mattz06

I will finally be getting my afr 205 heads this week, they are the 66CC version.

they are going on my forged stock cube shortblock with JE pistons that come out to same as stock compression height.

1) how much will need milled off to get 10.5-11.1 compression ratio? .030 thousandths?

2) anyone know what pushrod length should be correct after milling .030? 7.350? ( I will be using a pushrod length checker, but just wondered)

finally and most importantly,
my cam is a LG G5X2, I've been told that there would be alot of WASTE (something about blow by or something) if I leave it at 10.1 compression...
Is this true?

mattz06

almost forgot,

my JE pistons have valve pockets, will the afr's milled .030 have ptv issues with the G5x2? 232/240 595/609 112

PREDATOR-Z

I was told by a sponsor that 11:1 requires around .040 milling. He also told me that the maximum duration I'll be able to run with stock shortblock will be 224.

IMO I would double check to see if that cam would work with your pistons and the milled AFR's. Eeven unmilled I would still check to make sure.

Also for .040 he said I would need 7.35 and that it would be preferable for me to run adjustable rockers to have the right preload on the lifter and minimise a noisy valvetrain.

Tony Mamo @ AFR

iTrader: (13)

Matt,

62 cc's (apprximately an .024 flatmill) will get you right at 11 to 1 if you run a thinner .040 comedic gasket. AFR keeps them in stock. However, you will run into P/V problems with the X2 camshaft. You will have to notch your pistons which would require another cc or so to be removed from the heads assuming you still want to maintain an honest 11 to 1 ratio, due to the valve notch volume you just added. I do advise an 11 to 1 ratio with that type of camshaft to help keep good cylinder pressure...you have to compensate for the overlap in the cam. Compression is GOOD....better power, torque, throttle response, and overall efficiency.

As far as pushrod length goes, with about an .030 mill or so, 7.350 should be right in the ballpark and perhaps perfect. You need to check it with an adjustable to confirm.

Mill the heads....Your swapping them to make power....why leave some "under the table".

Crossing every "T" and dotting every "I" is how I managed to coax 480 HP out of a 346 CID engine with a mild 224 stick (a great set of heads certainly helped!)

Good luck with the build.

Regards,
Tony

PREDATOR-Z

.024 flatmil with cometic yields 11:1

So how much of a mill with a stock graphite gasket or MLS???
Cometics are around $75.00 a piece. (A bit expensive)

mattz06

thank you very much Tony. I will be posting up my afr results soon!

I am running a forged bottom end with JE pistons, they do have valve reliefs (2cc I am guessing) so it sounds like PTV clearance should be ok with .030 milled off with the g5x2

JBsC5

Great question..

Looking for an answer as well.

What would be the compression ratio with the 66cc chambers and stock GM gaskets? That seems to be the suggestion of a few tuners..

Thanks

JB