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Re: 78 99 Turbo w/cracked head Posted by Larry West [Email]  (#1140)  [Profile/Gallery]
(more from Larry West) on Mon, 12 Jul 2010 05:58:02
In Reply to: 78 99 Turbo w/cracked head, Brian McHugh, Sat, 10 Jul 2010 21:18:49 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I hope you're certain the head is cracked. I've seen a few B- and H- engine heads declared "cracked" by local shops that ran on and on for years afterwards. Often, they display a visible "crack" near one of the valve seats, but this crack doesn't go through to anything, and never develops into anything more. One that was declared cracked and replaced I know for a fact ran for 50k or more afterwards, showing no signs of problems.
That's not always the case, of course, but I just wanted to let you know, so you could do your own, thorough, investigation.
As for swapping in a 900 motor, if you're talking about the "H" block (aluminum valve cover), that's rather a bit more work than just dropping it in. Of course, a 1979-1980 900 turbo motor is the same as is in your 78 99.
When sourcing heads, be aware of two things:
1) sodium-filled exhaust valves. These are on the 99 & 900 turbos, and on all 99/900s by 1980. The turbo needs them. They can be moved from the turbo head you have, though.
2) three-way-thermostat. Saab started using three-way thermostats in 1977. What this means is the thermostat has three states: closed, normal open, and hot open. The difference between normal and hot is how far the flat plunger extends. With hot, the plunger extends farther, and actually closes a path for hot coolant to take back to the water pump and heater, forcing nearly all the coolant through the radiator.
Heads before 1977 can't block this flow off. If the squarish thermostat housing is removed, the early hole in the head is a single, squarish mating surface. Later ones have this square split in two. Because it's a gasket surface, the head and thermostat housing must match, or the 3-way thermostat doesn't work 3-ways.
_______________________________________ Current: 2002 9-5 Aero Kombi Cosmic Blue 2000 9-5 SE sedan, Imola Red 1990 900S Rose Quartz, Auto Past: 1999 9-5 LPT Combi 1999 9-5 LPT sedan 2002 9-5 Arc 1990 900 5-speed 1986 900 turbo Convertible 1991 9000 turbo 1980 99 GLi 1986 900 turbo 1986 900 S 1991 900 turbo 1984 900 turbo 1976 99 GL
, Tue, 13 Jul 2010 14:53:39
, Tue, 13 Jul 2010 06:30:35, Mon, 12 Jul 2010 06:02:32, Mon, 12 Jul 2010 05:58:02 <-- Viewing This Message, Tue, 13 Jul 2010 15:33:28, Mon, 12 Jul 2010 06:19:15, Mon, 12 Jul 2010 12:07:44
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