I missed where the op said this was a magnum. He did say that he has adjustable rockers.
340 issue after camshaft change
- Thread starter Sabremech
- Start date
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Dale Davies
Well-Known Member
Pedestal rocker bolts can break with an aggressive cam, strong valve springs and the aggressive driving that goes with the previous two. That is the reason the OP has 7/16 7/16 studs. Adjustable push rods and lash caps get you back to the same situation this started with.
The OP needs to go through the motions of pull the intake off to visually check lifter status regarding off base circle and plunger travel position in the lifter bodies when the valves are on the base circle. With the intake off and a piston at TDC, it is easy to verify if it or its running mate are on the base circle. Those lifters will be lower than the running mate which will be on overlap and both lifters will be raised a bit. If the lifter bodies are both low but the valves are off their seats, back the adjustment off to get clearance like a solid lifter cam and then do the one finger zero lashpoint adjust. Then tighten down the adjuster nut 1/4 to 1/2 turn to set the plunger part way down in its travel.
Working with running mates and adjusting the cylinder at TDC firing has always worked for me.
You want sensitive adjustment, try 12V or 16V Detroit Diesel timing that uses timing pins of various lengths for different injectors, or a 2300 Cummins V12 with Top Stop injectors.
Scody21
Just send it
I get it. I said in post 2 to pull the intake and front cover off and see what the heck is going on. Clearly there’s some issues, and a bunch of really smart guys here have thrown a ton of info his way. I’d say the best thing would be the the OP to step back, regroup, read this thread, figure out if he’s got a LA motor or Magnum Motor, take a deep breath and pull the intake/ timing cover, lube / degrees the cam, pull the oil/ distributor shaft and get the thing set all back to zero...
Dale Davies
Well-Known Member
I agree on degree the cam to verify. If it is off the problem could be an issue with one of the timing gears. A 340 will be a LA engine as the Magnums came much later. And I made a mistake thinking the OP has the 7/16 7/16 rocker studs. That is another poster.
Once the timing is verified by degreeing, the adjustments can be gone through again. I feel for SabreMech as pulling wrenches for 25+ years I have had an issue now and then that required going and having a coffee before wrenches started to fly, like when I was younger. I have a tool box that has a hole where a needle nose plier stuck in it during a fit of frustration.
Rarely is a cam grind done wrong these days with CNC machining used, but it can happen. If the timing is off, I would check the timing set on a known quantity alternate engine that can be degreed and then swap in the suspect timing set. Whether the timing set or the cam, send the incorrectly manufactured part back for another or refund, if that is proven the issue.
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Dale Davies
Well-Known Member
Degreeing is not exactly a "tuneup" procedure but to verify proper machine work on the cam.and timing set. It does allow changing cam advance or retard as desired by your application to tune where maximum torque occurs. This is accomplished with offset keys or bushings and drilling the cam timing gear index pin hole oversize to fit an offset bushing. Generally for street this is not required, but verifying correct parts manufacture is.
Kendog 170
Let the boy go !
Hey Old thread , I'm curious . Whatever happened with this. Did you get it figured out ?
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