948, 1098, 998cc Engine...?

[ricombi]

I'm currently building a Historic saloon racing car and have some engine considerations I need some advice on.

My main engine is going to be a 1300cc, which is fairly straight forward and I have someone to help me build that.

For certain races in Europe it is required that I race using a sub-1000cc engine. These are mostly FIA Appendix K events.

I've heard that the bottom end of the engine can be created using a 1098cc block, a 948cc crank and 998cc pistons. I am not entirely sure on this, and as I wish to have a go at building my secondary engine myself I thought I would seek some advice.

The top end of the engine is fairly straight forward, as any head can be used provided it bolts directly to the block, so obviously a 12G940 head will be used, and carburation is best achieved within the regulations using a single Weber 45 DCOE.

Any advice on achieving this kind of capacity would be much appreciated.

Thanks in Advance

[Kevin]

It might be worth your while also contacting the A35 owners club as there seem to be a few of them in historic racing, so it might be a source of more info along the lines you require.

[paulk]

http://www.morrisminoroc.co.uk/index.ph ... hlight=998

Try this.

I asked something about 998's a little while ago and BMC kindly filled me in. Not racing stuf Per se but along the right lines

[bmcecosse]

Yes - the 998 and 1098 Mini blocks are identical, and the 948 stroke is identical to the 998 stroke. So indeed - 948 crank in 1098 in-line block with Mini 998 pistons will give you - 998 cc in-line engine. Try to get the later flat top 998 pistons (and matching rods) - and either use a genuine Cooper S head or an Mg Metro head. Both have the large inlet valves - the S head has larger exhausts but is prone to cracking between the valves. I ran a Mini 998 with S haed in competition - with a 544 cam and twin 1.5" SUs on special long (weber like) inlet manifold. It was excellent - revved to the heavens - I then tried 649 cam and lost all the mid range and seemed to gain nothing at the top. Was glad to swop back to the 544. You should try all the options. Be sure to brace the centr main bearing with a strap - and have the flywheel as light as possible ! Good luck with it - looking forward to progress reports !!

[Peetee]

This is the book you want.
http://www.veloce.co.uk/shop/products/p ... dification&
It explains how the 948 can be taken out to 998 and modified from there.

I ran a mildly modified 948 and it was a peach of an engine. not quite as quick as a standard 1275 but far, far more likable.

[ricombi]

Fantastic! All good stuff! I'm basically looking to build the sub-1000cc engine as a good engine, but not one of these mega high revving ones, as it will largely be used as my secondary engine when needed.

The car is currently rolling and I have most components for the build and the roll-cage is half fitted. Unfortuantely work is closed for christmas and I am unable to continue the project in the workshop until after this yearly event.

Plans are to get the cage fully fitted, fit up some seat mounts and then get it sprayed a fetching colour of Red.
Progress photos will be posted in the new year and I hope to have the car in 1300cc guise ready for its first test in the middle of April.

Thanks for the help

[bmcecosse]

Ah - the old Des Hamill book - much better with Mr Vizards book. If you use the 948 block you will need to fit cam bearings - v expensive. Go with your 1098 block instincts - it already has cam inserts.

[Ianm]

Yes - the 998 and 1098 Mini blocks are identical, and the 948 stroke is identical to the 998 stroke. So indeed - 948 crank in 1098 in-line block with Mini 998 pistons will give you - 998 cc in-line engine. Try to get the later flat top 998 pistons (and matching rods) - and either use a genuine Cooper S head or an Mg Metro head. Both have the large inlet valves - the S head has larger exhausts but is prone to cracking between the valves. I ran a Mini 998 with S haed in competition - with a 544 cam and twin 1.5" SUs on special long (weber like) inlet manifold. It was excellent - revved to the heavens - I then tried 649 cam and lost all the mid range and seemed to gain nothing at the top. Was glad to swop back to the 544. You should try all the options. Be sure to brace the centr main bearing with a strap - and have the flywheel as light as possible ! Good luck with it - looking forward to progress reports !!

I was hopeful someone might be able to advise as I would like to follow this idea of a 1098 block with a 948 crank, 998 flat top pistons. After a bit of measuring and trial fitting when I fit the 948 crank into the 1098 block there seems to be a lot of end float! Like 2mm. I can see that the mains are a different width, can anyone assist with what the best course of action to get the correct fitment. Cheers all.

[Monty-4]

I faced this exact problem. You need the 1098 block with wider main centre bearings (MG Midget?) or double thickness thrust washers (expensive to have custom made if you can't yourself). I got mine made by a guy in the US who makes special thrust washers for Triumphs - when I had a higher paying job.

viewtopic.php?t=73579

[philthehill]

The only real benefit with fitting a 948cc crank into a 1098cc block is that you have a full set of camshaft bearings so enabling you to fit a sports camshaft.
There is not a great increase in noticeable power between standard 998cc and 948cc 'A' Series engines.
You have to add other tuning bits to get a real increase in power which all add to the cost.
I went the other way and had my 948cc block bored to 998cc and had a third camshaft bearing fitted.
The cost of doing the above may be considerably less than getting special thrusts made.
I used Powermax 998cc flat top pistons, 998cc conrods (which are the same as a 1098cc set) a Cooper camshaft, a 12G295 head and twin 1.5" carbs as pictured below.

WDF engine 2.jpg (183.71 KiB) Viewed 3080 times

[Monty-4]

Phil is quite right. The sensible route is the use the 948 block and perhaps have it reamed for proper cam bearings.

[Ianm]

Thanks for all the feedback, really helpful. The 948 block I have is a Gold seal engine which seems to have liners. If I am going for 20754 pistons will this just mean removal of liner and boreing to piston size?

[philthehill]

To be honest I would ditch the block with liners and find a 948cc block which does not have liners.
948cc blocks are readily available and are cheap.

[Ianm]

Ok, thanks again. The pistons I have are 998 +30 so was hopeful that when boreing to that size it wouldnt need anything other than removing liners and re boreing a long with cam busing install?

The workshop looks like a a- series parts emporium! Maybe 1 more engine won't hurt?

Thanks again for all feedback

[philthehill]

If the liners (Pt No: 2A784) are factory fitted the max recommended bore size is 2.477" to 2.4785".
The standard bore size of 998cc 'A' Series engine is 2.543".
So to fit the 998cc plus 0.030" pistons/rings into a block with liners the bore size will past the max recommended liner bore size.
Also the 950cc block has to be bored to 2.6035" to 2.604" before the liners can be fitted.
Therefore you either have a very thin liner which will be prone to failure or a bore which leaves the piston and rings loose in the bore.
So to reiterate if you want a 998cc engine ditch the block being discussed and get another block which you can bore to correct size.
If you go ahead and have a 950cc block bored to 998cc make sure your machine shop machines each bore to suit the piston for that particular bore. Not all pistons and bores are spot on size. The factory had graded pistons to suit each particular bore. We no longer have that luxury.

[kevin s]

I've got a 950 engine which looks like it might be on std bores you are welcome to , If' you are interested I'll try to measure the bores at the weekend.