120” want to up the compression

[rking1550]

Hey guys. I have a twin cam 120". SE cases
S&S flywheels. 4.060 cylinders. T-man thumper heads 102cc's. The spec sheet says heads were cut .008. I'm assuming that's just to be sure they true.  Compression is 11.3.
Is it possible to mill the heads enough to get the chambers down to 96-98 cc?  Without fitment issues with intake or exhaust? Also I know valve to piston would need to be checked.
 I'm thinking
I want to raise the compression to 11.8-12 and run the t- man 662-3 cam

Oh, almost forgot pistons are SE 120 high compression. The head sheet has them listed at 13.5cc

[kd]

I have my doubt whether or not it is at 11.3 with heads that CC at 102 cc.  IME The Screamin Eagle MVA  head on the 120R takes between .040 and .050 to achieve the level of 89 cc. With the SE flat top 10.5 pistons it produced 205 CCP at 11.1 calculated compression.  This is at zero deck.

Have you put your numbers through the BigBoyz calculator?

[rking1550]

I have my doubt whether or not it is at 11.3 with heads that CC at 102 cc.  IME The Screamin Eagle MVA  head on the 120R takes between .040 and .050 to achieve the level of 89 cc. With the SE flat top 10.5 pistons it produced 205 CCP at 11.1 calculated compression.  This is at zero deck.

Have you put your numbers through the BigBoyz calculator?

It wasn't a 120R. Not sure what the heads were to start with. The numbers I listed came right off of T- man's sheet pistons/heads.  102ccs on the heads and pistons @ 13.5 cc.
Yes I used big boyz calculator. That's where I came up with the cc's I'd like to try and get down to.

[kd]

I have my doubt whether or not it is at 11.3 with heads that CC at 102 cc.  IME The Screamin Eagle MVA  head on the 120R takes between .040 and .050 to achieve the level of 89 cc. With the SE flat top 10.5 pistons it produced 205 CCP at 11.1 calculated compression.  This is at zero deck.

Have you put your numbers through the BigBoyz calculator?

It wasn't a 120R. Not sure what the heads were to start with. The numbers I listed came right off of T- man's sheet pistons/heads.  102ccs on the heads and pistons @ 13.5 cc.
Yes I used big boyz calculator. That's where I came up with the cc's I'd like to try and get down to.

Ahhha, domed pistons?

[Ohio HD]

Were they Harley Davidson 110 heads or MVA heads? I assume one or the other due to the large chamber size.

With the heads off the motor, measure with calipers the distance between the head gasket surface and the lower rocker box surface. 110 heads uncut measure really close to 3.750". Uncut MVA heads will measure close to 3.725".

This gives a starting point to understand what can be removed from the head. I'm not 100% sure how much can be removed from the 110 or MVA head, but I know one thing that gets in the way is the auto compression release. But I have heard that guys shim them up so that they can still be used with heads that have interference due to machining the head gasket surface. I would expect that you would need to remove about 0.037" to 0.040" to get to 96cc.

Exhaust I doubt would be any issue, unless it's a super tight 2 into 1 now. If I remember correctly S&S used to say to shoot for 0.015" clearance for each side of the intake to the heads. You could always take a little off each side of the intake if needed.

Below are estimates I made, the first is as it is now, I show 11.2 which is close to what you estimate The second is the 662-3 and with heads at 96cc. That shows the 11.9 you're looking for.

First I would try to see what heads they are. I suspect either 110 or MVA will be OK to machine more to get 96cc. I would ask who ever will be doing the machining once you know what heads they are. And what they measure now. 

[rking1550]

I have my doubt whether or not it is at 11.3 with heads that CC at 102 cc.  IME The Screamin Eagle MVA  head on the 120R takes between .040 and .050 to achieve the level of 89 cc. With the SE flat top 10.5 pistons it produced 205 CCP at 11.1 calculated compression.  This is at zero deck.

Have you put your numbers through the BigBoyz calculator?

It wasn't a 120R. Not sure what the heads were to start with. The numbers I listed came right off of T- man's sheet pistons/heads.  102ccs on the heads and pistons @ 13.5 cc.
Yes I used big boyz calculator. That's where I came up with the cc's I'd like to try and get down to.

Ahhha, domed pistons?

Yes

[Ohio HD]

    110 heads have a head badge on both front and back head. The MVA heads only the front head has a badge.

[kd]

    110 heads have a head badge on both front and back head. The MVA heads only the front head has a badge.

