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Figure 1

Figure 2

EngINtel: Practical Builder Tips To Common Questions

Since you all indulged me last month with editorial musings, this month will be a couple of Practical Builder Tips (PBTs) that should keep you out of hot water from time to time. They’re somewhat generic but have been popping their ugly heads in all types of engines and they have no manufacturer preference so no one is immune.  

First are tubular camshafts. They are light and hollow, they have cam lobes positioned on a spline and then the tubing is swedged into the lobe pieces. Frankly, these are the ones you still have a tough time getting used to.
As we can all attest, a real man prefers to feel that solid heavy cast iron or steel in his hand. At least you know that what you have was machined out of one piece of metal, not some erector set creation that some engineer dreamed up.  Well, be that as it may, tubular camshafts are here and they are here to stay.  

Many of them will run live with oil running through the tube and actually have small bleed holes in the cam lobes that enhance lubrication to the follower regardless of the type. The concept is great – but there is a very mundane and very important step that you need follow whenever you clean these camshafts. That step is to clean them THOROUGHLY. Too often, there is not a good inlet for you to properly clean and brush out the ID of the tube-cam and you will likely have to remove a soft plug in most of them  (see Figure 1).

On the left you can see that there is a soft plug in the end of this tube-cam and on the right you can see that there is a ledge to determine drive depth. I strongly recommend that you measure the depth prior to removal of the plug so that you know – regardless of a stop being present – how deep to drive the plug back into the cam tube.  

Another heads up on these camshafts is a warning that those soft plugs are invariably some non-standard size, and you may have to go on a journey to find the right one. A measurement prior to removal would be a good idea here as well. Even with all the hassle it is a worthwhile step. Cleanliness is next to Godliness when it comes engine remanufacturing (see “When It Comes to ‘How Clean,’ Do You Really Know?” page 34, November 2006.).

This next PBT covers a situation that’s a lot more common than you may think, and can be the source of all kinds of engine failure warranty dollars if you miss it.  There are many engines out there these days that are either single- or double- overhead cam engines, and many of them use an oil pressure controlled chain tensioner. Belt-type cam drives typically will use an independent hydraulic cylinder or be a spring-loaded type.

What happens if you have an oil-fed tensioner that starts to hemorrhage oil? You end up with a timing chain that becomes footloose and fancy free and can cause the following small problems: a horrendous noise and/or clatter, the chain slaps the timing cover and damages it to the point of replacement; the cam timing can be messed up enough to crash the valves; or worse yet, it can destroy a block.  Suffice to say there are going to be all kinds of problems that will arise.  

Well, what if you did everything right and bought all new components?  

Take a look at Figure 2. The chain tensioner on the left has a deficient casting. The area circled has a casting bubble and a thin casting that will fail to properly seal against a block. The tensioner on the right is what you are looking for. This will seal and work properly and has no chance of oil hemorrhage.  

Now before I start getting emails from every manufacturer in the industry, let me say this: none of us is perfect and there is no slam.  This information is a pay attention “notice” for those of us out there that have to use those components and want to avoid potential costly warranties. That is why we all have quality control departments – because we are not perfect but striving to get there each and every day. 

I have a friend with a life mantra that says “Seriously Flawed But Improving Daily.” I like that because it says that though we can never be perfect we should never stop working at trying to get there. Kind of like golf, the game that you can never win but can only get better at.

Remember, we’re all in this together.