31 replies to this topic

[nicklouse]

at that age it would be leaded. but it may have had a replacement head.

 

the only way is to look and see if it has hardened seats.

[paulrockliffe]

I think that if the head casting number ends in 'b' then that would be an SPI head that is unleaded.  Otherwise, as Nick says, you can't tell unless you pop the head off and have a look.

[gazza82]

Don't think the lead-free heads came in until 1980'ish .. but if yours has a bypass it is probably not an A+ head and unlikely to be unleaded. I think, and I've have to check the various resources on the net, that the unleaded 998 head is CAM4180 or something ..

 

 

That doesn't mean an earlier owner didn't have hardened seats fitted, but the only way to find out is to strip the head and inspect it.

 

 

Just use Castrol Valvemaster .. (if it's available on that side of the pond!) ...

[gazza82]

Found Keith Calver's head comparison table .. http://www.calverst....casting-number/ ... he moved it and my bookmark was broken!

[Spider]

 

If the vehicle in question has done many miles with leaded gas, the seats have become somewhat impregnated, not to mentioned work-hardened, and therefore are somewhat immune to damage from lack of lead in the gas.

They aren't immune ... Just less immune ... And that depends how they are driven ...

 

 

In part, I agree with Gazza here.

 

Valve Seat recession occurs when engine speeds over around 3000 RPM are maintained and / or exhaust temps as they leave the combustion chamber are over around 600⁰ C. Both these vary a little depending mainly on Valve material and Seat hardness, which even in straight out cast iron, varies.

 

At the higher temps and speeds, some of the valve seat in the cast iron head, which is softer, 'micro-welds' at a molecular level to the valve seat face, but it had low adhesion to the valve, so as the valve itself opens, these cast iron molecules are then blown out the exhaust. Tetra-ethyl Lead prevented this from occurring. I think with long term use there does appear to be some residual effects from the Lead for a time after it's no longer used, but how long is that going to last?  How long is a piece of string? 

 

At lower sustained speeds and exhaust temps, this still occurs but at a lower rate.

 

This is why some car (and drivers) experience no erosion and some do.

 

Personally, as  matter of course, I do all my heads (then again, I do them myself) as 'insurance'. If you choose not to do them, even with the use of additives, i would recommend regularly checking Rocker Clearances. If the Exhausts are found to be closing up, then I would recommend to have the head converted and sooner rather than later.

[wile e coyote]

I think that if the head casting number ends in 'b' then that would be an SPI head that is unleaded.  Otherwise, as Nick says, you can't tell unless you pop the head off and have a look.

As far as I know there are no "B" suffixes on 998 heads - you're quite right though 12G940B is an spi head....

[Dusky]

998 cam 4810 Heads arent All unlraded but Have a bypass normaly. My 91 Mini had an unleaded head with bypass from factory.

I strongly agree with Mr Spider here.
Id also like to add that its very much worth it to either convert or use an additive, the cost of a damaged head is far Bigger, atleast here in Belgium where machining costs are quite high

[mikal]

This might sound naive, if so please ignore my comments.

 

If you are on a tight budget and having no issues currently, why not just keep driving the car until when/ if a problem arises? At worst you'll have to get the head reconditioned sometime and replace the valve seat inserts then? Valve seat recession won't damage the engine itself as far as I know, just gradually reduce it's performance?. I can't visualise anything dramatic happening if you do nothing.

 

I might be completely wrong on this, comments welcome (AC, where are you?!)

 

Cheers

 

Michael

 

PS: As a Petroleum Chemist I'd love to know what the formulation of the additives are and what/ how they claim to work. I'll do some research. I'm very skeptical when it comes to "additives", particularly the claims made by the manufacturer/ supplier/ seller. Most of the stuff is snake oil.... 

 

Edit: Example...

 

I had a quick read of the article in this link:

 

http://www.classiccars4sale.net/classic-car-how-to-guides/restoration/a-guide-to-unleaded-additives 

 

Most of it is poorly written rubbish, unsubstantiated garbage and they chop/ change the topic talking about valve seat recession in one paragraph, than about boosting Octane ratings in the next. I'm an expert and found it a painful, error ridden, confusing article designed to to scare the average punter into buying their miracle cure all product if they care enough to do the right thing to protect their pride and joy.....  

Edited by mikal, 24 November 2016 - 02:41 PM.

[Dusky]

This might sound naive, if so please ignore my comments.
 
If you are on a tight budget and having no issues currently, why not just keep driving the car until when/ if a problem arises? At worst you'll have to get the head reconditioned sometime and replace the valve seat inserts then? Valve seat recession won't damage the engine itself as far as I know, just gradually reduce it's performance?. I can't visualise anything dramatic happening if you do nothing.
  

There are No inserts from standard. Machining for inserts can leave you with an unusable head when it cracks or you Discovery a hole when machining,like AC recently did.
You can lose performance quite quickly and Be left stranded near the road ,or without your everyday car.

As far as i know asditives basicly Just add a dissimilar metal like lead once did,just not as (Officiallyunhealthy as lead.
They certainly do work. For fun we used 2 almost identical minis in a local competition, one with and one without additive. At the end of the season the one without additive wasnt too pretty on the inside. I should Have pics somwhere

Edited by Dusky, 24 November 2016 - 02:34 PM.

