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Old 03-27-2011, 05:53 PM   #105
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Join Date: Sep 2006
Default Hmm.

1. The three Fiat two-sticks that I know tolerably, that is to say the 1592 cc, the 1608cc and the 1792 cc (in the slightly different guises) were the simplest things in the world to change the shims. You needed a thing ilke a bent fork (preferably a special tool but you could do it with a couple of table knives or even an actual bent table fork) slid it between the cam and the bucket, that depressed the valve on its springs and the shim popped out in your hand - big thing about the size of a 2p piece (sorry, no idea what that is in US dollars) but thicker and you slipped in a new one and measured again. Most Fiat nuts had a biscuit tin full of different thicknesses! If you were sensible and greased one side of the cam cover gasket but used red hermetite on the other you didn't need a new cam cover gasket and there were only two retaining collars to undo and replace.

2. In the world of simple swappery, it seems that an unmodified 531 (and sodium filled valves) with an A or V cam (surely VXs are rare as rocking horse doodoo) will outrun an equivalent (N/A or turbo, using stock turbos) by a street. The high lift cams from the specialist suppliers are hundreds of pounds in the UK, and the number of tuning shops who can properly port and re-valve a head with bigger valves must be under 10 in the country.

3. I'm not that bothered about idle (so long as I pass emission control) nor indeed about torque since I quite like changing down. I think that (memories stirring from the past) that velocity is largely about droplet size and wall wetting, so so long as you rev it's of little relevance.

4. No, I have no tested these ideas other than the FIAT shims since about 1967 when I did have some BMC A series heads with very modified squish areas (Somender Singh did not exist then) and the habit of producing sheets of flame on a closed throttle, but a nice noise on an open one - up to about 8,000rpm, quite a lot for a BMC A series crank!
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