RolexNJ

Well said Travis, bravo!

evil 944t

If you eliminate the bad harmonics from the stock cam by swapping it to a quality after market cam, you will eliminate a lot of the problems. Not to mention staying within the factory rpm range if your not upgrading anything else.

2bridges

New springs with new cam is not "smoke and mirrors"
Unless you otherwise verify actual spring rates throught lift, check for bind (especially with higher lift/perforamnce camshafts)

Nothing to do with porsche vs non-porche is simple basic engine building good sense.
Check everything, if somthing is changing (cam profile for example) check it twice.
Only a fool would invest in new cam/lifters/ head work without at least having stockes ones checked extra close.

Also as mentioned in previous post - increased spring rates are needed the more lift and RPM you have. Valvle float is butal and actually "bounces" slack in the valvletrain, can even cause collision with piston, bad deal all around

Porschefile

Hehe, I've been learning a lot about metallurgy lately. It's a neat but vast topic. I just hate to see someone drop $1-2k in valves and retainers when they could save 50% or more of their money going with cheaper stuff that will work just as well.

I'm curious to hear some more real world experience (and not speculation) as to what our valvetrain's can actually sustain. I've heard so many conflicting things that I really don't know at this point. It doesn't seem to me that 7k rpm should be out of the question. I've heard comments from Milledge that the stock water pump should be safe to ~7.5-8k rpm but that the stock oil pump becomes an issue much past ~6.8k rpm. I commonly hear ~6.7-6.8k rpm being the safe and reliable max, though I'm not sure if that's conservative. Also, a race sustained 7k would be a bit different than the occasional spirited run on the street at 7k. I would think that stiffer valve springs would be good enough to support ~7k rpm. Does anyone else have some actual results as to whether this is plausbile or not? If I remember correctly, I thought ST actually revved his 2.5l out to ~7400rpm on one of his dyno runs. It seems to me that the biggest limiting factor in supporting higher rpm is the stock oil pump. It's too bad we don't have any (AFAIK) aftermarket upgrade oil pump available to us. It would be sweet if we did though, $3-5k for a dry sump to solve the problem just isn't plausible for most people. I wonder how much it would cost to have one CNC'd?! j/k

Dave, what bad harmonics are present with the stock cam? Odd ramp up angles or something like that?

evil 944t

Lol, I actually tried to design and build a pump to replace our factory pump. I worked with a dry sump pump builder and it was turning into a major project.

Plus, there are dry sump systems out there and for the people that need to spin up to 7k+ rpms, they can afford it.

I have to dis agree with one of your points. Wether you track at 7k rpm or take it to 7k on a spirited drive, you need to have the same parts in your motor. Other wise you risking failure.

You can modify you head with aftermarket valves/springs etc.. and keep you hydraulic lifters. If you mod the lifters, you can get them up to 7100rpm(track use). I haven't seen heard or personally gone any higher with out going to solids.

Porschefile

Sorry to get OT but, what is the real limitation with the stock pump? It's not that I can't afford it, it's just that to have to go to so much trouble and expense just to rev to say ~7.5k rpm is kind of lame. I'm not building a track car, just something fun for the street or the occasional DE/Time Trial.

special tool

Its a gerotor locked on at 1:1

evil 944t

Everyone, sorry for the OT. I don't have any data on the upper limits of the pump.
Because you like high rpms,lol. I can tell you there is a 8900rpm 16v sleeved 2.1car running around here. Its dry sumped though.

Porschefile

Hehe. That sounds right up my alley.

Thanks for the info ST.

RolexNJ

Wow, that is just plain nuts Dave, Damn!

Tom M'Guinn

I can understand arguing that different cam profiles may require different spring rates. No argument there. I can also understand that higher rpms may require valvetrain changes. No argument there either.

But, this notion that you need stiffer springs to run more than 16psi boost is dubious to me. I've never seen a logical argument supporting that notion, and it is inconsistent with our collective experience.

TRP951

when you say mod the lifters is this just going solid or can you actually mod the stock lifters?

RolexNJ

I am pretty sure that Dave means to replace the stock ones with solid ones. Meaning, doing a full conversion. I did this with my old 3.0L with Lindsey.

RKD in OKC

OK dad gum it, I am problably speaking out of turn here but this is what happened.

When LR was building up Rolex's 3.0 liter it was eating lifters. Brand new Factory lifters. AND it was eating them durning break-in, ie. under 5000rpm and 15psi boost. After a lot of florensic work and industry research they found ALL new 944 Turbo Hydraulic lifters were now manufactured by INA and only INA, even those purchased directly from Porsche. Rockwell hardness testing showed the INA lifters were softer than the original factory lifters. LR contacted INA directly and tried to get lifters that match the original factory lifters, but still got softer examples.

As part of trying to find why the lifters were being hammered LR had the 944 Turbo valve train computer modeled. The cam company that did the modeling is very experienced. One of their findings with the model was that the factory valve train would float at above 16 psi boost. This florensic computer model was the same one used to design the valve train setup for the LR solid lifter, cam, and springs and to make recommendatons for valve springs based on target maximum boost.

How do I know this...At the time I was running 18psi and doing dyno runs tuning for my glory run of 401 rwhp at 21psi. Heard some lifter tick and found 3 failed lifters. One of them was a brand new INA lifter installed only 10K ago. The solids were not in production yet so I got 3 of the original low miles lifters out of Rolex's car since he had the prototype the solids. Since then I have not run my car over 16psi. i am also putting my 2.8L together with valve springs for a target of 18psi.

Markus951

Well

in my last engine I did 6700 rpm and 28 psi of boost and I did not break anything. After changing to webcam I changed valve springs as well. New springs (FACTORY OEM) had much stronger seat pressure compare the ones in the car. I did change them myself when the head was still on the car. You could feel the difference in used and new OEM spring.. I say if you go with webcam go with stock but new springs. If you are going to purchase anything frm JME then by the spings with hes spec..they are not expencive.

I do not know how good are the spirngs on stock 16 valve engines.. As they are from NA car in stock I can quess that the seat pressure is not that storng compaire to turbocars, but that is also related to the lighter valve train what 16 valve engines have.. So If you are not planning to rev it up to 7500 rpm I quess its worth to try them out. If you see on the dyno plot that you are loosing power on higher rpm then I would change the valve springs first as a signal that valves are not closing property in higher rpm..

Markus