Time for a new motor...

[bullsnot]

Ok, so it’s time for a new motor. Compression test confirms rings are worn.

So now I’m trying to figure out what to replace it with. There are a lot of options and and I’m not even sure what I have as clearly the motor in it is not the original.

What I do know is that it’s a 5.7 GM but haven’t found the cast code. I do not know if I have 2 or 4 bolt mains or roller cam...etc.

So with that said...what can I put in this to maximize power without sacrificing reliability or wasting money. I definitely don’t want to go backwards on power. Can I put a Vortec motor in it? Roller cam? 2 or 4 bolt main?

Thanks in advance.

 

[SpitAndDirt]

What are the OMC model numbers? Pictures are worth 1000 words. Year of boat or other OMC components?

 

[Lou C]

OK had to look at your profile to figure out what you have, 1988 5.7/Cobra, that would have come with a pre-Vortec flat tappet cam engine with mechanical fuel pump. While you can upgrade to the Vortec for a bit more HP keep in mind that the Vortec does not have an exhaust crossover in the intake manifold used for heating the choke coil on the older models with Rochester carbs. So you'd have to switch to a different carb with an electric choke (Holley or Edelbrock) and we don't know if you had a 4bbl or 2. Just switching to the Vortec means a new intake (8 bolt)
choices are:
if you want all your old stuff to fit and work (carb, mechanical fuel pump)--reman pre vortec, flat tappet, might be able to get it built with the roller cam which makes life easier with modern oils
if you want the latest cyl heads---reman or new Vortec, roller cam, and you will need a new intake manifold (8 bolt) + carb with an electric choke and electric fuel pump.

you also probably have a points distributor, if you are thinking of changing to electronic, keep in mind whatever you use it has to be able to work with the OMC ESA system or else you will have shifting problems.

My preference is for a Rochester Quadrajet and mechanical fuel pump with points distributor. If you have a Q-Jet in good shape DO NOT exchange it for a rebuilt on the 'net many are junk, get it rebuilt by a local rebuilder or do it yourself, its not a hard job.

 

[bullsnot]

Thanks Lou C and sorry for the missing info. Thought I had a signature with info.

You confirmed what I was thinking. I’m pretty convinced it’s currently got flat tappets now and is indeed pre-Vortec. I think I’m just going to replace it with the same motor but with a roller cam in it.

One side note...I did the Cobra to Merc Alpha Outdrive conversion and had to modify the ESA during that swap. Not sure though if that mod will allow me to switch to electronic ignition from points though.