Guest Posted November 26, 2000 Share Posted November 26, 2000 I'm rebuilding my 455 but I think I have a problem. All of my cylinder bores are between 4.3430 and 4.3445. I got a set of TRW forged aluminum pistons from a guy that say L2353 .030 on the top of the pistons. I took that to mean that they were for a .030 bore. But when I put them in the sleeves, there seems to be alot of play. I measured the piston diameter and that seems to be 4.304, or @ .040 smaller. Did I screw myself and buy the wrong pistons? <P>I also bought a set of .030 over Federal Mogal pison rings and the two compression rings have a gap of .022 to .023 right out of the box. <P>I was trying to rebuild my motor to the specs that are in the Buick Performance Engines book by Steven Dove. Can someone help me here. Do I need to buy .040 pistons and rings? Thanks. Link to comment Share on other sites More sharing options...
Straycat Posted November 26, 2000 Share Posted November 26, 2000 <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 70gsconvt:<BR>...I measured the piston diameter and that seems to be 4.304, or @ .040 smaller. Did I screw myself and buy the wrong pistons?....<HR></BLOCKQUOTE><P>Based on your math, they are the wrong pistons.<P>Where did you get the engine from? It seems you weren't aware that it already had a .030 overbore.<P>If you plan on running on the street, a .040 overbored engine will run hotter in stop-n-go traffic. You may have to also upgrade your radiator to one of those expensive 4-core aluminum radiators. A ball park figure for heat increase is 10 degrees for every .010 overbore. In your case, 40 degrees hotter than the original stock 455.<P>Based on your current bore sizes, and the fact the walls may also be tapered, a .030 over piston may be out of the question. Final word on this will have come from the engine shop that will be doing the machining. <P><p>[This message has been edited by Straycat (edited 11-26-2000).] Link to comment Share on other sites More sharing options...
Guest Posted November 27, 2000 Share Posted November 27, 2000 The standard bore on a 455 is 4.314, so the block is bored .030 (@ 4.344). My question is this, are the pistons too small, being 4.3045, to use in these cylinders and should I go to rings that would give me a .016 to .018 gap on the top ring and .012 to .014 on the second ring like it says in the Buick Performance book? Link to comment Share on other sites More sharing options...
The Old Guy Posted November 27, 2000 Share Posted November 27, 2000 it is not a good idea to try to run those pistons in that block, as you will destroy it and it will rattle so bad it will scare you. You will be much better off to try to find some .030 over pistons. It is very difficult to find a block good enough to run standard pistons any more, so you may have learned an expensive lesson Link to comment Share on other sites More sharing options...
The Old Guy Posted November 27, 2000 Share Posted November 27, 2000 You might also check the number and see if they are in fact 455pistons. Link to comment Share on other sites More sharing options...
Guest Posted November 27, 2000 Share Posted November 27, 2000 L2353F pistons is the correct number for the forged TRW pistons for the 455 engine. The .030 marking should be the oversize. It sounds like they are marked wrong.<P>------------------<BR>Hal, btk@vbe.com Link to comment Share on other sites More sharing options...
Guest Posted November 27, 2000 Share Posted November 27, 2000 Thanks for the advice. What should be my correct piston to wall clearances? If I'm reading this book right, they recommend .006 to .008. Is this the size piston I should be getting? Link to comment Share on other sites More sharing options...
Guest Posted November 27, 2000 Share Posted November 27, 2000 those piston to wall specs seem a little large to me....i put a 462"motor together a few years ago with forged pistons/moly&cast rings...i went with .0045 piston to wall and around .016-.018 end gaps...no problem after 11,000mi.....let me just say that anytime you are going to get a block bored,always have the pistons first,so the machinist will know the true size he's dealing with...... Link to comment Share on other sites More sharing options...
Guest Posted November 27, 2000 Share Posted November 27, 2000 I just talked with the tech guy that Poston uses. He informed me of my ooops. I was measuring the piston size at the top instead of closer to the skirt past the wrist pins. My pistons are 4.3405 which will give me a .0035 to .0045 piston to wall clearance, which is what I was looking for. <P>I think I will get a set of file-to-fit rings and get the gaps down to .0016 to .0018, just for shits and giggles. Thanks for all the help and info here.<BR> Link to comment Share on other sites More sharing options...
capgage Posted December 2, 2000 Share Posted December 2, 2000 70gsconvt-<P>This will betray my lack of knowledge/experience, but what tools are you using to measure your pistons and bores? I would like to get some calipers (or whatever you are using) that measure to the accuracy you are measuring, but I don't know what tools to look for (or where to look for them).<P>I have my 364 all apart now, heads have been rebuilt. The next step is to find a reputable machine shop in or around Austin, TX to do the machining on the block and crank. I don't have a way of measuring my bores and pistons to for taper, out of round, etc. myself. I would like to go in with some good starting info, so they know I know what I'm talking about.<P>What measuring devices should I get?<P>Thanks,<BR>Mark (first engine rebuild) Link to comment Share on other sites More sharing options...
Guest Posted December 3, 2000 Share Posted December 3, 2000 I am using a digital micrometer that I picked up at a machine shop sales store. They go anywhere from about $40. on up to $200+. My pistons were brand new, so I was not too concerned about them being out of round. But I had forgotten about checking a piston's true diameter at the wrispin rather than at the top. As for the cylinder bores, you need a set of snap calipers. You just put them in the bore, open the caliper until it "snaps" in the bore, lock it down and then use the micrometer to measure the bore's diameter. Like most things, it's not really hard, just a matter of practice and knowing how to do it. I hope this helps.<BR> Link to comment Share on other sites More sharing options...
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