Could you use one of the MLS headgaskets in the thickness you need to reduce the CR? I've done that with an XK engine to bring it back to 9:1 after a head skim.

 

I'll be using 0.040" Cometic head gaskets but with the 97mm bore. It's not an issue I have plenty of material to remove in the chamber. It's just a matter of getting CR correct. To reduce CR by 3 points, about 8cc which would be nearly 2 head gasket thicknesses.

 

That's a fair bit of thickness! When a friend of mine had a Chrysler 440 rebuilt he had some material milled from the piston tops to reduce compression. It was a semi bowl, like some recesses in diesel pistons. That's what his machine shop recommended, and there was plenty of meat on the piston to do that.

 

duplicate post

 

Reduce CR !!!! Most if not all of my tinkering over the years involved upping the CR!!!


An oil line parted on my 69 FJ40 Toyota Land cruiser. Lost all the crank bearings and the shaft itself!!!


I had it in pieces on a table in my shop. Here comes son. An entire FJ 40 engine aboard his hot little truck. Circa 54, a generation later. Well, it was removed for a reason! Why. Stripped it. Lower end solid.
Head a major disaster. Crazed with little cracks in the combustion chamber??? Folks blamed failure to keep the valves properly adjusted?? My idea, too much spark advance. But, why the iron head
and not the alloy pistons???


My 69 engine had closed chambers and dished pistons. The circa 54 had flat top pistons and an open chamber head.


So, the 54 lower end was topped with the 69 head. CR had to be much higher. The engine got some other stuff. Better carb, distributor
and a six in to one header. It ran great. But, insisted on premium fuel!!


Carl

 

what are you grinding away...

 

Everything that is tinted black in the picture. So above the intake valve and between exhaust and intake. Mkst seems to be around the intake valve.

 

CR will be nearly 14:1 and needs to be reduced to around 11:1

Correct Damien, Everything that is black will be removed.

Around the intake valve I will remove the black down to the level of the valve.

Around the plug I will remove enough to expose the nose of the plug better.

Between the valves I will remove the step and profile the edges.

I don't think I can remove anything from exhaust pocket on the intake valve side as this could weaken the area and cause it to crack.

 

How did you come to the conclusion on what to remove? Are you going to use a mill to do this or by hand each chamber? Looks like a lot of work! The mega squirt thing is way above my expertise...I don't even know all the acronyms you guys are using. This looks like a very cool build.

Can you tell me where to look for more info on running the Chevy Pistons?

What camshafts are you going to use?

 

I might stick them in the mill I haven't decided yet. It is a lot of work I expect 100hrs, but I'm semi retired and have plenty of time.

Camshafts are stock.

Pistols will be KB143. And larger 95mm liners. Block has been bored for new liners.

 

Warrjon
Where did you source the liners from, please? And did you have to do anything to them to make them fit, apart from machining the block? Great project, by the by.
Greg

 

I don't know, Norman Lutz is building the engine, he has done a few here in Australia. 95mm liners in a 5.3L make it 6.0L or close enough.

I lightened and balanced the conrods and I'm doing heads.

 

Could you ask him, next time you have a chance, please?
Greg

 

Will do

 

.

i prefer head gaskets as thin as possible , reason thick gaskets when hot,the gasket can start to pulsate back and forth between cylinder bores,from combustion pressure, if slightest detonation heat/pressure takes place, it can weaken gasket and may start to leak,and then blows thru.

and two gaskets is only going to aggrivate the potential!

little known fact ,when USA GM V8s were new 1949/1955, they had a thin steel sheet metal gasket(.020 thou.), problem was mass production machine work did not keep the block and head surfaces flat(requierd).

so they went to steel or copper outer layer with fibre core, worked well for many yrs, what i understand today, MLS/Cometic types work well with closed deck blocks and heads,(with near perfect flat surfaces).

Jag V12 has an open deck and floating type liners, not best for MLS gaskets.
pulsing and flexing between bores weakens seal area!
last time i looked at Cometic catalog, there V12 gaskets were not MLS but made like factory with soft core and metal surfaces. donno now!

the good head to block seal would be NO gasket just GAS filled rings around the top of liner, and a custom gasket to seal the outer edge of block,READ expensive mod!

in lew of that, some good engines use No gasket on closed decks with just rubber/nitril O-rings to seal coolant passages, and a SS ring around the cyl. bore.

if some one has unlimited money, weld a 1/2" aluminum plate to the top of aluminum block, and convert to a closed deck, and go from there! many good mods for that type, like shouldered ridge liners, and O-ring lower bore edges!

anything very good cost money, so back to square one!

Warrjon, your decsion for head chamber mods look good, and the only way to know is build it, according to your personal logic!
only time will tell, and it is no doubt it will run and surprise many here!

and you are not constricted to factory emissions for your personal vehicles.

 

and 90% of TWR and Grp44 race losses was from coolant loss and for 24hr races it seemed to happen near the end of races!

i seen it at Daytona/Rolex 24 to many times, and Sebring 12hr also!

 

warrjon, this may interest you.

Grp44 1985, V12 7L cars,IMSA.

 

Thanks Ron, I'll give it a go.

Will be using Cometic head gaskets. They are fibre with a banded ring around cylinder.

 

Mounted the Megasquirt in the 6CU case, just need to wire it up now.

 

Was the ECU jam packed before you replaced it? Looks like you put a lot more in there yet!