Question on 502 compression ratio, octane
 

So I work at a dealer and i can get a pretty good deal on a long block 502, specs as follows and i'm wondering what octane fuel i would need to run and what you guys think? it would be going into a 1989 formula 242ss. this engine comes with edelbrock peformer rpm heads and intake--i will be in freshwater only.

Cubic Inches: 502
Liters: 8.2
Horsepower: 502 HP@5200 RPM
Torque 567 ft. lbs.@4200 RPM
Block Cast Iron, for bolt main caps
Crankshaft Forged Steel
Pistons Forged Aluminum
Compression Ratio 9.1:1
Head, Chamber Size Aluminum, 218cc
Value Size 2.02/1.60
Rocker Arms 1.7:1 Stamped Steel
Camshaft Steel Hydraulic Roller
Camshaft Lift .527” I, .544” E
Cam Duration 224° I, 234° E @ .050"
Warranty: 12 Months
Price: $5,800
my price through work would be a bit better.

What do you think??:readinghelp:

i'd run 92-93. if that engine is automotive watch out for water reversion unless you have a dry pipe system like gil or cmi.

The valve size does not look right. The 2.02/1.60 is a small block chevy valve size. You can read a lot of bad things and not so bad things about putting an automotive engine in a boat. Some people have bad luck and blow them up, and some people have no trouble at all. Most will tell you to have it marinized, which means to disassemble it and check the clearances, change if necessary, switch out the exhaust valves for Inconnel valves and some other things. I would think you ought to be able to get a pretty straight forward 502 Marine specific long block for similar money and not have the questions about the automotive engine be an issue.

everything looks like a ZZ502 except the valve size.
i would run 92 octane.


I may be wrong but the ZZ502 has brass freeze plugs correct?

I run a 540 with 9.75....93 octane. With 9.1 I'd run 89 and if I had to put 87 in it, I'd keep it below 3,500 rpms.

Valve size and cam duration...Just run dry exhaust and change the feeze plugs to brass.....You should be able to buy a marine version with your same discount......Carfull with what drive ya have also.....In a day or too you will get bombarded with info on here.....

I was under the impression that stainless valves are ok also?? I have the emi exhaust manifolds with 16" long risers, they dump the water in right at the ends of risers....still need to worry about reversion? The same company also shows another model 502 with 2.19 intake and 1.88 exhaust valves. Is this more in line with where they should be?? I have a pretty good mechanical knowledge but don't know much about these specs as far as cam lift, duration, valve size etc... Thanks for the help guys, I don't post on here much but I have gained plenty of knowledge reading all of your posts.
Bravo 1 drive by the way.

be safe run 92 oct. i also prefer dry pipes anyway.

Your weird if ya don't.....lol

2.19 and 1.88 are the correct size.
As far as reversion i would not worry about it with that exhaust. I run the same cam in my 454 and have no problems.

But dry pipes are bad azz:D

hey hows that magnum run? my buddy had a 27' t-sblocks, great boat.

I think you could easily run 89 octane with 9.1 CR and aluminum heads.

Also confuse don the specs. Valve sizes are wrong, as well as head chamber size says 218 cc.

The emi's should be fine, but you need to find out what the lobe sep is on the cam to make sure. It needs to be 110 or higher.

Lobe on the cam is 110 and you are right the heads should be 110, which is going to bring the ratio up to about 9.8:1

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Not too crazy about a used engine, don't want to buy someone's headache.

No problem I understand, but absolutely no hedaches. I finally am getting my new 555ci's finished, 2 year process!

Good luck with what ever you decision may be. Summer is almost here! Have fun this year on the water!

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Thank you By U Boy!!

No problem.