Author Topic: Cyl head surface/ finish? (Read 4179 times)

foxracer1 · « **on:** February 21, 2007, 05:44:24 pm »

What kind of finish should be on the head? A friend of mine took his gasser head to a shop who puts a rough/coarse finish on them. My friend went through quite a few head gaskets, scratching his head (pun intended :lol: ) Thought his prcedure of installing them or his heads studs were to blame. On the most recent time he had them put a glass smooth finish on it. So far no probs. But he is building his first TD nd i have told him we are going to run 20psi but his is worried about the head gasket holding up. He said he dosen't want to run any more than 15psi.

-So with a 1.9 metal head gasket what is the best surface? Or at least what have you used or what works.

Also they didn't remove the pre combustion chambers just milled them with the head. Should those be remove?

Thanks for the help guys.

myke_w · « **Reply #1 on:** February 22, 2007, 05:30:34 am »

I use a shop that cuts heads with the prechambers installed, they leave a very smooth finish on it. If a place is turning out rough surfaces, their equipment is either junk, or someone doesn't know what they are doing.
Could you get us a pic of a head that this shop turned out?

jtanguay · « **Reply #2 on:** February 22, 2007, 08:56:40 am »

couldn't a nice cross hatch be ok for a cyl head??? seems as though it might hold pressures a little bit better kind of like inside the cylinder... of course the proper cross hatch would be extremely hard to produce on a cyl head...

to me, a really smooth finish is just what pressure needs to seep out... no crevisses for it to be trapped.

bert · « **Reply #3 on:** February 22, 2007, 12:53:18 pm »

Smoother the better for a gas seal,my heads when returned are like glass.
Bert

BruceM31 · « **Reply #4 on:** February 23, 2007, 01:25:44 pm »

i work at a carquest with a large machine shop in wisconsin and i asked our machinist who does the head resurfacing and he says the same. The smoother the better, after the head is milled a final pass should be made very slowly to smooth it out.

jtanguay · « **Reply #5 on:** February 24, 2007, 06:25:09 am »

yea a very nice smooth finish is great, but wouldn't a nice cross hatch into that smooth surface help out? no matter what, its impossible to get metal 100% smooth anyways...

clbanman · « **Reply #6 on:** February 24, 2007, 06:29:35 am »

You can grip a flat steel plate better between the palms of both hands than between one finger on each hand. The rougher the surface, the fewer contact points you have, resulting in lower clamping force. Unless your head gasket is soft enough to compress to the point that you get full contact across the rough surface, you will reduce your total clamping force.

foxracer1 · « **Reply #7 on:** February 24, 2007, 09:49:17 am »

Well the last head came back smooth as glass cause thats what he told them he wanted. Before they were rough and he put three headgaskets in under a year! His brothers car just blew one and ruined the head, it also was surfaced there.

I don't have any pics if i get a chance i'll try but the only head left with that surface is the one that just got destroyed.

So a smooth surface is good with the 1.9 metal gasket?

jtanguay · « **Reply #8 on:** February 24, 2007, 09:52:25 am »

hmmm well smooth finish & then fire ringing :twisted: i can't wait to see how andy2's engine does after he gets his fire ringed!!!

myke_w · « **Reply #9 on:** February 24, 2007, 05:48:31 pm »

They come from the factory smooth, and don't blow headgaskets unless something goes wrong or mileage is really high, so IMHO, smooth is best.
Blowing 3 head gaskets in a year is unacceptable unless you are a fuel junkie like some of the ballsier folks around here..

macsdub · « **Reply #10 on:** February 25, 2007, 01:00:55 pm »

um,you may disapprove
but when i did my tdi head,all i used was liquid gasket remover+a sharpened popsicle stick for the stubborn stuff
then i used 1000 grit sandpaper+wd 40 on a palm sander
:shock: :shock: :shock:
it came out so nice,it still had the original "rainbow" shine to the head surface
say it doesnt work+ill say i havent blown a head gasket yet boosting it to 40 psi for over a year now
:wink:

burn_your_money · « **Reply #11 on:** February 25, 2007, 02:23:14 pm »

that's what I did last time... probably would have worked if the head wasn't warped :evil:

janb · « **Reply #12 on:** February 25, 2007, 07:26:49 pm »

there was a picture posted on this site a year ago, or so... of a finished head from these guys http://www.aluminumheads.com/ - they use 'ceramic' inserts on face mill for VW-d's with prechambers installed

It should be very smooth and have a'rainbow colored' refraction on aluminum surface. (we're talking 'reflective' !!) a rough rule for the grunt shop... is if you can snag a finger nail, it is way too rough.

smooth is quite important with high diesel compression + vw leak issues... + aluminum head on a Cast block... Especially important with a metal gasket I use a very light spray of 'copper coat' also.

foxracer1 · « **Reply #13 on:** February 26, 2007, 03:15:48 pm »

The one that he was blowing headgaskets on was his 1.8 gas. And i'm tellin him to run some boost but hes to scared hell blow headgaskets and/or melt pistons. I told him 20-24psi should be good and that fuel melts pistons not air.