74 351w engine peck when under pressure
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From: corbin ky
74 351w engine peck when under pressure
have a 351w that pecks when under pressure, i have checked all pushrods and lifters, all valves appear to be correct (havent pulled the head to see). along with the peck i am running rich on the same bank, also have a vacuum leak (same bank) that as far as i can tell is a exhaust manifold leaking though it too only does it when i give it some throttle. my question is this; is my peck due to the exhaust manifold leak under pressure or is this something else entirely?
also note that the exhaust leak wasnt discovered until after i had checked all the lifters, rockers, and pushrods.
also note that the exhaust leak wasnt discovered until after i had checked all the lifters, rockers, and pushrods.
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This "peck" that you speal of, is this a "ping" from detonation? How is the timing?
This can be caused by a real vacuum leak, but not my an exhaust leak.
Intake is vacuum, exhaust is exhaust. The exhaust has no vacuum, it has pressure.
Now, a bad exhaust gasket can allow the leak and will make a heak of a noise. This can actually sound like metal on metal, or a real loud tap.
Fix the exhaust leak since you know this is already a problem, and then isolate your problem from there.
Start with the known problem so you can eliminate it.
This can be caused by a real vacuum leak, but not my an exhaust leak.
Intake is vacuum, exhaust is exhaust. The exhaust has no vacuum, it has pressure.
Now, a bad exhaust gasket can allow the leak and will make a heak of a noise. This can actually sound like metal on metal, or a real loud tap.
Fix the exhaust leak since you know this is already a problem, and then isolate your problem from there.
Start with the known problem so you can eliminate it.
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From: corbin ky
i fixed one leak on it already, and didnt isolate the exhaust leak until i went through all of my lifters. it does sound alittle like a metal on metal tap, but only occurs when the motor is under pressure. i can sit and rev it all day and wont get the slightest sound. and only get the sound from the side with the exhaust leak, which is why i asked if the exhaust manifold leak could cause this. i dont think that timing could cause me to only have a peck on one side though i could be wrong?.
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From: corbin ky
UPDATE: have fixed exhaust gasket leaks so i can now hear the noise through its entire range. (dont have a tach so these are guesses on rpms) once cruising at around 3k in 4th (top gear), the noise goes away, there is no loss of power, stutter,stall or anything else just an annoying peck when under load, no noise at peck, or at cruising only when getting up to speed. correct me if im wrong but could this be a weak valve spring, or lifter failing/failed?
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From: corbin ky
what could cause this? a cracked spark plug or what? truck starts with no problems at all revs with no prob, has just about to much torque to handle on a wet road, but this peck is driving me absolutely nuts. thx i no it aint much info on it but its hard to find it when you gotta be driving to get the peck
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try running high octane fuel in it... i know it sounds crazy but i've seen it a couple of times... person runs one on 93 octane then switches back to 87 and the engine developed a gas ping
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From: corbin ky
if it was removed then it happened in the middle of the night while i was asleep. it is a recent development that didnt show up until about 100 miles after i had to replace the coil, pickup, and ignition module. it isnt getting any louder or changing at all, and i have tried changing the octane of fuel that i was running, but that didnt help, also started getting gas elsewhere but that didnt help either.
one thing though. my exhaust gasket was leaking just over my starter causing it to want to heat sink a little, could this excessive heat damage a spark plug??
i didnt think of the spark plugs b4 because they are all new, with new wires, and they were replaced b4 the ignition module, pickup and coil.
one thing though. my exhaust gasket was leaking just over my starter causing it to want to heat sink a little, could this excessive heat damage a spark plug??
i didnt think of the spark plugs b4 because they are all new, with new wires, and they were replaced b4 the ignition module, pickup and coil.
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ok since its only running rich on one side ... i would say that rools out the carb.. i would check the distibitor cap for cracks, check the plug wires for damage, check the sparkplug gap... it may just be in need of a tune up. as far as timing, vaccum leaks, carb out of adjustment, they should all effect the whole engine not just one side
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From: corbin ky
yeah thats what has been making me go ape sh** with this thing. gonna check all the wiring, and plugs out in the morning, maybe i will notice something this time that i have missed before.
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From: DeKalb, Ill.
How sure are you that the sound is only coming from one side?
I'm only asking because I've been through this,
trying to diagnose a sound that only occurs going down the road under a load.
I called my problem "ignition ping" for a long time,
misleading all of these helpful guys on the forum all along.
I didn't get to the bottom of my noise until I took the right old codger for a ride.
Long story short, try to be sure that you know what you're hearing.
These guys can help you solve any problem as long as you
give them an accurate diagnosis/description.
My advice, take an old fart for a ride.
Someone who has "been there done that".
Get an experienced set of ears on your side.
Murph.
I'm only asking because I've been through this,
trying to diagnose a sound that only occurs going down the road under a load.
I called my problem "ignition ping" for a long time,
misleading all of these helpful guys on the forum all along.
I didn't get to the bottom of my noise until I took the right old codger for a ride.
Long story short, try to be sure that you know what you're hearing.
These guys can help you solve any problem as long as you
give them an accurate diagnosis/description.
My advice, take an old fart for a ride.
Someone who has "been there done that".
Get an experienced set of ears on your side.
Murph.
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From: corbin ky
murph77: i have taken a old codger for a ride, quite a few of them in fact, i piled 2 experienced sets of ears in the cab with me and took them for a spin. we didnt make it 10 feet b4 they both pointed toward the 1-4 cylinder bank and said thats where your noise is.
daddy172005: it sounds the same when i get down on it as it does when i granny it. tried adjusting my timing atlittle in both directions but there was no change in the sound at all. which is why i beleive that this is something non timing/fuel related.
daddy172005: it sounds the same when i get down on it as it does when i granny it. tried adjusting my timing atlittle in both directions but there was no change in the sound at all. which is why i beleive that this is something non timing/fuel related.