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Rachet style Chain tensioners

2252 Views 51 Replies 6 Participants Last post by  eschaider
Hey Ed--- I did get my chrome- moly tubing to create the spacers to eliminate the rachets on my tensioners. I finally got a local machinist to cut it to the 0.200 length. In the interim I had contacted Tim Elchhorn from MPR in Boyton Beach to see how he addresses this with his engine builds. He advised me as long as the rachet does not extend out from the top more than 7/8th's of an inch the rachet can be removed and no spacers are necessary. He says the spacers can be more disasterous than the rachets in snapping chains and has seen this first hand at his shop. It would be great if some others would chime in on this -that have done this modification and race a bit with a two step. I want to button up my engine and get it back in but now I'm wondering which direction I should go. Life can be a conundrum for sure----Thanks

Can Do
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This is a long-standing Hyland modification that has been used for at least 20 some odd years. Properly sized (i.e., 0.200"), they will exactly pick up the slack in a brand-new chain with the engine off. Grinding down the ratchet arm teeth provides a similar but different function.

Without grinding down the ratchet arm teeth, the ratchet will stay extended to whatever length the chain stretched to at high engine speed. So while the plunger on the tensioner will retract, the ratchet foot will not because of the ratchet teeth. The Idea of grinding down the teeth came about as a way of allowing the ratchet to compress back into the tensioner casting and not hold the chain under tension with the engine off.

The problem with this is that the hydraulic piston will compress to the amount the internal spring allows. After your engine has some miles on it, this can represent enough slack to make noise and create potential problems in the engine before the oil pressure rises to the point it extends the piston and pushes the tensioning arm against the chain. You are probably OK the majority of the time. It is the one or two times you are not OK that are problematic.

The spacer never lets the piston retract to the bottom of its well and, at 0.200", maintains a very light tension on the chain with the engine shut off. This mod will not break timing chains. What breaks timing chains is two-step launches that load and unload the cam drive chains as the engine tries to maintain a predetermined launch rpm. The on-again, off-again whipping of the drive chains eventually will break a link somewhere. Two steps with or without the tensioner mod are tough on timing chains. The tensioner mod is designed to maintain a minimum tension on the primary drive chains when the engine is shut down, so the next start is clean and silent. It absolutely will not hurt a primary chain — look at the mechanism and think about how it works.

Cutting teeth off the ratcheting arm will prevent the chains from being held in a stretched and tensioned condition after racing. Removing the ratcheting teeth will not prevent the piston from settling down at spring height or possibly lower after shutdown. The 0.200" spacers will.

When you assemble the tensioner and install it for the first time, you will discover it is best to install a single bolt, compress the plunger in its well, and rotate the tensioner into position. Once in position, put the second bolt in and begin to screw it in while holding the plunger compressed and the tensioner in position. While one person can do this after they develop a little skill for the task, it is much easier with a third hand. You will know what I am speaking about the first time you do an install.

The 0.200" spacers will give you about but a little bit less than what Matt has for free play in his setup. The decision to run the ratcheting arm is a personal choice. If something is not necessary, I tend not to use it. If you choose to, make sure you get enough teeth ground down so it is not accidentally standing proud when you don't want it to.
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There is another follow on failure attributable to the sustained chain loading when the engine is shut down.

The sustained chain loading stresses all the links and anchoring pins in the silent driver chain, which is undesirable. It also does something else that is damaging in the extreme. When the engine shuts down, and the primary drive chain tension is not released because of a locked ratcheting plunger, it loads the front cam journal on both sides of the engine pinching off the oil film. The front journal on the driverside is at the end of the lubrication food chain and gets oiled last.

When the engine shuts down, and the primary drive chain tugs downward on the cam nose because the tension has not been released, in the now pinched off oil film between the cam and the head, the #1 cam journal experiences metal-to-metal contact. The repeated metal-to-metal contact continues at each new start and roughs up the cam and the journal bearing in the cam saddle. The cam eventually seizes in the head, and the broken chain, bent valves, and broken guides damage saga plays out.

If you check, many, if not most, broken chain histories will almost always have a seized cam journal in the litany of damaged parts — for the reasons we are talking about. There are three things you can do to mitigate this;
  • The Tensioner Mod we have been talking about,
  • Use of an Oil Accumulator,
  • Use of an oil additive — I highly recommend ProLong
The Oil Accumulator is not widely used or recognized. Canton offers them under the trade name Accusump™ and Moroso as an Oil Accumulator. They can be installed to perform two different functions. The first function is pre-oiling the engine before startup. Both firms offer a kit to allow the oil accumulator to flush into the engine prior to startup. This will protect those tender cam journals that get oiled last. Their second function is to protect from uncovering the oil pickup and drawing air into the lubrication system.

