Piston Tops design

[Thad]

Planning build for the Mercruiser 470 Godzilla 4 banger, now have two engines, an Edelbrock Performer head, roller rockers and four BBC H beam rods. There are several after market 460 pistons w/ BBC pin size available, with different compression heights and piston top. Flat or dished, the dished have the full surface dish with a "rim" like a blower piston.

When the crank is ground to BBC rod journal size, will do the math and select a stroke that will result in a 1:10 compression ratio. May even have to destroke.

Question:
If the flat top pistons ran at zero deck resulted in too high of a CR, would it be better to pick a stroke where TDC was below zero deck OR run a dished pistom at zero deck? If need be for fine tuning CR how much of the "rim" of the dished piston could be machined off?

Yeah, we all march to a different drummer, wife says I got lost in the middle of a marching band.

 

[lyonsy]

nfi on qustion but if you need extra cc you could allways cust machine the pistons to a perfect match for that chamber should give beter quench to??
so what is it a 460 ford boat engine? built by murcrusier what it going in?

 

[CZLN6]

Howdy All:

I'm with Lyonsy on this one. Your best bet is to mill a dish that mirrors the shape of the combustion chambers of the Edelbrock head. Leave a .250" rim at all edges of the piston top for top ring support.

What is your CR goal for this four banger?

Adios, David

 

[Thad]

Lyonsy,
It is the Godzilla of 4 banger. Mercruiser made an alum 4 cyl block that takes off the shelf 460 pieces; head, pistons, rods, lifters, etc.
The block, crank, dizzy and cam are uniquely Mercruiser.

Imagine a 226 ci 4 banger with syrup can size pistons.

CZNL6,
Another idea, if need not enough thickness in piston is open up the combustion chamber a little. Want a CR 1:10.0 -10.5.
It is for wife's street roadster. Much like FTF's frame wise, still scribbling exterior.

Comments anyone.

 

[Anonymous]

Don't lose the squish area (and don't let it get over .042" installed height). If you mill the raised edge of a dished piston to add cc's, I'd say mill it next to the intake valve first, then the exhaust, which will retain your little squish while unshrouding the valves. Use a milling cutter with a little radius in the corners, at least (machinists seem to love sharp edges and stress-risers).

But I'm with lyonsy. Ask the manufacturer how deep you can mill into the tops of their flat-top pistons, and transfer the shape of the head pocket to the piston. And save the info, Thad!!; I scored a set of closed-chamber 429 heads to go on my 460 when I rebuild it, and figure on doing just what lyonsy has proposed with flat-top slugs.

And if you still have to lose just a little more compression? . . . add one of Mr. Singh's notorious grooves!!!

 

[Geezer 300]

A 1:10 compression ratio... dyslexic ??

 

[Thad]

Constipated!
This Nigeria food :x

 

[Anonymous]

nitro motor