What is the deal with running a thinner head gasket?
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Cruiser
Joined: Feb 2018
Posts: 191
Likes: 9
From: Texas
What is the deal with running a thinner head gasket?
Hi all,
I picked up some comments on a different thread regarding a 96-103 conversion using a thinner head gasket and it sounds like an interesting topic by itself.
I am doing a Factory HD SE 96-103 conversion kit with 255 SE cams using my stock head with manual CR's for my 07 Road King.
Can any one comment on what issues or concerns they had with running a thinner gasket on a similar setup?
I picked up some comments on a different thread regarding a 96-103 conversion using a thinner head gasket and it sounds like an interesting topic by itself.
I am doing a Factory HD SE 96-103 conversion kit with 255 SE cams using my stock head with manual CR's for my 07 Road King.
Can any one comment on what issues or concerns they had with running a thinner gasket on a similar setup?
Ultimate HDF Member
Joined: Jun 2009
Posts: 6,899
Likes: 3,412
From: OH
The reason for the thinner gasket is to raise compression slightly. What you have to watch is the CCP #'s with the cam you are using. If you're going to go with the 255 you're on the edge depending on altitude of the magic number of 200 for a street motor and it may be difficult to tune. Most people recommend going thinner on the gasket with later intake closing cams.
Club Member
Joined: Sep 2010
Posts: 1,684
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As Todd-67 said, the thinner head gasket raises compression because there is less area to compress the volume of the cilinder into. With a SE-255, I wouldn't think raising the compression would be a good idea but you should check with an engine builder that knows.
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Cruiser
Joined: Feb 2018
Posts: 191
Likes: 9
From: Texas
I am running a a power commander 3. The SE103 kit comes with SE255 cams. I already have the K&N air filter, 02 delete, stock heads, and my D&D two into one exhust exhaust. So that tune setup is already an active download from the power commanders web site.
I was going to run with that pre selected setup. If I put the thinner head gasket on it, I assume I am going to have to tweak that tune because as you say, that added compression is going to effect the burn efficiency. I am still curious if anyone ran that set up and if they had any issues? Like, does the gasket blow out sooner? Do yo have to run different plugs, that kind of stuff...
I am thinking I am probably going to pass on the thinner gasket for my project, due to the fact I did not beef up the studs and other stuff and I will be around 10:1 compression already. But if it's not a big deal then I may consider it. On the other thread, it seemed like it was a no brainier to go that route for a cheap bang for your buck. But I got a feeling there is something more to it and there is some kind of trade off for longevity.
I was going to run with that pre selected setup. If I put the thinner head gasket on it, I assume I am going to have to tweak that tune because as you say, that added compression is going to effect the burn efficiency. I am still curious if anyone ran that set up and if they had any issues? Like, does the gasket blow out sooner? Do yo have to run different plugs, that kind of stuff...
I am thinking I am probably going to pass on the thinner gasket for my project, due to the fact I did not beef up the studs and other stuff and I will be around 10:1 compression already. But if it's not a big deal then I may consider it. On the other thread, it seemed like it was a no brainier to go that route for a cheap bang for your buck. But I got a feeling there is something more to it and there is some kind of trade off for longevity.
Ultimate HDF Member
Joined: Mar 2012
Posts: 6,129
Likes: 143
From: Santa Cruz
While a thinner gasket will increase compression, the real reason for them is more “squish” for better combustion turbulence = better mixing and burn. Static Compression should be adjusted with proper milling, combustion chamber area and/or piston dome/dish. I have not heard of leakage problems with thinner head gaskets in twin cams.
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Cruiser
Joined: Feb 2018
Posts: 191
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From: Texas
I was looking over at VT forum and they all say the same stuff too. Go with the thinner head gasket and higher lift cam for a cheap boost but nobody will confirm or deny that it's a really cheap boost if the gasket blows out. It seems if it was a cheap boost of performance with no down side the factory would just do it and take the credit.
it seems that the 103 kit I am buying was the kit they use on the 07 cop bikes. So, it can't be that radical and unreliabul.
With the 255 cams that came with my kit, it's telling me I needed to use different valve springs due to the higher lift. It never ends.... I just blew another $120 on bee hive valve springs today. I would hate to put this thing all together and find out because I was trying to squeeze a little more out of it that the head gasket becomes the weak link. I would like to know if anyone blew one out or last 80k miles.
it seems that the 103 kit I am buying was the kit they use on the 07 cop bikes. So, it can't be that radical and unreliabul.
With the 255 cams that came with my kit, it's telling me I needed to use different valve springs due to the higher lift. It never ends.... I just blew another $120 on bee hive valve springs today. I would hate to put this thing all together and find out because I was trying to squeeze a little more out of it that the head gasket becomes the weak link. I would like to know if anyone blew one out or last 80k miles.
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Joined: Jul 2007
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From: Bates County MO
All the stock beeehives from 05-present ( unless damaged/broken) can handle the lift of the SE255 cams; they work very well at 10:1, with that pipe, & a good tune, I would expect 110-112 TQ and 89-91 HP.