Replacing a bad 1987 350/5.7

[M&T]

I have a 1987 Chris Craft Scorpion 210 bowrider that has a bad power plant. I am looking for advice on using my local engine shop for a long block
(4bolt w/ F.P. hole-roller tappets- reg pistons 930.00 or 4bolt 1pc R/S-w /F.P. hole 755.00 flat tappets) instead of a marine specific application. I have read lots of theories and ideas but it always seems to be a budget based decision when the question arises marine vs domestic. My budget does not allow me to spend 5 to 7k on a marine application but I also do not want to throw away any investment I might make by replacing my power plant with something that will not or cannot handle the added abuse. Along with this choice, will replacing the camshaft (not sure what to buy for this) and bolting on my existing peripherals be all the add-ons or upgrades necessary to complete the swap?

 

[zbnutcase]

Re: Replacing a bad 1987 350/5.7

No real difference between "marine" and automotive engines other than brass core plugs (which most rebuilders use anyway, regardless of app), camshaft grind, and head gaskets. And yes, you can reuse your externals; and being an '87 (year of boat not necessarily year of engine) should be a 1-piece M/S, and centerbolt valve covers

 

[M&T]

Re: Replacing a bad 1987 350/5.7

I have shopped some cams (Comp Cans) based on the numbers I posted and have too many option with my limited knowledge to choose. Can you advise?
duration lift at 112 degrees
214-224 = 442-465 only gm cam i looked at
270-276 = 495-503
256-262 = 447-462
264-270 = 488-495
290-306 = 516-522

The shop I am using does not use marine head gaskets can I let that go?

 

[926bill]

Re: Replacing a bad 1987 350/5.7

If you go with any of the long duration grinds the idle quality will go downhill fast. I'd stick to the small 214-224 grind. I'm sure you can find the stock cam specs, internet-marine mechanic, etc. Good luck on your project.

 

[wallerus]

Re: Replacing a bad 1987 350/5.7

While you did not specify what went bad on your engine, I will assume it is not completely trashed and the only the longblock is junk. You can as an option take a longblock of the same vintage and A: Change over to brass freeze plugs ( don't forget the ones behind the bellhousing by the cam). B: swap over to marine head gaskets. C: If your marine engine has a roller cam and it is not rusty or trashed put it in the new longblock. I recommend moving over the entire valvetrain in the same positions they came from but with a roller cam this is not needed as much as a flat tappet. You may lose a sit of compression but it probably won't be too noticable.

 

[GLENN M]

Re: Replacing a bad 1987 350/5.7

280 duration 480 lift is getting up there its biggest you could go without screw in studs and guide plates,112 lobe seperation is putting max power higher in rpm range.272,264,252 are all to much duration for most boats,stick with truck or rv cam. 108 lobe seperation brings max power lower in rpm range,valve overlap maybe problem for marine use,rv cam is way to go

 

[wallerus]

Re: Replacing a bad 1987 350/5.7

By the way, new marine engines are not 4 bolt mains and are pumping out over 300 horse power so I would not worry about that.

 

[Aloysius]

Re: Replacing a bad 1987 350/5.7

By the way, new marine engines are not 4 bolt mains and are pumping out over 300 horse power so I would not worry about that.

correct! you shouldn't be spinning that thing over 5000 rpms even briefly, and probably well under 4000 rpms for for sustained operation.

If your engine is fresh water cooled, marine gaskets and water pump aren't really necessary.

 

[zbnutcase]

Re: Replacing a bad 1987 350/5.7

I have shopped some cams (Comp Cans) based on the numbers I posted and have too many option with my limited knowledge to choose. Can you advise?
duration lift at 112 degrees
214-224 = 442-465 only gm cam i looked at
270-276 = 495-503
256-262 = 447-462
264-270 = 488-495
290-306 = 516-522

The shop I am using does not use marine head gaskets can I let that go?

I would let the shop go....He can order marine gaskets just as easy as automotive ones, but if he is unwilling to do so I would have to question his integrity....

 

[M&T]

Re: Replacing a bad 1987 350/5.7

Thanks everyone for all the advice. I have a better understanding and a clearer path to completing my project.