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  #61 (permalink)  
Old 01-16-2009, 08:19 PM
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Nice items! I am running a set of Fenton split cast iron headers on my tricked out 335 6 in my '53 Chevy pickup. You can sort of see them in these pics.


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Last edited by willys36@aol.com; 01-16-2009 at 08:28 PM.
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  #62 (permalink)  
Old 01-16-2009, 08:39 PM
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Quote:
Originally Posted by 65smallblock
From Vizzards book a few pieces of info I found rather interesting. Here he is talking about using Iron manifolds with some porting done to them;

"On engines in the 280-350 hp range, it was common to pick up at least 10 hp, with 15 being the norm, and on one occasion I saw as much as 22. I have to stress @ thins point that the porting done was only basic."

And oppisite of that page there is a graph titled "Headers vs stock manifolds" where he ran the same '81 camaro with both stock iron and headers, quote; "This represents an increase of 16 HP and 22 ft lbs of torque".

Nearly identical results as the above comparison with just porting!

In another place he clearly states that Profesionaly worked cast manifolds produced about 65% of the gains possible by using typical race headers on "the types of motors we're dealing with here".

"The types of motors we're dealing with" ...... I take that to mean the 400-500 hp engines that the book is geard toward. Soooo, If we read between the lines, one might conclude from this that a set of ported iron manifolds on something up to 350 hp would do extremly well, while higher horsepower engines exceeding 400 hp can expect a bit more gain from headers as opposed to ported iron.
Just a point of clarification; the '81 Camaro used in the "Headers vs. Stock Manifolds" comparo wasn't the same engine used in the work on the opposite page with the ported manifolds. So the results weren't nearly identical.

The '81 Camaro test simply compared the difference between headers and manifolds on a bone stock engine. Just headers alone, no other changes; restrictive stock exhaust with pellet-type catalytic converter and all. The Camaro dynoed at 213hp in stock configuration. The manifolds were tested on engines of higher output, between 280-350hp, or an average of 315hp. That's an average 100hp more than the stock Camaro engine. So while both saw a 15/16hp boost, that represents a proportionally smaller gain with the ported manifolds on the higher output engines. The higher output engines gained 4.8% with the ported manifolds; the Camaro 7.5% with headers. In other words, headers bettered the manifolds by just over a 50% margin.

When Vizard then replaced the restrictive stock catalytic converter with a higher flowing aftermarket cat, power increased by total of 27hp over stock to 240, or about a 13% increase in power output.

Also, the gain Brzezinski achieved in "the types of motors we're dealing with here" are with the same 280-350hp engines Vizard was testing. Remember, Brzezinski is selling cast iron parts to circle track racers who are restricted in the types of mods they can make. That'll be clear when you look at the dyno chart I linked to earlier. His modified manifolds and 2 into 1 collector was worth a maximum of 33hp at 5000rpm, increasing power from 287 to 320hp. Peak hp was increased from 303 hp at 5500rpm to 327hp.

Last edited by BinderDriver; 01-16-2009 at 08:47 PM.
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Old 01-17-2009, 04:51 AM
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Quote:
Originally Posted by BinderDriver
Just a point of clarification; the '81 Camaro used in the "Headers vs. Stock Manifolds" comparo wasn't the same engine used in the work on the opposite page with the ported manifolds. So the results weren't nearly identical.

The '81 Camaro test simply compared the difference between headers and manifolds on a bone stock engine. Just headers alone, no other changes; restrictive stock exhaust with pellet-type catalytic converter and all. The Camaro dynoed at 213hp in stock configuration. The manifolds were tested on engines of higher output, between 280-350hp, or an average of 315hp. That's an average 100hp more than the stock Camaro engine.

