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MG MGA - MSX Crossflow head problems MGA

Hi all
I am comming back with a new tread title

As you know I built a MSX crossflow head on my MGA engine

List of the encountered problems:

- Inlet manifold to long , cannot build the original airfilter on the carbs , had to shorten the manifold

- Heater control valve has reversed function , when you want cold you have warm ... not tragic and easy to cure , you have to replace the top of the valve (the mecanism) whith your old one if it is in good condition

- More important: havy blue smoke at the exhaust !!! the old castiron head didn,t smoke even if 50 years old !!!
I checked all ( compressions, etc...) and opened the engine again , then I had a closer look to the valve springs and discovered one then another broken O ring seal between spring and valve stem !!! I dismanteled the valve spring mounting and it was true !!! 3 from 4 Oring seals where broken (dryed out? or to small for the stem diameter?) brand new !!!
I also wonder if 0.08mm is the good clearence for the valve stems?

- The moulding seems not to be very "symetric" if you have a look in the inlet ports the bronze guides are not included by the same lenght in the casting

- Valve springs are rusty wich is not good for longlife

I will replace the sealings and try again

Please MR or MRS Moss check the quality system of MSX
there is a lot to do !!!

I am disapointed


P Windenberger

valve guides pictures


P Windenberger

other valve guide in the other inlet port


P Windenberger

and rusty valve spring


P Windenberger

The original type O-ring "seal" doe not seal the top of the valve guide. It is supposed to be installed inside the spring cap just below the split cotters, and within the square groove of original type valve stems (with Type-A cotters). This is intended to stop oil from running down from top of the spring cap through the split cotters and down the valve stem.

The same original setup (Type-A) also used the oil deflector collar to inhibit oil splash from the sides getting to the top end of the valve guide. Fairly early in MGB production the oil deflector was deleted, and the spring cap was revised with a slightly larger pilot diameter for the inner valve spring. Early and later spring caps can be interchanged, but the collar will not fit on the later spring cap. All of this is related to the Type-A valve stems and cotters.

Your pictures show the later Type-B valve stem with round keeper groove. This was never original on the MGA or early MGB, but was standard on later MGB. Split cotters and spring caps are different for this setup. The oil deflector collar cannot be used with this spring cap. Additionally the O-ring seal can be somewhat difficult to install. Where it was originally nested in the bottom of the square keeper groove it will now be severely squashed below the cotters between the spring cap and valve stem.

Installing the O-ring on the valve stem below the spring cap serves no useful purpose. With no O-ring and no oil deflector collar, oil splash is free to access top end of the valve guide. Your 0.08-mm clearance (slightly more than standard) is good for bronze guides, but it may cause slightly increased oil consumption. Even then I wouldn't expect it to be the cause of smoking badly, so there may be some other undiscovered issue in play here.

I would recommend installation of umbrella seals on the valve guides to positively seal against oil running down the valve stems. This is especially useful on the intake guides where there is constant vacuum in the ports below. For iron guides it is common practice to install seals on the intake guides only while allowing a little oil into the exhaust guides. Bronze guides are self-lubricating, needing no oil, so it is good to install umbrella seals on all eight valves. Use of umbrella seals with standard OD size on valve guides precludes use of the splash collar (not an issue here).

I suppose it is worth the effort to install umbrella seals, then reassemble the engine and drive it to see if the smoking problem may be banished. If it still smokes, then there may be a problem with piston rings not sealing well against cylinder walls. The next worst speculation (and not very likely) might be a leak in the head gasket allowing oil from the port at LR corner of the head to get into #4 cylinder. The worst fear is that there may be a crack or casting defect in the new head allowing oil intrusion into a combustion chamber. You might need a casting pressure test to find that problem. Of a dye penetrant test might disclose a casting crack.



Barney Gaylord

For the original iron cylinder head the intake and exhaust valve guides are different length, because the ports are different shape in the air flow path. Top end of the guides (below the spring cap) would all be same height with the bottom end of the guides (inside the port) being different height. As long as the guides do not interfere with motion of the valves they will likely be okay as is.

The MSX castings do have a number of quality problems, like flat floors, short radius turns, sharp corners and casting flash. The casting can benefit from a substantial amount of labor time for clean up and porting by someone who knows what it's all about. Apparently there was not enough time or concern during design development of this part, so quality and function leave a lot to be desired.

The small amount of surface rust on your valve springs may be of no consequence. For myself, and/or for street use, maybe wire brush or shot peen the springs and put them back in service. If you were building a no-holds-barred and no-expenses-spared race engine to run at abnormally high speed, then maybe new springs would be justified.
Barney Gaylord

Woawww

Answer from "Sir Barney Gaylord" itself :o))
I am very pleased to come in contact whith you
I don't know all your website inside out but it's a bible for me and all my MGA friends, thanks a lot for your work and time and the further help...

Pierre Windenberger from France
P Windenberger

Hi,

I had same problem with oil and I have to change oil seals on all valves. I used that type of seals - http://www.cambridgemotorsport.com/MGB-1800-Valve-Stem-Oil-Seal.

Regard quality of MSX head was written a lot so you can find more on that link http://www.flowspeed.com/rates.htm - select Articles and follow link on the bottom of the page.


toni
Toni Kavcic

Well Pierre, I see you have have had the answer to your oil burning problem from the "Master" himself.

Its encouraging to know that I had the same reasons for your problem in mind as Barney, the difference is that he also can tell you how to fix it!
What would we do without him?

I was suprised to see the surface finish inside the ports, I would expect that a smoother finish (not polished) would help the gas flow quite a bit.

Let us know how things go

Colyn
Colyn Firth

Yeah, I guess I could have listed the links to articles by Sean Brown, all about porting and polishing and his experience with the MSX head.
http://mgaguru.com/mgtech/power/pp401.htm
http://mgaguru.com/mgtech/power/pp402.htm
http://mgaguru.com/mgtech/power/pp403.htm

Barney Gaylord

Further comments on this head after dismanteling:
very bad symetry of moulding , I think if you have 100HP you may have 60HP comming from the cylinders 1 and 2 and the other 40 HP produced by the 3 and 4 or inverted or variable
Before I saw that I was disapointed now I am very disapointed !!
Where is the Quality assurance manager at MSX ?
Is there a quality system at MSX?
or is the MSX philosophy: all what's comming out is good enough to be sold? ?
or does the X from MSX means Expedious-end-control?

On the picture you can see that the highness of the aluminium supporting the valve seat ring is not the same for the rear and front inlet ports (Due to bad form of the moulding core? or worse due to displacement of the moulding core before or during moulding?) perhaps you have also the explanation of the two different "shapes" of valve guides bossages

I think that it could have also an influence on metal thickness between port and cooling circuit !!! How thick is it now ? 1mm? 2mm? 0.1mm? 10mm ? And if problems occurs what is the resort?

MSX Manager : any explanations? For this price I can wait a little ...


P Windenberger

You are not alone in your criticism of poor quality:

http://www.flowspeed.com/msxpost.htm
http://www.flowspeed.com/msx-tribute.htm
dominic clancy

This thread was discussed between 09/05/2010 and 12/05/2010

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