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Erratic Knock WTF?

K

K5CuRbDoG

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To start i have a 79' with a i believe is bone stock 350. For starters I have been trying to figure out a miss, then just recently its a knock. I have replaced coil, plug wires, cap and rotor, plugs, and numerous vacuum lines. The miss went away for a few day to return as a knock, took the truck down to a friend for a second opinion. His suggestion was to recheck all the vacuum lines again that's when i changed a number of them. Knock is still there but is not a constant knock when its cold it knocks till it warms up then gone, i hit the accelerator and fine for half throttle and starts backfiring thru induction. last night on way to get lunch it was knocking till i put the pedal to the floor nothing ran like a scalded ape then let off started knocking again. this is erratic i want to throw a crate 572 in but wife wont let me please help?????????:dunno::doah:
 
Do you have access to a timing lite? I would check the timing and make sure its not too far retarded/aadvanced.
 
Timing and compression i didn't check because i have no issues with starting just turn key and go.
 
You should check the timing first! It's quick and easy and sounds like the issue. Maybe you have a loose distributor hold down bolt. Can you twist the distributor at all?

Back firing through the carb often is either timing or a burned intake valve.
 
Could be a broken valve spring or sticking/ broken rocker arm holding an intake valve open maybe,letting it backire thru the intake..I've seen a dead lobe on a cam cause intermittent ticking and knocking noises and if its an exhaust lobe thats failing,it wont let the exhaust escape and it'll try going out thru the intake next time the intake valve opens..
 
To me it sounds like a valvetrain issue just like diesel4me said.. Pull the valve covers off and have a look.. Its easy and harmless to check
 
Well i did pull the valve covers off before when i had the miss. Nothing noticeable then but i did again today and started it up. Only to find that my number one intake rocker was barely moving so rebuild time. Gonna crunch some number to see if i can do a full build with the 383 stroker and cam, or just a top end build. Im pretty sure its a flat spot on the cam cus i have squish in the lifter and none when running..
 
Sounds like a flat cam. If it wasn't using any oil before, and had good power before I'd look at swapping in a new cam, lifters and TC. Relatively cheap, which gets it back on the road. Then take your time saving for the 383 build you want to do.

If you decide to do a cam, pay special attention to cam break in oil and additives. It's pretty easy to wipe out a lobe on a new flat tappet cam...

Rene
 
Well been some time since ive posted but rebuilt my top end and yes 4 lobes were no more but it ran craziest thing ive seen. Now im looking to do the 700R4 conversion but wanted to know if anyone has used the monster transmission 4x4 700R4 and if still modifying needed to be done, also need direction on transfer cases mine is going out i got the p203 wanting to upgrade:dunno:
 
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