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Timing Guide Pivot / Dowel Upgrade

43K views 107 replies 30 participants last post by  cpask8 
#1 ·
Some of you may have read Michael's (rtusnake) post on the special upgraded timing guides/pivots he made. His thread is here => Timing Guide U/G The problem with ModMotor aluminum blocks is that Ford downsized the dowel anchor where it goes into the block from an 8 MM pressed in dowel pin on the iron blocks to a 6 MM screw thread dowel on the aluminum blocks.

Here is a picture of the two pivots side by side.



When you go to higher spring rate valve springs, fast ramp cams, use a two step or a WOT box these guys take a terrible beating. To get a sense of the abuse I believe AJ (Mofasta) has a pic of his crank snout timing gear in his build thread. The teeth are all beat up from leaving on the 2-Step.

When one of these little diddy's break it typically costs you valves, guides and a fresh valve job. If a valve head breaks off, the list of carnage will include a block, head(s) and pistons. The fix is to get rid of the weak link.

To date the only source I have seen for a fix is Michael. He was motivated by one of the failures I described himself. His solution was to rebuild with better stronger pins and is extraordinarily good as you can see from the visual in the picture above.

I got a set of these from Michael a little over a month ago. I had a mill so installation was pretty straight forward. I liked the fix so much I started to look for an easier install method so it could be done without a mill for anyone who wanted to take advantage of the upgrade.

Historically the challenge in performing the modification was and is the need to drill and tap the holes parallel to the crank main bore. Not an easy task without a mill. JamesHell and I were talking about a fix and the challenge to install it. James came up with an idea production shops use when the have to precisely locate holes or fasteners and can't or don't have access to a mill. The fix is a fixturing or jig plate.

The plate is registered off known good locating points and is lightly held in place with bolts to prevent movement during the machining process. The trick to building the plate was a block print that we could pick up the timing cover dowel locations and the guide pivot / dowel locations. With a little perserverance we managed to get a print for the front of the block with the locations we needed.

James is fabricating the fixturing plate as I am typing. We are waiting for some parts to complete the first one. The plate will look like the drawing below;



The holes marked guide pin are the current tensioner pivots. The two lowest holes on the plate are the timing cover dowel pins and the other three holes line up with existing bolt holes on the timing cover to allow firmly attaching the fixture to the front of the block. The guide pin holes are precision located, reamed to take hardened drill bushings.

Two different types of drill bushings will allow you to accurately place and drill the pivot holes so they are parallel to the crank centerline. If you put a Home Depot drill stop on your drill bit you will not drill into your water jacket. After drilling the bushings are swapped out for the second set that are designed to keep your tap perpendicular to the block face as you hand tap the holes for Michael's 8MM replacement dowel/stud.

James is pretty much finished with the basic plate at this time. We are currently waiting for the drill bushings to arrive.

If you ever wanted to fix this tender spot in your block but hesitated because you couldn't, didn't or wouldn't be able to get mill time (and dollars) to do the job this is your chance to not only fix your current block but any future blocks you ever get for the car. Michael has the studs, James has the tooling and you can have a much more reliable block.
 
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#2 ·
Ed, I also have a set of these on my shelf waiting to go in and have been contemplating a way to install them at home. Thus far I only came up with using the 8mm die set on the surface and tapping through it to keep it square to start the tap. Was debating on finding a piece of some sort of metal stock an inch or so thick and drilling a hole through it on a drill press and using the same concept to get the hole drilled. While much more "rustic" and taking a bit more of finesse, it could work. While my descriptions may leave a bit on the table, it makes perfect sense in my head......lol I had not thought near as deeply into it as you have. Your idea looks awesome, but would need to be on a level of one person has it and lends/rents it out. Unless you plan on doing a lot of these. If you do make one, can I borrow it? haha.
 
#4 ·
I agree with you Eddy. I think your approach would work well to keep everything parallel to the crank - it sort of mirrored my original thinking. The drill should follow the existing hole but I was concerned about the drill's ability to walk and that is what got me thinking drill bushings. The fixture plate just takes the potential for the drill to walk out of the picture.

James is pretty impressive when it comes to fabricating and keeping it in the affordable ball park. I think this is going to be a real nice way for anyone to be able to put these in as accurately as if they had a vertical mill. Best part is we took the dimensions and locations off a Ford print so we know they are dead nuts on.

\

Here you go Ed>>>>

Thanks AJ.

For those who have never looked inside, this is part of the damage a two step does to the insides of your engine. It beats up the gears, the chains, the wrist pins, crank, rods and pistons - did I mention oil pump? On a 4V it kills the cam drive components and if you have a built Teksid or Aluminator it is brutal on those little fulcrums - even more so if you use aftermarket valve springs.

The work Michael (rtusnake) did for his own engine has not been done by anyone in the industry. The guys who break these things just buy new parts and have at it again. I am not sure when his pieces are gone there will be any follow ons, so if you have been thinking about this and have hesitated because you don't know how to reasonably get them installed, here is your chance to do it right and also on the cheap.

Ed
 
#3 · (Edited)
When you go to higher spring rate valve springs, fast ramp cams, use a two step or a WOT box these guys take a terrible beating. To get a sense of the abuse I believe AJ (Mofasta) has a pic of his crank snout timing gear in his build thread. The teeth are all beat up from leaving on the 2-Step.
\

Here you go Ed>>>>

 
#8 ·
I am going to run one of these off this weekend. Then test fit it before running more.
The drill bushings will be here in a couple weeks.
I figured out how to cut the cost on it. I will include only one of the bushings for drilling and only one for tapping. Considering the bushings are about $10 a piece that will cut the cost $20. This should bring the cost of the tool down to around $80. This is without the drill or tap. I will check on that.

Any input is appreciated.
 
#9 ·
Just picked up from some from rtusnake/Michael for my Teksid build inwork right now.

Thanks again for all the hard work everyone is putting in on this. I will be having my machine shop install mine along with the crank snout stud mod.
 
#10 ·
Damn. A day late and a dollar short...

I installed my dowels with the block on the stand using a hand drill and a hand tap. One side... perfect. The other side (coincidentally the passenger side... the one that fails the most) didn't make it home perfectly tangential to the block.
 
#12 ·
whats interesting is kNOW I have WAY more passes on my car on the 2 step than AJ and my crank gear looked perfectly fine
 
#13 ·
You have more passes on your engine than anybody period, Jake!

I think one of the contributing factors for AJ may have been the cog drive for the blower. With a serpentine belt the drive system can provide a little buffering through slippage as the blower speed is manipulated. With the cog drive and no slip possible, the blower rpm changes have to be instantaneous and the inertial tug from the rotors at high speed will not get buffered by the drive system.

Ed
 
#22 ·
mine looks just like Eric's..
 
#25 ·
This is another great contribution to our favorite money pit.

I'll be happy to buy one when they become available. I have a Teksid block sitting in a friend' shop.

I've been picking up parts for quite a while now.

The real money grabber will be the crank work or just a whole new billet crank.
 
#31 ·
Prototype

Well after some work on the machine last week I finally had some time tonight to get the first one done.

Automotive exterior Metal Wood Auto part Fashion accessory


Those are the tap bushings. I am still waiting on the drill bushings.
I think I am going to have to drill the dowel holes a bit larger. They seem very tight.

I will let you all know when I have confirmed it will fit.
 
#33 ·
+1^ James!

I know there are several guys who have stepped up and gotten Michael's Vitamin C enhanced chain guide pivots. This fixture will allow you to install the pivots correctly without buggering up your block and cost you less than the machine shop time. Best part is you can use it again and again for every new block you get.

Thanks for another great tool James.

Ed
 
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