4371505 Cyl. head standard valve seats, are they OK for unleaded fuel ?

Road-race engines and ancillaries - general discussion
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Kerem1967
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Joined: December 26th, 2012, 9:08 pm
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4371505 Cyl. head standard valve seats, are they OK for unleaded fuel ?

Post by Kerem1967 » August 24th, 2021, 10:14 am

Dear Friends,

Are the exhaust seats OK for unleaded fuels in the mentioned cylinder heads ?

Regards
GC_90

Wal
Posts: 40
Joined: July 2nd, 2006, 7:22 pm
Location: Denham, Bucks, UK
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Re: 4371505 Cyl. head standard valve seats, are they OK for unleaded fuel ?

Post by Wal » August 24th, 2021, 7:17 pm

Kerem,
4371505 is most likely a 131 or 132 head, possibly a Monte Carlo.

The short answer is the standard exhaust seats for these heads are almost certainly not suitable for unleaded.

If original they are likely to be cast iron, there are some variations, though it is possible they have been replaced by a suitable alternative by a previous owner.

More detail here:
viewtopic.php?f=1&t=278

Regards,
Steven

Kerem1967
Posts: 32
Joined: December 26th, 2012, 9:08 pm
Contact:

Re: 4371505 Cyl. head standard valve seats, are they OK for unleaded fuel ?

Post by Kerem1967 » August 26th, 2021, 5:56 pm

Wal wrote:
August 24th, 2021, 7:17 pm
Kerem,
4371505 is most likely a 131 or 132 head, possibly a Monte Carlo.

The short answer is the standard exhaust seats for these heads are almost certainly not suitable for unleaded.

If original they are likely to be cast iron, there are some variations, though it is possible they have been replaced by a suitable alternative by a previous owner.

More detail here:
viewtopic.php?f=1&t=278

Regards,
Steven
Hi Steven,

Thank you very much.
The head I am going to use a brand new one so the seats are OE factory seats. And most probably, they are not for unleaded.
I will probably not prefer to change the ex seats but use a lead additive. I am not sure about the longevity but as it will not be a daily driver, we might be able to get away with it. What do you think?

Regards
Kerem
GC_90

Wal
Posts: 40
Joined: July 2nd, 2006, 7:22 pm
Location: Denham, Bucks, UK
Contact:

Re: 4371505 Cyl. head standard valve seats, are they OK for unleaded fuel ?

Post by Wal » August 27th, 2021, 11:30 am

Kerem,
Personally if it where my engine and I already had the head off I would change the exhaust seats to unleaded, just because the head is already off and why not do the job once.

I have no bad experience with lead substitutes and used it in a Triumph Spitfire I had for a while till I took the head off and got it converted. It was an occasional drive and not raced.

However, the one doubt I have is if it is a new head then the seat won’t have had any of the residue of lead protection from past running and this might make them more susceptible to regression even with the substitute. But this is only a view I have no evidence.

Regards,
Steven

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