HELP: silly question:maybe i'll have to correct my ebay data

[el-saturn]

i'm currently selling a tc head and have made the following claim: the valve seat inserts are adequate for BIG VALVES, having 41,33mm (1,625" is less) - my own has 40,5mm inlet valves so i'm pretty sure (or feel safe) i didn't lie OR DID I ??????? - i would immediately change the false info! MANY THANKS sandy

[stevebroad]

Hi Sandy

1 thou over 1.625" is rather tight but, IMO, acceptable.

You might want to revise the listing, as it states postage as 6 pounds

Being a pedant, the UK puts the pound sign in front of the amount

Have the valve guides been changed? Any gas flowing?

Steve

[el-saturn]

thanks steve! no gas flowing etc.. guides look nice and i think the seats can also be modified / lapped for the big valves. this head came off of a running engine! cheers sandy

[rgh0]

Normal seat inserts for 1.625 in / 41.27 mm big valves for racing are around 43 mm OD. With the valve sealing surface on the extreme outer edge of the valve and around 1 mm wide and the seat and port bored to around 39.3mm. This leaves around 2 mm wall thickness on the seat insert.

To much bigger seat OD and you get tthe seat insert OD intruding into the spark plug threads, to much smaller and you get to thin an insert wall thickness with the 39.3 mm seat bore.

Many heads have had oversize valve seats fitted during rebuilds to achieve the right interference fit, the original inserts were around 41.5 mm outside diameter I believe.

cheers
Rohan

[el-saturn]

that's what i got, as the combustion chamber and the inserts aren't measurable (i measured 41,3) more accurately! thanks rohan - i, btw, got the sealant: it doesn't say No. 3 though (but 80017 is stated) -- is this the same product??? thanks sandy