Turbo build questions

John I · 09-24-2014, 11:33 AM

Hello everyone. I would like to ask a few questions about a turbo engine build I have in mind.
I plan on building a twin turbo EFI Intercooled engine. This for my 79 930 with a G50 trans.
Right now the car has a 1995 3.6 993 engine.
I want to build an engine like I mentioned above. I already have the turbo set up, 3.2 intake, and Electromotive Tec 2.

(Questions)
Can I start with a 1978 SC engine long block?
I know it is an aluminum block.
I plan on using ARP head studs, or whatever is ideal.

Can I put a 3.2 crank and rods in this case?
I am looking for the extra stroke.
Are SC and Carrera rods the same?

Can I machine the SC case for 100mm cylinders?
I am a machinist and should be doing this.
But I want to ask before buying an SC engine to start with.

Are that Year SCs heads ok to use for this engine?
Valve size large enough?
I know I will have to machine them for the 100mm cylinders.

I want to build a 3.5 liter engine with good power, 400 plus HP
I know I am probably better off starting with a 3.2 Carrera engine, but I think I
Found an SC engine to start with.

I have now a 1977 3 liter 930 engine with SC cams.

If I am going to do this, I need to build an engine bigger than this 3 liter.
Here are a few pictures of the set up.

Thanks everyone for your help.
John

kenikh · 09-24-2014, 12:11 PM

Inline.

Quote:

Originally Posted by John I

Hello everyone. I would like to ask a few questions about a turbo engine build I have in mind.
I plan on building a twin turbo EFI Intercooled engine. This for my 79 930 with a G50 trans.
Right now the car has a 1995 3.6 993 engine.
I want to build an engine like I mentioned above. I already have the turbo set up, 3.2 intake, and Electromotive Tec 2.

(Questions)
Can I start with a 1978 SC engine long block? Yes
I know it is an aluminum block.
I plan on using ARP head studs, or whatever is ideal.

Can I put a 3.2 crank and rods in this case? Yes
I am looking for the extra stroke.
Are SC and Carrera rods the same? No

Can I machine the SC case for 100mm cylinders? Yes
I am a machinist and should be doing this.
But I want to ask before buying an SC engine to start with.

Are that Year SCs heads ok to use for this engine? Yes, but the alloy is different so the theoretical heat limit is a bit lower on SC heads than turbo heads. In practice, not a huge deal. Turbo heads also have sodium filled valves, SC do not. Again, in practice, not a huge deal
Valve size large enough? Yes
I know I will have to machine them for the 100mm cylinders.

I want to build a 3.5 liter engine with good power, 400 plus HP
I know I am probably better off starting with a 3.2 Carrera engine, but I think I
Found an SC engine to start with.

I have now a 1977 3 liter 930 engine with SC cams.

If I am going to do this, I need to build an engine bigger than this 3 liter.
Here are a few pictures of the set up.

Thanks everyone for your help.

The question I keep asking: Why not buy lower compression pistons for the 3.6 and turbo that? This configuration will meet ALL of your design criteria, with less hassle, less complexity and less expense.

John I · 09-24-2014, 12:22 PM

I understand what your are saying with lower compression on the 3.6, but I do not think the turbo exhaust manifolds you see here will bolt onto the 3.6 heads. Am I wrong?,
It seems a shame to take apart my 3.6 engine when it runs great already.
How much should I expect to pay for a good 3.2 crank and rods?
Thanks everybody.
John

kenikh · 09-24-2014, 12:30 PM

You just flip the flanges 180 degrees to use an early style exhaust on a 3.6. You won't be saving any money trying to go with an earlier motor - expect to spend $4K - $6K for a core 3L or 3.2L. $1500 for a crank and rods.

The best feature of your 3.6 is that it is known to run well. A pistons swap is EASY and you'll know the motor is good.

John I · 09-26-2014, 01:59 PM

Thanks for your advice. The info has been helpfull.
Is there any advantage to running the 3.0SC crank and rods over the 3.2Carrera crank and rods?
I guess even if the 3.0 crank is stronger, the 3.2 is not too weak.
There maybe an advantage if someone wants to build a short stroke reving machine, but turbocharged, it might not have that advantage.

I know it would be cheaper to convert my 3.6 engine, but I enjoy the behavior of my 993 High comoression N/A engine. I want to keep it that way in case I want to go back to it.
I have enough money not to worry about the cost of it. Plus this engine building is fun.

Thanks again
John

kenikh · 09-26-2014, 02:08 PM

Money as no object, I'd buy a 3 liter turbo motor, swap in a 66mm crankshaft, install GT3 titanium rods, open up the spigots to accommodate 102mm pistons and Nickies cylinders with mod-GT2 cams.

