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Mclaren924 · Joined: 13 Oct 2021 Posts: 253 Location: Oceanside CA

You are right Ciprian, I believe the housing was indeed machined to accommodate bigger wheel.

After talking with the customer, we just opted for a stock s1 flywheel. Going to take a page out of your book and stick with what the engines design benefits and just feed it more boost and keep rpm down. Ultimately the head is completely stock minus an adjustable cam pulley so the top end couldn't handle extreme abuse either. We may run a set of stiffer springs that mittlemotor has.

Just got the centerforce pressure plate and the flywheel and morghens crank pully dropped off to machine shop and they should have it all balanced and ready to go for us tomorrow.
The body shop has the engine bay almost completely stripped down and has a good paint match ready to go, hoping that's done this week too. We shall see
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1980 931 "Salt" Bucket wannabe racer (Dreaming)
1979 924 Sebring "Pepper" -Sold
1977 924 Slicktop "Pennie"-Most likely parts
1979 3/5 gt clone 924- Shop Test Car

Mclaren924 · Joined: 13 Oct 2021 Posts: 253 Location: Oceanside CA

Sorry for sparse updates, not from lack of desire. Machine shop just finished the machine work on monday. So much for it being done 3 weeks ago lmfao.

In all they decked both surfaces, replaced all valve guides and reground valve seats as well as ground old valve mating surfaces for a good seal. The bore was punched out to match the 88mm piston and the crank was line bored to help fix distortion caused by ARP main studs. DO NOT install main studs and go on your merry way, you absolutely need machine work to help true up the crank journals again. Lastly they polished the crank and checked the head and block for cracks, and balanced the whole rotating assembly including flywheel/PP and crank pulley. Took about 3 months and was about 2k USD down here in socal. Unfortunately this is the fastest and cheapest it gets while still getting quality work.

Speaking of which I mic'd out all the journals and all the main bearings were around .002 of clearance, went to check rod bearing clearance and it looks like my 1.5-2.4 in dial bore gauge shit the bed on me so I was stuck using the T style bore gauges and got an average of .0025 for the first rod bearing I tried. Will measure all 4 again tomorrow when my snap on guy comes by with a new dial bore gauge, I'm pretty sure it is going to be fine but I had slight concerns that the arp2000 rod bolts calling for 50 ft lbs may distort the bearing tolerances without any machining. So far it seems I was wrong in that concern as like I said, right around .0025 clearance. Double checked rod stretch and was within desired .005-.006 spec. Getting a real dial gauge in there tomorrow will put me at ease. Tomorrow will get rods squared away if everything is good measurement wise then will setup the rings. JE leaves the rings long and gives you a bunch of different applications and their desired ring gap so will have lots of fiddling to do with that. Will also have to check block bore is good for piston but I'm hoping the machine shop could handle that...

Will post more updates tomorrow or day after and what's going on with the build. Apparently chassis comes back on Tuesday from having engine bay painted.

Besides this I had a super weird and ill timed issue with another customer car, was a 77 martini we did a motor and basically complete mechanical/electrical overhaul for. The car left with 150 psi on all 4 cylinders and a good idle with lots of power, no leaking injectors and a new fuel filter/ a good FD swapped on as old one was bad. The plugs were swapped after initial tune up and run in was done and it never ran without an AFR gauge on it and was always ran around 14 area. It did have the classis hard start when left to sit hot for hour or so.

He comes back monday to try and fix hot start and I pull plug 1 to see what fuel mixture looks like and it is covered in chunked up carbon. Wtf I say, run comp test and down to 90 on all 4 and all 4 have carbon all over plugs. I scope all 4 and there's insane carbon build up everywhere. Pull the motor out and the entire valve seat/head/pistons are caked in it. Pull everything apart and no signs of any mechanical damage. Engine goes back in tomorrow and will run through the entire fuel system again from injectors to pump. The tank in the car is horribly rusty and despite emptying, shop vaccing, flushing, and repeating twice, I think it is still contaminating the fuel system somehow. I'm not sure how this much carbon could build up in 1500 miles or so, I think of maybe the FD is directing too much fuel to injectors, cold start stuck open all the time, all 4 injectors leaking or stuck open(I highly doubt as they're new). would love some thoughts on this side tangent

https://imgur.com/vhLyrzB

https://imgur.com/N1PP9ih

only reason no 1 is clean is because we just cleaned it out
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1980 931 "Salt" Bucket wannabe racer (Dreaming)
1979 924 Sebring "Pepper" -Sold
1977 924 Slicktop "Pennie"-Most likely parts
1979 3/5 gt clone 924- Shop Test Car

Mclaren924 · Joined: 13 Oct 2021 Posts: 253 Location: Oceanside CA

Well the 77 martini car was bad news, about a 1/4 pound of rust was scraped out from bottom fuel bowl and there's way more. Words can't even describe how bad it is, just watch the video. Owner said he had the tank redone and coated 10 years ago and it has since failed and been stirred up or aggravated by the cars awakening from it's 4 year slumber. He will be going with a new tank, strainer, filter, and sender. May wind up replacing accumulator too if its really nasty. Will need to blow through all the lines and hope the kjet parts didn't suffer.

https://imgur.com/uDqivpW

https://imgur.com/gacM2Rq

The 931 motor is going together nicely. Have been so dammed busy moving houses and finishing moving into the shop, it has been hard to get all my ducks in a row. Finally got the crank in, ring gap all set and confirmed piston to wall clearance and bearing clearances were good. Can post exact numbers next time I'm in shop, just need to get the pistons installed on the rods and then slipped in the bores and the bottom end is assembled. Chassis will be back from paint this coming Monday and then it's going to get going fast from there!