[carbon]

+1. Would not recommend running any car in a way that you are expecting to break something before fixing it. Could end up costing a lot more in the long run.

 

Here's a useful summary of different additives used in petrol for valve seat protection: http://www.classicra...tutes_facts.pdf

[Spider]

This might sound naive, if so please ignore my comments.

 

If you are on a tight budget and having no issues currently, why not just keep driving the car until when/ if a problem arises? At worst you'll have to get the head reconditioned sometime and replace the valve seat inserts then? Valve seat recession won't damage the engine itself as far as I know, just gradually reduce it's performance?. I can't visualise anything dramatic happening if you do nothing.

 

I might be completely wrong on this, comments welcome (AC, where are you?!)

 

Cheers

 

Michael

 

PS: As a Petroleum Chemist I'd love to know what the formulation of the additives are and what/ how they claim to work. I'll do some research. I'm very skeptical when it comes to "additives", particularly the claims made by the manufacturer/ supplier/ seller. Most of the stuff is snake oil.... 

 

Edit: Example...

 

I had a quick read of the article in this link:

 

http://www.classiccars4sale.net/classic-car-how-to-guides/restoration/a-guide-to-unleaded-additives 

 

Most of it is poorly written rubbish, unsubstantiated garbage and they chop/ change the topic talking about valve seat recession in one paragraph, than about boosting Octane ratings in the next. I'm an expert and found it a painful, error ridden, confusing article designed to to scare the average punter into buying their miracle cure all product if they care enough to do the right thing to protect their pride and joy.....  

 

As Dusty and Carbon have said, not at all a good idea to keep driving if you value the head.

 

As the Rocker Clearance is lost due to seat erosion, it will get to a point, and fairly quickly once erosion starts, where the Exhaust Valve will no longer seat with any real pressure on it. This will lead not only to a loss in performance, but also burning of the exhaust valve and a fair chance of cracking the head.

 

I'm no chemist, but isn't TEL that the refiners used to add to Oil just an additive?

 

I'm of no doubt what so ever that there are snake oil additives out there but I also believe there's proper ones too.

[limby2000]

The cheapest route by a long way is to pick up an unleaded head from a 89 onwards. Ive personally sold 2x, one on here and the other on ebay and they both went for under 40 quid.

[jabos7]

Many thanks for all the input!  As I'm down on compression and testing points to the rings, I need to tear it apart and that makes

an unleaded head more worthwhile than than an additive or the 100LL avgas I was pouring into it.

 

So, from the earlier replies-   with the head off, what visual clues would tell me if someone already put in hardened valve seats?  I

can't think of anything that would be evident, just by looking at it.  Ideas?

At the great deal of 40 quid I'd just buy a used one if someone was willing to ship it to the US.  Otherwise I'm going to have to buy

one from one of your big UK suppliers.  I can't run mine through a machine shop here for what a new one + shipping would cost!

Is it possible to positively identify an 1989+ head by its numbers?  thx--J

[mikal]

Hi Moke Spider,

 

Just reread my post and it did turn into a bit of a rant. Was too late at night and bad mood didn't help..

 

1. I had no idea the leaded heads had NO valve seat inserts, Lesson learnt, thanks!

. Even Octane engine cylinder heads, a 70 year old design, have them! Became adept at changing them out though very rarely required. I never noticed a VSR problem with these engines after leaded fuel was phased out even though they are constantly detonating when testing fuel. Mind you they only operate at 500 or 800 rpm (2 types of engine, RON and MON) and are built like brick outhouses. I guess the valve seat inserts are made of stern stuff...

 

2. When I was talking about the additives themselves, I really meant the additive packages available. You're right about TEL (Tetraethyllead) which is a chemical added to boost the octane rating of a particular fuel. A beneficial side effect was that is was found that lead sulphate by products produced in the combustion process, deposited on the the seats creating a cushioning/ protective barrier reducing VSR.

 

3.The Octane boosting products commonly available do work but are usually 99% Toluene, Xylene or similar (often used as paint thinners) that have VERY high Octane numbers, typically over 120 RON. On a cost per litre basis these octane boosters are extremely expensive. Better off to buy a 4L tin of Toluene or Xylene at a fraction of the price and do it yourself. (Add it neat, say 5%, don't spill it on the paintwork!) and achieve the same result much cheaper. My friends in Bali having detonation issues with their Harleys and even road cars (particularly driving up hills under load) did as I've described above and problem solved. At the time (5 years ago?) you could buy 4L of Toluene or Xylene at the hardware shop for about $10 Australian...

 

We won't talk about the charlatans who peddle the lumps of metal you drop into your fuel tank and hey presto the Octane rating of the fuel increases via some mysterious means! I met one such chap at a motorbike show once, he couldn't/ wouldn't  answer my questions and so I offered to do some lab testing for him (I operated, maintained and overhauled refinery Octane engines for many years). When he heard that he refused to sell me a sample!

 

Cheers

 

Michael

[Turbo Phil]

The inserts are usually easy to see, especially if they're not factory fitted. A lot of machine shops seem to fit seats where the ID doesn't match the throat diameter at all, often hanging over the throat by 1mm or so. The factory inserts are a much better match but still visible, just clean some of the carbon from the throat and you can usually see the edge of the insert about 6mm down.

Phil.