I was going on the assumption that the 280-350 hp motors used to test ported manifolds were measured @ the crank (as are most hp # quotes in the book) and that the #s given for the Camaro were from a chasis dyno (BHP) which would make them much closer than 100 hp apart. Otherwise that would be a very anemic Camaro..
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Old 01-17-2009, 05:30 AM
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Originally Posted by willys36@aol.com
[B]Nope, free flowing is a side benefit but a tuned header's claim to fame is the Helmholtz resonating effect. Otherwise, no need to care if the tubes are equal length or any particular length at all.

Hmm, Helmholtz huh, Ill look it up. My understanding is that "exhaust system" tuning is VERY important whereas equal length headers are, well, overrated..

Sorry if I seemed snipey earlier. I guess I just felt a 2nd opinion was in order.

Nice truck..
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  #65 (permalink)  
Old 01-17-2009, 07:37 AM
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Binder,
LOL,,,
yup, this thread would have been alot shorter if ya had posted this page from your BREZ' link for 49Willys....

http://www.castheads.com/faqs_exhaust_manifolds.php
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  #66 (permalink)  
Old 01-17-2009, 09:07 AM
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Quote:
Originally Posted by 65smallblock
Hmm, Helmholtz huh, Ill look it up. My understanding is that "exhaust system" tuning is VERY important whereas equal length headers are, well, overrated..

Sorry if I seemed snipey earlier. I guess I just felt a 2nd opinion was in order.

Nice truck..
Here is a link to the progress on my truck. Only been working on it for about 6 years - no rush. I started the engine about 3 years ago, ran it for about a minute (had to idle it at about 5,000rpm to keep it running so it needs a little fine tuning) then stored it while we built a new house, totally landscraped my 1/2 acre back yard, helped my son build a '36 Pontiac 4-dr sedan (which he sold to get a down payment on a starter hone - that's what having kids will do!),




Incidentally, I designed those headers w organ pipe theory for 2000rpm. Split them to dual exausts. Straight 6s w/ duals sound funky!! And I designed and cast that aluminum dual plane intake manifold (had to isolate the Siamese intake ports in the head too) for the same 2000rpm, using a Holley 390. That 215cuin engine would climb a wall at cruising speed!!



dressed the inside of my new 1700sqft shop (wire for power, plumbing, drywall, fill with cabinets etc., etc.), put crown molding in our entire house, built my wife a sewing computer room with a Murphy bed and LOTS of cabinets, built my grand kids a 200 sqft, two story castle (built the metal fence, rock walls, & poured the cement curbs and slabs too),



and now I just started restoring a '59 El Camino with my 14 yr old grandson. The truck MAY be done B4 I get sent to Trembling Hills, but I doubt it. Just needs tuned, bed painted and installed and it would be on the road.

No offense taken. Get a copy of that book I referenced earlier. It will explain intake and exhaust tuning in great detail and is very readable. Even the mag articles I referenced shed a lot of light. There is a definite science to it with real live engineering equations and everything. As I also mentioned above, there are two commonly used sets of equations that come out to essentially the same answer. And it isn't a case of equal length headers being 'over rated' or 'under rated'. It is simple physics. A single pipe can be tuned to 'supercharge' a single cylinder at a single resonant frequency (rpm). If the tubes to different cylinders are different lengths, their resonant frequency will be different and each cylinder will achieve maximum boost at different rpm so the engine composed of those separate cylinders will likely have less peak power but have a broader torque curve. Lots of art goes along with a little science in designing these things.

One design method commonly used (the one I use) is the organ pipe theory which addresses the action of a sound wave traveling in an open ended conduit. This guy discusses the organ pipe theory and gives the pertinent equations as applied to intake systems on motorcycles. Same principles and equations apply to cars, exhausts, organs, you name it.

