Questions re: valve springs, rods....

[TdiRacing]

I am new here on the forum, but have been starting to gather some of my parts to rebuild my 2.4L engine. I have a few questions so that I may source and find the correct parts for my plans. Been away from the Porsche scene for about 10 years, so please help me find the right parts.

What I had: 2.4L w/ 2.2S Pistons, Webers, 911E cams were installed. Had someone else assemble my engine last time and the sealant they used clogged my cam squirters and ate the cams. Engine has been apart for 5+ years now and I want to finally build it the way I want.

Plan: 2.4 w/ 2.2S pistons, S cams or 906 cams(have both), TMW Throttle bodies 40MM(have them), Electronic Fuel injection(need), Heads will have ports opened just a bit, case will be prepared will all the upgrades(shuffle pin, case savers, raceware studs, oil mod...)

Questions:

Want better valve springs to run the S or 906 cams I have. Not decided yet, but will likely use the S cams as it will not be an all out race engine.

Opinions on which cam and valve springs should go with them? I cannot remember where these cams max out? The range of pricing seems to be $270-up for the spring sets.

I know many people who have been running stock rods to 7500rpm without issues. I want to upgrade the rod bolts to ARP, but not sure If i should get "better" rods.

I guess this is dependent on the cam selection as well. As the higher the revs, the more likely an upgrade is necessary.

Opinions?

Last question for now: What is the gain from twin plugging the head? I can easily do this with my DFI ignition system, so the only added cost is the machine work. All the info I have is outdated and not applicable to the small 2.4 L engine.

Sorry for the long post.

[304065]

Where do you want to race this car? That determines how much money you need to spend to win.

For a street driven, occasional track car, I would use the S cams or even something a little more modern from Camgrinder, with stock valve springs. That allows you to keep the stock rods. There is a mod for the center bearing that is useful if you are going above 7500, but remember that the stock "s" had a safe limit of 7300 rpm.

Twinplug allows you to retard the timing for more ideal peak pressure point (PPP) and allows the engine to tolerate the reformulated panther pee sold to an unsuspecting public as "gasoline" without detonation. Above about 9,5:1 you want to consider this, it's highly recommended above that.

Remember that the more overlap the cam has (S have 97 degree lobe centers vs. 102 for E) the lower the dynamic compression, at least at low RPM. So bumping the compression usually helps, and there's a correlation to efficiency gain as compression increases.

So back to the beginning: decide first what you want to do with the engine, then build it for that purpose. Example: if you are racing, you need ALL the mods to the case and crank, 906 cams or the modern equivalent grind, LOTS of work to the heads to make them flow, the highest compression you can get (it's not unheard of to hear guys doing 13:1) and twin plug is a must, big oil pump, etc. IF all these mods are performed you can figure on 100-110bhp per liter with a 20 hour teardown interval.

On the other hand, if it's a street/occasional track engine you want, consider a different cam like the Supercup, twin plugs and 10,3:1 would be fine, do the case mods and the crank mods for insurance, and have a mild port done to the heads. From a 2,4 you should be able to realize at least what the factory achieved (190 DIN HP), most certainly more with modern parts and EFI.

Good luck!

[TdiRacing]

My goal to have it drivable on the street and get back to doing some PCA club racing/track days for fun. The goal is not an all out race engine.

What is this mod you are talking about for the High RPM's?(center bearing?) is that putting the groove in it?

I am leaning towards the S cams because I already have them and they seem to be more of what I would need for street driving.

I have a rebuilt set of stock rods reday to go, just need ARP bolts for them.

Compression will stay at the 9.6:1 so, based on what I have read, there is little return on the twin plug mod. Will see how much the machine work is and decide when I get there.

I am so curious to see the difference in performance with the TMW throttle bodies and PMO manifolds with the fuel injection. The carbs were such a pain. Always boiling fuel and locking the engine up, hard starts in winter....

Anyone here running a fuel injection system like this on a 2.4L engine? Would like some feed back on what systems work well on these engines.

[2.7RACER]

John Cramer,

"the reformulated panther pee sold to an unsuspecting public as "gasoline" without detonation"

Priceless!