VG barrel/piston/conrod query
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VG barrel/piston/conrod query
Hi, building a ‘48 ish 500 single with parts from a variety of sources. Crank is VG with the rod (A7/524), also found in VB’s. Apparently this is longer than the VH rod ? I have assembled it with a new VH piston, but the piston protrudes above the barrel around 3mm at at TDC. Did the VG have a shorter crown height piston ? Can’t find anything to differentiate them in the Drags tech pages, they recommend the same piston for VG and VH.
My barrel could have been shortened but I don’t think so, the base flange is 23mm thick, from the base surface to head surface is 134mm, and from base to top of spigot is 137.5mm. I can easily make a Packer for under the barrel but I’m curious to know where the extra 3mm is from ?
Thanks
My barrel could have been shortened but I don’t think so, the base flange is 23mm thick, from the base surface to head surface is 134mm, and from base to top of spigot is 137.5mm. I can easily make a Packer for under the barrel but I’m curious to know where the extra 3mm is from ?
Thanks
- adrie.degraaff
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Re: VG barrel/piston/conrod query
The VB rod is longer (and heavyer) so you need to find a VG rod.
You could opt for the stronger a VH crank and rod.
You could opt for the stronger a VH crank and rod.
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Re: VG barrel/piston/conrod query
According to the Drags info charts, the A7/524 rod was used in both VG and VB ?
- adrie.degraaff
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Re: VG barrel/piston/conrod query
That should be VG and VA.
A VG rod is aprox. 190mm centers and a VG crankpin is lining with the brass crankcase cambaring, when the pin is higher you have a VB crank in it.
A VG rod is aprox. 190mm centers and a VG crankpin is lining with the brass crankcase cambaring, when the pin is higher you have a VB crank in it.
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Re: VG barrel/piston/conrod query
Thanks Adrie. I have to deal with it as it is, I have just had the big end replaced in the rod/crank
- dave.owen
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Re: VG barrel/piston/conrod query
I have 2 spare VG cranks, both have A7/524 conrods
Dave
Dave
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Re: VG barrel/piston/conrod query
Thanks Dave, maybe mine is the correct rod then ? Do t suppose you have a VG piston that could be measured ?
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Re: VG barrel/piston/conrod query
I run both my VG and VH on the same pistons. Both barrels are the same. 24 mm base flange.
Dave
Dave
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Re: VG barrel/piston/conrod query
Thanks again. Maybe my barrel has been shortened? Does anyone have an iron 500 barrel they could measure please ?
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Re: VG barrel/piston/conrod query
Just measured an NH barrel, it is 10mm shorter than this VG one, which is what you would expect ? The mystery continues
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