Bent Valve or Major Vacuum Leak

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jefflock

jefflock

69 Dart 408 10.08 best pass so far
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After making a pass at the strip last evening something wasn't right. No noises and oil pressure was fine. The motor won't idle down. Normally it idles at 1500 but last night couldn't get below 3000. My buddy took a rag and covered the carb opening. Then it idled down some. I've also been told that if you have a bent valve it could cause this. I would think it would be just the opposite. The motor is a 414 with Indy360 heads and the big block valve gear. Today I didn't have time to do anything with it except pull the valve covers. All appears to be normal there. Tomorrow I will run a compression test. Ideas, thoughts or suggestions? Thanks
 
The compression test will tell you real quick about a bent valve.
 
A vacuum gauge will fluctuate when there's a bent valve.
Is the power down? Does it run ok otherwise?
If it were a huge vacuum leak, rpm's would increase when the carb is partially covered.
Don't laugh at this one: Is the floor mat caught under the gas pedal? (Been there, done that method of "cruise control".
 
I would bet on the carb being the culprit. Check the carb throttle plates. If they get loose or bent, it will idle high. Also could be binding linkeage to the secondaries.
 
Pulled the plugs tonight and found #6 plug had been hammered on. Took the head off and about 1/2 of the intake valve was gone. So far it looks good but I will pull the other head to make sure. The piston top and the chamber have minimal marks and nothing very deep. I will just need to polish off the high spots.
 
Ohhhhhhh, man!!!! Lay me on some pictures.

Dang that sucks!
 
Pulled both heads, (Indy 360's) Only found some minor damage on top of #6 piston plus a couple of barely dectectable marks in the cylinder wall. Took the head up to the machine and he pulled both valves for #6 cylinder. The exhaust valve is bent also. Of course the intake valve is junk.
 

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shhot. i am looking at the pick,a nd seen what i thought was just oil sitting on the valve. then i had to relook, to see that part missing. sorry for your loss
 
Gone, No pieces to be found.
 
Wow, I can't believe that piece passed out the exhaust, even if it got hammered into a couple smaller pieces. I guess you were lucky, considering...
 
how old are your heads and what valves are in it not to often you see that ,if i were you i would be some p#@$@ off thats going to cause some problems if i were you i think i would have the rod checked to make sure you didnt bend one you must have bent a push rods that reely suck hope you fair out not to bad.
 
Make sure to double check and see that it is not back upstream in the intake manifold somewhere. Stranger things have happened. Would suck if it was and you didn't catch it goin back.
 
Got the valves and other items ordered today. The valve pieces are no where to be found. Not in the intake or on top of the other pistons. I will be sure to check the pushrods. I'd wouldn't like having to buy a new head from Indy.
 
You were really blessed with that. I bet the valve pieces are probably hung up in the exhaust system somewhere. I would be skiddish of the rest of those valves, though. Mightta gotta bad run. You never know.
 
Check the guide play. Im wondering if the bent exhaust nicked the intake during overlap and caused it to crack. Something caused interference. Maybe the locks sinking in the retainer. I would take a magnifying glass to everything that moves.
 
daredevil said:
I would take a magnifying glass to everything that moves.
Click to expand...

Indeed. I would go so far as to say to have it ALL magnafluxed. Would be cheaper than a third build.
 
Got the motor back from the builder. My son and I installed it and took it to the strip last Saturday. Car went 10.44 @ 128mph. The air was really bad. 6700' density altitude, 108 deg air temp, 150 deg track temp. I'm sure it will pick up on a better day.
 
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