Piston pin bad ?

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mbaird

mbaird

mbaird
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I have a knock in my fresh motor. It is a double knock ... It happens every second or 2 at idle . It could be more frequent... But definetely not engine speed...It goes knick..knock......knick.knock.....first one hac a little
Different pitch than the second .
I can feel it if I put my hand on the carb.

I have checked firing order several times...played with timing...adjusted vales...
I am afraid to run it long enough to pull each plug to isolate.

KB 107s No clips. Press pin, not floating.

What are your thoughts ?

Will it ruin engine to drive ? Should I just pull engine and fix right away ?
There is about 1 hr on engine.

When I described it to my machinest he asked how the pin would make it up through the carb ! I said " huh??? "... Maybe I need a new machine shop.....but they do build a large portion of the race engines around here and have built several for me in the past.
 
I am too paranoid to let it run long enough to warm up...I dont want to damage anything more than it already is.
Am I safe to do so ?
 
I'd better let some of the more experienced guys answer that. If it wasn't bored you might have a cylinder out of round enough to cause some piston slap. What is the oil pressure like? Can you locate it to one cylinder? If not, pull the fanbelts off and start it. Is the timing set in the ballpark? I would have thought he'd notice a loose wrist pin when he put it together.
 
Block was line honed , bored , decked , oil galleys enlarge to head .

Pulled belts..still there ... Played with timing and jetting..tried 3carbs , checked flexplate bolts and clearance to dust shield.

Never noticed it during breakin because I had an oil slinger rattling away.... Took that out. Rattle went away...

Everything I have researched points to pin issue.

Can you feel piston slap ?

The wierd thing is that is seems so long between the knocks...
 
I had a Dart sport, my daily driver. I blew off the oil filter, shut it down immediately. Pulled it apart and replaced one piston, I broke the skirt getting it out. I had a mild piston knock on a cold morning. It had good oil pressure and ran for another 20k till I sold it. I could hear it for the first quarter mile and then it went away. I could never feel it but could hear a muffled knock. How was the crank, any end movement?
 
Yet to check crank play but that has crossed my mind.
 
Thing is that I am trying to get this on the road by saturday so that my son "Cuda " can take it to prom. If wont wont damage anything further I will let him take it with knock.
It is tough to here with hood shut...lol

Full rebuild on car. It is just one thing after another ! Why do we do this again ?
 
The fact that it's intermittent makes it sound like it could be the crank moving back and forth. Good luck!
 

mbaird said:
Block was line honed , bored , decked , oil galleys enlarge to head .
Click to expand...

Did you happen to catch what Mike said in Post #16 in the other thread you were posting in?

If they are Hyper pistons, you will have piston slap if your piston to wall clearance is more than .0035". They need them to run tight, spec is .0015". If you have a new car/truck, most of them run super tight P2W at around .0008-.001"!
Click to expand...
 
My truck has had a wrist pin noise for years. I have trid to record it but there's too much backgroung noise so it never comes through. If your oil pressure & temps is good, and you don't hammer on it, it should be ok for prom. Do you know what pistons & piston to wall clearance you had?
 
Thanks for the input. I did read that post and I have no idea what he clearanced them at...

I don't want to be the dummie that just drives his car despite the potential for serious damage... If all else fails he can take the BMW convertable (89 e30.. Best 3 series ever made..) but he thinks the Cuda is cooler...right on !
 
Maybe i have a lifter that bled down before adjusting valves....maybe I degreed my cam wrong and advanced it too much...but that would make all the valves hit..

If the sound was more frequent it wouldnt be such a mystery....
 
I have awindage tray but the knock is too solid and infrequent to be that I would assume.
It did cross my mind..
 
Ok...so i ran it for about a minute.... The sound may only appear every now and then, no consistancy to it ! But it is a sharp clank ! May run for 10 seconds before making it. Always a double clank or hard metallic tick ! Almost like someone whacked a thick metal plate with a hammer. Metal on metal I would say? Could I have dropped a nut down the intake? I am very carefull about that !
 
Will try to download vid....you can hear it on the vid..
 
Are you sure the rotating assembly is not hitting the pick up tube?

Just seen you have a wind age tray. Possible it's hitting it.

Converter bolts loose? Exhaust hitting something?
 
Mad Dart said:
Are you sure the rotating assembly is not hitting the pick up tube?

Just seen you have a wind age tray. Possible it's hitting it.

Converter bolts loose? Exhaust hitting something?
Click to expand...


I think it is too solid of a clank to be a thin piece of mild steel. Besides , I would imagine it would hit every revolution.
 
I agree, check the converter bolts at the flex plate. If you work on old mopars long enough you have had them come loose on you at one time or another. Clean em up real good, loctite them & torque them down real good. Hopefullythat's it. If not you have to decide how bad it sounds to you & if it's worth the chance.
 
B&M flexplate ...checked bolts..

Trying to upload vid..for your viewing pleasure....
 
mbaird said:
B&M flexplate ...checked bolts..

Trying to upload vid..for your viewing pleasure....
Click to expand...

The B&M Flex Plate I have has 3/8 & 7/16 bolt holes in it. You didn't mix up the holes and use the 3/8 bolts in the 7/16 holes? Just something else to verify.
 
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