My v6 Drag Week build

[c2xejk]

You may have had the timing belt jump time and do valve damage (low comp #'s). I experienced this when my power steering belt sheared and wrapped a piece of belt around the crank sprocket resulting in all 24 valves being bent. It would take a bit to shear the woodruff key on the 3.5 as it is pretty beefy IIRC. I know I have sheared the indexing roll pin on the crank pulley twice, bit I have a 36-1 wheel welded to the pulley and am not using the stock crank sensor.

EDIT: regarding repairing things, I had visible contact marks on my pistons and all I did was swap my heads with a known OK set (valve-wise, stem seals could use replacement...). I also got a full set of replacement valves off of Rock Auto fairly cheaply but haven't used them yet.

The belt is turning and the cam sprockets are off by more than a tooth (~90 cam degrees when I was looking...) If you do some google searches, you can easily find cases of the woodruff keys shearing (and/or doing damage to the crank or sprocket...) I will know for sure once I tear things down...

I am in the process of finishing several other small projects that are occupying the space in my barn... In the next day or two I should be able to get it in... for a full teardown.

I have done some looking and there are a couple yards near hear that have the heads... (plus ebay.)

I am wondering what the difference between the Diamante heads and Montero? For the mater, I think I can use some from a 24v 2.5L/3.0L, bunch of those in some of the U-pull-it yards...

Pull the valve out of your compression tester and attach an air line to it. Should be easy to see if you have a massive leak at the valves.

Yup, I am going to do a leakdown test...

[Ondonti]

The belt is turning and the cam sprockets are off by more than a tooth (~90 cam degrees when I was looking...) If you do some google searches, you can easily find cases of the woodruff keys shearing (and/or doing damage to the crank or sprocket...) I will know for sure once I tear things down...

I am in the process of finishing several other small projects that are occupying the space in my barn... In the next day or two I should be able to get it in... for a full teardown.

I have done some looking and there are a couple yards near hear that have the heads... (plus ebay.)

I am wondering what the difference between the Diamante heads and Montero? For the mater, I think I can use some from a 24v 2.5L/3.0L, bunch of those in some of the U-pull-it yards...



Yup, I am going to do a leakdown test...

All I know about the 24v heads is what was said about how the heads don't match up well with the smaller displacement blocks and the 3.5 works better. I wonder if the valve sizes are actually the same and ports the same. Surely google has the answers.

[Shadow24]

2.5/3.0/3.5 24v SOHC heads should be identical castings between all chassis. Cams are the only difference. If you ported the heads, maybe just R&R your current heads with new valves, guides and seals? otherwise the fastest way is a quick and dirty head swap with some 2.5/3.0 heads. If you go distributorless, the 3.5L Montero has the factory blockoff for the rear head's distributor hole.

[Vigo]

All I know about the 24v heads is what was said about how the heads don't match up well with the smaller displacement blocks and the 3.5 works better.

Well the 2.5 was actually debored instead of destroked which is kind of dumbtarded. Otherwise, like Shadow24 said the heads themselves are all the same.

I know this fix will not be fun but unless the crank snout is ruined it should not be TOOO horrible of a repair. I guess the real question is why did it happen and how do you keep it from happening again?

[c2xejk]

Ok, I did a leak down test on the front head. 96%, 98%, 98%. The heads are stock...

The 3.8L heads are unique. They have larger valves and combustion chamber. Using them on a 3.5/3.0/2.5 would significantly decrease the compression...

[Shadow24]

Sounds like pulling the heads wouldn't be a bad idea, see what you find valve-wise. Then you either can get JY heads or refresh your current heads and go from there. The SOHC heads are usually pretty common in the JY from what I have seen.

[Ondonti]

I think just dumping pressure into the cylinder is simpler. You can hear each leaking valve. I wonder if there are some cheap replacement valves available or something pricier that will fit and work.

Solid timing tensioner mod is common for 24 valve guys. The hydraulic sucks and people who use it never reuse it.

[c2xejk]

Those numbers are generally an improvement over the results shortly after the rebuild... Especially the last two...

Did some searching and I am unable to find a tensioner for the 3.5L 24v SOHC engine. I can find one for the DOHC, but not the SOHC. Apparently the bolt pattern is different... That said, it looks simple enough that I might consider fabbing one.

