problems with new block

[Anonymous]

I just got my short block back from the machine shop and I discovered a small air pocket hole in the number 6 cylinder wall about half way down the bore. It looks to be about .015 to .020 wide and is not very deep. (does not go through cylinder wall. Has anyone else had this problem and how serious is it? The block is already bored .060.

 

[godheadcustoms]

Did the machine shop sonic check/pressure test the block? If not, go back and have them check the cylinder wall thickness and strength. Better to find out what's up now rather than out on the highway.

 

[Anonymous]

Not sure what they did to it at the machine shop but I will ask tomorrow.

 

[xctasy]

How much money you got?

1. Sleave the block with some after market diesel liners. Get the sleave set, and take it back to the 3.632" bore all 1993 to date Aussie Falcons use. The ones from 1998 on wards a very shallow, about 370 thou shallower. The rods can then be 370 thou longer.


2. Some Aussies can send you some new ACL 4.0 pistons. They are very cheap!


3. Then add some 302 conrods, with the cranks fillet radius welded up to centre the narrower V8 rod. Do this on each of the six journals using long run downhand welding. The crank then has to be re machined with a 30 thou fillet radius.

This way, you'll have the facility fore endless rebores to 3.68, using turbo spec pistons which are bullet proof, and you'll get the betterkind of longer V8 con-rod to suit.

Capacity is 194 cubes, 3185 cc's.

The longer rods gain about 4% for power, while the loss of a potential 12 cubic inches on the +60 thou 206 will be restored with the longer rods.

If origniality is important, it will give you a practically unless lifespan on the existing block.

The high initial expense will be paid by will years of failfull service.

The option of getting another block may be cheaper, but it you have to think over the year, and the transmission options you have.

Think it over.

 

[Anonymous]

Not that much money. But that is something to think about. I already have about $1600 in the short block alone with some parts and labor. The problem could have been avoided all together if my machinist had noticed it in the first place.

 

[MustangSix]

Have them sleeve and rebore that one cylinder. Cost should be about $60-75. I had the same problem with the crossflow. Sleeves are a commonly done repair and are at least as durable as the original cylinder, if not more so.

Those large pits are caused by porosity. It may or may not go all the way thru the wall, but if it does, it will cause major problems. Better to fix it now.

 

[Anonymous]

Thanks for all of you advise. I will look in to that option.

 

[Anonymous]

If the hole does not go all the way through the cylinder wall would blow-by or compression loss cause problems?. That is assuming the sonic and pressure check is ok.

 

[xctasy]

No. The sonic and pressure test are only guidelines. Under the pressure of combustion, the thin walls can bow. The car can suffer cold start leakage and other problems.

Sleaving is the only option. If you are forced to, you can run just one smaller sleaved cylinder on one cylinder if cash is tight. I've seen it done on very valuable engines, and as long as the pistons weights are the same, you can get away with some variances.

One of the best ones I saw was an Olds 403 with a 30 thou overbore on one cylinder, and stock size on all the others.

 

[MustangSix]

If you are forced to, you can run just one smaller sleaved cylinder on one cylinder if cash is tight.

No need to do that, since they can bore the sleeve to match the other cylinders. It has to be bored anyway since the sleeves are manufactrued to a nominal dimension. Sleeves are pretty thick, usually .100 - .125" wall. The remaining cylinder wall in the block only serves to locate sleeve. And often the sleeve material is better than the parent material in the block.

In the early 70's when I was working in a machine shop, one of the most commonly sleeved engines was the alloy block Vega. The cylinder bores were silicon impregnated and extremely hard (like todays Northstar), but only to a depth of a hundredth of an inch or so. Once wear exceeded that, the alloy cylinder would go very quickly. It was not possible to overbore a silicon alloy block.

We would install iron liners in all the cylinders by boring away almost all the alloy cylinder, leaving only enough to support the sleeve. Once pressed in, it bacame an integral part of the block with better wear characteristics than the original.. We often only did the affected cylinder, but on a couple of occasions we replaced all the cylinders.