The Stovebolt Site Forums The Shop Area Engine Shop Pros and cons of reversing the lower timing cover bolts

I for one can see no benefit in doing this.
I like to be able to pull the front main for bearing inspection and shim removal on engines that have shims.

If I had a cam failure I would want to pull the pan to clean it out any ways.

I know brokenhead has a reason he likes it but I cant remember what that is.

What do others think?

I liked it because I didn't have to take the pan off to remove my cam. It hadn't technically failed, but due to the valves seizing up it had started to show signs of impending failure. There was some other thing it came in handy for, but I don't recall right now.

I'm with Dave on this one. If your are into the engine heavy
enough to be pulling the cam, your only a few minutes away by
dropping the pan also. GM had to have a good reason for
building them that way for all those tens of millions of units.
If your seeing signs of impending failure in the top end then
it sure would't be a bad idea to take a look at the bottom end.

dg

I'll admit years ago I did just that because it was, "Hey, that's a neat idea. Think I'll do that." Guess what. Done and never came off the engine again. So yeah, I agree, for most of us, not needed.

The only reason I can think of doing it is if a person plans on trying multiple camshafts in their motor. I'm not to sure how many different cam profiles are even available anymore for a 235.

I like this mod because it gives you the OPTION to remove the cover without removing the pan. As said above, if I were going deep enough to remove the cam I'd also remove the pan. However, if the timing cover had just a leak, I'd be glad I did this.

No Denny, it wasn't signs of impending failure on the top end like you are thinking, it was (and still is) a complete, new rebuild, I had installed positive type seal on the valves, now I don't know if it was the seals or the fella didn't give me the proper clearance on the exhaust valves. Whatever the case, I had 3 or 4 valves seize causing a lot of strain on the cam, it hadn't actually lost any metal, just a couple of spots that were obviously the beginnings of spalling, barely noticeable on two of the lobes. Which if I had left it in would have failed spectacularly somewhere soon down the road. I like Sweets' take on it, you have the OPTION of removing the cover without removing the pan. And as I don't have shims, I will never need to adjust them. If you are assembling your engine with shims, it might pay to leave them alone. I still think the valve seals should have worked though......

GM may have had reasons to do it at the time, but they had some better reasons to never do it again since then. I haven't met anyone that was sorry they did the modification.

If more folks had grown up around an independent shop in the mid-1950's like I did, the design would make more sense. Ring/valve jobs came pretty often back then, and the top quality shops ALWAYS adjusted bearing clearances in the process of a re-ring job. It was not uncommon to do a ring job every 30-40K miles back then, mostly due to abrasive wear caused by dirt that got past the oil bath air cleaners of the day.

The adoption of disposable paper air cleaners and PCV crankcase ventilation systems that used clean, filtered air to vent the crankcase doubled or even tripled the expected life of the average engine.
Jerry

Hotrod brings up a good point. Back in the fifties, when you spoke of roads, you meant dirt roads. If it wasn't dirt, you would specify it as hardtop. Today, when you speak of roads, you mean paved road. If it isn't paved, you specify it as a dirt road. Its easy to forget about the changes over time. Dirt kills.

Even on engines without shims between the block and cap I can make a case for not doing this modification.
On a high mileage engine it is not uncommon for the main bearings to see wear. This will show up as low oil pressure on the gauge.
Through the years I have worked on many of these engines. There are two fixes for this, both require pulling the main caps.
Most expensive is to replace the bearings. Second is cheap and easy, (if the inserts are not too bad), and most people do not even know about this process. It was common practice in the old days to shim between the insert and the cap. This forces the bearing closer to the journal. In the old days they sold tapered shims just for this. I even do this on fresh rebuilds if the clearance is not right where I want it.