Low cost engine build

[madjak]

Yeah they can be a bit of a pain. I have around 50 shims sitting in a box so hopefully I can get it close with those. I have sanded shims manually (up to around 6-7 thou) with some wet and dry sand paper stuck down to a sheet of glass.

It works well to close up the tolerances. Unfortunately opening them requires reshuffling a the shims.

[greenMachine]

Re-reading your posts Stan - are the shims you bought for the stock NB8A buckets, or for SUBs? I was talking SUBs, so the price I had in my head may be irrelevant for you if you bought stockers.

MadJak, when I did mine I had access to a shim grinder, made life a lot easier, and quicker, when thinning them down . Needed to be careful though, very easy to take too much off if you are not careful .

[madjak]

yeah a shim grinder would be nice!... still sand paper can take it down fairly quickly. 800grit with a bit of oil and like 20 seconds will take 1 thou off. I just rotate the shim on my finger every 5 seconds and I think it gets it pretty even. I wouldn't take too much off in one go though as it might generate a taper on the shim surface but 6 thou only takes 3 mins.

[StanTheMan]

Re-reading your posts Stan - are the shims you bought for the stock NB8A buckets, or for SUBs? I was talking SUBs, so the price I had in my head may be irrelevant for you if you bought stockers.

MadJak, when I did mine I had access to a shim grinder, made life a lot easier, and quicker, when thinning them down . Needed to be careful though, very easy to take too much off if you are not careful .

Mine are NB8A buckets.

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[madjak]

Since I'm doing this as a DIY build and it's a bit of an experimentation project I figure I might try and balance the lightweight crank myself.

I have several low friction bearings that I'll mount to a base cradle for the crank to run on. I'm guessing that I should be able to sit the crank on them and spin it by hand to find where it settles. I can then machine bit of weight off the bottom faces to balance it out. Then I can spin it up with a drill and see if I get a vibration. Plus I can compare it against a properly balanced race crank to see how close I can get.

I'll give it a go over the next few nights and see what I get. It should be good fun regardless.... I like fidget spinners!

[madjak]

Here is a photo of my home made crank balancer:



The crank spins nice and freely so the heavy side settles at the bottom. I can then add some plasticine to the top to figure out where the best balance point is. By spinning it 20 or some times and marking where it rests I can average the marks to find the light / heavy side.

My aim is to use a flapper to take weight off the crank until I can't detect any weight difference and then send it off to the machine shop to check.



I also drilled and tapped in some 1/8" NPT bungs into the oil drill holes of the crank. I normally remove the ball bearings on all my race cranks so that I can get in an clean out the oil passages.

[StanTheMan]

Low cost engine build....LOL

lats a lot of effort you putting in there. Not that I'm suggesting this is a bad thing.

[madjak]

It's low cost... not low man hours My time standing at a milling machine shaving off weight is pretty much free.

This crank I've had sitting around for 18months because I ran out of guts to drop it into my race engine last build. I figure this one will be a good candidate!

[bruce]

Low cost/Maximum effort engine build.

[Custardtart]

Love seeing this sort of stuff. Inspires me to be more ambitious with my build

[GR124]

loving this build madjak, please keep us updated

Quick question, as I don't want to side track this thread.... Is the NB8A crank the same (material/strength) as the N8A? As I have a spare N8A bottom end I may play with.

[madjak]

I'm pretty sure all the BP blocks are the same from 1994 through to VVT era as well as 1994-1998 Protege and Astina blocks. There might be some minor casting difference but they all are interchangeable with really only the pistons, oil pumps and sumps being different. I'm 99% sure that all cranks from BP 1.8s are the same forging.

The accessory differences are:
- Pistons are different compression through the years, from 8.5:1 to 8.8:1 to 9.5:1 to 10:1
- Rods are the same... I think
- The 2001+ VVT engine has a wider oil pump gear so it pumps a bit more. These fit on all blocks as do the earlier pumps
- The 2001+ engines run the MBSP (Main bearing support plate) are definately worth running on anything putting higher loads on the bearing caps. These require the later engine sumps or a quick mod on MBPS to clear the earlier sumps.

The block and crank i'm using is from a 1998 Astina which run a different oil pump (dip stick comes out of the bottom of the oil pump... but this can be blocked off). I will be running a standard 1994 oil pump from my race engine on this block which has the return valve blocked off as I run an external pressure relief valve.

I'll be blocking off the oil squirters even though I'm running stock SE pistons. I'm not sure how this will go but I figure I'm running E85 so they should live. There is a bit of power to be gained by blocking off the squirters (1-2 Hp) as they spray a cloud of oil that the crank has to chop through. Plus the main reason is to gain some oil pressure which is handy and retain oil volume in sump.

I'll also be running stock rods, my cut down crank with no MBSP given this is a low cost build and I want to see if the bearing suffer. I'll also make up a sump baffle plate cause it's easy and stops oil surge. For a proper race engine you really do want to run forged rods if you are planning to rev past 8000 rpm, and if you go for rods, get some proper pistons too and of course the MBSP.

Last thing is I like to get the die grinder out and clean up the inside of the block a little. I also do this in the head to try and promote the oil draining back to the sump as quickly as possible. At really high RPM levels oil accumulates up in the head and you lose sump volume. This can surge under braking so it's good to clean up anything that slows down or catches the oil on the inside of the engine. I also find it very therapeutic cleaning out all the nasty casting tags.

[GR124]

more than expected response
I pressed the LIKE button madjak.

sorry to be a pest but I would love to hear more on how you used the milling machine to knife edge ya crank. I just purchased a mill and I have a spare crank to play with

[madjak]

I'm not sure a lightweight crank will work well. Emilio from 949 Racing ran a lighter version than mine and had bearing issues.

So I suggest waiting until I test this one.

I did a couple of steps to mill mine. Basically I made two chunky 'L' brackets. One with a central hole that the main front bolt could bolt through and on the other 'L' I milled the flywheel bolt holes around the same center. These were rotated slightly so that I could get the angle I wanted off the counterweights. Flipping the angle bracket and the crank reversed the angle so that I could match it on the other side.

Then I spent a few hours shaving a mm at a time off the required counterweights with a 80mm multitooth cutter.

Next stage I mounted it all in a lathe and cut the weights on an angle. You need to be pretty careful spinning cranks as any wrong move can do some serious damage.

Lastly I flappered everything and either chamfered or rounded it off.

You have to enjoy doing repetitive tasks for this sort of work. Its a bit like porting a head. Its tiring because you must concentrate or you might loose a tool or a hand.

[shirtz]

sorry to thread hijack but whats this about using an astina engine as a base build?

my gf has a shagged out 1.8 astina 2001 we were going to send to the tip soon. should I be keeping this for a future build for my 93 clubman?