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Transplanting 924 turbo engine on na
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Juho  



Joined: 03 Oct 2018
Posts: 160
Location: Finland

PostPosted: Thu Nov 26, 2020 1:32 am    Post subject: Transplanting 924 turbo engine on na Reply with quote

I found a turbo engine for sale, and i want to put it in a na car at somepoint. Do i have to get a turbo torque tube and transaxle aswell or use na weakee clutch?
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 965
Location: Maysville, Colorado

PostPosted: Mon Nov 30, 2020 12:42 am    Post subject: Reply with quote

No expert on the 931, but I would think the relocation of the starter from low right to high left would create several problems. I assume the starter relocation is required by the turbo. Do you graft a 931 bell housing to the NA torque tube? Then how do you actuate the clutch?
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Mike
Poco a Poco, #033 '78 Vintage racer, SCCA Dp-81
'77 924
cricketdesigns.com
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safe  



Joined: 18 Mar 2017
Posts: 210
Location: Sweden

PostPosted: Thu Dec 10, 2020 10:48 pm    Post subject: Reply with quote

A 931 bell housing should work and be the easiest.
931 flywheel, 931 pressure plate and a 915 clutch disk. I think (counting on it) that the 915 clutch disk will fit the NA torque tube.
I guess you need a 931 starter, clutch slave and master cylinders and whatever else you need to fix with the clutch.

It might just be easier to build a turbo kit for the NA engine.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, under EFI and turbo conversion
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morghen  



Joined: 21 Jan 2005
Posts: 8274
Location: Romania

PostPosted: Fri Dec 11, 2020 12:20 am    Post subject: Reply with quote

The NA gearbox, TT and clutch would hold the 931 power..maybe not for 200k km...but it would hold....the problem is not if they would hold, the problem is if they fit to the 931 engine. The 931 is a very different car from many points of view.
You should also get the torque tube and gearbox, as well as the clutch from the 931, also the servo clutch and the pedal assembly you need from the 931.
Depending on which 931 version you got it from, you also need engine bay wiring, ignition modules, sensors..its a different car.

Honestly if you want more from your 924, you could just sell the 931 engine and strap a modern turbo and efi to the NA engine, it will be faster than the 931 and cheaper to maintain. Or if you just want a little bit more and dont want to keep your car on jackstands for 1 year, you can buy the supercharger kit i will sell next year. Bolt on, 3-4h to install by yourself, everything included, reversible mod.
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Juho  



Joined: 03 Oct 2018
Posts: 160
Location: Finland

PostPosted: Fri Dec 11, 2020 6:37 am    Post subject: Reply with quote

my plan was to find a na engine but found a turbo one for a good price so i bought it, 924 engines are impossible to find here
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morghen  



Joined: 21 Jan 2005
Posts: 8274
Location: Romania

PostPosted: Fri Dec 11, 2020 6:34 pm    Post subject: Reply with quote

Well, hmm...depends on whats the state of that engine.
If i were you, i'd put all NA gear on that 931 block, and strap a modern turbo to it and efi it. But use the NA flywheel and upgraded NA clutch.
If i wanted to keep it without turbo, i'd take that 931 engine appart, replace the pistons with custom high compression ones, reassemble that engine using NA stuff and efi, and enjoy the 170hp+ it could make if tuned properly.
In any case, i'd keep the NA gearbox and TT as well as clutch, pedal and wiring.

So i'd either put NA gear & efi on the 931 engine and run it as a high CR NA or leave it as it is internally, put the NA gear on it and strap a modern turbo and efi to it. Either way, its more or less a waste of money since for mild street applications...there seems to be no real advantage of the 931 engine vs the 924 NA engine. I mean you can get 200hp from both and keep them reliable....its just the 931 is some extra money spent.
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safe  



Joined: 18 Mar 2017
Posts: 210
Location: Sweden

PostPosted: Fri Dec 11, 2020 6:47 pm    Post subject: Reply with quote

Juho wrote:
my plan was to find a na engine but found a turbo one for a good price so i bought it, 924 engines are impossible to find here


I think you can find one in your friendly neighbour to the west....

There is 3 engines in junkyards right now, but for to much money... But I think there is a bunch in storage around the country for OK money.
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Porsche 924 -79 NA, under EFI and turbo conversion
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11410
Location: PacNW

PostPosted: Sat Dec 12, 2020 1:29 am    Post subject: Reply with quote

You should consider a VW 1.8t...
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TJC  



Joined: 04 Apr 2010
Posts: 777
Location: Central-ish Arizona, USA

PostPosted: Sat Dec 12, 2020 3:21 am    Post subject: Reply with quote

morghen wrote:
Well, hmm...depends on whats the state of that engine.
If i were you, i'd put all NA gear on that 931 block, and strap a modern turbo to it and efi it. But use the NA flywheel and upgraded NA clutch.
If i wanted to keep it without turbo, i'd take that 931 engine appart, replace the pistons with custom high compression ones, reassemble that engine using NA stuff and efi, and enjoy the 170hp+ it could make if tuned properly.
In any case, i'd keep the NA gearbox and TT as well as clutch, pedal and wiring.

