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Decking block
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Juho  



Joined: 03 Oct 2018
Posts: 391
Location: Finland

PostPosted: Wed Aug 25, 2021 11:08 pm    Post subject: Decking block Reply with quote

How much you can deck the block? Timing belt issues? I need to shave off 1.5-2.5mm for desired compression.
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safe  



Joined: 18 Mar 2017
Posts: 631
Location: Sweden

PostPosted: Thu Aug 26, 2021 6:50 am    Post subject: Reply with quote

Yes, you need a shorter belt. One tooth I think.
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Juho  



Joined: 03 Oct 2018
Posts: 391
Location: Finland

PostPosted: Thu Aug 26, 2021 3:13 pm    Post subject: Reply with quote

https://www.autodoc.fi/contitech/1210771

Yeah volvo guys get 1 teeth shorter when decking blocks +2mm.
Found this should work right?
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safe  



Joined: 18 Mar 2017
Posts: 631
Location: Sweden

PostPosted: Thu Aug 26, 2021 5:54 pm    Post subject: Reply with quote

Not sure. I have friend who has decked the block 1.5mm, I know he runs a shorter belt, but I don't know where he gets it. Its a bit tight to get on the engine, you really don't have to tension the tensioner...
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
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Juho  



Joined: 03 Oct 2018
Posts: 391
Location: Finland

PostPosted: Thu Aug 26, 2021 6:30 pm    Post subject: Reply with quote

Could you ask him what belt he runs?
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safe  



Joined: 18 Mar 2017
Posts: 631
Location: Sweden

PostPosted: Thu Aug 26, 2021 7:14 pm    Post subject: Reply with quote

Juho wrote:
Could you ask him what belt he runs?


Yes.
He says,1 tooth shorter, he gets them from Mittelmotor.

Mottelmotors webshop really really sucks if you cant find it, so you might have to call them or email, but they suck at email too...
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/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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Juho  



Joined: 03 Oct 2018
Posts: 391
Location: Finland

PostPosted: Thu Aug 26, 2021 9:21 pm    Post subject: Reply with quote

safe wrote:
Juho wrote:
Could you ask him what belt he runs?


Yes.
He says,1 tooth shorter, he gets them from Mittelmotor.

Mottelmotors webshop really really sucks if you cant find it, so you might have to call them or email, but they suck at email too...


Have to email them, they might just be selling audi belts at a higher cost?
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Juho  



Joined: 03 Oct 2018
Posts: 391
Location: Finland

PostPosted: Thu Aug 26, 2021 9:31 pm    Post subject: Reply with quote

Found it on the shop, 50 euros for one belt might have to look in to the audi belts because i have a feeling they might be selling them at a higher cost.
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TJC  



Joined: 04 Apr 2010
Posts: 828
Location: Central-ish Arizona, USA

PostPosted: Fri Aug 27, 2021 12:36 am    Post subject: Reply with quote

It would seem to me that perhaps the best source would be to contact your favorite belt manufacturer directly rather than going through some middleman to discover which size belt you need to purchase. They would most likely have all the specifications and with a little work they may provide you with the proper belt part number so you may go shopping for the best deal.
Then once you know the standardized belt number and are sure that it works properly you may tell the world...or keep it to yourself, buy up a supply of shorter belts and resell them as at a huge profit to compensate for the bit of time and effort put into sourcing them in the first place...like Mittlemotor, perhaps!
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DZGunner  



Joined: 18 Nov 2014
Posts: 191
Location: Great white north

PostPosted: Mon Oct 04, 2021 3:49 am    Post subject: Reply with quote

You keeping the stock internals with this compression ratio upgrade?
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Juho  



Joined: 03 Oct 2018
Posts: 391
Location: Finland

PostPosted: Mon Oct 04, 2021 3:12 pm    Post subject: Reply with quote

no, 931 head vw flat tops, forged rods
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Mclaren924  



Joined: 13 Oct 2021
Posts: 199
Location: California

PostPosted: Fri Aug 09, 2024 11:46 am    Post subject: Reply with quote

Juho wrote:
no, 931 head vw flat tops, forged rods


You ever get around to milling the block Juho? I'm thinking about taking 2.5 mm off with a 931 head and stock na bottom end. Seen multiple people mention taking 2.5 off or .100 thou but nobody posts afterwards. Will be intercooled ethanol only of course and even then will be spicy. Will be checking piston to valve clearance tonight with a degree wheel and checking springs. They say 2mm clearance for intake and 2.5 mm for exhaust so will see how much can really be had. Dumb question maybe but what about head bolts, i assume they would no longer fit stock ones and would need different bolts/studs?
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924RACR  



Joined: 29 Jul 2001
Posts: 8846
Location: Royal Oak, MI, USA

PostPosted: Fri Aug 09, 2024 9:54 pm    Post subject: Reply with quote

I would be surprised at a need for different head fasteners - but I would think it would be obvious that you'd want the ARP studs for that build. Pretty sure there's enough play with those to not have to worry. Just make sure you clean the threads in the block fully, which should be part of the job anyway...
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Vaughan Scott
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Mclaren924  



Joined: 13 Oct 2021
Posts: 199
Location: California

PostPosted: Sat Aug 10, 2024 2:37 am    Post subject: Reply with quote

924RACR wrote:
I would be surprised at a need for different head fasteners - but I would think it would be obvious that you'd want the ARP studs for that build. Pretty sure there's enough play with those to not have to worry. Just make sure you clean the threads in the block fully, which should be part of the job anyway...


Yeah I'm debating how far I want to take this build. I'm thinking skim both head and block and throw in a cometic but the headstuds will add a decent price increase. Debating if the stock pistons will even be able to handle enough boost for the head to lift. What head stud setups do you guys normally run? It really is a science experiment to see what the bottom end can handle when compression is cranked up and boost is fed to it. Ultimately I'm looking for a "cheap" way to get a more responsive and powerful motor with less boost. In the end I'll probably feed it as much as it can handle to see it's true potential or lack there of. Forged pistons and rods with big bore is what everybody wants but that's 3k at least before you start getting into other parts needed to round out the build.
Will be calling machine shops today to get quotes on decking and surfacing of mating surfaces. Hoping to have head and block done for around 3-400$ we shall see... I'm often surprised at costs now.
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1980 931 "Salt" Bucket wannabe racer (not started)
1979 924 "Pepper" Restoration (almost done)
1980 924 "Donnie" (Parts car)-DEAD
1977 924 Slicktop "Pennie" Bucket turned Silver Spoon
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924RACR  



Joined: 29 Jul 2001
Posts: 8846
Location: Royal Oak, MI, USA

PostPosted: Sat Aug 10, 2024 3:55 am    Post subject: Reply with quote

Fairly certain this is the head stud kit:
https://www.summitracing.com/parts/arp-251-4701/make/ford
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Vaughan Scott
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