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Mclaren924
Joined: 13 Oct 2021
Posts: 265
Location: Oceanside CA
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 Posted: Wed Apr 22, 2026 4:20 am Post subject: |
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Mistype on the last one, they're 30 mm bars sorry about that guys
I'm thinking replating too, glad I wasn't worried about nothing
Yes I've followed magnus's and the italians build and they've both demonstrated that the stock intakes work well for making power, especially when cramming 40 psi into it. I'm interested in what improvements can be made to head/intake to produce same power at lower peak boost. Talking to my machine shop yesterday, he does BMW s58 heads where stock they require 34 psi of boost to make the same power his ported heads do at 26 psi. I wonder what could be squeezed out of a 924/931 head and what is better to squeeze.
I understand and appreciate your approach cedric as it is built from first hand experience and lots of testing, you are 100% right that the vast majority of people will not be able to overpower the bottom end before seeing issues like exploding clutches, transmissions, spinning tires, and other things. Hence going looking for power in the head/intake is foolish when a modern dual journal turbo will quickly overpower even a built bottom end. Thus making it not financially feasible for most to explore the head/intake setup past a diy port.
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1980 931 "Salt" Bucket wannabe racer (Dreaming)
1979 924 Sebring "Pepper" -Sold |
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Cedric
Joined: 27 Aug 2004
Posts: 2806
Location: Sweden
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| Posted: Wed Apr 22, 2026 4:54 am Post subject: |
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| Mclaren924 wrote: | Mistype on the last one, they're 30 mm bars sorry about that guys
I'm thinking replating too, glad I wasn't worried about nothing
Yes I've followed magnus's and the italians build and they've both demonstrated that the stock intakes work well for making power, especially when cramming 40 psi into it. I'm interested in what improvements can be made to head/intake to produce same power at lower peak boost. Talking to my machine shop yesterday, he does BMW s58 heads where stock they require 34 psi of boost to make the same power his ported heads do at 26 psi. I wonder what could be squeezed out of a 924/931 head and what is better to squeeze.
I understand and appreciate your approach cedric as it is built from first hand experience and lots of testing, you are 100% right that the vast majority of people will not be able to overpower the bottom end before seeing issues like exploding clutches, transmissions, spinning tires, and other things. Hence going looking for power in the head/intake is foolish when a modern dual journal turbo will quickly overpower even a built bottom end. Thus making it not financially feasible for most to explore the head/intake setup past a diy port. |
The drawback with immense boost levels is it takes sone time to get there, and you need very high turbo efficiency (amd preferably e85)
You are thinking on something more like Joakims engine, probably the most well built. Very extensive porting, cams, itb and twinscroll Turbo manifold in its latest iteration. Sadly its been off the road for many years, so havent had a ride in it. It would be a significantly better engine for track use, with good response and much better rev range. On e85 he could probably have pushed quite a bit more power out of it.
https://youtu.be/Maae0lF1mXs?is=D5FuR_jhNQrNxB77
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1980 924 Turbo
www.instagram.com/garagecedric/ |
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Cedric
Joined: 27 Aug 2004
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Mclaren924
Joined: 13 Oct 2021
Posts: 265
Location: Oceanside CA
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| Posted: Thu Apr 23, 2026 2:54 am Post subject: |
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We need to get you the official title of 924.board historian cedric. Crazy the thing you can reference from so far back in time with pictures and videos and all. Very helpful and impressive.
Yes I remember reading about jokiams engine and the offset valves and extensive work required to get there. What is crazy is that he made this on pump gas at roughly 1.56 bar... Imagine would could be possible with a cylinder head like that with a built bottom end and modern turbo/ e85.
Ultimately HP is just a number and the graph/usable power is what's important and that's what's so enticing about jokiams build. A much better rev range with more freedom to rev and so on. Unfortunately the cost to do this is so prohibitive especially to somebody who can't do the work themselves. I absolutely understand why nobody has done it yet.
