M20b28 Easy swap eh!!

[Dubmaster77]

So after taking my track slag round mallory and coming into the pits knocking like a Barsteward, i recovered her back to base whiped out the lump and droped the sump!
Number four big end 5-6mm of free play and 7-8mm of end float on the crank!!!
The engine block itself was fine though and the bores showed no wear. So instead of dropping n a new lump i though I would do a quick 2.8 stroker!

Picked up a complete single vanos M52 2.8 from the classisfieds here as i already had a set of b20 conrods and what I belive to be a high compresion engine.... Things are not going well.

Crank whipped out of the 2.8 the webs seem massive dropped into the M20 and it wouldnt rotate until we ground out the breather pipe casting but now spins sweet as a nut..... con rods attached to pistons... Engine locked up again.... Quick run down to the engineering dept and 5mm taken off the skirts but no good no spinning!! so 2.8 pistons fitted to 2.0 conrods... Spins away but at TDC is 5mm from top of the block.... now my 2.5 con rods are 5mm longer....
Has anyone used this combination the 2.8 pistons look better than the 2.5 but have no dome??
Am i missing something, The wiki makes it seem easy and i think i have all the right bits but they dont seem to fit as intended?
Any advice greatfully recived.
Stu.

[HairyScreech]

Whats the part number from your crank? the early early pistons often need 14mm taking off rather than 5mm.

My advice would be to pull the crank back out and check the clearance on the skirts before trying to put it into the engine.

How long are your current pistons skirts?

Photos?

[Dubmaster77]

Hi screech! Have just been reading your epic thread till one last night, Dreamt of pistons and con rods all night.....

Im going back to start checking things at work today get some pics and get some numbers,
Looking at your pics my pistons do not have cutouts in the skirts but are from an 885 head, The car is a 91 but i have a feeling the engine has come from a different car altogether....

I reckon taking another 9 mm of the piston wold do it but means machining into the actual meat of the piston itself where as so far we have just removed the skirt extension.
Good job we have an on site machine shop... though not tottaly willing operators!!!

pics later!!!
Stu.

[Dubmaster77]

Sorry for rubbish posts and pics, not only am I at work full time but i have to study for work and its hand in week.... And i have a broken car... and trying to fix my mates broken moped.... and get ready for some mountain biking and camping at the weekend!!

i couldnt get a pic of the crank out of the block in the limited time I had, Number on crank is 1432277
The only other number I could find was NC38?
I looked for an engine code on the block but could only find 1432219.
Hard to see in this pick but we had to relieve the casting in this area to get her to spin



Ok my con rods....

The one on the left my standard 325 rods the ones on right some 320 rods purchase for a bargain 99p on the bay look about right to me?

Pistons... sorry you will have to tilt your head for this pick stoopid photobucket editor is playing up!
Standard piston on left our modified version on the right, The machine shop took of the lower skirt extension..



My coleague got the grinder out on the machined piston which had suffered some damage when the bottom end went, we have sucessfully got the crank to spin!! but im not sure how much meat we can safely take out of the casting before we risk the pin coming through or piston slap occuring? 14MM is impossible to macine of the pistons without machining into the gudeon pin hole.



any pointers at this stage greatly appreciated!
Was the 885 head availible as a high compresion engine? i imagine the same piston design with the gudeon pin move higher up the piston body would reduce the compresion and allow more machining of the skirts.
I have a set of 135 mm m52 rods has anyone sucesfully found a solution to using them and if so which pistons where they used with, My colleague wants to use the flat top pistons which is possible it seems using our 320 rods btu im determined to use pistons designed for the 885 head as they have been designed to work togeher.

Cheers,
Stu.

[HairyScreech]

From the side its hard to tell if they are high comp or low comp pistons, but if that is the stock skirt length then they look like the shorter skirts of the later pistons.

measure the rods by measuring the two holes and halfing the result, then measure the shank between the two holes, add the two and thats your rod length.

How much distance do you have from the bottom of the bottom ring land to the bottom of the skirt on the modified piston?

have just been searching for the crank and block number there but i can seem to find anything to match, realoem comes up blank.

However i have a feeling that you might have a crank with the larger webbs...



your questions:
Was the 885 head availible as a high compresion engine?
- All 885 heads are the same and all 325 engines used 885 heads.
The way to tell is that the squish band in the chamber is angled from the head surface at about 20-25 degrees.

i imagine the same piston design with the gudeon pin move higher up the piston body would reduce the compresion and allow more machining of the skirts.
- The high comp pistons have a smaller more shallow bowl in the top, the pin height is identical however in order to maintain squish clearance.

I have a set of 135 mm m52 rods has anyone sucesfully found a solution to using them and if so which pistons where they used with,My colleague wants to use the flat top pistons which is possible it seems using our 320 rods, btu im determined to use pistons designed for the 885 head as they have been designed to work togeher.
- Yes maintaining correct chamber geometry is as important as the CR of the engine when it comes to detonation and clean combustion, totally flat top pistons with an 885 head is a poor match, however it will work ok.
The 135mm rods have been used before using custom pistons, however most custom ones are flat topped and badly matched.
There are some good ones with the right profile out there.

I am currently working on the m20b28, there is a lot of info in my thread on unusual ways to go about things and potential methods of improving things, however most of it is theoretical at this stage and kinda technical, so just skim anything thats irrelevant.

[HairyScreech]

http://www.e30zone.net/modules.php?name ... ht=1432277

http://www.e30zone.net/modules.php?name ... ht=1432277

seems as though you may have a late single vanos crank, there is no 100% guarantee that you will have the small web crank.

Seems as though there are 3 cranks, the early small web, the later mid web and a blue tinted tuffrided B28TU crank which i am using with even larger webs.

