Will Frost's M20 Engine build

Mon Sep 23, 2013 9:21 pm

I am beginning my engine build and have started collecting parts now.

The engine is going into my 1978 E21 323i.

I also already have a lightweight flywheel, 6 paddle clutch kit and close ratio dogleg gearbox / alpina lsd.

The plan so far for the major components

Head - 885 (ported by SRE Launceston/new guides etc)
Cam - Kent Cams - BM63 Sports R (Specs below)
Cam pulley - Adjustable
Rockers - heavy duty
Valve springs - Metric Mechanic beehive ?
Valve retainers - steel
Block - m20b25 cleaned/freshly honed/line bored
Crank - m52b28 84mm + custom spacer (balanced/knife edged)
Pistons - Forged 10.25:1
Rods - m54b30 135mm, lightened, balanced
Bearings - ACL Race
Fasteners - ARP
Head gasket - ?
Lightweight flywheel 6kgs

I plan on everything being balanced as a rotating assembly.

Will

Mon Sep 23, 2013 9:38 pm

The cylinder head has been freshly ported by SRD Engineering and the valve guides have been replaced and also bullet nosed. The valves and seats have been re cut also as well as a light skim.

Tue Sep 24, 2013 9:02 am

what is the purpose of the build? street? track only?

is it safe to bore the smaller blocks to 86mm?

i wouldn't bother with titanium retainers. a crmo steel retainer for beehive spring is not much heavier than a titanium retainer for a dual spring setup and certainly not required for a catcam 288 ( not an off the shelf part)?

Tue Sep 24, 2013 9:18 am

The build is going into a rally car.

I am not sure about the blocks to be completely honest - I thought they were the same apart from deck height on some versions.

I have an M20B25 block here too which would be fine. Initially I was going to use an 84mm bore and wanted fresh bores hence using a smaller block. As it is looking like a bigger bore now I may as well use the 2.5 block.

Wed Sep 25, 2013 1:19 pm

As above, go for a smaller steel retainer, theres little weight difference and a huge cost difference, beehive springs will also perform better.

Head looks like it has been worked in all the right places, not sure about the removal of the guide ridge, people other than me have played about with it and found when worked right it causes very little flow loss with a benefit to velocity. Still everyone has there own ways of working heads and there isn't really a right or wrong.

Wed Sep 25, 2013 1:19 pm

As above, go for a smaller steel retainer, theres little weight difference and a huge cost difference, beehive springs will also perform better.

Head looks like it has been worked in all the right places, not sure about the removal of the guide ridge, people other than me have played about with it and found when worked right it causes very little flow loss with a benefit to velocity. Still everyone has there own ways of working heads and there isn't really a right or wrong.

Wed Sep 25, 2013 9:33 pm

Thank you for the input screech ! Much appreciated

.

Has anybody here used forged pistons and rods for this kind of build ?

I know the M20B25 pistons and rods are plenty strong but I am looking to reduce the weight of the rotating assembly.

The reasons I would like to add oil squirters under the pistons are for cooling meaning the piston to bore clearance can be a little tighter. Has anybody any info on adding these to an M20 ?

Will

Wed Sep 25, 2013 9:54 pm

If you dont mind spending get forged pistons and 135mm or even 140mm rods

Wed Sep 25, 2013 10:02 pm

Yeah I have been getting sticky pants over the metric mechanic website and their parts.
Kormann seem to have some nice ideas too.

I dont want to order from overseas really though (import tax)...

Wed Sep 25, 2013 11:20 pm

Be careful with forged pistons and their tolerances. They are different to cast pistons, you need to run them at the manufacturers specs oil squirters or not. They can be a little slappy when they are cold, but that is just forged pistons, some engines are worse than others. The pistons expand more when they heat up, so not really ideal to go looking to make the tolerances tighter. As Dan has mentioned 135mm rods would be good for a bit of top end, and a reduction in piston slap as the rod angle will be less.

The rings seal the bore not the piston anyway.

Sadly there are few places in this country that will be able to sort you out and even then they will be getting their stuff from America, so you will be paying the tax but blissfully unaware. The fact is the American stuff is cheaper even with the tax.

I have just priced up with Topend Performance, USA. And some custom pistons for a 450bhp+ m20 come in at £800 delivered less tax, and they are pretty trick. At the customers request we are trying a UK company too. I phoned them today, but sadly colin (or whatever his name is) is away on holiday the only chap that deals with the performance stuff in the company

The grunt on the phone mentioned CP pistons, so they would be coming from the States anyway.

