Looking For a Cam Doctor - in the North East

[jamesjedi]

Hi,

Anyone know of a reputable shop that has a "Cam Doctor" in the North East or Canada?

I need to confirm my cams. I have disassembled the cam box and looked at the marking and the stamps, but I still need to identify it as I do not have a cam card.

Thanks

James

[Tippy]

Just post the ID alphanumeric here.

There's not a lot of cam vendors for 911's. Should be easy to ID.

[jamesjedi]

Thanks for the reply.

I did post the numbers in another thread. Will put them here as well: 964 105 246 071 21.

There is a 3 or an M hand engraved on the end of each cam.
Nothing is stamped on the ends.

[faverymi]

I think Tom1394 in CT may have one.

You can PM him and confirm

[jamesjedi]

Thanks. I will contact him. I cant find anyone closer to the NE.

[racing97]

The problem with most cam reading equipment is that it usually is set up for translating measurement (straight up straight down) and the Porsche is CORA (cam on rocker arm) so to get the actual values the engine sees it needs to be measured on the valve retainer. Therefore the owner of said equipment is going to need to set up a head, cam tower, and rocker assembly. If it is important to you to have realistic timing figures that is what is required if not the other method can give you the L/C's and peak lift.
regards

[jamesjedi]

Thanks for the replies.

I am confused - I thought the cam doctor did more than just the up and down.

Where can I send this mystery can if the Cam Doctor will not work.

If I degreed the cam on the engine, could that provide enough information?

[racing97]

The cam doctor does do more than up and down we can't use all the information it can give you. It is the method used for actually taking the measurement with the type of rocker the porsche uses vs. the standard Domestic push rod system. If the operator is not willing to tool up for it you will only get numbers for the Lobe centers which may or may not suit your purposes.
Yes if you degree the cam on the engine that will give you a much better result.
regards

[Neil Harvey]

all good info here to consider. I posted this on another thread a few days ago.

911 Rocker arms are quick acting, so if the assembler tries to measure the cam timing with some valve lash and its off by half of one thousands, (0.0005") which is easy to do, they will get inaccurate cam timing numbers.

The easiest and most accurate way is to set the valve lash at zero and them measure the opening and closing crank angles at 0.012" valve lift (the hot lash point). Measuring it at 0.004"/1.0mm cold lash would also give you big durations that would be confusing.

Add in rocker arm geometry often modified by re grinding the rocker faces in a quick repair just to get a good surface will change the cam timing at the valve by large amount also. This often changes the rocker ratio which has a change in lift at the valve.

If you check the cams on a doctor or similar, these results can be compared to other cam profiles measured the same. This may help identify them. Most cams out there have the same lobe profiles and slightly different LSA's. Most of the offerings by the known cam suppliers in the Porsche aftermarket, are copies of older well know designs. Cut and paste cam designing is rampant in the business, so expect to see a lobe design the same as many of the more common designs.

[blockhed]

why not send it to a pro like camgrinder or rothsport or etc

[jamesjedi]

Thank you for the replies.

Blockhed - I would not think that they have the machine to measure an unknown cam. They certainly could use a degree wheel - as could I. However, I could be wrong.

Neil Harvey and Racing97, what would you do? I could assemble the rest of the motor and use a degree wheel, but would that give me my timing specs?

Or, do I have a Cam Doctor measure it and then compare profiles? As mentioned, it will not be an uknown profile.

[racing97]

I have figures for a stock 964 and a 993rs If you had you cams somehow reground and you remember what application you were looking for it would help. If no cam grinder placed markings it possible that it is stock. Those cams have very wide lobe centers and it would be hard to grind it very far off from the original angels. You can ascertain the lift with a caliper by subtracting the high side or the parabola from the ramp area (this is an approximation) and multiplying it by the rocker ratio 1.45 which is roughly the average, now you have the lift and we can work out the opening or top timing from there.
regards

[Neil Harvey]

We have measured the 911 valve motions long ago. so measuring just the cam on its own is all that is required.

Measuring on the engine can be done, but expect a large measure of error to be included. As racing 97 suggests, the 911 rocker ratio is known. The 911 rocker ratio by design is 1.47 but with wear, repair and other factors, it can be as he suggests, an average of 1.45.

You can measure the net lift of the cam in the engine, or remove any lash and measure the gross lift and subtract the lash. If you wish to measure the duration, you need to decide were the point of measuring starts. Most Porsche cams are designed (if properly) with lift numbers starting with 0.012" lift as this is the hot lash point designed into the cam lobe design. Durations are typically measured either as seat or at 0.050".

I'm not exactly sure what you are after? Is it just the settings to use? There is not one setting as many factors play into cam timing. I would do the following.

Dry assemble the engine without pistons. Fit 2 heads on one side of the engine along with the cam housing, camshaft and two rockers. Use a degree wheel and set TDC accurately. Use a wire pointer or similar to set the TDC on the degree wheel.Use some light test springs to make it easy to turn. Example use cyl 1. Zero out any valve lash and with a degree wheel fitted, select any number on the degree wheel as starting point. Note the number. Set up an indicator on the exhaust retainer or at the top of the adjuster. Now open the valves by turning the cam. As soon as the indictor reaches its highest point, record the number on the degree wheel. Stop there and move the indictor to the Intake valve. Then continue to turn the engine until that valve reaches its full lift. Record that number on the degree wheel. These difference between these two numbers will give to the lobe separation between the Exhaust lobe and the Intake lobe. If you want, you can repeat this and measure the open and closing of each valve and record the numbers on the degree wheel. Just expect some error here.

At least if you know the LSA, you can then decide where to set the camshaft to start. If its wide, 108° +, you know the cam is for high engine speed performance. Most late model 911 air cooled cams (964) had LSA numbers upwards of 113°.

Remember, to check the Piston to valve clearance at any position you choose. Low lift, narrow duration cams will typically run low LSA numbers as the head flow numbers are small. As the head flow numbers increase, so does the lift, duration and LSA numbers. This is the "off the hip" evaluation you can expect. There are exceptions though.

If you have any questions, email me and I will help. Use the contact info on our web site, PerformanceDevelopments.com.

nh

[tom1394racing]

You could try my method.

DIY Cam Doctor

PM me for details

[jamesjedi]

Thanks for all the replies. I would love to do the DIY methods described, however my heads are getting rebuilt.

I am going to get it measured with a Doctor and then compare results. I will post them here. Hopefully this process will aid anyone else with a mystery cam.

I cant say thanks enough for the effort that the replies have required.

[stownsen914]

Maybe call some of the Porsche race shops in the Northeast and see if they can recommend a race shop or machine shop that has a cam doctor? Dawes or Dan Jacobs are a couple that come to mind. Or if you're going to have to ship your cams anyway, just send to camgrinder from this forum, or Webcam or Elgin (probably all on the west coast as you probably already know).

I measured my cams as I was building my engine using a dial indicator and a degree wheel. Mostly I was curious (and younger and more enthusiastic!) Not a big deal since I was assembling my engine anyway, but might be a pain just to measure them. One thing I discovered was that the grinder had ground different lobe centers on my right and left cams!

Scott

[racing97]