Enough compression?

[bigblockbanshee]

Went to check my ring end gaps the other night and came up with one at .016 and the other at .018 and I decided to file the lesser one and make it match the .018 gap. My piston-wall clearance is at the high end of spec too so I'm assuming the jugs were bored too big. My question is with the 22cc domes that came with the cool head I bought a few years back, will I have decent compression or should I try to find some smaller domes? I'm at about 1800' altitude also.

[12 0 Clock P I M P]

did u just have them bored???

 

ITs time for a bore and new top end my friend......with matching set of pistons....will be good for a long time then

[bigblockbanshee]

Ugh, sadly yes it's a fresh bore. It's all a brand new top end and essentially a complete rebuild that I've been in the process of doing the past 4 years. I had to find a new set of cylinders as mine were way too worn so when I got these they were stock bore and I took them to a local reputable shop and had them bore and hone them for me. That was over two years ago. Just recently I really started to get serious about getting this thing going and found out my bore size problems. I mean, what can I do? All I can hope for is that it lasts me until I can afford to buy another top end kit or more.

[Larry's Shee]

Clymers calls ring end gap to be 0.012 - 0.018, this is for stock rings . Did rings while back and wiseco gives a value X dia for gap, don't recall value. Biggest concern is piston to cylinder clearance. Take it to a machine shop and have pistons and bores measured to determine clearance. mark pistons with size and writedown cyl size so you can select fit them together . Different pistons have different clearance needs.

[bansheesrtoys]

wiseco calls for .003 for every 1 inch in diameter. so if your jugs are 3in wide then you need .012 ring end gap.

[bigblockbanshee]

So I've got too much ring end gap. I guess my outlook is that I can't do anything about it as of now. The jugs are bored and the pistons are in. I'm just hoping to get at least one good season of riding out of it before I can afford to buy new stuff. So given the fact that I have 22cc domes what is the least I could run and still get away with 93 octane? It will be advanced 4 degrees too. Again, sorry for the ignorance, I'm just really new to this stuff.

[bansheesrtoys]

you can buy new rings only , and 93 should be fine.

[Bruce_Blaine]

You can buy 20cc domes and still run pump, but I would suggest 21cc's. That's what I used to run on 93.

[Larry's Shee]

First thing I would do is burn the shop that did the machine work . Then I would still have the cyls and pistons checked because if you have to much clearance you'll have problems from the first pop. Low compression , rapid wear (because piston are cocking in bore),excessive piston slap (breaking skirts) , taking out cyls or crank. IF this is the case consider selling your brand new pistons, buy new ones THEN have them bored to match new pistons. JMHO, your results may vary !!

[bigblockbanshee]

Ok so pending the fact that I get the ring gap and piston-wall clearances brought back into spec then what about a pair of 20cc domes? I mean, I know every little bit helps but I just don't wanna yank the head back off of it for a 1cc difference. I'm planning on running no less than 93 so I'd like to get every pinch out of it that I can ya know...

 

I had my brother-in-law look at it tonight and he turned the motor over and said it felt fine to him that I just needed to get it in the frame and do a compression test on it. I'm just in a hard spot with it I guess.