924Board.org

[Peter_in_AU]

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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1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

[Mikri184]

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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Life is to short to be looking for something?

[CBass]

Depends which rod you're looking for. You should try the vwvortex.com in the classifieds.
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'81 931 in various states of assembly

[Peter_in_AU]

I'll follow those up.

Thanks.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

[Raceboy]

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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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
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[Peter_in_AU]

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.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

[leadfoot]

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
leadfoot

[Peter_in_AU]

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
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

[-nick]

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

[CBass]

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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'81 931 in various states of assembly

[Peter_in_AU]

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.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

[john h]

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]

[CBass]

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.
_________________
'81 931 in various states of assembly

[Peter_in_AU]

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.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you