200 with 250 2V Head

I have another 2V head i am getting next week for my 200, been told by a bloke that just bolting it on will take my compression down to low 8’s, my 200 is 9.2.1, so milling the 2V head 60 wont help, anyone confirm this? he mentioned cast flat top pistons, but i am in no position to rebuild the whole motor, head is a standard reco, with factory alloy manifold/adaptor and 350 Holley and good set of extractors, price was good so i popped on it. Changes my mind again, 3rd time lucky for a 2V

Step one, measure the 250 2V head's combustion chamber. The head I had picked up ended up already milled once, so my CR stayed around 9.0:1, which is where I liked it. Don't go by hear say. Take the time and measure it to be sure.

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Measure for sure first, but its not often a 2v head is shaved that much, since the stock 250 2V had a huge 9.3 :1 compression ratio for 97 RON/MON leaded super. So shaving till you get a 52 cc chamber is fine. In most cases, 50 thou will get you 52 cc. A total shave from stock to 90 thou is a 46 cc chamber. 120 thou is risky, but it gives about 40 cc or so.

See viewtopic.php?f=3&t=71291

xctasy":2m3oifqy said:

Just shave to head xrwagon. 60 thou off makes a 60 cc head 50 cc. That's what everyone does with there US 200's and 250 2v combo's. Stock, with a 45 thou gasket, the 5.5 cc pistons and you'll end up with an 8.22:1 compression ratio. With a 60 thou shave, 9.3:1, same as the 155 hp and 170 hp 250 engines. Simple as mate


Between the factory low compression and high compression early engines, there was a nominal 8 cc cylinder head CC difference. With the XY, XA, and XB, an 8 cc piston dish difference.

The compression ratios for all the later standard fuel Aussie low compression I6's from 1971 to 1983 was done by putting the bigger dish 250 pistons into the 200 engine and a stock one size fits all 4.1 litre carburettor cylinder head chamber. When the 1985 XF came out, the low compression engine was ditched.


No one knows for sure exactly what the standard 1971-1975 200 and 250 XY, XA and XB piston spec was. Based on what I've seen, I think 0.0 flat top for high compression 200, wide brim 12.5 cc dish for 250 and low compression 200, and a the late x-flow 22.7 cc deep dish for low compression 250.


But they had a one size fits all log head ans 2V 60 cc chamber from 1971 to 1975.

The Aussie Low compression standard fuel ex Taxi engines 3.3 and 4.1 engines from 1965 to 1975 were something of a mystery.There's lots of info on the X-flow 1976-1983 taxi engines.

I have two factory Aussie 200's, a G-code 1966 shallow 7.803" deck 200 XR, and an E code 1972 tall 9.38" deck 200 XA. The XR has the 200/221 piston, with a 5.5 cc small dome piston relief and a factory 52 cc small chamber head.

The E code has the stock 250 piston with a 200 crank and rods, and standard 250 head with its 60 cc chamber.

The later E code LC and G code HC high compression tall deck has a wide brim shallow piston of either a nominal 0 cc flat top piston, or the 250's HC 250's 12.5 cc piston with a 60 cc chamber.

One had a 7.7:1 compression ratio, 12.5 cc piston, 60 cc chamber

the other 130 hp and 9.1:1. 0.0 cc piston and 60 cc chamber for high compresion,

The M code 250 2V 170 hp and L code HC 250 1V 155 hp were 9.3:1, via 12.5 cc piston, 60 cc chamber

The J code LC 250 , unknown hp drop for low compression, via the later 1976-1985 cross flow 250 22.7 cc pistons

3.3 200 cubic inches (3.3L) 6 cyl
Bore and stroke: 3.68 x 3.13 inches
Power: 130bhp (97kW) at 4600rpm
Torque: 190lb-ft (258Nm) at 2000rpm
Pushrod overhead valve, 2 valves per cylinder
Fuel system: Single throat carburettor
Compression ratio: 9.1:1

4.1 250 cubic inches (4.1L) 6 cyl
Bore and stroke: 3.68 x 3.91 inches
Power: 155bhp (116kW) at 4400rpm
Torque: 240lb-ft (325Nm) at 1600rpm
Pushrod overhead valve, 2 valves per cylinder
Fuel system: Single throat carburettor
Compression ratio: 9.3:1

4.1 2V 250 cubic inches (4.1L) 6 cyl
Bore and stroke: 3.68 x 3.91 inches
Power: 170bhp (127kW) at 4200rpm
Torque: 250lb-ft (339Nm) at 2200rpm
Pushrod overhead valve, 2 valves per cylinder
Fuel system: Bendix twin throat carburettor
Compression ratio: 9.3:1

Click to expand...

I have the webpage saved. I'm up in the air on what I want to do with it. Needs a serious revamp and probably going somewhere else for service.