Leaning 340 slugs?

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HP2

HP2

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Hi everybody,
Got myself a 71 Duster a couple of years ago, seller had no clue of engine internals or nothing else but I got a good deal and bought it. Haven't had time for it until now.
340", Eddie heads, Torker intake, expensive red dp carb, newer crap MP distributor, Hooker Comp headers... that's what you can see.
Fiber glass hood and bumpers, subframe connectors, full interior, drag radials... Will see mostly short trips and some visits to the 1/8-mile. Stalls around 3,000. Would guess 3.91 gearing. Manual valve body.

When the heads got off I found this. All the pistons are higher on right hand.
They are .010 over the deck on left and .035 over on right hand.
Just gotta ask if someone has seen this before?
I have very little experience from little engines and this is the first 340 I have worked on.

Engine has been run like this, I thought it run like pig so did a comp test and found 150-154 on all cyl except for #1 that had 0. Exhaust pushrod had stamped a hole thru the stamped OEM rocker and intake pushrod was bent. No signs of piston/valve contact (piston on pics) so prolly due to over rev.
I will take it apart and check bearings and everything and give it a quick honing.
Did some measurements and cam should be a MP 292. No signs of wear and lifters also look fine. CL is retarded 4 deg, is that good?
Have a set of 273 rockers that I will use.
Edelbrock heads seems untouched that look fine. Single springs.

340 piston.jpeg


340 piston2.jpg
 
Is the block square??? (Are the head decks flat???)
 
Block needs to be squared up and decks equalized. My 383 was .012 off one side to the other. From what I can see, looks to need an overbore while you are at it. torque plates and mains torqued to spec.
 
Yes, the high compression 340 had positive deck pistons. The Edelbrock heads you have are most likely the 60179's that have a 0.060 relief cut for the positive deck pistons. You can have the block deck squared to even them up. If you replace those pistons I would get the same type unless you plan on replacing those heads. 65'
 
The stock stamped rockers are prone to punching out, especially once you start going with heavier valve springs. I have seen stock 318's do it as well. The rockers are thin in the pushrod cup area. The Mopar performance replacement rockers were advertised to be thicker to help resolve this issue. Not sure if they make them anymore.
Generally if your stepping up the cam and springs you should consider going with an iron rocker or aluminum roller.
Im going to guess someone milled the deck one one side but not the other or more on one side for whatever reason. Hell, could have came from the factory that way. Depends on what your doing with the engine. Might be better to leave well enough alone if its just a street car.

You said it apprears to be a 292 cam. Would that be the old MP 292/508.....loved that cam. That would be pushing the stamped rockers on the edge and eventual failure.
 
I'm not convinced that the Piston wasn't designed that way it looks like it could be an 11 to 1 TRW forged piston I have never had a set but if I recall they pop up on one side. Punching a push rod to a rocker is pretty common specially when you start to run a cam as aggressive as a 509 the spring pressure that is required to stabilize the valve train is getting pretty near the limits of a stock rocker arm I ran that setup for many many years and replaced a couple of rocker arms it. My thought is that was a pretty hot little tamale in its day. If you had a rocker problem and we're not opening the valve you could have have zero compression in that cylinder unless you really want to tear that motor down I'm not sure that that is required. Feel free to PM me if you have any other questions
 
Definitely a aftermarket piston, not sure why it is higher on one side, all 8 are like that ? It would be hard to machine them at a angle in a latch.
 
If you have zero compression I think you have more issues than that rocker arm. If the valve was not opening you should still show compression. Maybe a bent valve?
 
MoparMike1974 said:
If you have zero compression I think you have more issues than that rocker arm. If the valve was not opening you should still show compression. Maybe a bent valve?
Click to expand...
If no air is allowed to enter the cylinder how can you produce compression,this is not a guess but something I just experience with my son's hemi . a push rod that had displaced from the rocker 0 compression put it back in place and problem gone.
 
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If every piston shows that same offset the issue is the top surface of the pistons not being perpendicular to the bore. The deck being a little out of square isn't going to show up with the same offset on each piston inline with the crank. Also, from that pic, the straight edge shows an air gap to the piston top on the right so that bigger gap to the deck may not be real.
 
When you say left vs right, are you talking drivers vs pass side?
I think stock 340 pistons had a "lean" to them on the top?
 
brian6pac said:
Definitely a aftermarket piston, not sure why it is higher on one side, all 8 are like that ? It would be hard to machine them at a angle in a latch.
Click to expand...
Yes they are all like that, and Yes it would be totally impossible to make that in an lathe - but it would be possible to mill them off square
 
MoparMike1974 said:
If you have zero compression I think you have more issues than that rocker arm. If the valve was not opening you should still show compression. Maybe a bent valve?
Click to expand...

When both valves are closed no air is moving. There was even a pinch of rust resting in the exhaust port.
Took the valves out and everything looks fine.
 
gzig5 said:
If every piston shows that same offset the issue is the top surface of the pistons not being perpendicular to the bore. The deck being a little out of square isn't going to show up with the same offset on each piston inline with the crank. Also, from that pic, the straight edge shows an air gap to the piston top on the right so that bigger gap to the deck may not be real.
Click to expand...

Exactly. All the pistons are higher on "right side" then on "left side". If the block would be off square piston #7 would be an inch above deck.
There was some carbon build up on the top when I took the pic and that's why you can see some light under the straight edge. I cleaned it later and used a feel gauge to do the measurements.
Bores look very good by the way. Cross hatch all the way except for a blank area at the top. You can barely feel it with your fingertips. Will be fine with a quick honing.
 
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