L46 piston ring gap
Thread Starter
Safety Car
Joined: Jan 2008
Posts: 3,795
Likes: 434
From: Aarhus, Denmark
L46 piston ring gap
Hi,
I have a "spare" L46 engine from 1969 that I'm playing with, when I have the time for it.
I would like to make it to factory std. I'm finish with the heads, the valves and seats have been grinded and hand lapped.
Now the time have come to the piston rings, I just noticed why the engine did smoke with the previous owner, besides from very bad o-rings on both heads, then the top ring on piston 1 was cracked.
Then I took the top piston ring of piston number 3, and measured it, it was .040 in the hole, I assume that it must be from .016 to .020 right?
The block is std. bore.
Thx.
I have a "spare" L46 engine from 1969 that I'm playing with, when I have the time for it.
I would like to make it to factory std. I'm finish with the heads, the valves and seats have been grinded and hand lapped.
Now the time have come to the piston rings, I just noticed why the engine did smoke with the previous owner, besides from very bad o-rings on both heads, then the top ring on piston 1 was cracked.
Then I took the top piston ring of piston number 3, and measured it, it was .040 in the hole, I assume that it must be from .016 to .020 right?
The block is std. bore.
Thx.
Instructor
Joined: Feb 2013
Posts: 193
Likes: 2
From: Illinois
During my L48 383 build I had American Speed, Moline, IL. balance my rotating assy, check line bore and mount my new pistons. When it came time for me to gap my rings the nomenclature said .004 per inch of bore, 4.030 x .004 = .01612 end gap. I called my machinest @ American (check out their web site, 34 years nothing but SBC of all kinds) he said the information I had was out dated. If I could keep the engine under 150deg F. it would be fine but that won't happen. Instead he said .025 end gap which is around .0062 per inch of bore. not wanting to give up compression I went with .005/inch of bore.
Other comments welcome.
Other comments welcome.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
I usually shot for .022-.024 in my 350 engines or go with total seal rings. I think .027 is the limit of wear on a 350.
The question is why did that ring crack? Is there a big ridge at the top of the cylinder. If the ridge gets big enough and the motor babied, it only takes a one good romp and a ring will crack!
The question is why did that ring crack? Is there a big ridge at the top of the cylinder. If the ridge gets big enough and the motor babied, it only takes a one good romp and a ring will crack!
Last edited by hugie82; Sep 11, 2014 at 04:56 PM.
