Topic: would this work ?

[brandan]

Would this work. if i put a 12hp  crank in a 11hp block  and use the stock rod. the top of the piston comes out, but the rings dont pop out. so  could i cut out the head so the piston fits,or would that be way to much pop up and make way too much heat  it would have wicked compression.



                                                                       thanks
                                                                     Maschke racin

[George Herrin]

with a little milling on the piston and a bit on the head yes it will work.

[brandan]

how much should i take off the piston ?

[George Herrin]

Well at the very minimum if you want it flush with the block, then relieve the head app. .030 for clearance. I generally run mine .020 below the block. Been alonr time since I have fooled with the setup you working with. But you generally want at least .030 clearance at top dead center.

[mowmanscott]

What if you used a 12 hp head do you still have to mill if so what?

[George Herrin]

Don't remember best put some modeling clay on top of the piston turn it over then pull head and measure thickness of clay that will tell ya how much room you got.

[mowmanscott]

Ok Ill just have to try it when I have time.

[tory]

Goerge,I see ARC sells a new rod to machine down  a 31cid AVS piston so that it is flat and I asume even with the deck.But you say you run .020 below the deck. Ive been wondering wicth would be better,there new rod and flush piston(more compresion)or there old rod and concave piston.(and perhaps manipulate it for better flow)Ive been thinking about this to macth the relief I put on the deck of the block toward the valves.Do you have any input to the subject that would help?

[George Herrin]

Well I was the one that called and asked for the longer rod, Thats what I use now no it isn't flush it allows it to be just below which will help with relieving the block. Try it out you will like it. I have built 3 so far!!!!

[mowcephus]

Which Rod number we talking about here?

[tory]

Will they tell me,when i purchase the rod, the optimum amount to take off the piston?Or is that one of your secrets :wink:

[tory]

Sorry,you answered thatearlir..020 below deck.I should pay more attention.thanx goerge

[brandan]

why do you make it .20 below , wouldnt you want more compression with it + .20 above , or would it not make that much of a difference.

[birdman_express]

why do you make it .20 below , wouldnt you want more compression with it + .20 above , or would it not make that much of a difference.

You have to give some room for that piston to move. The amount "in the hole" plus the head gasket gives you proper clearance. You can get the compression you want by milling the head.  You can run it tighter, but you have less margin for error.  Maybe that made sense... lol

[George Herrin]

I believe the new .050 longer rod is 6281, and believe it or not when under operating conditions and heat the rod will grow x amount including the piston. Thats one reason you run certain clearances everywhere. Using the copper E.C. head gaskets and the new rod I cut the piston so its a flat top this puts the piston .020 in the hole. You are not loosing but gaining compression by shaving the piston. The original rod and 28 piston is in the hole about .010. I have found in these race motors that if you run at least .030 clearance on anything in there like crank to cam lobe crank to block or valve springs in full open position you will not have an issue with them hitting under a load.