US 16V Cam Advance/Retard for Max Output

[Fixer]

Some people in racing that their build motors (and do not have the luxury of having a dyno on hand) have been very successful advanced or retarded their cams a few degrees carefully to dial in maximum power output.

I recently read about American 16V V8 motor builders doing this with great results.

I have a 450CC 4 stroke Yamaha racing Quad and retarding the cam 1 tooth makes a very noticeable power increase.

All the serious racer on this particular machine do this as soon as they get the chance.

Anyway first being sure that there is no piston to valve interference.
they do what you'd expect, setting #1 piston at TDC and using the starter to crank the motor, they move the cam maybe a degree or two at a time in each direction while checking cylinder pressure.

Once you determine which direction higher cylinder pressures are observed,
go in that direction a degree at a time until the pressure begins to drop and then back it off a degree. This would maximize engine power.

I was curious if any US 16V owners have tried to dial in their cams for maximum output as many in racing have done with much success.

Not advocating, I'd be very cautious to try this. But I was curious what the
much more experienced 928 Motor Heads around here thought.

[Danglerb]

Not really, the 16v requires the use of offset keys to tweak the timing +- 2 or 4 degrees, which means you remove the cam gear, change the key, set overall timing, see how you like it.

Stock cams are FAR from a racing cam, so not much playing with timing does as there is effectively no overlap. 16v brains, the Ljets don't have tuning ability, only the 85+ brains. (84 doesn't have eproms in sockets, so first a socket needs to be installed etc., maybe other issues).

[Fixer]

Greg Brown mentioned how well the 16V US cars respond to advancement or the distributor. I am curious about advancing the stock cams a few just to see.
I think to have my cams reground to Euro spec or better is was quoted @ $1200 (WebCam)

I am keeping with the concept of what Porsche could have offered in '83 (RS Project)
subtle performance increase along with weight reduction. This is why i wanted to advance the stock US spec cam.

Mike i wish we lived closer to one another, you'd be amazed how much quicker these US 16V cars are when less 700 pounds.

Already plenty quick enough for me.

[XLR8928]

Originally Posted by The Fixer

Greg Brown mentioned how well the 16V US cars respond to advancement or the distributor. I am curious about advancing the stock cams a few just to see.
I think to have my cams reground to Euro spec or better is was quoted @ $1200 (WebCam)

I am keeping with the concept of what Porsche could have offered in '83 (RS Project)
subtle performance increase along with weight reduction. This is why i wanted to advance the stock US spec cam.

Mike i wish we lived closer to one another, you'd be amazed how much quicker these US 16V cars are when less 700 pounds.

Already plenty quick enough for me.

I have found that the European ignition timing setting (effectively 8deg btdc) is good for more power and costs 0$. This setting however, will fail your smog check. So if you do advance, retard before test. Also, I'm running the euro cams, in my 4.7, and they do add some umph at higher rpm.
BTW- Smog check NR in my area

[Danglerb]

I think you will find the HP you gain advancing a stock cam isn't worth the price you pay in loss of torque in the low end.

Enough is real hard to predict. I like having two cars, mostly stock US, and a more modified Euro, and find both of them fun to drive. Euro is going to lose some wt, but I have a more modest target around 2900 or so, that easy first 300 or so lbs.

BTW What Porsche would do or have done, is whatever was permitted in the racing classification they wanted to win.

[Opelotus]

What about '78/'79 cams? I have a set in my garage and I think they have more overlap than the stock cams in my '84. I can take a picture if necessary. Would those cams make a difference?

[Fixer]

Originally Posted by XLR8928

I have found that the European ignition timing setting (effectively 8deg btdc) is good for more power and costs 0$. This setting however, will fail your smog check. So if you do advance, retard before test. Also, I'm running the euro cams, in my 4.7, and they do add some umph at higher rpm.
BTW- Smog check NR in my area

Good advice, no smog here in Pennsyltucky either. Yes i remember you installed Euro cams, were they the actual? or did you have a set made up to spec?

Originally Posted by Danglerb

I think you will find the HP you gain advancing a stock cam isn't worth the price you pay in loss of torque in the low end.

Enough is real hard to predict. I like having two cars, mostly stock US, and a more modified Euro, and find both of them fun to drive. Euro is going to lose some wt, but I have a more modest target around 2900 or so, that easy first 300 or so lbs.

BTW What Porsche would do or have done, is whatever was permitted in the racing classification they wanted to win.

Agreed, Mike you probably don't remember but i was dumbfounded how it could be possible to get these cars below 2900 lbs. You said it could be done and you were right. The electric adjust seats alone are 25 lbs heavier (each) than a manual seat.

Enough for me means that if driving the car flat out (or 9/10ths as said) through turns.. i'm sure i'd end up in a ditch. It's plenty fast as-is. But none of us here can help but want more.

Originally Posted by Opelotus

What about '78/'79 cams? I have a set in my garage and I think they have more overlap than the stock cams in my '84. I can take a picture if necessary. Would those cams make a difference?

Yes they add 10HP IIRC. Use them.

I just want this car done. More painting to do, engine, suspension, exhaust. PITA.
Have no time to work on it with real paying work to do.
I backed it out and drove it a bit, turns out the tires only had 27 lbs in them all around since i did the power assist steering delete.

Put 34 lbs up front or 2 lbs less than recommended, and the steering is terrifically light even at slow speeds. The car is really fun.

Looking at buying a 80 gal 2 phase compressor to do the rest of the paintwork.

[XLR8928]

My cams are authentic euro grind
-Kerry

[Opelotus]

Originally Posted by The Fixer

Yes they add 10HP IIRC. Use them.

Cool! I will have to clean them up in preparation for replacing the head gaskets, they are a little rusty in a few spots.

[Niles]

Matt, I just noticed your drilled key. Now that's funny. How much weight did you save?

Pearls Before Swine:

[XLR8928]

Originally Posted by Niles

Matt, I just noticed your drilled key. Now that's funny. How much weight did you save?

Pearls Before Swine:

I've figured out a way to drop 45lbs without so much as removing anything, (and my wife is even going to help)... I Hate diets!

[Fixer]

Originally Posted by Niles

Matt, I just noticed your drilled key. Now that's funny. How much weight did you save?

Pearls Before Swine:

Niles,

It's a nod to the 917 key along with the shift knob i made from lightweight wood
and the gulf blue paint with orange accents.
Porsche guys will pick up on that.

BTW even the keys for our cars are heavy. But your right more of a statement than anything. A lot of material came out of that key.
I have a spare key but the drilled key i really happen to like. It feels great for some reason.
Also lightened the gas cap which i found heavy. It needs painting in a high quality orange urethane enamel.
Notice the little plastic spring cover on fuel door is also gone. Little stuff adds up i'm learning.

I didn't drop over 700 lbs being lazy.
(not me the car)