12 replies to this topic

[firstgencrx]

I know it's completely acceptable to mill the heads on our little cars when they get a little warped. People do it all the time. Even the factory says it's cool. I also know the cam gets a tad out of timing due to the lost height, but an adjustable cam gear can easily fix that.

What I don't get is the camshaft(s) bores are now out of alignment. Do the cams ever stress break or seize from this? Or do the better shops re-align hone the cam saddles after surfacing the head? It would seem to me that the head can only be warped so much before the cam is going to suffer from being bent all the time. I guess a few thou out of alignment is no big deal.

I always wondered about this with overhead cam engines.

David

[DarkHand]

Hmm, I guess it comes down to whether the warping occurs locally at the head/block interface or through the entire head. Never considered it occurring everywhere, but now I can't really see it not happening across the entire head.

[cbstdscott]

I have five years on my shaved head with no issues.

[firstgencrx]

I have five years on my shaved head with no issues.

Ya, but how bent was it before you shaved it?

David

[Madkore]

You can have the cam journals align bored to line them up again.

If not, then you might actually seize the cam or break the cam.

I have seen cams that have seized or snapped before.

MK

[cbstdscott]

Ya, but how bent was it before you shaved it?

David

Oh, well, it wasn't bent. I just wanted higher compression.

[DEIVIONCRX]

I have herd of cams seizing and breaking before, i never attributed it to this tho. But there are many factors, HF, VX, HX cams are hollow and are very prone to breaking. Ive seen a few people with aftermarket cams get ones that the bearing journals are a few thousanths oversized and will sieze and sheer.

Back in votec i had a friend with a older Trooper, that blew a headgasket so our instructor found somebody who would mill it, but insted he just took his and gave him one that was already milled and fixed. The problem was when we bolted it down, the fuel pump push rod siezed in its galley, we pulled that head off 3-4 times trying to clean up the galley for it so it wouldnt stick when it was torqued down, we finaly got it to run after a month or so.

The head was majorly warped and insted of trying to un-warp it then mill it, they just milled it flat.

[firstgencrx]

The head was majorly warped and insted of trying to un-warp it then mill it, they just milled it flat.

You bring up an important idea. It never occurred to me the head could be straightened in a press a bit before surfacing. At least take most of the bend out. Makes sense.

"Just a little bit more, little..... bit..... more..... CRACK! Ops!!!"

Still a good idea.

Take care,

David

[hosmer]

I've had 2 motors overheat on me, 1 EW and 1 D16A6

EW head was machined and ran beautifully for a few more years (still runs last time I heard) and the EF head was junk

my method:
from what I was told (as a lad ) once the head is removed pull the valve springs and see if you can spin the cam with the cam gear still attached by hand
-too much resistance/frozen = find a good core

[NeverEndingNinja]

my car has overheated on me at least 4 times(EW1), and i've never even removed the valve cover since then. still runs like a champ. I guess I really should rebuild the motor, or at least the head.

[rwdcrx]

Could someone please explain to me how shaving the head down misaligns the cam journals. (the bending cam theory) I'm confused. Wouldn't the cam still be aligned just closer to the crank?

[redsautorehab]

Could someone please explain to me how shaving the head down misaligns the cam journals. (the bending cam theory) I'm confused. Wouldn't the cam still be aligned just closer to the crank?

yes, i'm bringing this back from the dead.
it's not the machining that misaligns the cam journals, it's the warping of the head, which necessitates shaving the head.

now, to answer david's original question, better machine shops will check the cam journals, and if they are affected, they will straighten the head, by clamping it down tight, heating it in an oven, and allow it to slowly cool similar to annealing.

now, hondas very rarely require straightening. the only heads that i have ever had to have straightened, are mercedes l6 motors, and the gm 2.2l, which warps the head beyond servicable limits every time the head gasket is blown.



sean

[rwdcrx]

WOW! thats old ^^^^^I don't remember posting that....and my question was answered 360 days ago...but thanks anyway!