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Good news everyone. I've decided to start a thread pointing out known differences between the 5 and 6 bolt 289 engines. This has cost me some money over the years because of the assumption of parts interchangeability that were not interchangeable.

I would like to start with the clutch equalizer bars. Because this was the latest mistake of mine, and I have the pictures on hand.

The lighter color equalizer bar is for a 6-bolt 289 and the darker is for the 5-bolt. Notice the extra length of the 5-bolt bar. This makes a big difference, obviously because the 6-bolt bar wont span across the distance from the engine pivot to the frame pivot of the 5-bolt set up.





More to come later. Feel free to correct me or give insight of you own.

Other differences to come:
Bell Housings
Timing Covers
Harmonic Balancers
Timing Chains
 

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How about button head bolts for more exactness?
those are too long to use as buttons. they also need at least on hole for the thread to go through. i dont use bolts to button my shirts. rounded top allen head bolts will do. they can also be machine screws that accept the screw driver phillips owns or the one flat head owns or a star or peter torx bit. :pirate::pirate::pirate::pirate::pirate::pirate:
 

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This will be a great thread I'm sure! I myself ran into this issue back last August and had a hilarious time adapting a six bolt engine to fit a five bolt setup.

I'm curious, what is the difference with the harmonic balancers? Do you mean the stock HBs? I found a HB for a 6-bolt fits a 5-bolt just the same.

Another difference that comes with the bellhousing is the flywheel size, I found.
 

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Discussion Starter #12
You guys are funny.

So on to the timing cover and harmonic balancers. The standard 5-bolt timing cover came with an oil fill tube located on the passenger side. Because of this, the 5-bolt block has a hole in the front of it to let the oil flow through the timing cover tube into the lifter valley. (In the red outlined area in the picture below.)



The 6-bolt timing cover simply has nothing to take its place. Both timing covers will "fit" but a 6-bolt cover will leave the hole uncovered and accessible from the outside. So debris can get in and oil can get out. (Indicated in the image below.)



I didn't like the look of the oil fill tube. So I removed the tube from the cover and machined a plug to fit in its place.
_

This part could use some more data. I had one experience with an aftermarket balancer that this is based from. So some other experiences would be good. Also I don't have pictures of this one.
The standard 5-bolt harmonic balancer is somewhat thin and then steps down to the external counter balance. Choices of aftermarket balancers are limited because of the extra thickness. They will fit the 6-bolt with out a problem, but will interfere with the cast in timing pointer of the 5-bolt timing cover. If you have a 6-bolt timing cover mounted of your 5-bolt engine this shouldn't be a problem.
 

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I'm curious - not sure what you mean about the HB being "somewhat thin and stepping down to the external counter balance"? I didn't ever have the original HB on my 5-bolt so I have no frame of reference. However, I now run a standard Summit Racing HB on my car with no problem. I've got the 5-bolt timing cover as well.
 

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I'm curious - not sure what you mean about the HB being "somewhat thin and stepping down to the external counter balance"? I didn't ever have the original HB on my 5-bolt so I have no frame of reference. However, I now run a standard Summit Racing HB on my car with no problem. I've got the 5-bolt timing cover as well.
This is one of the variations I was wondering. Maybe its some aftermarket HB's. I first purchased a HB simular to the one below.



I found it would not clear the cast in timing pointer on my 5-bolt because of how thick the largest diameter portion was, but it didn't have any troubles with the 6-bolt timing cover. So I went to a more stock HB similar to this one. Notice how thin the largest diameter is. Then the diameter of the counter balance is smaller. This let the cast in timing pointer of the 5-bolt sit inline with the largest diameter of the HB.

 

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This is one of the variations I was wondering. Maybe its some aftermarket HB's. I first purchased a HB simular to the one below.



I found it would not clear the cast in timing pointer on my 5-bolt because of how thick the largest diameter portion was, but it didn't have any troubles with the 6-bolt timing cover. So I went to a more stock HB similar to this one. Notice how thin the largest diameter is. Then the diameter of the counter balance is smaller. This let the cast in timing pointer of the 5-bolt sit inline with the largest diameter of the HB.

Thanks for posting this. I was just getting ready to buy a new HB for my 260 5 bolt.

Please keep this thread rolling.
 

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Interesting! That Summit damper that you posted a picture of is the exact one that I have on my 5-bolt :)
 

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When I sent my engine out to be balanced, I had to get a new HB, so I ordered this one from Summit. Its the thick shiny one.

https://www.summitracing.com/parts/sum-163289/overview/make/ford

After getting it, and looking at it, I decided to go with the Dorman one (from Summit) as it had a more original look to it. Its the thinner black version.

https://www.summitracing.com/parts/rnb-594-275/overview/make/ford

Neither are SFI approved, So if its a requirement at a track, I'm out of luck. Not that I will be in any class where it is required..... :grin2:
 

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You guys are funny.

So on to the timing cover and harmonic balancers. The standard 5-bolt timing cover came with an oil fill tube located on the passenger side. Because of this, the 5-bolt block has a hole in the front of it to let the oil flow through the timing cover tube into the lifter valley. (In the red outlined area in the picture below.)



The 6-bolt timing cover simply has nothing to take its place. Both timing covers will "fit" but a 6-bolt cover will leave the hole uncovered and accessible from the outside. So debris can get in and oil can get out. (Indicated in the image below.)

I've never heard of a "6 bolt timing cover". I think you'll find that all production 289 timing covers, for both aluminum and cast iron water pumps, as well as some early 302 covers, will have the casting that covers that hole. The later covers to fit both 302 and 351W don't.
 

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I think you'll find that all production 289 timing covers, for both aluminum and cast iron water pumps, as well as some early 302 covers, will have the casting that covers that hole.
Nope, that block is used with a timing cover with the oil breather/fill provision (hole) that covers that area, later covers don't.

:cheers:
 

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Nope, that block is used with a timing cover with the oil breather/fill provision (hole) that covers that area, later covers don't.

:cheers:
You mean like this D3OZ cover???



Tomorrow I'll go out and snap a photo of the "6-bolt cover" on my '66 which also would cover this area on a "5 bolt" block.
 
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