97 1fzfe knock (1 Viewer)

[bwiygul]

Situation: I bought a 97 80 from my friend with piston slap in cylinder 1 and 3.

I’m planning on doing an LS swap in the next two years but I’d like to not have it knocking for that amount of time. I intended to do it sooner but life.

So the question is: do the crank bearings go bad and that causes it or is it something else? Is there any way to get it “good enough” by working it from the bottom end for a temp fix?

Thanks for the help!

 

[SNLC]

Yes they go bad, especially with crappy maintenance.

Sure go for it, what do you got to lose by dropping the pans and taking a look? Or even slapping some bearings in and running it into the ground?

Cheers

 

[bwiygul]

Yes they go bad, especially with crappy maintenance.

Sure go for it, what do you got to lose by dropping the pans and taking a look? Or even slapping some bearings in and running it into the ground?

Cheers

Is it usually the bearings that cause the slap or just worn pistons?

 

[jpoole]

Piston slap and bearing knock are separate things. Sounds like you aren't sure where the noise(s) are coming from, is that right?

 

[SaturnAscends]

How was it determined that it was piston slap? Sometimes knocking noises turn out to be something else like a power steering gear or exhaust leak.

 

[bwiygul]

Well a reputable shop said piston slap. What I’m not sure of is what causes it. Is it bad bearings or cylinder/piston wear.

And I’m also not sure if you can get enough clearance to work from the bottom end for a “temp” repair.

 

[BILT4ME]

Well a reputable shop said piston slap. What I’m not sure of is what causes it. Is it bad bearings or cylinder/piston wear.

And I’m also not sure if you can get enough clearance to work from the bottom end for a “temp” repair.

Yes, there's enough room to work from the bottom for a temporary repair.

I highly recommend you do a better diagnosis on your own to verify the noise before you just tear off the oil pans. Oil analysis (Blackstone), Oil pressure readings, compression tests, stethoscope, remove a plug wire to hear differences.

Having piston slap in 1 and 3 seems odd, as it is usually 1 and 6 or 3 and 4 because of how the crank is configured.

 

[bwiygul]

Yes, there's enough room to work from the bottom for a temporary repair.

I highly recommend you do a better diagnosis on your own to verify the noise before you just tear off the oil pans. Oil analysis (Blackstone), Oil pressure readings, compression tests, stethoscope, remove a plug wire to hear differences.

Having piston slap in 1 and 3 seems odd, as it is usually 1 and 6 or 3 and 4 because of how the crank is configured.

Ok. I just know the shop diagnosed it for the PO. They did say it goes away with the plug pulled. That’s how they figured 1 and 3 but I’ll follow up as well. It’s for sure a distinct knock during idle and acceleration but drops off on decel.

 

[Dave Pierce]

Situation: I bought a 97 80 from my friend with piston slap in cylinder 1 and 3.

I’m planning on doing an LS swap in the next two years but I’d like to not have it knocking for that amount of time. I intended to do it sooner but life.

So the question is: do the crank bearings go bad and that causes it or is it something else? Is there any way to get it “good enough” by working it from the bottom end for a temp fix?

Thanks for the help!

Was involved in a AMC dealership years ago and we had problem with engine knocks on the top end of the inline 6 cylinder motors, the cause was carbon build up on top of the cylinders, a piece would break off and you could hear it knocking around, the cure from American Motors was poir a pint of transmission fluid slowly into the carb at a high idle, be prepared for a smoke out, this would dissolve the build up and end the knock, the cause of the buildup was low octane fuels. Use a engine stethoscope to determine if your knock is on the top end or bottom, if its the bottom change the oil and try some high friction lubricants. hope this helped.

 

[jpoole]

Based on how little cylinder wear these engines typically show, even with high miles, I'd think that bearing damage from oil starvation or something like that would be a more common source of bottom-end noise generally though you have to be open minded until you figure out what the problem is. Pulling a plug wire to remove ignition load can be a good diagnostic tool as can listening for the noise on accel/reving and decel of the engine. Combining those with a mech. stethoscope could be worthwhile. I'd also want to closely monitor the differences in these noises when the engine is cold, warm and hot.

Regarding piston slap, one cause of it, possibly the most common, is overheating. The piston skirt will expand and press out as the piston warms up, snugging it against the cylinder. When you overheat a piston it will over-expand and this often causes more wear on the cylinder bore where the skirt presses against it and this also causes the shape/strength of the piston to deform/collapse to some extent. When the engine/pistons cool back down the skirts will over-contract essentially and end up having a larger gap, or more clearance, between the piston and cylinder. The slap is typically most noticeable when the engine is started and cool and then lessens as the engine warms up, typically going away when the engine is at full operating temp. On engines with really bad slap they may only stop when overheated again.

