sleeving aluminum blocks
Seems like sleeving blocks is a common subject. In the last 30 years, I sleeved a lot of aluminum blocks, mostly outboard. Originally all outboards had cast-in sleeves. In 1985 OMC started using sleeves installed after the block was cast.(In 2.7l loop charged engines) These blocks were cast in England. Since the cylinders were really thick, big bores seemed like a good idea. So we increased the bore from 3.5" to 4". LA Sleeve made the sleeves. Straight walled, 1/16" wall thickness. Open deck block. Never had a problem with cylinders. OMC did a lot of research on sleeve installation when they made the transition. One of the things that is important is heat transfer from inside cylinder to coolant. The difference in heat transfer between "hot dropped sleeves" and pressed-in sleeves is phenomenal. They said a factor of 10. A microscopic view of the bored surface ready to accept the sleeve shows continuous peaks and valleys. A hot dropped sleeve sits on the peaks only, leaving air space between sleeve and block. Air is a good insulator. If that sleeve is pressed in with proper interference and proper lubricant, the peaks are smeared over into the valleys and create a solid surface. Thermal conductivity is much improved. Ideal interference seems to be .001" plus or minus .0002. More than that causes undesirable stress in the block. Recommended lubricant is a product called LB5000. Without lubricant aluminum will gall. If sleeves are hot dropped, they need to be seated after the block cools. For some reason, the block shrinks away from the bottom of the sleeve, usually about .003"-.004". A good, solid rap on top with a metal plate and a 2# hammer will seat it. If this is not done, it is common to see the sleeve drop in operation enough to cause head gasket leaks.
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mgb260 Jim Nichols Sequim,WA (2461 posts) Registered: 02/29/2008 08:29PM Main British Car: 1973 MGB roadster 260 Ford V8 |
Re: sleeving aluminum blocks
Larry, Long time since you've been on here. Did you ever pickup a 4.0 or 4.6 block to examine those sleeve issues? Fred has a thread on flipping them around or using inexpensive stepped GM liners.
[forum.britishv8.org] Edited 1 time(s). Last edit at 12/07/2019 01:19PM by mgb260. |
Re: sleeving aluminum blocks
It's been a while. I used a lot of thin (1/16" wall) sleeves in aluminum blocks. They tend to have too much chamfer on the bottom to suit me. Full contact at the bottom is important, so I flip the sleeve over and barely break the edge with a file. Also, a standard boring cutter leaves an angled lip at the bottom of the cut. Using a sleeve cut-off tool for boring leaves a nice square lip.
No, I have not found a 4.0 or 4.6. Not too common in central Georgia. |