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1986 454 Engine rebuild |
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LennyBoat 
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Joined: May-22-2023 Location: Belgium Status: Offline Points: 50 |
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 Topic: 1986 454 Engine rebuildPosted: June-05-2023 at 4:48am |
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Hi all, For our project boat, a 1986 BFN, We are rebuilding the engine. The original engine is cracked internally & externaly due to frost damage. I sourced another Mercruiser engine core with the crank & oil pan. However this is a GEN V instead of a GEN IV. The work that needs to be done on this block is quite extensive as it's in a rough shape. Before giving the go-ahead to the workshop I wanted to double check if its possible to swap a GEN IV with a GEN V core? What are the differences in these blocks? I know the old one has a 2 piece main bearing seal and the V has a 1 piece. Oil pan is different as well as timing chain cover. I can see that the old block has small cutouts in the top part of the cilinder for the valves, the newer one doesn't. not sure these are neccesary. the cilinder heads are GM hi-perf 14086188 heads.   All help would be greatly appreciated! Cheers, Lenny |
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TRBenj
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Joined: June-29-2005 Location: NWCT Status: Offline Points: 21186 |
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Posted: June-05-2023 at 8:34am |
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Some parts interchange mark iv to gen5, but some do not. Depending on what you are planning to reuse from the old, it may or may not be viable.
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 11125 |
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Posted: June-05-2023 at 8:47am |
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I'd hold off on that go ahead for a while.
It sounds like you want to use the older heads and intake on the gen 5 block. Do some reading on that because there are issues, some say it's as easy as using the Gen5 head gaskets, others will say there's more involved And you're probably dealing with a Normal Rotation Mercruiser and a Reverse Rotation PCM engine. There are other differences like the balancing method, meaning flywheels and harmonic balancers are different which may or may not affect you depending on whether you're using the Mercruiser stuff or the PCM stuff and the Gen 5 will need an electric fuel pump because there's no provision for a mechanical one I'm sure there are other things to worry about too. Unless somebody jumps in here and says "I've done this swap and here are all the details", I'd go to someplace like Offshoreonly.com and ask your question there.
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67 ski nat
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Joined: July-19-2018 Location: Santa rosa Status: Offline Points: 1194 |
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Posted: June-05-2023 at 10:06am |
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Love the 454, keep trying lenny
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LennyBoat
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Joined: May-22-2023 Location: Belgium Status: Offline Points: 50 |
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Posted: June-05-2023 at 12:35pm |
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Thank you for the replies! There is no PCM tag on the cracked engine (maybe it's been replaced before) so not sure if it's LH or RH. Online i'm reading a lot of different things. It's mated to a 1:1 velvet drive though, so its RH I guess? Not sure if there is someone with a 86BFN who could verify this?
 I'll ask on Offshoreonly as well. Would love to replace it with the same engine as original, but the problem is that these blocks are really hard to find in the EU. |
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3750 |
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Posted: June-05-2023 at 12:53pm |
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Ok, your last statement says a lot. I was going to say find any GM truck block with a Mark 4 block and you are good it does not have to be a marine block. In Europe you are probably limited to what you can find. Fel-Pro has tech bulletins showing what gasket set to use with what 454 version. GM did move some of the cooling ports that feed the heads and the gaskets need to match the block you are using.
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KENO
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Posted: June-05-2023 at 1:37pm |
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Here are a couple of pictures of the front of a BW transmission showing the pump indexing when installed for a Normal Rotation engine (LH in marine world terms) and for a Reverse Rotation engine (RH in marine world terms).
  Look at your transmission and the arrow at the top to see which way yours is set up for The original engine rotation in an 86 BFN was Reverse so the pump would have been set like the first picture unless there was an engine change done by somebody over the years.