Picking up spring plates from shop today and hopefully get it all together today in the car as this thing has been an post turtle on my lift for almost a week while we wrap up suspension and brakes. Need to get it off so I can put up a second lift in the shop. Literally have 924's falling out of my ears over here.
This 931 gts "rally" clone build
A complete mechanical and paint resto martini thats coming back from paint next week that needs us to put the new motor in and put an EFI kit on it. Also did a 5 speed swap and new gas tank among a million other things
A 78 auto 924 that's getting 5 lug swapped and 5 speed turbo trans swapped, will be doing a 944 brake setup in this car with brake bias adjuster very similar to the 931 GTS clone
Another customers 80 931 safari build that classically has a kjet system riddled with issues and orange fanta coming out of the tank
A 79 924 that is getting unmolested after PO did an "overland" conversion and put 27" tires on it with a 2" spacer lift, custom wood panel interior, a gas cooker in the back, and a roof top tent.... Poor old thing is going to get some nice 5 lug shoes swapped on her and a 944 master/ bias setup too.
Not counting the 951 that's getting a clutch, cylinder head, rod bearings and all the other assorted goodies and this 996 were taking from a 3.4->3.8, I think I need a second set of hands or three over here 
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1980 931 "Salt" Bucket wannabe racer (Dreaming)
1979 924 Sebring "Pepper" -Sold |
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Cedric
Joined: 27 Aug 2004
Posts: 2806
Location: Sweden
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| Posted: Thu Apr 23, 2026 5:34 am Post subject: |
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| Mclaren924 wrote: | We need to get you the official title of 924.board historian cedric. Crazy the thing you can reference from so far back in time with pictures and videos and all. Very helpful and impressive.
Yes I remember reading about jokiams engine and the offset valves and extensive work required to get there. What is crazy is that he made this on pump gas at roughly 1.56 bar... Imagine would could be possible with a cylinder head like that with a built bottom end and modern turbo/ e85.
Ultimately HP is just a number and the graph/usable power is what's important and that's what's so enticing about jokiams build. A much better rev range with more freedom to rev and so on. Unfortunately the cost to do this is so prohibitive especially to somebody who can't do the work themselves. I absolutely understand why nobody has done it yet.
Picking up spring plates from shop today and hopefully get it all together today in the car as this thing has been an post turtle on my lift for almost a week while we wrap up suspension and brakes. Need to get it off so I can put up a second lift in the shop. Literally have 924's falling out of my ears over here.
This 931 gts "rally" clone build
A complete mechanical and paint resto martini thats coming back from paint next week that needs us to put the new motor in and put an EFI kit on it. Also did a 5 speed swap and new gas tank among a million other things
A 78 auto 924 that's getting 5 lug swapped and 5 speed turbo trans swapped, will be doing a 944 brake setup in this car with brake bias adjuster very similar to the 931 GTS clone
Another customers 80 931 safari build that classically has a kjet system riddled with issues and orange fanta coming out of the tank
A 79 924 that is getting unmolested after PO did an "overland" conversion and put 27" tires on it with a 2" spacer lift, custom wood panel interior, a gas cooker in the back, and a roof top tent.... Poor old thing is going to get some nice 5 lug shoes swapped on her and a 944 master/ bias setup too.
Not counting the 951 that's getting a clutch, cylinder head, rod bearings and all the other assorted goodies and this 996 were taking from a 3.4->3.8, I think I need a second set of hands or three over here |
Joakim lives not that far from here, so the locals are easy to keep track off. But my archives are big, bought my first 924 in 2003 and the 931 in 2006, so been around for a while.
