Help choosing camshafts for 944S ITB build

[adonay]

Stock 2.5l 16v engine with New seals\bearings and crank scraper -Fresh head with new guides and seats\ nothing out of the ordinary .
Danst Engineering 50mm itbs
Motorsports electronics me221 ecu with wasted spark ignition.

Now that ECU is on order i am planning the next step in this project and that is to see how good the stock 944s head can breath with some more aggressive cams .
Plan is to run the car in June and tune the current engine setup. Then add improvements in the winter
Low rpm drivability or low end torque is not the priority with this build. This will be a high strung fun engine .

I do not want regrinds but do want 2 exhaust style cams for a dual camgear setup. I may eventually upgrade the head with 968 intake valves and push rpms together with a drysump system.

How far can i go with hydraulic lifters in terms of rpm ?
Were is the valve lift limit on stock tappets and valve springs?
Cams i am looking at are 292-280º - 40/72 66/34

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[Bergerac]

From memory Cat Cams recommend solid lifters and upgraded springs after you go past 12mm lift but double check on their website. If it was for me I'd look at their dual pulley setup if I was going all out on a big cams

[adonay]

Nice thank you for this info will try to Get in touch with catcams. Solid lifters on the 944 16v platform is interesting and not really well documented. Wish I had 1 additional 944s head maybe I should look for that first.

Also I have seen or told by somebody that depending on valvespring height/retainers etc the springs may interfere with the cam house body. Hopefully the clearance modification is easy .

[adonay]

Have done some research today and believe i have figured out what i need and all that it involves.
Think i understand how these cams and lifters are shimmed by putting the correct thickness lashcap on top of the valve stem and putting a feeler gauge in between . I will be using a 3rd party supplier in Sweden .

Not sure going for the "biggest" cam is the best move probably wont even idle well bellow 1200rpm However it will be interesting and i am almost dead sold on going this route

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[Bergerac]

Are you planning to run the stock pistons and compression ratio? Valve to piston clearance may be an issue with this much lift especially if you go to the 39mm 968 valves.

Id be reading very carefully what @michaelmount123 has written here and on the old forum and maybe even engaging him to build me a head if he's still doing it.

[michaelmount123]

The hydraulic lifters will go to 7500rpm with the proper cams. Solid lifters will go 8000+. Setting the lash with lash caps is time consuming, but necessary if you want the extra revs. If you're considering going to 968 intake valves, be sure to configure your pistons for them now. That way they will accommodate the bigger valves if you ultimately go there. Oh, you'll likely need to provide relief in the cylinder head for the bigger cam lobes. Just sit your new cams in the head and spin them to see if there's contact at the top of the lifter bores. If you go with the solid lifters, you can block off the oil feeds in the lifter bores with very small pipe plugs. They're only there to feed the hydraulic lifters.
Good luck,
MM

[michaelmount123]

One more thing: The dual cam sprockets are pretty slick, but the intake side won't clear the hood. You'll have to put a bubble in it for clearance. Be sure to plan for this.
MM

[adonay]

The hydraulic lifters will go to 7500rpm with the proper cams. Solid lifters will go 8000+. Setting the lash with lash caps is time consuming, but necessary if you want the extra revs. If you're considering going to 968 intake valves, be sure to configure your pistons for them now. That way they will accommodate the bigger valves if you ultimately go there. Oh, you'll likely need to provide relief in the cylinder head for the bigger cam lobes. Just sit your new cams in the head and spin them to see if there's contact at the top of the lifter bores. If you go with the solid lifters, you can block off the oil feeds in the lifter bores with very small pipe plugs. They're only there to feed the hydraulic lifters.
Good luck,
MM

I do not currently have a head with the 968 intake valves and will not have one any time soon. Also would like to check the full potential the stock 944s setup has to offer. Flycut 40 year old pistons does no sound like a good idea to me.
I think I should source a second 16valve head and set up a mock-up engine to experiment on before I install the cam system to my main engine.

Is it possible to drill and tap then mount z screws with loctite into the lifter oil-feed?
Also can I buy thick lash caps and just machine them to correct thickness or do I need to purchase a bunch of different sizes.

If I were to install a dry sump pan and lower the engine as much as possible will the intake gear still hit the hood? A cosmetic bulge above the engine is not really an issue to me regardless.

Appreciate the feedback not much shared information about this modification online

[michaelmount123]

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

[cp99]

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?