d1mbu1b

Does anyone know if the vortec combustion chamber (64cc) on the MAG 350, 5.7 is specifically set up for squish or quench?

Is the piston only dished on one side stock or are they 'valve relieved' on both sides?

What is the piston to deck height on a stock 5.7 vortec marine engine?

I am building a 350 from a GM vortec 5.7 designed for marine use. This engine has 9.4:1 CR with iron heads already (stock)
This fact lends me to believe its a zero decked block but you never know.

I need to know if the block is ready to take advantage of the higher CRs squish can offer. (I dont want to pull the block to deck it or change pistons)

I am hoping to get close to 10:1 with aluminum AFR heads if the GM block is zero decked from the factory.

I have searched the web over and over and have not found deck height specs or even piston part number for this marine vortec 5.7 engine

Any help will be greatly appreciated. I caught the bug and 60mph provides little relief

Raylar

If you have a GM standard vortec 5.7 the stock pistons are flat top with a slight dish and a double (mirror) valve releifs. All vortec heads use the squish as part of their fast burn tecnology and I am sure standard deck height will work fine. I would recommend that you keep the total height at around .035" to .045" minimum depending on the head gasket you are using.

Ray @ Raylar

bobl

The Vortec engines run a .028 thick GM head gasket and on the ones I've measured, the piston is approximately .025 down in the hole.

Sonic30ss

I just bought two of these, from 1 800 runs new. 5.7 vortec head, roller cam, kind of a high rise duel plane intake, holley 600 cfm carb, electric fuel pump, advertised @325 hp but specs say 300 hp.The spec sheet also says to run no more than 26* total timing, that seems kind of low. I understand the Vortecs don't run as much timing as the old heads but my old motors were 34* @ 3000 rpm. Is there any room to bump it up WITHOUT risking detonation? I'll be running at least 89 octane. Dropping them in this afternoon.

tmdog

If I remember correctly total timing no more than 32* for Vortec heads. But you can bump it up to 34* and if no performance is gained, go to the standard 32*.

d1mbu1b

This works out to pistons with a 10 cc dish and a quench of 0.053, which is way on the high side from what i understand. I hear anything over 0.06 does not benefit from squish/quench. Is this true?

It Merc limits there timing advance they must be on the hairy edge of detonation at 9.4:1 CR, which seems to be consistent with the quench distance stated above.

Do "non-shim" head gaskets exist less than 0.028?

Seems as if I cannot count too much on a squish or quench effect without decking the block.

So what is a safe CR with aluminum, heads on this block with 92 octane?

Iggy

I believe the squish should be about .035" (piston to deck plus gasket thickness).