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#507807 09/25/13 11:12 am
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Allan G Offline OP
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Following Roger G's thread about tappets where he pointed out about he has a 010" high spot.

This has gotten me thinking about using this method to increase compression.

A standard copper head gasket after crush and several times of re-application measures 040".

I have been looking at head gaskets of between 020-025" - which is getting difficult to have made, so... And as I'm convinced that my head gasket surface isn't flat ( will measure it later)

Would I be safe removing about 015" off top the top off the cylinder and then using a standard gasket?

The ring height Is well below where the top of the barrel is, and there is about 50-60 thou gap between the top of the fin and the current surface.


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68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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That much should be fine and will raise your compression less than 1/2 point.


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wak Offline
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so the cast barrels are 010" out at the top ? are they 010"out at the base ?8 minutes out of parallel of the bores ?umm increare the cr with british petrol ?food for thought?


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Allan... Think you might have missed the last part where I think it's only .040" to .050" in the center.

straight edge across the top in the center of the bore from left to right what I found was about .008 to .010 high on the right side. Touching the left side and center so I guess it would actually only be .004 to .005 high in the center

The first time I tried to stop the leak I bought a new gasket that was quite a bit thicker than the one that came one the bike when I bought it. Never did take any measurements at the time, just used the new one. It is now about .047"...would that be considered to be standard?

Will be watching where this thread go's.


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Allan G Offline OP
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Originally Posted by Alex
That much should be fine and will raise your compression less than 1/2 point.


Cheers Alex, just the answer I was looking for. Don't forget though I am running the Ed V slanted pistons, and the head has been skimmed in its life time (I should have pointed that out earlier)

Originally Posted by wak
so the cast barrels are 010" out at the top ? are they 010"out at the base ?8 minutes out of parallel of the bores ?umm increare the cr with british petrol ?food for thought?




I've not checked the surface for being true yet Wak, my reference was from Rogers comment spured the thought to use this method. The cylinders have worked fine and haven't shown any leakage (although a little suspect around the oil drain holes, sometimes it seals great and sometimes it doesn't) My sole aim is to increase


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68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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In any case, you must have a flat and square cylinder surface. I also have .040and .050 gaskets. Not sure where the .050 came from. As far as raising the compression goes, the previous comment about fuel goes a long way. However, I have found that with the Ed pistons, they need to be flush with the deck in order to produce the stated 9.5 compression. Of course that depends on how much the head has been trimmed. Best approach is to assemble before doing anything to measure the deck ht. and then (with the rings installed) install the head with gasket and measure how much fluid the entire chamber holds at TDC. I use a 2oz syringe that is calibrated in cc and model airplane fuel which wont attack the syringe like oil will. The idea is to fill the chamber so you will have to tilt the motor so the spark plug hole is mostly straight up. It will probably measure between 35-40 cc. Its important to know what you got before cutting anything. Once you know what your real c/r is, you can start figuring out what you want it to be based on intended use and fuel used. Cheers, PRT

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My A65 proved to me high compression is overrated smile.

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Roger,if its only 004" high in the centre ,maybe a bit of careful filing or even better scrapping may do the job? im only sugesting this as my experience with engineering shops is usually a costly one in many ways.are the barrels true in the other planes ?


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Allan G Offline OP
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Originally Posted by pushrod tom
Best approach is to assemble before doing anything to measure the deck ht. Cheers, PRT


Good point Tom, I will do this when I have the motor back in my hands again. The crank will be away for about 2 weeks for nitriding which will give me time to skim the barrel if I need to.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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Allan G Offline OP
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Originally Posted by Adam M.
My A65 proved to me high compression is overrated smile.


All depends on what you want to use it for, I ran my A65 for a long while with the 7.5:1 pistons and it ran well, I could even start it by hand! For a tourer its a good thing, IMO the flatter pistons allow the gasses to flow better (you don't see modern vehicles with domed pistons, if anything they are flat or concave - albeit they use a cross flow head)

I actually improved fuel ecconomy when switching to a higher compression, by about 8mpg. I used to get 65mpg with low comp pistons and got 73 with higher compression (although other factors could have been responsible) I was also able to change up sooner.

The HC pistons were able to produce a lot more power in acceleration and power at higher rpm.

Also I have suffered more pinking with the low compression pistons than anything else, only time my HC pistons pinked was when the guides were seeping oil.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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Allan G Offline OP
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I have just run the barrel on a sheet of glass with some light oil and fine grinding paste.

Without any serious work done as regards trying to skim the head, I have highlighted the high spots, as you might expect they were where the studs fit and in the very centre web area saw no paste at all and remained totally dry

[Linked Image]

A picture from the start of the year, unfortunately I didn't remove the gasket at the point the photo was taken. But it looks the piston edge don't come near the top of the barrel.

[Linked Image]


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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You can flat lap a .040 solid copper gasket down to what ever you want. I generally go for .005 increments. I have a little gasket file; black marker the gasket thickness on the copper. Taken the .020 down to .015 but thats as thin as I could go.

Currently running 10.5 to 1 pistons with .040 solid copper gasket. 100 octane fuel.

7.5 to ! Man thats cherry head compression.
Pump it up

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Hi Allan

If you got it that far without any real work, then it wont take you much more to bring it flat, keep going.

John

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Allan G Offline OP
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Originally Posted by Richard Phillips
You can flat lap a .040 solid copper gasket down to what ever you want. I generally go for .005 increments. I have a little gasket file; black marker the gasket thickness on the copper. Taken the .020 down to .015 but thats as thin as I could go


That's interesting. How do you ensure you are getting equal reduction on a flexible item?

Originally Posted by JER.Hill
Hi Allan

If you got it that far without any real work, then it wont take you much more to bring it flat, keep going.

John


I'll do just that John. Time I think for a fresh sheet of glass


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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Oh come Gill, Piece of Cake
All you do is glue it to your surface plate and skim it with a D/A starting with 180 to get it down. Then work your way along with finer sand paper.

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Allan G Offline OP
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Originally Posted by Richard Phillips


glue it to your surface plate and skim it with a D/A starting with 180 to get it down. Then work your way along with finer sand paper.


D/A???

I was thinking about sticking the gasket to one sheet of glass with a glue that can be removed with solvent, glueing a sheet of grit paper to the other and working the gasket against it, finishing the gasket off with fine grinding paste to remove any scratch lines.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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Allan G Offline OP
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well, I spent the best part of the day polishing barrel surfaces. not only on the A65, but a 400/4 barrel, 400/4 head inc rocker box surfaces and the 4 carb mounts and the rocker box. needless to say, after doing all that, cleaning everything honing both barrels and making some brake rods in stainless (note to self need a new M6 die, that will cut stainless) I'm pretty worn out. Oh and I started the day with cutting back the side covers and giving them a final lacquer.

Anyway, without further ado, keeping on topic

[Linked Image]

I really should have checked how much I was shaving off. Anyway, when the engine is back I'll CC the combustion chamber.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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Did you end up using paste or grit paper ?
Thinking about doing the same with mine..


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Allan G Offline OP
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I used 150 grit paper glued to a sheet of glass (took quite a lot of paper as it get clogged up) when it was all shiny and uniform scratches, I then use fine grinding paste on the other side of the glass mixed with WD40 as a lubricant, then keep adding and mixing a paste. It's time consuming but worth it in the end. I did the honda 4 at the same time, I fitted the head gasket dry, and so far so good!


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)


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