Also just got in the mittlemotor adjustable cam pulley and their valve springs, all in all $550 or so. $180 were tariffs, thanks Donnie

Even so, that's a pretty good price for all 8 inner and outer valve springs plus the cam gear.
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1980 931 "Salt" Bucket wannabe racer (Dreaming)
1979 924 Sebring "Pepper" -Sold
1977 924 Slicktop "Pennie"-Most likely parts
1979 3/5 gt clone 924- Shop Test Car

Cedric · Joined: 27 Aug 2004 Posts: 2776 Location: Sweden

For the cam pulley theres plenty of VW wheels available aswell, i run one from a vw tuner shop

I had to rebore the rods, but they where used std rods with ARP screws, need to double check how hard those where torqued.

Do a fuel balance test on that martini, run the injectors in bottles an measure the weight, should be within a few percent.
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1980 924 Turbo
www.instagram.com/garagecedric/

Mclaren924 · Joined: 13 Oct 2021 Posts: 253 Location: Oceanside CA

Cedric do you mean the old group buy arp hardware meant for 924 rods or the alfa variants that are very similar? God I read these forum posts and a part of me feels like I missed the 924 golden age with Ideola running his shop and the community being so active. Another part of me feels like this is the golden age with kits like ciprians being sold and all the other awesome support the 924 has been getting and how much technology has advanced. Also how we benefit from all their trials and tribulations.

I was a little concerned what the rods were going to measure out to being they're aftermarket and the crank wasn't turned specifically for them but they would up being perfect, same with side clearance between piston and journal. Really nice product from Pauter.

Good news about the VW cam pulley, the mittlemotor one was actually fairly priced and I was mostly interested to see if what came with their valve set for 180 Euros. Their customer service wasn't great which is probably my fault for being on wrong side of planet and not speaking german lol. Am very happy with their complete inner and outer set for the price, currently not a lot of options for springs that don't break the bank.

Maybe I'm wrong but as far as I know, please correct me if so. There's nobody making off the shelf performance valve springs for these cars? Most people wind up redoing the whole setup with different lifters, lash caps, and all that jazz which isn't super enticing for a street car that will never see super high rpm. Maybe you could have some custom springs made to work with stock lifters but what's the point of only doing part of the weight reduction...Rambling here sorry

The Martini Car will need to have all the injectors tested and the WUR recalibrated along with probably tuning the FD, really a bummer with that car. Unfortunately a tale told on here very many times too, as the saying goes.There's no such thing as a cheap porsche.

I just got back in the shop from thanksgiving seeing family and waiting till monday to call JE to see if these pistons are bi directional or not. There is no markings on them or any statement in the instructions, as well as the ring orientation can be set based on the piston correctly with it in both directions. 99% sure it does not matter but finding out after the head and turbo kit was on would really suck. Will get the head put back together tonight and tomorrow so I can put it all together once I get the word from JE. IF one of you fine gentleman who installed these pistons before and want to save me some waiting, i'd be very thankful. Until then, thanks for reading my late night ramblings and will update again soon. Hopefully get chassis on monday...

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1980 931 "Salt" Bucket wannabe racer (Dreaming)
1979 924 Sebring "Pepper" -Sold
1977 924 Slicktop "Pennie"-Most likely parts
1979 3/5 gt clone 924- Shop Test Car

924RACR · Posted: Sun Nov 30, 2025 10:43 pm Post subject:

Re: valve springs - I went with new stock original Porsche parts for my builds (NA racecar - ITB and HP motors)... nice that they're now available as such!

On my GSXR motors (in the prototype), my pro engine builder (best in the country, many Runoffs wins) has stated that factory Suzuki ones are the best, every other aftermarket spring he's broken. I've had aftermarket ones break on the track. Just don't have the same quality control as factory.

So I don't know if that applies to the Porsche parts... but I'd bet it does.

We just shimmed our stock springs up, is all... per Dima's recommendation for the HP cam.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Mclaren924 · Joined: 13 Oct 2021 Posts: 253 Location: Oceanside CA

This was a concern I had about the springs, I've seen a lot of heartbreak first hand with some of my chevy customers when they get supplied wrong or cheap springs and things fail badly. I plan on running these mittlemotor springs in a personal engine and will see how they fair. It's not worth the risk trying them in a customer build and having to pull a head because of a part failure due to manufacturing standards being bad. Pulling a 924 head would be one thing, pulling a 931 head off in car would be a whole different level of hurt.

