GM 454 to 502 Upgrade (Gen 4)
08-13-2020 | 05:45 PM
#11
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Joined: Mar 2004
Posts: 2,697
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From: Pa
Engine froze so apparently engine block or heads broken.
It still runs fine but you can see oil/water emulsion coming out of the air filter or crank case breather hose.
Only seen a video so far. Gonna pick the boat up in 1 week.
As it still runs fine (the guy I bought it from sent me a video, didn't ask him to crank it myself) I'm not really convinced that the block is cracked.
Not sure if these engines tend to crack the head or the block when they freeze. Freeze plugs came out and were replaced, then the current issue appeared.
That's how I bought it.
I'm new to boats and GM V8 engines so trying to identify the best/most cost efficient repair option with all my questions.
Cheers
Martin
It still runs fine but you can see oil/water emulsion coming out of the air filter or crank case breather hose.
Only seen a video so far. Gonna pick the boat up in 1 week.
As it still runs fine (the guy I bought it from sent me a video, didn't ask him to crank it myself) I'm not really convinced that the block is cracked.
Not sure if these engines tend to crack the head or the block when they freeze. Freeze plugs came out and were replaced, then the current issue appeared.
That's how I bought it.
I'm new to boats and GM V8 engines so trying to identify the best/most cost efficient repair option with all my questions.
Cheers
Martin
08-13-2020 | 09:32 PM
#12
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Joined: Jan 2003
Posts: 6,023
Likes: 1,522
From: Grand Rapids, MI
I've seen a Ford 351W push out freeze plugs and survives. I've never seen a BBC push out freeze plugs and survive. Usually they crack in the lifter/cam area without pushing out the freeze plugs. I'm sorry, but it's junk.
08-14-2020 | 10:33 PM
#13
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Joined: Sep 2001
Posts: 5,769
Likes: 151
From: tn
There is no Gen 4. It's a MkIV. But we knew what you were talking about.
There are no problems with installing MkIV heads on a Gen6 block. You just have to run Gen6 head gaskets. If you put MkIV heads on a Gen5 block, there are some issues that you need to address.
MkIV blocks will freeze crack in the lifter Valley. Can't be reliably repaired - the block is trash.
You can swap in pretty much any 502 long block. If you do a short block and reuse your heads, you should choose a MkIV or Gen 6.
If you go with a 502 block, you cannot reuse your 454 crank without rebalancing. Stick with a 502 rotating assembly.
Your Volvo 7.4 uses a regular no-frills 454 longblock. Cast crank, small rod bolts, mild cam, oval port heads. None of these are parts you should worry about jumping thru hoops to reuse.
There are things you need to do to a passenger car big block to run it in saltwater.
There are no problems with installing MkIV heads on a Gen6 block. You just have to run Gen6 head gaskets. If you put MkIV heads on a Gen5 block, there are some issues that you need to address.
MkIV blocks will freeze crack in the lifter Valley. Can't be reliably repaired - the block is trash.
You can swap in pretty much any 502 long block. If you do a short block and reuse your heads, you should choose a MkIV or Gen 6.
If you go with a 502 block, you cannot reuse your 454 crank without rebalancing. Stick with a 502 rotating assembly.
Your Volvo 7.4 uses a regular no-frills 454 longblock. Cast crank, small rod bolts, mild cam, oval port heads. None of these are parts you should worry about jumping thru hoops to reuse.
There are things you need to do to a passenger car big block to run it in saltwater.
08-15-2020 | 07:30 AM
#14
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Joined: Aug 2020
Posts: 32
Likes: 1
From: UK/Germany
There is no Gen 4. It's a MkIV. But we knew what you were talking about.
There are no problems with installing MkIV heads on a Gen6 block. You just have to run Gen6 head gaskets. If you put MkIV heads on a Gen5 block, there are some issues that you need to address.
MkIV blocks will freeze crack in the lifter Valley. Can't be reliably repaired - the block is trash.
You can swap in pretty much any 502 long block. If you do a short block and reuse your heads, you should choose a MkIV or Gen 6.
If you go with a 502 block, you cannot reuse your 454 crank without rebalancing. Stick with a 502 rotating assembly.
Your Volvo 7.4 uses a regular no-frills 454 longblock. Cast crank, small rod bolts, mild cam, oval port heads. None of these are parts you should worry about jumping thru hoops to reuse.
There are things you need to do to a passenger car big block to run it in saltwater.
There are no problems with installing MkIV heads on a Gen6 block. You just have to run Gen6 head gaskets. If you put MkIV heads on a Gen5 block, there are some issues that you need to address.
MkIV blocks will freeze crack in the lifter Valley. Can't be reliably repaired - the block is trash.
You can swap in pretty much any 502 long block. If you do a short block and reuse your heads, you should choose a MkIV or Gen 6.
If you go with a 502 block, you cannot reuse your 454 crank without rebalancing. Stick with a 502 rotating assembly.
Your Volvo 7.4 uses a regular no-frills 454 longblock. Cast crank, small rod bolts, mild cam, oval port heads. None of these are parts you should worry about jumping thru hoops to reuse.
There are things you need to do to a passenger car big block to run it in saltwater.
Once I have the boat I will strip the engine and have a look at what actually cracked.
If it is the block which means I can reuse the heads I probably then get a 502ci big block short engine (block, crankshaft, pistons, conrods). A shop is offering a refurbished marine short engine for $2400 in Germany to then carry over heads.
I reckon new flywheel is required as well but not the biggest deal I suppose.
I keep you guys posted and might require further help once I stripped the engine.
Many thanks guys for your help so far!
Looking forward to get get the engine running again.
Martin
