Head carnage

surfcam · Post by **surfcam** » Sat Feb 02, 2008 1:37 pm

I'm in the camp that thinks the cam journals will warp with the head. I've worked on warped pumps and everything seems to move with the flat surface of a split case of a pump. The bolt holes that hold the seal in the bearing journals all move with the face. Line boring the cam journal can only help as far as stress on the head. But when you take a cut off the bearing caps before boring you will be looking for smaller valve shims. I can sure see the problems with resurfacing a head being in evolved with doing the same thing to pumps. The only thing that I see that might help is more teeth on the cutter and a slower feed. Oh yea more cost.

Asymtave · Post by **Asymtave** » Sat Feb 02, 2008 3:30 pm

I didn't get out the feeler gauges but a staight edge placed across the journals showed they were significantly out of line. Looked like about 10 thou to me. Sometimes I can hear the cam "squeak" at idle, but as soon as it's revved a little bit this goes away.

CoolAirVw · Post by **CoolAirVw** » Sat Feb 02, 2008 4:22 pm

bertcarrier wrote:Is there any chance that a bad injector (dribbling, peeing) could have caused that? I had one go bad that burned the chamber completely out.

Maybe its still possible but the nozzles were replaced with new at the rebuild.

myke_w · Post by **myke_w** » Mon Feb 04, 2008 11:11 pm

I rebuild quite a few of these motors and I'd say about 50% of them need some head surfacing.. I'd guess I have at least 20 cars out there running around with shaved heads on them that are in good condition and in daily service.. and believe me I'd know right away if there were a problem too

Obviously the Bentley says not to mill, but I've personally had good results. I think there definitely is max mill depth for the heads to be observed for several reasons. I'd agree that if you could remove the pre-cups and machine them, that would be best, but considering I've found only one machine shop that will even touch my diesel heads, It's a long shot.
I'd really like to see a pic of the peened precups.

vwtyp133 · Post by **vwtyp133** » Wed Feb 06, 2008 11:13 pm

There was one place around here that used a stone grinder to surface my VW diesel heads. It never caught or lifted a swirl chamber puck the way a mill can. IMO maybe the cutter feed was going a bit too fast, ie. taking bigger bites. Feeding just a little slower seems to work better.

J.R.

libbybapa · Post by **libbybapa** » Tue Feb 12, 2008 10:49 pm

myke_w wrote:I'd really like to see a pic of the peened precups.

Ask and It Is Given.

Cheers.
Andrew

woodrat · Post by **woodrat** » Wed Feb 13, 2008 1:47 am

aha!

Thanks. I will do that to my head before it goes on for sure.

Post by **Fatmobile** » Wed Feb 13, 2008 2:16 am

I haven't taken a picture of the peens around the prechambers yet.
Around here they put 5 peens all the way around it,... none near the cylinder ring.

woodrat · Post by **woodrat** » Wed Feb 13, 2008 2:59 am

So by not near the cylinder ring, you mean not where the edge of the cylinder hole in the gasket touches the head? So I'm thinking that if I were to lay the gasket on there and draw the circles with a sharpie and then make sure not to put peen marks on that line, that's what you are talking about?

thx!

libbybapa · Post by **libbybapa** » Wed Feb 13, 2008 9:20 am

Yes, you don't want to compromise the head gasket seal.

The pre-chambers cannot fall toward the outside of the cylinder and so peening there will not do harm, but I do not see how it can accomplish anything. Also, bear in mind that the above picture was taken after the head was shaved. I imagine the peens were larger prior to the shave.

Andrew

Post by **Fatmobile** » Thu Feb 14, 2008 12:45 am

I think peening on all sides of the prechamber would help hold it in, not because it would hold the PC up on that side but because it would provide more pressure on the sides of the prechamber pinching it in place.

libbybapa · Post by **libbybapa** » Thu Feb 14, 2008 9:33 am

I think as long as the actual headgasket sealing area is respected, then peening all the way around would not hurt anything and might be helpful as you say. I will likely adopt that as policy.

Andrew

Post by **Fatmobile** » Fri Feb 22, 2008 4:01 am

My new peen pic:

I notice he also took the sharp edge off the PC outlet.

CoolAirVw · Post by **CoolAirVw** » Mon Mar 17, 2008 3:25 pm

I have further pics of the head repairs on my Jetta.

This is not a bash the machine shop thread. I canâ€™t decide if I want to bash the machine shop or not. If I do Iâ€™ll probably do it in this thread later.

I returned to the machine shop that rebuilt the head. After some ridiculous â€œbanterâ€

Post by **Fatmobile** » Tue Mar 18, 2008 12:45 am

While you have the head off it's a good time to mention I've seen peen marks around the valve seats too.... on that little angled section below the head surface.
You're going to smooth those peens right?
Thay are usually done before they get surfaced so are flat when the head meets the gasket.