5.7L Rebuild Question

Hey guys. New to this forum, but I'm excited to get started.

I have an issue that I hope you guys can help me with. I have a 1990 Malibu sunsetter with a mercruiser 5.7L motor. Took it to the lake to give it a crank when it cranked right up, but immediately starting pouring water out of the port side of the block (spare me the ridicule. Needless to say I screws up).

Block is going to have to be replaced. I can handle the rebuild. I have found a 5.7 L vortec block for $150; my question is: can I rebuild that motor using the same parts from my existing motor, but will my existing heads (from a carberated motor fit the new block? I have no desire (at this point at least) to replace my existing heads, manifolds, and carb with the vortec equivilents. Will this work without any modifications or adapters?

Thanks in advance. I'll keep everybody updated with my progress.

Re: 5.7L Rebuild Question

Brndnreb said:

Hey guys. New to this forum. I have an issue that I hope you guys can help me with. I have a 1990 Malibu sunsetter with a mercruiser 5.7L motor. Took it to the lake to give it a crank when. It cranked right up, but immediately starting pouring water out of the port side of the block (spare me the ridicule. Needless to say I screws up).

Block is going to have to be replaced. I can handle the rebuild. I have found a 5.7 L vortec block for $150; my question is: can I rebuild that motor using the same parts from my existing motor, but will my existing heads (from a carberated motor fit the new block? I have no desire (at this point at least) to replace my existing heads, manifolds, and carb with the vortec equivilents. Will this work without any modifications or adapters?

Thanks in advance. I'll keep everybody updated with my progress.

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Old heads will bolt to this no problem (nobody sweats the details like the General!), although I would recommend having a machine shop look them over as they may have cracks/issues too.
Only major difference between your block and a vortec block is the timing cover, roller cam, and there is may be no provision on the vortec block for a mechanical fuel pump. The cover is no sweat, the roller cam is a bonus, and you're going to be in the market for an electric fuel pump if you don't already have one.

Re: 5.7L Rebuild Question

Didn't think about the fuel pump. Will I need an entire new pump assembly for the tank?

Also, will my existing cam work with the new block?

Re: 5.7L Rebuild Question

I can handle the rebuild. I have found a 5.7 L vortec block for $150;

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Ayuh,... You do realize that there's Alot more to buildin' a motor, than just throwing your old parts into a different block, Right,..??

Re: 5.7L Rebuild Question

uhhh...yes

Re: 5.7L Rebuild Question

Brndnreb said:

uhhh...yes

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Ok,... What kinda shape are the bores of this $150. block in,..??

Doin' what yer wantin' to do, Without machine work, will be just short of a Miracle....

Bubba's Idea will probably be Cheaper in the long haul...

Re: 5.7L Rebuild Question

Brndnreb said:

Didn't think about the fuel pump. Will I need an entire new pump assembly for the tank?

Also, will my existing cam work with the new block?

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If your old engine has a flat tappet cam, then no. If it has a roller cam them maybe, although i believe GM changed the retainers used to hold the cam in place, so it still may not fit a newer Vortec without the right retainer. Probably best to get a marine cam intended for use in your model year vortec block.

Like others have said, you're going to be piecing this one together. If this block is not in pristine shape, its going to need a trip to a machine shop for a once through, plus anything else your going to need to make it right during that trip (pistons, bearings, core plugs, gaskets, etc). Maybe wise (and cheaper) to consider the short/long block route where it's all been done, and has a warranty too.

Re: 5.7L Rebuild Question

I know my GMC pickup from 1991 had the roller cam block, with a standard flat tappet cam in it. I am sure that you can use a flat tappet cam in a roller block. The roller cam has a retainer behind the upper timing gear. On the flat tappet cam, the retainer is not used, although the mounting points are there, and the spider, and lifter retainers are not used on the flat tappet cams. Also, my 1997 5.7 Mercruiser has the fuel pump mounted on the motor. And it has the updated timing cover, etc that the Vortec blocks have. You should be able to use your engine internals in that block. That is of course if your internal parts and the block are within tolerance. I do agree with the other people, that you may just be cheaper to get the shortblock that matches your current engine, if this new block, or your parts require any machine work.

