Author Topic: Should I Resurface Head? (Read 3860 times)

cj8990 · « **on:** June 04, 2016, 05:28:14 PM »

These scratches make me wonder if I should drop the head off for a resurface?

The scratches in pic 2 can be felt with a fingernail. Pic 3's scratches can't.. it just feels slightly rough.

If I do resurface what kind of consequences are there (i.e. A/F ratio, piston-valve clearance, serviceable limits, anything like this)?

-Corey

chewbacca5000 · « **Reply #1 on:** June 04, 2016, 05:49:19 PM »

It looks like that head had been modified. Can you put a head gasket on it and snap a picture. What displacement are you going for?

cj8990 · « **Reply #2 on:** June 04, 2016, 06:42:22 PM »

Here is the picture with the head gasket. How would the head have been modified? By what displacement do you mean what bore and piston am I running? If so these are factory pistons no oversize.. 58.47 - 58.49 mm.

-Corey

754 · « **Reply #3 on:** June 04, 2016, 07:48:51 PM »

That head has been opened up for bigger than stock bores, that head gasket wont work .
The scratched look bad, but if its flat you may be able to bead blast the gasket surface to give it a bit of tooth.. ot take a very light cut.

Is it a 75 or 76 F head ?

cj8990 · « **Reply #4 on:** June 04, 2016, 08:04:30 PM »

The head is off a 76 550 K I got last summer. How can you tell it's been opened up? I wasn't aware the head had to be opened up when using factory oversized pistons/bores or is that just for one of the aftermarket oversize pistons that increase displacement?

The bores/piston it came off of are def stock sizing as I measured them myself. So what has the previous idiot done? Put a head modified for aftermarket oversized pistons (the 650cc ones or whatever they are) on a factory lower half?

-Corey

---Edit---

Also if it is opened up, what does this mean? What needs to be opened up on a head to accommodate oversize pistons?

BTW.. thanks for they help both you guys

kmb69 · « **Reply #5 on:** June 04, 2016, 08:04:44 PM »

Quote from: 754 on June 04, 2016, 07:48:51 PM

That head has been opened up for bigger than stock bores, that head gasket wont work .
The scratched look bad, but if its flat you may be able to bead blast the gasket surface to give it a bit of tooth.. ot take a very light cut.

Is it a 75 or 76 F head ?

Frank, Pretty sure all 550's, K's and F's use the same head: 12200-374-000.
Looks stock to me.

754 · « **Reply #6 on:** June 04, 2016, 09:55:16 PM »

Ok, I thought it was a 750 head, not familiar with the 500/550. I noticed the band around the periphery of the opening at about a 15 deg angle. I noticed it because it had a chattery appearance on the cut... which did not look factory.
Then when I looked at headgasket pic it appeared it was hanging over and shrouding that bevel cut.. back to look at the pic.

I went back and looked, i had looked at 2nd chamber from the right and it appeared to overhang, but the left two clearly look like all is OK, sorry for misleading in the wrong direction...

Lostboy Steve · « **Reply #7 on:** June 05, 2016, 05:47:34 AM »

I think I was cautioned against milling the head from my machine shop. (I may have done it anyway.) If its straight, with a straight edge, you could leave it and just use a graphite type headgasket.

Or (at your own risk) you could so it this way:

Lostboy Steve · « **Reply #8 on:** June 05, 2016, 06:24:11 AM »

Honestly, I don't remember. Maybe because my head was pretty clean and straight. Could have been the old don't fix something that isnt broken.

754 · « **Reply #9 on:** June 05, 2016, 08:06:25 AM »

A lot of shop wil cut at least 10 to start , more if they think they need it..

drumstyx · « **Reply #10 on:** June 05, 2016, 10:05:44 AM »

I'm a noob in this regard, but can someone explain why scratches like that are bad? There's a vast gasket surface area, is a gouge really going to make a difference?

BomberMann650 · « **Reply #11 on:** June 05, 2016, 10:29:38 AM »

Quote from: lostboy on June 05, 2016, 05:47:34 AM

I think I was cautioned against milling the head from my machine shop. (I may have done it anyway.) If its straight, with a straight edge, you could leave it and just use a graphite type headgasket.

Or (at your own risk) you could so it this way:

That went surprisingly well

PeWe · « **Reply #12 on:** June 05, 2016, 11:36:22 AM »

Improve head surface on the kitchen table.
I started with grit 400 but changed to 280 when there were rather deep scratches, ended up fine surface with grit 400 when the deep marks were gone.
I used 2 glued and taped on a piece of thick board I had clamped to the kitchen table.

I had to watch out for the paper damage when getting tired. Water on paper and move the head on the surface in different directions make a flat surface. This works on correct surfaces, scratched only. Correct the entire angle will be another thing.

