22 replies to this topic

[adam c]

This is another job that i plan to do myself but may end up taking it to the proffesionals.
I have two heads;
An old one that has had all the valve springs removed (the valves are still in place). I'm not sure if its unleaded - how do i tell?? Theres no carbon on it so i presume its been cleaned so it might be worth a try..

I also have the one that came off the engine i took out at the weekend, its intact and i've seen the engine it was on run but its totally carboned up and is supposed to be a stage 2 but it looks no different from the other one?? I also don't know if its unleaded so also need to now how to tell??

If I want to recondition it I preume i should re-grind the valves (I have done this succesfully in the past on a stationary engine) but should i do anything else to it?? Will i need any parts?? How could i remove all the carbon - i think it may have built up so much as it was a 998 engine with a hif44 carb so it probably got pretty choked??

I want to get the car on the road pretty quickly and can't really budget for a reconditioned head and also want to do some work on the engine myself so thought this might be a good thing to try. Any suggestions would be great....

[Bluemini]

To get rid of the carbon on the valves, put them in a drill and switch it on, with a stanley blade take the carbon off. Once done, use some fine sand paper to polish them up, then lap them back into the head using valve grinding paste and sucky stick thing you get with the paste.

As for modding the head, check out the bible for diagrams and instructions.

[adam c]

Yeah have read the bible, the pics are good but the writings a bit confusing. Am thinking for now of leaving it standard, just want it to be in good condition and unleaded.
Cheers Rich :grin:

[dklawson]

You asked how to tell if the head is set up for unleaded gas. Look for hardened inserts for the exhaust valve seats. If they are present you are ready for unleaded gas.

If the heads are old you should pay attention to the condition of the valve guides. These are only supposed to have about 0.0015" of play to allow for expansion when hot. The guides in my old head were severely worn and had closer to 0.020" of clearance with a lot of taper. It is an extreme waste of time to try and lap valves into a head with worn out guides.

To remove the carbon from inside the ports you can mask things off and sand blast or take the whole head to a machine shop and ask them to hot tank it, which will remove all residue... inside and out.

[adam c]

Cheers...what will hardened inserts look like??

[Bluemini]

They are like standard ones, but if you put your finger in the valve hole and run it around just under the seat you'll be able to feel a lip were the seat has been pressed in, unless it is unleaded as standard that is.

You can still run it on u/l fuel without converting it as long as there is plenty of carbon build up one it. For something like every 40,000 miles you do with full fat fuel, you can 10,000 on unleaded. Have a look at Keith Calvers page on it at the Mini Spares website.

[adam c]

Cheers - i think i may be in luck as i stripped the head today (the one that was fitted to the car) and found that there was virtually no difference between it and the standard one and it has obviously been recently fitted as it was painted red. I therefore presume that it may have been fitted as it is unleaded. This head also has virtually no play in the valve guides and the seats look very good and almost may not need lapping. I also has slightly different shaped valve guides so i'm hoping its unleaded but will have a better look later..
When re-assembling are there any parts i need?? The stem seal thingys??
Cheers :grin:
Some pics....

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[adam c]

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[adam c]

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[dklawson]

If there is no play in the guides that is great news. I couldn't tell from your photographs of the ports whether or not there were inserts. When you really get into cleaning it will be obvious if there are inserts as they will have a different texture and (typically) color than cast iron. In the U.S. those of with older "leaded" cars can buy lead substitutes for the gas.

KC may be correct about 40k miles of lead protects you for up to 10k of unleaded driving. However, we haven't had leaded gas in over 15 years. There aren't many engines here that haven't been driven 40k miles in 15 years. On my head the valves were badly recessed into the head from years of operation without service (or lead). I replaced the head with a later 12G940 casting with the inserts and have been very happy with its performance.

If that head is as good as it looks in the photographs I'd just clean it up, lap the valves back in (don't mix them once you lap them in... mark them for position). Then paint it and reassemble. Yes, you'll want new seals. The later type seals with the garter springs should fit and hold up better than the "un-sprung" solid rubber seals. The seals are usually placed only on the intake valves if the guides are new or tight. On an older engine with a little wear or play in the exhaust guides you may consider putting them on the exhaust guides as well.

[siggy]

Doug I have not seen 'O' seals in head set in the UK for some time now.

When gringing the valves in make sure that NO paste goes onto the valve stems. Use 1 rag for cleaning the heads and a 2nd one for cleaning the stems. While gringing in I spray a little WD40 on the stems to lub them.

Siggy

[dklawson]

Siggy, if I implied "o-ring" seals as used on the very early engines that was not what I meant to do. Thanks for pointing that out.

What I was referring to is that the "cheap" seal has no garter spring on its neck opening. Those used on the 1275s (like S engines) have garter springs on the seals to maintain their performance longer.

[siggy]

Doug It was more for your information. the only seals I have seen have been the ones with the garter springs.

Siggy

[dklawson]

Thanks Siggy. I have some of the seals without garter springs among my spares along with Rover ones with the springs. At the moment I am running aftermarket Viton seals with garter springs. Supposedly these hold up even better than the Rover ones with springs but only time will tell if that is true.

[siggy]

Are they the ones off Todd, ADO17?

Siggy