Engine builder experience needed - several questions

[95BMWIC]

I am in the mist of a bit of a delimna, I have a 91 325i that has copper colored metal flakes in the oil for the past 1000 miles. Although the engine runs smoothly, no knocking, I believe that either the rod bearings or the main bearings (or both) are beginning to fail. I have 220K. The car is now parked awaiting for a decision from me on how to proceed.

I have some time off this summer - so for the last few days I have decided to educate myself and dissect a 325e motor to see how hard it would be to perform a bottom end refresh. I took pictures every step of the way in case I had some questions for the forum. I have a bentley that I am using to make sense of it all..

First - I have a couple of questions regarding the crank.

According to the Bentley manual - the crank should have a color code (dot) to reference the size of the main bearings. This crank from an 1987 325e and has no color dots anywhere (not on crank, bearing, or "main bearing web" - whatever the hell that is) - so how would one know what bearings to order?

Since I have the crank out - and I were to do a bottom end refresh - do I need a machine shop to measure the journal diameters or polish it or check for balance? Is there something I must ask them to do?

Second - I have a bunch of questions on how to proceed - but I will only post a couple because my mind is not made up on how to proceed.

I am thinking about the possibility of ordering new oversize pistons from Pelican Parts +.25mm and having a machine shop bore and hone the cylinders for this. My current pistons (in my 325i) are 83.98mm

I assume this is the safest route, meaning I can use my stock parts(head, injectors, etc.) and refresh the bottom end with little issue?

Is there a better way to go? This is a daily driver and I only have a budget of $3K or so. What is I increase the size to +50mm? Pelican states this will raise compression 8.8 to 1 - so does that mean I need to upgrade other components?

This is a noobie question - but if I go +.25mm oversize pistons - I also purchase the +.25 mm rings.. correct? Then what rod bearings do I purchase? Or how do I know what rod bearings to purchase - I dont see that in the Bentley. I assume no matter what size pistons I go with, the main bearings will correlate with the crankshaft color code - correct?

I have several more - but if anyone could help this will get me started..

thanks

[packratbimmer]

I would invest in a micrometer, pull the oil pan and inspect the rod bearings. Then you can use the same tool on your 325e crank as well. You never know where a car has been over the last 24 or so years?

If you are planning to build a 2.7 with the 885 head, there is a ton of reading to do here as well as other places. You will need to think about issues such as rod length, pistons and combustion chamber size - and many other issues!

Most of the folks here who know the best advice are going to want to know your ultimate goal including engine management, budget (3K is doable) and such to be able to give specific advice.

With that said, I would get on the phone and talk to some local machine shops to get pricing and a feel for the quality of work that they can provide.

[95BMWIC]

First - I have a couple of questions regarding the crank.

According to the Bentley manual - the crank should have a color code (dot) to reference the size of the main bearings. This crank from an 1987 325e and has no color dots anywhere (not on crank, bearing, or "main bearing web" - whatever the hell that is) - so how would one know what bearings to order?

I may have the answer to this one - a standard crank (no modes and within factory spec) will have no color code..

I would invest in a micrometer, pull the oil pan and inspect the rod bearings. Then you can use the same tool on your 325e crank as well. You never know where a car has been over the last 24 or so years?

If you are planning to build a 2.7 with the 885 head, there is a ton of reading to do here as well as other places. You will need to think about issues such as rod length, pistons and combustion chamber size - and many other issues!

Most of the folks here who know the best advice are going to want to know your ultimate goal including engine management, budget (3K is doable) and such to be able to give specific advice.

With that said, I would get on the phone and talk to some local machine shops to get pricing and a feel for the quality of work that they can provide.

The only good engine I have is an "I" engine.

I have a couple of machine shops that can do the work - but my questions on the pistons are a bit more specific to the M20 engine. I didn't ask them about the crank specifically, cause I thought I could get that here..?

I do have a basic idea of a stroker -- as I can in fact I can use the 81mm crank in my "i" motor with custom pistons (somewhat like the MM kit) - in fact I had a long conversation with Jim at MM a couple of days ago - he basically stated I need a 10,000 budget for his 84mm pistons. He told me once you start adding compression on the bottom (using bigger pistons) you will then have constraints in the head (cam / porting) and need to match up both. and it is particular important in the baby 6. He ran out of time to talk and I ran out of money to consider an MM stroker..

So my next thought is if I want to perform refresh using an existing head what diameter can I increase without having to redo the head?

I feel confident I can be the general contractor with help - meaning I can install the crank, pistons and bearings - but need a little help figuring out parts and what measurements.. Most stroker threads are for the street / track engines and or (if not a true engine builder) have had issues with idling and performance.,, I want to avoid that if I can..

[jlevie]

At 220k it is almost certain that the engine needs an overbore (I'd go 50 over). You won't find color marks on the crank (I never have), but you pick the bearing color based on the rod and main journal sizes (measured to a tenth. Prolly best to have done at a machine shop as the micrometers with that resolution are a tad pricey. The shop will also be able to check for out of round wear on the crank.

The pistons should come with the proper rings and the shop will want to have them when they bore the block. You will also want the shop to refresh the head and you may need new exhaust valves.

Most of what you need to do is either obvious or in the Bentley.

[95BMWIC]

At 220k it is almost certain that the engine needs an overbore (I'd go 50 over). You won't find color marks on the crank (I never have), but you pick the bearing color based on the rod and main journal sizes (measured to a tenth. Prolly best to have done at a machine shop as the micrometers with that resolution are a tad pricey. The shop will also be able to check for out of round wear on the crank.

The pistons should come with the proper rings and the shop will want to have them when they bore the block. You will also want the shop to refresh the head and you may need new exhaust valves.

Most of what you need to do is either obvious or in the Bentley.

Thank Jim!

Any advice on brand? Stick with stock BMW - through Pelican? or can I order JE or other..

Also how do the rod bearings vary with the crank diameter? I only see those listed as standard (45 mm) or +.25mm through Pelican Parts..