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SOHC V6 Timing Chain Saga

2000StreetRod

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V8 SOHC not as bad

. . . Just from looking at the engine I can see why they've set it up the way they have, but I have to guess at how they're actually doing it. My guess is that this jackshaft you fellows have been speaking of is somewhere in the area of where the camshaft would normally be in a pushrod engine, It runs the whole way through the engine to a sprocket to run a single cam, while the other is run from the front.

That's correct. The SOHC V6 has the jackshaft where the camshaft is on the OHV V6. See my post Main timing chain - OHV vs SOHC for more information.

They only did that to save on the cost of having to have two different cylinder heads designed and made, and in the process doubled, tripled? the amount of expertise, time, tools and patience required to do this job. Which usually means their dealer gets paid and they get to sell you overpriced parts to fix a bad design. Those chains should be on the front of the engine like on every other automotive design. Not to mention that the system is needlessly complex, is inefficient, and has more parts to wear out (which will, because they're made to "Ford's specification").

I agree that the chains for both banks should be on the front. The 4.6L V8 has the chains on the front.


As far as your intuition about the chain guides, yeah. There are only a few engines that use guides similar to yours, and they're part of the aluminum block in some of those engines but there's a huge difference. They use roller chains, similar to a bicycle's, roller chains will only take a tiny bit of metal out and then they ride gently on the metal on the bearings in the links, these engines use separate tensioners. Their guides also don't put nearly as much curve into the chain. Before anyone crys 'oh my god metal shavings', how much do you think your hardened steel pump internals care about aluminum powder?

My old MGB had a rubber tensioner that worked in this manner, sacrifice some material initially so the design of the chain works WITH the design of the tensioner. It was 28 years old and didn't need replacing.

In the case of your engine the chain is not long enough to warrant a tensioner or guide on the working side of the chain for any reason, not even slap. If Ford wanted to be paranoid about slap they should have used an idler gear or smooth pulley, not a piece of plastic against steel, those chains don't exactly have the smoothest backsides. . .

I've owned five DOHC engined vehicles during my life (4 Jaguars and an Alfa) and all were equipped with fairly reliable double row roller chains for cam timing. None of them required pulling the engine to replace the valve timing components. However, that was many years ago and not representative of Ford's targeted purchaser today. The 4.6L SOHC and DOHC V8 uses similar chain and guide material to that in the SOHC V6 but the wear is not as rapid and replacement does not require engine removal.
 


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CDW6212R

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Eh, Ford had a pretty good OHV engine, and wanted to save money and still get the bigger heads on it. I agree that they didn't achieve long term reliability or serviceability. They did get it to work well, but that's selling, it's what they do.
 




2000StreetRod

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Transmission jack

The exhaust pipes and catalytic converters unless removed prevent using a normal transmission jack to support the transmission when pulling the engine. The photo below shows what I improvised that worked fine.
TransSpt.jpg
 




2000StreetRod

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Primary timing chain kit

The Ford primary timing chain kit (PN 2U3Z-6D256-CA) arrived yesterday. The photo below shows the contents of the kit.
MainKit.jpg

Because of the costs associated with repairing the timing chains (crane, engine stand, tools, etc.) I've decided to replace all of the chains, sprockets, guides and tensioners but not purchase any engine rebuilding components (rings, bearings, valves, ect.). I'll wait a year or so do all of that.
 




Glen4X4

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nice I will have to get a scissor jack, I was trying to think of what I was going to use to support the tranny.
 




2000StreetRod

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Balancer bolt loosening assistant

After pulling the engine I needed some way to keep the crankshaft from rotating while I attempted to loosen the harmonic balancer/damper bolt. The photo below is what I improvised and it worked just fine.
ChanBlnc.jpg

I used scrap bolts at the chain connections since the extreme force applied would probably damage the threads. I installed washers between the bolt and the flexplate to keep the chain from scratching the flexplate.
 




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Pull the cat pipes if you can to start with, those are a pain. With them out it's a good time to work on the trans. I'd do the trans side servos if I got mine off again. That and adjust the bands, far easier without the cats there.
 