You'd get an 8500 RPM capable super-short-stroke 3,3L turbo monster unlike anything anyone else has.

If we are talking something less esoteric, I'd go with the 3.0L SC motor as a base, as the 3.2L rods are not the best Porsche made. Easily managed with aftermarket rods, of course.

911TT33 · 04:24 PM

John, why don't you just machine down the crown on those 993 pistons and fit on some 993TT heat exchangers (nice short primaries for maximum spool up) instead?

You can actually slip in 3.6 turbo pistons in the 993 cylinders

You'd be way ahead financially and also in terms of resulting HP if you used the 993 motor as the base. Those heads would flow very well too, and you'd have a proven EFI configuration to build upon too.

Up to you, but that's the direction I'd take.

John I · 09-26-2014, 06:52 PM

I am understanding that this 993 engine is a good engine to have, from what you guys are saying. Part of my concern in messing up a good thing. I like that engine the way it is.

I am now thinking of building this engine using the 3.0SC engine with its crank and rods, and going big bore as suggested above.

Big bore with shorter stroke does have some advantages with less piston side loading, and general stress. Maybe advantages too small to matter or make a difference. What do you think about that?

I have some heads here. I think they are 1987 930 heads. Can anyone look up these casting numbers?, and let me know what they are please. They might be better to use than 1978 SC heads.Thanks again for your advice and help.

ThanksJohn

getz · 09-27-2014, 12:18 AM

"I have now a 1977 3 liter 930 engine with SC cams. "

You could get 400 hp out of this.

JFairman · 09-27-2014, 12:56 PM

Those 930 heads look like they were made in November 1978 according to the 11-78 cast into them.
I don't think the casting number in the top left corner changed from year to year as long as they are 3.3 heads made for 97mm bore cylinders.

RR350 is the high temp alloy used in the 930 heads. I think the RR is for Rolls Royce because they made that alloy for the V12 P51 Merlin engines used in the P51 Mustang aircraft.

spuggy · 04:00 PM

Quote:

Originally Posted by JFairman

RR350 is the high temp alloy used in the 930 heads. I think the RR is for Rolls Royce because they made that alloy for the V12 P51 Merlin engines used in the P51 Mustang aircraft.

The "RR" in RR350 does indeed stand for Rolls Royce, although RR350 was used later in military turbojet engines like the GE YJ93 and GE4.

The Schnieder Trophy "R" motors and the Merlin developed from them used RR50 for the crankcase and RR59 for the pistons.

http://en.wikipedia.org/wiki/Hiduminium
http://en.wikipedia.org/wiki/Rolls-Royce_R
http://en.wikipedia.org/wiki/Rolls-Royce_Merlin

But the P51 used the Packard version:

http://en.wikipedia.org/wiki/Packard_V-1650

Personally, I think the OP should use the 993 motor if he knows he wants big power; twin-plugged, EFI, big ports and a knock sensor from the factory... It's a lot easier to start with that...

JFairman · 09-27-2014, 04:59 PM

Thanks for pointing that out. I'm just going on fragmented hearsay...
I looked at one of your links and found this picture of Rolls Royce Merlin engines being assembled in 1942.

spuggy · 09-29-2014, 08:09 AM

Quote:

Originally Posted by JFairman

Thanks for pointing that out. I'm just going on fragmented hearsay...

I dug up an application note or patent for RR350 few years ago for a post in this forum. Seem to recall suggested use was bearing support housings in jet motors, and plasticity of the alloy didn't occur until 1450, 1600 degrees, or something like that - or around 400 degrees more than the alloy for "regular" 911 cylinder heads.

Perhaps this was mainly for the race cars they homologated from the road cars - or maybe plain old over-engineering because they just didn't know and played it safe.

As noted, a lot of folks run N/A heads with forced induction and don't seem to see issues, even in some very high output applications.

Although I seem to recall Bill V saying that the 993 N/A used RR350 as well as a ceramic port lining. That was years ago, and I've never owned a 993, so maybe that's a senior moment.

Quote:

I looked at one of your links and found this picture of Rolls Royce Merlin engines being assembled in 1942.

Wicked. Always loved these motors as a kid. Outstanding some are still flying.

The R motors were pretty special though - had no idea until I read that Wiki that they were almost half as much displacement again as the Merlins...

JFairman · 09-29-2014, 08:24 AM

The 1976 930 heads I have don't say RR350 on them but the 1987 930 heads I used to have and sold did say RR350 on them.
I wonder if they just didn't have that number in the 1976 casting molds at the time or if they didn't start using that alloy until sometime during or after 1976. I wonder if anybody actually knows or if it makes any difference on a street driven motor.
I think you're probably right that they started using it for the race turbo motors and of course all the 930's got it at the same time.