The other commonly used design theory is Helmholtz resonance which addresses an enclosed cavity which is charged with energy (gasses in our case) and acts like a spring, then the pressure (spring) is suddenly released and gas flows out displacing the small volume in the conduit which acts as a 'non-compressible solid' in the equations (good approximation) and this too can be tuned for a resonant frequency and maximum benefit at that single frequency (rpm). They use Helmholtz theory to scientifically tune guitars nowadays! The principle discovered in the 19th century by Hermann Ludwig Ferdinand von Helmholtz (August 31, 1821-September 8, 1894) but he applied it to electromagnetic radiation since he was studying optics and light (He is the Harley Earl or Zora Arkus Duntov of modern optics!). Works with any energy input (light, electricity, air, plasma, etc.) into an enclosed volume through an attached conduit. We happen to use a set of his equations that help design intake and exhaust manifolds.

Here is a page from the engineering web site of Florida State that gives a summary of the two theories as applied to intake and exhaust tuning. It is pretty abridged but is a pretty good narrative of what is going on. For some reason they don't list the organ pipe equations on that site.

Last edited by willys36@aol.com; 01-17-2009 at 09:14 AM.
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Old 01-17-2009, 01:06 PM
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Quote:
Originally Posted by 65smallblock
I was going on the assumption that the 280-350 hp motors used to test ported manifolds were measured @ the crank (as are most hp # quotes in the book) and that the #s given for the Camaro were from a chasis dyno (BHP) which would make them much closer than 100 hp apart. Otherwise that would be a very anemic Camaro..
Well, it's a stock '81 Camaro. Late '70s/early '80s smog motors weren't a bonanza of horsepower, even with the wonderful computer controlled Quadrajet. So, yeah, Camaros at that time were anemic. So was everything else. The '81 Z28 with the LG4 305 was rated at 165 SAE net hp; the '81 Z28 350 was rated at 175. I remember reading a road test at about that time and the author complained about being unable to pass a determined Toyota driver. I also remember a 17 second quarter mile. This is about the same time period when 'Vettes were 15 second cars.

Since that SAE net 175HP was measured at the flywheel with all accessories and a full exhaust, it'd take divine intervention for that Camaro to gain 40hp with the addition of the drivetrain and produce 213HP at the wheels, stock.

Since Vizard's stock HP figure was so much higher than the engine's rating, I was under the impression that it was measured on his engine dyno w/o accessories but with a full exhaust.
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Old 01-17-2009, 01:16 PM
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Willys36-


Ive gotta hand it to you, when you jump in you jump in with both feet.. I will just say that I personally feel that my time will be better spent focusing on other aspects of my ride as opposed to splitting hairs over header tube length. I know that there are benefits to be had there, but I feel that there comes a time where you get diminishing returns per the amount of effort put into it. If I were building a pro-stock car I might have a different disposition. But unfortunatley Im not..

I can certianly relate to not getting in a hurry. I had a dog run, landscaping, broken water main and fireplace improvments that set back my project hopes last summer.. Time is our most valuable asset.


Id like to know more about your I-6, looks like fun stuff. Is that an aluminum block?
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Old 01-17-2009, 01:35 PM
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Originally Posted by BinderDriver
Well, it's a stock '81 Camaro. Late '70s/early '80s smog motors weren't a bonanza of horsepower, even with the wonderful computer controlled Quadrajet. So, yeah, Camaros at that time were anemic. So was everything else. The '81 Z28 with the LG4 305 was rated at 165 SAE net hp; the '81 Z28 350 was rated at 175. I remember reading a road test at about that time and the author complained about being unable to pass a determined Toyota driver. I also remember a 17 second quarter mile. This is about the same time period when 'Vettes were 15 second cars.

Since that SAE net 175HP was measured at the flywheel with all accessories and a full exhaust, it'd take divine intervention for that Camaro to gain 40hp with the addition of the drivetrain and produce 213HP at the wheels, stock.

Since Vizard's stock HP figure was so much higher than the engine's rating, I was under the impression that it was measured on his engine dyno w/o accessories but with a full exhaust.

Your points are well taken. I wont get into the specifics of what hp the Camaro had da, da, da anymore than we already have, because the truth is that the book really doesnt specify. I think that weve both made our points.

One thing I do know is that Ive seen people unwittingly go out and break open their piggy bank and throw in their lunch money after reading and hearing about big horsepower gains from this part or that part without realizing that said part is only a small piece to a big puzzle. Then the results are often huge dissapointment from either no "seat of the pants" gains or maybe even worse performance. You know the people Im talking about.. Like the guy in another thread who went out and threw a BIG roller cam in an otherwise stock motor expecting to tear up the boulevard. Bottom line, what nets 20-30 horsepower gains for one motor is NOT nessecarily going to do the same for another. And for me personaly, if Im running a stock 350 (like said anemic Camaro) and I have a choice of upgrading a stock dual exhaust to headers or adding a good set of heads, Ill take the heads every time and smoke the guy who opted for the headers..

Last edited by 65smallblock; 01-17-2009 at 01:46 PM.
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Old 01-17-2009, 02:44 PM
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Quote:
Originally Posted by 65smallblock
One thing I do know is that Ive seen people unwittingly go out and break open their piggy bank and throw in their lunch money after reading and hearing about big horsepower gains from this part or that part without realizing that said part is only a small piece to a big puzzle. Then the results are often huge dissapointment from either no "seat of the pants" gains or maybe even worse performance. You know the people Im talking about.. Like the guy in another thread who went out and threw a BIG roller cam in an otherwise stock motor expecting to tear up the boulevard. Bottom line, what nets 20-30 horsepower gains for one motor is NOT nessecarily going to do the same for another. And for me personaly, if Im running a stock 350 (like said anemic Camaro) and I have a choice of upgrading a stock dual exhaust to headers or adding a good set of heads, Ill take the heads every time and smoke the guy who opted for the headers..
I couldn't agree more. Although, I have to admit I'm one of those guys who's made changes to my engines that have ended up not doing much, or reducing performance. But I always figured that was part of the learning process. Like Willys36 said, this is as much art as science. Sometimes you'll take a step backward before moving forward. Especially when, if you're like me, you do this for a hobby and will never develop enough independent experience on your own to call yourself an expert. I just won't build that many engines. I'm also not an engineer. But I can at least learn from those who are, figure out why the change didn't result in the gains I wanted, and do something about it. It's also good to know even the experts made the same mistakes before they were experts. I've always been happy with the results eventually, and as far as I'm concerned that's the only thing that counts.

I also agree that the cylinder head is the key component in building a top end that can satisfy the needs of the bottom end. But I think we can both agree that it makes little sense to improve an engine's ability to to pack a greater combustion charge into the cylinder and not pay equal attention to how you're going to get the left overs out of there, when money, space, & other considerations permit.

Which is why I joined in to help beat this dead horse. I agree you don't necessarily need headers if your engine is stock or close to it, and you're only using the vehicle for towing and looking cool. And some manifolds work better than others out of the box, and there are ways to improve them. But I just couldn't go so far as agree that headers aren't useful on a street vehicle, & that they only provide any kind of benefit at higher rpms. You have to look at the whole package
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Old 01-18-2009, 10:38 AM
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Quote:
Originally Posted by BinderDriver
But I just couldn't go so far as agree that headers aren't useful on a street vehicle, & that they only provide any kind of benefit at higher rpms. You have to look at the whole package

If I suggested that anywhere then I will consider myself corrected, but I dont think I did. All I was really trying to say is that they are more usefull after more power is achieved than basic stock applications.

Just a few thoughts Ive had re; this "dead horse"

1- Im thinking that the case of the camaro could well be an extreme case, IE; terrible exhaust system to match the rest of the smog engine. It certianly isnt a consensus.

2- Maybe your right and maybe Im right reguarding what Vizzard meant by his "the motors we are dealing with here", statement. Again, it doesnt specify.

