Cam tower restrictors - Good for break in?
 

Not that I'm at the point for the initial 20 minute break in run yet, but was reading Waynes break in procedures tonight and thought the following:

If the first 20 minutes at 2K RPM are when the rockers and cam form their wear pattern, then they will probably benefit from the greatest amount of oil possible at this curcial time.

I wanted to perform the cam tower restriction upgrade while I'm building the engine, but was thinking if the cams and rockers will benefit from more oil during this break in, is it better to keep the larger (original) cam line fittings and perform the upgrade at a later time when the cams/rockers are fully broken in?

I know, I've heard the stories of guys who've run thir engine w/ the valve covers off and have seen 'plenty of oil' and I'm sure if Porsche suggested this upgrade, its probably fine. Just curious if this is the right time to perform this upgrade.

Thoughts?

Porsche uses cam followers, not lifters. Therefore you can rest a little easier on the cam breakin. Just use a good moly or redline assembly lube and let er rip.

snow what I think he's refering to is the cam line adapters that have the 2.5mm hole instead of the normal 5mm hole. I think someone did a test and pulled the valve cover when the car was running and saw a ton of oil squirting over the cams. I"ve never rebuilt an engine so I dont' think I can help you with that specific question but I know it can't be too bad if porsche recommended it.

I've done this on my car and it gave me lots of extra pressure.

Tim,

That extra pressure is down low. Not that I don't trust Wayne's suggestion or Porsche's engineering wisdom, but any extra oil to the cam/rockers won't hurt. Its a 5 minute job to do the upgrade. I'll wait until the 500 mile valve adjustment.

I'm probably worrying for nothing, but it is my blood, sweat and tears;)

The old-style restrictors are no longer available from Porsche, if that says anything. They have been superceded to this new part.

I'm not 100% sure on this, but here's some food for thought. The larger hole in the plug means more volumetric oil flow, however, restricting it might actually increase the output oil pressure and spray. Like a garden hose? With nothing on the end, you get lower pressure, but higher flow. Place your thumb across the opening, and all of a sudden, you get a fast, large spray pattern.

I'm not sure if this analogy would apply in this particular case (seeing how the restrictors are upstream from the spray bar), but it's something to think about...

-Wayne

This restrictor thing got me all worked up as I first read about it in the preview of Wayne's book. As I had the motor apart anyway, I ordered the restrictors intending to put them in.
Then it occurred to me....there was next to no wear in the top-end of my motor, and oil pressure had always been max......so why change anything? I have the restrictors on the shelf for now.

would it be that the lines now have 2 "steps" up in pressure? You go from normal pressure to the cam line where the restrictor steps it up and then again at the nozzle?

Wayne,

That analogy makes sense. Also, the spray bar itself has holes much smaller than the 2.5mm restrictor. So if you think about the garden hose analogy, the amount of oil through the end of the hose (spray bar holes) wont vary much (but how much?) if the inlet is 2.5mm or 5mm even if the pressure is different at the inlet.

Again, I'm just curious and am a 'hard facts' kinda guy.

time to break out the fluid dynamics eqn's......;)

I don't know why Porsche put the restricters in. Did they state a reason? Two possibilities, one at idle, with higher pressure you get more coverage, like Waynes garden hose analogy, the other is at high rpm you just get to much oil on top, like a chevy, and not enough left for the rest of the engine.

What's the part number for these restrictors and who carries them?

thanks,

Mark:

The part number is 901 105 361 01.

The smaller holes create greater oil pressure behind them which is why the pressure stays up at idle. They also create more pressure to the crank and squirters.

Oil foaming was another concern as I recall, and it was reduced with the new fittings.

Pin holes in cam bar are so small as compared to the fittings, oil is going to be backed up in the bar with plenty of pressure to lube everything up.

