Piston Slap? Ridges on bottoms of cylinders (pics and vids) Help!!

S

speedfreak426

New Member
Mar 31, 2008
380
1
0
Brighton, MI
Last year I purchased a JDM 7mgte to put into my 77 Celica. Upon receiving the engine I pulled it apart, lightly lapped the head and block to remove small imperfections, installed a new OEM HG, and put it back together using ARP head studs.

Mods are(if it matters): Cooleeze Big Mouth DP, 2.5" IC pipes, Aftermarket intercooler, Walbro pump, MBC. ARP studs torques to 78lb/ft

Over the summer I drove approx. 3000 miles, about 1900 of those miles were on stock boost, and the rest on about 9.5psi right at boost cut.

I went to take an exhaust video after geting it installed, upon startup it sounded almost like rod knock but went away after a second or two... and it did not make the noise when revved. The engine always ran perfectly smooth and never gave me much trouble.

I broke the trans at the end of the summer(broke 1-2 shift fork bolt) and I had to take the engine out with it because of space issues... so I figured I would pull the motor apart because of some worries that I had about rod knock.

After pulling the head off I saw that I was already starting to get a BHG after 3000 miles! I admit I was pretty hard on the car over the summer, but in just 3000 miles? That sucks.... and there are no machine shops around me capable of prepping for a MHG. Pic of headgasket... #'s 5 and 6 were the ones starting to go bad
p1251517_1.jpg


Pulled it apart and all the bearings and journals looked to be OK. Pics...
p1251517_2.jpg

p1251517_3.jpg


Pulled the pistons out... and this is what worries me. I have torn a few engines apart and I have never really dealt with ridges that appear on the bottom of the cyl's. Maybe this was the cause of my noise? Could have been piston slap? There is barely any ridge at the tops of any of the bores, but the bottom of every bore had a very visible ridge that you can easily feel. Is this normal for the 7M? and is it safe to put back together and drive for another 3000 miles while I save up for a forged build? I want to build the motor once and I want to build it right... It has proved very difficult for me to find any machine shops that know anything about imports here in Michigan. Nobody has a Torque plate, and nobody can finish to a MHG correct surface RA.

My basic questions are....
Is this wear normal?
Is it safe to put back together and drive, so I can save up for building it right?
Has anyone ever seen this happen on a 7M?
Why is the bottom getting a ridge and not the top?


Cyl. pics...

p1251517_4.jpg

p1251517_5.jpg

p1251517_6.jpg


pistons
p1251517_7.jpg

p1251517_8.jpg



I appreciate all help! I need to get my Celica back on the road!


Here is the video link....
Video might not be done processing yet...
this is the only time I heard the engine make this noise that I remember. Didnt hear it in the car, only on the video. At first I thought it was rod knock, but it has no symptoms of knock

http://www.youtube.com/watch?v=KooOxJ38LhI
 
Last edited:
S

speedfreak426

New Member
Mar 31, 2008
380
1
0
Brighton, MI
Yeah, I have read that thread already. I searched for a few hours yesterday and thats about all I came up with that helped.

Edit: I know exactly what piston slap is.... but I am just looking for an answer as to how safe it is to drive the rest of next summer
 
Last edited:
I

IJ.

Grumpy Old Man
Mar 30, 2005
38,728
0
0
62
I come from a land down under
LOL sorry it's a new one to me!
(I'd expect it to have no oil rings left looking like that)

7M blocks are some of the hardest cast iron I've machined over the years so that's some serious wear, if I had to guess I'd say it has the wrong size pistons in it and it's been slapping like a bitch and rocking the rings on the change of direction.

Usually the skirt breaks off the piston at the Oil ring groove in that scenario.
 
Piratetip

Piratetip

Far From Maddening Crowds
Staff member
Super Moderator
Dec 30, 2005
1,177
69
48
39
MKE, WI
Strange machine shop work to make those ridges?

I hear you on the Michigan bit, have had a few bad experiences here.
Best bet is race shops NOT machine shops, I have had good luck with them.
 
S

speedfreak426

New Member
Mar 31, 2008
380
1
0
Brighton, MI
When I tore the motor apart when I first got it I could tell that it had never been taken apart before. I don't think the factory would have put in the wrong size pistons?

The only time I ever really even heard the "slap" was during the vid that I took, probably becasue the camera was on the ground behind the car.


I am really trying to upload the video!!!! I tried on my own computer and it kept freezing up, now I am on another computer and I am hoping for progress. I'll post it up if it ever uploads!
 
I

IJ.

Grumpy Old Man
Mar 30, 2005
38,728
0
0
62
I come from a land down under
Measure the piston skirt just below the Oil rings where it's not badly worn then measure the top of the bore.

It would be very unlikely for Toyota to make a mistake but it's a 20 year old engine it may have been apart at some time.
 
S

speedfreak426

New Member
Mar 31, 2008
380
1
0
Brighton, MI
IJ.;1251850 said:
Measure the piston skirt just below the Oil rings where it's not badly worn then measure the top of the bore.

It would be very unlikely for Toyota to make a mistake but it's a 20 year old engine it may have been apart at some time.
Click to expand...

I will try to bring a piston or just the one that looks most worn to work tomorrow so I can mic. it.

No mic. at home :(
 
I

IJ.

Grumpy Old Man
Mar 30, 2005
38,728
0
0
62
I come from a land down under
Clean the carbon off the crown and check for size marks then measure the bore if you have a vernier at home, top of the bore won't have any wear so it "should" be 83mm if it's stock size.
 
S

speedfreak426

New Member
Mar 31, 2008
380
1
0
Brighton, MI
The noise at the end of the video is just a heat shield rattling.


IJ: When I looked at the pistons last I was pretty sure there were no markings on the crowns of the pistons? I dont have access to a big enough vernier caliper or t bar mic I don't think. I will check at work tomorrow though...
 
I

IJ.

Grumpy Old Man
Mar 30, 2005
38,728
0
0
62
I come from a land down under
"Slap" will be most evident when it's a cold start and "should" get a little quieter as it warms.

Can't tell from the vid the camera needs to be at the front and the engine idling.
 
S

speedfreak426

New Member
Mar 31, 2008
380
1
0
Brighton, MI
IJ.;1251893 said:
"Slap" will be most evident when it's a cold start and "should" get a little quieter as it warms.

Can't tell from the vid the camera needs to be at the front and the engine idling.
Click to expand...

:cry:

Kind of hard when all of the engine parts are laying on top of the toolbox and the transmission is in pieces.... and there is snow on the ground! LOL




anyways, I didn't ever notice the noise on start up while DDing it. Only on that vid.
I didn't watch the video til like a week after taking it. I heard it and was instantly thinking Ut ohhhh.

Still drove it for another month, and even took it to the drag strip after taking that vid, ran perfectly fine. I am just worried about it becasue I don't know if I can afford a proper rebuild ATM
 
a_sesshoumaru

a_sesshoumaru

Suprita
Jan 7, 2007
455
0
0
El Salvador
hey are those pistons aftermarket? i always check for pistons clearance when i am building a motor, and when i take the head off it always looks like it, but again with aftermarket pistons at 0.035 inches clearence.
 
You must log in or register to reply here.
Top Bottom