1098 box onto 948 engine

[RobThomas]

Probably covered elsewhere, but...

This engine has a 948 block/crank. I don't have a 1098 flywheel so I was planning to use a 948 flywheel and a Herald (9-spring) clutch cover. The gearbox is a 1275 one. Can I get away with a 948 backplate, 948 thrust bearing and a 1098 release lever? Is that the normal way of gettig a 1098 gearbox onto a 948 engine?

Soooooo many options.

Thanks

Confused, of South Wales

[philthehill]

1098cc gearbox or 1275cc gearbox?

There is a slight change in subject matter

Phil

[RobThomas]

It'll be a 1275 early box but with a Minor fork from a 1098 Minor or a 948 if I can find one here. I did think about a hydraulic release system but thought that might become a problem when converting back, unless you know something different, Phil? The pedals are MM ones at the moment but I might be able to find 1000-style ones.

[philthehill]

Rob
The 948cc backplate, the 948cc flywheel, the 1098cc release lever should work ok. I would fit a 1275cc release bearing though.

In the past I have done a similar conversion but I had to slightly bend the release arm to suit and modify the release bearing as it was fouling the first motion shaft on full travel.
I also had to enlarge the hole in the bell housing to allow sufficient travel for the release arm.
Regards
Phil

Take care and keep safe.

[RobThomas]

OK. I have some 1275 carbon thrusts here so will try that. Ta.

Next job is to find an easy way to get that cast iron sump off. At least it was never filled with oil.

[philthehill]

Rob
A wide thin flat paint scraper usually does the job when driven between the sump and block.

Phil

[RobThomas]

Does anyone have a 948 gearbox front cover handy? I'm after the dimension from the mating face to the centre of the pivot. It is 1-3/8 inch on the 1098 but probably different on the 948.
Thanks
Rob

[RobThomas]

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[philthehill]

Rob

1098cc front cover Pt No: 22G118...……………..1 13/32" from rear machined face to centre of release lever pivot pin hole.

948cc Front cover Pt No: 2A3087...……………….1 5/8" from rear machined face to centre of release lever pivot pin hole.

Note: There is also listed front cover 22A224 for the 948cc front gearbox cover.
Unfortunately I do not have a front cover of that part number so cannot give you any dimensions.

https://www.moss-europe.co.uk/catalogse ... =&q=22A224

Also have a read of this link:-
http://www.gerardsgarage.com/Garage/Tec ... arings.htm

I hope the above is of use.

Phil

[RobThomas]

Thanks, Phil. That's excellent!

I'd seen the Gerard's Garage page and also a few other ones, some of which gave opposite opinions on things such as the need for the cast iron backplate to space the spigot bearing away from the input shaft. I thought it would be worth getting a definitive answer (or as close as possible). The difference in height for the front cover pivot holes is almost exactly the same as the difference in length, or protrusion, of the input shafts. Makes me wonder if the whole idea was simply to space the bellhousing back 1/5 inch to give extra clearance for the fatter clutch cover.
With all this spare time I might as well have a play and see what I can come up with.

Found a good gearbox with excellent teeth and a 22G input shaft (no reverse light switch) so will be using that.

The only annoying items so far have been the lack of an A+ timing chain thrower, or an equivalent, and the new pin drive oil pump being so tight that it left some steel shavings when first run. Less than zero lobe clearance at one point in the rotation.

[philthehill]

Rob
Keep up the good work.

Do you mean the flat oil thrower plate that you need for the duplex?

I sometimes despair at the quality of parts supplied these days.

[RobThomas]

Yes, I had to raid another engine to get the thrower. The one I had expected to use was for the really early cover and wouldn't fit since instead of a small step in the middle it was flat and had a turned up edge round it. Having sorted that I realised that I need to cut the breather can off of the A+ cover since it will foul the Blower belts. Strange that there aren't many of the 'bigger' covers on Ebay. I dread to think how many I threw away over the years.

[philthehill]

Rob
You mean one of these:-

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The moral of this story is.......................Never throw anything away

[RobThomas]

.....Never throw anything away

a.k.a.......never get married.


I haz timing cover envy

[RobThomas]

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Cut the front breather off but then found I can't use the tapet cover breather since it is in the way of the water hose. Are there any breather suggestions for the fuel pump hole??

[philthehill]

Yes
Using the home made adapter plate - photo below - fit a Mini breather.

http://www.minispares.com/product/Class ... o%20search

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You may have to alter angle of the canister and fit an angled hose off the canister to clear.

Thankfully you will not my rear mounted radiator hoses to contend with.

[RobThomas]

I like that idea. I'll see if there is room for it.

I've got 2 gearboxes and maybe another 4 or 5 remote assemblies but none have the brass plunger for tensioning the gearstick. East German Lathe to the rescue!!

[RobThomas]

Survival package arrived from ESM plus a couple of other bits. New waterpump seems to have had metric threads for the fan pulley. Duh. Needed opening out and tapping UNF. My block was missing the dowels for the pump so I lathed up a couple in mild steel. I hate having a metric lathe when everything else is imperial. Wish I could afford a Myford.
I'm missing a lot of parts for the conversion that I'm hoping someone on Faceplant has set aside for me. I did manage to find the bracket for the gearbox restraining cable, a correct 1098 gearstick of suitable length and a bag of new tappets. Result!
I looked at several head options from a 948 standard one (yuk), a 12G295 from a late Midget 1098 (Nice) and an alloy 1275 (too shallow) so it looks like the '295' is the winner. The 1275 has only about 220 thou between the valve face and the face of the whole head. Can some kind soul remind me what the recommended minimum is for a standard lift cam to clear 1275 valve on a small bore block?

[philthehill]

Rob
If fitting the 12G295 head there is no issues with the valve clearances as the 12G295 valves are centred on the 948cc bore.

When fitting the restraining cable bracket to the gearbox drill and tap the screws to 5/16" UNC. The 1/4" UNF screws are not man enough to restrain the gearbox. They were never designed for the restraining job. The restraining cable was an after thought and BMC just used what there was..
I have had to remove one of the water pump dowels to slacken the drive belt. If not removed the drive belt is too tight which may lead to the drive belt snapping and/or the pump bearings failing.

Phil

[RobThomas]

Phil. Can I ask a quick question?

The original cam in the 948 had, as I understand it, only .280 lift. I'm going to go out later and check what is on the car. The 998 Metro has .318 on the inlet and .300 on the exhaust. Does this then mean less of an issue with pocketing the block? Hypothetically, would it be possible to run a low lift 948 cam and a 1275 head or is that just wasted effort that doesn't warrant time spent against reward? I can understand the 'theory' but would welcome input on the real-world expectations.

Edit. Right, it is a pin drive cam with narrow lobes and 235 lift for inlet and exhaust on all 8 lobes, suggesting .300 lift at the valve? Head has .280 to the face and the gasket is 30 thou+. Valves could be sunk further. 11 stud 'K' head. Strangely, the waterways etc line up much better to the holes in the 948 block than other 12G940s.