My 2 cents

Thanks, Marc. I've ordered the parts from my local Porsche dealer & will install them soon.

regards,

I just got worked up on this because I'm approaching the part purchase point in the rebuild. I would say that since Porsche discontinued the large hole part they must have a good reason for it. Also I've heard Don Wise recently did a test on a 3.2 with the covers off trying to find out why new reground cams are going flat (not Camgrinder and not Elgin) he says there is just tons of oil flowing out on the spray holes I guess this also means the cam bearing are getting what they need. Also we hear about too much oil going to the sump/etc/etc. My thinking currently is....cam system gets enough oil...I hear of horror stories of bottom end possibly not getting enough oil esp. at high revs. A bottom line could be that fixing bottom end issues is more $ than top end. You can be fairly sure Porsche did tests of oil pressure and flow in the top end for various conditions including startup after rebuild and then made the change. I know, where I work, unless there is a clear strong case for a change there is a lot of resistance to doing it. If Wayne or others have updates on this please post.
Thanks,
-Henry

I would like to pose the following challenge for any hydraulics engineers out there. :) We know there are 6 spray holes per spray bar and 2 spray bars per engine bank. If we know the size of the spray holes, then the volume of the oil they can flow can be determined(pressure being constant). If the total flow capacity of the spray holes exceeds the total capacity of the restrictor orifice, then we got a problem. Number 3 and 6 heads will lose volume because they are furthest from the oil source(oil restrictor).
This does not take into account the oil volume to the heads is not only used for lubrication between moving parts, but it is also used as a coolant medium.(heat transfer)

The flow to ALL the spray holes will be decreased if the restrictor is to small. The reason is that the pressure is the same throuout the system that is beyond the restrictor. Pascal or someone, I forget came up with this.

The first point you made is exactly what I was getting at. The challenge is to determine is the restrictor "is to(o) small".

The second point, I disagree with. Your hypothesis is correct only in a closed system. Whether you measure pressure from 1" of the restrictor or 1 mile, the pressure is the same.
However, in our case, every opening beyond the restrictor results in a pressure drop because of the loss of fluid thru the opening, hence loss of pressure. Think of it in terms of a fire hose with holes in it. The more holes you have the more ineffective the fire hose becomes.

The second point is almost exactly correct. The holes are very small and in the case of the fire hose, it is turned off, meaning the only leakage is thru the small holes. In other words the hose itself isn't a restriction. To restate what you said , the pressure is the same everywhere beyond the restriction. The flow is determined by only two things, the pressure and the size of the hole. For the hose to have a significant drop in pressure it must also be a restriction. Of course there is almost always some slight restriction in the main line, but it is so small as to be meaningless.

An easy way to prove this to yourself is to buy a sprinkler hose, ie one with a lot of holes in it. As you adjust the restriction (the water valve) all of the hose has about the same amplitude water jets coming out from it, almost down to a dribble.

Extreemly long hoses and hoses with the end missing are special cases that would not apply to the engine as neither is true.

By the way one reason for cams going flat is not using proper assembly lube on the camshafts, another is reusing worn cam followers with a new cam. Cam followers should be reconditioned when installing new cams. But my guess is the improper assembly lube. You must use a good MOLLY lube or something like Redline Assembly lube for the cam to break in properly, The oil is to little to late and not good enough performance wise.

Im guessing the new restrictor has less area than the six spray holes, if the oil pressure increases at the crankcase when they are installed.
I like the idea of drilling the new style restrictor out to 3.5 or 4mm. I think the original is 6mm ? and the new one is 2.5mm?

I agree with Snowman, some moly lubes can dry up if an engine is built and not installed, or not started for a few months. I also believe the number one cause for cam failures when rebuilding an engine is using old rocker arms on new camshafts.

Porsche, and original owners, broke in all 3.6 motors with them.......

Jeff

That would be 12 spray holes: the restrictor feeds two spray bars(intake and exhaust) with 6 holes each.

Snowman,
I was thinking in terms of the hydrant being the restrictor and the hose being the spray bar.
Close the spray head of the hose and measure the pressure anywhere along the hose and you find the pressure is a constant. It's when you have leaks that exceed the flow capacity of the hydrant is when you run into problems....uneven flow across the spray bar(hose). Simple hydrodynamics.

In case you haven't noticed, I'm firmly against this retrofit. Most of us have modified our engines in one form or another. In any event, we are increasing the amount of heat being generated as a by-product of increased horsepower. These engines have only two means of melt-down prevention; oil and air cooling. Why reduce the reduce the capacity of one of the components to mask a problem on the bottom end?(crank and rods)