Piston Slap!

[1988MK3]

Fella's,

My '88 7M-GTE has got a case of piston slap. I am running JE forged pistons and only have 900 miles on the car since the rebuild. It's quite loud when the engine is cold and quiets down for the most part when it's fully warmed, but never goes completely away. My blueprint for my build lists the piston clearance as .0066 to .0068 on each cylinder, which I know is a lot of clearance (.004 is what JE calls for, sounds like people like .005-.0055). The reason for the excessive clearance is because the engine was already .040 over when I got it and it had a melted piston. The cyl walls were good and i bought the .040 JE's and after honing the cylinders, that was the clearance. It's too late to go back now and tighten up the clearance, so I wanted to get your guy's opinions on this situation....

So what I am thinking is I just run it and not worry about the noise and hope it lasts for a few years. I will of course go easy on it until it's fully warm.
The other option is to sell it. I can't afford to tear it down and I don't have the time/motivation now.

Do you think there will be premature failure? Do you think it will be okay? Anyone have experience with clearances like this?

Thanks in advance guys!
Brad

 

[IBoughtASupra]

I always thought people ran tight piston to wall clearances for JE due to the high silicone content.

 

[CajunKenny]

Piston slap is a common tale with JE's. I can't comment on the clearances related to those claims; but, I've heard that at least 8.67 times in my life.

 

[1988MK3]

Have you heard anything about Supra's with piston slap having long and prosperous lives, or do they fail prematurely, like eating too much red meat?

 

[DEFIANT 7M]

Unfortunately you will be the only one to answer that. Just take it easy on it till it gets warm like you plan, hope for the best. Beat up on it and you will be tearing it down again.

 

[mk3-4-me]

I just got my 7m going with .20 over JEs.

I can hear the piston slap when i start the car and warm it up, and it pretty much goes away when it's warm. I gabby noticed it really when driving yet.

I always wait till my car is warmed up and my AFRs go to about 14.7 ( after start up enrichment ).

I didn't measure the clearances when I rebuilt mine, cause it was just rebuilt before I got the engine then it got rodknock.

But how distinct is it when it's warmed up? Do you have to listen for it? Or can you plain hear it?

 

[IBoughtASupra]

I have a bare 7M block you can have, just pay for shipping. 250-300 is what it usually cost for shipping a blockZ

If you can find a cheaper rate and want to setup the shipment and pickup, that's fine.

 

[1988MK3]

You can hear it without trying. It's not loud by any means, but you can still hear it.

I posted a video to Youtube. Sorry in advance for the terrible video quality, I took it on my phone. http://www.youtube.com/watch?v=CPxSsrijixI

I talked to the guy that did the machine work and assembled the lower end, he said it's possible if they are slapping hard enough the piston skirt could break.

Anyone had piston breakage in a 7M before from slap?

This weekend I am going to check the front pulley and power steering pump just to make 100% sure they aren't the culprits, even though I'm pretty sure it's piston slap.

 

[CajunKenny]

Have you heard anything about Supra's with piston slap having long and prosperous lives, or do they fail prematurely, like eating too much red meat?

I have only been around one engine that had JE's and piston slap. It ran fine for about 7k miles. The engine has since been removed from the car (not problem related) and now sits on an engine stand waiting to go in my car.

That's not really helpful, I know; but, that's all I got.

As already mentioned, I'd let it warm up before you beat on it.

 

[Mike Morris]

If it goes away when motor is warmed up you will be okay.

 

[1988MK3]

Unfortunately, the noise doesn't go away completely after it's fully warm. I guess I'm S.O.L.

Thanks Iboughtasupra, I don't know what I'm going to do yet, but I will keep your block in mind.

Anyone else have any comments on this situation?

 

[quake]

Fella's,

My '88 7M-GTE has got a case of piston slap. I am running JE forged pistons and only have 900 miles on the car since the rebuild. It's quite loud when the engine is cold and quiets down for the most part when it's fully warmed, but never goes completely away. My blueprint for my build lists the piston clearance as .0066 to .0068 on each cylinder, which I know is a lot of clearance (.004 is what JE calls for, sounds like people like .005-.0055). The reason for the excessive clearance is because the engine was already .040 over when I got it and it had a melted piston. The cyl walls were good and i bought the .040 JE's and after honing the cylinders, that was the clearance. It's too late to go back now and tighten up the clearance, so I wanted to get your guy's opinions on this situation....

So what I am thinking is I just run it and not worry about the noise and hope it lasts for a few years. I will of course go easy on it until it's fully warm.
The other option is to sell it. I can't afford to tear it down and I don't have the time/motivation now.

Do you think there will be premature failure? Do you think it will be okay? Anyone have experience with clearances like this?

Thanks in advance guys!
Brad

i hope this is not your only car. Live and learn from this and never do it again. The proper way to have gone about this was to get the block and bring it to the machine shop BEFORE buying pistons. Next you decide the usage and power goals and leave a bit of room to grow for the future. With that said and judging from the pic of your engine i would have gone with .004. The only way to fix it now is have swain tech build up a skirt coating to spec, or order a custom piston and sell the old ones. Another option is to take the free block but that is more money spent. Right now it is possible to crack a skirt and you will wear out the pistons and cylinder walls at a faster rate.

 

[1988MK3]

Unfortunately, I didn't know about piston slap and how bad it would be when building the engine, I know now.

Thanks for mentioning swain tech. I've never heard of them before, but it seems like this might be a good option to tighten up the clearances.

 

[quake]

the thing is it is not the best way to go about it, and it will wear down the coating. Also it is not cheap the best way is to go custom if you dont have the cash just go probe if you can. A custom order piston is only like 100.00 more dollars.

 

[DHeath0013]

I have slap in my 1J that only occurs when the outside temp is below 65 degree F. It has not gotten worst in two years and I push my car frequently. Of course I always let it warm up first and it does go away completely.