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67 ski nat
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Posted: June-05-2023 at 1:46pm |
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Holy cow Belgium 🇧🇪. Sounds challenging
You should fly KENO out to your country for in person assistance |
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LennyBoat
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Posted: June-06-2023 at 1:09pm |
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Many thanks for the help! Herewith a picture of the trans, please excuse the engine stand blocking the view a bit. So this means this is an LH rotation engine and its not the orignal.  I also noticed that the pistons in this engine are forged (as oposed to the cast ones in the mercruiser block), and the cylinder heads have rectangular ports. Are these standard for the 454 PCM engines? (engine also came with an Edelbrock perfomer(?) intake manifold) |
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MrMcD
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Posted: June-06-2023 at 6:35pm |
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You need the casting numbers off the heads to verify chamber size and what type head they were. I think the rectangular head ports were for the high performance engines same with forged pistons. GM had a variety of big block heads and the chamber size changed which affects compression so you need to know what you have before making decisions.
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KENO
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Posted: June-06-2023 at 6:51pm |
Yep, Lenny's got a leftie It's a normal automotive(LH) rotation engine that the transmission is set up for. |
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LennyBoat
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Posted: June-09-2023 at 10:39am |
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As an alternative route: would it be possible to just buy any aftermarket GEN IV from summit racing and call it a day?
If I'm adding everything up, i'm coming pretty close to the price of a new block and rebuild kit. https://www.summitracing.com/int/parts/sdm-1-286-012-02/make/chevrolet?retaillocation=int all my original parts are still in very good condition. I do apologise for all the questions, I know some things about engine maintenance, but very little about engine rebuilding. Thanks for all your replies. Cheers, Lenny
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MrMcD
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Posted: June-09-2023 at 12:08pm |
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Since your engine is a lefty that might be the best option but consider looking for a running 454 truck engine locally and just drop it in. Might not be any in Belgium but boat engines do not get used much so even a used engine can last a very long time in a boat. Boat engines usually die due to neglect of some sort.
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LennyBoat
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Posted: July-04-2023 at 11:56am |
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I have discovered the casting number on the engine core and located an identical block available for purchase in descent condition. However, it will be necessary to bore the cylinders. The block appears to be in good shape and has undergone magnaflux testing. Just a shame that its located in the US, so shipping will cost more than the block itself.  I tried finding a block in the Netherlands, Germany, Belgium, France, Austria.... Problem is they are either completely rebuild short/longblocks (read: expensive), or the 5.3 Vortec block. 454 engine cores are nowhere to be found. I'll update once i receive the block.
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sethl
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Joined: October-09-2019 Location: Ma Status: Offline Points: 4 |
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Posted: July-12-2023 at 9:59pm |
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Gen iv fuel pump mechanical vs. gen v need electrical pump
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LennyBoat
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Posted: July-27-2023 at 11:33am |
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While I'm patiently waiting for my engine block to arrive from the U.S., I started thinking about all the other parts that might need replacement. I want to make sure that all the parts that can cause catastrophic failure, or that are hard to reach are replaced before reinstalling the engine and gearbox. I'll definitely give the water pump an overhaul, but what about the distributor, gearbox seals/hoses, engine mounts,…? Are there any “must-do” things while the engine and gearbox are out of the boat?
Cheers, |
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DayTony
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Joined: June-30-2013 Location: Salem MA Status: Offline Points: 832 |
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Posted: July-27-2023 at 12:46pm |
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lenny Hi,
On must do's i wouldn't say these are musts. more like nice to haves.
I re-built the 454 on my 88 BFN a few years back. I kept mine rev rot but with std rot you def have more off the shelf cam option so that's something to think of. just keep the overlap to a minimum.  I did not go full stock on my internals but on external upgrade i found one really nice to have was I added a crusader oil pan and a remote oil filter which increased my oil capacity and increased oil cooling. I basically got another quart out of it. It's also a great time to upgrade or clean up any of the engine wiring harness if its been bastardized over the years. Edit* also take a good look at your shaft because if its bent, now is the time to replace that or re-pack the stuffing box. |
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1988 Barefoot nautique-454
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LennyBoat wrote: