Compression difference

jabber800 said:
Bob I agree with your procedure but suggest the squish band be checked at the outside edge as well as about 8 mm's in from the outer edge.
I have seen many squish band angles changed when modding heads.
Ideally I would prefer to know the overall volume of the head rather than the squish.
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Yes I agree...my squish bands are tapered on my engines as well.
I think he's going to find that someone has decked the original cylinder which should show up in a tighter squish.
I have found on these engines that .020" off the deck or head surface gives @ +20lbs, if all the porting remains the same.

Regardless of whats causing the higher compression, the real question is going to be...Run it as it is or correct the issue?

What do you think?
 
pour a liquid in each head and dump it and see the volume of liquid in a measuring cup..sure that would work.Use a light oil maybe,2 stroke oil perhaps..measure it after or weigh it.
 
Tht seems un logical to me i dunno. How would I get the oil out? And there would Always be some left in There jut like a funnel all the oil never really comes which would equal a false reading? JMO I'm not sure though
 
Just after reading a lot on heads cyls etc I've noticed a lot of guys mentioning many base gaskets and a head gasket I only have 1 base gasket installed (one piece) and on the heads there is only o rings no gasket I assumed this was right because that's the way it came apart and also my new gasket set only had o rings for the top as well not sure if this helps.

Thanks!
 
Gerryjackman said:
Tht seems un logical to me i dunno. How would I get the oil out? And there would Always be some left in There jut like a funnel all the oil never really comes which would equal a false reading? JMO I'm not sure though
Click to expand...
I mean the cylinder heads would have to be off the motor upside down to do this...lol..

here is something I found..

http://www.smokemup.com/auto_math/piston_vol.php
 
Procedure for measuring compressed head volume. (Used in calculating compression ratio)

Set sled up so the top of the cylinders are level.
Remove the head and rotate the clutch to move the piston down in the cylinder.
Line the cylinder with a light grease.
Rotate the clutch until the piston is now at top dead centre.
Remove excess grease.
Install head and torque to spec.
Remove plug.
Use a graduated syringe or burette to measure the amount of liquid that it takes to fill the cylinder head to the base of the plug hole.
That volume of fluid is your compressed head volume.
Repeat on all 3 cylinders.

Before doing this I would measure the port timing and deck height though!

And I would definitely try to find the issue with this rather than running it as is!

It would end up being a jetting nightmare at some point.
 
Ok port timing and deck height? I have no idea what that is sorry. So basically this thing is coming apart regardless? I'm still having a hard time understanding about the head volume I really don't think these heads were Altered although I'm not positive on that but both other cylinders are 120 so I'm assuming they wouldn't alter just one, I guess it would still give me a different reading if one cylinder was lower than others. I will post a pic of my heads I took when I had it apart
 
if u wanna know if it related to head its easy ...just switch 2 heads of place ...120 to 140 and the 140 to 120 ..and check back compression .if the higher number change cylinder u got something wrong with that head .......
 
Thanks guys. Ok so I was just about to tear into the top end once again and took a close look before, it's hard to explain but right in front of the head just above the p valve there is a little "tit" we'll call it it's about 2mm deep and maybe 10mm wide this is in existent on the middle cylinder ( the one I'm having issues with) basically it is a fool proof indication that the middle cylinder is definitely shaved at the top not much but it definitely is. I looked from the side and put all the head bolts in line and you can tell indefinitely the middle cylinder is lower!

I have to apologize to everyone for a bit of a run around I feel I should have noticed that earlier and therefor solved my issues.
Extra thanks to jabber I really appreciate it!

So now I'm gonna give chrome us a call I the morning and hopefully they can air freight me a new cylinder, regardless I have to tear the ol girl down so I will keep updated once I figure something out. I'm hoping this time all goes as planned!!

I cannot thank everyone enough on here you guys make the light at the end of the tunnel appear. thanks!
 
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