[Dubmaster77]

Once again thanks Screech!
Im going away for the weekend and wont be back until tuesday, However half term next week so no kids in the work shop so i can do some proper measuring.
Watch this space!
Cheers, Stu.

[basketweave]

I have fitted the m52b28 single vanos crank to my m20 block with no clearance issues, and if you have a look at my thread its got a blue tinge/tint to the crank.

http://forums.eurocca.net/showthread.ph ... tory-parts

I would stick with the m20b25 pistons if you can.

[HairyScreech]

I have fitted the m52b28 single vanos crank to my m20 block with no clearance issues, and if you have a look at my thread its got a blue tinge/tint to the crank.

http://forums.eurocca.net/showthread.ph ... tory-parts

I would stick with the m20b25 pistons if you can.

very nice looking job wish i had workshop space in that order to use, being a student means i have to scrounge it where i can either at work or in a friends unit.

I think you may be right, a lot of the cranks were forged and tuffrided, i know the tu crank is for sure, the single vanos one i just pulled doesn't seem to be, however it could just be burnt on cack.

as above if you can go with the b25 pistons then do, they are the ideal shape for the head and the b28 pistons would need significant modification.

If you do have a large web crank then a good engine/machine shop should be able to bob the webs back to the size of the early webs.

[Dubmaster77]

Hi basket weave.
I have previously read your thread also before i started this, Yours seemed to fall together, I think I prefer the idea of having the webs resized and then the crank balanced and lightened rather than over engineer the pistons. Im looking for a standard 325 lump at the moment so I can keep the car on the road while i build up the new lump.

[HairyScreech]

Where are you dubmaster? I have a single vanos and a tu crank should you need to compare, or i can probably get the measurements.

[Dubmaster77]

Im in Derby Screech, Where abouts are you?

[HairyScreech]

ah, no where near, im either in swansea or wiltshire, with the crank at home in wiltshire.

[Dubmaster77]

Not to worry, I have a contingency engine going in now, Thinking about having the crank shaft lightened balanced and knife edged to save the pistons, Though i do need a new low comp piston to replace my "Test Piece"!

[basketweave]

Hi mate,

Unfortunate to hear your engine is not falling together..... I made it sound prob easier than it is, it has been a long road for me also. I have had more pains with the scraper and head though, but the crank was good to me.
Time will tell with mine, it goes in soon.

Screech, my workshop is my single car garage, where my car used to live nice and dry. Now it's out in the elements I am keen to get the engine in and get my garage back.

I have had some luck with my neighbour in the unit block, lending me his double garage to do the swap

[Bullet_Ride]

I am also building an M20B28. It's almost finished and it will be going in within the next couple weeks. I used a single vanos crank for the build with the late model short skirt pistons. The crank would rotate freely within the block but the counter weights would hit the piston skirts so I turned down the counterweights and had the crank rebalanced. Nothing was taken off of the piston skirts.

I have my build thread posted on a couple forums, but not here unfortunately.

http://www.r3vlimited.com/board/showthread.php?t=243359
http://www.e30tech.com/forum/showthread.php?t=112985

[HairyScreech]

I actually read your build a few days ago, i think you actually would have been able to trim a touch off the bottom of the skirts and get away without having to bob the counter weights, however it does mean you now have a lighter crank.

[Bullet_Ride]

This picture shows how far off the rod cap was from being seated, the counterweight would have to move that much farther up into the piston + whatever clearance you want between the piston and the counterweight in order to be able to torque the rod cap on.



I'm not sure that just trimming the piston skirt would be enough. I think the counterweight would end up hitting the boss where the wrist pin is. The OP seems to be having this problem.

[HairyScreech]

Hmm, there does seem to be some issue with the single vanos crank as well, seems there is more than just a single vanos and TU crank.

Most people have been able to use the single vanos crank, 130mm rods and the pistons with this profile put on the bottom.




Do you know what the part numbers of your crank and pistons are?
When i am home next weekend i will get the numbers off all the kit i have there.

[Bullet_Ride]

I don't know for a fact that the counterweight would hit the wrist pin boss, as I didn't take any dimensions of the inside of the piston (i.e distance from piston skirt to wrist pin boss) because I was planning to machine the crank from the get go. If people have had success with their pistons cut as you show in that picture, the counterweights must be coming pretty damn close to the wrist pin boss lol, but as long as it rotates freely when it's at temp then who cares how close it is right .

I'll try and take a look at the part numbers on my crank and pistons tonight tonight.

[HairyScreech]

the counterweights must be coming pretty damn close to the wrist pin boss lol.

Yeah pretty much, never really asked the question of how close is to close on this one but provided there is a few mm i cant see an issue.

Bobbing the crank is a good way to go about it, the b28 crank is quite a bit heavier than the m20 one so will increase the rotating mass quite a lot, The webs are also quite large so will be stirring up quite a whirlwind of oil.

I think its about time we get a proper list of cranks that are know to clash/clear together and get it onto the wiki.
I have one i know will hit for sure and one i believe will clear.
The webs that hit seem to have a flat end and the webs that don't seem to have a ribbed end.

[aceifty]

i had done a m20b28 last year, had no problems at all and still drives fine.
i used
2.8 crank
m20b20 rod
m20b25 pistons
885 head
290 cam
all new rings, bearings, seals etc.

just looking around for a MAF conversion, might be going for the MILLER MAF conversion with the W.A.R chip.


only one bad new that i did not to a build thread but got alot of pictures of the build.

[Bullet_Ride]

Well I've had my 2.8 swap up and running for a few hundred kilometres now and I just wanted to report back to say that I am very happy with the performance of the motor. There is a lot more low end torque which makes it great to boot around town in, and much better for passing the slower chaps. And on the top end the thing is a beast, pulls hard to red line and 200km/h comes much faster than before!