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post #1 of 8 (permalink) Old 04-25-2018, 04:46 AM Thread Starter
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Smile OMC 460 rebuild advice

Hi all,

I have been reading on the forums a lot and some of my questions have been answered but still some are left open...

I have a pair of 1988 OMC 460 KC's (with the flat top forged TRW pistons) in my CC stinger 312 with 350hrs on them, I’m pulling them for the 3rd time out because finally I have the cash needed to rebuild them, so far I have rebuild the original carbs (holley 4160 750cfm), fitted weiand stealth intakes and made 4" trough the hull exhausts paired with the alu hardin marine manifolds. From what I have red in on the forum is to deck the engine block to 10.300” and port the D3ve heads, the question that remains is what cam and pistons I should buy knowing that I will have to bore the engine.(pitting in cyl. 7)

This is what I had in mind but I don’t know if it is all correct, and please correct me if I am wrong as don’t have any experience in rebuilding a marine 460 and this is a big expense for me :s

rebuild rotating assembly
0.030” Overbore
Keith Black KB Performance Piston and Ring Kits KB137KTM-030
Deck engine to 10.300”
Port D3VE heads
Xtreme Marine™, XM262H
billet Petronix marine distributor
New Roller timing set 72’ – 87’
New fuelpump + regulator and oil pump

Overall I am looking for a good reliable engine that performs well (+-400hp), I am hoping to achieve 60mph+ with the boat after the engines have been rebuild, mind that I live in Belgium and that I am using octane 95 minimum, sometimes also 98 😊


Thanks in advance for your replies !
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post #2 of 8 (permalink) Old 04-25-2018, 08:30 AM
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WoW dual 460's in a boat! Awesome! That is not seen a lot around here often. Congrats. You should be able to reach your goals with ease and not a lot of capital investment really with this deal at all. Especially since you have higher octane fuel available! Looks like plenty of room to work on the engines in the boat as well. Curious as to why you are pulling them for a third time? Did I read that right? If you haven't been in them how do you know you have pitting in one cylinder? Did you look in with a bore scope or something? Good luck with your build plans!

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post #3 of 8 (permalink) Old 04-25-2018, 09:29 AM
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I think you want to stay away from the '72-'87 timing chain sets as they are retarded 4 degrees as I recall.
Go with an early ('68-'70) 429 or 460 one. Or I think the later model EFI engines were okay as well.
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post #4 of 8 (permalink) Old 04-25-2018, 01:56 PM Thread Starter
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Originally Posted by away View Post
WoW dual 460's in a boat! Awesome! That is not seen a lot around here often. Congrats. You should be able to reach your goals with ease and not a lot of capital investment really with this deal at all. Especially since you have higher octane fuel available! Looks like plenty of room to work on the engines in the boat as well. Curious as to why you are pulling them for a third time? Did I read that right? If you haven't been in them how do you know you have pitting in one cylinder? Did you look in with a bore scope or something? Good luck with your build plans!
This package was the standard engine package at the time... when i just purchased the boat i had to rebuild the interior, renew the drives and transoms and i had to remove and refit the engines a couple of times, there was also no budget left to do any work on the engine other then the minor things.

During the summer last year i had manifold leak and water ended up in the chambers, had to pull the cylinder heads and noticed some pitting in cyl. nr 7 on PS engine. Now before i started to take the engine apart i did a pressure test and noticed a 2bar difference between nr. 7 and the other cylinders.
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post #5 of 8 (permalink) Old 04-25-2018, 01:59 PM Thread Starter
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Quote:
Originally Posted by 1EFF100 View Post
I think you want to stay away from the '72-'87 timing chain sets as they are retarded 4 degrees as I recall.
Go with an early ('68-'70) 429 or 460 one. Or I think the later model EFI engines were okay as well.
Thanks for the tip, I had red someting already about these early style timing sets but I was not shure if this was also applicable for my marine engine.

Anybody some suggestions on my pistons and cam ? hoping to get a 9 : 1 compression ratio.

Thanks !
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post #6 of 8 (permalink) Old 04-25-2018, 06:26 PM
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That's a super clean rig for a 1988!!

Are you sure it needs to be bored? Blow by and oil consumption??

What kind of RPM does the engines turn now?

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post #7 of 8 (permalink) Old 04-26-2018, 01:41 AM Thread Starter
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That's a super clean rig for a 1988!!

Are you sure it needs to be bored? Blow by and oil consumption??

What kind of RPM does the engines turn now?


blow by i believe yes because of the difference in compression (cylinderhaed is tight), oil consumption was not the case because the pitting was only in the way of the comprssion rings. maybe you see it on the pictures
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post #8 of 8 (permalink) Old 05-09-2018, 06:49 AM Thread Starter
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update

for those interrested here is my update on rebuilding my OMC 460 engines;

Engine core is with machine shop and had to be bored 0.040" over, later the shop will also deck the block to 10.300" (as stated by paul kane in other posts) and resuface the cylinder heads.


For cams and pistons I ordered keith black KB137KTM-040 flat top pistons along with a pair of Lunati Voodoo 10340701K (256/262 lsa 112°) cam & lifter kit

all togheter hoping to reach 9 : 1 compression ratio, I also started to port my D3ve heads, first time ever doing this, so far i am happy with the resulsts, 8 done 8 to go...
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