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95 5.8L XLT, Hedman Shorties/MF SS Y & Muff, E4OD, Manual hubs, KYB Quads, 31x10.5x15's, 301K miles
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I see that your cam is designed for 2600rpms to 6300rpms = mid to high rpm cam, kind of out of the normal truck range and tow range which would be around 1000/1500 to 5000/5500 range = low to mid plus range. So waddabout your Torque converter stall speed and Gear ratio? I see your tires are 33"ers. What heads do you have on there?
 

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1980; 347 stroker; Holley Sniper EFI
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Discussion Starter #22
I see that your cam is designed for 2600rpms to 6300rpms = mid to high rpm cam, kind of out of the normal truck range and tow range which would be around 1000/1500 to 5000/5500 range = low to mid plus range. So waddabout your Torque converter stall speed and Gear ratio? I see your tires are 33"ers. What heads do you have on there?
Torque converter is this one. I don't know the gear ratio - I am not sure how I can even find that out without taking the front part off the diff and counting the gears? All I know its a Ford 9", next time I'm under I will see if there is some sort of serial number or tag.

Also don't know the head specs. I think its the stock 302 head but don't know for sure.
 

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95 5.8L XLT, Hedman Shorties/MF SS Y & Muff, E4OD, Manual hubs, KYB Quads, 31x10.5x15's, 301K miles
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So your TC starts moving the vehicle at approx. 1400 rpms and locks up at 2000 rpms, that leaves approx. 600 rpm before the cam starts coming on. You need to have all the components of your engine matched to work together in a certain Rpm range or the engine will not feel like it is up to the job. Your Cam, heads, intake manifold, Carb or Throttle body all have to be matched to operate in the desired RPM band to produce the intended results, in this situation the heads if stock are not matched to the cam and the TC is not matched either, you don't know your rear-end ratio so we don't know how that works with the rest. These are heavy vehicles and NEED Torque to get moving in the LOWER rpm range and your cam is not going to work without a looser TC. The rumble in you videos is the mufflers when you accelerate by putting a load on the engine, you will not hear that rumble in neutral/park just revving the engine. The greater the load on the engine the loader the rumble/noise from the mufflers/exhaust system will be. If you remove the valve covers and start up the engine you will get oil squirting all over the place but is you are checking the rockers, lifters and pushrods that's the only way to get to them to check but you don't have to start the engine you can just turn the engine with a big wrench to be able to check each lifter, rocker and pushrod.
 

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85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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I cant quite tell from my phone speakers.

That is a very healthy cam.

I also see you are running a sniper EFI, and it appears your IAC reading is not correct, judging by the red box around it.

@AbandonedBronco is running a sniper too, maybe he can clue us in on that.
 

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1980; 347 stroker; Holley Sniper EFI
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Discussion Starter #25
I cant quite tell from my phone speakers.

That is a very healthy cam.

I also see you are running a sniper EFI, and it appears your IAC reading is not correct, judging by the red box around it.

@AbandonedBronco is running a sniper too, maybe he can clue us in on that.
The red /yellow warning lights can be programmed to whatever value you like, but I am in fact having idle issues. Lately its been wanting to stall and red lights and it seems the IAC isn't always keeping up. I replaced it recently and it helped for a while but its back to acting strange. Not sure if @AbandonedBronco will have some idea - posted on the sniper forum but didnt get any response
 

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95 5.8L XLT, Hedman Shorties/MF SS Y & Muff, E4OD, Manual hubs, KYB Quads, 31x10.5x15's, 301K miles
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Here is what Comp Cams says about your Cam:

XFI Computer Controlled 236/248 Hydraulic Roller Cam for Ford 351W
HYDRAULIC ROLLER-347” or larger. Super strong mid-range. Best w/ 9.5 to 1+ compression aftermarket heads, intake, T-body & injectors. 3000+ stall or 5 speed. Computer modifications a must.
SKU
35-775-8

They are recommending a 3000+ stall converter vs your 2000 stall converter. Also Aftermarket heads vs your Maybe stock heads. super strong mid-range vs you wanting to tow and pull away from a red light/ stop sign where you need strong bottom-end. Still need to know rear-end gearing to know how good or bad that adds or hinders things.
 

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78 Custom 351M NP435 NP205 Sniper EFI Hedman Headers Magnaflow Muffler 4.56 Gears Grizzly lockers
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Going back to your original complaint, was everything running fine before your long trip? I mean, would it go up on ramps just fine before you noticed all of this?

