G'day all
picked up a a12 motor at the weekend[only wanted the extractors & weber]but got the complete motor & 3 gearboxes for $200,the owner said that he was told that the motor had been recently rebuilt but had a crook valve so he threw in a fully reco head also,just stripped it down and found that its got 020 flat top pistons and all new bearings but the head has had 2mm machined off and the ex valve on #1 cyl had just touched the piston and bent the valve,the head that came off has a heart shaped comb chamber where the fully reco head has a round comb chamber also the cam looks like its been coated in molybond and has 401 stamped on the end,does anyone know if std cams are stamped?the new head has new valves/seats/guides&seals how much can you safley machine off a round comb head to increase compression?sorry for maybe dumb questions but I'm a bit Datsun dumb as its going into my 59 morris 1000
tks Russ

Quote:
With normal A12 dished pistons you can machine off up to 2.29 mm. But not with flat-tops. Maybe 1.5mm?

Note that the A12 open combustion chamber is not less compression than the A12 heart-shaped chamber. They both have 29cc chambers.

But milling the head is the worst method for gaining compression. Better to use flat-top pistons -- or if you want more than 10:1, use a slight dome.

Quote:

Nissan Competition cams were stamped on the end:


Most aftermarket cams are also stamped there.

A10 cams are cast "180" or other numbers
Early 1200 case "H10" or other numbers
Late 1200 cams are cast "H50" or other numbers

tks ddg it looks like it's a A10 as its cast 180, so is there any benifit performance wise running a A10 cam in a A12 or would it be better to find a std A12 or regrinding the A10?
I'm not looking for a firebreathing monster just a bit more power,current setup in the "MORRY"is a stock A12,1200 4 speed g/box & diff but I have a set of extractors & 40dcoe weber yet to be fitted

Early A12 cams might use the 180 casting. It would be very unlikely to find an actual A10 grind put into an A12.

To get more power, rev it up higher. If you shift at 5000 and keep the RPMs above 2500 the performance goes way up (redline is 6000 RPM so it's no abuse to run to 5000 RPM).