Piston piece

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green1

green1

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I got a crap macdaddy camera that I can't work. Maybe someone can edit the pic.
# 6 piston has a piece missing, you can see the ring. How bad is this?
70 10.25 340. no ridge.

piston.JPG
 
Man I wish you had a better camera. :) If the ring land is broke, you need a need a new piston. Sorry man. That's a drag. It looks like it may have been caused by detonation but it's hard to say without a better pic.

Some pistons have a notch that indicate the front of the engine, is that the case?
 
Are those hypereutectic pistons?

Did you do the math example=bore 4.060 x .0065=.026 for street natural aspirated.

If not the ring ends butted together and broke the land above them.


Buy 1 piston and lighten to same as the rest, hone & clean the cylinder and install the piston/rings [properly gapped] a new bearing and your good to go, though if the bearings good you could reuse if desired.jmo

By the way, nothings wrong with installing a piston with the notch backward UNLESS the valve reliefs are insufficient in providing valve clearance.
It'll actually pick up the torque a lil=less friction, see they put a lil offset in the pin bore as to keep the piston against the cylinder wall to keep it from rocking around=making a lil noise, the kind grandma didn't wanna hear out of her new car.
 
I'll try again in the Am; unknown engine; original 70 pistons, I think. Castings say 70 340 block, Pistons are out of the bore in places, Like 1/3 with a little dome, is out..17" . Valve reliefs cut in. I can't remember if this was stock 10.25. No ridge, and the bores have a chamfer, right at the top 1/8".
Double notches to the front. 2.02 j heads. And the unknown cam that wants 30 degrees at idle.
 
your compression needs to be checked with the vac advance dissconected and you wanna get a @ idle reading and 3000rpm full/mechanical advance reading then report, otherwise it sounds you're 10.25 is really 8.9-1 or at least the cams bleeding it off [dynamic] to look that way, cause thats a lo of initial to put a load @ low rpm and not ping.

What the cranking psi and the cams @ .050 duration, if you can find out.
 
It appears to me those are the stock pistons that came in a 1970 engine. I have a set just like them sitting on a shelf in my shop that are .030 over. If you need 1 or 2 let me know and I'll send them to you.
 
1wild&crazyguy said:
Are those hypereutectic pistons?

Did you do the math example=bore 4.060 x .0065=.026 for street natural aspirated.

If not the ring ends butted together and broke the land above them.


Buy 1 piston and lighten to same as the rest, hone & clean the cylinder and install the piston/rings [properly gapped] a new bearing and your good to go, though if the bearings good you could reuse if desired.jmo

By the way, nothings wrong with installing a piston with the notch backward UNLESS the valve reliefs are insufficient in providing valve clearance.
It'll actually pick up the torque a lil=less friction, see they put a lil offset in the pin bore as to keep the piston against the cylinder wall to keep it from rocking around=making a lil noise, the kind grandma didn't wanna hear out of her new car.
Click to expand...

i had heard of this b4 that in a stock 318 installing all the pistons backwards and picking up 15 horse at the cost of some noisy piston slap.
 
could be worse, I've seen the entire top snatched off a piston before. That was a 4 cyl. pinto engine in a dirt track racer. Failure was due to too lean thus too hot.
 
Heads and plugs read rich; don't know the history though. No ridge at top of the bore. I think I'll just run it.
 
I doubt it was ring butting if it was only that one hole, and only that one chip. But, it IS possible. Detonation can also do that. If it were me, I would not run it like that. The broad side fot he ring is not supposed to be exposed to combustion gasses and the ring seal in that cylinder will be... odd at best I think. Pull a piston and measure the ring gap. If it's less than .021 and that's a KB hyper, the rings butted.
 
OK, I decided to replace the piston. Next question; New un-fired used 727 in it. Some fluid in converter, none in trans cooler lines or radiator. How many qts?.
Because I seem to be going to the place, where I pull the timing cover and figure out what cam is in it.If it is wrong, needs replaced. My problem is, I don't want to be breaking in a cam at the same time I am checking trans fluids.
For you gurus- Intake off. Anybody have a program, if I put a dial indicator on the cam from tdc to tdc, on the lobe; rough estimate of duration?
Close would help, as I'm still trying to figure out the 30 degrees initial timing issue.
 
With a dial indicator you would be able to check the total lift, for the duration you'll need a degree wheel. Someone correct me if I'm wrong, it's been alot of years.

Dave
 
Have to look and see if they make a degree wheel that would bolt to and be corrected from the crank??? or could you adapt yours to the crank/balancer, rig a pointer....might get you in the ballpark..
 
Degree wheel bolt to the crank with the big bolt. You dont need to have the timing cover off to check it. But, you can't adjust it, and without knowing how bad the timing chain is, you will want to be careful to only turn it in one direction to eliminate slack.
 
According to the Dodge dealerships, I just scored the last factory piston available for a 70 340, sitting in the back shelf in PA. $40.
 
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