2000StreetRod

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Flexplate bolt loosening assistant

The chain attached from the flexplate to the head worked so well that I decided to use the same method to loosen the flexplate crankshaft bolts. The photo below shows the revised configuration that also worked fine.
ChanFlex.jpg
 




shelbygt

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Got my parts for the primary the other day as well... thanks Dale! What a difference having the motor out to work on huh? Getting some of my parts from Rockauto.com for the gaskets I needed and new valve seals for the heads, they should arrive tomorrow. Hopfully I'll get back to putting it together in the next 2 days. I am wondering since both cams are off, will it matter for the valves be in the same configuration (slots parallel to the head) if the slots on the cam ends are 180° out? Or should I make sure that certain valves are depressed or not when setting it all back up. I remember that the right bank...cylinder #1 should have no valves depressed, but what about the left bank?
 




2000StreetRod

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cam slot offsets

I got lucky again on eBay yesterday morning. I bought a Ford new complete front cassette for $20 plus shipping from an individual who decided he didn't need it.

Actually Dave, technically it doesn't matter if the camshaft slot offsets are above or below the camshaft axis as long as they are both the same when the #1 piston is at TDC. The camshafts are the only thing in the engine that determine if #1 piston is on the compression stroke. However, I think it is less confusing to install the right (passenger) camshaft with no #1 cylinder valves depressed (slot closest to head) and the left (driver) camshaft with the CPS protrusion up and the slot closest to head. Also, I believe the camshaft tool requires the slot to be low (closest to head).
 




2000StreetRod

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Worn guide post

Here's another example of the consequences of Ford's inferior design of the SOHC engine. Because Ford chose to implement a curved guide on the traction side of the jackshaft to camshaft chain, when the guide eventually fails the chain contacts the guide post. The arrow in the photo below identifies where the chain has worn off a significant portion of the metal guide post.
GuidPost.jpg

The metal particles drain into the oil pan and are picked up by the oil pump and accelerate it's wear. From there the particles flow to the oil filter. The particles that pass thru the oil filter end up accelerating the wear of the engine bearing surfaces. This is why it is so important to utilize a quality oil filter.

I am appalled that Ford continues to manufacture the SOHC engine with this inherent design flaw that can be corrected by changing the shape of the traction side guide and it's mounting configuration. I will evaluate eliminating the entire traction side of the guide assembly and the guide post.
 




BobWiersema

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Say what you want about Fords SOHC engine but my experience with Ford has been great. The original engine came apart around 95k and Ford replaced it out of warranty for no charge. I dont know of any other manufacture who stands behind a product like that. Dont take this personal Dale but, considering that your engine is completely fried and burnt to a crisp, I think you should share in the blame. If you cook a engine to that point you have to expect something to fail I dont care what kind of engine it is.

Good luck with the repairs and keep us posted. I cant wait to see how much stuff is in your oil pan. :)
 




2000StreetRod

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No offense taken

Say what you want about Fords SOHC engine but my experience with Ford has been great. The original engine came apart around 95k and Ford replaced it out of warranty for no charge. I dont know of any other manufacture who stands behind a product like that.

You're right about them standing behind their product more than most car makers. I believe our Toyota Highlander only has a 50,000 mile/5 year warranty on the engine and drive train. However, I think Ford admitted they had a significant problem with the SOHC V6 and decided to repair the failures rather than correct the design. The design of the SOHC V8 is significantly improved.

Dont take this personal Dale but, considering that your engine is completely fried and burnt to a crisp, I think you should share in the blame. If you cook a engine to that point you have to expect something to fail I dont care what kind of engine it is. . . .

I bought my Sport in May, 2009 with 150,000 miles on the odometer knowing that it had probably not been maintained properly. In the 2,000 miles I have put on the odometer since the purchase I have added remote engine and ATF oil filters and coolers and changed the oil and filters twice. I suspect the previous owner probably knew about the timing chain problems and that is why he left it abandoned on the interstate when it broke down. It was lucky for me that the engine died due to a failed crankshaft position sensor instead of a broken chain.

