Supra Forums banner

41 - 60 of 60 Posts

·
Registered
1987 Toyota Supra
Joined
·
498 Posts
Are the Cam Gears still in good shape?
If they are, that's a testament to the work Andrew down under does.

I also agree someone use way too much sealant on the cam cover corners.
 

·
Registered
Joined
·
549 Posts
Hmm. So it's the one that failed after a short time. Before giving you my input on what I think happened I want to make a comment on the lack of cleanliness of the head they machined and gave back to you. Where the cam seal goes is a layer of brownish yellowish goob that a shop doing any work on a head should have properly cleaned. That they apparently did not strip, clean and inspect the empty head would really make me angry if I spent big bucks like you clearly did. That's very poor shop workmanship and may be exactly why this happened. My shop I use runs every head through a meticulous cleaning process. Who knows how much machining goob they left in the block and head for you (yes, I'd be cutting your oil filter open as well).

What killed your engine here was IMO the #1 cam and journal oil clearance. Lack of it. I don't give a rat's butt whether the cam was too large, (which an aftermarket maker whose cams go into used heads with loose journals would be wise to do) the shop gave you a head back after all that machining and they (apparently) did not plastigage the cam oil clearances before handing it back to you. That would have caught the issue and easily clearanced it. I did mine with 1200 grit in the spare room, and got nice oil clearances. Please post the other part (the upper journal you bolt on) because only a few months ago someone got a 7M head back from their shop with the exhaust upper journal mistakenly put on either backwards, or swapped with the intake, or both. So I'm wondering if you could post BOTH your intake and your exhaust upper journal since that's apparently possible to do, if you smoke enough crack. If your exhaust upper is wrecked like the intake lower you've already posted (it will have a mark "I" or "E") so we can verify what was supposed to go where), but the intake upper is mysteriously fine then we have some clear evidence they installed them in the wrong places. If the intake upper journal was installed backwards, you'll also be able to tell because there is a cast arrow on it and you'll be able to compare the scratch marks with the lowers by looking at where the marks meet (or don't meet). Obviously the forward half of the head side of the journal is far more damaged, so if it does not match the upper you'll know before even posting the pictures.

I think the #1 cam bearings siezed. I do not believe for a NY minute that a loose cam gear bolt caused that bearing damage - it was the other way around. So let's see those journals for the final word - at least from where I sit.
 

·
Registered
Joined
·
63 Posts
Discussion Starter · #44 ·
I agree completely and that was my original thought. I have the caps I forgot to take a pic of that. I’ll do it today. When I pulled the valve covers they did have them on in the right order and facing the right way. I don’t think any plastigauge was used on the cams. these are reasons why I’m going else where with this head even though they would’ve helped take care of labor. Not worth it. I’m probably fortunate this was it.
I also noted that the cap bolts seemed a lot tighter than They should’ve been. They really broke loose. We thought at my shop that they were over torqued. I didn’t put a wrench on them coming off though. They cam seal came out though. It was ingested slightly. And the gears seem fine. The dowel pin hole is slightly wallowed. Aside from that I can’t see much of any witness marks. Maybe a little ring from the washer on the cam bolt.
 

·
Registered
1987 Toyota Supra
Joined
·
498 Posts
I've seen something similar to this before, but on a Subaru when I used to work in a dealership way back.
The owner never changed the oil or it went very low on oil level.
The right hand bank, intake side camshaft snapped in half right behind the 1st cam bearing.
Engine was still running but, running like shit of course.

The camshaft belt was strong enough to snap the cam in half without breaking or skipping a tooth.
Pretty incredible to see.

The root cause was oil starvation and intense heat at that cam journal.
The heat weakened the metal, sized it and snapped in half.
Engine was basically running on the LH bank 2 cylinders only.

I don't enjoy remembering having to work on that vehicle, but was something out of the ordinary.
 

·
Registered
1987 Toyota Supra
Joined
·
498 Posts
That took a long time of searching but I found the photos from my mention on the previous post.
My memory was not quite right, the camshaft snapped in front of the 2nd bearing.
So the engine was sort of running on 3 cylinders, with the back cylinder having no intake valve actuation.
Subaru H4 2.5L engine.

 

·
Registered
Joined
·
549 Posts
Yeah, the cogged belt drive system is pretty crazy stout and overbuilt. It's amazing to think of the force. Journal cap pics from 7M?
 

·
Registered
Joined
·
63 Posts
Discussion Starter · #50 ·
It 110% was not oil starvation. It had 8 fresh qts of Amsoil racing series and an HKS magnetic filter on it.
261275
 

·
Registered
Joined
·
549 Posts
Not oil starvation as if it had no oil, but the journal cap in your hand was too tight for an oil film between it and the spinning camshaft for the parts to "float" on. There has to be a certain range of space in a cam/crank/con rod bearing for the oil to go through it and if it's too tight the oil just can't move through it, and also the two parts are in physical contact which they're not supposed to be. Heat builds up, damage occurs and after awhile they start "galling" or swapping metal until the entire space is filled with metal and the parts are now generating incredible rotating friction and heat. Often they seize suddenly and snap the cam shaft. In your case, it forced the cam gear to move and place this force on the locating pin which is not designed for that, and then snapped the pin and began spinning the pulley under the washer.

All could have been fine if the shop had taken time to check the oil clearance on the cams - part of their job. No head should EVER go out the door without someone checking that and some of the best shops will actually document the measurements.
 

·
Registered
1987 Toyota Supra
Joined
·
498 Posts
What stamp is on the top of that cap?
Which way was the arrow facing?

I1? E1?
 

·
Registered
Joined
·
63 Posts
Discussion Starter · #53 · (Edited)
The caps were in correct orientation. Exhaust side is fine. I didn’t put a torque wrench on it coming off but it felt stiffer than the 14ft lbs or whatever the Spec is.
It is not going back to the same machine shop for the next head. The shop I’m going to use this time knew it was a 7m when I told him 88’ Supra. He’s done a bunch over the years out of Aurora, IL.
BC cam will be here tomorrow and it goes back out
 

·
Registered
Joined
·
549 Posts
Yeah, that's oil starvation - classic. It's NOT a too tight timing belt and here's why. You'd see excess wear on the LOWER JOURNAL and inboard area of the bottom journal from the pulling DOWN and INBOARD from a tight belt, and this is the upper. I didn't mention this earlier when all we had was the lower journal to see but that's my read - no obvious divoting on the inboard lower area which is the force vector on your timing belt. Bummer it happened but you are on to another shop and I hope they square you away. I want to see a picture of your Supra with bugs smashed all over the front of it, no more internal damaged engine bits!!!! Heh.....


Doug
 

·
Registered
Joined
·
63 Posts
Discussion Starter · #58 ·
Me too! They said probably 4-5 days turn around time so I'm really hoping for next weekend
 

·
Registered
Joined
·
63 Posts
Discussion Starter · #59 ·
Wreckless- I Made an appointment with Larry for end of August.. They're booked out that far, but I want to be able to enjoy this thing fully. We were talking about SP on another thread. They are the best around and so close that I might as well go get done by them.
 

·
Registered
Joined
·
25 Posts
I hope you get this resolved. That's a gut wrenching feeling to get something together and then it fails.

That said, pretty impressed by the failure analysis discussion in here. There's some knowledge here.
 
41 - 60 of 60 Posts
Top