8 replies to this topic

[BEN99W]

Hi

 

Apologies for bringing up an often asked question, but Ive just picked up a 998 A+ engine for our mk3 and was checking to see if the head was unleaded or not. Im getting mixed answers.

 

The engine number is 99H D80 105197

 

https://blog.simonbb...e-number-guide/ states that it is an unleaded unit, but others like the Guessworks site seem to indicate it may not be.

 

Without wishing to cast doubt upon either of the sources mentioned, is there a definitive source of information somewhere or how easy is it to remove a valve to check?

 

Cheers

 

Ben

[sonscar]

Could easily be wrong but I thought 99 HE was the first of the unleaded motors.Previous to this I believe they could be an order option for the later years.Removing the head may be the only way to be definate,Steve..

Edited by sonscar, 24 October 2021 - 12:49 PM.

[nicklouse]

The only definitive way to know is to take the head off and look.

 

many leaded heads were converted or had heads swapped out meaning the engine number means diddley squat as it only refers to the engine as it left the factory.

 

I would presume it to be leaded until you open it up to look.

[Ethel]

As above,

 

Anything could have happened, especially back in the day, when used A Series bits were 2 a penny.

 

If it's unmolested the distributor advance may give a clue. If you're in a rush to get it fitted it'll be a while, running on unleaded, before it matters. If you're not, you'd gain peace of mind (as a minimum) from giving it a bit of a strip down, inspection & rebuild.

[Spider]

In the 998's it was from 99H/D81 and after that were fitted with Lead free cylinder heads. It was very late in the 998 story and so they are not common, but as the other guys have said, the only way to be sure is to lift the head and check, however it would appears your just missed out being a 99H/D80.

[BEN99W]

Thanks guys, looks like Ill have to take a look inside. I took the manifold off hoping I might be able to see in there, but of course now I see that wasnt gonna work. I presume an unleaded insert is obvious if present once the head is removed?

[Ethel]

Removing an exhaust valve would be the way to get a proper look. They're steel rings that are pressed in for the valves to seat on, a difference in colour may be the only indication once the seats have been recut. The edge inside the exhaust port is usually more obvious.

[T.Harper]

If you're not in a rush, you can just use an additive in the meantime.  I use an additive in my unleaded engine anyway to reduce impact on the seats.

[ACDodd]

Unleaded tolerance was from may ‘89 onwards with engine prefix 99HE.

Engines before this could still be unleaded becasue the factory used to produce kits to enable owners of earlier cars to be dealer converted. So it’s is entirely possible to have an ‘86 engine for example fitted with a factory unleaded head. Also cars since then could have been converted to unleaded fuel if the head had been rebuilt at any stage in its life.

As already been stated the best way to know is the physically check for hardened valve seat inserts by removing the head and investigating.

Ac