Hks stopper headgasket

[splitzhail89]

Hello, just needing to know if block and head surfaces need to be lapped with lapping compound to use this headgasket. My block and head surfaces have been machined, about .3 millimeters off of each, and are flat, but is it enough to use the stopper without a problem?

 

[jdub]

The HKS Stopper requires a surface RA of 30 at minimum...most machine shops cannot achieve that level of smoothness. You took a total of .3mm off each...what thickness is is the Stopper MHG?

 

[splitzhail89]

Alright, just talked to my machine shop, they took a total of .3mm off surfaces, so .15mm per each, and im using a 2mm headgasket. The RA is was set to 36 which is as low as they could go. So what am i going to have to do to achieve that RA level. Thanks for the info.

 

[JustAnotherVictim]

Out of blatant curiosity what does RA stand for?
I know what it means but the acronym escapes me.

 

[jdub]

That is actually pretty good for a machine shop
I would lap it or have them do it...shouldn't take much...36 RA is darn close.

You would need a 1.7mm MHG to keep the stock compression. Your 2mm Stopper should be fine...you will lose a small amount of cylinder compression, but you can make that up with boost :evil2:

 

[jdub]

Out of blatant curiosity what does RA stand for?
I know what it means but the acronym escapes me.

RA - Roughness Average. It's expressed in units of height. In English measurement, RA is typically expressed in "millionths of an inch". In the metric system, RA is typically expressed as "millionths of a meter"..."micrometers" or "microns".

 

[JustAnotherVictim]

Ok that clears that up.
I kept searching for RA and kept coming up and electronic references.
Thanks.

 

[splitzhail89]

Thanks for the info jdub. Now i just need to know where to find a lapping tool big enough to go over the head surface. And would you lap both block and head surfaces. Once again thanks for the info.

 

[Alister_Rizen]

Just wonderin'.

What kind of RA can you get away with on the Cometic HG??

((On Topic)) I remember seeing a little while back that someone had made a handheld lapping tool. I don't know if it actually saw the light of production.

Sorry couldn't more.

_Ian

 

[jdub]

Thanks for the info jdub. Now i just need to know where to find a lapping tool big enough to go over the head surface. And would you lap both block and head surfaces. Once again thanks for the info.

You're welcome :icon_bigg

Can't help with the tool...machine shop did mine. And yes, you want to do both the head and block. Do a search for post by me "jdub" with "MHG" and "ARP" and you'll find a ton of info

Just wonderin'.

What kind of RA can you get away with on the Cometic HG??

((On Topic)) I remember seeing a little while back that someone had made a handheld lapping tool. I don't know if it actually saw the light of production.

Sorry couldn't more.

_Ian

The Cometic spec is 50 RA...that's why you hear it's "more forgiving". In reality the spec is just a bit higher than a HKS.

 

[JustAnotherVictim]

I would still get the RA as low as possible even with a cometic.

 

[starscream5000]

Flatter is better with a MHG guys .

 

[Alister_Rizen]

So if I went with an HKS RA but used a Cometic, i'd be sweet??

Good to know.

_Ian

 

[jdub]

So if I went with an HKS RA but used a Cometic, i'd be sweet??

Good to know.

_Ian

Oh yes...like JAV said above, the smoother the better. The RA specs are max requirements

 

[IHI-RHC7]

Great info J.
I got sick and tired of dealing with machine shop boch jobs, so I got one of Reg's lapping tools and I've been doing them my self with great results. I still suggest going with copper coat on each side of the gasket prior to assembly. I also highly suggest a retorque after the first couple times the engine sees a heavy load such as dyno, quarter mile, etc...

 

[Mr.PFloyd]

Great info J.
I got sick and tired of dealing with machine shop boch jobs, so I got one of Reg's lapping tools and I've been doing them my self with great results. I still suggest going with copper coat on each side of the gasket prior to assembly. I also highly suggest a retorque after the first couple times the engine sees a heavy load such as dyno, quarter mile, etc...

how are you positive that your lapping tool gets good ra?

 

[IHI-RHC7]

I compare the surface of the block to that of a nearby babies arse, and as we all know, it doesn't get any smoother than a babies butt. But seriously, the finished product is ridiculously smooth when we get done! The local machine shop has an RA gauge and Reg's lapping tool makes the deck far smoother than things that they have linished to under 40 RA at their shop.

That, and the fact that the lapping tool is sold for the sole purpose of making things smooth enough for a mhg and Reg made it, so it has to be good enough.

 

[Mr.PFloyd]

where can i get one? i need it. did you use this on your head as well?

 

[Alister_Rizen]

Would the same place that machines the head have a lapping tool??

I'd like to get mine lapped, but would it be cheaper to get the tool and do it myself or have someone else do it??

_Ian

 

[IHI-RHC7]

The tool was made by Reg Reimer back in the mid-late 90's.
It was made specifically for removing machine marks from 7m blocks and heads to achieve an Ra of less than 30. in most cases, the Ra is closer to 10. I had to search high and low to find one, but there is a guy on here that owns one and is willing to rent it out. If you search for "lapping tool" you should be able to locate him.
I use them on the head if it needs it. My machines linishes heads, so there are no machine marks to remove. A linisher is basically a huge belt sander turned upside-down and light objects, manifolds, heads, etc... get a quick visit to the linisher after being machined so I don't have to lap them.
Most machine shops laugh at you if you ask them about lapping. Some older shops have lapping tables, but it typically takes about 4 hours to lap a block, and at $65-85 per hour for shop time, that gets spendy. That said, it is cheaper to get the tool yourself, but they are VERY hard to find these days.
-Jake