Line Bore 121 Head or Reduce Journal Bearing for 300 Sport

[jplips]

Plan is to install 300 Sportcam into 121 head with Solex PHH40.

Have a hard time finding speciality machine ship in Houston that can perform line boring. More machine shops seem to be able to reduce second and third journal bearing with 2 mm to fit the 121 head?

Anyone has done this before with satisfactory results after 5000 miles??

Second question to the forum is that most posts recommend a 292 cam for street use. Would a 300 Sportcam with Solex PHH40 be to rough idling for normal street driving?

Any comment/feedback is highly appreciated

[tim385]

Im running a 306 new billet Ireland Engineering cam (no line boring needed) are you sure you need to line bore ? 2x 45 webers idles fine, bit lumpy and good on the street , just gota stop yourself wanting to stamp on it for fun.Fuel usage is great ....it loves it !!!

[schwartzerritter]

ok for street!

13 years norris 300 cam and 40's

[jplips]

Dank je John voor je antwoord.

Heb je de cylinderkop uitgehoont voor de 300 sportcam of de lager diameter met 2 mm verkleint.

Met vriendelijke groet,

JP Lips

[jplips]

Hi,

Yes, the ID of the journal bearing of 121 head (121 025 008 09) is set up for the stock cam which has OD of 43/42/35 mm while the optional BMW 300 Sportcam has larger OD of 45/44/35 mm.

My theory is either to line bore the 121 head which is how the German engineers designed it for the optional 300 Sportcam. While I should know better not to mess with their calculations. Still have hard time finding a reputable machine shop in Houston area. We dearly miss Mike Perkins, who was the owner of Bavarian Machine Specialities in Houston and unfortunately for his family and all his customers passed away. Mike was a gentleman and professional for the local BMW racing and 02 community.

As a stubbern Dutchman, my theory is to reduce the bearing journals on the Sportcam with 2 mm to match the stock cam OD and take that small groove out of the second journal as well, see picture.

As a cheap Dutchman I do not want to do valve job and mess up the 121 head for future usage. What if the 300 Sportcam with dual Solex 40PHH is not stable enough for street use which is all I do with the 1972 Targa, then I can still buy a 292 regrind from IE and use the head?

So, this is my dilemma. I noticed in another post from a fellow Dutchman that he has no issues with the 300 Sportcam in Dutch traffic which is prone for traffic jams and 100's of stoplights.

Sorry for those who read that post and thought it was Dutch to them, well they were right I responded in Dutch without too much thoughts we were on an English board.

Hopefully a fellow 2002FAQ member has experience with reducing the OD of the BMW 300 Sportcam to the same OD as the Dr. Schrick journal bearings which do fit the 121 head.

Any feedback is appreciated.

Thank you

[jimk]

JP

Post a pic of your car. You don't see one like it too often.

Will we see you at MidAmericaFest this year?

Jim

[jplips]

Howdy Jim,

Thought you would recognize the 121 head in the picture Very glad with it, the valve guides need some work but no build up of anything. You certainly took care of it. I am definitively planning to see you all again at 2012 MidAmerica02Fest, such a nice group of mind-like 02 enthusiasts without too much fanfare is always positive. Will try to get other 02'ers from Houston to join us and meet the Dallas group somewhere in the middle.

With respect to the head would you be so kind to send me the VIN so I can order the correct replacement parts from BluntTech. Perhaps you can send it to bmwtarga@comcast.net if you want to avoid posting on the board.

I hope to salvage the 44 mm intake valves since those are scarce.

All the best

[jimk]

Howdy Jim,

Thought you would recognize the 121 head in the picture Very glad with it, the valve guides need some work but no build up of anything. You certainly took care of it. I am definitively planning to see you all again at 2012 MidAmerica02Fest, such a nice group of mind-like 02 enthusiasts without too much fanfare is always positive. Will try to get other 02'ers from Houston to join us and meet the Dallas group somewhere in the middle.

With respect to the head would you be so kind to send me the VIN so I can order the correct replacement parts from BluntTech. Perhaps you can send it to bmwtarga@comcast.net if you want to avoid posting on the board.

I hope to salvage the 44 mm intake valves since those are scarce.

All the best

02 Vin 2578384

Jim

[TobyB]

My only thought is that the head is a lot less rare than that cam!

Boring the head isn't particularly hard- the problem is that, without a

custom cutter (which takes time to make) it's time consuming to set up.

What about sending the head out to someone like VAC who does this all the time?

no help here,

t

[jplips]

I also thought it was not a big deal but local 02 supporting specialty shops in Houston could not assist. Talked with another Houston based 2002FAQ recently who has his engine at a local shop and does not even want to pass on their name??

I talked with folks at Aluminium Head Rebuilders in Oregon who told me they do not have the tooling to line bore the 121 head. Has anyone worked with this company before, would like to hear some feedback.

I did send an email to Metric Mechanic today to request assistance, see what happens.

Sorry for my ignorance but who are VAC?

Thanks

[Harv]

http://www.vacmotorsports.com/

John

[gracer]

The head needs to be bored out to let the cam lobes clear the cam holes. My machinist also has gone on to the great machine shop in the sky. Isn't Terry Saylor in Texas? You asked about Aluminum head rebuilders. They do great work on heads,, but I don't think that they have capability to bore out the cam holes. Ireland Engineering? G

[Guest Anonymous]

The head needs to be bored out to let the cam lobes clear the cam holes. My machinist also has gone on to the great machine shop in the sky. Isn't Terry Saylor in Texas? You asked about Aluminum head rebuilders. They do great work on heads,, but I don't think that they have capability to bore out the cam holes. Ireland Engineering? G

That is correct... If you grind the journals down.. The cam will just hang on the lobes. The reason no one does it is because of "cheap Dutchman". Want quality, pay for it. Dont ask a machinist to do an incredibly nice job without doing the head proper.

[jplips]

Thank you for the VAC website. After reading in what they specialize, I can see they should be able to do the job for me what no other machine shop in the Houston can do.

Appreciate it.

[jplips]

Hmmm, the question is not to spend less money but which option is available in the area I live in. No specialty machine shop I talked to was able to line bore the journal bearings. As a result, consulting on this great forum seemed like a logical step to gain valuable opinions and eventually... solutions. Now that I learned about the cam lobes do not pass the bearing journal, the search is on for a reliable machine shop with BMW experience.

Besides, if you are paying an hourly rate for a specialty machinist I prefer a line bore job in (soft) aluminum anytime over forged German steel of the cam journal bearings. The question is now which machine shop!