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Does this win the "Worst first post ever!" award?

kumfasa

Well-known member
Joined
Feb 28, 2015
Messages
125
Location
Tauranga, New Zealand
Hi All, this is my first post. I was determined not to be the guy whose car was on jack stands or in pieces more than it was on the road. However...
I recently purshcased a 1991 JDM Evo 0, great original condition with 144,000kms (~90,000Omiles) on the clock. I have spent a lot of time and effort performing maintenance as outlined in this forum and the VFAQ.
On my way to buy the airtools I required to replace my timing belt and all other required parts, my timing belt breaks. /ubbthreads/images/graemlins/mad.gif
Obviously I have all the timing parts (and tools) needed to execute the repairs required.

My questions are:
Aside from removing the head and checking/replacing any bent valves are there any other parts that I will need to inspect? Will the bottom end (pistons, rods, bearings etc...) have survived this? What about Cams, rockers and lifters?

Some info on the event: Car was warmed up, I was approaching an intersection at about 30kmh (20mph) I pushed in the clutch to change down and "bang" then I hear the tinkling of valves meeting pistons and it stops running. I coast to the side of the road and thats it. Not under load, not high RPM's, and not in gear.

I pulled the upper timing cover off and it looks like the balance shaft belt snapped and took out the timing belt. I haven't pulled the lower timing cover yet.

I would appreciate some input on how far I have to go to ensure that everything is okay to get this back on the road.
 

EMX5636

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Jun 28, 2008
Messages
1,631
Location
Bucks County, PA
Sorry for the crappy luck! Usually the pistons and bottom end are ok when a belt breaks at lower RPM. There might be a couple nicks in the pistons you can take a file too remove any sharp edges. The older cast rockers hold up really well, same with lifters. Good luck, take any pics of anything you are unsure of, and post them up so we can give you help if need be!
 

kumfasa

Well-known member
Joined
Feb 28, 2015
Messages
125
Location
Tauranga, New Zealand
Thanks for the quick response Justin. Im glad I wasn't boosting to redline at the time so hoping for the best. Good to know that most of the parts are likely to survive. I would loathe having to remove the block from the car. I've started the head removal process and will know more once I get a look inside. I figure I will come up against some corroded fasteners and other obstacles but I will post up some pics of the damage once I get it apart and then I'll look for some feedback then.
 

toybreaker

iconoclast
Joined
Apr 30, 2006
Messages
3,581
Be sure to thoroughly inspect the valve guides.

It is very common for them to be damaged / cracked by the side loading that occurs when the valve gets bitch slapped by the piston.
 

kumfasa

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Joined
Feb 28, 2015
Messages
125
Location
Tauranga, New Zealand
Thanks toybreaker, aside from a thorough visual inspection are there any key dimensions I could/should measure?
 

EMX5636

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Jun 28, 2008
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Good thought toybreaker. I usually recommend having the head gone over by a competent machine shop, to check/install new valves, guides, deck surface etc.
 

fuel

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Feb 23, 2009
Messages
2,161
Location
Toronto, ON, Canada
I would replace the whole head and do the valve stem seals on the replacement head. At the very least you'll be up for a set of valves and valve guides and associated machine work, and it will be cheaper to find a second hand head and fit that instead. The 2.0 DOHC N/A head is the same apart from the cams and bung in place of the turbo oil feed.
 

kumfasa

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Joined
Feb 28, 2015
Messages
125
Location
Tauranga, New Zealand
Thanks Phil, sounds drastic but might just be the easier route. So your saying this might be a good option TradeMe
 

fuel

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Feb 23, 2009
Messages
2,161
Location
Toronto, ON, Canada
yeah that looks to be the correct big port head, I would be a bit wary of how much they have planed off the surface though. You gotta ask why they did that - for instance did it overheat and warp? I would not put a head that has had a bit planed off it on an existing bottom that's near tired as it's always usually a source of bearing failure due to a sudden increase of force the bearings are not used to (from the increased compression ratio).
 

kumfasa

Well-known member
Joined
Feb 28, 2015
Messages
125
Location
Tauranga, New Zealand
Interesting thoughts. Ill talk to the guy and get his story about why the head was shaved.

