Ford Fairmont carbed 5.3 swap, odd noise, need some other opinions
05-22-2012, 10:41 AM
#1
Ford Fairmont carbed 5.3 swap, odd noise, need some other opinions Here's the run down, I helped a friend swap his 78 Fairmont a few months ago and it's making a noise recently that we can't seem to trace exactly.
5.3 with a custom comp cam and a th400 with a 3600 rpm stall, cam duration in the mid 250's. Shortblock had 73k +/-, oil pressure is great, E85 HPI carb and MSD 6010.
In park and under hood, it'll free rev right up to 7k without an issue or a sound, the motor sounds great.
The noise is most noticeable when you put the car in third gear at cruising speeds and give it about a half throttle and the engine is loaded well. It sounds like an exhaust leak, I pulled the drivers side MLS header gasket and it looked kinda rough so I changed both sides. No change in the noise. I doubled checked all exhaust connections and nothing is leaking. Converter bolts are tight, nothing is rubbing anywhere that I can see.
It follows RPM. I stood on the roadside and got him to duplicate the sound and I don't have a clue how to describe the sound, it's a lot quieter than when you're in the car and sounds different than what I hear while inside the car, I've never heard such a thing.
My next attempt is going to be changing out the coil packs. It's pretty slim odds, but is it possible that one of the coil packs is arcing and creating that noise?
I inspected a couple on that side real quick last night before I went home and couldn't see any cracks are carbon marks on the two I looked at or the areas where they're near.
It's only making the noise at certain RPM's and the motor has to be under a good load and the car does not have a miss at all, runs great all the way from idle to 7k RPM's when you stand on it.
Anyone have any coil pack experience as far as noises or seen anything like this? I'm baffled by this one so far.
Thanks in advance guys!
5.3 with a custom comp cam and a th400 with a 3600 rpm stall, cam duration in the mid 250's. Shortblock had 73k +/-, oil pressure is great, E85 HPI carb and MSD 6010.
In park and under hood, it'll free rev right up to 7k without an issue or a sound, the motor sounds great.
The noise is most noticeable when you put the car in third gear at cruising speeds and give it about a half throttle and the engine is loaded well. It sounds like an exhaust leak, I pulled the drivers side MLS header gasket and it looked kinda rough so I changed both sides. No change in the noise. I doubled checked all exhaust connections and nothing is leaking. Converter bolts are tight, nothing is rubbing anywhere that I can see.
It follows RPM. I stood on the roadside and got him to duplicate the sound and I don't have a clue how to describe the sound, it's a lot quieter than when you're in the car and sounds different than what I hear while inside the car, I've never heard such a thing.
My next attempt is going to be changing out the coil packs. It's pretty slim odds, but is it possible that one of the coil packs is arcing and creating that noise?
I inspected a couple on that side real quick last night before I went home and couldn't see any cracks are carbon marks on the two I looked at or the areas where they're near.
It's only making the noise at certain RPM's and the motor has to be under a good load and the car does not have a miss at all, runs great all the way from idle to 7k RPM's when you stand on it.
Anyone have any coil pack experience as far as noises or seen anything like this? I'm baffled by this one so far.
Thanks in advance guys!
Last edited by RATBOX; 05-22-2012 at 04:13 PM.
05-22-2012, 02:00 PM
#4
If you can't even describe the sound then how do you expect people to diagnosis it over the internet?
My mom had a Ford Fairmount. the whole dash was loose and rattle so badly that I don't know how you could possibly hear engine noises.
My mom had a Ford Fairmount. the whole dash was loose and rattle so badly that I don't know how you could possibly hear engine noises.
05-22-2012, 02:03 PM
#5
Do you have a scanner and monitoring the Knock count as well as the Fuel trim and Load when this happens..?
This kind of problem and asking for help is not an easy one for anyone 2-3k mile away to help. Way to many Variables and issue to debug.
Byt what kind of sound is it making.? Also it might or would sound different to someone else. Internal noise problems can be transmitted throughout the engine/trans and sound like it is originating from somewhere else.
But as SS409 said, if it is only under a load.. back to the Knock counts, is Timing being taken out, Misfires, etc, check or monitor, try a capture and have someone look at it.
Could be in your tune.. and that is way to hard to debug from here without data..(not that I would be able to, but a good tuner might).
Good Luck....
BC
This kind of problem and asking for help is not an easy one for anyone 2-3k mile away to help. Way to many Variables and issue to debug.
Byt what kind of sound is it making.? Also it might or would sound different to someone else. Internal noise problems can be transmitted throughout the engine/trans and sound like it is originating from somewhere else.
But as SS409 said, if it is only under a load.. back to the Knock counts, is Timing being taken out, Misfires, etc, check or monitor, try a capture and have someone look at it.
Could be in your tune.. and that is way to hard to debug from here without data..(not that I would be able to, but a good tuner might).
Good Luck....
BC
05-22-2012, 04:04 PM
#7
Do you have a scanner and monitoring the Knock count as well as the Fuel trim and Load when this happens..?
This kind of problem and asking for help is not an easy one for anyone 2-3k mile away to help. Way to many Variables and issue to debug.
Byt what kind of sound is it making.? Also it might or would sound different to someone else. Internal noise problems can be transmitted throughout the engine/trans and sound like it is originating from somewhere else.
But as SS409 said, if it is only under a load.. back to the Knock counts, is Timing being taken out, Misfires, etc, check or monitor, try a capture and have someone look at it.
Could be in your tune.. and that is way to hard to debug from here without data..(not that I would be able to, but a good tuner might).
Good Luck....
BC
This kind of problem and asking for help is not an easy one for anyone 2-3k mile away to help. Way to many Variables and issue to debug.
Byt what kind of sound is it making.? Also it might or would sound different to someone else. Internal noise problems can be transmitted throughout the engine/trans and sound like it is originating from somewhere else.
But as SS409 said, if it is only under a load.. back to the Knock counts, is Timing being taken out, Misfires, etc, check or monitor, try a capture and have someone look at it.
Could be in your tune.. and that is way to hard to debug from here without data..(not that I would be able to, but a good tuner might).
Good Luck....
BC
Mostly what my question was pertaining to was whether or not anyone had experienced a coil pack arc under certain conditions and if it made enough noise to hear it while driving.
Thanks again for the input!
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06-11-2012, 09:07 AM
#8
Little follow up, noise was a reeeeally small crack in the header primary where they come together at the collector. Couldn't see it with the header on the car, decided to pull the header off on a vague hunch and saw a tiny carbon trail. I welded it and voila, noise gone. No idea how it cracked, the headers were used prior to this but not for many miles so I dunno. One of those flukes you see now and again I guess.
06-11-2012, 02:36 PM
#10
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Little follow up, noise was a reeeeally small crack in the header primary where they come together at the collector. Couldn't see it with the header on the car, decided to pull the header off on a vague hunch and saw a tiny carbon trail. I welded it and voila, noise gone. No idea how it cracked, the headers were used prior to this but not for many miles so I dunno. One of those flukes you see now and again I guess.
06-11-2012, 06:30 PM
#11
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That was an nasty noise you had if it sounded anything like mine. My stainless 2.5 band clamps let the smallest exhaust leak out and it sounded almost like something skuffing in the bottom end . Glad you found it . I have now welded everything from the front to the back in the exhaust . If i could get in to my exhaust flanges i would if they make a peep.
