Replacing wrist pin

taylorb1 · Posted: Wed Oct 03, 2012 1:44 pm Post subject: Replacing wrist pin

Can yall help an engine noob out on what all neeeds to be done to replace a wrist pin.

do i need new connecting rod and piston?
can i do this without splitting the case?

Glenn · Posted: Wed Oct 03, 2012 1:56 pm Post subject:

Yes, it can be done without splitting the case.

Why does it need to be replaced?
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taylorb1 · Posted: Wed Oct 03, 2012 2:13 pm Post subject:

Im getting an engine noise and its not the head or rockers. it seems to be coming from the jug. so that makes me think wrist pin knock?? any way to tell

head and rockers have been replaced

Glenn · Posted: Wed Oct 03, 2012 2:23 pm Post subject:

It could be a rod knock and it could be at either end. If it's the wrist pin then the bushing in the rod should b e replaced. if its at the "big end" then the rod needs to be rebuilt or replaced.
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taylorb1 · Posted: Wed Oct 03, 2012 3:07 pm Post subject:

its not a deep sounding as rock knock. ive heard wrist oin knock and this has the same bitch.

but hey what do i know Rolling Eyes

modok · Posted: Wed Oct 03, 2012 5:11 pm Post subject:

hmmm, well, one thing you don't know is that the bushing wears 4X faster than the pin. Only times I've seen a pin that was in need of replacement was if the engine ate so much dust that it killed every bearing surface in it, or if the pin was bent

Check the skirt clearance and the pin bushings, if it needs new pin bushings then you must take them to a good auto machine shop or get a set of rebuilt rods exchange

taylorb1 · Posted: Wed Oct 03, 2012 6:21 pm Post subject:

modok, thanks for the heads up. what parts do i remove to have that outa the block to take it to the shop.

here is what i have

remove tin
remove head
remove jug

what comes next to get the wrist pin and bushings out.

miniman82 · Posted: Wed Oct 03, 2012 6:54 pm Post subject:

Make sure the arrow on the piston points at the flywheel while you're in there, could be piston slapping.
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blue77bay · Posted: Wed Oct 03, 2012 6:56 pm Post subject:

remove circlips from piston
remove pin
remove piston
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modok · Posted: Wed Oct 03, 2012 8:11 pm Post subject:

The connecting rods of course! Once you get the jugs off you can wiggle(more like twist) the pistons and feel how much slop is in the pin bushings. Once in a blue moon a pin bushing comes loose in the rod, in which case it may be shifting around and who knows, if that is the case you will probably see it once the piston is removed, or notice the three oil holes are not lined up

It is easy to OOPS... drop the rod cap or nuts into the case while your trying to take them out.... but you'll figure it out; it's not that hard.

I had an engine where the pin bushings had .004 clearance (over twice the wear limit), I took the rods out and re-bushed them and put them back in with no other changes to the engine. Could not tell the difference. On the one hand that means they have to be REALLY BAD to make a noticeable amount of noise, on the other hand the rods often tend to get neglected by DIY engine builders, so while this problem should be rare it probably isn't.
Who knows what you will find in there! gotta check everything

taylorb1 · Posted: Wed Oct 03, 2012 8:53 pm Post subject:

right on

let me double check see if i have this right.

its probably not the pin itself. most likely the bushing correct?
and i can get a new bushing pressed in and then its ready to go back together using all the same parts?

miniman82........ yup the arrow is pointing toward the flywheel. i know this because i replaced the head today.......now have to tear it all down again Evil or Very Mad

one last thing. what other things can go bad with this (thought to be) wrist pin noise? i don't want it to self destruct. its been going on for about a month. it used to be only in a certain rpm range, now its becoming more prominent.

modok · Posted: Wed Oct 03, 2012 9:11 pm Post subject:

Yeah, we remove the old bushing and put in a new one, then bore the bushing to size and make sure it's straight. Sounds easy but it does require the right tools. Don't try to DIY with a brake cylinder hone!

Usually what the career builders do is just bring in the rods and we fix em'.
They don't even bother checking them they just bring them right in.

now, I still have my doubts that this is your problem, but its possible, and it's worth checking

OLD VW NUT · Posted: Wed Oct 03, 2012 9:27 pm Post subject:

A bad wrist pin has a double knock. Heard best during idle or at part throttle where you're slowing down. As it gets worse it can get quite loud.
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taylorb1 · Posted: Wed Oct 03, 2012 9:54 pm Post subject:

taylorb1 · Posted: Thu Oct 04, 2012 4:08 pm Post subject:

here is some more insight to the problem.

everyone i talk to including the one of the local air cooled mechanics says its valve tap. well after a head swap its still there. so that rules out something with the valves......

today was the first time i got to drive the car since the swap. and the noise is worse.

i dont have a compression checker but when turning the engine over by hand #3 cylinder has the least compression aka its easier to turn than the rest of the cylinders. what im getting at is, can worn rings be causing piston slap and my lower compression.

does piston slap sound like valve tap?

its a 1600 dp and its in my DD not sure on the year cause someone ground off the numbers on the motor. its in a 76 std bug.

modok · Posted: Thu Oct 04, 2012 4:26 pm Post subject:

valve noise just means something in the valve train is making the noise, the thing about that sort of noise it it comes and goes at certain RPMs, could be the cam or lifter bores are worn, try setting the suspected cylinder to zero lash and run it for a short time..... sound gone?

Piston slap is always temperature related, it will be bad when cold but goes away when the engine is hot on a hot day

taylorb1 · Posted: Thu Oct 04, 2012 4:34 pm Post subject:

ill go set them to vero lash. BRB Laughing

taylorb1 · Posted: Thu Oct 04, 2012 6:32 pm Post subject:

did nothing.... im just hoping i dont have to split the case for this repair. it is my dd Confused

taylorb1 · Posted: Thu Oct 04, 2012 8:20 pm Post subject:

Just got back from a Waffle House snack with some friends. a 5 mile highway drive. With the new head without a bad intake valve there is noticeably more low end power.

but still the tick noise. sometimes its quiet sometimes its loud. sometimes its there at idle sometimes its not Confused

modok · Posted: Thu Oct 04, 2012 8:47 pm Post subject:

It could explode tomorrow or last forever, who knows Confused

Just think of the sound as motivation to build up a spare shortblock


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