My MVA heads came on a 120R crate engine.  They have a SE badge on the front head and a 120R badge on the rear.  Probably not a good comparison because they were purpose mounted on a factory assembled engine.

[rking1550]

    110 heads have a head badge on both front and back head. The MVA heads only the front head has a badge.

No head badges, except T-man badges. Lol.
No auto compression releases.  Manual releases. Can't remember if the auto releases weren't there or plugged in these heads.
Also forgot to mention the pistons are actually .010 over so 4.070 bore

[rking1550]

I ran the s&s 640 at the 11.3 compression made just over 142hp. It felt soft down low and no "hot rod" feel to the bike. Missed that feeling so went with the 662-2 that's in there now.
I would like to get to 150+hp and hopefully keep some of the hot rod feeling,  that's why I want to up the compression
The bikes a 01 road king

[Ohio HD]

No head badges, except T-man badges. Lol.
No auto compression releases.  Manual releases. Can't remember if the auto releases weren't there or plugged in these heads.
Also forgot to mention the pistons are actually .010 over so 4.070 bore

If they're T-Man badges that are screwed on where the 110 heads have badges, I would suspect they're 110 heads. It would be worth a call to T-Man and ask what heads they started life as. Also if the head casting numbers are available, that may be a clue as to what they started life as. 

[Ohio HD]

I ran the s&s 640 at the 11.3 compression made just over 142hp. It felt soft down low and no "hot rod" feel to the bike. Missed that feeling so went with the 662-2 that's in there now.
I would like to get to 150+hp and hopefully keep some of the hot rod feeling,  that's why I want to up the compression
The bikes a 01 road king

If you still have the 640's you might try them again with that higher compression.

[rking1550]

I ran the s&s 640 at the 11.3 compression made just over 142hp. It felt soft down low and no "hot rod" feel to the bike. Missed that feeling so went with the 662-2 that's in there now.
I would like to get to 150+hp and hopefully keep some of the hot rod feeling,  that's why I want to up the compression
The bikes a 01 road king

If you still have the 640's you might try them again with that higher compression.

640s are gone. The 662-3 is sitting on the shelf now

[Ohio HD]

I'll add a fly in the ointment so to speak. T-Man has used a lot of 20° pistons. This pic is T-man's and you can see the 20° pistons and heads machined for the piston. So if you were to reduce the combustion chamber by machining the head gasket surface, the 20° angle in the head would also need to be machined to get the proper clearance.   

I'd call them and ask what they provided in their kit. If it is their 20° pistons, you might want them to work on the heads to change compression. They would also know if the 662-3 will work as far as valve to valve clearance in those heads.

[rking1550]

No fly in the ointment there.  I talked to T man a while ago. He suggested doing just that 20 degree pistons and redoing the heads. Didn't say it was necessary and he didn't say I couldn't just Mill the heads. I didn't want to spend that much right now.
His reason was if I didn't like the 662-3 I could mill the pistons and go back to the 662-2 ,  kind of like a built in plan b.

My thought was Mill the heads up the compression. If I'm happy it's the cheapest way out. If I didn't I could Mill the pistons already in there. Save a lot of money on  20 degreee pistons and redoing
the heads.
 IF. The 20 degree pistons and more head work is the only way. I'll probably hold off a little longer.
The only crappy part is right now the rear cylinder is getting a lot of oil into it, Not sure where it's coming from , valve seal/ guide, piston /rings ? So I'll need to do some repairs no matter what. And that's what got me thinking about the higher compression and 662-3 set up.

[Ohio HD]

It depends on what pistons and what the heads are in there now as to being able to just  machining the head gasket surface. It had just occurred to me after I posted that T-Man may have used the 20° pistons in the kit you have now. Assuming he supplied the heads and pistons before.

[rking1550]

It depends on what pistons and what the heads are in there now as to being able to just  machining the head gasket surface. It had just occurred to me after I posted that T-Man may have used the 20° pistons in the kit you have now. Assuming he supplied the heads and pistons before.

I believe they're the SE 120 high compression pistons. .010 over sized.

[Ohio HD]

It depends on what pistons and what the heads are in there now as to being able to just  machining the head gasket surface. It had just occurred to me after I posted that T-Man may have used the 20° pistons in the kit you have now. Assuming he supplied the heads and pistons before.

I believe they're the SE 120 high compression pistons. .010 over sized.

Most likely you can just machine the head gasket surface to gain more compression then.

I take photos and keep records on everything I work on. That way I can check when someone says, what was that....  you did for me....   three years later. My memory isn't what it used to be.