Re: 5.7L Rebuild Question

Yes your flat tappet cam and lifters will fit the vortec block but why bother, the roller vortec cam is a better cam, better yet get the marine grind roller now that you have the set up for it.

Re: 5.7L Rebuild Question

christoner2002 said:

I know my GMC pickup from 1991 had the roller cam block, with a standard flat tappet cam in it. I am sure that you can use a flat tappet cam in a roller block. The roller cam has a retainer behind the upper timing gear. On the flat tappet cam, the retainer is not used, although the mounting points are there, and the spider, and lifter retainers are not used on the flat tappet cams. Also, my 1997 5.7 Mercruiser has the fuel pump mounted on the motor. And it has the updated timing cover, etc that the Vortec blocks have. You should be able to use your engine internals in that block. That is of course if your internal parts and the block are within tolerance. I do agree with the other people, that you may just be cheaper to get the shortblock that matches your current engine, if this new block, or your parts require any machine work.

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The '91 block is a different animal. It was meant to be either way.
I would seriously question if a new vortec block would have the riffled lifter bores it would need it use flat tappet lifters. Don't know if GM would bother riffling the lifter bores anymore since roller lifters aren't supposed to rotate.

Your Mercruiser block most likely had the mechanical fuel pump boss machined after the fact. It really all depends on what the OP has for a block. If it's a truck block, then chances are the mechanical fuel pump boss is not going to be machined.

Just my 2?......

Re: 5.7L Rebuild Question

Thanks for the input guys. I'm mechanically capable of rebuilding a motor, but it would be my first rebuild piecing together parts from two different motors. I've always replaced parts that were OEM and designed for the engine I'm working on.

It would help if I could just find a bare block from the generation motor I'm repairing, but they can be hard to come by. I can find plenty of trucks that age in the junk yard, but the hardest part of the entire project would be pulling the motor of the donor truck.

As far as the components in the short side of the block; I would be using the parts from my existing motor. While I'm in there, I can inspect bearings, change piston rings, etc. Those parts are cheap.

I'm going to check out long and short blocks and consider a complete replacement. Just depends.

If I do buy a rebuilt long block; would it be worth the extra couple hundred dollars to replace the motor with a vortec mpi?

Re: 5.7L Rebuild Question

Brndnreb said:

Thanks for the input guys. I'm mechanically capable of rebuilding a motor, but it would be my first rebuild piecing together parts from two different motors. I've always replaced parts that were OEM and designed for the engine I'm working on.

It would help if I could just find a bare block from the generation motor I'm repairing, but they can be hard to come by. I can find plenty of trucks that age in the junk yard, but the hardest part of the entire project would be pulling the motor of the donor truck.

As far as the components in the short side of the block; I would be using the parts from my existing motor. While I'm in there, I can inspect bearings, change piston rings, etc. Those parts are cheap.

I'm going to check out long and short blocks and consider a complete replacement. Just depends.

If I do buy a rebuilt long block; would it be worth the extra couple hundred dollars to replace the motor with a vortec mpi?

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Assuming by saying replacing this block with a vortec MPI, you are saying a fuel injected vortec? That would be allot more then a couple hundred dollars as you would be looking for the entire U.S.C.G. approved injection system to make it work. You could get a vortec long block, then get the vortec intake manifold to use your carburetor on (allot cheaper then sourcing an entire injection system). That would be good for some extra ponies over what you have now, although you may need to eat a core charge since you don't have a complete vortec long block to send back.

Re: 5.7L Rebuild Question

Brndnreb said:

Thanks for the input guys. I'm mechanically capable of rebuilding a motor, but it would be my first rebuild piecing together parts from two different motors. I've always replaced parts that were OEM and designed for the engine I'm working on.

It would help if I could just find a bare block from the generation motor I'm repairing, but they can be hard to come by. I can find plenty of trucks that age in the junk yard, but the hardest part of the entire project would be pulling the motor of the donor truck.

As far as the components in the short side of the block; I would be using the parts from my existing motor. While I'm in there, I can inspect bearings, change piston rings, etc. Those parts are cheap.

I'm going to check out long and short blocks and consider a complete replacement. Just depends.

If I do buy a rebuilt long block; would it be worth the extra couple hundred dollars to replace the motor with a vortec mpi?

Click to expand...

I have complete 1997 5.7 liter needs rings.. new heads, HEI dist. new..