So i'd either put NA gear & efi on the 931 engine and run it as a high CR NA or leave it as it is internally, put the NA gear on it and strap a modern turbo and efi to it. Either way, its more or less a waste of money since for mild street applications...there seems to be no real advantage of the 931 engine vs the 924 NA engine. I mean you can get 200hp from both and keep them reliable....its just the 931 is some extra money spent.


There are some good points to be heeded here.
I think the biggest issue is how are you going to use the vehicle, how soon do you want to use the vehicle, how much time, effort and money do you want to spend and how much do you want to put up with in maintenance and obtaining difficult to find and/or costly parts to keep it running afterward?

I'm grappling with some of those same questions myself in my thought process when it comes to deciding what to do with the '80 924 Turbo that I have...but I'm seriously considering going the opposite direction that you are. In this forum and on various other 924 groups I'm constantly seeing how much of a hassle and how expensive it is to keep a bloody Turbo running, LOL! I'm seriously considering using the bits I have and building a simple Weber carbed, high compression, hot cam, properly exhausted, etc. engine that requires the least amount of Saturday morning tinkering to go out and blast around the mountains and canyons near my home. Hell, even a properly curved mechanical advance points type distributor, basic coil ignition system will be fine. !50-160 horsepower would do it for me as I would lighten the hell out of the car and concentrate more on handling and raw enjoyment...especially listening to the beautiful music a pair of dual throat Webers make combined with a raspy, burbling exhaust note!!!
But, it's your car and your time and money. And whatever you do, the most important thing is to have fun doing it. Don't make it a task or a job!
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'95 BMW 318i/5 ..."Pearl"
'80 Porsche 924 Turbo..."Pogo"
'81 Porsche 924 Turbo...Parting!
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"

Still on the Prowl!

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Juho  



Joined: 03 Oct 2018
Posts: 160
Location: Finland

PostPosted: Sun Dec 13, 2020 1:04 am    Post subject: Reply with quote

cant decide between high compression na or turbo engine, i just want to have a engine to build and keep driving my 924. i just want the turbo head to get better flow
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safe  



Joined: 18 Mar 2017
Posts: 210
Location: Sweden

PostPosted: Sun Dec 13, 2020 1:12 am    Post subject: Reply with quote

Juho wrote:
cant decide between high compression na or turbo engine, i just want to have a engine to build and keep driving my 924. i just want the turbo head to get better flow


High compression turbo. You have E85 in Finland right?
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Porsche 924 -79 NA, under EFI and turbo conversion
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Juho  



Joined: 03 Oct 2018
Posts: 160
Location: Finland

PostPosted: Sun Dec 13, 2020 3:42 am    Post subject: Reply with quote

I mean high compression na engine with turbo head
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 965
Location: Maysville, Colorado

PostPosted: Sun Dec 13, 2020 4:23 am    Post subject: Reply with quote

I have been porting and flow testing a 931 head. With the NA head unless some really serious porting(a la Gegge) is done the flow tends to stall at .400 lift. On the 931 head the flow continues to climb to .500 lift so much more potential. Due to changes in my testing methods I can't accurately compare the two. By cleaning up the casting/machining marks above the valve and smoothing and enlarging the sides of the short side radius I have gotten about a 8-9% improvement in flow using the existing valves and seats. I will install 7mm stem valves and the intake has a 12 degree back cut rather than the standard 20 degree. Several sources have said that the shallow back cut significantly helps on ports that turn about 90 degrees, the smaller valve stems will help also.
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Poco a Poco, #033 '78 Vintage racer, SCCA Dp-81
'77 924
cricketdesigns.com
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Juho  



Joined: 03 Oct 2018
Posts: 160
Location: Finland

PostPosted: Sun Dec 13, 2020 5:06 am    Post subject: Reply with quote

safe wrote:
Juho wrote:
my plan was to find a na engine but found a turbo one for a good price so i bought it, 924 engines are impossible to find here


I think you can find one in your friendly neighbour to the west....

There is 3 engines in junkyards right now, but for to much money... But I think there is a bunch in storage around the country for OK money.


I know this, but cant leave country because of my military service
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Juho  



Joined: 03 Oct 2018
Posts: 160
Location: Finland

PostPosted: Sun Dec 13, 2020 5:07 am    Post subject: Reply with quote

Rasta Monsta wrote:
You should consider a VW 1.8t...

I would 100% do that if i had tools and space to fabricate+its hard to make it street legal
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