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VW GTI Rods
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Peter_in_AU  



Joined: 29 Jul 2001
Posts: 2740
Location: Sydney, Australia

PostPosted: Sat Jan 22, 2005 9:38 am    Post subject: VW GTI Rods Reply with quote

anyone have any thoughts on where I might be able to pick up a set of GTI rods at a reasonable price?

I'm going to rebuild my spare engine and figure I'll replace the rods if I can get them at a good price. Unfortunately the budget doesn't run to a set of Pauter rods and the engine doesn't justify them anyway.
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1982 924 (As featured on Wikipedia)

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Mikri184  



Joined: 12 Sep 2003
Posts: 746
Location: Ferndale, WA

PostPosted: Sun Jan 23, 2005 5:11 am    Post subject: You might try Reply with quote

I know these folks have so much VW stuff it is ridiculous. Try asking them if they can hook you up. They usually sell all there stuff very cheap. And there service isn't too bad. They can be found on Ebay, Hope it helps
madpartsprincess
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7948402642&category=33626
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CBass  



Joined: 03 Nov 2002
Posts: 2807
Location: Vancouver, Canada

PostPosted: Mon Jan 24, 2005 7:42 am    Post subject: Reply with quote

Depends which rod you're looking for. You should try the vwvortex.com in the classifieds.
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Peter_in_AU  



Joined: 29 Jul 2001
Posts: 2740
Location: Sydney, Australia

PostPosted: Mon Jan 24, 2005 12:45 pm    Post subject: Reply with quote

I'll follow those up.

Thanks.
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1982 924 (As featured on Wikipedia)

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Raceboy  



Joined: 01 Mar 2004
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Location: Estonia, Europe

PostPosted: Wed Jan 26, 2005 8:12 pm    Post subject: Reply with quote

Kinda weird question maybe, but when you use VW GTI rods, what year and what displacement of the engine would fit? Are the journals same as 924?
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Peter_in_AU  



Joined: 29 Jul 2001
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Location: Sydney, Australia

PostPosted: Wed Jan 26, 2005 10:54 pm    Post subject: Reply with quote

It's the early (Mk1 I think) Golf/Rabbit/Jetta 1.8 litre GTI. The rods are the correct length but the pin diameter and the big-end bore is different. They are both smaller so it's not a straight swap but if you're doing a rebuild and swapping pistons and getting the crank ground then it's not really an issue.
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leadfoot  



Joined: 11 Dec 2002
Posts: 2222
Location: gOLD cOAST Australia

PostPosted: Wed Feb 02, 2005 6:32 pm    Post subject: Reply with quote

try : performance9 , volksaffair or asv (european auto spares), wolfsburg automotive (great range of second hand parts but have had unreliable service from these guys)
what size length are the 924 rods??
Volkswagon motors mainly use four different rod lengths:
1.5,1.6,1.7 litre motors all use 136mm rod with a 22mm piston pin
1.8 uses a 144mm rod with a 20mm pin
Diesel uses a 136mm rod with a 24mm pin
'93 tall block uses 159mm rods not sure of pin
'98 A4 uses 141mm rods not sur of pin
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Peter_in_AU  



Joined: 29 Jul 2001
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Location: Sydney, Australia

PostPosted: Wed Feb 02, 2005 9:32 pm    Post subject: Reply with quote

thanks for the tips leadfoot.

The 924 rods are 144mm with a 24mm pin and a 51.6mm big-end bore. The length is right but the pin and big-end are smaller on the GTI rods. The smaller big-end bore is probably a good thing if you're getting the crank ground.

http://www.pauter.com/4340_rods.htm has the specs for quite a few rods although the weights are for their rods and this one http://members.aol.com/FE3N/rods.html has heaps.

I'll have to sit down and do the maths to see if I use my new 87mm flat-top VW pistons with the 931 head I've got what rod length I'll need to get some good compression for a NA. Alternatively, a longer rod would allow me to use a cheaper, more modern piston with a lower compression height.

Too many options, not enough money
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-nick  



Joined: 16 Nov 2002
Posts: 2700
Location: Cambridge, MA

PostPosted: Thu Feb 03, 2005 4:31 am    Post subject: Reply with quote

Woah, there's a thought: vw pistons + 931 head + shave ~ .040" = ~ 9.4:1 perfect NA combination! Why hasn't this ocurred to me before? This may be the answer a lot of you folks are looking for.

