Mag stacks

[raspy2point2]

Does anybody know what the size of 911S mag stack for MFI is in MM or how do I know when I look at one. Sometimes when your confronted with a mag stack by itself its hard to say that It is a 911E or S. Also I have ordered a set of 2.8 RSR Mahle high compressipn P&C. any thoughts of going with the orignal factory approach ( 92X70.4 ) or a 2.6 short stroke (92X66). The car will always be a norrow body with 7'S in the back and a max of 215 X 60 or 225 X 55 in that area. Main question is--will I have too much engine with a standard 2.8 to use on a narrow body car or will the 2.6 SS fit the bill better? When I look at pictures of factory 2.8 RSR's they always have big tires and heavy flared fenders. I do not want to be on the edge all the time around corners about to break loose at any second because I have too much power. Thanks Chris R- Gruppe#144 / Early S Reg.

[Eric911S]

Hello: You can never have too much engine. I have built early 911 narrow bodied cars with 3.0 engines that have alot of power. Saying that I would do the short stroke engine. You will have less overall power but the quick reving engines are great for fun street driving. You may also consider doing a 90mm bore with the 66mm crank. This will cost you less to build and they run great as well. I'm going to build a 93mm bore with the 66mm crank to give you a 2.7 short stroke since I already have the parts. If you do go the 2.8 route then I would suggest using the early aluminum case bored to suit the 92mm cylinders. I would suggest you make up a quote sheet to see what it will cost you and also so you can start collecting the parts. Good luck with your project. Oh almost forgot about the stacks. I'll get you the part numbers. You can also bore the stacks out to fit your engine. Thanks Eric

[RTincher]

Raspy:

I went through the same quest a little while ago. The specs for all year stacks are on this thread.

http://www.early911sregistry.org/for...ead.php?t=7669

For the plastic stacks, the 312R # indicates S stacks, but I don't know if that's true for mag stacks. EricS will.

Matt Blast at Eurometrix is also a great resource on things MFI - he talked me through several alternatives, and rebuilt my throttle bodies and re-cad plated my hardware to jewelry-quality finish.

[raspy2point2]

Yep I love to rev!!!!!! Thanks for the info guys --looks like I'll go for the 92X66 approach and have a car like my 2.2 911S but to the MAX with a 2.6SS ,twin Plug, High compression MFI. I am going to leave the 1970 2.2 911S alone and start with another car for this project. The 2.2S is a great 911 which sounds almost like a 917 at 6800 to 7300 rpm --love it. Regards Chris R-Gruppe #144/ Early S Reg.

[Eric911S]

Hello: Good engine you are going to build. Just keep in mind the 90mm pistons and cylinders will cost you half of what the 92mm ones will. I would find a aluminum engine case first and build up on that. You can put that in your S and still keep the original engine. Although if you are like me you need more than one early Porsche car for the fun factor. Lastly nothing sounds like a 917 at full song--- nothing! Thanks Eric

[kenikh]

Just keep in mind the 90mm pistons and cylinders will cost you half of what the 92mm ones will.

That's if you use Mahle parts. Also remember that using Mahle 90mm (RS) P/Cs on a short stroke crank will give you a CR of about 7.5:1; not good at all. You will have to invest in JE pistons to get this combo to work well. The really cool set up and why the 2.6SS is so neat is that a stock Mahle RSR 92mm kit on 2.7 heads with 66mm crank gets you around 10.5:1 CR; perfect for dual plugs.

I'd go with the short stroke 2.5 (90mm P/Cs) for cost and reliability reasons. I think that the margins on the spigots for 92s are too thin. It's not a matter of if it will fail, but when.

[Eric911S]

Hello: With all due respect to Kenik, the 92 and 93 mm pistons and cylinders work just fine. I've built some pretty stout 2.8 and 2.9 engines that pull hard to 8000rpm. The trick is the early aluminum engine case. The mag cases are way too soft and tend to work harden over time. That is why you have to put inserts in every stud hole and shuffle pin the case halves and they still leak oil. Mahle make some higher compression 90mm piston and cylinder sets that are 10.5 or so compression. You could also use some used Mahle 90mm cylinders and some 90mm J&E pistons or Ross pistons or Wiseco pistons or Cosworth whatever brand you like. I've used them all. Like I said look for that engine case first then decide what you want to build. Thanks Eric

[kenikh]

I'm with ya Eric; I wouldn't hesitate to build a 2.8 on an early aluminum case.

[raspy2point2]

Hi Eric--In your opinoin a 2.6SS be a little less stressful of an engine on an Mag case? I would like to retain the Mag case as I am weight savvy. 22lbs. is a consideration. I am a member of the Aluminum Lug Nut Assoc. I am buying the Mahle pistons for their quality and long life. But if you think a Mag case is going to come apart after 10,000 miles then I will consider a early Alum. case. I assume I can attach MFI to a 1967 case without too much trouble. Or is this case going to have to be carbs?

[Eric911S]

Hello: Mag cases are fine except you have to do all the theaded holes with inserts of some kind. The threads will pull out of the case for sure including the case half studs. It is just a money thing, you will spend more preparing a mag case then you will a aluminum one. The aluminum case you will just need to bore the cylinder holes for the larger cylinders and do an oil by pass mod if you want and still use the steel cylinder head studs. What you may want to consider is a 2.4 engine with 2.2 S pistons and twin plugged. These run great as well and you won't have to bore the case just need the long stroke crank. I've built a couple of these as well and they pull as strong as some of those 2.7 RS clone engines I've driven in. If you want to run MFI on a early aluminum case you will have to also weld on some mounts for the MFI pump, very easy to do. I know so many choices so little money. On the 22 lb weight it is good weight and you could always use lighter tires and race seats. That should save you at least 100 lbs. Also a carb setup weights less than an MFI setup, just another thought for ya. Good luck and take your time. Thanks Eric