compression# opinion

[nitrousED]

i have 61 cc tw heads with a dss flat top piston,could somebody give me any idea on the compression? thanks

 

[Blue Thunder]

Answer these questions and I'll give you your approximate mechanical compression ratio.

Engine Bore:
Engine Stroke:
Deck clearance of block: (.035" - .045" is stock I think)
Head gasket compressed thickness: (.038" is normal)
Combustion Chamber CC: 61
Number of valve reliefs per piston:

 

[nitrousED]

thanks

30over
3.25 (331)
block hasnt been decked(stock i guess)
felpro perma blue,not sure on thickness
61 cc
2 valve reliefs,not sure on size of reliefs

 

[thumper460]

compression...

Ruffly... .010 deck and .039 gasket and 61 cc= 9.45:1, .000 deck and it is 9.7:1, using the HO out of the hole thing..-.003 = 9.78 !!

hope that helps..

Just me............................

Thumper

 

[Blue Thunder]

Going by .038" standard compressed gasket thickness, 61CC heads, 4.03" x 3.25", 2 reliefs:

deck clearance of .00" will give 10.3:1 :edit: fixed!
deck clearance of .01" will give 9.98:1
deck clearance of .02" will give 9.68:1
deck clearance of .03" will give 9.40:1
deck clearance of .04" will give 9.14:1
deck clearance of .05" will give 8.89:1

 

[thumper460]

Whoa... blue thunder... please re-check. Either your way off or my computer is!! Using a -2CC's for the valve reliefs, .010 deck, and the .039 compressed gasket, 61 CC's and 4.00 bore is.... to my computer... only 9.56 !! ?? cool?? vs the 9.8 ?? and with a .000 deck its a whopping 9.8??? not the 11.14 indicated??? Cool??

Just me..........................

Thumper

 

[Blue Thunder]

Whoa... blue thunder... please re-check. Either your way off or my computer is!! Using a -2CC's for the valve reliefs, .010 deck, and the .039 compressed gasket, 61 CC's and 4.00 bore is.... to my computer... only 9.56 !! ?? cool?? vs the 9.8 ?? and with a .000 deck its a whopping 9.8??? not the 11.14 indicated??? Cool??

Just me..........................

Thumper

Oops, I mustve entered 4.3" for the bore instead of 4.03" on the last check, (.000 deck), because that one should be 10.3:1, not 11.14:1 @.000 deck clearance.

I used my own program for calculating ratios. I entered his 4.03" bore and a gasket thickness of .038", though.
Try yours again using his 4.03" bore, not 4.0".