getrdunn

iTrader: (7)

You have to make the ultimate decision regarding parts etc however on Pistons if you can find a deal on a set of forged go for it. There's cp, je, wesico, auto tek, etc. Proper clearance and build as far as I'm concerned you'd have no issues with a mild NA build. If you go cast is lean towards the KB performance Pistons. They run for ever. In regards to rings you could just use a speed pro moly coated cast. Yes there are numerous different routes you can go there as well. If you so choose to save a little money on cast Pistons and rings in my opinion that's fine but just remember to not scrimp on the exhaust valves.

Just do your research and you'll be fine. If you have a machine/speed shop nearby have them ck block, rods etc before reassembly. Over time rods stretch and may need resizing. It's relatively inexpensive.

Gannz

I always use this on every fill up. Snake oil?

87MagnumII

It keeps the alcohol from separating but can't imagine it does much as far bringing the BTU's back up. I ran the Lucas branded treatment just to keep the carb from gunking up

NHGuy

I'd get a head gasket and piston combination that nets you a .040 quench. Proper quench, fuel, timing, loading and temp go along way to staving off detonation. Then when it's together run the shorter prop first. If it makes the engine over speed go up, but not til you know you won't torque load the engine.
I have a 9.85:1 iron head forged flat top 383 that does fine that way.
I do not have a wideband either, but I just checked my plugs and they are lean, so I'm jetting up before my next run. I'm probably a little lucky/safe because my ignition has knock retard.
If your compression will end up much over 9.6:1 perhaps get some spark plugs that are one range colder. The colder plugs resist detonation.

SB

iTrader: (1)

Pre-ignition.

And I agree with what you said above.

sutphen 30

the question........Detonated piston & blew head gasket. Now what?

simple

4l whippled efi bb,say in the 580ci range. end of story.go big or go home.

ezstriper

really should used forged pistons, marine engines hard on them as under a load all the time..

Gannz

I did get the quench as close as I could with the original build. That was a few years ago and I don't recall for sure but I couldn't get it to the ideal .040 without zero decking the block and/or using expensive D dished forged pistons and/or a thinner head gasket and/or raising the compression too high. I think the thinner head gasket would have done the trick or gotten me very close but they don't make them for a marine application. I remember seeing a few references of one company making them in the past but they don't anymore. And, most people told me it wouldn't make that much of a difference since I wasn't building a high performance race engine.

Gannz

Sounds good. Wanna trade?

Gannz

All valve stems are .342 to .3425 (.343 is new)

Valve stem clearance is .002 to .0025

Heads are flat. Can’t fit a .002 feeler between a machined straight edge. Can’t even fit a .0015.

I hit the intake seats with a brass wheel on the dremel but it disintegrated before I could get to the exhausts. First pic is the one that blew up.





I stuck a flashlight into the ports with the valves seated and there was some light that came though. Not much but there was some. So, I'm thinking I just finish cleaning everything up and lap the valves and heads/valves are done. Also, since I'm running a bigger cam, going to pull the pressed in studs and replace with screw in's while heads are off.