Bad wrist pin? (video included) (300 6)

[Xybris]

I have this loud tapping noise coming from the #1 cylinder. Goes away at warm idle, comes back with a load. Already changed all 12 lifters and no difference. Previous owner drove it like this for 10 years.

http://www.youtube.com/watch?v=OhONa1sCpk4

When it stops raining I'm going to go pull the spark plug wire to confirm. I just don't have a good ear for this stuff which is why I wasted $55 on lifters.

[DuckRyder]

I really don't have anything with fantastic speakers, but I'm almost wondering it that is a timing gear or something, it sounds too irregular and not quite right for a wrist pin to me.

Follow your plan of pulling the plug wires one at a time, if it goes away or significantly changes (keeping in mind that the change in RPM alone will chage the sound a little) youve at leas isolated it to a cylinder.

[Xybris]

Spark plug wire check confirmed it. Pulling #1 smooths it out. Compression is also around 85 compared to 120 on #2. This confirms wrist pin?

[Ranchero50]

It wouldn't be a straight six without a rod knock. Really depends on what you want to do with the truck. These motors will run forever with a rod knock so if you are using as grandpas parts go getter around town then it should last long enough. If you plan on swapping a V8 you have time, same as just swapping in another motor. You have time.

Jamie

[DuckRyder]

This confirms wrist pin?

Not really, but it tells you you have something mechanical going on with that cylinder, since the compression is low as well, I'd suspect a cracked piston skirt or something along those lines. It could be anything on that rod and piston assembly though, better get it out and see if you can salvage it before it lets completely go...

[Xybris]

I'm trying to evaluate whether it's worth it or not. I'm already out $500 on brakes, starter, battery, carb, lifters, seals. Just to see what's going on in that cylinder will cost at least a head gasket, oil pan gasket, manifold gasket, plus repair of the actual problem/machining, and probably something else- I've never removed a head before. Previous owner hauled sand and gravel for ten years with it tapping, it would be just my luck it breaks on my way to AutoZone. I've only driven it twice in the month I've had it for a total of 10 miles.

[fordman]

ive never heard that before. but i want to know waht the anser is. so please update when you find out. it mightnot hurt to pull the valve coveer to see if anything is loose in there.

[DuckRyder]

Of course only you can decide if it is worth it, but even an overhaul gasket kit shouldn't be that much money (what 80.00 or so) and if you are careful you could probably put it back together and not be any worse off if you decide it is too bad to fix.

The thing that concerns me is the compression being lower. That would seem to indicate that something is impacting ring sealing which could mean that the piston skirt is cracked allowing the piston to rock in the bore and "slap" or that the wrist pin has come out far enogh to damage the cylinder wall. Either could go bad wrong in a hurry.

I'm also guessing that 300's are not exactly scarce, they are not here anyway and 150.00 would probably buy one, the only real question would be if it is any better than the one you have.

[Xybris]

Yeah, I have nothing to loose by opening it up, in fact, knowing what's deep inside the engine will only help me more throughout my car owning career. I found the gasket set for 70-something dollars so not too bad. Haven't seen any 300's locally, only V8s but the used engine market is saturated with Ch**y stuff. I know the engine I have isn't original, has a 1977 emissions sticker on it, and it knocked since it was installed back in the mid-90's.

@ fordman: Had the valve cover off when I did the lifters yesterday, nothing abnormal. Very black and gritty in there but my neighbor said that's normal for American built engines.

[Ranchero50]

Xybris, where is local? Those motors were used through the 90's trucks. Simple rugged design. I wouldn't drop any coin on the one you have, look in Craiglist and ask around and you'll find a better one for under $200 if you are patient.

Jamie

[Xybris]

I'm in Oregon. I've checked Craigslist but not really outside my local area. Well, I saw a late model fuel injected one but I have no idea if that would work on my 68.

[Ranchero50]

The EFI 'should' work fine. The guys use the late style twin exhaust manifold on these trucks. Change the distributor, intake and maybe the oil pan and it should be good to go...

Jamie

[Xybris]

Are the engines and transmissions all interchangeable? I have the 4 on the floor. Does that work with all the other engines 6's and 8's?

[fordman]

i do know the early and late small blocks use a shorter and longer dist. by abotu 1.2 inch i heard. watch out for that on those engines. i dotn know if its true on a 6 cyl or not.

[Xybris]

I ran the description of my problem past a mechanic from back in the day and he's not convinced that it's piston related. Says it's most likely rocker or pushrod related. Gonna drive it by tomorrow night so he can listen to it.