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Truthfully as Dirty as those plugs are and the fact your already 65% pulled already, Don't aggravate yourself with going half way. Pull it have the Cylinders Checked/Honed out get heads & Valves rebuilt even put a little better cam in, and I'm sure that many can tell you how far to go with that without becoming a problem. I don't Recommend a cylinder Bore Out, it seems to breed Overheat Posts
Alrighty then! Finally got the engine pulled and identified the source of the knock. With the engine upside down I put each rod just past BDC (where the piston is just starting to push toward TDC). At this point, I hit the cap with a rubber mallet; if there's a spun bearing then there will be a gap and the rod will shift, making a loud clunk. Then I confirm with another hit and it should sound solid (whether there's a problem or not).
I did them all and #8 is the culprit. All the rest make just a very slight 'pok' (to be expected). But #8 was scary loud, almost echoed. So there's my culprit.
I'm glad you got to the Ahha Moment sorry that it is a major problem, pull the caps and inspect since it didn't fall apart it's a straight forward rebuild. Depending on what lies beneath the caps will tell whether you're crank and rod is salvageable. For piece of mind go new or I am sure many will voice an upgraded racing crank suggestion and this is the time for that if so inclined.
@Tom400CFI yeah, my head's been leaning that way and doing some research, reading old 383 stroker posts and such. I read another post about someone (sorry, lost the reference) that was looking to stroke without boring (377cid?) @s carter , I agree regarding the over-boring. I think I'll just buy some honing stones and ensure I've got straight walls anyway (I've done this before to my 71 Cougar's 351 Windsor). I lean toward a 3.75 stroke but I really am wary of going to .030 unless necessary (call me crazy, I like the idea of having room for another 100k miles). I'm thinking that if I stroke it without overboring then I have room for a 64 or 76 chamber when I upgrade the heads; If I go full 383 then 76 is my only choice if I want to stay under 10:1 compression.
The culprit, #8. #6 is also starting to go, can barely feel some groove starting on the crank. I measured the cylinders, they're all 4.000-4.001 from top to center; although, two have a slight wearing in the outside side of the wall,
The most important question right now is whether you have a local machine shop that you trust to check and recondition the crank and rods. If so, then you have that option. If not, then you will need to buy a crank kit, and you may consider doing a stroker kit. Local machining may be your least expensive option. Poking it out to 377 or more may merit bigger injectors and retuning the ECM as well, so another added expense. Slippery slope, etc...
I don't think is salvageable w/o welding....and at that point the cost is approaching or exceeding the cost of a new crank, no matter how good the local machine shop is.
A crank on Summit is $190.