His engine has really nice forged rods and pistons, it could most likely handle more than that, but he always kepts it on the safe side. It was very ambitiously tuned, always in an engine test bench, fine tuning every load and rpm. I hope he gets the car back out some day ! The drawback with putting shit loads of money on a head for example is if something goes wrong, it gets very expensive to replace it, 924 engines are dirt cheap still otherwise 
You really seem to drown in these cars, i guess when you started with a few, more of them comes in to get help. But 5 lug on a US spec auto, seems overkill 
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1980 924 Turbo
www.instagram.com/garagecedric/ |
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safe
Joined: 18 Mar 2017
Posts: 702
Location: Sweden
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| Posted: Thu Apr 23, 2026 5:10 pm Post subject: |
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| Mclaren924 wrote: | Mistype on the last one, they're 30 mm bars sorry about that guys
I'm thinking replating too, glad I wasn't worried about nothing
Yes I've followed magnus's and the italians build and they've both demonstrated that the stock intakes work well for making power, especially when cramming 40 psi into it. I'm interested in what improvements can be made to head/intake to produce same power at lower peak boost. Talking to my machine shop yesterday, he does BMW s58 heads where stock they require 34 psi of boost to make the same power his ported heads do at 26 psi. I wonder what could be squeezed out of a 924/931 head and what is better to squeeze.
I understand and appreciate your approach cedric as it is built from first hand experience and lots of testing, you are 100% right that the vast majority of people will not be able to overpower the bottom end before seeing issues like exploding clutches, transmissions, spinning tires, and other things. Hence going looking for power in the head/intake is foolish when a modern dual journal turbo will quickly overpower even a built bottom end. Thus making it not financially feasible for most to explore the head/intake setup past a diy port. |
This is the difference between a stock 931 head and a seriously ported one, Joakims.
The difference at higher RPMs are enormous.
I have a professionally ported NA head, still original sized valves, going on my engine. Don't know when I have time to get to that.
_________________
/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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924RACR
Joined: 29 Jul 2001
Posts: 9068
Location: Royal Oak, MI, USA
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| Posted: Thu Apr 23, 2026 9:12 pm Post subject: |
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Wow, those are impressive gains up high!!! Is that also larger valves than stock? I'd guess so?
Had an amusing discussion with an old timer over the weekend, looking at Turbos, he was trying to convince me they needed a cam... I guess he still doesn't understand what positive intake pressure does... LOL
As for the US car getting the 5-lug... it's also getting a 5-speed conversion, so the 5-lug would be quite suited if it's going to be hitting the track...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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safe
Joined: 18 Mar 2017
Posts: 702
Location: Sweden
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| Posted: Thu Apr 23, 2026 9:28 pm Post subject: |
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| 924RACR wrote: | Wow, those are impressive gains up high!!! Is that also larger valves than stock? I'd guess so?
Had an amusing discussion with an old timer over the weekend, looking at Turbos, he was trying to convince me they needed a cam... I guess he still doesn't understand what positive intake pressure does... LOL
As for the US car getting the 5-lug... it's also getting a 5-speed conversion, so the 5-lug would be quite suited if it's going to be hitting the track... |
Pretty sure it has larger valves, pretty much no stone unturned on that head.
The right cam help I'm sure, if the head can support it.
You had 4 speed 931's in the US?
I'm upgrading a G31 to put in my car. One piece bearing retainer, stiffer diff cover and an LSD.
_________________
/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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924RACR
Joined: 29 Jul 2001
Posts: 9068
Location: Royal Oak, MI, USA
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| Posted: Fri Apr 24, 2026 12:11 am Post subject: |
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No no - crossed signals, Cedric was referring to a '78 auto (so, NA) getting a 5-lug swap as overkill - except it was also getting a 5-speed swap. So, from 3 gears to 5!! LOL
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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Mclaren924
Joined: 13 Oct 2021
Posts: 265
Location: Oceanside CA
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| Posted: Fri Apr 24, 2026 9:12 am Post subject: |
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Jokiam's head is very impressive and especially it's ability to keep making power at high rpm.
Why did you choose the NA head over the turbo head for your big turbo setup Safe? I remember reading mike931 (i think) thread about head porting and he mentioned after his extensive fiddling that maybe the na head could be better option.
