HELP??Are My Measurements off?? and a Piston Ring Question??

[BoostedBeaver]

Ok so here it goes. I have been in the process of rebuilding the car from the firewall foward and it has been some work. Now I am on the downhill slope as things start going back together and nothing else is coming apart. So tonight I went outside to do the final cleaning of my block and take my measurements for all of my clearances. I am using Weisco STD pistons. 3 of the pistons measured 3.343 and the last measured 3.344. I am shooting for .004 of PTW clearance. Next I checked the Cylinder bore and found that it was measuring anywhere from 3.347 to 3.349???? At first I was thinking it had to be human error, So I pulled out the Mic and used the 3in standard to verify it was zeroed. After that was confirmed, I set the Micrometer to 3.347 and put the Dial Bore Gauge in between the Micrometer and zeroed out the dial gauge. I preceded to again measure the cylinder bore at the top, middle, and bottom of the cylinder as well as taking the same mesurements at 90* to check for any egg shaped cylinders. Again I got one measurment that was at the bottom of number 4 that was 3.347, but every other measurment was larger anywhere from .0005 to .002. Also remember that I have one piston that is a thousands larger but .002 makes it 3.349 and that would make the one larger piston have .005 PTW. When I dropped the block off it was to be finished at 3.347 except for the one. Also it seems that every cylinder is egg shaped at one point or another. Lets take number 4 as an example. When measured in a straight line from front case to rear main, number four is top 3.3475, middle 3.3475, and bottom3.347. From these numbers it looks outstanding but you take the next measurment 90* and you get 3.3485, 3.3485, 3.34875. That makes this cylinder the worst one. SO MY QUESTION IS, is there anything that you might suggest I try. Is there an explanation as to why I would get measurements like this(besides the obvious). It was suppose to go together tommorrow but at this rate I will have to wait and take it in on monday. Also I have read that the silver color ring is the top and the black ring is number two. Is this correct. Thanks for you help and time.

 

[viperlp01]

Ya why did you not just bore the cylinder to verify a perfectly round cylinder. Also I would have measured the pistons before sending it to the machine shop especially if you don't deal with them a lot and can't trust there work. Also tell them to check cylinder roundness before you decided on the size of piston. Honestly your in a major crossroad here. You have the option of trying to sell open packaged wisecos and buy new .020 over pistons. Or find a new block and hope the cylinders are round. For the 100 bucks of getting a cylinder bored why no just bore it from the beginning.

Yes the silver ring is the top ring and the black ring is the middle.

 

[BoostedBeaver]

Thanks for the fast reply and it turns out that it is as bad as I thought. The pistons were measured prior to taking the block to the machine shop. I did not have the cylinders bored over due to the fact I was told everything looked good. I see now why everyone bores them .20 over. I thought honing it would get everything back into spec but that is what I get for thinking. Once again thanks for the input and it is much appreciated.

 

[JacksonAuto]

Honing doesn't remove enough material to bring them back to round, especially if they didn't use a plate. When you put your head on it will get even worse. You'll want to have that block re-done by a shop that knows what they're doing.

 

[BoostedBeaver]

I found out that (like stated above by Jackson Auto) that the cylinder can not become totally round again due to the fact that the Honing process only takes of a minimal amount of material to attain the recommended PTW. Since it is only a few thousands there is not enough removed to take the wall into spec and every inproffection will show. All this said, Have your block bored .20 over and be done with it. It will be round again and to you hearts desire. The only way I would use STD pistons is if you know that your Walls are in spec and would be fine with just a hone. To Jackson Racing, How would I have the block redone?? Do you mean bored over?? Just asking?? Thanks for the response and advice.

 

[JacksonAuto]

To correct it you'd need to have the block bored +.020 or whatever it takes to make the cylinders round again. Then buy pistons to fit that bore size and hone it to spec with a torque plate. Make sure the shop has a torque plate to fit a 4g63 and if you plan to use head studs make sure they install the plate with the same studs that you're going to use. If you can't find a shop, bring it on up to us. We do this everyday.