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Why does it ask for the smaller bit on the F motor? Does anyone have a possible explanation for this? Just curious...

I just installed brand new plugs, .032 gap, new rotor, new correct cap, new condensor, and magnecor wires. I didn't put in the new "contact breaker" yet because I don't really know what to gap and how to adjust it. I'm going to try and go to Shayne's soon to put it in and set it with a meter.

I still need to get the other manifolds on... Either tomorrow or friday night i guess.

870 miles and still going well. Hasn't seemed to lose any oil over the last 370 miles since the last oil change either. The oil also seems reasonably clean, although i can't quite say the same for the rockers and springs up top. They're still just about as dirty as it was when i got the engine, maybe a little cleaner around the top where it squirts out on the rocker. I hope to get some M1 in there after a few more miles, gas is costing quite a bit though, premium...
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Kyle - '68 142(258k, 71 b20b, SU HIF6s)

The running clearance is a fairly arbitrary figure that a cam designer starts with. A & D grinds are designed to run with .012" of clearance when measured at the lobe, the C grind is designed to run with .015". A B20 rocker ratio is close to 1.5 so you should run with .012" * 1.5 = .018" at the valve for A & D grinds & .022" for the C grind. Overly tight exhaust clearence will hurt fuel economy & bottom end torque, overly tight intakes hurts power & economy everywhere. A, C & D grinds have linear clearence ramps, so always err on the loose side.

Probably because the injected engine will maintain acceptable idle smoothness with the tighter lash, and therefore be a bit quieter. If there is one failing of the B20 engine, it is the noisy valve train, and the fibre timing gear.
Why the Europeans took decades to discover the hydraulic valve lifter, and then behave as though they invented it, and charge huge money for them, when Chev had been doing it for years (and at a cost of about $2.99 a lifter) is beyond me.
Breaker point condition is really important Kyle. It is arguably the greatest point of wear in the ignition system, after the plugs. Set them at a loose .016, and use breaker point lube (silicon grease) only on the rubbing block. No axle grease....
Rhys

You will note the different cam profile. The clearance spec is usually tied to the cam dynamics.
Phil has mentioned that setting the "B" engine to the other spec will release a little more power at the cost of losing some fuel economy due to greater scavenging, loss of some exhaust valve cooling time, and a slightly rougher idle.

Mike!

The C is really forgiving, and I don't understand why Volvo called for such large lash. I've run them down to .012" or so before noticing any drop in low end or idle quality, assuming the rest of the motor is retuned to match.

Valve cooling is no problem as long as there's no detonation. They still get tons of seat time.

No, I am NOT recommending that anyone run theirs that tight, just clarifying about old experiments of mine. I do think that .016" hot is safe for any decently tuned motor (repeat: decently tuned). Whether or not you like the way it runs set like that is up to you.

Well I like it. I'm running .010" on the intakes and .012" on the exhausts with my C-cam. Probably just about gives it D-cam characteristics with 0.018" orso...
I also ran this thight valve lash om my B18A and B20A long time: very nice and quiet.
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)

I'm with ya. I never understood the reason for specifying such a loose lash other than allowing for a lot of seat time. It seems to me that the later closing would be nicer to valves anyway as you are down on a deceleration ramp rather than slapping them closed. Besides, as I considered the issue, greater overlap would allow for some of the (cool) intake charge to wash over the exhaust valve.

On the other end, opening sooner will put more lateral load on the lifters (tappets) and their bore increasing parasitic losses (slightly).

I say be resonable but don't get carried away in either direction.

Mike!

p.s. I had a triumph i worked on come in with clearances at .008" Way tight but it had flat cam so it would not run with any more lash (no overlap).