Help choosing camshafts for 944S ITB build

[adonay]

Since you're asking about setting valve lash with solid lifters, I presume you're wanting to rev beyond 7500rpm. I caution you to consider the weaknesses in a stock lower end. The crankshaft can handle it, but stock Glyco rod bearings will not. Although the main bearings will be okay, you'll want to use ACL race rod bearings. Stock connecting rods are another issue. The big end will distort at very high RPM, and even the ACL bearings will struggle to survive. Proper race rods like Molnar or Pauter (or others) are the answer. You'll also want to consider the stock pistons which will be operating well beyond their designed stress limit. Dry sump will surely add a level of confidence with lubrication.

Doing a mock-up with a 4V head will show you a lot. The lifter oil holes can be tapped without drilling using an 8-32 tap. Then use short 8-32 set screws (not pipe plugs) installed with Loctite as you mentioned.

Machining thick lash caps is very difficult. Obviously the machine work will need to be precise, or you can avoid this by purchasing lash caps in the sizes that you need.

Lowering the engine is limited by the 944 cross member. I don't think you'll be able to get enough clearance for the intake pulley, but you can try. Modifying the crossmember may be the answer but your oil pan may get a little close to potential damage when running off the track.

I do hope I'm being helpful. I surely don't mean to be critical of your plans, but there are pitfalls you'll surely want to avoid. If you care ask more questions, please fire away.

Regards,
MM

Going Beyond 7500rpm is hard to say this all depends if the added lift can produce enough flow and power up top.
Like you Saied there are several issues over revving the 44 engine. I have some aftermarket Molnar rods in my garage and have few sets of ACL bearings also maybe i will install those regardless.

WP_20160628_18_26_32_Pro_zps9wevma64.jpg (210.69 KiB) Viewed 1138 times

@cp99 Do you intend to sell these if so do you have the camshaft specifications .

Lets just say that i will choose the most aggressive camshaft that i can still use with the hydraulic lifters and upgrade the Valve springs recommended to the same springs that i need for the Solid camshaft setup . This way it will be a modular upgrade that can be upgraded further in the future if needed. Figuered new valve springs should be purchased with any cam replacement regardless .
fitted load / length: 34kg @ 36.0mm: 39kg @ 35.0mm
max. load / lift: 110kg @ 14.0mm: 110kg @ 13.0mm

290°/283° - 249°/242° - 12.00mm/11.55mm - 3.15mm/2.65mm

Also Curious if i should throw in some VR6 lifters while at it 928 community seems to think they are a lightweight option.
https://928srus.com/products/050109309j

I can tune the car and dial in the powerband with these cams and see were i am at around 6500-6800rpm if the engine behaves well to the modification i may consider further developing the valvetrain and bottom end . If The stock head with stock Intake valves does not flow enough at higher Rpms i will keep it lower.

@michaelmount123
Your input here is most welcome and your experience and expertise on this subject is second to none in the porsche 944 community. Your old builds is what inspired me to try to modify the 16valve platform to begin with.

[cp99]

@adonay

Yes, I want to sell the camshafts because I won’t be using them. I bought them from Michael with the intention of building a monster 16v motor but life got in the way. They are brand new camshafts and the lobes were never ground, so you can grind them to the spec of your choice. Michael can opine if they’ll fit your build. If they do, I’m happy to sell them to you.

[adonay]

@adonay

Yes, I want to sell the camshafts because I won’t be using them. I bought them from Michael with the intention of building a monster 16v motor but life got in the way. They are brand new camshafts and the lobes were never ground, so you can grind them to the spec of your choice. Michael can opine if they’ll fit your build. If they do, I’m happy to sell them to you.

I am interested. Not sure I have anyone locally here that could transform the cam-blanks into something useful. Do you know the manufacturer and max lobe height?

I am having allot of fun with this 16v build and will probably transform the whole build into a turbo when I am done playing with the NA setup.
Ultimate goal is 180whp or close to stock turbo levels with no turbo.
Have to see the potential first and what sort of power levels are possible with the more or less stock 2.5l bottom end

[michaelmount123]

I don’t know if they’ll work in your application, but I have a set of the split cams with adjustable sprocket that I purchased from @michaelmount123 . They are brand new. What do you think Michael?

These billet cams are very high quality and would cost a fortune today. All of the journal surfaces are finished, and the lobes are rough machined and big enough to handle any cam lobe, i.e. any duration or lift. They were probably shipped with 19 tooth S2 sprockets, but I have 18 tooth 968 sprockets that can be fit with minor machining. I used them for both. The sprockets and cam halves bolt together and allow changing the cam centerline by altering the position of the sprockets. A camshaft grinder can finish the lobes to your specs.

[michaelmount123]

I'd definitely use the Molnar rods and the race rod bearings to increase durability. You'll also want to refinish your cylinder bores and use custom lightweight pistons at some point. Your cylinder head should be reconditioned and the ports configured by an expert (of which there are very few). This is to say, all aspects of your engine need to be in perfect shape to get maximum power and durability. The sequence of addressing different areas of your build is up to you, but you surely don't want to invite a catastrophic failure that will render any components useless.
Cheers,
MM

[michaelmount123]

Regarding lifters, never install a new cam with old lifters. The lifters will have worn in with another cam and will wear the new cam quickly. The VR6 lifters are a great replacement; cheap too.

[Bergerac]

I'm interested to see how this pans out, I almost went down this route before starting my 968 turbo build.