| hi really cannot say that definitively , on any one engine you have to measure it judge for yiotself . my point is many times they are made oversize without careful evaluation , and often unneeded . But any given motor may be perfect or a wreck . FSM has some numbers ,,but even pushing the high end a bit on FSM may be the lesser of two evils . Moly rings are really good, not around back then . Another issue I have seen is fitting new pistons too tight . Hard to crank hot . Run hot . Skilled shop is critical and best guy does work . i d rather be a tad loose than tight , and that sort of happens with moderately used block . Sent from my iPhone On Jan 11, 2024, at 12:14 PM, Cox Mail <scooter465@xxxxxxx> wrote:
Just make shore you run A hone down the bores Or the new rings will not Seat properly. Bob Haag On Jan 11, 2024, at 11:54 AM, Zach Hietsch <zhietsch@xxxxxxxxx> wrote:
All,
This is a neat discussion for me to read as I am contemplating rebuilding my Bs engine here in the next year or so.
John if I am understanding what you are saying, if there is no discernible ridge or damage to the bore the best thing to do is put good rings on the piston and leave the bore alone.
That was something I was thinking about as you hear all of the horror stories of blocks being ruined by poor shop work. Also availability of new pistons and rods. On Jan 11, 2024, at 11:26 AM, Henry Schleimer <henry.schleimer@xxxxxxxxxxxxxxx> wrote:
My first car was a well used 71 Valiant with 318. Used to blow smoke if you gave it more than ¾ throttle. Being a broke student, I drove it like that for 4 years until I could afford to rebuild the engine (and restore the rest of the car). Took 40 thou over to clean up the bores. Rings were still ok. My “theory” was the factory chrome face rings were too hard at the expense of the bores. Bought a 74 Chrysler 360 for wrecking and the bores were worn out the same. Took that block to the dump – wouldn’t do that now – but put the heads on the 318. Anyway, I used moly rings on forged pistons instead. At the time there was a shop importing forged pistons for about the same price as local (Australian) cast ones and they never made any noticeable noise. Drove it for 50,000 km before selling it and never used any oil so I assume all was well. No need to be afraid of reboring an engine if it is worn out. Bad taper will kill top end power plus annoy everyone behind you. The 300C I bought had a “rebuilt” engine 40 thou over which did run. However I pulled it apart (don’t trust strangers) and found the pistons (while new) had vertical scratches all over them. Rebuilder forgot to put the spacer ring on the end of the cam and the back face of the cam sprocket ground itself into fine particles which filled the engine. Decided new pistons and rings (and oil pump etc, etc) were needed to fix that mistake but luckily only a light hone on the bores was required. My take on both examples is find a good machine shop but put the engine together yourself.... Henry From: chrysler-300-club-international@xxxxxxxxxxxxxxxx [mailto:chrysler-300-club-international@xxxxxxxxxxxxxxxx] On Behalf Of John Grady
Sent: Thursday, 11 January 2024 11:36 PM
To: Jean-Yves Chouinard
Cc: chrysler 300 club
Subject: Re: {Chrysler 300} 413 pistons. Hi , i may have a set from long ago . not sure of size ( overbore) will look why do you need new ? are you overboring it ? As you know , my feeling is unless something is really really wrong , old and go . Have done that 5-6 times in life no problems . “ expert “ will always say rebore, way it is . (Sell up , best dentures) so three jeep 4.0 done that way two i personally drove both to 300 k , zero oil use , 318 also went 300k in 57 plymouth ..all old parts no machine work . key is really good moly rings be sure you know forged or cast pistons when comparing , both work but forged a lot stronger . changing pistons gets into balancing . Any screw up boring wrecks rare 300G block I had a 327 chev ruined by “ pro machine shop “ just trying to remove ridge , a chip “fell down “ caught into guide roller deep scratch in wall . had that happen on small kohler engine too . i did not remove ridge on jeeps could not feel any with finger tip , yes took a chance . It depends — your mileage may vary but if a teal ridge should be removed 02 jeep year had junk cast mopar pistons , skirts broke off , other one (98) had antifreeze leak into oil used those over again . third one had been run out of oil (ex wife)! i bought the jeep pistons from silv -o- lite , a branch of keith black racing engines . 120$ for 6. 150 k miles ago ,,had machine shop do exchange on rod , press fit into rod like mopar . used as they came compared weights to old seemed ok there are specs in fsm on taper etc measure block for yourself . ridge too Even if pushing upper limit on wear it will work fine . Most of the time hardly worn at all !! my 02 , I know . My cynicism results from 260 ford rebuilt for my dad with all new ovetbore etc burned so much oil had to be rebuilt agaiin 30000 later . Shop kept saying it will wear in . I was left with thin wallet mad dad , and junk motor made of all new parts As far as real wear many in club have gone 300k on hemi , Jerry Kocur went 300 k and 400k is barely broken in , . I know , opinion , but backed by 5-6 examples . on other hand if damage have to do it
On Jan 10, 2024, at 8:28 PM, Jean-Yves Chouinard <jymopar@xxxxxxxxxxx> wrote: --
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