"The things you think are useless I can't understand"

Or so said Donald Fagen. Of course, he wasn't talking about a car. But, here, I am. What we've got here is a pretty darn nice 92 900S. I bought it at an auction knowing it had a bad headgasket, but not that it had a bad transmission, too. It was totalled by the prior owner's insurance company so if I got it back up and running, it'd still have a salvage title.

96,525 miles is all she's got on the clock. (The last mile wasn't actually driven: I ran her on jack-stands to be sure the odometer was working.)

So off to the crusher she goes. But not before I part her out...

Thought you knew c900 injector flow rates? Me, too...

I recently took for granted some data about cam timing and newgen heads; I found out that the info was wrong. For years, I've accepted the oft-cited injector delivery rates of 21 lb/hr for Turbos, 19 lb/hr for non-turbos. Wrong again.

From the Saab technical manual (conversions are mine -- divide cc/min by 10.5):

• 16V Turbo (2.5 bar reg.): 208 cc/min (19.81 lb/hr)
• 16V Turbo (2.8 bar reg.): 220 cc/min (20.95 lb/hr)
• 16V NA (B202i or B212, both 3.0 bar reg): 180 cc/min (17.14 lb/hr)
• 16V Lucas (3.0 bar reg.): 290 cc/min (26.62 lb/hr)

Incidentally, I found some data on the 24 lb/hr light blue Ford injectors (Bosch 0 280 150 947) that people use. Actual testing on a bench found these to flow 25.33 lb/hr @ 3.0 bar fuel pressure. (Flow measured by an injector cleaning/testing company.) I also found some data as quoted from a Bosch manual: 0280150913/947... rating is "255.9 cc/min @270kPa", or 24.37 lb at 2.7 bar. Converting this spec to 3 bar yields 25.68 lb/hr.

B204 head on B2x2 cam timing

You have read my forum posts about putting a B204i head (sometimes referred to as a T5 head)* on a B2x2 block. I’ve written about the cam timing change due to the head being thinner, and how it comes to 10 crankshaft degrees.

I was apparently wrong.

A well-respected person on a forum noted that the thinner NG head retards cam timing by 10 crankshaft degrees. I decided to do the math myself, and found him to be mistaken. Here’s the equation, from a book on engine performance:

D = 720h/NP

where
D = amount of retard (crankshaft degrees)
h = change in cyl head height (1mm or 0.0394") [source: Saab manuals. Basically, the NG and OG heads differ by a millimeter]
N = number of cam sprocket teeth (mine's 38 teeth) [source: me – I counted ]
P = chain pitch (mine's 9.525mm or 3/8") [source: Saab OEM chain company in Germany]

So running the numbers : 720*1mm/38*9.525mm = 1.989 degrees of retard at the crank, not 10.

I posted this information at an engine-building web forum for professional builders and got confirmation that it’s correct from two people using two different methods:

Quote:

--Since the slack side tensioner will take up the slop, the cam will retard 1 mm at the pitch circle circumference. --The circumference is 0.375" or 9.525 mm x 38 teeth = 361.95 mm. --Thus, 1 mm cam rotation = 1/361.95 of 360° or 0.9946 cam degrees = 1.99 crank degrees.

Quote:

I laid it out in SolidWorks(Hey, it's pretty close to the end of the day ! ), and got the same .9934 cam degrees, or 1.987 crank°.

Anyway, the moral of the story is this: DON’T BELIEVE WHAT YOU READ. EVER. Not even from people whom you believe to be knowledgeable, experienced, whatever. They can be mistaken, flat out wrong, etc.



*Calling it a “T5 head” isn’t exactly accurate, because these heads were fitted to many non-turbo engines that were controlled by Motronic!

B204i head on B212 block

I put a 96 newgen head on a B201 block that I had bored to fit B212 pistons. The ports flow better, and the intake valves are 1mm larger than B2x2 intake valves. My head has had some minor port work done, too.

Couple things:

• The newgen head is THINNER than the B2x2 heads; this retards cam timing 2 crankshaft degrees -- if you cannot tolerate two degrees, then you need to run cams from a newgen head, not a B2x2 head. Because you need a slotted exhaust cam to run your distributor, this means your exhaust cam needs to come from a non-turbo newgen 900 that ran Motronic (mid-90s).
• Use B2x2 cam gears. Use a B2x2 coolant temp sensor (at the front of the head).
  
• I neglected to measure combustion chamber volume. On the web, one poster says it's 50 cc's and another says it's 44.8. YOU SHOULD MEASURE IT and are an IDIOT if you don't and put a head on to find it doesn't work right (this, coming from an idiot who didn't CC the head first).
• The B202 intake supposedly does not fit without modification. I was able to get a B212 intake manifold to bolt on without modification; however, the port matching is VERY close, and my machinist asked that I do everything possible to mount the manifold as high as possible with respect to the head. After 20k miles, it works perfectly.
• The head can be modified WITHOUT welding: your machinist needs to mill out a space to fit a plate of aluminum to bridge the space between firewall-end timing cover bolt holes. The plate is epoxied in.
• For power steering, see pics below. For AC, you're on your own, but could do something similar to the PS bracket I fab'd.
  
• For a good online calculator, see the excellent not2fast website.
• This is an INCOMPLETE LIST of details. YOU are responsible for making your own head swap work; reliance on a some online "recipe" from some anonymous source (that'd be moi) is folly.
• When I have some time, I'll try to add more details. In the meantime, here are some pics (the first one I found on the intarweb, the rest are my engine)...

Here's the gap at the timing cover:

Here's the customized motor mount bracket:

A shot of the PS bracket, as well as the cover-to-head area post-modification:

Another shot of the bracket:
Hey, why not another pic of the bracket?

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