New vs Servicable Camshaft

Guys,

Anyone an engine guru?

I popped open my IO540 C4B5 and found I bought a pretty good motor, but have a small amount of pitting on the cam lobes. I plan to replace the cam shaft and doing the research to buy a new one found two options. New for ~$1000 or Serviceable and tagged ~$600.

I would ask the mechanic who is helping me disassemble but he has the FAA in his shop this week for an ag service inspection and I don't want to bug him anymore.

I am at that the point in the build were everything seems to hit me for more then I expected panel, engine, seats, interior and would love to save $400 but also don't want to "regret it" later.

Thanks

Four hamburger runs for a new cam. I would not hesitate at all.
Cams cause so much grief and are so hard to get to.... cracking the case and more.
Get the new one, you will be way ahead.

Drippy said:

Guys,

Anyone an engine guru?

I popped open my IO540 C4B5 and found I bought a pretty good motor, but have a small amount of pitting on the cam lobes. I plan to replace the cam shaft and doing the research to buy a new one found two options. New for ~$1000 or Serviceable and tagged ~$600.

I would ask the mechanic who is helping me disassemble but he has the FAA in his shop this week for an ag service inspection and I don't want to bug him anymore.

I am at that the point in the build were everything seems to hit me for more then I expected panel, engine, seats, interior and would love to save $400 but also don't want to "regret it" later.

Thanks

Click to expand...

One expert's opinion, passed along by a non-expert...

A while back, I asked Mahlon Russell (the board's resident engine guy) an open ended question about an engine core I was looking at and what he would do if he purchased that core. The core came with a bunch of yellow tagged parts, including a cam and followers from one of the reputable shops which specialize in re-machining internal parts. He recommended selling the yellow tagged cam and followers and buying a "cam kit" which includes a new cam, new followers, new hydraulic units, and a few more bits and pieces.

Cam's&Tappet's

flightlogic said:

Four hamburger runs for a new cam. I would not hesitate at all.
Cams cause so much grief and are so hard to get to.... cracking the case and more.
Get the new one, you will be way ahead.

Click to expand...

Yes, I agree......and No,there is more to the story.Failure rates are about 50/50 between new and proven,don't forget tappets will need to be tagged or replaced also.Have you sent your parts in for inspection?We can always override the inspector and install new.Only FAA approved shops get to make the Tag call.IMHO
RHill

Thanks

Guys easy sell I will go new thanks

Tappets

I had the tappets visually inspected by the machine shop, only 28hrs on them since new and they felt it was OK to reuse them. Should I be worried?

Mike

CAM AND LIFTERS

What is the point of going with a new cam if you use the used lifters.

The cam and lifter kit will run about 2300.00. If you figure the difference in cost on the lifters and hyd units you will be closer to 900.00 total difference.

That being said the kits come with the Hyperbolic lifters and some people have had oil pressure issues when using them. The straight lifters are available but not in the kits. I imaging the parts would be close to the same cost if priced separate.

Jesse

Only go with a serviceable one if it meets new limits. You can be sold a servicable cam or crank that is within FAA required limits, but a few hundred hours down the road the wear could actually take it below the minimum limits. This means a replacement if your engine has to be torn down, ie due to a prop strike or something.

togaflyer said:

Only go with a serviceable one if it meets new limits. You can be sold a servicable cam or crank that is within FAA required limits, but a few hundred hours down the road the wear could actually take it below the minimum limits. This means a replacement if your engine has to be torn down, ie due to a prop strike or something.

Click to expand...

Many an RV project ran into issues buying a "rebuilt engine" for a few thousand less from an air boat shop. Two quintessential expressions come from the rebuilding industry. 1) Paint it black and send it back! 2) Paint it gray and send it away! Not funny if you have been burnt buy any of this.Try not to learn the hard way the difference between may or may not meet the bottom of service limits (one of these engines had "not air worthy" scribed on the ideal gears and the engine data plate installed). And A new limits engine from a reputable builder.

