Project Big Blue

Garbage_Mechan · Mar 24, 2020

Booyah45828 said:
Looks normal to me. Looks like it was a skim cut done on a head resurfacing machine. That machine is technically nothing more then a 12"+ dual insert fly cutter. Being that it was a skim cut and is a picture I'd say is what's throwing some off.

He can check the surface finish Ra if he'd like, but I'd say it's fine for the gaskets he's using. If it was an mls gasket then you'd be looking for something really smooth, but it's not.

Booyah I know Ra is quoted on head specs and is a surface finish quality measurement could you explain how it is measured?

ifrythings · Mar 24, 2020

A few weeks back I watch this video from FTE member TooMnayToys that explains a lot about Ra and required surface finish

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Booyah45828 · Mar 24, 2020

Garbage_Mechan said:
Booyah I know Ra is quoted on head specs and is a surface finish quality measurement could you explain how it is measured?

With a tool called a profilometer. It basically drags a stylus across the surface and calculates the Ra based off the movement of the stylus.

Booyah45828 · Mar 24, 2020

As far as walking away from a machine shop that doesn't have one, I don't know if I'd do that. A good machinist can get the right surface finish without needing a profilometer. It's nice to have one to get an exact number, but when you're working in a 20-30 window, a good machinist with sharp tooling can get there without worry.

To be honest, I've seen more issues with flatness causing head gaskets not to seal then incorrect surface finish.

IDIBRONCO · Mar 24, 2020

nelstomlinson said:
Yes, I think that's what he was getting at. He's not set up to handle the pre-chambers, so he won't try to mill IDI heads.

I've run into this before too.

Garbage_Mechan · Mar 24, 2020

On the RMS I had some engines back in the 80’s that were very sensitive to head surface finish. Had to run pure graphite head gaskets on a very smooth surface.

On the IDI head surfacing I have ran into the issue with the precuts being hard. The shop that used to do mine used an actual surface grinder. He was very careful to be sure the precups were tight....if one came out while grinding it would likely explode the wheel (and destroy the head)

Thewespaul · Mar 24, 2020

Far from horrible, with a head surfacing machine unless you change to a brand new insert every time you go over a prechamber you’re just going to have visible marks where the cutter passed over the inconel and back into the cylinder head and they aren’t noticeable to the touch on the surface, just visible on the surface. These aren’t mls gaskets and aluminum heads that require a mirror finish for sealing, what’s most important is the flatness, the surface finish can be cleaned up with lapping stones and prep tools which I did for good measure, on top of the copper coat to seal any imperfections with the block surface and 150 ft lbs on the studs, shouldn’t ever, ever have to come apart again
:Thumbs Up

Thewespaul · Mar 25, 2020

Well she’s a runner, just did a first fire and it lit off pretty easy. Did my compression check while priming everything and actually picked up some compression on most cylinders with having the heads shaved, with my highest now just being shy of 500 psi. Getting the accessories and intercooler kit in tonight for a first drive in the morning!

IDIBRONCO · Mar 25, 2020

So will you be able to get it on the dyno with the quarantine?

Thewespaul · Mar 25, 2020

Unless things change I can still get it run at truck source diesel where the truck was originally ran stock since the city considers them an essential business and still allows their employees to travel. Engine is coming along, hooking up the exhaust and setting the rad in now.