Installed 170 Header, Lost Power

[1strodeo]

Installed CI dual outlet header and Thrush Turbo mufflers with pipes out the sides, in front of rear tires. I had it on the highway, level ground, wide open and barely got to 65mph. Stock manifold and single pipe with 18" round muffler and I could get to 75 no problem.

Does this sound like a back pressure thing? Should I try an H pipe?

Got the sound I was looking for, but would be nice to at least have the power I had before!

...and NO I'm not installing a V8

 

[bmc69]

That's actually not uncommon. Opening up the exhaust a lot without changing the front end (intake) characteristics can lead to loss of power. Without a tailpipe O2 sniffer, we're just guessing, but I suspect that without a cam change and a different carb you are going to have a tough time recovering and, particularly, exceeding, the power from the original setup. But the carb is the first place to start...a larger main jet. Again though...I hate to guess at that; a wide-band O2 reader is your best friend for this kind of tuning.

 

[1strodeo]

Thanks guys, I'll just have to move forward with triple carb setup!

 

[jckkys]

I saw the same phenomenon with 300 I6s in the huge fleet UPS owned. They tried an experiment with Borla stainless headers, mufflers, and pipes. All they got was more noise. Power and MPGs went down. Single exhaust is better for I6s. The intake is integral with the head. It's a single casting. To get a better intake, get an Australian head first. The best carburetor swap for your engine is a small 2100. The best of these have 1.02 venturis or smaller. They were off 260 V8s and likely too big for 170, 200, or 250 I6s, those that did this swap are happy.

 

[Digger556]

Could be a couple of things. Larger exhaust may not generate the same velocities as stock and you get less scavenging in the cylinder, which in turn changes the power curve.

Or (what IMO is more likely) you have a more free-flowing exhaust and have increased the Volumetric Efficiency of the engine and therefore it is running leaner and making less power. Try going up a jet size in the carb and see if you get power back.

 

[bmbm]

bigger carb

One option that may help is to get a carb from a 200, the autolite with 185 cfm.
The head on the 170 has a smaller intake log and valves than later 200 and 250 heads.

 

[hillbilly1089]

I put a split header on my 170. It has 2-1/4 pipe running back and turned out behind the rear wheels. Could not fit the dual in and out muffler with internal cross over, so it has a stainless dual in and out resonator from a Corvette. It will run 85 mph on the highway if I feel like it.

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[1strodeo]

I put a split header on my 170. It has 2-1/4 pipe running back and turned out behind the rear wheels. Could not fit the dual in and out muffler with internal cross over, so it has a stainless dual in and out resonator from a Corvette. It will run 85 mph on the highway if I feel like it.

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So you're running dual pipes to a dual inlet-single outlet resonator with no muffler? I've never really understood what the resonators were for

 

[hillbilly1089]

The resonator is dual out. Both exit the passenger side. It sounds good, but is loud.

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[broncnaz]

So you're running dual pipes to a dual inlet-single outlet resonator with no muffler? I've never really understood what the resonators were for

Resonators are mainly to produce a certain sound.

Back to the original question. As others said your most likely to lean and more likely you'll have to go up a few jet sizes. while back in the 60's the carb may have been on the rich side and mods like exhaust may have worked todays gas is leaner by 10-20% which compounds the problem off the bat.
You may also need to adjust the timing as modifications can affect the need for more or less timing as well. Most modifications are not just a bolt on and instant power increase. Usually its a snowball effect you have to tweak or modify other systems to see full benefit.

While I'm sure Ford teams of engineers are pretty smart that doesn't mean they designed for the best performance. They were given parameters and that's what they engineered to. Remember they were designing for production vehicles that are mass produced and needed to be done cost effectively. Nowadays I think they do a lot better job in the performance side but some of the pieces and parts that go on todays engines kinda makes me scratch my head like you couldn't design this so I don't have to take half the engine apart to get to the one bolt you decided needed to go on from underneath the intake?

 

[1strodeo]

Most modifications are not just a bolt on and instant power increase.

