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MG MGB Technical - Rocker Covers

'ello all,
i have a '79b daily driver that i'm rolling out for the season. being unable to fund repair of the rockers (rust thru outer sill on dvr side, bubbles on pass. side),i'm looking at using the moss stainless steel rocker covers. aghast as i am at using 'flash' instead of actually fixing it, i still would like to stop the rust at this point, and add any structural integrity that i can with only normal hand tools and the help of my 3 & 5 year old assistants.
exspanding house insulater 'great stuff' has been suggested as a way to fill the length of the rockers after blowing them out. this would keep out any further wisconsin water/salt/sand. i'm also looking for a way to seal the covers to the b.
opinions or suggestions? (my beautiful bride has declared selling an assistant is a no go)
thanks,
brady
brady

Brady,

I think you should check the archives, but I am quite sure there were many objections to using great stuff. I think the clean up of this material will take a long time when it is time to do job properly. Also it might trap more water, hastening the corrosion problem.

Maybe fiberglass and paint and lots of rust preventing oil afterwards, with monthly treatments to retard the corrosion. That is how I handled Volvo 240's in the Canadian winters.

I think in the long run there is only one way and bite bullet to do it right. I think if you subtract the cost of the stainless covers and find out how much the job is net.

Maybe the experts will have sometime more to add.

Shareef
Shareef Hassan

Hi Brady - if your main goal is to add structural integrity, I don't think you'll get any benefit from the stainless rocker covers - they will only cover the rust. The actual rockers are a 3-part member - you see one part inside the car being the rail running from footwell to rear arch, another part is the outer rocker cover which actually dives under the front and rear fenders and reaches to the front and rear wheelwells, and the third is called a castle rail, which is hidden in between the aforementioned parts. The castle rail has triangular shapes punched into it to add to its rigidity. If you have a hole in the drivers side, you likely have a fair amount of the castle rail missing also. You can check that by putting an allen key into the drain holes and attempting to spin it around - if the castle rail is there, it won't turn all the way around. That being said, the MGB is further supported by the transmission tunnel, and as such can remain quite rigid despite a fair amount of rust damage in the rockers.
I agree with Shareef - great stuff may occupy the space inside the rockers, but will likely trap more moisture and speed the rust process. Also, when it comes time to do the job right, it may be tough, maybe even toxic, to remove effectively.
If I were you I would treat the insides of the rocker periodically with a rust inhibitor via the drain holes in the underside of the rockers to preserve what rigidity you have left, and if you want to improve the appearance of the rockers, put on the stainless covers, and do the job properly when finances allow. But in the meantime, bear in mind that rust has weakened your car to a degree, large or small I'm not sure, and the covers will do nothing to improve that. Keep that in mind when giving the "assistants" rides also.
It seems to me that replacing rockers on an MGB is like changing the timing belt on modern cars - has to be done every so often. Its almost like periodic maintenance!

Erick
Erick Vesterback

Erick,

The vertical central panel with the triangular pressings is the diaphragm - the castle rail is the heavy duty channel under the floor!

Brady,

Don't waste the money on covers - use it to have the existing outer panels plated to repair the corrosion.

Don't fill the voids with foam - it will accelerate corrosion - instead, once the outers are patched up, spray inside with Dinitrol or another thin cavity sealer - even engine oil diluted 1 to 1 with paraffin - to arrest further corrosion.
Chris at Octarine Services

I don't know...I've seen a few filled with foam...and one which was restored later and totally torn apart showed no detrimental effects in the rocker caverns...It appeared the foam stopped the rust and did not asborb moisture...
pete

The main downside of foam is the clean up when you go to do the repairs later. It has to be removed entirely and if not melts and gums up grinders, sanders, and causes vast quantities of smoke if too hot. I did spray some of this stuff up inside a footwell cavity on my midget and so far it seems to have stopped the corrosion in that area for almost 8 years now.
I'd try an air sprayer and some chemical rust converter containing Phosphoric acid. Just reach in through the holes or drill a new one if necessary and spray the entire inner surface with this stuff. It won't add any strength, but it will stop the corrosion until you can repair it correctly and isn't a problem working with later.
Bill Young

This thread was discussed between 31/03/2007 and 02/04/2007

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