Joey Mack Posted 16 hours ago Share Posted 16 hours ago Gotcha. Quote Link to comment https://www.bigmacktrucks.com/topic/75768-300-rebuild/page/19/#findComment-588858 Share on other sites More sharing options...
Joey Mack Posted 16 hours ago Share Posted 16 hours ago I may be wasting your time, but since they are 1 pc. Pistons, can you slide a ring less piston in to take the measurements? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75768-300-rebuild/page/19/#findComment-588859 Share on other sites More sharing options...
Freightrain Posted 16 hours ago Author Share Posted 16 hours ago Guess I'm confused....why? I bore gaged the cylinder and miced the piston. I have clearances that I question. Are you thinking I should use feeler gages? Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/75768-300-rebuild/page/19/#findComment-588863 Share on other sites More sharing options...
Joey Mack Posted 6 hours ago Share Posted 6 hours ago Yes to feelers. Not trying to confuse you, just curious myself. My gut tells me you are good. Especially with your skills. Im also assuming you have long feelers or metal shim paper like I have. Ill take a break for a bit. Still waiting for other comments. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75768-300-rebuild/page/19/#findComment-588866 Share on other sites More sharing options...
Freightrain Posted 4 hours ago Author Share Posted 4 hours ago I am just confused why feelers would be more accurate then using micrometers and a bore gauge. Both should give the same basic results if done correctly. Unfortunately I don't have long feeler gauges, as I have never had a need for them. I measured the old pistons and they are 4.867/4.868. Those were running on a bore of 4.875(on size and negligible wear). That gives it +.003 more clearance on average. Maybe I am splitting hairs but I don't want to have to do this twice! Thousandths make a difference. 2 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/75768-300-rebuild/page/19/#findComment-588867 Share on other sites More sharing options...
fjh Posted 2 hours ago Share Posted 2 hours ago 2 hours ago, Freightrain said: I am just confused why feelers would be more accurate then using micrometers and a bore gauge. Both should give the same basic results if done correctly. Unfortunately I don't have long feeler gauges, as I have never had a need for them. I measured the old pistons and they are 4.867/4.868. Those were running on a bore of 4.875(on size and negligible wear). That gives it +.003 more clearance on average. Maybe I am splitting hairs but I don't want to have to do this twice! Thousandths make a difference. So i see did you check the ring gap in the bores and you did have to file some ends! If you didnt file too much I would put this question in a a dark corner and move on! You can stew for ever on this ! Joey mentioned putting in a piston with out rings that is a good thought! But what is the min- max measurement with that method just a gut feel ! I have a gut feel as well and it is if it ran before it will run again ! if these pistons are NEW Mack pistons or the old ones they will be fine if they came with a kit they should be fine if they are what you ordered! Just ME! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75768-300-rebuild/page/19/#findComment-588874 Share on other sites More sharing options...
Popular Post Freightrain Posted 1 hour ago Author Popular Post Share Posted 1 hour ago It is all Mack parts. My concern is the liners being almost -.002 undersize from book spec after installation. Why? Manufacturing? I had .0015-.002 shrink and the book calls for .001 clearance to .-001 shrink. It squeezed them a bit. Then the pistons being +.001/.0015 larger then old pistons. It all adds up to tighter fit. The book has a wide variation, so what is right? That is all I question. I have slipped pistons in the bore(had to to be able to check ring gap). They fit, it isn't that tight. Like I said, I don't want to gall a liner and tear it apart again. This is all just the anal "wannabee" machinist in me. I'm all for hacking shit that doesn't matter. Engine work is a not that. 3 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/75768-300-rebuild/page/19/#findComment-588876 Share on other sites More sharing options...
fjh Posted 1 hour ago Share Posted 1 hour ago 31 minutes ago, Freightrain said: It is all Mack parts. My concern is the liners being almost -.002 undersize from book spec after installation. Why? Manufacturing? I had .0015-.002 shrink and the book calls for .001 clearance to .-001 shrink. It squeezed them a bit. Then the pistons being +.001/.0015 larger then old pistons. It all adds up to tighter fit. The book has a wide variation, so what is right? That is all I question. I have slipped pistons in the bore(had to to be able to check ring gap). They fit, it isn't that tight. Like I said, I don't want to gall a liner and tear it apart again. This is all just the anal "wannabee" machinist in me. I'm all for hacking shit that doesn't matter. Engine work is a not that. I do understand your concern! Max book specs I would guess ! unfortunately we aren't there so I guess all we can do is count on your expertise to make a call! If they are all Mack parts If I were doing what you are doing I would go with it! and trust that the parts they made are good! ! have built quite a few 237 and 285 E6 and never encountered an issue BUT there is always that possibility I guess! your call Bro! I personally feel good about how your attacking this! Just Sayin! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75768-300-rebuild/page/19/#findComment-588877 Share on other sites More sharing options...
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