[speedzter]

I didn't see it here, but do we know the dome volume of the SE pop tops ?
I have a 120 home brew, with SE flat tops and Larry's 110 heads set at 94cc.
No real problem with intake (slight manifold trim) or exhaust.
I did have to open up the valve reliefs , I think mainly due to larger valves.

[rking1550]

I didn't see it here, but do we know the dome volume of the SE pop tops ?
I have a 120 home brew, with SE flat tops and Larry's 110 heads set at 94cc.
No real problem with intake (slight manifold trim) or exhaust.
I did have to open up the valve reliefs , I think mainly due to larger valves.

13.5 cc.

[kd]

It depends on what pistons and what the heads are in there now as to being able to just  machining the head gasket surface. It had just occurred to me after I posted that T-Man may have used the 20° pistons in the kit you have now. Assuming he supplied the heads and pistons before.

I believe they're the SE 120 high compression pistons. .010 over sized.

Most likely you can just machine the head gasket surface to gain more compression then.

I take photos and keep records on everything I work on. That way I can check when someone says, what was that....  you did for me....   three years later. My memory isn't what it used to be.

The opening post suggests the heads were already decked .008.  As Ohio said, a fulsome conversation with Tman will be helpful for you to "confirm" what he did.  Write down your questions and also ask if he has a spec sheet showing valve to valve and valve to piston (including the valve pocket eyebrow) clearance. If you mill the heads the valve to piston and valve pocket eyebrow will change.  Because of the valve angle from perpendicular difference the amount machined is not so straight forward in calculating those clearances.  A fitting check with putty is the only way to confirm it's within safe limits.   

FWIW, as I mentioned (sort of) I had my heads CC'd to 89CC.  It took .045" each average to get them there.  One took more than the other but both were close to each other and near .045" removed.  The manifold fit OK but on the snug side, so I rubbed a few thou off to make sure the seal had a groove to sink into and heat expansion would not be an issue.

Most of us have determined that the MVA and 110 heads are 95 - 96 CC out of the box.   If Tman puts the 2.125 intakes in them, and I think he does< the shape of the new valves may change the avarage CC.  Mine had approx. .045 removed (too lazy to search out the sheet  ) and they settled in at 89 CC.  The general consensus was (and in fact right on the money with my heads) that a .007 cut will yield about 1 cc.  Of course that has to be monitored after each dive so the final approach is even on both heads.  To repeat the answer to your question about manifold fit, My notes said I removed about .030 from each side of the intake manifold to give good mounting clearance. 

One of the most important things to be concerned about is how much the valve lip will close in on the piston valve pocket eyebrow.  You'll need to measure and maybe open the clearance up.  I see Tman offers a wider clearance upon request for those that may be making changes later.  But that's a "by request" thing.  You would have had to ask for it. 

[harpwrench]

I've been looking into the SE hi compression 120 pistons for a possible 113 build. If they're what you have. Multiple posts on HTT have mentioned they are 15.5 cc, and FWIW not enough dome thickness to safely mill to lower the cc's.

[rking1550]

I've been looking into the SE hi compression 120 pistons for a possible 113 build. If they're what you have. Multiple posts on HTT have mentioned they are 15.5 cc, and FWIW not enough dome thickness to safely mill to lower the cc's.

Pretty sure that's what's in there. I bought this set up used from a good friend. Cylinders, pistons and heads. All set up by T man to run together with his early 680 cams. And I think 110 heads to start with??
 When I talked to TR a while ago he thought he milled these pistons a little. That's why 13.5 instead of the 15.5.
I know part of the problem now is remembering everything that's there. The original head work and pistons was from 2015. It's been a couple of years now. lol.
Looks like it might have to come apart to confirm what's actually there ?? And best options.
I was just hoping to keep costs down. Don't know if that's going to be a realistic expectation at this point.

I do have a call into T man on Friday. Hopefully get a call back on Monday.

[RoadKingKohn]

Why not figure out what is causing the oil leak first? That would give you a better idea as to what your cost are going to be.

[rking1550]

Why not figure out what is causing the oil leak first? That would give you a better idea as to what your cost are going to be.

True. But it's also a good reason/excuse to do some upgrades. Lol.
Original when I talked to TR about a year ago he wanted me to bore go with his 20 degree pistons, re work the heads for this pistons and use his 680 cam.   That build is out of my budget right now. But if I'm doing some repairs might as well see if any upgrades fit into the equation too.
I have the 662-3 sitting on the shelf now. That's why I'd like to try that cam.