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I was given a 454 chevy marine engine with a busted block and would like to build it for my street rod but all I hear is horrow stories.Since I am not a professional engine builder I need some advice and help. Is it true marine engines that come from a boat with 2 engines have different rotations and if so what effect does this have on internal parts. Also I was told to never use a truck blockwhy?


NEED HELP THANKS Wiretwister
 

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wiretwister said:
I was given a 454 chevy marine engine with a busted block and would like to build it for my street rod but all I hear is horrow stories.Since I am not a professional engine builder I need some advice and help. Is it true marine engines that come from a boat with 2 engines have different rotations and if so what effect does this have on internal parts. Also I was told to never use a truck blockwhy?


NEED HELP THANKS Wiretwister
I can give you a partial answer.

Truck blocks have a higher deck height, from the crankshaft to the head, so a car type intake is too narrow and requires spacers between the intake and head.

Engines can rotate either direction, but of course the cam has to be for the desired rotation.

Generally, that's the 2 biggest things I see.
 

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True, but the taller truck blocks only came in 366 and 427. If its a 454 its a standard deck height.

There is some debate on reverse rotation, but all evidence I've seen points to the fact that any engine installed with sterndrives (I/O) is standard rotation. Any counter-rotation props are due to the outdrive configuration.

But, like Xntrik said, its a simple cam change away from proper rotation.

The biggest concern I see is salt. If it was used in salt water and wasn't an isolated cooling system, the salt will have soaked into the block. No amount of flushing will get it out. Alone thats not a problem, but when you throw ethylene glycol coolant in there it will have trouble coexisting with salt.
 

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But, like Xntrik said, its a simple cam change away from proper rotation.
Actually,........ It's the Same Cam Rotation, regaurdless of Engine/ Crankshaft Rotation......

But,.... The Cam will be driven by Gears, rather than a Chain......
That's Where the rotation Reverses......

And,..... If the Block is Busted,.... You'll need a New 1, so the Saltwater issue is a Moot Point......
 

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Discussion Starter · #6 ·
Thanks Guys: All the response answers were well taken and helped educate me on a subject that I was in the dark on. I will record all these answers since my memory seems to be getting shorter and I think I can now feel more comfortable about building this engine. I hate to be a bother but could someone explain exactly how the camshaft controls the engine rotation.

Thanks Wiretwister
 

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the cam is like the brain of your engine.it tells the valves when to open or close. you can get one ground to reverse pattern so when you do spin the crankshaft backwards then the right valves are opening and closing when needed. i'me guessing you have a normal rotating engine. one easy way to check would be to hook power to the starter. it would have to be wound for reverse direction also i'm guessing. if no starter then check your flexplate see which side of the teeth seam mashed a bit from the starter rubbing on it.should be able to determine which way the motor spun. hope this helps.
 

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bondo said:
Actually,........ It's the Same Cam, regaurdless of Rotation......

But,.... The Cam will be driven by Gears, rather than a Chain......
That's Where the rotation Reverses......
Uh... no. Disagree. Whoever told you that wasn't even on the right track. you can't run the cam forward and the crank backward. The firing pattern doesn't reverse that way. The cam would be operating on the normal pattern of 1-8-4-3-6-5-7-2, but the crank would have the pistons moving 1-2-7-5-6-3-4-8. Can't work that way.

Its easy to find out what you seek. Just go to a parts website for marine stuff and you'll see that the timing chain is identical regardless of rotation, but the cams are different for reverse rotation.
 

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302/Z28 said:
At any rate that engine has some good parts in it like a forged crank, good rods and such. It's a shame the block is bad.

Vince
not necessarily... Most of the low-po marine engines (up to 360 hp for the BBC) had cast cranks on 2-bolt mains. Normal everyday marine chevys actually only differ from car engines in that they are built with brass freeze plugs and NPT plugs. Period. Nothing special.

Like with cars, its possible that his marine blocks are HD, like sometimes an Impala might have been fitted with a 4-bolt block, or a truck gets fitted with a 2-bolt, but for the most part the normal everyday marine sterndrives just got cast cranks and 2-bolts.
 

