Gasket Material and Surface Roughness-and How they Relate 

As a machinist who uses said tools on a daily basis, thanks for posting a real useful video for the novice.

You neglected to mention measuring flat on the diagonal. I have seen heads and blocks that measure flat in length, flat across the head, but have a twist that shows up diagonally.

great video and explination of surface roughness, the only issue i saw with the video is the demenstrator measured the surface of the block's RA, then showed the surface of the head.

I used to work in R&D for a automotive manufacturer and we were having some head gasket issues and we started playing with different RA's on both the head and block stealing surfaces and we actually had the best results from what is normally considered an RA surface that's too rough... the engines coming out of the plant were machined to low to mid 30's in RA but we had the best results with a 55-60 RA while still using the same factory MLS gaskets.... I doubt that you will see this post as old as this video is but if buy chance you do I would love to hear your input on this... because it shouldn't be this way in all of my personal experience but it is.... thoughts? BTW that OEM did adjust the machine program a small amount but not anywhere close to the numbers we found to get the best results..and they are still having HG problems to this day ... I don't work for them still but I do have a passion for the brand still

Explained very well, I did not realise it was such a technical subject. Many Thanks.

Very helpful. I beginning to get this head gasket thing figured out.

What a beautiful lesson.

Really Good, This is very important. And I learned something new

A lot of good information here. I am building a high compression ford 302 with trick flow heads and want the best possible gasket. I also want the same RA number on the deck surface and the head surface. I am old school and perma-torque was always the choice.

So informative...👍👌

As one doing a budget-conscious project, I don't have the means to acquire a profileometer. I know I'm 'cavemanning', but I watched this in the hope of *_seeing_* what a 15-to-20 RA finish looks like in comparison to the rather mirror-like finish I've achieved by old-school sanding. Who the fuck makes this kind of video without even showing the surfaces of the 'finished' head and the 15 RA crank journal? That would have been an effortless edit-in. : /

I know what you're saying but my machine shop uses a fly cutter for MLS gaskets for OE aplications. They don't have a deck grinder and we've never had a head gasket job come back. So OE engine over heats alloy on alloy OE gasket is MLS. We use a scotchbright die grinder pad on the block and get the head fly cut. These cars are day to day run arounds and a full engine build would right the car off so we offer the cheap fix. These cars can see over 100,000km out of the job. So I'm very skeptical about the RA finish values for MLS gaskets. Yes if I was spending 20k on an engine I'll get the head and deck ground to the correct RA for safety factor. But I don't believe it's necessary to finish the blocks to the level stated here. Even the OE just fly cut the block and head then throw a MLS gasket on some TTY bolts and call it a day and most engines will do 300,000+km. I call BS.

Perfect video left nothing out and everything handy in

Really good information, thanks.

at 9:46, a black mouse is visible at the roof of the red car. If is not your pet, the shop can use a resident cat, which would make a great pet. Thanks for the info on the very thin stainless gasket, I'm debating wether to copper spray and reuse a set I have brushed down to metal or just install new composite gaskets.

Doesn't Fel-Pro have a blue rubberized surface finish on their MLS gaskets that accommodates rougher aftermarket finishes??

this is interesting. I get it. what the discussion is not telling you is that an MLS only needs to be super Smooth in the sealing areas. It is possible and not difficult to on an Iron block use only a razor blade and maybe some emery cloth in certain areas to ensure the surface is viable. now the cylinder head would be the same but aluminum is prevalent now and it needs to be resurfaced. I have done this on a BMW s54 block(iron) without any issues at all. Yes in areas the factory surface is obvious after some work, MLS is the standard for this block so it is not time consuming 4-6hours. I spent time, instead of money on the process. But I didn't have to haul the block around to shops and have some body work it, I don't trust almost any services in my area, any. But in general taking all the hardware to a machine shop and saying do this some might reply "the customer is wrong, we always do it this way". One other thing on MLS is that apparently the non crush sealant is Viton, all of that material needs to be blemish free, and carefully inspected. I have had 3 Elring head gaskets with this lately, post CV-19 world.

Which is the best for high compression like racing style? I wanna use nitro and turbo.

It's really difficult finding a machine shop that actually uses a profilometer to check the surface finish. Most, if not all, just do an eye ball check. I absolutely hate that.

As alloy heads expand more than the engine block does that mean the head slides back and forth long ways on the gasket?

That RA gauge is almost $2k Is there a way to use sandpaper as a roughness standard? For example...220 grit = 50 RA

What does a composite head gasket actually consist of? Graphite?

Thank you

nice info thanks buddy

Please post what profilometer you used for reference? Consider listing typical RA ranges by head gasket and links to gasket mfg technical data supporting.

What doesn't add up is a MLS gaskets on rough cut heads and blocks straight from the manufacturers. I'm doing a engine now, 4.6 Ford off a 97 f150 and I could clearly make out the rough machine surfaces of the block and heads. I'll get it down to at least 40RA or where I can't feel anything by much and copper spray both sides of the MLS gasket. I assure you it will be better than it was.

What about copper spray???

Hi. On modern common rail turbo diesels would you advise to spray Hylomar onto gasket prior to installation?..

2:43 “If you take a look here”…..and the camera focuses on the head, he is measuring the block 🙄🙄

You never showed a 60

Not enough can be said for properly measuring and machining the crank, cam, then deck of the block. 🇦🇺🤜🏼🤛🏼🍀😎🤓

Which gasket is better for overheat engine? Block heat stainless steel

what head gasket do you recomend for a sbc cast iron 100ra stock street use?

Hate the Multi Layer Steel Gaskets from Mahle / Victor Reinz....they are so flat, even the original Hemi/Chrysler surface isn't smooth enough and they will begin to leak.

He is measuring the block but the camera is showing the head.

Why are you talking about the block surface and show a 36 head surface

This could have been a much shorter video. It felt like you didn't want to say the numbers.

Which is better Carbon or St eel Cyliner gasket? Need help coz i need buy to replace my blown gasket

Has anyone ever tried using a belt sander and straight edge?

carbon head gasket for better seal ? with additional copper spray better? for proper seal

No mention of sealers?

MLS gasket?

what profilometer your using please send link where I can buy. what brand is good want to use it to make sure piston bore is finished to perfection.

Lol, surface finish. Use good head gaskets and you don't have worry about stupid bullshit. The vehicle needs to work with imperfect tolerances. Like an AK47.

I think he just plain ole & bored that poor little ole mouse right to death in this video... 9:46 little ole black mouse on the roof of the Nova car high tails it out of the video.. ..

ARE COPPER GASKETS ANNEALED? IF NO THEN ALL THAT TALKING MAKES NO SENSE AS NON ANNEALED COPPER GASKET WILL LEAK

Thank you