Possible issues with Euro Spec P/C's in US

[mohmedh]

Currently going through an engine rebuild and after going through many posts and a call with Don at EBS led me to buying the 9.8:1 95MM (930 103 983 03).

Was advised if I wanted to go stock Mahle 95mm P/C's, I was limited to the Euro compression spec as Mahle was no longer making the others. This was also confirmed when trying to order directly from my local Porsche dealer.

My questions - These P/C's will be going on my near stock 3.0L SC build, and when reading through forums, I am now worried about issues relating to fuel not being as good in the US and working well with this compression. Is there anything I can do during the rebuild to help with this?

Also - Is it worth going up to the 964 cams? This will be a street car, and I would rather have more on the lower end. I have read you lose this with the 964 cams, but is it really that noticeable?

[Flat6pac]

Have Don make up a set of JEs for you at 9.5, have the cylinders replated or if cylinders are good
just use slip in JE pistons
Go to the high side of cam settings with JE upward of 1.8 that you can’t do with Mahle pistons.
Better low end response.
Bruce

[mohmedh]

Hey Bruce,

I plan on keeping the original cylinders and getting the JEs like you mentioned for a future build I have planned. Appreciate that advice though as I was about to give my original cylinders away to be used as display pieces.

However, For this current engine rebuild, it will be the 95mm Mahle set I described above

[Glenfield]

Who’s doing your build or are you handling that yourself?

The issue you’ve been warned about is detonation. Can happen on 9.8:1 with our crap fuel and hot temps in the summer. In reality, those P&Cs are unlikely to measure out at 9.8:1. To be sure, you can have your builder check before assembly and tell you actual compression. If 9.8:1 you have options incl. upping gaskets, although probably not preferred.

964 or 2021 cams will reduce effective compression further so you should be OK. Do you have a small port or big port motor? In my research 2021 was a better cam than 964 (set to max advance for a small port motor bc they don’t breath beyond 5700 anyway). Others will now wax lyrical about M1 cam sold by ICarp or William Knight or Perfect Power in Chicago.

If you’re buying new P&Cs, seriously consider 98s. I rebuilt my motor stock with 2021s. Wish I didn’t. PM me and I can give you more details.

[mohmedh]

I am doing my build at an independent Porsche shop out in Woodstock, IL. I have yet to get advice from my engine guy, this is just all based on my own research and would like to go back to him with as much info and being as knowledgeable as possible. Also everything at the moment is at Ollie's and have been told they are starting to work on it as initial inspection of stuff was completed roughly 3 weeks ago. So this would be the time to make these decisions and get things machined out if necessary.

Do you recommend at-least moving away from the stock SC cams? What did you end up doing in yours and did you lose out a bit on the low end? Being a street car, and a city car at that I would like more low end than top end.

I did just purchase the new P&Cs from Don, I told him I may change my mind so he has given me a month to decide if I want to keep the 95's or go up to 98's. If I do go up to 98, is there anything I would need done to the case or heads to make it more compatible? It is an 80SC, I'm going to guess it has the smaller ports, but I can ask and find out for sure.

I sent you a PM, would love to talk more about this and get your advice, especially since you are local to Chicago.

[Glenfield]

If keeping it stock or stock plus, i would do cams. Look into the 964 v 2021 v M1 and call a guy called John Dougherty.

I probably would do 98 jugs. Interchangeable but different gasket setup in think. Or no gasket. Engine builder will know.

If you have an 80sc, believe you have a small port motor. Check engine engine stamp. 930/16 is small port US and Canada. You’d get major returns from porting and flowing the heads. Chat to John Dougherty about it relative to cam choice and where you want torque.

If you’d change out CIS it opens up a bunch of additional decisions but if not, you should:
- use arp rod bolts
- steel or Supertec/raceware/etc head studs
- auto associate rod bearings and get the good Porsche main bearings (have to research this)
- have your bottom end balanced to a gram by Ollie ** and pistons etc
- check intermediate shaft gears, chain and sprockets

[mohmedh]

You're still running the stock P/C's with original US Spec compression, but with updated 2021 cams? What exactly is the difference from the stock sc cams that you notice and are not liking?

I am looking into the 98mm Jugs, my only concern is that would be an even higher compression that the euro spec 95mm no? So I would run into the same kinds of concerns?

I have asked about porting and flowing the heads, this seems like a good idea. I plan on sticking with the CIS for now.

[Glenfield]

I saw your DM and will give you a ring but good to keep this on public boards for posterity and most importantly, the input of the real gurus.

Yes, small port motor with 9.3:1 compression and 2021 cams set to full advance. The small port motor is very torquey bc of the port velocity. It won’t rev above high 5s in stock guise. So I timed the cam to increase the torque in the mid range vs higher ranges, where the engine would be out of breath anyway. It definitely helped add area under the curve but doesn’t solve the fundamental issue with small port motors - it’s a narrow power band with a low rev ceiling. I would definitely spend good money porting and flowing the heads to earlier SC spec (39mm). That will help the car breath and pair very nicely with more compression and cam. That’s my big regret.

There’s a set of P&Cs for sale in the classified. Buy those and send them straight to millenium. Other ideas would be to buy a set of Nickies (if they have more piston options for 98 or 95mm jugs). Also, Henry Schmidt sells 97mm jugs at 9.5:1 that would go really well with nieces heads and a better cam.

[shoooo32]

I've built a big port 3.2ss with 964 cams and a small port 3.0 with M1 cams. Both have plenty of torque for city driving (I set them to 1.4mm advance) but the M1 idles so much smoother. The 964 is choppy and doesn't sound stock. I've already put 50k miles on the 3.2ss, and when I get to 100k I'll toss in the M1 cams. Highly recommend. I'm localish to you Chicago folks (Milwaukee) if you want to check them out.

[mohmedh]

What other things have you done on the small port 3.0 with M1 cams build? Also what compression are you running?

Would love to see it, and get more info on what things worked and what you wish you changed, if there is any on that build

[faapgar]

After your valve job the CR will be less than 9.5 so you will be fine.Ciao