All good points and sugesstions.
As for clearances we like to use on stock GM shortblocks are slightly different than for aftermarket specialty products we can use in a block. For the stock GM type crankshafts and rods we use what we call the 2.5 sizing or .0025" on rods and .0025" on mains. The GM type crate engines can be anywhere between .001" and .003" Piston clearances and ring gaps will vary based on forged (4032 alloy) and hypereutectic cast pistons. Ring gaps can vary all over the board depending on who assembled them. We like to see .024" or so on top ring and .022" - .028" on second ring depending on piston type and induction system. On long blocks valve guide clearances should be checked and brought to normal .001"-.0015" intakes and .0015" -.00175" for exhausts. Also should check installed spring heights and verify good valve seat face to valve seat patterns and seal. There are obviously a lot of clearances that can be checked and set properly and it will depend on the original builders base part qualities, specifications, machining processes, measurements and attention to detail during block prep and assembly.

Would I take most of the better crate bbc engines I have seen properly fitted and cammed and put them in a mild 300- 420HP replacement use in more pleasure/performance hulls and run them at 4000-5000rpms in lake and river enviroments with most usage at idle and cruise rpms- YOU BET!.

Would I take some of these same crate bbc's and put them in higher speed performance boats in bigger water and ocean wave enviroments and run them with 450-550HP levels at 5000-5800 rpms for moderate sustained near WOT runs, poker runs or long up the lake blasts - HELL NO!

Best Regards,
Ray @ Raylar

Good points. The ZZ502 does come with the Felpro marine head gasket #17048. SS core.

Good points back to ya. Bob Madera has his hand in this project. One of the reasons I choose the
ZZ502 motor was for some of the good parts. Example: Forged pistons. I agree with you on clearances and other parts that fall short of the task at hand. Example: piston rings. My project motors were taken down to the bare blocks and worked up from there. Including (but not limited to) internally balancing the crankshafts.

Did I mention that Bob Madera is involved in this project?

Like the old Allstate Insurance commercial slogan- "You're in Good Hnads with Bob Madera"!

Best Regards,
Ray @ Raylar

I think that can be said of both you guys ! Ray , i really enjoy your " HIGH QUALITY " posts !! Thanks for sharing your vast knowledge of marine engines so freely !!

X2

you are appreciated RAY!!!

Ray, are the LS series built any better? Do some of the LS crate engines come down regular engine production lines?

Michael

I think the LS family of crate engines are all being built by GM in GM plants except I believe the LSX iron block variants and the crate 572's are assembled by PAS - Performance Assembly Solutions in Livonia. Very well done there by the way! Still think these have a void warranty on marine use.

These LS performance series engines are not only better numerically machined and assembled with todays better parts quality by GM engine plants, but the later superior design of the LS engine family, it's superior parts and such make them a far better engine that the older design small blocks and big blocks that are pretty much still the same as they were when released in the 50's and 60's. The supercharged versions of the LSA 550-680HP family of engines that are available in Corvettes, Cadillacs and crate engine program are hand built in a special GM state of the art high tech facility with top of the line trained engine assembly engineers as I like to call them.

The only issue with using stock out of the crate LS engines provided by GM HighPerformance is that in marine high performance most carry a warranty disclaimer not providing a warranty when used in marine applications.
The LS engines provided by GM Powertrain to engine marinizers and marine engine supply companies have OEM credit type warranties that are very involved and complicated and are not available to the end user who must rely on the engine sales company warranty which is not a GM Warranty and may be quite limited.

I like my old say'in "the best engine warranty is an engine that doesn't break!"

Best Regards,
Ray @ Raylar

Ray, you are a wealth of information.

I've always been a big block fan, but I have to say the LS is really getting my attention now. It's amazing how much power GM is getting out of the LS engines. This really shows what new technology, and fresh computer aided designs can accomplish.

Do you think the LSX 454/620 street version, or the LS 376/525 would have too much cam overlap for marine use in terms of water reversion?

Michael

Great info guy's ! Curious about a GM SB as I I have a very clean 20 Ft Formula SC that has a 305 -198 HP and I would like to install stroker in it ( 350 HP ) Kind of a sleeper . Is there any crate GM SB engines that would fit this bill that I can drop in WITHOUT tearing it apart ?

Larry