M20 Engine Info and advice

[Sorton]

Mike,

Fortunately, I owned and drove the donor for many years so have all the documentation. However, knowing the engine number is one thing, proving it to a jobsworth is a completely different story. Hence my hope that I can polish it up so that it can be read.

[cabrioman]

Mike

I have seen the pictures on your site with the Marlin ARB (or should it be non ARB), I can't see that it will do anything except locate the TCA in terms of castor if it is split in that way.

I spoke to Peter Morris he confirms he thinks the bulk head mods on his could have been avoided if the ARB was taken out of the equation but he didn't want to lose it, but I am not sure if fitting the different style ARB as per yours will be enough to provide clearence without cutting the bulkhead.

It maybe that compression struts are the route to go, I know Simon did modify his bulkhead but when he did that he still had an ARB fitted, I think the compression struts were introduced when he found he had a severe castor problem, maybe if he had gone with struts to start with the bulkhead could have been left unchanged.

I think it is something I will have to decide on once I have an M20 engine to dangle over the engine bay.

It would be interesting to get Simons input on the handling with struts but no ARB, I am not looking at building a track car so maybe struts will be adequate for normal road use and provide adjustment on the castor. In essence the Marlin modified ARB is doing the same job as a strut without the adjustment.

John

[cabrioman]

Sorton

The info on BMW engine codes is here:

http://www.ge39.com/files/zeigeinfo.pdf

has pictures of where to find them on different engines.

John

[Simon]

Originally Posted by cabrioman

Mike

It maybe that compression struts are the route to go, I know Simon did modify his bulkhead but when he did that he still had an ARB fitted, I think the compression struts were introduced when he found he had a severe castor problem, maybe if he had gone with struts to start with the bulkhead could have been left unchanged.

I think it is something I will have to decide on once I have an M20 engine to dangle over the engine bay.

It would be interesting to get Simons input on the handling with struts but no ARB, I am not looking at building a track car so maybe struts will be adequate for normal road use and provide adjustment on the castor. In essence the Marlin modified ARB is doing the same job as a strut without the adjustment.

John

Hello John,

I needed to modify the bulkhead on my car very slightly to get the engine to fit. The M20 is a much tighter fit in a Cabrio than a Sportster and the engine in my Cabrio seemed especially tight when compared to Peter Morris's Cabrio. I don't know if my car being a SWB had anything to do with it or whether it was just due to car-to-car differences (to be expected with a kit car). I modified the bulkhead to give approx. 10mm clearance to the back of the cylinder head. As you say, the best bet is to position the engine in the engine bay and then see what clearances you need to make.

With my engine 'in situ' there was no way the ARB I had was going to fit as it ran straight through the sump (and at the time I didn't realise there were different types of Sierra ARB). I also contemplated modifying the sump as well as looking (unsuccessfully) for a version of the BMW M20 sump that had the sump at the rear of the block.

So after some deliberation I opted to go for the compression struts. I haven't experienced any problems on the road with not having the anti roll bar (and I dont 'pussy foot' around!) and the ride comfort is extremely good. The thing to remember with the Marlin is that it's such a low car with a low Centre of Gravity that it doesn't really need an anti-roll bar. I've seen quite a few Sportsters now that dont have anti-roll bars either.

As has been pointed out, the other advantage with the compression struts is that you can very easily adjust the castor angle. This allows you to tune the steering both for 'feel' (i.e. how it loads up in corners) as well as self centering behaviour. Incidentally, the problems I initially had with castor angles was due to the compression struts not being adjusted properly. I set the caster angle very crudely at home initially (to get the car on the road and SVA'd) but then got it set up properly on a 4 wheel alignment rig.

So I would definitely recommend opting for a BMW M20 engine (as it goes like the clappers, sounds great and the electrics are not too difficult to sort out) as well as the compression struts. If you want to use the car on the track, and think you need an ARB, you can always fit a separate one (i.e. non Sierra)

Hope the above information is useful and good luck !