After the accumulator is set up, for example, to discharge below the engine's operating oil pressure, say 45/50 psi, when the oil sloshes to the back of the pan, for example, exposing the pickup, the oil accumulator will begin to discharge its supply of oil into the oil system making up for the temporary reduction in oil volume or quality to the bearing surfaces.

Oil accumulators come in various sizes up to a 3-quart capacity. In general, they only hold about 1/2 of that capacity. Their design uses an o-ring sealed piston with air behind it at atmospheric pressure. As the engine runs, the oil pump pumps oil into the engine, and the accumulator pushes the piston up against the air-filled chamber, compressing it to a pressure equivalent to the engine's oil pressure. Fully compressed, about half or a bit more of the cylinder is oil and the other half is compressed air, so your three-quart accumulator is actually 1.5 quarts or a bit more. Buy the big unit. These things are a poor man's dry-sump!

ProLong and other oil additives are an emotionally charged topic. I was historically an anti-additive guy. I got talked into using ProLong at an NHRA event decades ago — it saved an engine for me, at that event. I have been a ProLong bigot ever since. If you elect to use it buy the gallon bottles off Amazon for $65. They are a better deal than the 12 oz auto parts store bottles for $20.
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The tensioner mod is in the TToC Dave under the Engine section. It is nine posts from the bottom immediately before the Crank Tech I & II postings.
No, you are not, Dave. Check the TToC in the 03/04 SVT Cobra Forum
Got it. I saw a set of those for sale somewhere and wondered what they did. Do you make them? What would a set cost me?
I don't make them, Dave. They are pretty simple to make, as you can see in the post. The problem is access to a lathe. The easiest way to get them is to go to a machine shop and ask him to make two spacers 0.750" in diameter that are 0.200" long. Use 0.120" wall tubing. Unfortunately, a lot of the stuff floating around was made by someone who never had access to an original part from Hyland or a copy of his print for the part, and most importantly, they do not know how to determine the proper length. As a result, they are all over the map length-wise, making them bad choices. If you point out the length whoops to whoever is selling them, the attitude is frequently something like, 'who made you the arbiter of length for these?' Don't waste your time, go out and get a set made properly — it is cheap money.
Ordered my Gallon jug of Prolong engine treatment today from ebay for $68 --my machinist told me it would be the middle of the next week before my spacers are ready-- getting 5 sets cut. Will always have a set of these spacers on hand from now on. The 3 qt. Canton Accumulator is next on the list. Ed told me about Mcmasters - Carr for the Chromemoly tubing necessary to make the spacers happen- 3/4 OD x 0.095 ID x 0.200 in length chamfered on both ends.The tubing was around $22.00. I had an engine failure too and am nearing the completion of my new build and looking forward to getting my car back together-- now scattered in pieces in my shop.
Not that it is a lot of money, Tom, but when I made mine, I forgot to check aircraft spruce for 4130 tubing. Had I gone to aircraft spruce the tubeing would have been a bit cheaper but not a lot.
I have the cast ones from a 94 Mark VIII engine (my shortblock is from there). I'll see if we have any of that tubing in our metal cage. Thanks!!

The cast iron tensioners are much preferred over the later plastic body units, Dave. Make up some spacers and you should be good to go.
If anyone has the plastic tensioners Tom (Motorhead4Ever) spoke to earlier, his fear for the longevity/durability is spot on. Just get a set of cast iron units. Here is a link to a Parts Geek listing for them => Left & Right Tensioner The left part number is - 17877-07928337, and the right part number is - 17877-07895506. As of this posting, the price is $53 each. There are Mellings and Cloyes on the same page for even less.
It might not work, Tom. The issue is the ID on the sleeve needs to be large enough to allow the spring to fit through. I don't have any pieces at the house to check. I am getting ready to go up to the race car garage and I believe I have a spare tensioner up there I can measure spring OD on. Actually, the price difference between McMaster and Aircraft Spruce is not that significant and McMaster has the tube in stock.