I don't know about the cat placements as I don't have a Bronco with cats, but the double y-pipe deal and that super tight 90* bend behind the t-case going into the driver side muffler are the only things I'd change. How they are changed is personal preference, but those are the only dislikes I have on the exhaust system from just looking at the pics.

I've had a Sniper for about a year and a half or so. I recently swapped engines and put it on the new engine. As far as the idle goes, once you have your timing set, bring the engine up to temp and then adjust the iac with the screw on the linkage. When I swapped engines I didn't readjust the iac right away and I had a problem with low idle because of it. The engine would actually die immediately after a hot start just because the throttle blades were closed too much for the new engine's liking and the iac was the only thing keeping it going and it didn't have enough time on its own to fully open before the engine would stall.

If everything is set properly at idle and you're having problems with the idle dropping too much when you come to a stop, you can adjust the idle decay or whatever Holley calls it in the handheld. When you let off the pedal the rpm drops to whatever set point you put in and then it "decays" from there over a set amount of seconds until it gets back to your set idle rpm. For example, say you have it set to start decaying at 1,000 down to your idle of 700 over 3 seconds. You let off the pedal, the rpm drops, once it hits 1,000 is slows down and drops to 700 over those 3 seconds. Anyway, you can play with those settings and see if it helps if you have problems with your idle bottoming out when you let off the pedal.
 

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1980; 347 stroker; Holley Sniper EFI
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Discussion Starter #28
Going back to your original complaint, was everything running fine before your long trip? I mean, would it go up on ramps just fine before you noticed all of this?

I don't know about the cat placements as I don't have a Bronco with cats, but the double y-pipe deal and that super tight 90* bend behind the t-case going into the driver side muffler are the only things I'd change. How they are changed is personal preference, but those are the only dislikes I have on the exhaust system from just looking at the pics.

I've had a Sniper for about a year and a half or so. I recently swapped engines and put it on the new engine. As far as the idle goes, once you have your timing set, bring the engine up to temp and then adjust the iac with the screw on the linkage. When I swapped engines I didn't readjust the iac right away and I had a problem with low idle because of it. The engine would actually die immediately after a hot start just because the throttle blades were closed too much for the new engine's liking and the iac was the only thing keeping it going and it didn't have enough time on its own to fully open before the engine would stall.

If everything is set properly at idle and you're having problems with the idle dropping too much when you come to a stop, you can adjust the idle decay or whatever Holley calls it in the handheld. When you let off the pedal the rpm drops to whatever set point you put in and then it "decays" from there over a set amount of seconds until it gets back to your set idle rpm. For example, say you have it set to start decaying at 1,000 down to your idle of 700 over 3 seconds. You let off the pedal, the rpm drops, once it hits 1,000 is slows down and drops to 700 over those 3 seconds. Anyway, you can play with those settings and see if it helps if you have problems with your idle bottoming out when you let off the pedal.
The acceleration was fine before the trip, something definitely happened. I might not have the optimal set up / combination of components but thats not what I am trying to figure out. There is definitely a louder sound and a loss in acceleration compared to before the weekend.

The other IAC issue I've been having is it doesn't always ramp up and back down when I start it. Sometimes it does, sometimes it doesn't, not sure if thats normal. I replaced the IAC motor and it was working way better until recently. I have tried playing with the decay rate but it doesnt seem to change much so I recently went back to the default settings.
 

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Another thing besides a Cat problem is the internals in the mufflers or a muffler came apart and are blocking the flow thru the/a muffler(s). Test the engine vacuum with a vacuum gauge and see what happens with the readings under certain conditions, this will give you a good idea of what is happening in the engine and the exhaust.
 

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Discussion Starter #30
Another thing besides a Cat problem is the internals in the mufflers or a muffler came apart and are blocking the flow thru the/a muffler(s). Test the engine vacuum with a vacuum gauge and see what happens with the readings under certain conditions, this will give you a good idea of what is happening in the engine and the exhaust.
I don't have a vacuum gauge but I may look into getting one.

Not sure how to interpret this information, but in the videos you can see the manifold air pressure in kPA. Its the number on the left, second from the bottom. In the accelerating video, the number doesn't change all that much, it stays around 100 kPa (29.5 inHg). In the video where I'm parked, the manifold pressure drops a lot more to about 45 kPa (13.2 inHg). Not sure what that would indicate?
 

