headers have weep holes as part of the header.
Water may slow down the chrome headers from turning blue, but not for very long.

Well in my case im planning on running the EFI with O2's so ill be getting the headers ceramic coated and then header wrapping them to control the heat as best i can, as water injection and O2's dont mix.

I was mainly asking as a just in case, but the cam i am planning on running was going to be on a 110LSA, and was thinking around the same 248/254 but with alittle more lift depending on where the head flow numbers end up, but if they can make over 500 with the crappy peanut port heads and 9.0:1CR, surely i can do better with more compression and better flowing heads, maybe even get close to the 550 mark.

Yea, I agree the O2 sensors and water don't mix.
Is the wrapping to protect the boat from the header heat?
I'm not sure why, but the ceramic coated headers cool down fairly quickly on their own, and much faster than chrome headers.

 

[SyTy Speed Shop]

How many over the transom headers, with water has anyone seen that worked properly?  There is a reason the headers have weep holes as part of the header.
Water may slow down the chrome headers from turning blue, but not for very long.

Well in my case im planning on running the EFI with O2's so ill be getting the headers ceramic coated and then header wrapping them to control the heat as best i can, as water injection and O2's dont mix.

I was mainly asking as a just in case, but the cam i am planning on running was going to be on a 110LSA, and was thinking around the same 248/254 but with alittle more lift depending on where the head flow numbers end up, but if they can make over 500 with the crappy peanut port heads and 9.0:1CR, surely i can do better with more compression and better flowing heads, maybe even get close to the 550 mark.

Yea, I agree the O2 sensors and water don't mix.
Is the wrapping to protect the boat from the header heat?
I'm not sure why, but the ceramic coated headers cool down fairly quickly on their own, and much faster than chrome headers.

Wrapping the ceramic coated headers was to help control heat for both to protect the boat and keep heat off the passengers, as I want have water injection.