.40 over pistons for 1.8L

[S2_ITBVW]

Is anyone familiar with this piston?

http://www.summitracing.com/parts/UEM-9078-1-0MM/

I spoke with the tech line for Keith Black and they indicated that this was an OEM replacement cast piston. So I think the specs are right from a "legality" standpoint. However, the tech folks could not provide the exact compression ratio, only that it would produce the "stock" compression for the engine.

This is the application information:

Make VOLKSWAGEN
Engine Type L4
Liter 1.8
CC 1780
Engine Size 1.8L/1780cc
Beginning Year 1983
Ending Year 1987
Engine Family Volkswagen 4-cylinder
Application Notes Replacement for original equipment numbers 026107103Q or 027107103O.

Does this look right?

As always, thanks for your help.

[Flyinglizard]

The specs note the dish as .360 deep. I have a pile of pistons. I check the p[istons with pennies in the dish. 3 pennies are 10/1, 5 pennies are 8.5 to one.
It sounds strange but is a good visual.. Measure 3 pennies.
I think that .360 is 8/1 dish.

[Ralf]

Make sure to let us know what you find out about the compression. That price is a steal since it says its a set of four.

[T Broring]

I've been trying to help Dave off line in his search. I have seen three different stock pistons as far as the recess in the top that determines compression. Unfortunately the ones I know to be 10:1 are inside my motor so I cannot measure. These seem to have the most shallow indent on the top. I also have a set of new Mahle pistons that have the deep indent but the diameter of the indent is less than on the 8.5:1 stocks I took out. I think I will have to cc all the different indents in the off season. It is a shame that we never had to do all this work in the past as ordering them was easy. The European manufacturers will sometimes make a batch if there is demand.

[S2_ITBVW]

Thanks, everyone.

Mike, I do not have a stack of pistons to measure. If you have a moment could you check the diameter of the dish on the 8.5:1 and 10:1 pistons. I suspect that the Keith Black pistons are 8.5:1. The depth of the dish on all the KB pistons is over "6 pennies" so I doubt it is going to be 10:1. Thanks very, very much for your help!

I have contacted every domestic resource I can find, including folks I found on eBay. I have talked to several piston manufactures and they all say that the .40 over pistons are not available and that no one wants to pay for a production run because the demand is just not high enough to justify it.



I called Mahle to talk to them about maufacturing the .40 over pistons. The motorsports folks told to me check one last time with the Mahle OEM folks. The Mahle OEM folks told me to talk with the Mahle Europe folks. I talked to the Mahle Europe folks (AmBoss??) and they have sent an inquiry to Europe to find out if there are any .40 pistons laying in warehouse in Germany somewhere.

I'll let you know if they find anything. We are "officially" looking in Europe now.

[Flyinglizard]

The penny sizing is just because of trying to buy pistons online and over the phone before. Most parts salesmen dont have a vernier in their pocket , but may have 4 pennies..
Place 4 pennies on the piston. Drag a ruler across the pennies. If one penny is scrapped off , youhave 10/1 pistons, . If the ruler clears the 4 pennies, you have 8.5/1.
The measured dish is about .182 for the 10/1
The dish is about .348 for the 8/1.
The OD size is very close to the same.
Now, if the car is a MK 2, the 8/1 engine came in the car.
The max compression is 10.5 to 1. Those pistons are legal. The min head thicness is maybe 132.5 mm?
Deck the block about 032. The Felpro gasket is 054 tight,
You should come up with about 10/1. maybe a little under..
Jake, help me out here...
MM

[S2_ITBVW]

The Mahle Europe folks (AmBoss) have located four .40 over cast OEM pistons in the United States and over 100 of the same pistons in Europe. They quoted me a price of $55 per piston. They are emailing me a link to the specs tomorrow. I'll post the link as soon as I get it. They do sell to the public and I will provide the contact information as soon as I confirm that this is what we are all looking for.

Cross your fingers. Thanks for the help.

[Eric Parham]

I've been trying to help Dave off line in his search. I have seen three different stock pistons as far as the recess in the top that determines compression. Unfortunately the ones I know to be 10:1 are inside my motor so I cannot measure. These seem to have the most shallow indent on the top. I also have a set of new Mahle pistons that have the deep indent but the diameter of the indent is less than on the 8.5:1 stocks I took out. I think I will have to cc all the different indents in the off season. It is a shame that we never had to do all this work in the past as ordering them was easy. The European manufacturers will sometimes make a batch if there is demand.

The 10:1 CR 8V pistons have the same diameter dish as the 8.5:1, just shallower. The ones with the smaller diameter but deeper dish are probably 8:1 Corrado G60 pistons (which take 136 mm instead of 144 rods, IIRC).