103 big bore question.....
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Road Warrior
Joined: Dec 2006
Posts: 1,533
Likes: 2
From: Nebraska
103 big bore question.....
I have a chance to buy a 103 partial kit. The kit comes with the screamin eagle flat tops. the cylinders are 96's bored out to 103. I am waiting for an answer on who bored out the cylinders which I haven't gotten yet. I figured I could pick this kit up fairly cheap and then add my choice of cams and some adjustable push rods to the mix later. Was planning on doing the work myself.
Anything I should watch out for on these cylinders? I haven't asked yet but probably no warranty on them. The pistons and rings are new in packaging. I am figuring I would like to take the cylinders to someone (haven't figured out who yet) to have them checked out and Measured or guaged? (not sure of the terminology here).
The second question is does anyone know of a place local in the midwest that would be recommended for boring out my stock 96 cylinders? Would this be a speciality that I would need to look for or could pretty much any machine shop do this with just being told I want to go from 96 to 103? I was thinking it might be cheaper for me to get the pistons and cams seperately once I figure out which cams to go with.
This is going to be my winter project this year. On the subject of cams... pro's and con's of gear driven over chain? Any? Other than the fact I don't have to worry about tensioner's on the chain driven cams. I am looking for more Low and Mid range torque as everyone else does. This is on an '07 Heritage.
As mentioned. I am going to do the work myself. Looking at the manual on cams... it doesn't look to be that hard at all.... other than the special tools. Any gotcha's or watchouts?
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Anything I should watch out for on these cylinders? I haven't asked yet but probably no warranty on them. The pistons and rings are new in packaging. I am figuring I would like to take the cylinders to someone (haven't figured out who yet) to have them checked out and Measured or guaged? (not sure of the terminology here).
The second question is does anyone know of a place local in the midwest that would be recommended for boring out my stock 96 cylinders? Would this be a speciality that I would need to look for or could pretty much any machine shop do this with just being told I want to go from 96 to 103? I was thinking it might be cheaper for me to get the pistons and cams seperately once I figure out which cams to go with.
This is going to be my winter project this year. On the subject of cams... pro's and con's of gear driven over chain? Any? Other than the fact I don't have to worry about tensioner's on the chain driven cams. I am looking for more Low and Mid range torque as everyone else does. This is on an '07 Heritage.
As mentioned. I am going to do the work myself. Looking at the manual on cams... it doesn't look to be that hard at all.... other than the special tools. Any gotcha's or watchouts?
[align=right] [/align]
May our Moderator Rest in Peace
Joined: Sep 2006
Posts: 11,386
Likes: 35
From: Rochester, NY
RE: 103 big bore question.....
I'm not sure that boring out stock cylinders more that .030 or .060" is all that great an idea.
Usually bigger bore cylinders need to have the cases bored out to match and that tells me there may not be enough extra "meat" in stock cylinders for that bigboring job, while still maintaining reliability.
This may be an even more important consideration if your thinking of putting even more High Perfomance goodies in later. The cylinder walls may turn out to be a bit on the thin side after boring to handle the extra pressures without flexing or even cracking.
I would be interesting in hearingif anyone knows exactly how much is cut out to make the 96 to 103 jump. I don't have a calculator handy, but it seems like that kind of increase would need to be on the order of something north of .090" and that sounds like it may be a little too much for my taste.
Usually bigger bore cylinders need to have the cases bored out to match and that tells me there may not be enough extra "meat" in stock cylinders for that bigboring job, while still maintaining reliability.
This may be an even more important consideration if your thinking of putting even more High Perfomance goodies in later. The cylinder walls may turn out to be a bit on the thin side after boring to handle the extra pressures without flexing or even cracking.
I would be interesting in hearingif anyone knows exactly how much is cut out to make the 96 to 103 jump. I don't have a calculator handy, but it seems like that kind of increase would need to be on the order of something north of .090" and that sounds like it may be a little too much for my taste.
Road Master
Joined: Jul 2005
Posts: 1,061
Likes: 5
From: Fort Worth TX
RE: 103 big bore question.....
If you are worried about the cylinders bore yours to the pistons you are buying. There is no worries at all boring that cylinder to that size. We bore them to a 107 and you are still fine at that size. A small cam with the stock heads and a 103 would be a nice mild build. You may have to run a thinner head gasket to gain some compression for the cam. For low end a andrews 37 would run extremely well. A woods 6 would work, a hq cam. There are tons of cams that will give you great low and mid range power, on a budget.
Road Master
Joined: Jul 2005
Posts: 1,061
Likes: 5
From: Fort Worth TX
RE: 103 big bore question.....
Well the bore should be 3.750 for a 88 inch or 96 with the longer stroke. bore the cylinders to 3.875 you have either a 95 inch or 103 based on stroke. Bore the cylinders to 3.937 you have 98 inch or a 107 again based on stroke. That would be as far as you would want to go. Now all the 95 or 103 cylinders as well our 98 or 107 kits are done on stock factory hd cylinders. There is no case boring needed and they are extremely stable. Beyond that you would ned to start with a larger cylinder. S&S made a 106 kit that is a 95 inch bore with a 4.5 inch stroke but they had a problem with oil usage for the most part. The piston is extrmely short to the point of the wrist oin hole cut through the oil ring.
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Road Warrior
Joined: Dec 2006
Posts: 1,533
Likes: 2
From: Nebraska
RE: 103 big bore question.....
ORIGINAL: HDWRENCH
If you are worried about the cylinders bore yours to the pistons you are buying. There is no worries at all boring that cylinder to that size. We bore them to a 107 and you are still fine at that size. A small cam with the stock heads and a 103 would be a nice mild build. You may have to run a thinner head gasket to gain some compression for the cam. For low end a andrews 37 would run extremely well. A woods 6 would work, a hq cam. There are tons of cams that will give you great low and mid range power, on a budget.
If you are worried about the cylinders bore yours to the pistons you are buying. There is no worries at all boring that cylinder to that size. We bore them to a 107 and you are still fine at that size. A small cam with the stock heads and a 103 would be a nice mild build. You may have to run a thinner head gasket to gain some compression for the cam. For low end a andrews 37 would run extremely well. A woods 6 would work, a hq cam. There are tons of cams that will give you great low and mid range power, on a budget.
Thank you HDWRENCH. I have decided to wait until next year. Mainly because of the information you supplied. It might be better to wait and do a 107 with a little more time, planning out and money than a 103 right now.
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Ultimate HDF Member
Joined: Feb 2007
Posts: 7,663
Likes: 7
From: Northeast Ohio
RE: 103 big bore question.....
It is routine to bore stock cyls to 3.875, no need to buy the big bore cyls from HD, which are basically stcok cyls bored. The 96 to 103" will get you good results and there are a tom of options out there as far as cams, heads, etc. Another option is to send you cyls and heads to a builder such as HQ or GMR and they will bore the cyls, do the heads, fit pistons to the bored cyls, so basically when all the parts return, you just bolt in all back together. Go to the HQ website to learn more.
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