[Shadow24]

Rock Auto lists valves for an 01 Montero 3.5 at $4.84 ea. (exhaust) and $3.64 ea (intake). Valve stem seals are $20 for a set too. Valve guides are $1.64 ea (exhaust, sold in packs of 4) and $1.94 ea (intake, sold in packs of 4).

Hydraulic tensioner also listed for $53.79

I might have to order some guides for my spare heads at some point too....just in case.

[c2xejk]

Unless you have a significant problem with the guides in the head, I would not bother with new ones. You are better off having them relined by a machine shop. Including labor, it will be cheaper to reline. And it is less trauma to the head.

Also, many modern heads do not need work done to the guides unless they have a LOT of miles or physical damage...

Before you buy a bunch of valves, you might want to get samples. Some aftermarket valves are better than stock, some are worse than stock.

[Shadow24]

=glances guiltily at a box containing a complete set of valves and valve stem seals=

I vaguely remember you mentioning that same piece of advice a few years ago when I bent my valves....

At least you can go off of my experience and not be too worried about the pistons and heads

[c2xejk]

For those playing along at home, I just finished stripping down the front of the engine. The crank sprocket key is fine. As is the slot for the key in the crank and sprocket. The timing belt is fine too...

Best guess is that Brent called it when he mentioned the hydraulic tensioner... With that in mind I am attempting convert the hydraulic tensioner to be a static tensioner. I will post pictures once I have it all figured out...

[Vigo]

So you verified the cam timing to be off? Ill be interested to see what you come up with for a manual adjuster. Could just see if one or two 8v tensioners will bolt into any convenient holes on the front of the block.

[Ondonti]

btw what I said above doesn't mean everyone goes solid, it just means people don't try to get away with using old hydraulic tensioners, and they don't want to use anything not OEM. I think they are way too paranoid about OEM parts for things that don't matter, the tensioner might. They are also scared of solid setups. I did a quick check and people mentioned that older ones could slip even at low rpm startup. Something about them sticking. I know I have had a serpentine tensioner that would stick and I could make it work by turning it manually towards the belt. Not a good idea for your valvetrain.

I feel that I am very aggressive on the 12 valve timing belts, I make no attempt to be careful when setting the belt. I basically pry the pulley hard with a wrench and lock it down. On a fairly loose belt it might max out the adjustment slot. I have only ever purchased 1 new timing belt and that was in 2005. I think for 24 valve setups almost all of their failures are due to the tensioner sticking (or even leaking) but they change everything on their cars because the book says so. The people who change belts and not the tensioner....hah. Funny response I found when googling mocked people who said adjusting timing belts at certain intervals was "too annoying" since he knew those people are the type who would replace every "tune up" part on the entire car at the same interval.

Once you have failure like this you probably don't want to chance the tensioner. At least get a new one.

[c2xejk]

The one on the engine was a new one... It came as part of the timing belt kit that I installed during the last rebuild...

[Ondonti]

The one on the engine was a new one... It came as part of the timing belt kit that I installed during the last rebuild...

Well I would assume its not OEM and while I don't normally care, I couldn't say that equates to the same level of assurance. You had a problem so you gotta kick out the first suspect. Belt skipping seems to almost always be faulted to the tensioner except in cases of catastrophic failure.

[c2xejk]

Already built the solid tensioner. None of the internal parts showed any issues.

Here are the parts from the hydraulic tensioner that I used


Here is the assembled and installed solid temperature.



I did a compression test, 175psi on the front head and 180psi on the rear head. So no bent valves!

[Ondonti]

Hey Ed, is there a roller or what on the end? I don't know exactly how they work. Last picture is fuzzy. Glad your car ran poorly for easy to fix reasons

[c2xejk]

The tensioner pulley rides on carriage. The tensioner pushes on the carriage. The pulley can be rotated to adjust the "initial tension".

I will see if I can get a better picture.

[Vigo]

It's a pretty common setup. You're supposed to adjust the eccentric tensioner pulley so that when the hydraulic tensioner is released it only pushes out a very small distance from its housing. Of course with your setup i dont think that distance matters any more.

So is the entire housing threaded for that bolt and the nut is just a jam nut? What is the set screw pushing on?