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Re: difference B engine to H engine Posted by Larry West [Email] (#1140) [Profile/Gallery] (more from Larry West) on Mon, 16 Nov 2009 09:58:00 In Reply to: difference B engine to H engine, alvaro isla, Mon, 16 Nov 2009 09:29:39 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The B engine is the Saab development of the original Ricardo/Triumph design.
The H engine is a further refinement of the overall design. The major differences are:
Removal of the "jackshaft". This shaft drove the oil pump, water pump and distributor. If you think of the B motor as 1/2 of a V4 (which it kinda is...), the jackshaft lives where the camshaft on an OHV V8 lives.
The Distributor was relocated to be directly driven off of the camshaft at the "back" (flywheel end) of the motor.
The oil pump was directly driven odd of the crankshaft.
The water pump was now driven by a belt shared with the alternator (later a matched pair of belts on the 900, though I don't think the 99 ever got the matched belts).
The camshaft was shortened, and a different style of chain tensioner was used.
The valve cover was now cast and machined aluminum instead of stamped sheet steel. The VC gasket was now an o-ring type, instead of cork. Manifolds remained largely the same.
The change to the water pump makes installing an H engine in a 99 that was not equipped with an H engine from the factory difficult. Just dropping the motor in leaves almost zero clearance between the WP pulley bolts and the firewall. Saab modified the flywheel to allow room in that area to work on the WP, as well as for the motor to move under normal use. DIYers who have done this conversion often hack out a larger than necessary chunk of the firewall, and rebuild it for clearance. Some just whack at it with a hammer, and a few find the right bits in Europe to weld in.
Saab 99s from 1981 or 1982 on, and Saab 90s all were equipped with H motors, mostly with carbs. They all had the relief in the firewall for the water pump from the factory. Also, the pulleys were slightly different, owing to the fact that those 99s didn't come with power steering, so the alternator belt was closer to the block.
(The Saab 90 was the replacement for the 99, which was a 99 from the nose to the 'B' pillars, and a 900 2-door from the 'B' pillars back. It was produced from 1985 through 1987.)
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