924Board.org

[Dutch924-racer]

I have bought an Webcam camshaft.

Duration: 257/257
Duration @ 0.050: 233
Valve lift: .517/.517

I have an adjustable cam gear with it which I can turn 4 degrees to the right or left.

What degree should I put in on ?
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937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

[Rasta Monsta]

Did you deck you head? If not, set it on zero until you are ready to dyno tune it.
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[924RACR]

You might ask webcam what they'd recommend...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[endwrench]

I think it will be personal preferance and driving style. Advancing the cam should give you better top end and retarding it should improve the bottem end.

Todd
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'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....

[Dutch924-racer]

Advancing is turning the gear to te left ? (standing in fron of the car).

And do you mean with top end, more power in high rev ?
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

[endwrench]

Advancing the cam would mean turning the cam to the right in relation to the gear. If you turn the gear to the right this would probably retard the cam if your gear is built like mine or most I have seen. Just think of it as turning the actual camshaft in relation to the belt.

In theory, if you advance the cam, and you pick up power, it will be at the upper end of the rpm range but there is usually a corresponding loss of power in the lower rpm range.

Todd
_________________
'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....

[Lizard]

hmm, I have been trying to find confirmation on this factoid Todd,

though from everything I have found, retarding the cam gives more top end (I would start with 2º retard), and advancing the cam gives more bottom end.
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3 928s,

[Lizard]

to retard the cam turn the gear CW on the Camshaft,
To advance it turn the gear CCW on the camshaft.
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3 928s,

[Dutch924-racer]

I want more power @ low rev. Zo turn it to the right (CW) ?
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

[RC]

The generally accepted consensus is that advancing the CAM (in relation to the crank) MAY allow some "improvement" in the lower (<4K) range while retarding the CAM possibly increases power in the upper RPM range. Note that this is more relevant to stock cams. Aftermarket or "performance" grinds will have various degrees of duration, overlap and lobe separation, as determined by their manufacturers. and may not follow this generalization.

The way most adjustable gears are made and marked (mine included) may confuse the issue somewhat. Ensure that you are advancing or retarding the CAM in relation to the crankshaft and not the outer sprocket.

Other factors to consider that will affect valve timing are the proximity of the cam to the crank, the belt length, and the valve lash. If the head or block has been machined the cam will retard as will a stretched used belt. Within reason, reduced valve lash may theoretically improve the top end while increasing it can improve bottom end power.

Any results achieved by altering cam timing will depend on the individual camshaft in addition to intake, exhaust and head flow and design. The results will be difficult to quantify, even on a dyno, and vary with your driving style, track, gearing and expectations.

My own experience with altering cam timing has confirmed that the "optimum" individual position is more a case of trial and error following the general rule. With one fairly "hot" cam I found that whatever I did would only lose top end power without gaining anything much less than 5K. The stock cam appeared to be best (IMO) at about 2° retard on a decked block and head and so was actually 4°. My current cam which is essentially stock plus a few degrees but on an increased lobe centreline, performs brilliantly at the O position.

Considering the manufacturing tolerances, wear and effective belt length the only way to assess the accuracy of the timing is with a degree wheel and dial gauge. Failing that would just suggest starting at O position, do a few timed laps and then try + and - 4° and do some more laps and see if you can measure or feel any difference. Found that 2° is difficult to compare but 4° will make a difference. Basically it comes down to experimentation and you may even end up with different preferences for short or long tracks, depending on your level of competition and driving style.

And remember to reset your ignition timing after every cam change.

Roger

[Dutch924-racer]

A bit confusing with al different answers.

Standing in front of the car the engines turns clockwise, so I asume:

- advancing it wil be turning the gear to the left (CCW) - more power @ low rev ?

- retard it wil be turning the gear to the right (CW) - more power @ high rev ?

I asume the best way is to set the cam on TDC and the turn the gear ?

Correct ?

My gear looks like this one, can be adjusted -4 to +4


_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

[bass gt]

Ok,

If you turn the crank clockwise, with the cam gear loose, you are retarding the cam.
Turn the crank counterclockwise and you are advancing the cam.
however, be very careful, and do not advance/retard too much. And hand crank the engine several times before using the starter motor, just to be sure.
And having tried this, the changes are very small, but measurable.


Steve
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Front Wheel Drive is the Devil's work.

[endwrench]

Uuug! Not sure which orifice I had my head in when I gave you my answer but please disregard it . Obviously, when you consider the whole theory of the thing, RC is entirely correct. Also, bass GT's explanation of turning the crank is the easiest to follow. Sorry for steering you wrong.

Todd
_________________
'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....

[Martijnus]

quick question.
Next week I'm adjusting my cam gear in the same way, what bolts did you use? M5?

edit: hmmm guess that's not yours on the pic

never mind...
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"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

[Dutch924-racer]

The cam gear is from a VW I don't know wich model.

This weekend I adjusted the gear.

Is turned the camshaft 4 degreeds to the right. This should be advancing it.

I will test it next trackday 1 march.
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller