Wondering about exhaust systems

[Pebcak]

I like dual exhausts and plan to have them on both of my trucks. And I'll use Magnaflow mufflers on both of them as well.

But I don't have any pro tips. My plan is to take my trucks to a pro somewhere and have systems custom made for them.

I second Gary's motion.

That's what I did. Went to a local rep and had them make a custom dual setup with Magnaflow's. Here it cost me about $450 all together. Sounds great though.

Best example I can give is a little quieter than a Dodge exhaust rumble.

[Gary Lewis]

I second Gary's motion.

That's what I did. Went to a local rep and had them make a custom dual setup with Magnaflow's. Here it cost me about $450 all together. Sounds great though.

Best example I can give is a little quieter than a Dodge exhaust rumble.

Don - Will I get to hear it in a month?

[LARIAT 85]

...works so poorly it ends up in the junkyard soon after?

I'm not saying it's what would happen if you put duals on yours. I'm saying it's what I surmise from what I've observed over the past 30 years. You're entitled to interpret your observations YOUR way, but I'm only going to post MY observations & opinions.

My vehicles have always run great with factory or direct-replacement exhaust, and they run that way substantially longer than everyone I've encountered IRL & online who installs modified exhaust systems.

Most people who have an older carbureted engine and installs headers and/or dual exhaust usually don't leave the engine stock. THAT is usually the problem, and that is probably why you see so many in the junkyards.

Many older vehicles I have seen with headers and dual exhaust - even at car shows - have modified and poorly thought out engines bolted to them. To begin with, it is often necessary to re-tune the carburetor when headers and/or dual exhaust is added. If you don't so that, there is a good chance the engine will be too lean as a result and it will see the junkyard quicker.

The stock thermostatic air cleaner often goes missing because it is "smog junk" and so the engine never has the correct fuel mixture. Chokes are removed because they were "not needed." The carburetor is typically oversized in the name of "more horsepower" and not tuned properly, often being way too rich. Single plane exhaust manifold on a street engine because that is what race cars use. Lumpy, racing style camshafts are installed because they "sound cool," which results in low engine vacuum and a very confused, out-of-balance carburetor that has been opened up too far in order to sustain an idle. Colorful, racing-style spark plug wires because they look "cooler," etc.

You know what I am talking about.

 

[85lebaront2]

That's great as long as you can get something that fits and works.

I think you CAN get direct-replacement exhaust components for bullnoses.

Manifolds are restrictive...

That's pretty vague & subjective. Ford designed the engine, and the manifolds. Who can say better than Ford what qualifies as "restrictive"? I know the original exhaust manifold on my I6 was not particularly breezy, but it had another function (preheating the charge air for cold weather). But the ones on the 4.9L are widely considered to be at least as good as (if not better than) any headers.

"...OEM manifolds are made of a different material than the heads, expand at a different rate and cause issues with bolt breakage as well and exhaust ear issues."

So is he claiming that every header available is made of the same material as Ford heads? Of course not, which means that statement is irrelevant.

But let's examine it...

The heads aren't actually "cast Iron" - they're steel. The coefficient of thermal expansion for every common type of steel (except stainless) is 6.5 E-6/°F. For the cast Iron manifolds, it's 6.7. Assuming they're assembled at 80°F, the head temperature will rise ~140°F as it reaches normal operating temperature, and the manifold might rise 1,000. So if the head & manifold are 20" long (on a V8 with four ~4" cylinders plus some extra between them & at each end), the head will grow (20x140x0.0000065)=0.0182", and the manifold will grow 0.134". So they'll move a total of 0.1158" relative to each other. Given that Ford puts a small bolt hole in an ear near the center of the manifold, and all others are oversized (meaning the manifold stays roughly centered on the head); that means that the manifold will creep ~0.0579" along the head at each end, when they're at operating temps. That's not quite 1/16" (0.0625"), which (big surprise) is about the difference in the manifold bolt diameter to the hole diameter.

https://supermotors.net/getfile/770511/thumbnail/12greaseman.jpg

https://supermotors.net/getfile/1143092/thumbnail/20181210_174534.jpg

You'd almost think Ford designed it to tolerate that temperature change!

Steve, please explain to someone who worked in a metallurgical laboratory what alloy steel cylinder heads are made from? All of them I have seen were cast iron, most gray iron (brittle) some might be nodular iron like some Ford 9" hogsheads, and some might be malleable iron. Maybe some Flatheads were steel.

[Steve83]

...what alloy steel cylinder heads are made from?

If you say they're cast Iron, then you must agree that bolting cast Iron manifolds to them won't cause any bolt or ear problems, right?

I have no idea what alloy Ford specified for blocks & heads, but I bet it was below 3.5% Carbon, which makes it steel in my mind. Can you get one tested & tell us for sure?

You know what I am talking about.

Yep - those modifications are as much symptoms as causes. But the result is the same: junkyard, in a hurry.

[ArdWrknTrk]

Most people who have an older carbureted engine and installs headers and/or dual exhaust usually don't leave the engine stock. THAT is usually the problem.

Many older vehicles I have seen with headers and dual exhaust - even at car shows - have modified and poorly thought out engines bolted to them.

Single plane exhaust manifold on a street engine because that is what race cars use.

Rick,

Maybe it's a single plane intake?

While I agree, most people don't have the knowledge (or restraint) to build a balanced performance engine.

They are also the useful idiots that keep most of these companies in business.

In some small way, we should be thankful for them.

 

[ArdWrknTrk]

...what alloy steel cylinder heads are made from?

If you say they're cast Iron, then you must agree that bolting cast Iron manifolds to them won't cause any bolt or ear problems, right?

I have no idea what alloy Ford specified for blocks & heads, but I bet it was below 3.5% Carbon, which makes it steel in my mind. Can you get one tested & tell us for sure?

You know what I am talking about.

Yep - those modifications are as much symptoms as causes. But the result is the same: junkyard, in a hurry.

High nickel and/or chrome blocks were used for quite a few engines.

Not just performance engines, but Marine and industrial applications where corrosion and wear protection were important.

As for the carbon content of heads, I'm not so sure.

We see plenty of nodular and other gray and white irons, that are way beyond eutetic, but not considered 'steel'

[85lebaront2]

...what alloy steel cylinder heads are made from?

If you say they're cast Iron, then you must agree that bolting cast Iron manifolds to them won't cause any bolt or ear problems, right?

I have no idea what alloy Ford specified for blocks & heads, but I bet it was below 3.5% Carbon, which makes it steel in my mind. Can you get one tested & tell us for sure?

You know what I am talking about.

Yep - those modifications are as much symptoms as causes. But the result is the same: junkyard, in a hurry.

Not any more, I am retired, the metallurgist I worked with for years is retired, the man who ran the spectographic analyzer retired and is now deceased from Alzheimers complications, even the head Chemist has retired. When I was still working in the lab is was at a major defense contractor and we did metals, paints, plastics, trace elements, just about anything you needed. One of our outside customers through our marketing division was Ford Motor Company, I have a pair of partially finished 460 EFI valve covers that we tested the for a gasket leak issue, this resulted in the deep groove HD valve cover design.

There are some high chrome, nickel, moly cast iron alloys that have very good wear resistance but can be a royal bitch to bore (Mercedes-Benz blocks) Chrysler used to use a hard iron block, which is why many of the old 318s will have loads of miles on them and still run well.

[Gary Lewis]

While I agree, most people don't have the knowledge (or restraint) to build a balanced performance engine.

They are also the useful idiots that keep most of these companies in business.

In some small way, we should be thankful for them.

Very true. I've come to the conclusion that it is wise to pay someone that knows the correct bits to put together for a given application. Someone like Tim or Scotty that lives and breathes a specific engine is invaluable.

I told Scotty what I want to use the engine for, that I have the F3 heads, will be running EEC-V and want to burn regular pump gas to tow and offroad with, but still get "good" MPG - for a 460. And with that he knew what pistons, deck height, cam, etc.

And, he strongly recommended headers.

[Steve83]

I've come to the conclusion that it is wise to pay someone that knows the correct bits to put together for a given application.

I agree totally, but the "someone" I trust is Ford.