As for rods, Time Team will be digging up m20 rods in a thousand years time

They are, shall we say well over speced. The above engine uses m20 130mm rods at the moment. so lets say you shoot for 250bhp, that leaves a little room for weight to be taken off them. I'll post a picture of the lightened rods i'm working on at the minute. However my rod of choice for you would be a lightened+balanced m52 rod, 135mm, and they are light and very well made, then have pistons to match that build.

I still have a gearbox here for you by the way.

Thu Sep 26, 2013 1:56 am

molnar make some nice light rods (sub 500g with bolts which is about the lightest you will find) for the S52 which are same as that for M20B25. MM make longer rods but alot more $$$ for pretty much an unquantifiable benefit.

could always use S52 rods as these are alot lighter than M20 ones and plenty strong for a NA engine

topend can do a JE piston with the "9.7:1 OEM piston crown" with a reduced compression height and bigger bore suit a b28 crank. this will give you about the 10.5:1 CR you want with the additional capacity over that of the B25.

Ireland engineering can now do something similar i believe but with Ross pistons

Sat Sep 28, 2013 1:28 am

The m52b28 rods are a mass production version of the s50 rod, they are as strong as the m20 ones with significantly less mass.

Sun Nov 03, 2013 11:20 am

stop playing with your S50 build and crack on with this build Will, I might be after you to build me one ;)

Sun Jan 12, 2014 7:31 pm

Just a little update.

I now have a Kent cam, and adjustable cam pulley.

http://www.kentcams.com/product-details ... ports-'-R-'

And I have had the rocker cover soda blasted ready for refinishing.

Will

Sun Jan 12, 2014 8:05 pm

Rallyprep_UK wrote:I am beginning my engine build and have started collecting parts now.

The engine is going into my 1978 E21 323i.

I also already have a lightweight flywheel, 6 paddle clutch kit and close ratio dogleg gearbox / alpina lsd.

The plan so far for the major components

Head - 885 (ported/new guides etc)
Cam - catcam 288/288
Cam pulley - adjustable
Rockers - heavy duty ?
Valve springs - Metric Mechanic beehive ?
Valve retainers - steel
Block - m20b25 cleaned/freshly bored to 86mm
Crank - m52b28 84mm + custom spacer (balanced/knife edged)
Pistons - Ireland engineering forged 86mm 10.5:1
Rods - m54b30 135mm
Bearings - ACL Race
Fasteners - ARP
Head gasket - ?
Lightweight flywheel

I plan on everything being balanced as a rotating assembly.
I would like to install piston oil squirters, has anybody here done this ?

Will

I did something like that. was quite nice but needed mapping. then it blew up on the dyno and has been in the garage for a couple of years

Sun Jan 12, 2014 8:17 pm

Oh no ! Do you know what went wrong ? What was the extent of the damage ? I would cry !!!

Will

Sun Jan 12, 2014 8:17 pm

Oh no ! Do you know what went wrong ? What was the extent of the damage ? I would cry !!!

Will

Sun Jan 12, 2014 8:50 pm

spun a shell, crank, rod damaged. it had covered 2000 miles and did a trackday at cadwell and some 15sec runs at the pod but four hours on the dyno on a very hot day was a bit too much for it. haven't been able to think about it as it depresses me but collected up some parts and im getting back into it. (hence im back on e30zone) planning to get it back out this summer and wont be going anywhere near a dyno. I have a set of lightend balanced m52 rods if your interested. not the ones that were in it

Sun Jan 12, 2014 9:37 pm

Bloody hell, what a wounder

I did wonder why you suddenly disappeared

Sun Jan 12, 2014 9:51 pm

yeah was a bit of a blow. stripped it straight away but couldn't find the enthusiasm to put it back together. bought an e36 m3 and spun two shells on that. thought it best I had a break from motors. new crank and rods waiting to go in. should paint the engine bay this time too. coming back stronger

Sun Jan 12, 2014 11:30 pm

Good to hear your fixing it

Mon Jan 13, 2014 11:16 am

ezagood wrote:coming back stronger

That's the spirit

Wed Oct 22, 2014 11:20 am

Blimey, a (small) amount of progress !

I finally got the block out and onto a stand. I have also started gathering everything I had for the engine already for cleaning and painting etc. I also had delivery of my camshaft

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[img][img]https://farm4.staticflickr.com/3946/149 ... 5ff5_b.jpg[/img]2014-09-17 11.15.47 by Rally Prep, on Flickr[/img]

[img][img]https://farm6.staticflickr.com/5597/149 ... cbde_b.jpg[/img]2014-09-17 16.11.00 by Rally Prep, on Flickr[/img]

[img][img]https://farm6.staticflickr.com/5613/155 ... 7e00_b.jpg[/img]2014-09-21 18.31.22 HDR by Rally Prep, on Flickr[/img]