260 Compression Help

**Jgebhardt** · 08-17-2019, 12:30 PM

I have a 260 that I had the nikasil cylinders taken out of and steel sleeves with 280 port map installed. When the sleeves were installed, the block was decked about .010 so the pistons stick out slightly.To accommodate this, I installed 1.3mm head gaskets. I have the original heads from the 260 (part #18789-C3) on it with .050 cut off them. The compression on the motor is 125psi. I am trying to figure out how much I need to have cut off them to get my compression up to 150psi. Can anyone give me a ballpark amount that I would need to cut off? Also can someone tell me what cc the heads are based on the part number? Any help would be appreciated.

**Chaz** · 08-18-2019, 10:56 AM

Jg,
Ballparking it is what got you to the point your at in the first place. Lets throw out, kinda, sorta, slightly and fill those spots with numbers. That way you can do it once and put it right on the button.
Accurate numbers matter, otherwise it's garbage in~garbage out. Fill in the two blanks and if you have a used gasket, measure the compressed thickness.

Remember PieR~Sq 3.14 , cakes are round, and please pass the canoli' ..

Bore : 3.500
Stroke : 2.65
Exhaust port Ht. ____
Deck Ht. -.010
Head gasket Ht. .05249
Head gasket diam. 3.530
Head cc _______

**Jgebhardt** · 08-18-2019, 04:02 PM

Originally Posted by Chaz

Jg,
Ballparking it is what got you to the point your at in the first place. Lets throw out, kinda, sorta, slightly and fill those spots with numbers. That way you can do it once and put it right on the button.
Accurate numbers matter, otherwise it's garbage in~garbage out. Fill in the two blanks and if you have a used gasket, measure the compressed thickness.

Remember PieR~Sq 3.14 , cakes are round, and please pass the canoli' ..

Bore : 3.500
Stroke : 2.65
Exhaust port Ht. ____
Deck Ht. -.010
Head gasket Ht. .05249
Head gasket diam. 3.530
Head cc _______

I have no idea what cc the heads are. I know they were stock heads before I cut .050 off them. This was done a year before I had the block sleeved and decked. I don’t have any idea what the exhaust port height is either. I don’t even know how to measure it.

**KIRCHNER** · 08-20-2019, 04:57 PM

FOR the pistons to be above deck, he had to cut more than .010 off. call jay s. to get stock below deck spec, for your year 260, to gain 25 lbs you will have to cut another ,o5o imo.