Ford Modular engine: Problem with timing chain tensioner/guide design? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 08-20-2011, 12:20 PM
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Ford Modular engine: Problem with timing chain tensioner/guide design?

First of all, I've never disassembled a 4.6, 5.0, or 5.4 modular motor, so I've never seen one completely disassembled.

However, I was reading an article recently in Car Craft where they were rebuilding the 4.6L engine in a 4 door Crown Vic to improve horsepower. It was a fairly short article with limited detail, but the point was to show how to get more power and to illustrate that the modular motor isnt too difficult to build.

So anyway, before reading the whole article, I looked at the pictures of the engine as it was coming apart. They showed a picture of the front of the engine once the timing chain covers were removed, and I took a close look at this picture. The chains were still on, but I could see that the chains ride on 2 guides in between the sprockets, one on either side. One guide is actually the tensioner, and the other is a guide. They both guide the chain inward at least a little(the tensioner pushes the chain farther inward than the other guide).

The tensioner arm appears to be aluminum with some kind of plastic/polymer/ or maybe Teflon lining it where the chain rides, and the other guide was made entirely of the plastic/polymer/Teflon.

But they didnt show any close pics of the inside of the guides with the chain off, so I couldnt see what they looked like where the chain rides, but it appears that the chain literally slides across this plastic/polymer material.

Once I noticed that, I questioned to myself whether this would create a wear problem that would require the car/engine owner to occasionally need to replace the guide or the plastic/polymer lining due to wear.

So then I began reading the article, and sure enough, they pointed out that the chain on the driver's side had worn through and was grinding against the tensioner piston. Plus, the chain guide on the opposite side of the tensioner had actually cracked and broken.

After breaking the engine down, all of the plastic/polymer liners and guides were replaced with new plastic/polymer ones that were white instead of orange.

So my question is: Is this a bad idea to run the timing chains along plastic liners and guides, and won't that eventually either break or wear out on MOST or all modular engines?

Why not come up with a better system that tensions and guides the chains with metal sprockets with good quality bearings or something?

Again, I'm no lifelong engine expert, but I do understand mechanical things pretty well, and this setup seems a little odd, and potentially problematic........

Also, is this same design used on the newer 3 valve and 4 valve DOHC modular motors, or do they use a different type of tensioner/guide setup without the plastic/polymer/Teflon? (or whatever it's made of)

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Old 08-20-2011, 06:10 PM
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I am not sure if the newer 3 valve engines use the same design, but the older mod engines are fairly reliable. When I was with Ford, I saw several in the shop for blown out spark plugs, and blown out repair inserts. You have to pull the timing chains off when doing a head, so I got to see a lot of these guides. I have seen many engines with 300,000+ Km (200,000+ miles) without issues in the chain guides. Proper oil grades and regular maintenance is key.
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Old 08-23-2011, 06:10 PM
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Quote:
Originally Posted by sbchevfreak
I am not sure if the newer 3 valve engines use the same design, but the older mod engines are fairly reliable. When I was with Ford, I saw several in the shop for blown out spark plugs, and blown out repair inserts. You have to pull the timing chains off when doing a head, so I got to see a lot of these guides. I have seen many engines with 300,000+ Km (200,000+ miles) without issues in the chain guides. Proper oil grades and regular maintenance is key.

Am I correct in my assumption that the timing chains simply slide against the liners in the tensioner arm and the plastic/polymer guide? Or is there some kind of rollers in there that I didnt see because of the timing chain blocking the view in the pictures?
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