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Re: head gasket- honing- peening Posted by BFJRestoration [Email]  (#3230)  [Profile/Gallery]
(more from BFJRestoration) on Fri, 29 Dec 2023 17:46:20
In Reply to: head gasket- honing- peening, Alvaro Isla, Fri, 29 Dec 2023 13:06:45 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Others with more experience may chime in and correct my inexperience. Pic looks like your cylinder bores are free from issues
1. That's normal for the gasket to only have holes on certain passages. You'll even see a smaller hole on two and a medium sized hole as well. Helps with flow circulation
2. Ideally you'd have a smooth deck surface for the head gasket to properly seal. If you have very light scoring, I'm guessing it wouldn't effect the seal too much. BUT if you have anything more, I'd suggest getting the block "decked" by a machine shop. The layer that's skimmed off may help if the deck isn't completely flat as well. BE SURE to take the two aluminum end plates (the timing cover and the clutch cover with the "rear" main seal) as they will need to be bolted on as the top of them also comprise the deck surface. Check out where the head gasket overlays them to see what I'm on about.
3. The whole cylinder should be honed and a re-honing generally does not necessarily require an over-sized piston. The machine shop will measure the bore to see if it's in factory spec and then will give options from there. If there are medium or heavy scoring or rust spots, the machine shop will probably need to bore the cylinders out larger which would require over-sized pistons if they bore it out enough. The top of the cylinder bore is not usually touched by the piston rings (except for instalation and disassembly), so that's why it may look darker with burnt oil/carbon build up. The very top lip is usually given a slight chamfer to help make piston installation easier.
4. Shot-peening should be avoided in the cylinders if you're not boring them out as it adds small divots to help add a comprehensive stress layer to strengthen the surrounding metal. Those divots would interfere with piston ring seating and cause excessive wear quickly, even if done before honing, at least that's my theory. As for the rest of the block, looks like that may be a way to rid rust and oxidation so I guess it's okay???? Usually shot-blasting using softer media solves that issue. It's also gonna be a pain to clean every single nook and craney of the metal shot so it doesn't mix with the new oil and/or coolant. Also, from my understanding, the iron blocks for the C900 have a high magnesium content, are solid as a rock and are very strong from factory. Get too crazy and you'll need some forged internals...
5. Use some green plasti-gauge. The red stuff is usually for bigger stuff with larger tolerances. Check out the Saab Engine Manual in the Saab Manual section on here for all your engine spec needs
Disclaimer: I've only built one C900 engine... for now at least
->Posting last edited on Fri, 29 Dec 2023 17:50:40.
, Sat, 30 Dec 2023 08:01:58, Fri, 29 Dec 2023 17:46:20 <-- Viewing This Message
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