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Go Back   Madabout Kitcars Forum > Mad Build Area > Marlin Sportster, Cabrio, Berlinetta and Roadster builds

Marlin Sportster, Cabrio, Berlinetta and Roadster builds Enthused or Confused about your vintage Marlin build? Ask away here or show off your build.

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  #1  
Old 4th January 2017, 14:22
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Default 2.5 block needed

Hi All,

Does anyone out there have a spare 2.5 M50 block? My current M50B30 stroker project has hit a small snag when I took all my parts to the local machine shop today. Basically the bores on my M50B25 iron block are worn leaving a lip at the top that would instantly destroy the higher piston rings on the M54 pistons. My original idea was that just this lip could be cut out and the cylinder be honed but they've told me it needs a 0.25mm over bore and therefore new oversized pistons. The only ones we've found are 135 each + vat making that route totally uneconomical. Current options are

1. find a lower mileage M50B25 block that doesn't need a rebore, just a hone

2. Just rebuild the M54B30 as is and put the M50 back together

3. Find an M50B20 block and bore that from 80 - 84mm as everything else is the same - would be expensive on man hours though

4. Put the M50B25 back together again and accept defeat (don't see this as a real option)

I've seen some oversize M50B25 pistons for sale on ebay at a reasonable price so I could always still get the M50 block bored and rebuild as is. It will at least be resell-able then as an entire refurbished engine. Seller is Jazzman.0018 - is that you Patrick (recognised you have something very similar as your youtube name)
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  #2  
Old 6th January 2017, 21:53
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Spoke to the machine shop again yesterday evening and they confirmed that the M54 block is still in spec so can just be honed. I've stripped the M54 head down and sent it in for them to skim and clean up so it looks like it will be an M54B30 build for the sportster. I'm a little disappointed as I was hoping to do something a bit more unique but not at over a 1000 just on machining and pistons. With the cost of the other parts such as bearings, rings and gaskets I'd be looking at over 1500 for a stop gap engine. If I was restoring a classic then it would be worth it to keep the originality but for a kit car, nope. If I spend that much money it will be on a much more interesting engine project.

I'm getting them to modify the head to accept an M50 style thermostat so I can still run at a lower temp and there will be some other mods to accept the coolant temp sensor for the gauge (unless I can get the megasquirt to provide it instead).

Other than that I'll invest the modding effort into a custom intake manifold potentially incorporating a set of S54 ITBs. Need to practice my ali TIG welding first though.
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Old 7th January 2017, 13:32
mcramsay mcramsay is offline
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Just chuck an s50b32 m3 lump in!!
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Old 8th January 2017, 11:47
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Quote:
Originally Posted by mcramsay View Post
Just chuck an s50b32 m3 lump in!!
......... try and find a reasonable one for less than 1,500! Not a cheap option.

Ian wanted the fun of building a frankenstein stroker: but an M54B30 is not so bad - that's what I am planning, except I want to keep mine as standard as possible, running the DISA manifold and MS43 ECU.

Ian be careful with your manifold plans............... ITBs are good for top end revs, but the M54B30 has a well known harmonics problem with continued high revs destroying the oil pump/sprocket/nut.

If its an interim engine, why not stick with the DISA and make use of the incredible low down grunt? Much better suited to a daily driver - I'll bet it will be quicker as a road car!

If you want a track animal then why not go for an S54 - it's probably just as cheap as an S50, easier to find, and a better engine.
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Old 8th January 2017, 12:29
mcramsay mcramsay is offline
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That's true, I was only kidding around! What's the benefit of stroking the current engine, more low down torque? I only ask out of interest!
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Old 8th January 2017, 12:35
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Quote:
Originally Posted by mcramsay View Post
That's true, I was only kidding around! What's the benefit of stroking the current engine, more low down torque? I only ask out of interest!
You get something similar to an S50B30 for a lot less money, and you have the fun/cudos of building your own engine: the M50 steel block is better suited for higher revs too (it is basically the same block as the S50, S54). As Ian is doing, it usually goes hand in hand with developing a stand alone engine management system.

I love the idea, but just do not have the software/electrical ability to pull it off.

It's a shame Ian, I was looking forward to seeing your progress with the M50B30 run on a standalone system.
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Old 8th January 2017, 12:38
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Does the m50b30 not have vanos then? I wanted to run an aftermarket ecu on my s50b32 but I could only find that the DTA ecu would control the vanos, and mapping etc would be difficult.
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Old 8th January 2017, 20:42
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The TU version of the M50 had single VANOS on the intake side, earlier ones did not, so it depends when it was built.
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Old 8th January 2017, 22:02
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Quote:
Originally Posted by mcramsay View Post
Does the m50b30 not have vanos then? I wanted to run an aftermarket ecu on my s50b32 but I could only find that the DTA ecu would control the vanos, and mapping etc would be difficult.
From what I've read Megasquirt 3 will run Vanos - there is a guy in Canada with an M54B30 (it has dual Vanos, and DISA intake) running on Megasquirt 3, so you could run your S50 on a stand alone if you wanted.
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Old 9th January 2017, 13:20
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Quote:
Originally Posted by morris View Post
Hi All,

Does anyone out there have a spare 2.5 M50 block? My current M50B30 stroker project has hit a small snag when I took all my parts to the local machine shop today. Basically the bores on my M50B25 iron block are worn leaving a lip at the top that would instantly destroy the higher piston rings on the M54 pistons. My original idea was that just this lip could be cut out and the cylinder be honed but they've told me it needs a 0.25mm over bore and therefore new oversized pistons. The only ones we've found are 135 each + vat making that route totally uneconomical. Current options are

1. find a lower mileage M50B25 block that doesn't need a rebore, just a hone

2. Just rebuild the M54B30 as is and put the M50 back together

3. Find an M50B20 block and bore that from 80 - 84mm as everything else is the same - would be expensive on man hours though

4. Put the M50B25 back together again and accept defeat (don't see this as a real option)

I've seen some oversize M50B25 pistons for sale on ebay at a reasonable price so I could always still get the M50 block bored and rebuild as is. It will at least be resell-able then as an entire refurbished engine. Seller is Jazzman.0018 - is that you Patrick (recognised you have something very similar as your youtube name)
It seems to be a shame to give up on Option 1.
Somebody is bound to have an M50 block or engine lying around, it may just take a while to find it. I had a M52 328 block that I couldn't even give away and it end up in the scrap metal bin.
Have you tried on the BMW forums and maybe even the MOC forum who seem to be good at squirrelling things away?
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Old 18th January 2017, 02:20
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Whoa, lots of activity that didn't make it to my email inbox for some reason.

To answer the question on the s50 option, it's simple, I didn't have free one knocking about the garage, unlike the M54.

The megasquirt ms3x can now handle double vanos but it is pwm based i.e. you send a varying pulsed signal to say how much you want it moved, the same as an idle valve. The only problem with that is how much do i want it to move and when? The exhaust side does little for power, just emissions so I'll probably just leave that on/off full the whole time. I have a cunning plan to just use the standard on/off solenoid from the single vanos on the intake side for now at least.

This engine is just a stop gap until I can find the right V12 so I don't want to break the bank on it.

On the ITB issue Mike, yes I agree that there is little to be gained from them at sub 5000 rpm. I just love the way the look and sound. My sportser is so far from a daily driver that day to day driveabilty is the least of my concerns, I just need it to put a grin on my face. It's also a good project to get me building up experience on my TIG welder. I may just go for a more simple single throttle design first and build up to the ITBs. It's the building I enjoy much more than anything so having a not so sensible project is always good fun.

I'm stuck in Canada at the mo so no updates until at least next week I'm afraid
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