questions on reconditioning the m20 head

[darien28]

ok, just got an "i" head relatively good condition except for a few bent valves which I think was due to the head sitting on the valves. I am in the middle to taking it all apart right now and was wondering about the best way to clean everything and what to replace while it's apart.

I plan to bust out the dremel and mildly polish as much of the head as I can get to, as well as port matching the intake and exhaust ports to the gaskets. here are my takes on the initial inspection of the parts... but I'm no expert since this is my first time playing with it...

325i m20 head - 110k miles at time of removal

valves - a few bent... should I got with oversized valves since I'm prolly going to have to regring the valve seat anyways? and where shoudl I get the oversized valves?

rocker arms - they look fine to me, but some say to jsut replace them. are there upgrades for this? they don't seem to have any wear on them.

cam - looks fine, but since I'm building a 2.8l stroker turbo motor... should I look into a new grind from racetep? car must still be streetable since it's going to be my daily driver, so I don't want to skew the powerband too much...

valve springs and other parts - they look fine to me... it's already got the dual valve springs, shoudl I do anything in this area? Ti valve retainers? heat treated valve guides? o.O

head itself looks fine, no cracks, no discolorations...

ALSO, when I get all the stuff and start putting it back together, what should I lube it with? can I jsut used the regular amsoil motor oil that I run in my car? or is there a special assembly grease that I should use?

thanks.

--crossposting in DTM and r3v...

[rwh11385]

ha, I was just researchin and thinkin about this. My rocker arm broke and I considered my options and what things I should do. (I ended up buying a recently rebuilt head, but anyway....)

Valves - Ireland Engineering used to sell oversized valves. They weren't that much more expensive I believe, but you have to weigh the costs and benefits. With a 2.8i turbo, they might be worth it. Dave Adams did some calculations about the valves. http://www.davelength.net/car/engine.html

I will send the head in for a rebuild, match porting, flow work, and have them install a new Schrick 272/272 cam. I will
also be adding +1mm stainless steel valves, which works out to be a sizable difference in surface area. The existing
seats can be ground to accommodate the increased size.Here is a comparison of area for the valve sizes:

Diameter Area [pi * (r) * (r)]
Stock Intake 42mm 1384.74mm²
+1mm Intake 43mm 1451.47mm²
Increase +66.73mm²

Stock Exhaust 36mm 1017.36mm²
+1mm Exhaust 37mm 1074.67mm²
Increase +57.31mm²

Dave got them from http://www.vacmotorsports.com/ for $411 as he wrote on his parts page: http://www.davelength.net/car/engine_parts.html
Might as well list all the good sources and suppliers now, and refer to them later.
http://www.davelength.net - Click on the white Mtech Cabrio, and go to his modification articles, lot of good stuff
http://www.strictlyeta.net/index.html - great source for 2.8i build, with complete parts list he used.
http://www.racetep.com/bmwothers.html Top End Performance
http://www.kormanfastbmw.com/e30engin.htm - Korman
http://www.bmw2002.com/ - Ireland Engineering
Matt325is - will be a great wealth of infomation as he has a 2.8i turbo.

Rocker arms - I believe Top End has stronger rocker arms and I know Korman does. Some believe that re-using rockers are fine, as long as there is no noticable wear.

Cam - Dave used a 272 cam on his 3.0L. Some use more extreme cams. Since you are turboing, maybe mild is better. (Back in my honda daze, aggressive cams did worse than stock on turbo motors. Boosted air doesn't need the longer duration to fill the cylinders. Ask Matt what he runs. Maybe ask Stu or call his dad to see what they think. My guess that something like 288 would hurt a turbo performance........

Valve springs - BMP recommends Ti retainers only for racing applications. I dunno if you need them. Maybe call one of the tuners - Top End, Korman, or IE and see what they think.

I'd have a shop check for head for sure. Pressure check, dye test, or whatever...... Hate to have that missed crack rear its ugly head at 6k rpm and 6psi of boost!

Someone mentioned using some sort of white grease to assemble the head with......

[darien28]

another thing, while I was removing the rocker arms from the shaft, the shaft on the exhaust side seemes a bit stiff and difficult to slide out. The notch for the rocker arm retaining clip at the end of the rocker shaft that is closes to the timing belt coused some problems as it scratched the inside of 3-4 of the rocker arms. the scratch isn't any thing big, but there were some metal shavings inside that 1mm wide slot in the shaft. Will this be a problem? I don't see this as a problem since that pivot point/joint is well lubricated. Any suggestions?

[RedBaron86325]

There shouldn't be any problem re-using the scratched arms. When re-assembling, place the shaft in the freezer for about 30 minutes and warm the arms with a blow dryer or heat gun. It will make the assembly a bit easier.