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Discussion Starter #1
i have an olds 455.
i know all about olds oiling problems!
i am on my seventh season since rebuild.

my question is, what would cause my 455 to suck(mushroom) 4 of my intake valves? 2 on one head and 2 on the other. 0 compression on three of them and 30lbs on the last???

all the rest have 160lb.
 

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Blown head gasket to adjacent cylinders is a common way. Did you pull the heads off yet?
 

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May have leaned out on fuel and the valves got too hot and tuliped. Seen it happen many times, especially on Olds.
 

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Heavy load and low RPM along with wide open throttle and no speed gain (lugging) will do it every time. Its real common on carburated engines. No vacuum at WOT and low rpm causes the carb to not have enough air flow through the venturies to draw out the fuel. Engine leans out, things get over heated in the combustion chamber. The intake valves are not designed for the heat spike and they go soft. Then the combo of cylinder pressure, heat, and valve spring pressures "suck" the overheated valve into the bowl.

Dragging a tube or wake board at half plane will get you as well.

Replace all the intake valves when you have the heads done, not just the cupped ones.
 

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May have leaned out on fuel and the valves got too hot and tuliped. Seen it happen many times, especially on Olds.
Duane Nailed it , common on this motor , high combustion chamber temps , too lean, not enough octane (needs 91 or better) , worse with the 10.25 (higher compression ) pistons Tom
 

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NW Spectraholic
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I ruined 2 intake valves running my Olds lean a few years ago. Back in the Q-jet days... :D
 

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Engine junkie
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Worn or low valve spring seat pressures will tulip a valve faster than you can shake a stick at it. Very common problem in a marine engines in particular.
 

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Discussion Starter #10
Heavy load and low RPM along with wide open throttle and no speed gain (lugging) will do it every time. Its real common on carburated engines. No vacuum at WOT and low rpm causes the carb to not have enough air flow through the venturies to draw out the fuel. Engine leans out, things get over heated in the combustion chamber. The intake valves are not designed for the heat spike and they go soft. Then the combo of cylinder pressure, heat, and valve spring pressures "suck" the overheated valve into the bowl.

Dragging a tube or wake board at half plane will get you as well.

Replace all the intake valves when you have the heads done, not just the cupped ones.
thanx, this sounds like me with a twist of under carberated!!
 

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Discussion Starter #11
heres the deal

i have been running a 650 double pumper since 2003. the thing was always hard to start. when it was cold i would have to pump the [email protected] out of it to start it. when it was warm, i would have to hold it to the floor to start it. when i would idle around, i would have to give it gas every 30 seconds to keep it from loading up and dieing!! other than all these hassles, cruisin to wot were always perfect(some how???????????) for 6 years, run hard!!!

i had my carb rebuilt.
fixed the starting and idleing problem.
it seems to suck my intake valves now!!!!!!!!
 

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NW Spectraholic
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What jets are in your carb? I'm running 72/84s in my 750 and getting a lean pop at 3500-4000 right before the secondaries open.
 
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