tyerfryer

I am in the process of repowering my 88formula 242ss from a 330hp 454 to a 502. I would like to get some opinons on parts selection. Below is a list of part I already have and would like to find out what else I will need to finish.I am not looking for huge hp but rather a strong running engine with good power and have it be ultra reliable.
gil exhaust with stainlees risers
gm 12568782 502 short block (should i blueprint and balance it?
edelbrock 61459 oval port heads
edelbrock 7161 rpm air gap intake
crane gold roller rockers
msd 6 marine ignition
carb?
cam?
flywheel?

GoCiggie31

double check on that short block part number, This is a NON-MARINE package so you should be aware of the some of the risk in running (as is) in your heavy deep v and build accordingly.
If it was me,(and you want it super reliable) I would have a good shop that you can trust open it up re-clearance pistons, rings brgs, rebalance, linebore checking deck, change free plugs, oil pump rework with double checking pickup secure method, change cam ( i went mild with all crane 132561 marine with crane rollers 3/8 chromemoly pushrods) Extreme duty Manleys (inconnel) blah blah blah. plus plus plus and hopefully mine should be done by Christmas.

IF no one else jump in on this thread, do some searchs, LOTS of TALENT here and great advise.

Some guys on the board here has had some very good success with the zz502 in marine conversion-they do have some great components in that create 502/502 and some good prices.


good luck and keep us posted.

tyerfryer

Thanks, I look forward to hearing more advice to this project.Besides changing to brass freeze plugs is there anything else that this short block should have done to it. It is a zz502 short block but im not sure the diffrence between it and a "marine" version. Also the edelbrock heads do have the inconel valves already in them.I would think 450-500 hp seems realistic with this combo.

wompom1

FOR STARTERS:
The pistons alone need at least 002"-004" ADDITIONAL MORE clearance for marine use see www.jepistons.com for actual recommendations. keep your compression down as fuel quality can be a problem.

-make sure your cam is a marine "powerband" grind meaning torque and power are usable in your applications. Felpro s.s . laminate head gaskets

-double check the oil pump pickup to make sure it is EXTRA SECURED so as to not vibrate loose.

as stated above some folks have made the zz502 live in marine application. Do a search on subject (and below names) and spend some time.
To name a couple oso'ers, I think kidnova and Jeffrey Cheng has done what you are planning and you may p.m. them-very knoledgeable

articfriends

iTrader: (1)

I agree somewhat with what has been said but a few things I would differ on is IF you tear the short block down-check the line bore,do NOT automatically have it re-line bored. My original 2000 502 had PERFECT main alignment when I tore it down at 55 hours to take out the metric ring j/e pistons to go to slightly lower compression pistons with std rings vs the metric rings. I left main bore alone and replaced the main and rod bearings with same exact size std clevite 77's. I did have crank polished slightly which gave it about .0002 more clearence.There is alot of debate on clearences,if your going to run it N/A and are using a thermostat,the stock clearences are fine. There is zero difference in the clearences between and 450 hp 502 crate engine vs a merc 415 mpi 502,they are NOT built looser from the factory,it is pretty much just a more marine friendly cam.My merlin 2 block had clearences all over the board from the factory compared to my 502 block's clearences that were all exactly the same and fairly tight. The most important thing you need to focus on is make sure you use a cam that is built for marine use to ensure you do not have reversion,install 30 lb block bypass valves for the oiling system to make sure ALL the oil goes thru the filter and cooler,install a marine oil pan IF you can afford it,weld and safety wire or buy a oil pump pick up that bolts on and weld it on also (they do fall off). Locktight your oil pan bolts,they can loosen over time. As far as balnce if you want it really perfect or are going to buzz it at 6000 rpm's vs 5200-5400 ,have it re-balanced but I never re-balanced mine from stock,even after changing the pistons but they were almost identical in weight,it never vibrated at all,even running a blower,Smitty

Stingray69

Freeze plugs should already be brass.

Those heads:Cylinder Head, Performer RPM, Marine, Aluminum, Assembled, 110cc Chamber, 290cc Intake, Chevy, Big Block, -will make your compression a bit high, and thicker head gaskets to lower CR will make your quench amount too large. I would look at using 119cc chamber and the thin Cometic head gaskets, to keep as close to correct quench as possible without block machining.

http://store.summitracing.com/egnsea...115+4294924666

Click on the heads part number (sorry direct link not possible) and at the bottom it says:

"Notes: Designed for Marine use. The spark plug location has been moved .150 inch closer toward the bore center. Custom pistons are recommended make sure to check clearance before final assembly."

Stock pistons should be okay, but bolting heads on will create around 10:1 CR, better to aim for about 9.4/9.5:1.

"Designed for 396-502 c.i.d. big block Chevy engines, these Edelbrock cylinder heads include heavy-duty exhaust valves that provide the added durability needed for marine applications, and have one-piece, stainless steel intake valves with hardened tips and swirl-polished heads. The high-velocity flow capabilities of Edelbrock Performer RPM cylinder heads provide increased torque across a wide rpm range that's ideal for marine use. They're cast from A356 aluminum and heat-treated to T6 specs. Their oval-port heads have 110cc chambers and their rectangular port heads have 118cc chambers. Both the oval and rectangular port heads are hard-anodized to protect the aluminum in the harsh marine environments."

Rectangular port version is same size intake port, (it says), but with 118cc chambers, and should be available as marine version, (anodized, and Inconels) though not clearly listed as such. CALL THEM!

Carb: 850 Marine (sea demon) Barry Grant Mechanical, and pull off the choke.

Cam: with that exhaust, about 731 crane is hottest safe shelf cam to avert exhaust reversion; or go for a custom cam, keep duration, hence overlap down, and maybe run a bit more lift, like 610-630-ish, like the 741, but without the greater duration of it .

Pismo10

From what I have read here on OSO, MSD and ultra reliable don't go together.

camptappakeg69

More info please, just bought a 502 with msd in august.

motor has about 420 hrs, not sure when msd was put on.

seems to run pretty strong so far, only thing I noticed sometimes the idle is a little to high when then engine has been running for awhile.

thanks in advance

the duke

Not totally correct. There are 10,000 MSD's out there, and about 10 of the rest. so needless to say you hear about the MSD failures. They are the ignition of choice of NASCAR, NHRA, and most everyone else. All the boats that I know of personally, with MSD have noy had problems. I had one on my boat die. But it was 10 years old, and it cost me $75 to have MSD redo it. Not to many things in a performance boat run 10 years with no problems.

the duke

The ONLY difference in the GM long block compared to a Mercruiser long block is the cam and freeze plugs. All the rest is the same.

If you are running in salt water, you can get aluminum parts that are anodized, OR you can just make sure that you flush the engine very well everytime you use it. If you are in fresh water, its not an issue. As far as your build, the parts that you have listed, are all fine. Cam depends on how much performance you want from it. The crane 731 is a great choice for mild power. All the clearances are the same as any big block. .003 for the mains, and .0025 for the rods. Use JE/SRP pistons and set the clearance to what they say to set them to. Stock GM crank/rods for a 502 are good forged pieces, and will be fine. Carb, Holley 800-850. Blueprint is an over used word. It just means that you have checked every clearance and its right where it should be. For example if it says clearance .002 to .003, then .0025 is perfect, and whats called "blueprinted". Balance, is worth doing, as its cheap insurance.