stroker blues

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duster451

duster451

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Apr 16, 2012
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Grand Rapids
im back at it ..i hope that you guys out there can give me some good advice...ok..i have a 70 duster 340 with a 451 stroker....it ran great on the break in stand and for a few rides up and down the road then got worse untill it wouldnt run hardly at all...upon pulling the valve covers and intake i found a bunt push rod and the lifter was out of the bore and jusy laying there..bad lifter?..easy fix with new lifters and a push rod?no visable damage to the cam...motor has hours on it and maybe 20 miles on it...old school with ground 440 crank..509 mopar cam..Too much cam?..full port and polish 906 heads...also with a 3.55 sure grip...what touqe converter?...i have a frank lupo 9 1/2 street strip ..dont think thats right...all the tranny did was run hot .also at some point the oil pressure dropped way down to like 6psi..im hoping that gas thinned out the oil while i was trying to figure out why gas was coming out of the exhaust..this is my first time so go gental......thanks guys .any more info you may need ill do my best...a "friend" built this for me but he has trouble returning my calls
 
6 psi and a bent push rod is no good. you may have eaten a cam lobe. if it were me i would stop everything and make sure you didnt lose the cam. losing oil pressure sucks.

welcome to the site, you will get plenty of advice on this one.
 
Oil pressure would drop when the lifter came out of the bore
 
correct...bent pushrod...lifter comes out...low or no oil pressure...
 
Your "loading up" issue could be down to the valve not operating -

OR

a defective fuel pump (if its mechanical)

OR

sticking needle and seat


I'd see how it behaves once you get it fired up again - but if it blows blue smoke - turn it off quick, because you'll be washing your bores.
 
unless your using high zink oil the flat tappet cam wont last, you have to buy the zink additive or just put a roller cam in it. good luck
 
Run high zinc oil even with a roller.... Had a couple bouts of the same situation but in my case the push rods didn't bend, they broke the (aluminum) rocker arm by jamming underneath. Sounds like your push rod came out (too short, not adjusted properly or rubbing on the head), bent under a rocker and allowed the lifter to come out, dropping oil pressure. Something bent the PR so carefully inspect the rockers on that cylinder and the rocker shaft before putting it back together with a new rod. I would also check the springs and retainers, at least on that cylinder.
 
Why did the pushrod bend? Uh, ya know, they don't get soft in oil and just squish up. Something bound up, the pushrod was the weak link and it bent. Valve guides too tight? Retainer to guide clearance? Piston to valve clearance? Did we over rev this baby? Did driving it around with the low oil pressure damage something else? 'Cause, "then it got worse untill it wouldn't run hardly at all..." Did excess fuel wash the oil off the rings and score the cylinderwalls?

Cut the oil filter open and check for metal in the element.

I think tearing this completely down and checking everything might be in order, bearings, clearances, gaps, cam timing, pushrod length, rockers and shafts as suggested above, spring installed height and blah, blah, blah.............or not.
 
IQ52 said:
I think tearing this completely down and checking everything might be in order, bearings, clearances, gaps, cam timing, pushrod length, rockers and shafts as suggested above
Click to expand...

i agrreee. if it were mine, it would be coming out for a thorough check of everything.
 
Yep. It's almost always an Exhaust valve not opening and causing the Cylinder to "load" up. Bad Cam? Stuck Valve in Guide?
Or totally weak valve springs that let the Rod pop out at high Rpm's but that usually comes on all of a sudden. How's the exhaust Cam lobe on the offending Cylinder? Think about all the compression in a cylinder. If the exahust valve don't open far enough, It's gonna bend the Push rod. I really don't know what else could cause it.
 
IQ52 said:
I think tearing this completely down and checking everything might be in order, bearings, clearances, gaps, cam timing, pushrod length, rockers and shafts as suggested above, spring installed height and blah, blah, blah.............or not.
Click to expand...


x3
 
ok....im going to pull it and go thru it...better be safe than sorry again...ill post again for updates and more than likely...advise...thanks guys....
 
well just pulled the head on the side that lost the push rod bent and i feel two grooves in it...dont have the money to rebuild it again right now...not sure what im going to do..any body want to trade for something that runs...going on three years and it has not left the garage...this sucks...
 
on the cylinder wall but its not scored liked it was dry metal on metal...i looked at everything and all still looks new....weird...even the cross hatch patteren is still visable in that cylinder...almost like it came from the machine shop that way...i tried to take a pict but you cant see it...think i might just put it back together and see what happens....
 
Sounds like something fell in the intake and scratched the cylinder wall and interfered with the valve.Closely check the piston top for telltale marks.
 
Have you removed that piston, if not I would to make sure you don't have a broken ring.
 
sounds like mabey camshaft breakin failure.@ "too much cam" That's a pretty small cam for a big wedge, but you're still going to want to check clearances properly, just to maintain the habit if anything.mabey a hung valve? Who knows... but you.. ;)
 
just incase anybody was wondering as to what happened,I ended up swaping in a stock 383 mag and trans..All is good now. Not sure what im going to do with the stroker combo...thanks to everyone who tried to help....
 
Hey everyone. It's been a long time but I finally drove my duster today. After typical life and some health issues I finally got her out of the garage. New carb and breaks and gas and it runs pretty good. Some hesitation off idle but hopefully just needs to be driven. I forgot how good it feels
 
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