Reinstalling pushrods

[Luvjet]

Good morning everybody! I'm doing a complete top overhaul on my '50. All the airport visitors "experts" are coming by for advice and a cold one. The list is split right down the middle as to whether The pushrods should be matched for each cylinder. Some guys say it doesn't matter at all since they are hydraulic, others say you will get better performance if they are matched. HELP!

[c170b53]

Were some of the guys wearing bright colored leather jackets advertising smokes and the like?

[Luvjet]

Were some of the guys wearing bright colored leather jackets advertising smokes and the like?

No ,but they were wearing funny hats.

[HA]

what's to match, you're just looking to get the clearance correct with the lifters bled down and you'll use different length pushrods to accomplish that. once they are within specs there's no difference, that's what the hydraulic lifters are for.

[Luvjet]

I Think ,HA, that your response answers my question. Some guys around here are saying that it doesn't matter about the pushrod length BECAUSE of the fact that the pushrods are hydraulic.

[4-Shipp]

Hey Don,

I finally get back in the air and you break?

Make sure the lifters and bled down and the zero lash clearances are correct! The limits on the zero lash are generous and it may be tempting to let one go a few thousandths under but don't do it. Mark Todd, DAL FO, has been fighting roughness on his Continental powered L-5 for months and finally pulled the cylinders and found all six push rods on one side were too long by just a few thou. He also had burned exhaust valves on that side. He got the rods the right length and it purrs like a kitten now.

I'll be down int the next week or so. I'll call to see when to find you at the airport. Hurry and get her fixed!

Bruce

[mod cessna]

Guys keep track of where the push rod comes from so when it comes to re assembly they do not have to check the valve clearance. If they do check the clearance then everything should be ok. This is assuming nothing changed.
Here is the problem.
1. You may have some oversize push rods mixed in with the batch.
2. If you have your cylinders overhauled along with cam/lifter wear your clearances are all going to be completely different anyways.

Sooooo.... Check for deflated lifter valve to stem clearance of .030 to .110. Adjust push rod length as required.

[4-Shipp]

I recently replaced an exhaust valve in number four. Putting things back together revealed that one push rod was now too long. I tried swapping side to side and things got better but still not within limits. Fortunately a friend was dong a top on an 0-200 and allowed me to take a short push rod from his collection. He had a vernier caliper that was long enough to measure the push rods to the thousandth. This mad the job sooooo much quicker. It took less than 2 minutes to sort through his 8 push rods and eliminate the ones that were longer than the one to be replaced. I don't know where he got his tool but I would check Harbor Freight or other tool shop. It did not appear to be a high dollar tool and would save a great deal of time over the trial and error method. I'll find one - new or borrow his - before I have to tackle this job again.

Bruce

[Bruce Fenstermacher]

According to my parts manual pushrods only come .030 over sized. If you are changing anything in the valve train you should check the zero lash. Some things that I can think of that will change the zero lash are changing a valve and or seat or having these reground so a new or even overhauled cylinder would count. Of course overhauling the tappets will change the gap but you would only do this on a major or at least have to split the case to do so.

Changing the rocker arms will change the gap. When I rebuilt my engine I swapped around the rocker arms to get the best uniform fit for all my valves. If you do this swap only the intakes with intakes and exhaust with exhaust. My parts manual has different numbers for each and I know there is a difference at least in the older rocker arms. I don't recall for sure but think newer rockers are interchangeable. The difference was one rocker lacked an oil hole that the other had.

[GAHorn]

... The difference was one rocker lacked an oil hole that the other had.

Yep. The exhaust rocker must have a lubrication squirter-hole. The intake can be either way.

[mit]

How is everyone bleeding them down? Making sure they are flat.

[Brad Brady]

How is everyone bleeding them down? Making sure they are flat.

Tim,
You could tell all the lifters that they are ugly and that there mothers hate them......That should depress them!...Another way is what I call dry pumping the lifters.....bring them to where they are opening the valve and repeatedly pumping them until the oil is out of the fouler.....this method is marginal.... the best way is to remove the lifter from the fouler...with a 470 type of tube this isn't a problem but with a stock 145 or 300 push rod tube....you need to pull the cylinder. All of this is academic....if the fowlers havn't been ground you shouldn't have over sized push rods....But I always keep the tappet,push rod and the rocker arm together......But that's just because I'm that anal......Brad

[HA]

ya know Tim that's a good question. Like Brad says it's easy with other engines (Lycs, big TCMs) because it's easier to pull the pushrod tobe and get to the darn things. then you can just stick a length of safety wire in there and depress the check ball and push it together. but on the O300 if you don't want to pull the cylinder then you've got to deal with the lifter way down in there....and if you do manage to pull it out this type can be reassembled cocked slightly which will lead to breakage and mental anguish.

so the way Brad described (as his non-preferred method) is how it's usually going to happen, just excersize the thing a bunch and assume you got it eventually. the tolerance is big enough that that's probably going to work just fine anyway

[mod cessna]

HA-

....and if you do manage to pull it out this type can be reassembled cocked slightly which will lead to breakage and mental anguish.

Are you referring to the push rod socket becoming cocked in the tappet body? Yes that is a problem. If the socket does become cocked in the tappet body it will shatter the tappet body if the crankshaft is rotated. This usually happens when mechanics are swapping push rods. When a push rod is removed it can pull the push rod socket out with it. It does not come all the way out, it becomes cocked, the crankshaft is rotated, the socket smashes against the push rod housing flange, and boom your cylinder project just became a tear down.
Only the old tappet bodies really have this problem. The new tappets have a grove where a clip is installed to prevent the cup from coming out of the tappet. Although I have seen the tappet bodies, with the clip grove, with no clips.