8 replies to this topic

[ECG317W]

Hi,

I've got a 998 cylinder head which I'm ALMOST certain is unleaded. Is there any way I can confirm this from the casting? By the way, casting number is CAM4810 (which could be leaded or unleaded as far as I know).

Thanks,

Ben

[ECG317W]

bump

[Ethel]

No, you can take a gamble on the engine number being correct or, if it's off the block, you can look to see if it has pressed in seats on the exhaust valves.

Not A Series, but the best illustration I could find

[Guess-Works.com]

Only sure file way is to remove an exhaust valve and look for the seat.

[ECG317W]

Thanks for the replies. I'll take an exhaust valve out and take a look.

Cheers

Ben

[bmcecosse]

Don't think the 998 heads ever had 'pressed in seats' from the factory. They simply fitted better quality exhaust valves - and sold that as 'unleaded'. Good news is - it doesn't matter! Just run the engine on unleaded fuel - set the exhaust valve gaps to 15 thou - and keep a weather eye on them. As long as they don't close up - no harm will be done. ths heads are '10 a penny' anyway - so worst that can happen is that you eventually may need another head - good excuse then to upgrade to a head with larger valves/better flow. ie 12G295 or even better 12G 940

[daemonchild]

Is it worth adding 'additive' in this case or not?
I've bought some for my 1973 mini, but not put it in yet as I'm hardly stressing the engine while it sits in the garage getting fixed up.
But once I'm on the road....?

[bmcecosse]

Up to you. Most are made with mixes of sodium/potassium and hocus pocus! They may help slightly with octane number to suppress pinking - but do little for the exhaust valve seat. The ONLY additive I think MAY be worth having is TETRABOOST. It's the only one with genuine Lead Tetra -ethyl, and so effectively makes unleaded fuel into leaded fuel. It must NOT be used on a car with a catalyst. Unless you are going to be caning your car on M way for long distances - don't worry about additives. My 1098 A series (940 head) has done over 10,000 miles now on unleaded and no additives. It's fine !

Edited by bmcecosse, 21 November 2009 - 09:20 PM.

[daemonchild]

Up to you. Most are made with mixes of sodium/potassium and hocus pocus! They may help slightly with octane number to suppress pinking - but do little for the exhaust valve seat. The ONLY additive I think MAY be worth having is TETRABOOST. It's the only one with genuine Lead Tetra -ethyl, and so effectively makes unleaded fuel into leaded fuel. It must NOT be used on a car with a catalyst. Unless you are going to be caning your car on M way for long distances - don't worry about additives. My 1098 A series (940 head) has done over 10,000 miles now on unleaded and no additives. It's fine !

Cool! Thanks.
Little Em is far to old to even know what a catalyst is!
Caning on the M way? Nope. She might do the odd long journey from time to time like any car I guess.
So we're good all round.
And as you say, 10 a penny..