deck height ?

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nevhunter
Holder of a Golden Anorak
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Re: deck height ?

Postby nevhunter » Fri Feb 10, 2017 4:56 am

The thickest one I have is 1". Nev

Ian.Taylor
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Re: deck height ?

Postby Ian.Taylor » Fri Feb 10, 2017 4:59 am

Thanks Nev, I'll check Friday night after work.

david.anderson
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Re: deck height ?

Postby david.anderson » Fri Feb 10, 2017 8:32 am

To remove material from the cylinder base (which is 1” originally) was common practice in Australia with the iron engine VH. I have 2 different cylinders that had 1/8” and 1/6” removed from the base flange. I have increased the 1/16” slightly to .070” with one cylinder and use that with a 7.5 piston in my 49VH. That gives a compression ratio of 8.3 to 1 which runs superbly on 98 unleaded. With such a modification there is no problems with piston to valve clearance which is more than adequate even with a HS cam. A standard piston does not extend beyond the cylinder wall at the extremities but sits below the rim.
A cylinder liner for a VH has a wall thickness of about .080” and there is no lip at the top. The raised cylinder spigot is unaffected when a liner is fitted as the liner is pressed in then finished flush with the existing spigot.
With regards to valve lift, the rockers are 1-1 and do not alter the lift from pushrod to valve. The cam levers do however alter the valve lift. The twin lobe follower has a lift ratio of .86 which reduces the lift of the A7/642 to .318” at the valve. The 56mk1 HS cam and HS follower lifts .430” at the valve.
David

Ian.Taylor
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Re: deck height ?

Postby Ian.Taylor » Sat Feb 11, 2017 6:13 pm

Good Info Dave .Thanks
Ok back out yet again to have another look at this issue.
After measuring the Flange which is 1" and the cases ,comparing figures to my VHA case..all seems good, so why the 2mm protrusion.

I had a look at the rod,first.A7/S24.Yes the 5 looks like an S..lol.look up in the book and the VB uses A7/524.I then yank off the case and yes indeed it is a VB Crank,30mm Vs 28 for the VH..also A7/550 is stamped on the flywheel.

Now I know why the 2mm difference.
looks like I'm making an aluminum 2mm spacer and maybe longer push rods.

Michael Will
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Re: deck height ?

Postby Michael Will » Mon Jun 29, 2020 8:24 pm

Hi,
I seem to be having the same issues with the Deck height of the piston,the dome of the piston is higher than the barrel old piston was dished , I am using the club's Omega piston. There has been work done previously on the motor, I am thinking the conrod is the problem at this stage.

Any help is appreciated.

Ian.Taylor
Holder of a Waxed Cotton Anorak
Holder of a Waxed Cotton Anorak
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Re: deck height ?

Postby Ian.Taylor » Sun Jul 12, 2020 10:29 pm

Putting the original VH Crank back in solved the problem.


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