MG Midget Forum

I have a spare 1275 head, thinking of getting it converted to unleaded. Getting conflicting information. It needs a complete redo anyway, been sitting 27 years and not reconditioned. Anyone know aprox cost and should I let local do it? Suggestions please.

Had one cleaned, magnafluxed, three angle valve grind and checked to be sure it was flat cost $325 as I recall.

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Iceman

Atlanta GA

71 MG Midget

62 AH MKII
67 Midget
71 Midget

Everyone says these engines have to be converted to run on unleaded. British Leyland saw the writing on the wall and ( I have read this I do not "know" this). I rebuilt my engine and did not do anything with the valve seats as the guy doing the head, a renown auto machinist, said this car did not need it. In the 8000 miles I put on it, I have only had to adjust the valves twice, the first time was minor, the second time was even less adjustment and some of the valves did not need adjustment, Do what you feel comfortable with. I run a Kent Cam with 10 degrees more duration but it does not open any wider. I don't know if that helps. A hardness test could be performed. Magnafluxing is absolutely necessary.

Thanks, I'll get the machinist opinion, the one I'm running was done aprox 7,000 ago with no further adjust, just checked and OK but I may have a slight exhaust valve leak on # 3. I thought i would get the spare one done right then swap them over.

it cost about $80 to $100 to put in 4 hardened exhaust seats. You do this to preserve exhaust valve seal, as cast iron exhaust seats do not hold up well to hotter unleaded fuels, and will pit up and lose seal, you can re-cut them in a valve job, but they will pit and lose seal in a short period of time, of course the owners may not know this unless they do a cylinder leak down test. I tell people no matter if your engine is bone stock, or full race, if you re losing valve seal, you're losing available power and economy.

Here I wrote up a tech post about this here. Post #80

http://www.mgexp.com/phorum/read.php?68,1828263,page=4


There's no real mystery here, of course some people, and some lazy machine shops don't do it, and try to explain it as not needed, well not needed if sub par performance, and valve leakage which can lead to a burnt exhaust valve is OK with you.

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Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com

If there a "point of no return" before the hardened seats can no longer feasibly be put in? The machinist I who performed the work for me had been established for making rock solid engines and was the best in area, his reputation was established by what he did and the results thereof. If he did not put in seats, it was not laziness,, also, this was a long time, and I wonder if more information would have changed his opinion (he is deceased now). As I have stated, 8000 + miles, barely any valve adjusting needed, there has certainly been no recession into the block. However, my trust in you, Hap, is such that if this starts to rear it's ugly head, I will take off the heads and have the seats installed. I may lie to my wife, and get the "Crossflow" head, as I have just found my second DCOE 40 Weber, and that would be the perfect opportunity to do this. Maybe the price will come down a bit by then. I do think if I was doing this now, I would have the hardened seats installed, why not.

People always talk about valve recession, but it is extremely rare, in the picture I showed from the linked thread above, that is the norm of what I see, not a rarity. Meaning I see heavily pitted exhaust seats, they are not recessed, just pitted and not sealing. So yes, if your machinist says this are not necessary, I would say IMHO, he is misinformed. We did cylinder leak down testing and see the facts firsthand, #2 and #3 exhaust valves fall off the quickest due to the shared port, and increased heat.

All the new aftermarket cast iron heads, like the MGB come with hardened exhaust seats, and of course all the aluminum ones do as well.

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Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com

My reason for concern is simple. I pulled the plugs to do a compression test to do an engine condition test for Jeff to build me a Distributor. # 3 was 168 #. 4 was 179 #. On top of that 3 plugs had normal brown porcelain, # 3 was as I have never seen before, white on one side of e porcelain and sooty black on the other 180°. My suspicion is # 2 is leaking thru the # 3 exhaust valve causing the weird combustion. Theories welcome. Car runs fine with plenty of power at this time but having a spare head I thought it would be wise to get it done properly before catastrophe strikes.

Sounds prudent. 66jalopy Thanks Hap, for a simple to understand answer.



Edited 1 time(s). Last edit at 2014-10-25 04:46 PM by CtMGDude.

I had hardened exhaust seats installed in my TR6 several years ago. A good portion of my use is long stretches of Interstate driving on trips and because of that I am really glad I had them installed. Why just exhaust valves? First they run much hotter than the intake valves. Second is that the seats can be a little larger in outside diameter. Third was that some of my exhaust seats were seriously pitted from pieces of the top rings making an exit. And fourth it didn't cost all that much for the piece of mind. And if both intake and exhaust seats are installed the web between then is either very thin or even broken through when machining the pockets.

Yesterday I was talking to the machinist that built my Midget engine in 2003. That was long before I bought the car. He told me that hardened seats were installed in the Midget engine and I confess to being glad they were.

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Tom Smith
1974 Midget
1976 TR6

I always have hardened seats installed on pre-unleaded vintage engines. It's cheap insurance! My local shop (a speed shop actually) does it well and it's like $15.00 a cylinder.

Well, machinest says head is good except exhaust seat on one cylinder, so all new inserts. Ordered new valves, springs and Payen gasket set from Hap. I think this is gonna be no more than $250.00

On the way home from machine shop lost more power. Took another compression test, 2&3 down to 90#. Head gasket blown between 2&3. By the way, wich instruction on the head gasket should I have obeyed, top up or turn it over for front to be front, I chose front to rear. Valve seat after head redone about 8,000 miles, yep I'm getting hardened seats.

I removed the little pipes that send the exaust to the rail, cut a nail off and inserted it in the hole, put a 7/16 20 bolt in the hole and cut it off, 2 1 1/4 bolts did all 4 holes, could have used one 2 1/2" for all four. This was for practice, do it again when head come back from machine shop.

Well, got the head back. One intake seat was bad from sitting and getting pitted from rust, so exhaust and intake new seats, bronze liners in the valve guides, replaced the brass plug with a screw in steel one, resurfaced head, $397.00, gulp! That didn't include the new valves, springs and gaskets, another $120,00. Put it on the car, sounds good, cranked right up! Now the electric fan decided to quit, AAAAAHHHHHH, new one on the way.