pjburges

Hi all,

Some of you might have noticed some of my other threads about solid lifters in a 944 16-valve motor. Well I've done it, with .003-.004" lash for intake and .006-.008 on the exhaust.

I'm having timing challenges and am curious how to interpret the Factory Service Manual when it adresses cam timing. It says: 1mm stroke, zero play and then lists:

Inlet opens -> 4 degrees (CS?) after TDC
Inlet closes -> 40 degrees CS after BDC
Exhaust opens -> 36 degrees CS before BDC
Exhaust closes -> 4 degrees CS before TDC

What does 1mm stroke zero play mean exactly? and what does "CS" mean? Am I to use my degree wheel and a dial indicator on the lifter and measure 1mm of stroke on the lifter and verify that the crank is 4 degrees after TDC , or is the point at which the lifter and lobe contact and start to move occur 4 degrees after TDC? Hope my question makes sense! I'm no cam expert so this is stumping me a bit.

Ideas? Thanks all!

Tom M'Guinn

My guess would be CS means crankshaft degrees (i.e., not cam rotation degrees), and the 1mm stroke, zero play, might mean the specs are lists at the point when the valve has opened 1mm with zero valve lash. Most cam specs are listed at a specific point of lift, since the exact point it starts to open is difficult to pinpoint. Could be wrong, but that would be my guess...

pjburges

I think your guess is right on Tom - thanks for the help!

So from the above numbers we can calculate that the duration of the intake cam is 216 degrees and the exhaust cam -> 212 degrees.

Am I correct in assuming that taking the duration and dividing by two gives me my lobe centerline angle (LCA)??? If so, thats 108 degrees for the intake and 106 degrees for the exhaust.

Zero play still seems vague - is this a hydraulic lifter totally pumped up - or totally squashed out, or perhaps they just mean no lash between the lifter and cam?

Here's my predicament - I now have about 13 degrees of extra duration in the intake cam (haven't measured exhaust yet) from using the solid lifters - don't know how it happened but I'm confident in my measurements. I don't think I can reliably assume that my 4 degrees CS will yield the factory's 4 degrees CS rotation at the 1mm lift amount because hydraulic lifters squash out, and my solids don't at all not to mention the fixed .003" lash in the solids.

Can I time the engine by setting it to the same Lobe Centerline Angle (LCA) as the factory hydraulic setup as listed in the FSM? So if set my LCA to 108 degrees too - is that basically the same thing except I get a little extra duration?

Sorry for the wordy post - just trying to be thorough!!

Tom M'Guinn

How did you determine you have 13 extra degrees of duration?

pjburges

Ok, so after measuring over and over and over again the attached excel file shows how it turned out. What I told you earlier about my intake duration was wrong. The whole setup is very similar to the factory S2 camshafts. Intrestingly, it would appear the less the lash the more duration is developed. My 6-8 thousandths on the exhaust cam yielded #'s very similar to what Porsche achieved with the hydraulic lifters!

Feel free to use the file - or suggest alternate cam timing other than what I have it set at!!! I'd love to hear opinions - just keep in mind that I cannot change intake relative to exhaust - but I can move the whole system advanced about 2 more degrees or retarded about 6 or 7 degrees. This is a 2.5L S with an S2 intake.

Hope all this info is useful to someone out there with a DOHC head on their 944!!

pjburges

Ok - so here's what I settled on for timing and the predicted results from the measurements that I got from setting the cams there. Suprised nobody wants to suggest a valve timing! :P

I used Engine Analyzer Pro, which seems to be estimating very closely the power output of the engine considering it is purely theoretical calculation. Most importantly - none of the parameters are changed about the engine except for the cam timing of the stock hydraulic vs. the solids with my current lash and timing settings, so the change in the power curve is purely resultant from that. EAP also calculates that my current camshaft timing is 3.5 degrees retarded which I don't calculate, but hey perhaps its smarter than me! I have plenty of adjustment to move it.

gt37vgt

One of the reputable guys on here sujjested getting the lobe centers further apart for fat torque turbo.
I did have a little look at one of your other threads and didn't see much ..
i was just wondered why you have done this ?
the standard 16v valve chain is from a few accounts good for big rpm .
did you shed significant weight from the valve chain ?
I've gone for TI valves and retainers
and light weight VW hydralics i managed to drop the lot from about 180 down to 120 grams per valve with bigger valve heads ..
the exersize has cost me i guess $800 that includes setting my lathe up for R8 so i can turn down the valves .
but i will put in a heap of time on the lathe ..

