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MG MGA - Unleaded to leaded

I have just seperated the cylinder head from the main body of the engine (which is an MGB 1800 engine)and am about to take a part with a view to getting it converted for unleaded fuel. If you get the valve seats hardened what does this mean do you need therefore to get the valve sleeves and stems hardened too.

If so why not just but new or do you need to get the actual head hardened.
A Aitken

You will want to check with the person doing the conversion,but usually they install only the exhaust seats,better exhaust valves and better valve guides. They machine out the old seat and interference fit a new hardned one.Look here under item 61 and click for more info-http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=29210
I cant find them but they used to sell the hardned seat also.On something like this tho I would have the one doing the work order they parts they are used to using.Another alternative is to get a head on an exchange basis,http://www.mgcars.org.uk/peterburgess/ Hope this helps,Gary
gary starr

As Gary says you need to get hard exhaust valve seats fitted by an engine reconditioner and then get them to cut the seats to the three angle configuration to get best gas flow. The valves and guides should be OK provided of course that they are not excessively worn.
Iain MacKintosh

Hi. If you are going the no lead head route, then you definitely want to have hardened valve seats installed, use stellite exhaust valves, and use bronze valve guides. Note that the bronze valve guides will need to be reamed a few thou oversize, since they expand more than stock guides, and will seize a valve stem otherwise! A no lead head using these components will be very reliable, and last a very long time. The 3 angle valve grind is a good idea! While the head is off, you might want to do some light porting and polishing. You dont want to take off very much metal, rather, you want to remove casting marks inside the ports and combustion chambers, and generally smooth the rough spots in these areas. You can similarly clean up the inside of the intake manifold. Removing the rough spots and casting marks will likely improve engine breathing a bit, which should help engine performance at least a little. Cheers, Glenn
Glenn

The standard exhaust valves on the B are well capable of being used on unleaded fuels so don't need changed. Bronze valve guides wear quicker than steel and on the basis that modern engines use steel guides then the standard B guides are more than adequate for the job with no risk of seizure.
Iain MacKintosh

There is almost certainly a difference between modern "steel" valve guides and the standard iron guides used on our vintage MG engines. I can state with certainty from l-o-n-g mileage driving experience that the stock iron guides do wear a lot (well beyond factory tolerance for good alignment within 100,000 miles), and bronze guides may wear very little indeed.

I have a cylinder head that I had rebuilt in the early 90's with bronze guides. It is now running on a second engine and has accumulated about 150,000 miles on the bronze guides. These guides are in very good condition and will most likely run a quarter million miles with no problem. I will never go back to iron valve guides.

The same head has hardened steel valve seats for all valves. The intake seats looked like new afer 100,000 miles and needed nothing for continued service. The exhaust seats were still serviceable after 100,000 miles, but slightly worn. I touched off the inside corner to narrow the land slightly back to 1.0 mm (0.040") before putting it back in service.

I drive the car with vigor for autocross and high speed trailer towing. I used to burn stock exhaust valves in about 40,000 miles to the point of mild compression leakage. First time around they got a standard valve job touch up. Second time around they needed replacing. When I installed Stellite exhaust valves with the hard seats all valve problems went away. I now do no valve work until the rest of the engine is totally clapped out and in dire need of reuild. At 100,000 miles the Stellite exhaust valves were worn enough to be noticable, but would likely run another 100,000 miles without service.

If you don't plan on driving the car more than another 50,000 miles in your lifetime, then standard valve gear works just fine, even using unleaded fuel, and you might replace valve seats only if they have a bad case of valve seat recession.

If you plan on putting another 100,000 miles on the engine, certainly install hardened steel valve seats for the exhaust valves.

If you plan on driving it hard or running it more than 100,000 miles, I heardily recommend Stellite exhaust valves and all hard seats.

$.03,
Barney
Barney Gaylord

FWIW, I had bronze liners installed in my valve guides.

http://www.hastingsmfg.com/Service%20Tips/valve_guide_liner.htm

http://www.goodson.com/technical_support/tech_library/installing_clasic_liners.php

Supposedly, the thinner sections allow tighter clearance. They have worked well for me.

The MGA is dirt-easy to replace guides so the price and process was similar to full guides.

Their real value is on older aluminum heads. To get the guides out, you need to heat the head which can cause warping due to uneven heating. Even with heat, you can ruin the guide bore. For old Jags, bronze liners are a godsend.

Bill
Bill Eastman

This thread was discussed between 16/10/2006 and 28/10/2006

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