I think stock cam can do a lot for you with a adjustable pulley and lots of boost, of course there are gains to be had with a custom cam grind but I think extensive head work would have to be done first IMO before justifying custom specing a cam.
The customers 78 is a toofah auto 4-lug, we will do a 5-lug swap and a 5 speed turbo trans to boot. Only reason turbo trans is it's the only standard shift 5 speed i have left in my stash and a g31 wont fit as torsion bar is wrong and even if swapped the early chassis and standard 5 speed cars don't feature the mounts.
He is using it as a gateway car into autocross , hpde, and track driving, he has a beautiful 80k miles 83 3.2 carrera 5 speed we helped him find and did a bunch of suspension work to including some turbo tie rods and adjustable konis up front and he's understandably a little hesitant to go learning in that car first lol. Going to be night and day going from auto 3 speed to 5 speed...
Just got all the front suspension and brakes installed for final test fit, had to get creative removing the pillow ball setup that comes on the front coilovers in order to run a set of the racers edge camber plates. Truthfully not a huge fan of the way the top mount was made and glad it's being ditched. Just getting rear spring plates reassembled and the torsion bar ears getting new bushings installed.
Is it just me or has anybody else had some issues with powerflex poly bushings not seating all the way? Both real control arms they have to be really forcefully jimmied in and one of the spring plates one sit flush against the bushing while other does. No amount of pressing or redoing will fix it or get it flat. Im thinking that when they're installed it will keep it pressed together but my OCD is off the charts here.
_________________
1980 931 "Salt" Bucket wannabe racer (Dreaming)
1979 924 Sebring "Pepper" -Sold |
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safe
Joined: 18 Mar 2017
Posts: 702
Location: Sweden
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| Posted: Fri Apr 24, 2026 5:41 pm Post subject: |
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| Mclaren924 wrote: |
Why did you choose the NA head over the turbo head for your big turbo setup Safe? I remember reading mike931 (i think) thread about head porting and he mentioned after his extensive fiddling that maybe the na head could be better option.
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Just because it was an NA car with a stock NA engine, sort of an experiment.
I'm continuing with an improved NA base engine because I have forged pistons and everything it needs.
The turbo head is better no doubt. The angled valves of the turbo head makes the ports better and it makes it possible to fit larger valves. I also guess that with the pistons getting closer to the head you actually get squish and a better/safer combustion. The NA pistons stop so far from the head there is no squish.
David Wizard had paragraph in a book (that I cant find) where he describes improving an engine with a heron head. The gist of it was that the less heron you could make it, the better it performed. It was from improved combustion area with better squish.
| Mclaren924 wrote: |
I think stock cam can do a lot for you with a adjustable pulley and lots of boost, of course there are gains to be had with a custom cam grind but I think extensive head work would have to be done first IMO before justifying custom specing a cam.
The customers 78 is a toofah auto 4-lug, we will do a 5-lug swap and a 5 speed turbo trans to boot. Only reason turbo trans is it's the only standard shift 5 speed i have left in my stash and a g31 wont fit as torsion bar is wrong and even if swapped the early chassis and standard 5 speed cars don't feature the mounts.
He is using it as a gateway car into autocross , hpde, and track driving, he has a beautiful 80k miles 83 3.2 carrera 5 speed we helped him find and did a bunch of suspension work to including some turbo tie rods and adjustable konis up front and he's understandably a little hesitant to go learning in that car first lol. Going to be night and day going from auto 3 speed to 5 speed...
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The 924 and the 911 will act very different in an auto-x. The 924 will be much, much easier.
But as someone who has mostly driven old 911s in auto-x and on track, I would encourage him to use the 911, not because its better but because it will help him to get a handle on a 911, it will serve him well someday on the street. Auto-x is the safest way to approach the limits and learn how to react when its not on purpose.
_________________
/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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