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95 Bronco, 351W, E4OD, 4.56 gears, 35x12.50x15 Patagonia MTs.
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I would check compression and or check each exhaust runner temp during warmup to look for a weak cylinder. Vacuum gauge also can indicate issues, but since you already have an aggressive cam, any comparison on vacuum is going to be moot. Assuming the engine is fully warmed up, did your vacuum at idle change before vs after the noise appeared?
 

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95 Bronco, 351W, E4OD, 4.56 gears, 35x12.50x15 Patagonia MTs.
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Psst, I can see an exhaust leak by your HVAC box in your engine video. That won't cause a power loss though.
 

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The first thought that comes to mind with the Sniper and an exhaust leak is that they're EXTREMELY temperamental to exhaust leaks. If you have a leak upstream from the O2 sensor, extra oxygen will slip in and hit the O2 making it think it's lean. It'll then dump in more fuel to get it right.
This will make the O2 sensor reading look good on the handheld, and the computer will think it's good, but in reality it's rich. A rich mixture will make it doggy and lack power.

Have you pulled your spark plugs and taken a look at them? How do they look?


Also, take some data logs of a drive and acceleration with the Sniper. Those can tell you a whole lot more than just the little viewscreen.
 

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As for the Holley Sniper EFI forum.... I don't get much traction over there and eventually gave up. There's one guy who answers everything, and if he doesn't answer, almost no one else does.

Check out the Facebook group. It's MUCH more active:

 

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1980; 347 stroker; Holley Sniper EFI
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Discussion Starter #35
I would check compression and or check each exhaust runner temp during warmup to look for a weak cylinder. Vacuum gauge also can indicate issues, but since you already have an aggressive cam, any comparison on vacuum is going to be moot. Assuming the engine is fully warmed up, did your vacuum at idle change before vs after the noise appeared?
I will get a compression gauge and report back. Can't do it today, because its Canada Day up here (our 4th of July) and everything is closed.I might also get a vacuum gauge, but the Sniper has a MAP sensor in kPA, is that not the same thing?

Psst, I can see an exhaust leak by your HVAC box in your engine video. That won't cause a power loss though.
How can you see the vacuum leak? and the HVAC box is the area circled? I have watched that video a several times and I dont see what you see
162551
 

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kPa and vacuum are close, but not quite the same thing.

kPa is absolute. Meaning you'll get the same reading at any elevation.
When I turn my engine off, my atmospheric here is about 95kPa. When I'm up at 9000 feet, it's about 75. (This is the reading the MAP says when the engine is off).

Vacuum is based off of ambient pressure. So, it's always 0 for atmospheric pressure. It'll be 0 at sea level and it'll be 0 at 9000 feet.

So they behave a little differently.


In your engine bay video, I thought I saw a puff of exhaust on the passenger side of the engine when you revved it.
 
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Discussion Starter #37
In your engine bay video, I thought I saw a puff of exhaust on the passenger side of the engine when you revved it.
Yes I have noticed that before as well, it looks like its coming out of either somewhere on the exhaust manifold or out of the spark plug socket if that makes any sense? I will try and look into that more, if it happens again I will get a better video
 

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1980; 347 stroker; Holley Sniper EFI
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Discussion Starter #38
I will get a compression gauge and report back. Can't do it today, because its Canada Day up here (our 4th of July) and everything is closed.I might also get a vacuum gauge, but the Sniper has a MAP sensor in kPA, is that not the same thing?


How can you see the vacuum leak? and the HVAC box is the area circled? I have watched that video a several times and I dont see what you see
View attachment 162551
@twofortyz Sorry, just re-read that, you said exhaust leak, not vacuum leak. My bad! yes I see that too, I will look into further
 

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If you think it might be coming from a sparkplug then check all the plugs and especially that particular plug for being tight in the hole, it is not that uncommon for a sparkplug to loosen up in the threads and let compression escape and a loss of power results and also noise from the escaping gasses. If you think your headers are leaking then also check all the bolts for tightness. If it is still leaking out the headers then a new set of header gaskets are in store, just get a GOOD pair. Hopefully it won't be from a crack in the headers. All this is basic maintenance on a Bronco. While you are checking you sparkplugs for tightness check to make sure 1 or more plug wires are not shorting to your headers because of heat and being to close to the header or on the header. Just another though for power loss under load
 

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Sounds like an exhaust leak to me.
might be a blown exhaust manifold gasket.
have you tried looking for it and night?
sometimes you can see it flashing in the dark
Look for a black or gray soot mark where it might be leaking
Can you narrow it down to driver or passenger side?
is that an edlbrock intake with egr port?
Those can make noise at the carb gasket
 
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