did you use an off the self solid lifter ?
there are alot of cars with 35mm buckets

333pg333

This is n/a right?
Who supplied the cams and what do they say?

pjburges

They are the factory hydraulic cams and yes N/A. Porsche specifies a timing procedure that just flat out won't work when using solid lifters. So I've got a degree wheel with a dial indicator on the follower, measured duration, centerline, opening/closing event @ 1mm lift etc etc in order to time the cams according to the values in the FSM that I wrote earlier in the thread. I got as close as I could - but my durations are now different with solids so I had to compromise. Someday when I have a little cash I'll have a set of solid-lifter cams made special for the motor.(Or maybe I'll do it myself!haha)

Lifters are 35mm aftermarket solids made for an Audi - came with shims that go on top of the valvestem. I spent a TON of time on the lathe cutting those little bastards to fit! All in all I put about$400 in mine and alot of labor. I've reduced oiling demand to the head, I can feel the weight difference in my hand just comparing hydraulic vs. solid. Same cam chain - engine won't spin over 6800rpm anyways. I increased duration 6 degrees on the intake from having such a tight lash - .003-.004 thou and this has changed my predicted powerband quite a bit all other things held constant.

I did it because nobody else has yet!!

Chris White

Geez, I was out having some fun skiing this weekend and you guys finally post some interesting 16v stuff?!

It looks like you figured it out with my help anyway, the factory method is a pain and I don’t like it of even setting up the hydraulic cams. I use a similar lobe center method. If you use a good crank wheel and some dial indicators its not too bad. I use the midpoint of the cam opening as the measuring point since the rate of change is at the greatest (most accurate measurement) and mark the point on the degree wheel where the opening and closing ramps cross that lift.

Your spreadsheet looks quite a bit like the one I made up to do the same thing….!

BTW – it you really want to go with solid lifters (this is a little late for your project!) the other way is to get longer valves (assuming that you are going to better strength alloy – just about mandatory if tis a turbo) and then there are other stock solid lifters that can be used.

pjburges

I used a cheap Jegs degree wheel and some safety wire as an indicator attached to the altenator pulley. They were suprisingly consistent / accurate. A harbor freight dial indicator with half a washer bent and tack welded to the tip did the measurments on the #1 intake and exhaust lifter buckets. I made a little metal bar that bolted the dial indicator rigidly on a stand to the head.

All is done - buttoned up and putting it in the car next weekend. Timing was what the last table I posted is. Im hoping that the intake/exhaust cams will advance some when the tensioner is pressurized with oil and the valve stems heat up and reduce the lash on the exhaust... I'll snap some pictures of it going in!! Thanks for the help!

pjburges

Hey all,

THANKS FOR ALL THE INPUT ON CAMS SUPPLYING SPARE OIL PUMPS, PARTS ADVICE ETC!!!! I successfully got my first 944 motor that I rebuilt from scratch myself running. The only other motor I've ever rebuilt was a motorcycle engine and a 350 Chevy so I'm feeling pretty stoked!!!

It has solid lifter buckets with the factory hydraulic cams. Lash and timing are as mentioned earlier in the thread (made the lash caps myself on the lathe!) It also has a bored out N/A throttle body @ 60mm (again done myself on the lathe!) and an S2 intake plenum. No emissions controls except the oxygen sensor. Also has no balance shafts, power steering or A/C. I am probably going to do a cat delete to it since it is emissions exempt.

The throttle response is laggy, but once it "pulls vacuum" in the intake it revs quickly. It only pulls a steady 17psi of vacuum at idle. The part throttle fuel mixture doesnt seem rich enough soon enough, so the part throttle engine response could be alot better. WOT is the opposite (goes rich I think). Below is a AF ratio graph with me driving around logging with an Innovate LC-1. It pulls 1800-6500 RPM in second gear in 5.5 seconds according to the plot below. Thats pretty quick I think! The motor definitely comes "on cam" around 3500 RPM. Below that it is boggy but still very drivable. It needs a tune, but I don't know how to edit the values on the computer chip/ burn my own chips yet.

Here's the AF graph - do these fuel mixtures look pretty good??? This is a modifiend 2.5L 16V. Pulls are up through second and third gear. Upper line is 14.7:1, lower line is 10.58:1. The second gear pull and the shift to third and pull through third are visible at the beginning of the plot.