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93 TBI 350

Heveychevy

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Okay so I bought this truck from my boss man who supposedly had the motor and trans rebuilt. Had the truck for about a month and started getting a EGR code and moderate miss under load. Replaced the EGR valve and solenoid, no code but still had the miss. Long story short, ended up replacing IAC valve, TPS sensor, distributor/dis cap&rotor, rebuilding the throttle body, and putting AC Delco plugs and wires on it. Now the truck would idle fine and even take some decent throttle taps but when you put it in gear it lost all power and wouldn't do much else besides backfire. Found out the valves were burnt and pulled the heads. The seats and all looked fine so i got replacement valves and lapped them in but now the truck won't start and I'm getting a popping sound through the throttle body. Anyone got a idea of what's going on or what I can do to fix this? Anything would be helpful at this point. Thanks in advance.
 

Wes Harden

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Since everything has been apart, my 1st guess, valve adjustment possiblity to tight. Distributor 180* out.
So question, if "New" engine had burnt valves is really new?
What if it is used, and the timing chain was marginal, only 1 back fire away from skipping a tooth.
Something that should be checked.
 

Heveychevy

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Yea Im about 100% sure that either my boss man ripped me off or whoever he had ripped him off because the "new" things I've seen on that motor were the gaskets. As far as the valve adjustment, I followed the Haynes manual witch had the "spin the push rod and tighten" method. To be honest I haven't done enough of them to really get a feel for what 0 lash is so I'll definitely try that first.
 

Wes Harden

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Yes but you need a helper.
Remove dist cap. Mark where rotor points. Turn the crank by wrench one way until you or helper see rotor move. Mark the rotor point. Turn the crank the other direction until rotor moves.
Ideally it should move immediately, but real world there will be a little slack.
I just remembered another item to check. Make sure the rotor is indexed correctly on dist shaft. They are pita and can be installed Incorrectly. If the cap ever wasn't on straight it will move the rotor.
 

Wes Harden

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Well I screwed up that procedure.
Mark the dampener, not the rotor.
If you look at the timing scale marked on the dampener, it will give you an indication of how many degrees of slop in your chain.
 

Heveychevy

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Okay I gotcha, I'm checking the valve adjustment now and if that doesn't give me any results I'll go from there. I sure do appreciate the help man, I'll be sure to post the results when I get it figured out.
 

Heveychevy

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Alright, so you were 100% correct. I had the valves adjusted a little more that a full turn to tight. I used a feeler gauge this time, I could only find my metric set so their about .020 shy of spec but i can at least crank the truck so I figure I'll just do a running adjustment if needed. I also had them set on the exhaust stroke instead of compression so that wasn't helping either. But anyway, I sure appreciate all the help and advice.
 

Wes Harden

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Good you figured it out. You can do sbc at 1/2 turn and be good. All mine hydraulic flat tappet sbc are 0 lash +½ a turn.
 

Heveychevy

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I ended up doing a 1/2 turn then like half a tooth of the ratchet I was using to try and make up for the difference in the feeler gauge
 

Wes Harden

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0 lash is feel thing takes a little practice.
I start by getting the rockers close.
Pinch the push rod between thumb and index finger, jiggle the rod up and down while slowly tightening the rocker. Once the up and down is gone, I spin the the push rod till I feel resistance. This is the felt experience you need to develop, but is not terribly critical on a sbc.
At this point give it another 1/2 turn, and move on to next in sequence.
 
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