Scratches on head face... resurface?

[BARRON]

I had my head in a corner at work and somehow it got rolled over on its face on the floor and moved a bit. This scratched a couple spots. ONE particular scratch spans the across width of the fire ring area of the #1 cyl. The scratch dosent even measure .001" deep.. but I can feel it while running my fingernail over it.

Should I recurface it?
Will the headgasket compensate for this scratch?
What If I use Coppercoat head gasket spray?


I am just concerned ecause this is going to be on a STEEL part of the head gasket.

Input please! I want to put this togather this week!!!



________________________________________
89' 2.5L Caravan 7-passanger "Shortie" ;)
10-12Psi on T2 Garrett
FMIC /w 2.5" I/O - P&P Head
2.5" shraight-thru exhaust

[Warren Stramer]

Could you show a photo?, Maybe I can help. Warren

[turbovanman²]

Usually, if you can catch your finger nail, its too deep to use. I have used a file and JB weld before to fix deep scrathes like that.

[BARRON]

*Sigh*.. ok thanks simon. There is a machine shop at work, I'll try to get my friend Paul to mill .002" off it and see if it cleans it up. I dont want to mill much off a 782.

[shadow88]

Why don't you want to take more than .002 off? I have .015 off mine, been that way for years.

[turbovanman²]

Why don't you want to take more than .002 off? I have .015 off mine, been that way for years.

Because its probably already been milled a few times, and possibly the block also. More compression equals bad, ;)

[Directconnection]

Usually, if you can catch your finger nail, its too deep to use. I have used a file and JB weld before to fix deep scrathes like that.


hahaha....oh wait...you're being serious?

How long did this actually last?


It's really hard to say if it needs resurfacing without seeing it in person and especially no pics.

If this head was freshly resurfaced, it would be a hard guess over the net. If it came off a motor and wasn't resurfeced ever, or even if used for a year or two... then I'd definately have it done.

Last year before I worked at an engine shop, I had one place do my Intrepid's heads. I got them back and the surface was HORRIBLE! I eneded up sanding them by hand. I did not want to tell you this because it is VERY hard to sane something like this flat and not have it be just a couple thousandths off. If you do this...take your darn time. Because I worked at a Machine shop at the time, I had access to precision ground flat stock (Starrett sells it). I had a bar that was as wide as I could find in the stock rack and was about 3-4 " wide. I used a fine sandpaper and douched it in water continuosly to keep it clean and sand nicely. You make slooow and even strokes (hehe..he said strokes)holding the bar at a 45 degree to the stroke you are using. low and even pressure and start with the bar/paper slightly of one end, ending at the other end with the bar/paper just off the other end, bu not too far. Overstroke it. If you go too far, and the pressure you apply stays the same, what is happening is that pressure applied in "x" amount of ft lbs lets say gets distributed over a smaller surface area of the bar/paper. More material gets removed in the ends is what it amounts to. If you don't overstroke, though... then not enough paper travelled acrossed the ends and that will be a high spot. Also, don't exaggerate or apply uneven pressure as that can remove more material on the sides/ends as well.


I basically over-explained this... Smooth, even strokes. Even pressure, overstroke maybe 1/3rd to 1/2 of the bar/paper on both ends but most importantly, make sure the strokes are covering the head's width when you make your passes. The head will need a complete teardown and washing as the aluminum and paper's grit media makes a grey nasty mess that wouldn't be good getting into the engine at all. Wash it with a pressure washer after douching it with alot of brake cleaner.


Or...bring it to a shop to get it resurfaced:thumb:

[turbovanman²]

hahaha....oh wait...you're being serious?

How long did this actually last?




Yeah, I am dead serious. I was porting my old Ninja 600 head and I slipped with the die grinder, took a nice chunk off at the firing ring. JB welded it, sanded it flat and put her together. I rode for 6months then sold it. I assume its still running. This was in the mid 90's, :thumb:

[Tony Hanna]

That's interesting. I've never had any luck with jb weld in high heat applications like that.

[BARRON]

I ran a painters buffer over it with 600 grit pad on it a couple times to see if it would clean up but the scratch is still there.

This is a reman head so no doubt its had about .010" off it already. Plus its been ported and other misc stuff so I kinda want to use it.

So I guess I'll carry it about 10 feet from where it is.. set it on the milling machine and have our super duper machinist with 19 years under his belt, surface it a bit more...

Thanks for all the info guys.

Oh.. thanks simon for getting into the 13's .. now I'll NEVER catch you!! ..unless after I am done lightning this thing... hee hee ho and har. ... yah.
_________________
89' 2.5L Caravan 7-passanger "Shortie" ;)
10-12Psi on T2 Garrett
FMIC /w 2.5" I/O - P&P Head
2.5" shraight-thru exhaust

[mpgmike]

There is a small square tab on the front of the head just forward of the T-stat housing. On the block side, it has a recessed area below the machined surface. I've measured several virgin heads and they all range from 0.085" to 0.087". Using that as a guide I can determine if the head has been milled and by how much by measuring the depth of the recession.

Mike

[Directconnection]

*Sigh*.. ok thanks simon. There is a machine shop at work, I'll try to get my friend Paul to mill .002" off it and see if it cleans it up. I dont want to mill much off a 782.

Make sure if he is using the bridgeport type of a machine that the head is trammed in perfectly or darn close. With such a large cutter radius, if the head is tilted .001, technically, the head's surface will be concave to the tune of .001" or more! Depending on how large of a sweep he uses when indicating in the head. Normally, you need a bias in the head as the leading edge of the cutter's path removes the material, and the trailing edge that is biases .001" takes a super light finish skim cut which promotes the best finish.

[BARRON]

I've measured several virgin heads and they all range from 0.085" to 0.087". Using that as a guide I can determine if the head has been milled and by how much by measuring the depth of the recession.

Mike

I checked the spot you said. Mine measured 0.091". So we machined 0.005" off and it cleaned up beautifully!


Normally, you need a bias in the head as the leading edge of the cutter's path removes the material, and the trailing edge that is biases .001" takes a super light finish skim cut which promotes the best finish.

Directconnection,this all took place exactly as you just described... so this tells me that the machinist knew what he was doing.. and that you know what you are talking about! We used as small of a diameter as we could. It just completely cover the head.

The head turned out awesome!

Thanks a heap all!