When I get back from the shop tonight I'll update you on spring diameter. If yours are already out, disassemble one and measure the spring OD. That will be the limiting ID on the spacers and determine your max wall thickness.
Sorry Tom, late night, and I forgot to post up. The 0.095" wall tubing will work. The 0.125" tubing might work as well. I had one spring that would go into a 0.125" wall tube, and one would not. I believe one spring was OEM, and the other was aftermarket — and I can't tell which is which. To be safe, the 0.095" wall tubing will work all the time. Be sure to lightly scotch bright the OD to remove any foreign material and clean up any surface imperfections, so you have a nice smooth round spacer.
I have 2 sets of the cast iron tensioners so I'm going to go ahead and make the spacers for all 4. I'm planning another build with some DC heads I found. I do have the crossover mod done. I also am going to have billet gears. I'm going to look up the reverse tensioner mod. I saw MMR had a set with it flipped. I degreed my cams in when I first built it and they were around 3 and 6 degrees off between the cams. That added to the potential extra 6 would surely explain the differences in the stock setups and the freak engines. Thanks!
Dave, before you buy be sure to check out Cobra Engineering <= clickable. They also offer the corrected passenger-side secondary chain tensioner. The link I provided will take you to an opening page where they offer a package deal on the corrected tensioner body and a set of HD dowel pins among a number of other very nice items.
Thanks, guys. I just wanted to be sure you knew you have options/alternatives.

Sometimes we win without even knowing it — until it's all over ... :giggle:
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So, I got my tensioners off, spacers made, and then started to put them together. Uhoh! I have different tensioners than what I've seen all over. Consensus was to get a new ford set so I did and the spacers work. I'm leaving the ratchet stop out. I know they say for racing only but if this falls apart, I'm not thinking this one piece is going to be want causes a catastrophic issue. That'll happen before. So, pics of my tensioners (that I find no part number or likeness anywhere on the net) and the new ones with spacers installed. I really think they could be slightly less than 0.2" but that's me. I'll go with what's recommended. Thinking though, Wouldn't it be better if the check ball was removed insode the tensioner as well so it could surely collapse onto the spacer stop to ensure it doesn't stay pumped or do they bleed down anyways?

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The reason for the spacer is to eliminate the need for the ratchet. A 0.200" long spacer will set the idle tension for the chains. When the engine speed increases and the chains begin to stretch, the engine oil system will project the plunger outward taking up the new found chain slack. When you let off the throttle and the engine speed decreases, the previous chain stretch disappears. If you have the ratchets in place they do not allow the chain to relax and will maintain chain tension as if the engine were at high rpm.

The net, net bottom line is the chains, and other expensive parts are unnecessarily abused by the presence of the tensioner ratchet in a performance focussed version of the engine. Even worse, when you shut the engine off while using a chain tensioner ratchet, the chain tensioner ratchets continue to tension the drive chain and pinch off the oil film between the cam's #1 journal on each side and the saddle in the head. That means at the next cold start, you have a metal-to-metal abrasion occurring until oil gets to the cam journal.

The cam journals are at the end of the engine's oiling system food chain and get oiled last. Because they get oiled last and because they are experiencing a metal-to-metal style of abrading contact, the bearing surfaces begin to accumulate surface damage. Eventually, the surface damage is sufficient to seize a cam, ruin a head and break a chain. At that point you will begin to destroy a significant number of other costly parts also.

The oil check valves in each tensioner are different and should not be intermixed or left out. They are a key part of a successful operating tensioner.
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The issue with the oil checks in the bottom of each lifter is proper tensioning. The oil supply for the driver side comes off the main pump feed before it enters the main oil gallery. The oil supply for the passenger side comes off the main oil gallery at the far end of the galley after everything else in the engine including all the lash adjusters in the passenger side head have been oiled. The different bleed-down valving reflects the different positions each tensioner has in the engine's oil feed and delivery system. One tensioner is at the front of the oil feed line ahead of everyone else and the other is at the end of the oil feed line after everyone else. The different check valve performance is designed to make them operate as if they were being fed from the same position in the engine's oiling system.
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It is hard to say without more information but that is a good bet.
Not that I know of Kirk but that does not mean one does not exist. Let me sniff around a bit and see if I can get a better answer.
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I checked with our Grand High Wizards and they inform me there is no way to do this. :(
I had hoped to have better news for you but not his round.
I know the routine well, Kirk. I'm one of those binder types myself. Don't forget the TToC that Screamn03 started way back when. It is probably the motherload of all things Terminator.
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