Just because I badmouth Ford for the SOHC V6 doesn't mean I won't buy another one. In fact, I'm looking forward to purchasing a 1999 or 2000 Mustang GT in about 2 years. I'm interested in replacing the stock 4.6L with a 5.4L.
 




shelbygt

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Nice find Dale!
Man I can't believe how clean my motor is inside compared to the photos I have seen on here. I really don't know why it is this way at 193k. I'm not complaining though!
 




2000StreetRod

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Primary tensioner surprise

As I removed my front timing cover I anticipated my primary tensioner to look like the one in the photo below by White98.
Exp019.jpg

In the above photo the plastic and metal backing have been completely worn thru by the chain. I was totally surprised when I found the condition of my tensioner as shown in the photo below.
PrimTens.jpg

There appeared to be less than 15,000 miles of wear on the tensioner and guide plastic surfaces instead of the 150,000 miles indicated on the odometer. I began to wonder if I had wasted a lot of money purchasing the primary timing chain kit and wasted a lot of time removing the timing cover. At first I suspected that the tensioner must have been replaced recently until I noticed from the base that it was the old obsolete design. The photo below is a closer view of the tensioner and guide after being removed from the engine.
PrimWorn.jpg

How could the rear chain guide be totally destroyed and there be so little wear on the front tensioner? Well if you look again at the photo above you'll realize that the tensioner spring is broken and was not exerting any force on the chain at all. This is why I say that Ford should have continued to utilize an oil pressurized tensioner. The slack side of the chain was merely conforming to the shape of the tensioner contact surface. When I started to remove the guide I noticed that the upper mounting bolt was not even finger tight. Apparently it had vibrated loose over the years. There's a locating plug on the back of the guide about midway lengthwise. The plug fits into a 1/4 inch diameter opening to the oil line that runs horizontally across the front of the block. If the guide were to get loose enough to unplug the opening, oil pressure would drop significantly. After removing the tensioner and guide I attempted to lift the chain off of the jackshaft sprocket and then off of the crankshaft sprocket. There was not enough slack in the chain to do either. I concluded that it is extremely unlikely that the jackshaft chain would ever slip a tooth on either gear.

The photo below shows the chain method used previously to loosen the balancer bolt and flexplate bolts being utilized to loosen the jackshaft sprocket bolt.
JSprkLsn.jpg

This way I was able to keep the crankshaft at TDC.
 




Glen4X4

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I like how detailed your doing this thread. I am awaiting for my parts to arrive at the local Ford dealer so I can get to this.
 




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Dale,

I was out today having a liquid lunch with my buddy Bill and while talking about boats I thought about that sludge in your engine. A while back we cleaned up the engine (straight 6) in a used boat he bought. I remember that we used something that worked great, so I asked him if he remembered what it was, he did, Auto-Rx. So I looked it up and this is the web site. http://www.auto-rx.com/index.html

The engine in that boat he had was a disaster, Bill must have bought it from the same guy you bought your Explorer from or they both followed the same maintenance schedule. :) We used four bottles (4 oil changes) of the stuff to clean up that boat engine but we were trying to do it fast so it was probably over kill and not recommended.

Just thought I would pass the info. along to you. Money back guarantee so you have nothing to lose.

Bob
 




2000StreetRod

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Thanks for the tip!

Bob, thanks for the tip and the link to the site. Interesting reading. I plan to clean out a lot of the sludge before reassembling the engine. I'm afraid that a big chunk could break loose and block an oil return. I have a can of engine flush, a spray bottle and a tooth brush. I'll start the cleaning process as soon as I get the cassettes and oil pan removed.
 




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Dale, Did you use a nut and bolt through a hole in the jack shaft sprocket? Don't think I need to worry about moving then crank at this point, but it may be easier with your method. I have yet to tackle it as Tasca Ford just sent the parts out today, a week after I ordered them.:(
 


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2000StreetRod

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chain, bolts, nut & washers

Dale, Did you use a nut and bolt through a hole in the jack shaft sprocket? . . .

Yes. I installed a washer next to the bolt head to make sure it didn't pull thru the sprocket hole. I also installed a washer next to the nut to make sure it didn't pull thru the chain link.

I'll have to use the chain method to loosen the camshaft sprocket bolts. I should have loosened the camshaft sprocket bolts before removing the jackshaft and crankshaft sprockets and chain.
 




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