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Barrel height

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Can anybody please confirm the original height of a 1956 Dominator 99 cylinder barrel ? My barrel has had the spigots removed and the  machined top boss height is minimal and washes out to part of the right hand side top fin. It has been suggested to me that the standard height is 41/2” and whilst mine does measure 41/2” , I really would like confirmation . 

 Perhaps the casting of mine is a poor one and I am having the barrel currently re lined and bored back to standard . On reassembly I intend to fit a 0.030” compression hopefully to get the compression back to standard manageable level of around 7.4 : 1 . 

All advice most welcome.

George

 

 

 

 

 

Hi George,

I have just verniered my barrel in 6 places and get 4.558" to 4.566" which is very close to the above.

Regards

Dick

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Further to my earlier query and constructive replies, I have now got my barrel back from having it re lined and rebored back to size. The barrel height has as I suspected been reduced by a previous owner and measures 4.520". Comparing Richard and Tony's figures  then the barrel has had 0.040 " lopped off. Due to it's high starting effort I had originally assumed that it had had high compression pistons fitted but now I am better educated !

I have a 0.030" compression plate ready to fit which will hopefully help in reducing the compression. I understand that if I fit a thicker compression plate then the geometry or length of the pushrods could introduce problems. As I do not wish to go further down this road then I will fit the 0.030" compression plate and keep my fingers crossed. 

As usual any advice would be welcome.

George 

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Over the years its likely that the valves have become recessed ,but the machining of the barrel is likely to compensate for that. So its quite likely that you won't see any problem anyway. Serendipity?.

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A couple of points worth checking before you start bolting all the big bits back together. Skimmed barrels and recessed valve seats are not a good combination. The pushrods will lose a lot of the adjustment clearance with either. Mix both of these together and the pushrods will not fit at all and need to be shortened.

You can get hold of extra thick cylinder head gaskets from companies who specialize in making such items. A 40 thou thick solid copper gasket would sort out the skimmed barrel and and any recessed valve seat issues. The fun and games of a thicker copper head gasket is trying to get it annealed evenly.

Measure up inside the head to ensure that the inside is recessed enough for the barrel spigot to fit with a standard gasket. If the head has been skimmed then there is a possibility that the height of your new liner spigots will hold it away from clamping down on firmly on the gasket enough to prevent it from leaking or even blowing.

What is the preferred method of determining  as to whether the push rods are the correct length ?

I am going to fit a 0.035" thick cylinder head copper gasket in addition to the 0.035" thick compression plate between the crankcase and the barrel as previously mentioned. 

The new liners have spigots and I will indeed check that there Is clearance into the recesses to ensure that the head sits down onto the gasket.

George

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I feel that with the added compression plate, it might be Trial & Error. The push rods will fit but will be lower in the tunnels due to the camshaft followers being 0.035" further down. The solid copper gasket should not crush significantly so that should not add to the clearances. The point to check is that the rocker arms may have a changed geometry resulting in the adjuster end striking the inside top of the cylinder head. 

 

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