Side note: Over decades I can't remember how many friends think certain things will happen "if only I do this". I learned a long time ago that I'm not smarter than a team of Ford engineers, regardless of what year. That is why I leave my stuff stock.
And, I dig sixes.

As I stated before I was looking for a sound, not a boost in power, but I certainly didn't expect to lose power. Prime example of the benefit of one change at a time!

Next up...triple carb setup.

What should I set the timing at?

Thanks again,
Jeff

 

[blubuckaroo]

Anytime you replace manifolds with headers, you need to check your jet size. That goes for sixes and eight cylinders alike.
Like bmc69 said, a wide band 02 sensor is the correct tool for this, or you could use the old-school method of reading the spark plugs.

 

[ledslinger29]

Did you have any trouble installing the CI headers? I'm in the middle of a mild build, have the stock 1100 carb right now with loadimatic. Put a Schneider 248/256 cam in, oversized valves, and had the head milled down .020. I'm thinking about headers, but have fitment concerns. Either way I'm gonna finish the build and get it running before I switch. I'm watching your thread on fordsix as well


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[1strodeo]

Anytime you replace manifolds with headers, you need to check your jet size. That goes for sixes and eight cylinders alike.
Like bmc69 said, a wide band 02 sensor is the correct tool for this, or you could use the old-school method of reading the spark plugs.

Yes I can tell the plugs are getting fouled without even pulling them, due to a distinct smell as well as performance, but i don't think theres a change i can make with the current carb to make a difference

Did you have any trouble installing the CI headers? I'm in the middle of a mild build, have the stock 1100 carb right now with loadimatic. Put a Schneider 248/256 cam in, oversized valves, and had the head milled down .020. I'm thinking about headers, but have fitment concerns. Either way I'm gonna finish the build and get it running before I switch. I'm watching your thread on fordsix as well


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the CI headers flanges are turned at different angles; basically the front flange is vertical mount, the rear flange is horizontal mount...if they were both vertical I think it may be ok, but because the rear flange is horizontal the 3 tubes need to be bent toward the block to clear the Bronco frame. If the header flanges were free floating like all other headers Ive had, there would be no problem. All the headers I've ever had you could turn the flange on both the header and the adjoining exhaust pipe as needed but these flanges are welded in place. The only way I found to bend the header pipes inward toward the engine was to mount them on the engine and use the old trac bar to pry them off the frame. An iron bar (like a trac bar) is needed because of the cushion of the motor mounts

Also I had to flip the alternator bracket upside down so the alt would be lower to clear the header.

 

[blubuckaroo]

Yes I can tell the plugs are getting fouled without even pulling them, due to a distinct smell as well as performance, but i don't think theres a change i can make with the current carb to make a difference

The addition of a good set of headers will usually make the engine run lean. Re-jetting the carb is usually needed.
A lean condition can smell the same as a rich condition.

 

[ledslinger29]

I'm sure you've got better things to do, but if you get bored I'd love to see a couple pics of how its all situated now.

 

[1strodeo]

The addition of a good set of headers will usually make the engine run lean. Re-jetting the carb is usually needed.
A lean condition can smell the same as a rich condition.

Im already into the Holley 1940 rebuilds, but interested to know what exactly is involved with re-jetting a carb? The smell is similar to a diesel exhaust smell??

Ill take some pics today ledslinger

 

[1strodeo]

Here are pics of each plug...thoughts? How does oil get on the threads, does that indicate a bad oil ring?

 

[1strodeo]

header pics

ledslinger, per your request, lower alt bracket I flipped upside down to lower the alternator, but it tightens the stock belt so there's no play there...had to 'massage' the number one tube a bit to clear the alt, but did it before realizing I could flip the bracket so may or may not be necessary. Also oil dipstick is a bit of an issue, I bent the bracket that attaches it to the block so now the dipstick is basically pointing to about 2:00 rather than 12:30ish.

 

[rmk57]

From what Iv'e read good plug readings are hit and miss with these engines due to the intake manifold being such a piss poor design. The end cylinder(s) tend to run lean on them. Plugs look ok. Knock the deposits off them and reinstall. As someone said go up a couple jet sizes and see how it runs.