What ever happened to the idea of peening the pre-cups?

[Dakotakid]

I can remember (about 6 or 7 years ago) (on this forum) that the concept of attempting to "anchor" the pre-cups, in older heads, by multiple peening marks......was all the rage. I mean there used to be photo after photo of this "black art."

It was right up there with Frisbees, Hula-hoops, and Ford Pintos. I mean to tell you, it was the "default" answer for everything from dead batteries to ash trays that needed emptying.

Then, all of a sudden it was like Bill Clinton.

When did this "technique" fall out of favor? I ask because of the one guy who was ether-ing his Parts Place head and going to run it.

[theman53]

I gave up on it as I peened mine and a cup still fell out.

[libbydiesel]

I believe that the cracks are more of an issue.  If a pre-cup is solidly peened in place but cracks in half it will destroy the engine.  At this point I thoroughly inspect every pre-cup before install and replace any that have even micro-cracks.  That said, if a pre-cup is not tight in the bore it can wiggle and destroy head gasket, pre-cup bore and top of piston (I've seen it more than once).  If any precup is loose in its bore, I will peen to make it fit tightly.  At this point I also believe that having the precup protrude above the head so it is pinched tightly by the head gasket.

[745 turbogreasel]

.  At this point I also believe that having the precup protrude above the head so it is pinched tightly by the head gasket.

I  am on this bandwagon as well.  I also think  using a cutter to surface the head with them in eggs the  precup bore.

[theman53]

To add, 1 fell out the other 3 of mine could move in and out of their bores with just finger nail grabbing onto them. Heat and time or ether heat and no time is really bad for them.

[vanbcguy]

Large part of why I went M-TDI....

[libbydiesel]

The absence of pre-cups is a big plus.  I also like the 15% better fuel economy.

[RabbitJockey]

is it really a 15% difference in fuel economy? i always read 10-15% better engine efficiency, but thats before all the accessories and the drive line and aeodynamics.

[libbydiesel]

I dunno.  It's at least 10%.  I've never driven the same car with both engines at the same acceleration rates.   

[vanbcguy]

I'm definitely getting quite a bit better economy with mine. Went from a 1.6 TD to an M-TDI. Last highway trip I did was 5.2l/100km, same trip on the same road at the same speeds with the same car used to be more like 6.5l/100km.

[libbydiesel]

Yes, I know I have gotten at least 10% better fuel economy but I also know that I haven't run a tank where I haven't accelerated a lot faster at least a few times, so I'm not sure what the actual % is if you do the same acceleration rates.  It's kinda fun to think that my mTDI vanagons consume the same amount of fuel as a 1.6 non-turbo vanagon which was probably the slowest production vehicle in the last 50 years...  I think I could probably tow a second vanagon with mine and still accelerate faster and have a better top speed.   

[RabbitJockey]

Yes, I know I have gotten at least 10% better fuel economy but I also know that I haven't run a tank where I haven't accelerated a lot faster at least a few times, so I'm not sure what the actual % is if you do the same acceleration rates.  It's kinda fun to think that my mTDI vanagons consume the same amount of fuel as a 1.6 non-turbo vanagon which was probably the slowest production vehicle in the last 50 years...  I think I could probably tow a second vanagon with mine and still accelerate faster and have a better top speed.   

i can't believe they ever sold them like that.

[RabbitJockey]

Yes, I know I have gotten at least 10% better fuel economy but I also know that I haven't run a tank where I haven't accelerated a lot faster at least a few times, so I'm not sure what the actual % is if you do the same acceleration rates.  It's kinda fun to think that my mTDI vanagons consume the same amount of fuel as a 1.6 non-turbo vanagon which was probably the slowest production vehicle in the last 50 years...  I think I could probably tow a second vanagon with mine and still accelerate faster and have a better top speed.   

i can't believe they ever sold them like that.

  i guess 10-15% isn't that crazy of a difference either, say in a jetta u get 45mpg with a 1.6td, with a tdi u should get 50-53