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wiretwister said:
Thanks Guys: All the response answers were well taken and helped educate me on a subject that I was in the dark on. I will record all these answers since my memory seems to be getting shorter and I think I can now feel more comfortable about building this engine. I hate to be a bother but could someone explain exactly how the camshaft controls the engine rotation.

Thanks Wiretwister
The cam alone doesn't, but standard firing order is 1-8-4-3-6-5-7-2. The cam opens exhaust then intake for each cylinder in order. In order to reverse rotation of the engine you have to mirror-image the cam so that the exhaust lobe leads the events again.

If you want to be technical about it, what actually controls the rotation is the starter. Its just that the rest of the engine has to be tuned for the rotation you start moving. If you put a reverse starter on a standard engine, you'll be sucking in the exhaust and spitting out the intake and it won't run.
 

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reverse rotation

curtis73 said:
Uh... no. Disagree. Whoever told you that wasn't even on the right track. you can't run the cam forward and the crank backward. The firing pattern doesn't reverse that way. The cam would be operating on the normal pattern of 1-8-4-3-6-5-7-2, but the crank would have the pistons moving 1-2-7-5-6-3-4-8. Can't work that way.

Its easy to find out what you seek. Just go to a parts website for marine stuff and you'll see that the timing chain is identical regardless of rotation, but the cams are different for reverse rotation.
if you have a reverse rotation chev v-8 motor, the firing order is; 1-5-6-3-4-2-7-8-----FOR SURE
 

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wiretwister, I build engines for a living and quite a few are marine engines. If you give me some specifics such as year and tag number off the rear of the block, I can provide additional information.

Barry
 

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curtis73 said:
that's correct, but I was just illustrating a point to show him how his theory couldn't work.
What Theory,..??....

This is a Righthanded 454,........


This is a Standard, or Lefthanded 454,..........
 

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Discussion Starter · #15 ·
topfuel said:
wiretwister, I build engines for a living and quite a few are marine engines. If you give me some specifics such as year and tag number off the rear of the block, I can provide additional information.

Barry
Sorry but I threw the block away and kept all the other parts to sell or build me a 454 engine. The one thing I do know is it has 4 bolt mains and all the heads
,crankshaft ,pistons and rods are in excellent shape
 

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Wiretwister,....

Do you have a Timing set with a Chain, or Gears,..??...

Mercruiser hasn't used Righthanded motors for Many years,....
It's Much easier to reverse the rotation of the Drive, instead of the Motor.....

The Odds are,.. Your motor was a Standard Rotation motor......

As long as you get the Right Generation of Block,...... It Doesn't have to be Marine.......
Car, or Truck will be Fine.....
 

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bondo said:
What Theory,..??....

This is a Righthanded 454,........
]
The point is not how it moves the cam, but that the cam can't be the same. If you rotate the crank in the opposite direction, and use that gear to move the cam in teh standard direction, the cam STILL can't be the same. Reverse rotaton cams HAVE to be different unless you use an entirely different crankshaft to mirror the reverse order of the cam events.

If you have a standard crank, the order in which the pistons move is fixed. A standard rotation cam has events that support that. You have flexibility in which TDC gets which event, as is the case with things like the 4/7 swap.

Reversing the crank does not support the same TDC events. For that reason, you cannot use the same cam, regardless of which way you turn it.

I stand by what I said... reverse rotation engines require a cam timed for reverse rotation. Period. The only way of changing that fact is if you use a special crankshaft with throws that support the forward cam timing events on a reversed crankshaft. No physical way of getting around that.

but... I do appreciate the pics... I didn't know of a reversed cam like that but I learned today. but, the fact remains that if you have a reverse rotation crank linked to a forward rotating cam, the cam cannot be timed like a standard cam. Reverse rotation is 1-5-6-3-4-2-7-8 and forward is 1-8-4-3-6-5-7-2. If you put them both on one and rotate, the crank is ready to fire #5 while the cam is making event for #8.
 

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bondo said:
Actually,........ It's the Same Cam Rotation, regaurdless of Engine/ Crankshaft Rotation......

But,.... The Cam will be driven by Gears, rather than a Chain......
That's Where the rotation Reverses
......

And,..... If the Block is Busted,.... You'll need a New 1, so the Saltwater issue is a Moot Point......
I never worked on a boat that had reverse gear.
I learned something. :thumbup:
 
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