Timing cover design A motor 948

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niftyrodman
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Timing cover design A motor 948

Postby niftyrodman » Fri Jul 12, 2019 10:51 am

I have a weep from a timing cover, and I have a theory. Back in the 50s the oil was not as slippery as it is nowadays. Perhaps oils are sneakier. The spacing between the bolts seems to me a bit wide and although the elongated washers do compromise with that deficiency, nonetheless the fact remains that the cover is not clamped tightly enough. I can make a backing strip of steel plate to stiffen the face but maybe there is an aftermarket cover that is stronger.

Murrayminor
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Re: Timing cover design A motor 948

Postby Murrayminor » Fri Jul 12, 2019 11:44 am

I once used a modern oil in a Morris Marina and to say it leaked slightly was an understatement, I investigated everything to solve the leaks but when I reverted back to proper oil the majority of the leaks stopped.
I now look upon oil leaks as a rust preventative measure.
Proud owner of my first Morris Minor

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philthehill
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Re: Timing cover design A motor 948

Postby philthehill » Fri Jul 12, 2019 12:48 pm

BMC overcame the timing cover leak problem on early timing chain covers by fitting a separate stiffening strip (Pt No: 12A666) around the bottom of the timing cover.

Later timing covers were much improved as were the timing cover gaskets. Because of the improvements to the timing covers the stiffening plate was made obsolete but may be found on the likes of 'e' bay.


niftyrodman
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Re: Timing cover design A motor 948

Postby niftyrodman » Fri Jul 12, 2019 1:25 pm

Thought so. Its pretty obvious. Haven't got one in your back shed Phil? No matter I have a sheet of plate left over from a job I did and I can make one if necessary. Pretty easy but a nuisance. I do think its the later oils that escape easier than the old, exacerbating a flaw. Also I think the available gaskets are a bit sus. I think I will make my own out of a heavier piece of material. Saps restorers enthusiasm things like this.

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philthehill
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Re: Timing cover design A motor 948

Postby philthehill » Fri Jul 12, 2019 1:46 pm

I do have a 12A666 stiffening plate but not spare though.
The plate is 1.5mm thick and has three 1/4" holes for the three 1/4" bottom bolts and a 5/16" hole for the R/H bottom 5/16" front engine plate bolt.
To me it would make better sense if you fitted the later timing cover with lip seal and improved gasket.

I have used modern oils in my Minor and never had an oil leak front or back.


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Re: Timing cover design A motor 948

Postby IslipMinor » Fri Jul 12, 2019 2:45 pm

I use a 'modern' Castrol full synthetic oil in our 1380, and it does not leak from either timing cover or sump gaskets. I use a thin layer of non-setting gasket sealant, e.g. Hermatite, on the face between either the timing cover or sump pan and the gasket, and smear grease on the gasket where it meets the machined cast iron block faces. Same for the rocker cover.

The sealant looks after uneveness of the pressed steel components, and the grease makes sure that if you do need to remove the rocker cover, timing cover or sump, they are very easy to do, with no residual gasket to scrape off!
Richard



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Re: Timing cover design A motor 948

Postby niftyrodman » Sat Jul 13, 2019 12:45 am

First thanks phil for the design, and secondly thanks Islip for the hermatite tip, yes oil sneaks under the cork, and actually I was mistaken by thinking the felt timing cover seal was leaking, but alas it was the cover. I never got under to check just assumed it was, so when I pull the radiator out to get at the nuts on to fit the chrome top grille bar, I will deal with it. May I ask, what thread was originally in the front engine plate to fasten the cover. BSF? I might even go up a thread size and use socket headed bolts in the oil splash area, lower plated as well.

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philthehill
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Re: Timing cover design A motor 948

Postby philthehill » Sat Jul 13, 2019 7:23 am

The timing chain cover gasket is special oil resistant paper not cork https://www.ebay.co.uk/itm/GASKET-PAPER ... 2ZJN1nHEAQ. Cork will just squash out from under the cover flange and make the oil leak worse.
The threads holding the cover are 1/4" & 5/16" Unified National Fine (UNF). Increasing the size of the bolts is off no benefit. The original bolts are more than adequate.

Later timing chain covers had improved rigidity of the gasket flange and used a rubberised gasket paper.
See photo below for image of the improved timing cover flange. Note the raised 'worms' between the heads of the cap headed bolts.
100_1232.JPG
100_1232.JPG (1.49 MiB) Viewed 219 times


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Re: Timing cover design A motor 948

Postby niftyrodman » Sun Jul 14, 2019 3:15 am

Sorry Phil. The mention of the non hardening sealant brought up an image of the cork rocker cover seal weeping and I dropped that in without explanation, and was my mstake. I managed to get the stiffener from The U.S Sprite group. I paid over the odds for it but saves a lot of time messing around making it. Phil, was the 948 A motor 1/4 bsf threaded in the front engine plate, and what difference if any is the head from a 948 compared to a head from a 998?

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philthehill
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Re: Timing cover design A motor 948

Postby philthehill » Sun Jul 14, 2019 7:24 am

The front engine plate bolts are all Unified National Fine (UNF). No British Standard Fine (BSF) threads were used in the 948cc or 'A' Series engines.
See the chart below for the differences in the heads:-
cyl head details.jpg
cyl head details.jpg (870.85 KiB) Viewed 175 times



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