Test ran the new Raylar goodies
11-17-2018, 10:34 AM
#42
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Ryan watch out for the Tubulators being removed. Its a dam for the condensation aka kind of like a drip pan when it gets hot burns off the condensation. Also WHAT others do not know and I can careless what anyone says because we seen this inperson and even messed around with it in OEM training school many years ago for the 496 was the reduced exhaust section of the tubulator is there for a reason to speed up velocity ( no pun intended ) of the exhaust flow to PREVENT water reversion at idle speeds. Keep in mind when ever one scans any marine engine the engine idle does not stay AT ONE rpm only - it moves up and down .
Many people do not know this about why the tubulator was really engineered into the mix. PLUS the big one if I can find the pics to show removing it does not matter period..
Many people do not know this about why the tubulator was really engineered into the mix. PLUS the big one if I can find the pics to show removing it does not matter period..
11-17-2018, 02:34 PM
#43
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Dude just do the pistons. Keep the stock crank, rods and the piston kit will be a breeze.
The aluminum heads will bump your compression ratio from roughly 9 to almost 10. If you barf a piston with those new heads it will make you sick. Plus, then you can run the 206 cam next winter easy....
The aluminum heads will bump your compression ratio from roughly 9 to almost 10. If you barf a piston with those new heads it will make you sick. Plus, then you can run the 206 cam next winter easy....
BUP, appreciate the info. Mine have been removed since 2014. Exhaust has been off numerous times with no signs of reversion. Water mixing with the exhaust at transom vs stock has to be helping here.
Ok, pulled the engine this morning. Very easy setup to unwire/remove. I will be purchasing a beefier engine stand. This fully dressed 496 is a heavy beast! Don't feel comfortable with my current stand. I really like the built in stand of the 496 oil pan. You can just set it down on a flat surface.
11-20-2018, 04:21 PM
#45
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Gold Member
FWIW, skip the engine stand. Use you stand to re-assemble the crank and oil pump, put the pan on and stack up 6 cinder blocks with a piece of plywood on top. Then set the engine on it to do the heads, intake and accessories. The 496 oil pan is a flat natural stand.
12-16-2018, 07:39 PM
#46
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Update....
Before tearing apart the engine. I leakdown tested the cylinders. All good except #8 Exhaust valve is leaking. 45% leakdown on that cylinder. Rest were 22-24% cold @ 100psi. Heads went to the machine shop for some TLC. They called back and a valve job thru the Serdi machine will do the trick. Valve guides are ok. Intake valves are good. They are telling me the exhaust valves need replaced. Stock valves are Stellite faced and are starting to come apart on the stem tips. Stock scrubber rockers must have taken a toll. I'm going to check them out tomorrow and post some pics. New Stellite valves from GM are $26ea. Enginetech has Inconel for $20ea.
Good news..... With 567hrs the bottom end looks fantastic!!! Journals on crank look new. So much so I am reassembling with same bearings, rings etc... Installed the 203 cam today. Measured main bearing clearance. .002" on 1-4. .0025" on #5. Thrust spec is dead on. Installed crank. Cleaning up the pistons/rods now. Coated skirts on pistons look good. Block cylinder bores look good as well. I can see why many have gone well over 1000 hrs on these bottom ends.
Before tearing apart the engine. I leakdown tested the cylinders. All good except #8 Exhaust valve is leaking. 45% leakdown on that cylinder. Rest were 22-24% cold @ 100psi. Heads went to the machine shop for some TLC. They called back and a valve job thru the Serdi machine will do the trick. Valve guides are ok. Intake valves are good. They are telling me the exhaust valves need replaced. Stock valves are Stellite faced and are starting to come apart on the stem tips. Stock scrubber rockers must have taken a toll. I'm going to check them out tomorrow and post some pics. New Stellite valves from GM are $26ea. Enginetech has Inconel for $20ea.
Good news..... With 567hrs the bottom end looks fantastic!!! Journals on crank look new. So much so I am reassembling with same bearings, rings etc... Installed the 203 cam today. Measured main bearing clearance. .002" on 1-4. .0025" on #5. Thrust spec is dead on. Installed crank. Cleaning up the pistons/rods now. Coated skirts on pistons look good. Block cylinder bores look good as well. I can see why many have gone well over 1000 hrs on these bottom ends.
Last edited by Ryan00TJ; 12-16-2018 at 07:48 PM.
12-17-2018, 05:09 PM
#48
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I would replace the hypereutectic pistons if anything. Heads could be done with the motor still in the boat if necessary.
12-17-2018, 07:52 PM
#49
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01-01-2019, 01:48 PM
#50
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I'm keeping the stock heads. Ordered new GM Stellite exhaust valves. Should have the heads back soon. Thought about upgrading to Dart heads, but not worth the $$$ for a low flowing iron head. I did replace the piston rings with new Mahle 41902CP. File fit to .020" top, .022" 2nd. This is per Mahle's spec for marine use. End gaps on stock rings are really tight. Pistons installed and bottom end done. The Gen 7 crank scraper and internal pan windage tray are really nice features for stock.
Last edited by Ryan00TJ; 01-01-2019 at 02:24 PM.