There can be other causes of piston slap like wear of the cylinder/piston or improper sizing when the engine was built, etc..

The slap happens as the piston changes direction. The skirt will be tight against one side of the bore on the up stroke and then when the piston starts to travel back down the slack in the bore will allow the piston to pivot slapping over against the other wall of the cylinder, making the slapping sound as the piston skirt switches from one bore wall to the other. The wear and slap are at the top of the stroke, where the compression forces are at play and pushing the piston down/etc. Running these slappy engines long term causes a lot of piston and bore wear as the piston rotates/slops around more and more.

An older technique for dealing with piston slap was to knurl the piston skirt which would essentially enlarge it where the knurling was done and tighten it up in the bore. You can search for info on this to better understand slap. Piston design (skirt length/shape) can have a big impact on if it will even slap, and how it changes shape as it heats up, etc.

If you get access to the bottom of the pistons you can check the clearances of the skirts to see if they are excessive, etc. There may not be specs on how to do this for the 1fzfe but basically if you compare clearances piston to piston at various positions in the cylinder you can figure out what clearances should be, etc.

 

[bwiygul]

Thanks- I appreciate the info. I trust the shop that looked at it as I’ve had a long relationship with them as well. Coincidence that the PO had taken it there. He’s a Toyota/cruiser guy and very familiar with jap motors. But I get it- gotta double check. I was hoping that it might be something more with bearings but if not….

Can pistons come out from the bottom? I’m curious about how much room between the crank and the bottom of the cylinder. I don’t mind replacing the pistons if I can do it from the bottom relatively easily. It seems like it should be but…. I’ve not torn into enough motors to know. And I’ve never tried this.

 

[BILT4ME]

Thanks- I appreciate the info. I trust the shop that looked at it as I’ve had a long relationship with them as well. Coincidence that the PO had taken it there. He’s a Toyota/cruiser guy and very familiar with jap motors. But I get it- gotta double check. I was hoping that it might be something more with bearings but if not….

Can pistons come out from the bottom? I’m curious about how much room between the crank and the bottom of the cylinder. I don’t mind replacing the pistons if I can do it from the bottom relatively easily. It seems like it should be but…. I’ve not torn into enough motors to know. And I’ve never tried this.

No.

 

[bwiygul]

No.

Damn…

 

[mudgudgeon]

Damn…

There's a big wiggly piece of iron that gets in the way of pulling pistons from the bottom.


You can pull the sump from underneath and change rod bearings. Give everything a thorough degreasing and was down first, or you'll keep copping an eyeful of crud.

If you want to go much further than swap out rod bearings, it would be worth the effort to yank the motor out.

 

[bwiygul]

There's a big wiggly piece of iron that gets in the way of pulling pistons from the bottom.


You can pull the sump from underneath and change rod bearings. Give everything a thorough degreasing and was down first, or you'll keep copping an eyeful of crud.

If you want to go much further than swap out rod bearings, it would be worth the effort to yank the motor out.

Yeah that’s what I was wondering. Wasn’t sure how much clearance there is between the crank (wiggly thing) and the bottom of the cylinder. I’m just trying to avoid rebuilding something that I’ll be. Pulling in the near future.

 

[manofthewoods]

Yeah that’s what I was wondering. Wasn’t sure how much clearance there is between the crank (wiggly thing) and the bottom of the cylinder. I’m just trying to avoid rebuilding something that I’ll be. Pulling in the near future.

From where I'm sitting. Your "near future" time is about now. I wouldn't drive to grandma's house, even if she was next door with the engine the way it is now.
Pulling the engine isn't that difficult, and makes every job possible and easy/fast.
Just my 2 Penny's (with inflation, not worth much)

 

[bwiygul]

From where I'm sitting. Your "near future" time is about now. I wouldn't drive to grandma's house, even if she was next door with the engine the way it is now.
Pulling the engine isn't that difficult, and makes every job possible and easy/fast.
Just my 2 Penny's (with inflation, not worth much)

Well, it has to get driven cause I’m not able to do the repair right now. Don’t have the time and working away from the location. If I had to pay somebody to work the bottom end that’s what I was hoping. But… I guess i’ll just have to keep my fingers crossed. Most people have said it’ll run another 100k miles like this. Don’t plan on that but…. We’ll see. If she goes T.U. Then ill
Have to swap or find a 1fz to drop in for the interim. They’re quoting $10k for a full rebuild and that’s nuts….