It looks like the 1.8L GTI rods would work perfectly. You would need to turn the crank .040", otherwise they look good. Does anyone know if the weights listed by Pauter are the stock weight, or the Pauter rods weight? I'd like to know if there is a substantial savings with these vw rods.

Great find!

nick
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CBass  



Joined: 03 Nov 2002
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Location: Vancouver, Canada

PostPosted: Thu Feb 03, 2005 5:16 am    Post subject: Reply with quote

Those rods shouldn't be hard to find used. The 1.8 liter GTI engine is called the JH, and the common thing to do with a JH engine is to replace the bottom end with the 2.0 Audi 80 bottom end, or the 90s 2.0 ABA VW botom end, leading to a torquier motor.

So the goal here is to use the VW piston and rod with the 924 crank? The crank could be offset ground for a few extra cc's.

What's the compression height on those VW pistons vs the 924 pistons?
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Peter_in_AU  



Joined: 29 Jul 2001
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PostPosted: Thu Feb 03, 2005 7:46 pm    Post subject: Reply with quote

The specs that I've found say that the type 1 VW pistons have a compression height of 39.6mm. This isn't an official number, just from a couple of piston manufacturers. The 924 NA euro piston has a compression height of somewhere between 41mm and 41.3mm according to my digital calipers.

I've taken the data in the list of rods I linked to earlier and converted it to MS Excel format so you can sort and compare more easily. I've also uploaded the ACL pistons catalogue so you can get specs on suitable pistons. ACL is an Australian company so the pistons they offer are what's popular here.

The rod list is here

The piston catalogue is here it's about 15meg.

One very interesting thing when you look at the piston catalogue is that the only pistons that approach the specs of 924 pistons (compression height and pin size) are for diesel engines. Sort of backs up the idea that these engines are seriously over-engineered for a petrol engine.
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john h  



Joined: 06 Nov 2002
Posts: 827
Location: Wellington New Zealand

PostPosted: Fri Feb 04, 2005 11:22 am    Post subject: Reply with quote

Without seeing the piston's and rods - but from reading a few other posts where Racing for example mentions the VW 87 mm pistons sit about 5 mm below the block - you could then use the Mitsubishi 4G63 early conrods which are about 5 mm longer than the 924's and could be machined to suit crank journal diameter and width.

What's the reason behind going for the Golf rods anyway?
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Peter_in_AU  



Joined: 29 Jul 2001
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PostPosted: Fri Feb 04, 2005 11:40 am    Post subject: Reply with quote

john h wrote:
What's the reason behind going for the Golf rods anyway?


For me it's a weight saving thing and as I'm replacing the pistons anyway I'm looking at options.
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1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

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CBass  



Joined: 03 Nov 2002
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Location: Vancouver, Canada

PostPosted: Fri Feb 04, 2005 1:33 pm    Post subject: Reply with quote

IIRC, the JH head has a quench style combustion chamber, so it will have much less dish in the piston than the 924 NA piston will.

The North American version of the JH only has 8.5:1 compression, I know that much.
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Peter_in_AU  



Joined: 29 Jul 2001
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PostPosted: Sat Feb 05, 2005 12:34 pm    Post subject: Reply with quote

I bought these on ebay last night for a big $10.50 plus $8.50 shipping can't complain at $4.50 each for new pistons:


They are for a Toyota 2Y motor and are 40thou over which makes them 87.0mm, have a compression height of 34.7mm and a pin diameter of 22mm. If I team them up with later Mitsubishi 4G63 rods which are 150mm long I'll end up with the same overall length as the NA 924 rods and pistons.

One nice plus with the mitsu rods is that the bore is 3.6mm smaller than the 924 rods so I can get the crank offset ground and pick up an extra 3.6mm of stroke. Remember, this is a NA motor I'm building so every little bit counts.

[Later] Just did the numbers and 87mm pistons with an extra 3.6mm stroke (taking it to 88mm) gives a capacity of 2092.5cc an extra 109cc. Woo Hoo.
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