Engine Problem Challenge
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Joined: Apr 2004
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Out of the blue stupid wag, but based on watching two guys kick & push a motorcycle for an hour trying to start it: PULL the carb and see if the rag someone stuffed in there during a change is still in there.....
Senior User
Joined: Dec 2007
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I will see if I can get my hands on a thermometer to check cylinder temps. Is there an easy way to check to see if the intake is blocked? It was used and may very well be restricted with something. If there is something else wrong with a cylinder, shy of compression and leakdown problems...what else could be wrong?
Pulling the valve covers and checking the lift and duration of the valves might be something too. You might have a flat cam.
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Junior User
Joined: Jan 2005
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Will do ASAP. I replaced the carb myself, but will pull it again to peek into the runners with my scope to make sure. I will also check for rocker arm movement to be sure they each move the same. I have not thought of a cam problem. The driver's side head was taken apart when I replaced a valve and lapped them all.
As always, you guys are providing me with great ideas!
As always, you guys are providing me with great ideas!
Junior User
Joined: Sep 2007
Posts: 57
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Back in the autoshop in High School, we worked on a car that had a dead cylinder and what it ended up being was a vacuum leak to that single cylinder, causing a mixture problem (too lean) so it was not firing. A couple vacuum caps and it was running strong again. Is it possible that when you put the manifold on, one of the ports didn't seal (crushed or folded over gasket)?
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Junior User
Joined: Jan 2005
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I will check as close as I can for something with a gasket. I also bought a thermometer today to check cylinder temps. Another customer at the store mentioned a possible internally shorted spark plug which he ran into before. The majority of techs I talk to seem to think it may be a flat cam or faulty valve components.
As soon as the rain stops, I will check the cylinder temps to find which ones are not firing, then try swapping out new plugs, look for vacuum leaks, fuel actually getting to the cylinder, valve lash, and for rocker arm movement while the engine is running. Surely this has to be the final stretch!
Hopefully, I will find the problem. If it wasn't for you all, I would have given up a long time ago and junked it!
As soon as the rain stops, I will check the cylinder temps to find which ones are not firing, then try swapping out new plugs, look for vacuum leaks, fuel actually getting to the cylinder, valve lash, and for rocker arm movement while the engine is running. Surely this has to be the final stretch!
Hopefully, I will find the problem. If it wasn't for you all, I would have given up a long time ago and junked it!
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Junior User
Joined: Jan 2005
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I pulled out the #6 plug which was black and wet. The others seem normal. When I replaced the plug with a new one, no change. The thermometer read about 100' degree difference between #5 & 6. I pulled off the driver's valve cover to look for something obvious and started it up. Nothing seemed abnormal. All rocker arms appear to be moving uniformly. Gaskets appear to be in order. Even tried the propane trick around the intake and carb.
Post Fiend
Joined: May 2004
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From: Lakewood, Ohio
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Yes do the compression test already!
If it won't build good compression in that cylinder, it won't create good vacuum in it either so it won't get enough air/fuel to burn and make power/heat.
If it won't build good compression in that cylinder, it won't create good vacuum in it either so it won't get enough air/fuel to burn and make power/heat.
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Joined: May 2007
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did you remove both fuel pumps?most of those trucks had a low pressure pump in the tank and the high pressure on the frame.
and i disagree with an earlier post about the 351m being a big block.but thats another thread all together.
and i disagree with an earlier post about the 351m being a big block.but thats another thread all together.
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Junior User
Joined: Jan 2005
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I did a compression test and a shop did also. As far as the fuel pumps, I replaced the frame mounted high pressure pump with a new low pressure one for the new carb setup. The pressure gauge I have says it providing 5 psi.
Today I will pull the carb and check for blocked ports in the intake. If I don't see anything obvious, I will probably do one of three things:
1) schedule a visit with an "old-school" shop
2) find another motor to drop in
3) have this motor broken down and gone thru from the bottom up
If I get my paws an another motor, what would be the best fit "drop in" replacement for a 351w? A 460 would be great if I find one, but a proper running 351 should provide me with enough power.
Today I will pull the carb and check for blocked ports in the intake. If I don't see anything obvious, I will probably do one of three things:
1) schedule a visit with an "old-school" shop
2) find another motor to drop in
3) have this motor broken down and gone thru from the bottom up
If I get my paws an another motor, what would be the best fit "drop in" replacement for a 351w? A 460 would be great if I find one, but a proper running 351 should provide me with enough power.
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