So you want to build your engine… Well, here’s how to do it.

**Van Black** · 12-18-2018 04:06 AM

Originally Posted by aluthman

He’s asking about the old crowned pistons (05.5-06) vs the newer flat top pistons (07-08). Not sure the 1.8 piston data is useful here.

I know the older ones might not help in regards to the new dish ones. But maybe someone else might find info on the dish ones and compare it with the crown info I have

**aluthman** · 12-18-2018 05:28 PM

Originally Posted by aluthman

This is all a contingency plan if I'm still burning oil after getting my head back from the machine shop. I'm going to do a stock piston build on my spare block. I will be using drop in rods and I already have a crank that *should* be useable. Here is why I want these pistons specifically:

These are the two types of 2.0T FSI pistons, AFAIK. The one on the right was what came out of my BPG engine when I built it. The one on the left came out of a '07 BPY engine in a GLI. The BPG had a higher compression ratio 10.5:1 vs 10.3:1, but the biggest difference between the two is this:

Notice the casting lines in the dished BPY piston. The BPG pistons doesn't have these, meaning that, you guessed it, the BPY pistons are cast and the BPG pistons are forged. This is why I'm specifically looking for the crowned pistons.

I believe this guy ^

**FatMongo** · 02-08-2020 09:06 AM

Phenomenal thread - shitty photobucket. Any chance the images can be resurrected? This thread is absolute gold.

**aluthman** · 02-08-2020 09:50 AM

Now that photobucket got smart and decided to be realistic with pricing, I got a paid account. The images should be restored soon.

Edit: Images are back.

**FatMongo** · 02-08-2020 02:06 PM

Originally Posted by aluthman

Now that photobucket got smart and decided to be realistic with pricing, I got a paid account. The images should be restored soon.

Edit: Images are back.

Awesome - thank you a million!

**FatMongo** · 03-08-2020 03:17 PM

Adam,

I think Im going to refer to this thread ALOT over the next few weeks/months...

As I posted in my other thread...

Had a day off from work on Friday, swung by the local junkyard as they had just gotten in an 2007 A4 2.0, but that engine turned out to look like trash. Went to another junkyard where i had seen a decent looking BPY in a Jetta a few weeks back, but that engine had been snagged. As i was getting ready to leave the yard, i saw a 2007 passat wagon that had come in around the same time as the jetta. Well, the passat looked clean, looked like it had been totalled out because of a minor fender bender (air bag was deployed). The engine looked ok from the outside and turned over pretty smooth. The kicker was because it was FWD, it was almost too easy to pull - so even though it was a high mileage motor - at least 175K, it looked like it was decent candidate and for $270, it was hard not to take a gamble on it. And here she is:

**aluthman** · 03-08-2020 04:51 PM

Good snag. Let me know if you have any questions.

**FatMongo** · 05-01-2020 12:55 PM

Originally Posted by aluthman

I believe this guy ^

Adam,

I'm wondering about the BPG vs. BPY piston. The BPY piston is flatter and the BPG has a 'gulley'. In my mind, it would stand to reason that the BPY piston would have higher compression because it is flatter and there is just that few cc's less area in the cylinder for the combustion to take place. Yet, you state, the dished BPG piston engine has a higher compression ration (10.5 vs. 10.3). Im not understand why the flatter topped piston has less compression in the same block and head.

**aluthman** · 05-01-2020 03:00 PM

Because the crowns on the BPG pistons stick out above the deck of the block at TDC. This means that they take up space in the combustion chamber of the head and compress everything that much further.

**FatMongo** · 05-01-2020 06:18 PM

Originally Posted by aluthman

Because the crowns on the BPG pistons stick out above the deck of the block at TDC. This means that they take up space in the combustion chamber of the head and compress everything that much further.

Oh duh. That makes perfect sense! Thank you.

**FatMongo** · 05-21-2020 05:24 PM

Damn it! I think Photobucket is screwing with us again. Adam, is there anyway I can get your Word document with the images for post #74 emailed to me if you still have it? I will PM you my email address.

Thanks!!!

**aluthman** · 05-23-2020 10:54 AM

The pictures are all still showing for me. What’s wrong with them on your end?

**Yogibara** · 02-23-2021 03:13 PM

Necro-bumping so I can find it in the Audizine app.

I just reinstalled the crank today. Using this to reference the piston rings install now. Cheers.