ausmini
https://www.ausmini.com/forums/

The good and the bad of an unleaded head conversion.
https://www.ausmini.com/forums/viewtopic.php?f=2&t=14225		 Page 1 of 2
Author:  Bromley [ Thu Dec 22, 2005 1:27 pm ]
Post subject:  The good and the bad of an unleaded head conversion.
The article in the first publication of TME tell us that the unleaded head conversion is a good thing to do if you are rebuilding an engine. In fact most people here on ausmini have suggested the same thing.

I have heard though, that the conversion is not something that should be done. Why? because if you were to overheat the head there is potential for the seals to fall and cause major damage to the engine. Also been told that the cost of the hardened seals make the unleaded conversion impracticle compared to the cost of just using a product like flashlube.

I know many of you have the unleaded conversion and would like to know what you think, as I am at the moment considering what direction to take with my own engine rebuild.
Author:  Lillee [ Thu Dec 22, 2005 2:17 pm ]
Post subject: 
I've had it done, no complaints, even when really hot.

I think the seats falling out when overheating is an old wives tale. The seat is pressed in and when metal heads up it expands so it gets tighter not more loose? I've never understood that argument? or am I missing something?
Author:  kazjim [ Thu Dec 22, 2005 2:45 pm ]
Post subject: 
Actually, it is ESSENTIALLY True, but the heat you'd need to get to is about 400+'C . . . If your engine is that hot, you've got bigger problems than that....

The Coefficient of expansion of the Cast-iron head is actually higher than that of the seat (Usually Through Hardened Steel) and so if the fit isnt just right, it can drop out under the right circumstances....

Not something I worry about myself .... got hardened seats in my 12G1316 head....

J
Author:  Boostedmini [ Thu Dec 22, 2005 3:16 pm ]
Post subject: 
I was thinking of having seats fitted by GR when he was doing my mods but he said no as it was turbo and it woud get very hot in the combustion chamber, so i said ill just stick to my flash lube and he said no just use some 2 stroke oil in the fuel now and then.

I have heard this before for diesel engines due to the crap low sulpher fuel we have which does not lube pump and they then shread out.

hhhmm interesting i know
Author:  drmini in aust [ Thu Dec 22, 2005 3:38 pm ]
Post subject: 
kazjim wrote:
Actually, it is ESSENTIALLY True, but the heat you'd need to get to is about 400+'C . . . If your engine is that hot, you've got bigger problems than that....

The Coefficient of expansion of the Cast-iron head is actually higher than that of the seat (Usually Through Hardened Steel) and so if the fit isnt just right, it can drop out under the right circumstances....

Not something I worry about myself .... got hardened seats in my 12G1316 head....

J

Actually most unleaded inserts (Rover ones, anyhow) are austenitic steel and have a higher expansion coefficient than the head does.
If properly fitted (shrunk in, not pressed) they will not come out. But there are people out there that do not fit them properly. I have heard of people fitting them with a hammer and dolly... :shock:
Insert has (or should have)approx .004-.005" interference fit... and if it does it is in there for keeps. :wink:
Author:  Bromley [ Thu Dec 22, 2005 3:47 pm ]
Post subject: 
I am going to be telling my engine bloke this. Thanks!
Author:  drmini in aust [ Thu Dec 22, 2005 3:49 pm ]
Post subject: 
When I got them put in Barney's 1293 motor (12G1316 head) the toolmaker that did it for me warmed the head to 200C and shrunk the inserts with liquid N2... :shock:
They practically fell in... :wink: and no way will they come out! :lol:
Author:  Steve [ Thu Dec 22, 2005 5:01 pm ]
Post subject: 
Not necessary

Anyone doing your head will and should still recommend lead replacement after getting inserts.

steve
Author:  J_A_M [ Thu Dec 22, 2005 10:37 pm ]
Post subject: 
The beauty of having the conversion means you can forget about Flashlube or similar.

Just one less thing to worry about 8)
Author:  gafmo [ Thu Dec 22, 2005 10:41 pm ]
Post subject: 
Mine had Hardens put in 5 to 6 years ago...the heads been off a few time and all is good inside.

no I don't a lead replacement..sorry Steve :wink:
Author:  manofaus [ Fri Dec 23, 2005 9:06 pm ]
Post subject: 
austenitic stainless steel
higher thermal expansion (change in length vs change in temp)
lower heat transfer rate (movement of heat through the material)

like when you piss borrowed beer in a urinal when its cold and it goes 'bong'
Author:  drmini in aust [ Fri Dec 23, 2005 9:17 pm ]
Post subject: 
On a 1275, if the exhaust seats have sunk heaps from years of running plain unleaded etc, fitting inserts there is the only practical way to save the head. :wink:
If only minor recession, you can fit 31mm exhaust valves instead. Then run Flashlube, 2 stroke oil or whatever. 8)
Author:  Dylans Clubby [ Sat Dec 24, 2005 12:03 am ]
Post subject: 
wasnt it posted on here AGES ago that an unleadsed head is a good conversion if you are building, but you still need flashlube to lubricate other parts of the motor?\

we put an unleaded head on my new motor, is there any special care it needs? or can i just run on a 98 RON and all will be sweet?
Author:  drmini in aust [ Sat Dec 24, 2005 4:58 am ]
Post subject: 
Dylan's Clubby wrote:
wasnt it posted on here AGES ago that an unleadsed head is a good conversion if you are building, but you still need flashlube to lubricate other parts of the motor?\

we put an unleaded head on my new motor, is there any special care it needs? or can i just run on a 98 RON and all will be sweet?

I run Barney with no Flashlube now. But as well as genuine Rover exhaust inserts, he has the latest valves from UK with chromed stems- designed for unleaded.

If running standard valves, Flashlube is a good idea- it provides some lube for the inlet valve guides. Unleaded fuels all have so much solvents that their lube properties are non-existent.
Author:  Keith Calver [ Sat Dec 24, 2005 5:22 am ]
Post subject: 
Genuine Rover inserts for the exhausts have been copper-berylium for many years now. They are excellent for street motors. I have no idea what 'flash-lube' is, but did piece on unleaded thing many years back that is on my site under Calver's Corner (www.calverst.com). I tried a whole pile of lead substitutes years back and only a few were of any use.

I know my mate Mr Russell doesn't like inserts over-much, but I have been fitting them to every head I've done for MSC and others for the past 15 years.Never had an insert fall out. And I also fit many race heads with inserts (on occasion have fitted to both inlet and exhaust) and never had a problem.

The issue seems to be fiting them properly. Any self-respecting and capable engine re-conditioner MUST be able to do it these days. I bore the holes ot as Kevin has stated to 0.004-0.005" interference fit and squeeze them home with a press. Last year alone I must have fitted 800 inserts. No worries.

For my money - I'd fit inserts. KC
Page 1 of 2 All times are UTC + 10 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/