G'day,

Have been trying to find out what head my 850 has on it but I can't seem to find the right ones for my markings. I was told by the previous owner that he thought it may have had an 1100 head put on it at some stage but he wasn't sure.

Looking from the front of the engine with No. 1 on the RHS the marking are:

'2A3' between the valves for cyls no 1 and 2 with a '2' above this near the manifolds

'MOWOG' between the valves for cyls 2 and 3 with '71A' upside down above this near the manifolds

'21086' between the valves for cyls 3 and 4 with 'MC' above this near the manifolds.

Pics below for reference.

Thanks, Rocky

Is there any number on the thermostat end ?

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Not that I can see Timmy.

All the ones I’ve seen with 21086 are 2A629 heads - stock 850 head.

To be 100% sure you might need to take off the head, but it’s possible that bigger valves have been fitted too

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Timmy - the head has been done up and is already back on the block. Unfortunately, I didn't get a chance to measure the valves beforehand though. All I've got is a pic. I've checked the paperwork from the joint that did the head and it doesn't specify valve sizes. Just refers to a Mini 850.

No big drama whatever it is. I was talking to a bloke today who has a few minis and he was showing me some of his 1275 engines and got talking about heads etc. He mentioned that the casting numbers on the head could be used to determine what motor mine was off.

Cheers, Rocky

Assuming they are standard size 1” exhaust valves, the intake ones are much bigger than normal - looks like around 1.2”

It would have to be a 850/998/1098 head (not 12G295 or 206) based on the shape of the combustion chambers

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Thanks for the info Timmy.
When I got my rocket, it was fitted with a custom set of combined inlet manifold and extractors and twin 1 1/4 SU's. Someone along the line had obviously hotted it up and looks like he might have fitted a different head as well perhaps.

He must have been a racer back in the early 60's cos he also fitted a Holden EK chrome bonnet emblem on it to make it look hotter I suppose.

does it have a boss for a temperature gauge in the front below the thermostat?

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did I tell you that I won a trophy?

Hi Simon,

No boss for temp gauge on the head or block. I've put a new thermostat housing on that has provision for a gauge.

It's an 850 or Deluxe head.
All 1098 heads had a temp sender.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks Doc. Did the Deluxes all have 850 motors or 998's?

Would the larger inlet valves just be a result of having the head done up and they needed to fit larger valves when they machined new seats?

Rocky

Deluxes are 998. It's probably a stock 850 head...

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did I tell you that I won a trophy?

Standard 850 and 998 inlet valves are 1.090".
Exhausts are 1.000" in all small bore heads.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks Simon and Doc.

As Timmy said, the inlet valves are much larger than the exhaust. I did a rough measurement scale on the picture of the head and if the exhaust valves are say 25mm or 1" then the inlet are roughly 30mm or about 1 3/16".

Would this increase in size be as a result of the seats being buggered and when they machined the head, they had to fit larger valves? I don't have any pics of the head when it was first taken off the motor to compare it to.

My question is just out of curiosity.

Rocky

It's common to fit bigger valves for either better flow, or because the valve seats in the head are worn.
I did this with my 1100S head- fitted MK2 S inlets and 1.219" oversized exhausts.
No unleaded exhaust seats, I use Flashlube.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.