Hs50 high compression copper head gasket

#1
Does anyone know the thickness of the old high performance copper head gaskets for Hs40s back in the day? The ones that increased compression.
I am looking for something similar for some upcoming hs50(and hs40)builds.
 

cfh

Well-Known Member
#3
They say copper is really bad for a head gasket. I believe Eric Adams was the one that was talking about that on his video cast. I think it would be just better to mill the head - I would go that route
 

delray

Well-Known Member
#4
here you go oldcarcbx. I did little micing out some old use gaskets. the hs-40 mic out at .054 and the hs-50 mic at .076
copper gaskets unlimited makes a .042
I personally never use a copper gasket on anything and I've never heard anything bad on copper gaskets. maybe this eric adams could explain in more detail? the down fall of milling more off the head could make it much easier to warp it? for example if the factory gasket mic out at .076 and the copper was at .042. that would be a .034 difference to achieve the same compression. .034 material on a little flathead Tecumseh to me is a lot material.
now couple things I have see in the gokart world of racing when it comes to copper head gaskets. I have seen them all use a sealer of some kind. the two big ones that I see that keep popping up are a very thin coat of Toyota gasket sealer 103 or couple light coats of copper spray gasket. I also have seen them scuff up the surface of the copper with a scotch-brite before applying the sealer.



 
#5
I saw Eric Adams' comments on the forum from 2016 regarding copper head gaskets ,but i didn't see his video you referred to. If you provide a link, I will check it out.

His forum comments were regarding the sealing of the gaskets and the use of silicone. There are specialized sprays for the sealing of copper gaskets and my idea is to use such a spray to aid in the sealing of my gaskets. Silicone will not factor into my situation. I

I am willing to go the copper head gasket route and report back to forum on my results. I'm thinking it is easier to buy a thinner head gasket to raise compression than to find a machine shop and send out a head out to be milled. To ME, its worth a try. i have a number of engines to do.

....That being said.... I look forward to further input from the forum and appreciate those taking time to read my post and reply.
 

delray

Well-Known Member
#6
and if you don't know the guys at the machine shop? they could easily charge you $100 for setup,milling....etc.
yep a gasket is much cheaper route.
let us know what works the best for you when you get it running...…...:scooter:
 
#7
Thanks Delray,
I was typing my last response when your post was came up. I didn't see it till now. I see your thoughts reflect mine. Just need a little clarification, you mentioned the gaskets were old; were they NOS unused or, old-previously installed and crushed to the post torque thickness?

BTW I have an order into copper gaskets, so I'm already committed. I just need to know what is considered the proper thickness for the old Hipo gaskets.
 

delray

Well-Known Member
#8
yes, old factory type gaskets use. not sure on a new gasket how thick they are before crush. no new ones on me now. I believe my cousin had a factory Tecumseh performance head gasket that was something like .040 ? I wish I could remember that number.
 
#9
Ok thanks, they were used.
Back in the day , I had a thin copper head gasket i bought out of an ad in minibike guide. It got creased so i stuck it inside a book to flatten out and forgot what book i put it in!

Don't feel bad, I cant remember either. You know the old saying ...If you remember the 60s( in my case the 70s), you weren't there..
 

delray

Well-Known Member
#10
think I got lucky when I found this early hs-40 engine when I built it. came with a small bolt pattern and the chamber was small too and having a .020 over piston in it. help little in the compression. like to see if this company would make a .042 thick gasket for my hs-40 . from what info I have gathered they will make it for you.
from what markus has said in the pass the head chambers where all the same,but my early head came with a much smaller chamber.
think the later years the head gasket design might of dictated the compression because the bolt pattern for the 40's and 50's became the same. so if the engine was a hs40 the gasket would be much smaller or I should say closer to the bore to help keep the compression correct. that's still something to look into?
here is my head.
https://www.oldminibikes.com/forum/index.php?threads/hs40-the-early-revisions.138509/page-2
 

markus

Well-Known Member
#11
yes, old factory type gaskets use. not sure on a new gasket how thick they are before crush. no new ones on me now. I believe my cousin had a factory Tecumseh performance head gasket that was something like .040 ? I wish I could remember that number.
.040 sounds about right from what I remember of the ones I had gotten out of some old performance parts stock few years back I think it was Ables that made them back in the day. I have some Briggs ones here, theres a straight copper one that's only like .022 the Fel pro racing gaskets with the coating on them unused are a little over .030 so they problaby squish down to .030

Problaby worth a shot and not be much of a leak issue if your into a full rebuild where you can true the deck surface as well as the head when you are building.
 

markus

Well-Known Member
#13
I just ordered one
reusable head gasket would be nice
I did too :p (thanks for showing that site BTW delray) Only HS heads I have here that are cut are .010 off.....I was being a pussy about it when I had them done, Will try it with the high fin head I modded since its stock in the chamber.
 

cfh

Well-Known Member
#16
i can send an email to Eric Adams. He works for OldMiniBikes warehouse.
Roccos does the bike pull over differently with the increased compression?
when you say it made a difference, can you explain what was different? thanks
 
#17
i can send an email to Eric Adams. He works for OldMiniBikes warehouse.
Roccos does the bike pull over differently with the increased compression?
when you say it made a difference, can you explain what was different? thanks
Sure the bike would go 36 MPH with me on it when it had the stock head gasket in it. After I put the copper gasket in it the bike went 45MPH so like I said (It made a huge performance upgrade to the engine) Pull starting the engine didn't seem any different than before. This is just my experience with this particular engine.
 

cfh

Well-Known Member
#20
I talked to Eric Adams he works For OldMiniBikes warehouse and he says they do not sell copper gaskets. because they are not easy to work with. Here’s what he had to say ...

don't recommend copper gaskets for the "noobies". The copper needs to be "annealed" to soften the material before installation. Noobies do not do that and the gasket will never seal. That is why we don't sell them!

Every Briggs 5 I have rebuilt with the copper head gasket took me a long time to scrape the silicon off of them because they never sealed properly
They are effective when prepared properly and I have no doubt that you could get them to seal. You need to anneal the gasket and then verify the surfaces are flat. Most old flathead decks and heads and never truly flat! The copper gaskets need absolutely flat surfaces to seal.

I use fiber type gaskets on all my flatheads. I will gain compression from milling the head!
I am not a fan and do not recommend them!
 
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