'69 427-400HP knocking
Thread Starter
Drifting
Joined: Feb 2001
Posts: 1,539
Likes: 63
From: new ulm mn
'69 427-400HP knocking
Okay, been fighting a carburetor leak and finally think I have it fixed. Took it out for a test run, everything running fine. After engine is warm, kick it down and bring in the secondary carbs. Everything is fine, engine running strong. About half mile down the road, coasting to a stop for a stoplight, it's like a switch was thrown. Engine is knocking like crazy. Sounds like marbles and there is no power, like half an engine is shut off. Limp three blocks home and engine is still knocking and won't idle. Start car (hard starting) and drive it into garage, knocking going away. About two minutes later, knocking goes away and engine is running normal. Anybody have an idea as to what is/was wrong and what should be my next preventative step? Was it stuck valves?
Last edited by loflite; Aug 22, 2012 at 11:46 PM.
Race Director
Joined: Apr 2011
Posts: 11,183
Likes: 3,335
From: North of Toronto - Ontario
Lifter collapsed? One would not have affected your power as bad as you described, several would be an odd coincidence, did your oil pressure drop?
Timing shifted? Not sure why it would get better.
I wonder if your advance stuck (either vac or centrifugal) and tossed the timing out to lunch and then loosened off and went back to normal.
Double check your timing and advance functioning
Mooser
Timing shifted? Not sure why it would get better.
I wonder if your advance stuck (either vac or centrifugal) and tossed the timing out to lunch and then loosened off and went back to normal.
Double check your timing and advance functioning
Mooser
Thread Starter
Drifting
Joined: Feb 2001
Posts: 1,539
Likes: 63
From: new ulm mn
Gas leak was external to the engine at the fuel line connection to the carburetor so there was no fuel in the oil.
Unfortunately I did not look at the oil pressure when it was running so poorly. The oil level is where it should be. The timing idea is interesting. Maybe it did get stuck and then worked loose?
Unfortunately I did not look at the oil pressure when it was running so poorly. The oil level is where it should be. The timing idea is interesting. Maybe it did get stuck and then worked loose?
Advanced
Joined: Nov 2009
Posts: 66
Likes: 0
I've had distributors going bad and do goofy things like this--the engine runs well, starts pre-ignition knock and runs like it's on half its cylinders, then resurrect itself after a cool-down. Glad you didn't dump gas in the oil.
Last edited by tonystar1; Aug 23, 2012 at 03:09 PM. Reason: clarification
Melting Slicks
Joined: Oct 2001
Posts: 2,065
Likes: 1,395
From: Halifax, Nova Scotia, Canada
Cracked/split rocker arm can cause those symptoms, especially the exhaust one. Engine fires on that cyl, exhaust valve never opens, then when intake opens, you get "blow" up the intake, really messes things up.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
An oil pressure reading will tell all
I've seen and have had one oil pick up tube fall off and the motor maintained oil pressure at idle but you get on it or turn a corner the motor would loose pressure.
I've seen and have had one oil pick up tube fall off and the motor maintained oil pressure at idle but you get on it or turn a corner the motor would loose pressure.
Last edited by hugie82; Aug 23, 2012 at 12:49 PM.
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Le Mans Master
Joined: May 2006
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From: League City Tx
I would drain the oil and have a look first....Cut open the oil filter and look for glitter...
Next I would pull valve covers and inspect everything in the valve train.
I have spun rod bearings before where they would make a bunch of noise, then get quiet..... atleast until the bearing shell spun again or came out all together... Usually resulting it a ruined crank.
I would get to checking everything pretty quick just to be safe... It would totally suck to put a rod thru a #s matching block.
Next I would pull valve covers and inspect everything in the valve train.
I have spun rod bearings before where they would make a bunch of noise, then get quiet..... atleast until the bearing shell spun again or came out all together... Usually resulting it a ruined crank.
I would get to checking everything pretty quick just to be safe... It would totally suck to put a rod thru a #s matching block.
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
If it helps mine acted the same way after getting on it hard once pushrods were bent. No big deal replace and drive
if thats the case may want to check your springs to make sure they are up to snuff
if thats the case may want to check your springs to make sure they are up to snuff
Le Mans Master
Joined: Jan 2006
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From: Butler Pa
Thread Starter
Drifting
Joined: Feb 2001
Posts: 1,539
Likes: 63
From: new ulm mn
Checked the easy stuff today over lunch. Coil wire is good. Worked vacuum advance with hand held vacuum pump, works good too. Was hoping it would get stuck for an easy fix. Fired up car today, runs and idles good. Oil pressure where it is always, idling or driving. Now onto the other stuff.
Thread Starter
Drifting
Joined: Feb 2001
Posts: 1,539
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From: new ulm mn
Latest and greatest news. Took the car out to drive to my mechanic, about a block away same thing. Started out with a weird rattle up front and then constant knock with severe loss in power and rough running. No idling. All the while, oil pressure is normal. About 40 psi at idle and goes up with rpms to about 60. Guessing a bearing?
Le Mans Master
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From: Gladstone MO
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There's a long step between a tick (valve train) and a knock (lower end). I'd be pulling the rocker covers and looking there, then dropping the pan and looking at the rods/crank/lower half of the pistons. a matching number block is not a real good place to take ANY chances.