I'll look for longer grinding paper for next job. One long piece of 1000x 500 mm would be fine.

cj8990 · « **Reply #13 on:** June 05, 2016, 07:45:50 PM »

754 - No problem.. I should have mentioned this was a 550...

I'm going to stop by the machine shop tomorrow morning and see how much they think they'd have to take off. I guess the consensus is it would be stupid to not have it machine if it was just a few thousandths, right? As for the dowel pins.. they aren't removable are they? I have to bring both the jugs and head in to get them machined (as of now one dowel is in the head and one is in the jugs)?

-Corey

OldSchool_IsCool · « **Reply #14 on:** June 05, 2016, 08:28:24 PM »

I do something similar, PeWe, but in stead of trusting wood to not bow, I use a slab of marble tile from the home improvement store. Use a marker to color the surface and you'll see how evenly your cut is.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #15 on:** June 05, 2016, 09:52:01 PM »

The dowels are removable albeit often times not very easily.

754 · « **Reply #16 on:** June 05, 2016, 11:10:13 PM »

A lot of guys use a level to set it up, quick but a 4 thou cut may not clean it up.
I have set up HD heads on a swivel fixture, and clock them in with a dial indicator and shims, takes time, and I try to take least amount off..
but the big question is where do you start ? any edge? if that one section is high or low .. changes everything.
I take skim cuts til it is averaging, ie cutting three corners, or 3 places in a circle, relatively even... then zero the machine.
if you touch off on an ends.. say, it may be 4 thou lower than the sides... so a 10 thou cut is more like 14 , all of a sudden.

As one engine shop owner put it to me.. I had asked how they take least amount. he says we take a cut , usually 10 thou.. 50 dollars for a pass across a head. I said so if ten thou wont clean it do youjust take another 10 thou, no charge.. He said no, each pass = 50.00

Garage_guy_chris · « **Reply #17 on:** June 06, 2016, 12:40:50 AM »

I just had a set of Subaru heads come back from the machinist and they always try to take off as little as possible, this time they managed to clean them up with a 0.004" - 0.005" cut. Last time I had a CB450 head done and same thing about a 0.005" cut. The guy i use is fantastic generally about $60 for a resurface, payed $120 for the Subie heads as there are 2...

The other thing is heads generally have a service limit for how much can be machined you can use that up in 1 big cut or a bunch of smaller ones. On my Subaru I *think* its 0.010" so i have used half of that so in theory I could machine them again if it ever needs head gaskets again..... I don't know if our Honda's have a service limit for this or not but it is something to consider.

I have also seen this "sand paper" method many times. I have used it on smaller less expensive parts thermostat housings, water necks, stuff like that and it works great. For me I went to a granite counter top place and picked up a nice thick 1 inch slab of granite about 18 x 24 inches. It was a cut out of a counter for a kitchen sink. i think i payed $10 for it.

Now my big concern for this method is how true is the board, wood, glass, tile, whatever you are using? If it has high spots or a warp or can flex it can transfer the irregularities to the part being lapped. A perfect example I saw was a guy doing a 4 cyl car cylinder head of a piece of about 3/16" window glass on a old picnic table. I can just see that glass flexing and screwing up his lapping job on such a big part. Too little support too much weight.

Lostboy Steve · « **Reply #18 on:** June 06, 2016, 05:17:59 AM »

Quote from: PeWe on June 05, 2016, 11:36:22 AM

Improve head surface on the kitchen table.
I started with grit 400 but changed to 280 when there were rather deep scratches, ended up fine surface with grit 400 when the deep marks were gone.
I used 2 glued and taped on a piece of thick board I had clamped to the kitchen table.

I had to watch out for the paper damage when getting tired. Water on paper and move the head on the surface in different directions make a flat surface. This works on correct surfaces, scratched only. Correct the entire angle will be another thing.

I'll look for longer grinding paper for next job. One long piece of 1000x 500 mm would be fine.

Damn, you must be hanging out with the dude in the video! I don't see why this method isn't used more. Again, I would use a piece of level granite.

cj8990 · « **Reply #19 on:** June 09, 2016, 07:58:14 PM »

In case anyone's curious/it helps someone in the future..

$98 and they removed .007"

-Corey

rhackney · « **Reply #20 on:** June 10, 2016, 09:00:15 AM »

I had seen on here that someone used a large piece of glass on a flat surface with some lapping compound spread about.
They then took the head, laid the side that they wished to resurface and moved in a figure eight pattern for a while until the plane was level and clean looking.

Your wet-dry paper approach looks like the same method with a different media.

Looking good man!

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Author Topic: Should I Resurface Head? (Read 3860 times)