No disrespect Phil, but assuming the head is straight, shaving a few thou off is only going to raise the compression ratio a gnats whisker, I struggle to see how this will cause bottom end bearing failure any more than turning up the boost a few psi.
These bottom ends are known to run up to 400hp no drama's and they must be pushing 25-30psi to do that. Surely increased boost increases the combustion forces down on to the bearings.
Am I missing something?
 

fuel

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Feb 23, 2009
Messages
2,161
Location
Toronto, ON, Canada
It's a surprisingly common phenomenon man.. and many engine builders are hesitant to take too much off the head for that very reason. It's happened to two of my cars - one I was responsible for and the other I received after the head gaskets were done.
First one was a 4G37 Galant - the 4G37 has the same stout rod, bearing and crank size as the 4G62/63 yet while dealing with a fraction of the power (about 80-90hp). It blew a head gasket just between the water and oil galleries allowing a mix but not compromising the combustion chamber, but the machine shop took a little off the head anyway. About 10,000kms later the engine developed a bearing knock on an otherwise healthy engine. Before the head gasket replacement I had 185psi even across the board and after the readings were 210-220psi.
The second was a 6A12 MIVEC Galant, of which I admit these things are not known to have the strongest bottom end. It blew a head gasket on one bank and the previous owner spent almost $3,000 on getting both the heads reconditioned, new gaskets, timing belt etc etc only to have it literally shatter one piston, bend one rod and snap another rod completely locking up the bottom end. This was due to two of the rod bearings quickly giving way and allowing the piston crowns to tap the underside of the head. He sold it to me for just over scrap value (as I had another MIVEC Galant at the time and wanted parts), and I ended up rebuilding the engine with new pistons, rods and crank to use along with the nicely rebuild cylinder heads. That engine is now running fine ever since.

The 4G63 may be fine but rod bearings which have been used to the same forces most their life often don't like a sudden increase of force and it can accelerate and perhaps exaggerate their existing wear to the point of quick failure.

My point is specifically with that 2nd hand head is that you don't know how much has been shaved off, and you could be buying into an entirely new set of problems with it. I would ask if they have a build sheet from the machine shop for that head to find out how much was taken off.
 
Last edited:

BENE38A

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Joined
Sep 2, 2013
Messages
261
Location
New Zealand
off the top off my head the spec in the factory service manual for head thickness measuring from the deck to where the valve cover gasket sits is 5.193"-5.201", if you are going to buy a used head do it local where you can inspect it and measure it.
 

kumfasa

Well-known member
Joined
Feb 28, 2015
Messages
125
Location
Tauranga, New Zealand
Thanks for the real-life info Phil. Your first example had upped the compression by ~30-35psi which is significant.

And I understand that some parts that have been operating nicely at a certain force/pressure (and would have continued to do so for some time) can fail quickly once additional forces/pressures are applied. I think we have all seen a cascade of issues along the lines of: Change coolant then thermostat dies. Change thermostat then water temp sensor dies. Change water temp sensor then a pipe starts leaking, etc...etc...

Thanks for the info Ben, I have an FSM and am a big Jafro fan and subscriber and any head that I use will get the full "deck tech" inspection.

I'm going to try and find the time this weekend to pull the head and Check it over. I'll keep you all posted on what I find and where this might take the repair process.
 

tektic

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Dec 19, 2012
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ronkonkoma, ny
You don't think coolant in the oil had anything to do with your bearing failure?
 

fuel

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Feb 23, 2009
Messages
2,161
Location
Toronto, ON, Canada
^^ there wasn't coolant in the oil - there was oil in the coolant as the oil pressure was higher than the coolant pressure. It was such a small leak that would allow oil sludge to accumulate under the radiator cap after a few days/week of driving. The oil was still nice and clean and dipstick/oil filler free of milkshake.
 
Last edited:

kumfasa

Well-known member
Joined
Feb 28, 2015
Messages
125
Location
Tauranga, New Zealand
Nearly there just need a 10mm allen head socket to get the head bolts out. I'll pick one up tomorrow.

Funniest moment so far was the creation of my "Intake manifold support bracket bolt removal tool"
Take a good look!




Just a little sumpin sumpin I whipped up.


 

tektic

Well-known member
Joined
Dec 19, 2012
Messages
1,497
Location
ronkonkoma, ny
If the DS axel is out you ca easily reach these bolts from the bottom. Even if it's in you can reach up to them but not quite as easily.
 
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