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milnersXcoupe's Avatar
 
Join Date: Dec 2007
Posts: 20
Question Pre magnesium engines

I'd like to build a 66mm or 70.4mm stroke 911 engine for Turbo
so I'm thinking the pre Magnesium engine case motor is the way to go.

Which year / model case is strongest ?

What would be the largest bore Nikasil barrels available without weakening
the case structure I could go with ?

Will later model heads interchange for better breathing ?

Which later EFi manifolds fit these earlier engines ?


Thanks in Advance !

Last edited by milnersXcoupe; 12-12-2007 at 08:30 PM..
Old 12-12-2007, 08:21 PM
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Not sure if the mag case would be strong enough for boost. The head studs may pull out. The mag 915 trannies certainly wouldn't be strong enough either.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

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Old 12-13-2007, 08:34 AM
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I agree - the 'Magnesium' cases are out.

The 'Pre Magnesium' 1966 - 67 cases are Aluminum - the 2.0 , maybe the 2.2 and 2.4 ?

- which is the info. I'm seeking :

What year / displacement are the last of the First Aluminum engine cases -
prior to Porsche going Magnesium ?

From really bad Google reference info. - the use of Magnesium started with
the 2.4 , something you had to 'presume' as the articles referred to
carry over engine cases that used carry over cooling to create the 2.7 Magnesium case engine - being presumably - the 2.4 .

Were all 2.4 engine cases Magnesium ?
Old 12-13-2007, 10:57 AM
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Are you trying to stay within a specific racing class by using a small bore turbo engine?

If not, why not use a 3.0 or later engine? Or better yet a 930 engine?
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Old 12-13-2007, 12:48 PM
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No class - street.

66mm or 70mm stroke / 90 to 94mm bore.
Old 12-13-2007, 01:37 PM
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You might get a better response from the 911 forum. Not many people here would have the engines you are talking about.

I gather you just want a short stroke, big bore engine though? Sounds cool
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 12-13-2007, 01:48 PM
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I know that in many engine families we go short stroke for more rpm. BUT there aren't too many Porsche engines made from the factory that spin any higher than a 3.6 GT3RS engine. With regard for the Porsche engines, its seems quality rods and valve train determine rpm more so than stroke/crank or engine size.

I'm pretty certain that you can install newer heads on a smaller bore space block, BUT it will require a lot of work ie welding and drilling if I'm correct. I'd think some ported E heads or S heads would easily flow more than enough under boost. S/ RSR spec heads aren't short on flow and would outflow some CIS heads anyway. Off boost port flow could be miserably slow without compression or camshaft. I'm sure CMW could make you some killer heads to your spec's....but you might have a power curve like french curve towards redline with nothing below 4000rpm.

Larger bores are of course going to help unshroud valves, but yet cause more flame front issues. I'd think Nickies would be able to maximize bore and maintain strength. At this point, you'll probably want to entertain the dual plug thing for a big bore high rpm engine under boost. If you go down to a 2.4-2.8 engine and then drop compression to 7-7.5:1 you've better get the gear ratio down for off boost torque deficit. I'd think you'd break a 7:31 so maybe a 8:31 with short stack gears.

Jmho...great project for track. Street, by the time you get compression down and rpm up your going to have a pig off boost. Your going to need to look for a nice little GT turbo for spool and I'd seriously consider the SSI route the Brian and Ben have put together for a torque throttle repsonsive turbo. Most aftermarket turbo headers will be BIG. Most KKK options that are improved will be BIG. Custom cam is probably easily doable. There has been many 2.x turbos ran on the track, just not sure of "streetability". I don't know your experience so nothing personal. These two valve hemi air cooled dinosaurs don't do well with high boost levels and therefore you can't make up displacement with psi like many 4 valve water pumpers. As you surely know a low boost 3.6 will walk all over this on the street. Not only due to engine/torque curve, but tranny options and little to NO weight benefit with a boxster of a 2.0 to a 4.2 liter. Small block ford weighs about 450lbs and a big block weighs like 720lbs. There might be a 40lb difference between a big and small block Al boxster engine.

I just feel your maximizing the short comings of Porsches own 3.0. Unlike so many engines, head temp is your limiting factor and you just can't cheat that. Interesting project and I wish all the best. I'm sure I sound like a dark cloud...just devil's advocate. In the right chassis and properly geared this could be a real screamer. Cheers
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Old 12-13-2007, 03:28 PM
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By the numbers you give I could tell that you are trying to rev the piss out of this motor you are looking to build- I dont have much advice on the crank shaft accept that porsche built a 2.1 liter motor for some class back in the 70's. That and if you are going to reve that high you are going to need the 906 or 901 rockers- stock 930 rockers are not much good past 7,500.
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Old 12-13-2007, 03:44 PM
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I would be concerned with the stregth and age of the engine case.

There is at least one member here on the board with a 2.4L turbocharged engine. A search might turn something up.
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Old 12-13-2007, 04:18 PM
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