Tappets

Thanks everyone for the inputs. I am still a bit confused about the Tappet issue.

Prior to my purchasing the motor it had gone through OH and was returned to 0 time status. The aircraft had a fire in the wheel well and the engine saw some heat at 28hrs. Working with an A&P I opened the motor up and we found quite a bit of surface gunk, evidence of water, but the only pitting was on the cam shaft lobes. I have cleaned most of the parts in the shop and sent the crank out to a shop to be polished.

I purchased a new cam shaft - thanks for the good advice.

But I did mess up and don't know which tappet assemble was in which slot or for which cylinder. I did keep the tappet assembles together (same plunger, push rod socket, body). I also had a machinist inspect the surface of the tappet body and they appeared new with no wear or pitting.

I will have them dimensionally inspected if you think I should????

QUESTION - Can I recover from confusing which tappet goes in which cylinder or do I need to buy new Tappet Assemblies?

Thanks sorry for the long question and drama.

One reason for the tappet matching is to match the wear-in of the cam lobes. That aspect will be moot with a new camshaft. The only potential issue with resurfaced tappets (followers) is the hardness vs depth of the remaining material. If they are really heat treated through hardened, then the depth of hard material is greater.

If done right, the original depth is known, the material removal limit is known and some pieces have been tested for hardness (QC).

This technical aspect may be why some would desire to replace tappets along with the cam.

Did the pitting occur from high surface contact pressures, or corrosion in an earlier life?

Tappets

Bill,

I believe the pitting occurred while the engine sat post getting wet. I come to this conclusion based on the location of the pitting, not on every lobe and discovered under a film of gunk. Some lobes were less gunked up and didn't show pitting.

While I have an educated ear - can you confirm the matching that is intended to be maintained is between the tappet body and the cam lobe and doesn't apply to the hydraulic tappet plunder and push rod socket ect? Is that correct?

If I buy replacement parts do I buy just the body or the whole assembly?

Drippy said:

Bill,

I believe the pitting occurred while the engine sat post getting wet. I come to this conclusion based on the location of the pitting, not on every lobe and discovered under a film of gunk. Some lobes were less gunked up and didn't show pitting.

While I have an educated ear - can you confirm the matching that is intended to be maintained is between the tappet body and the cam lobe and doesn't apply to the hydraulic tappet plunder and push rod socket ect? Is that correct?

If I buy replacement parts do I buy just the body or the whole assembly?

Click to expand...

I am not one to answer the specifics for the lycoming engines. Some of the engine builders out here should do that. They know what the book says, as well as what works best. It usually takes a couple of days for them to see and answer. A weekend is a good time.

I asked about the pitting as if it were from contact, then, personally, would look carefully for tappet damage. As it is, again, an experienced builder (with multiple builds) should give advice.

bodys

I would replace the bodys only if the hyd units were new or overhauled last go around. The key part is the contact between the lifter bodys and the cam.

Jesse

Tappets

Jesse,

Not sure I understood - again sorry up front.

You would only replace the units if they were new?? Do you mean if they were new at the last OH you wouldn't replace?

bodys

I would replace the bodys no matter what! I would only reuse the inside pieces if they were new or overhauled 28 hours ago when the engine was overhauled.

Jesse

Not to add confusion to the matter. All these parts are stone ground.When you send lifters in,there are thrown in a pile.When time permits,they are cleaned,inspected and there faces reground,then put in matched sets,tagged and put on a shelf,waiting for an order.The tappets you send in are not the ones you get back.The quality of the work depends on how often the operator dresses the stone.Once stone hits steal the cutting face starts to change so the more often there dressed the better the result. I understand the pitting came from a sitting motor that was involved in a fire that was put out chemically lased water and not from wear. I also have cleaned gray lead laced oil residue as thick as taffy out of these engines,so as I see this,I wouldn't mix and match.Replace all with new.Send everything in for tagging, I would think the cam & lifters can be reground and sold on ebay to recoup some of the cost.