This customers original springs had very similar rates compared to a new porsche one I supplied my machine shop to test with so I have no concerns reusing old ones. Especially being this is a street car.

In your case 924racr, if its a 931 head. Do you remove all the rotowashers and shim up the missing depth there too or do you shim under them? Similar question for NA's. I think I've heard you mention this before on the board too.

Aside from that I Just got done cleaning up some casting marks on the intake ports and matching the head to the intake gasket, not going to touch anything inside the port as A the valve guides already in there and B without a flow bench or a lifetime of experience porting heads (I have neither), it's really not a wise idea to mess with ports. Also I think it's probably pointless doing a bunch of port work with a stock manifold on it, just spend the money to do a much better intake and I think then maybe extensive port work to match the new intake may make sense. This is at least what I gained from reading mike931's custom head work build. Not to say he didn't make huge improvements in flow over a stock 931 because he without a doubt did, the effort and money to achieve that would probably be better spent on the intake. Which he also denotes the stock intake being a huge issue with porting and trying to improve the 931 flow.

I am debating making a gts/gtr intake manifold setup and having it tested on the dyno vs the stock intake when this car goes to get tuned. Would be really interesting to see real life results of stock vs gts/gtr style and no port work and then of course ported in junction with new style intake. Mike if you're reading this

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1980 931 "Salt" Bucket wannabe racer (Dreaming)
1979 924 Sebring "Pepper" -Sold
1977 924 Slicktop "Pennie"-Most likely parts
1979 3/5 gt clone 924- Shop Test Car

924RACR · Posted: Mon Dec 01, 2025 4:45 am Post subject:

In our case - no, NA head not a 931 head. Pretty sure the shims were under the lower seats, seems like the only thing that'd make sense.

I do some day want to make up a GTR style intake for my 931 - since it's running the 951 IC. I have a sectioned stock 931 intake which just needs rework... but it's been a super-low priority task anyway... especially since I've been working on the interior and cosmetics instead! LOL
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Cedric · Joined: 27 Aug 2004 Posts: 2776 Location: Sweden

Mclaren924 · Joined: 13 Oct 2021 Posts: 253 Location: Oceanside CA

Cedric · Joined: 27 Aug 2004 Posts: 2776 Location: Sweden

Mclaren924 · Joined: 13 Oct 2021 Posts: 253 Location: Oceanside CA

What a crazy month it has been! Happy holidays everyone and time for some updates!

The pistons were machined incorrectly by JE, there are actually two other sets of #### up pistons sitting on EBS'S shelf that have same exact issue as mine. For whatever reason EBS decided to spec the piston to have "Custom" work done to it by milling down the pin boss area to fit the connecting rod they chose. Ultimately JE missed the custom work part and shipped them with the standard pin boss they have for the part, resulting in my rods not fitting.

First and foremost I blame myself for one, not catching this in my initial CQ check when they first arrived, I neglected to check pinboss diameter and could have caught it all before the machine shop. Ultimately I didn't and the block got punched out to fit those pistons meaning there's no getting a different piston or anything like that. Especially with the coating being ran on these pistons, they never come to an exact size as listed.

This left me with two options. either send the pistons back to JE on my dime both ways and have them take weeks to correct pinboss, or I find another set of rods that will work. Long story short is God was watching and threw me a bone, 2 days later another 931 enthusiast posts on FB essentially the same set of JE pistons and PAuter rods for sale for 30% under retail. The rods wound up being the exact same rod but with a .100 thinner small end with and weight was almost exact. Truly couldn't have gotten luckier with the timing, Jim if you're reading this. Thank you again buddy.

I will say i'm not super pleased with EBS either, it seems super convoluted to have JE make modifications to the pinboss when they have rods and piston combos that fit without issue. Essentially, the custom rods they spec'd for me could have worked on the other set of pistons I obtained as those pistons had a wider pin boss.... Meanwhile my original pistons will fit the second sets rods with no issue... To me that just seems like a recipe for a ####, why not just spec a set of known fitting and working parts instead of having custom stuff done. Sorry If I lost you here, will post the rod and piston specs down below.

My Pistons and rods

The set I got to fix my issue

With the piston and rod debacle behind me, the motor went together pretty smoothly. Customer has gone back and forth so many times on the front mount setup vs top mount, finally have him set for a front mount intercooler and GTS style intake. May wind up making our own replica because to import the mittlemotor one, it would be almost 5k all said and done. I have thought about buying one in person when I fly over to germany in a 3-4 weeks and just shiping it to myself... Negate VAT and the orange man tarrif all at once. Currently just has a s2 intake to keep it all covered up. A lot of the bracketry and some covers are off being powder coated as well.

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1980 931 "Salt" Bucket wannabe racer (Dreaming)
1979 924 Sebring "Pepper" -Sold
1977 924 Slicktop "Pennie"-Most likely parts
1979 3/5 gt clone 924- Shop Test Car