UpFixenDerPorsche

Thanks Greg.

Somewhere I've seen an article mentioning titanium lifters, plus other bits like titanium keepers and collets. Think they may have mentioned Ti valves too.

They did calculations that showed the reduction in timing belt tension (and therefore HP recovered) by the use of lightweight reciprocating pieces.

Seriously tempting, but alas, the cost was measured in cubic dollars.

Strosek Ultra

Speedtalk about DLC coated lifters. Simard´s cams were made of steel - right?
Åke
http://speedtalk.com/forum/viewtopic.php?f=1&t=33940

Strosek Ultra

Solid 35mm DLC coated lifters at a favorable price.
Åke
http://techtonicstuning.com/main/ind...oducts_id=1932

GregBBRD

Correct on the steel cams.

Read that thread. As usual, on the Internet, a lot of people stating "what they have heard" and very few actual people with experience......

The Internet creates experts from idiots, with the push of the "post" button....amazing stuff!

Probably the only person there with firsthand experience had been doing it for many years.

GregBBRD

Adding titanium retainers and keepers when using a stock lifter is one of those absurd procedures that people get conned into. The percentage of weight change is virtually zero.

BC

However, as stated, Nissan figured it out with cast cams. Nissan is one OEM that has done well, relatively, with coatings to really get the most out of the engines.

ptuomov

There was no confusion. I asked about DLC on lifters sliding against cast-iron camshafts. It's a difficult application to get right without problems. Steel sliding against DLC is lot easier to get right.

Everyone is free to ridicule others for the sources of their information, but I think there's value in reading the published research papers on the topic. I am not my sister who's got a Ph.D. in material physics, but I do have enough experience reading research papers that I can get information out of them. Not enough to make a call on what coating to use where, but enough information to have an intelligent conversation with someone who works on DLC applications. As of today, my informaiton from maybe five years ago is of course now dated. It's possible that the coatings have improved and/or that the experts now better understand exactly how and where to apply them.

My view on cams, in case anyone cares, is that Simard's steel cams with Mike Jones profiles, modified hydraulic lifters with reduced travel length, steel beehive springs set to load profiles that match the camshaft profiles and the valvetrain mass, and potentially DLC coatings on the lifters is the current gold standard of mechanical camshaft systems for 928s. Getting the valve events right for the application is, however, much, much more important than getting the state of the art mechanical combination. The state of the art mechanical combination will just allow one to reliably run a little more aggressive (i.e., higher acceleration) profiles and to maybe reduce friction losses compared to the standard mechanical combination. I'd want to know exactly what I'll get for the increased peak accelerations (or if these increased limits are even used) before paying say $5000 more for the gold standard mechanical combination. Just my opinion.

Strosek Ultra

If the lobes need welding it will cost some money. Thought if the wear is limited regrinding which cost far less would be sufficient. Regrinding will make the base circle diameter of the lobes somewhat smaller. It is also a question of how far deep the hardening of the lobes goes.
Åke

UpFixenDerPorsche

+1

GregBBRD

People's shock of what it costs to accomplish improved quality and improved performance pieces is almost always humorous.

This forum is about the most expensive street car made in the the 1980s and 1990s. The Honda Civic forum is located somewhere else.....

Back a few years, when brand new GT cams were still available (some of them still are available), a stock set of cams, new lifters, and springs was over $7500, from Porsche.

I bought and used many sets of these cams....using different springs and different lifters, with the cost still being north of $6000.

In comparision, the "gold standard" cost of making very custom pieces with the best reliability possible is an unbelievable bargain.

Just my opinion.

mark kibort

so funny... I know.. but the bmw guys NEED to use them or their springs fly off the valves ... sometimes the end of the valve breaks off too. dont hear that much of that going on in porsche land!

HP savings??? man, what a joke... almost as funny as the guy that drops 2 lbs a wheel and thinks he saves a second a lap.....*(until you see the data. )

mark kibort

thats not good news, as no one wants to risk this mod with a gear that can break a fixed tooth! Ill have to go back to my notes.. it was a canadian industrial cam and sprocket company that had some secret way to fix this stuff, but wouldnt say how. Ill have to check . i thought mine was sheding teeth due to the one tensioner that was jammed and loose, but the other side lost just as many teeth.... remember, i lost a few that were not adacent, and then when they became neighbors.... I pulled the cams and used modified elgin 85 cams for the S4 heads.

terry gt

why mess with old cams with worn lobes and sprockets , sure you can get them reground , if there is still material left . Get a new set of Colins cams like I did , I put my good set of GT cams on a shelf.

ptuomov

Do you have photos?

Depending on how much and what kind wear they have, it may be possible to simply regrind them to the original spec (or to some other spec). Since the base circle diameter will be reduced, you should probably measure how deep the valve sits in the valve seat and then run lash caps if necessary. If the regrinding will take you past the hardened part of the camshaft surface, then the cams can be nitrided to harden them again (I believe this will give you harder and more durable cams than the factory stock cams, by the way.) While you're at it, you may want to have them grind a slightly different profile if you want more high rpm power, but that is entirely dependent on the rest of the engine and your preferences. Then pair those with the VW hydraulic lifters that Roger sells and you're in my opinion good to go.

In my opinion, reground cams that are nitrided combined with the new, lighter VW hydraulic lifters will match or exceed the reliability of the factory stock GT camshaft system, provided that the lobe is either the GT lobe or some other competently designed lobe with similar aggressiveness.

Strosek Ultra

Here's what Supertech said:

"I am not sure if can be DLC coated, but a cast cam with a welded hard face like stellite, does not need DLC because these already have a good coefficient of friction and is compatible with most cam followers.