Engine builders please chime in
TECH Addict
Joined: Dec 2010
Posts: 2,610
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From: Maricopa, AZ
But, if we consider the piston height (.025" in the hole), the valve lift, and head gasket thickness, odds are that 1 or more valves will contact a piston in the event of a complete timing chain failure. That would classify it as an interference engine.
Added valve lift, or decking the block or heads, or thinner head gaskets will definitely classify that LT1 as an interference engine. I've experienced this personally when my chain stretched and jumped timing by 1 tooth on the crank. But my engine is modified. I broke 1 exhaust valve and every single exhaust valve was hitting every piston.
Thread Starter
Teching In
Joined: Dec 2019
Posts: 11
Likes: 0
The gen 2 LT1 is a pushrod and isn't going to be listed as interference or not, officially. The odds of a timing chain failure is very small on a stock LT1.
But, if we consider the piston height (.025" in the hole), the valve lift, and head gasket thickness, odds are that 1 or more valves will contact a piston in the event of a complete timing chain failure. That would classify it as an interference engine.
Added valve lift, or decking the block or heads, or thinner head gaskets will definitely classify that LT1 as an interference engine. I've experienced this personally when my chain stretched and jumped timing by 1 tooth on the crank. But my engine is modified. I broke 1 exhaust valve and every single exhaust valve was hitting every piston.
But, if we consider the piston height (.025" in the hole), the valve lift, and head gasket thickness, odds are that 1 or more valves will contact a piston in the event of a complete timing chain failure. That would classify it as an interference engine.
Added valve lift, or decking the block or heads, or thinner head gaskets will definitely classify that LT1 as an interference engine. I've experienced this personally when my chain stretched and jumped timing by 1 tooth on the crank. But my engine is modified. I broke 1 exhaust valve and every single exhaust valve was hitting every piston.
In my case, a shop employee only manually rotated the crank 90, from 12:00 to 3:00, before I yelled at him to stop. We’re replacing the timing set. A compression check show’s good results on all 8, but number 5 & 8 were my immediate concern.
thanks for the input,
ed
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Verdad Gallardo Thread Starter
Teching In
Joined: Dec 2019
Posts: 11
Likes: 0
I think I have that tool, I’ll have to do some research on the various findings that it can provide.
This is (was) a very strong engine. Water pump was leaking, so naturally the opti was on the way out. And the front seals created an oil-fog for a very long time. What a mess that was. So since all that was removed, it made good sense to replace the timing chain and sprockets...
thx,
ed
Don't yet dismiss the opti being bad because of a coolant leak. I had coolant leaking on mine for a month before I figured out what was going on. I cringe at how many good AC Delco optis were thrown away back in the day. Crack it open and see if there is any corrosion. If not I'd put it back on.
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Teching In
Joined: Dec 2019
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Thread Starter
Teching In
Joined: Dec 2019
Posts: 11
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We purchased a rebuilt Opti from “The Opti Doctor”. He replaces the cap, rotor and bearing with new MSD, cleans up the internals, seals the unit and includes the vent mod. All we need to do is modify the water pump to drain away from the opti, and this repair should be good for the next 10 years, maybe more