Simon

[peterux]

Originally Posted by Sorton

All very interesting, my F reg (1 Jan 89) 325i Sport donor was always described as "cat prepared" or "cat ready" when I went looking for exhausts. It does not have a cat or lambda sensor, but I think it would have done if sold in other EU countries as we were late adopting the cat principle.

This leads me to wonder if it is the lower compression engine.

So I thought I would check to see the engine number and codes but I have totally failed to find them on the block which is still awaiting refurb in the garage. I thought they should be on a machined area low down on the inlet side but can find no trace of any digits - I hope they have not corroded away! Can someone tell me exactly where these markings should be on a UK engine? Help!

Hi Sorton,
do you still have the V5 for your old car. the engine number will be on that. Mines an F reg and the engine number is stamped on the flat machined area on the inlet side next to the engine mount.. You can see its the unpainted area in this pic.



ooooooooooo^^^ooooooooooo
regards

Peter

[cabrioman]

Simon

Thanks for the valuable and practical "used in real life" input.

I think I will go down the compression strut route and then determine if and by how much I need to mod the bulkhead, can you tell me where you sourced your compression struts from.

Do I understand correctly from your comments that regardless of using compression struts you still felt the the need to modify the bulkhead.

Regards


John

[Simon]

John,

I think a few places sell the Sierra compression struts (including Ebay on occasions) but Burtonpower are a trusted source of quality parts IMHO:

https://www.burtonpower.com/product_...ession%20strut

Yes, regardless of the compression struts I needed to modify the bulkhead slightly as lengthwise the M20 is a bit of a squeeze in a Cabrio. The link below shows the mods to the bulkhead:

http://www.flickr.com/photos/marlin_...7594349598270/

In hindsight it may not have been strictly necessary to cut and re-weld the bulkhead and I could have probably achieved sufficient clearances with simple panel beating of the bulkhead (although it may not have been as neat a job with my limited panel bashing skills!).

If you dont fancy the idea of modifying the bulkhead, then the other option may be to try and move the radiator forward a bit.

Regards

Simon

[cabrioman]

Simon

Thanks, looks like the best bet is to source the engine first and go from there for the bulkhead mods, Burton Power looks good and reasonable for the struts.

Regards

John

[Sorton]

John & Peter,

Thanks for your responses. As I mentioned earlier, I have all the papers and know the number of my engine but wanted to be able to point to it on the block.

Funnily enough my number is located in the same position as yours, Peter, but not as shown in the BMW reference quoted by you, John. The difference is only a few inches on opposite sides of the engine mount but it just goes to show that there are differences in parts one would expect to be identical.

Re the Cabrio ARB.

When I collected my Sportster kit in the dim and distant past the ARB brackets and bushes were out of stock. After months of waiting I was told that they could no longer source these parts and anyway the ARBs were not necessary so I got a credit note. I do not intend to find my own brackets and fit the ARBs. However, with the Sportster I have the option to change my mind!

[peterux]

Originally Posted by Sorton

John & Peter,

Thanks for your responses. As I mentioned earlier, I have all the papers and know the number of my engine but wanted to be able to point to it on the block.

OK, I got your point now, you need to the prove its the engine you say it is. I would try gently running an old wood chisel across the surface with a little 3-in-1 oil. (Like as if you were sharpening the chisel on a stone). You should find the block comes up shinning leaving the 'crud' in the stamped numbers or as Robin suggests use some paint.

Your comment about the ARB brackets was the same as my experience with Marlin insisting it was not required on the Sportster. The latest wishbones do not have the location brackets welded on, so you can't fit one.
Which also reminds me, have you had you wishbones swapped under the recall notice issued by Marlin?
...peter

[Patrick]

I don't suppose there is anything to stop you cleaning up the area and restampting the engine number on to the block.

[Chris Cussen]

I know it is a fly in the ointment type suggestion but wouldn't be easier to go down the Zetec route?

[cabrioman]

Chris

Could go the Zetec route but by the time you have sourced an injection system, ecu and all the RWD mods you will be circa 3K.

The tubular plenum, ecu and mapping will be around 1k on their own, if you go throttle bodies you can double that.

Then I am back to the sort of costs I was looking at for my original choice of Rover V8.

BMW for me is the most sensible option.

John