3- A question, the 15 hp ""average" gains by mild porting pretty much is a consensus in reguards to iron. What do you think the "average gains" would be for adding headers to the same motors? (280-350 hp). ? Frankly Im kind of suprised that he gained that much by basic porting..
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Old 01-18-2009, 02:12 PM
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Originally Posted by 65smallblock
If I suggested that anywhere then I will consider myself corrected, but I dont think I did. All I was really trying to say is that they are more usefull after more power is achieved than basic stock applications.
No, you didn't say that. But I wasn't directing my comments specifically at you. I was just weighing in on the general "all manifolds are junk" and "no street car needs headers" tug-of-war.

Quote:
Just a few thoughts Ive had re; this "dead horse"

1- Im thinking that the case of the camaro could well be an extreme case, IE; terrible exhaust system to match the rest of the smog engine. It certianly isnt a consensus.

2- Maybe your right and maybe Im right reguarding what Vizzard meant by his "the motors we are dealing with here", statement. Again, it doesnt specify.

3- A question, the 15 hp ""average" gains by mild porting pretty much is a consensus in reguards to iron. What do you think the "average gains" would be for adding headers to the same motors? (280-350 hp). ? Frankly Im kind of suprised that he gained that much by basic porting..
The gains may be extreme. I don't know, as I haven't played around with any smog-era Camaros. But the term "terrible exhaust system" applied to all of the cat-equipped GM products of the era. GM was using a pellet-type catalytic converter that was just like sticking a big cork in the middle of your exhaust. The exhaust gases had to wind around each little pellet inside the cat. At the time, Ford was using a honeycomb design which allowed the exhaust gases a less restrictive, straighter route. At the time, everyone from Hot Rod magazine to David Vizard discovered that replacing the GM cat with a Ford cat was worth HP, as almost anything was an improvement.

Speaking of Vizard, I recall somewhere in one of his books in the series (How to make HP, vols 1-3) that all the results were on his engine dyno. I'm not going to swear to that, as I don't have the book in front of me right now or the time to search it. But 213HP at the rear wheels is in the neighborhood what a lot of late '60's/early '70s muscle cars actually produced. I can see an LT1 making that. In '71 it was rated at 330 SAE gross HP/270 SAE net HP. So if you put that on a chassis dyno and got 213HP at the wheels, I'd buy it. But the '81 350 rated at 175 SAE net HP obviously wasn't in the same league as a '71 LT1.

If on its best day Chevy could have produced a small-block '81 Camaro that put out 213HP at the wheels on a chassis dyno, people like me who had gotten their drivers licenses just after the muscle cars had been killed off wouldn't have been so depressed about the future of cars. Which is why I got into hot rodding in the first place. Everything from the factory just sucked. At one point in CA the biggest engine Chevy offered in the 'Vette was the 305. I mean, even the cops with their new police-package cars found they couldn't hit 65mph on a grade unless they reduced drag by taking the light-bar off (not that I was depressed about that). The last thing I wanted when I graduated high school was a new Z28, a Trans Am with a flaming chicken, or (worst of all) a Mustang II "King Cobra." Fortunately, people were practically giving away muscle cars because all anybody cared about was MPG. A cherry 383 Super Bee? $800. My '68 Charger with the Police Pursuit Special 440? A grand. That I could swing bagging groceries part-time. Even after selling my first hot rod at a loss, the '68 Ranchero that kept eating transmissions.

As far as Vizard's porting goes, I'm also surprised by his results. Mostly because Randy Brzezinski gained just a little more by using his ported/modified manifolds AND his 2 into 1 collector. Brzezinski says his modified manifolds are worth 6-11HP over stock manifolds and his collector. On the one hand, Vizard says he couldn't duplicate Brzezinski's results, on the other hand it looks like he exceeded them as he says he saw an ave. 15hp gain/max 22hp gain with just basic porting. The numbers don't quite add up.

So it's dangerous to speculate using Vizard's numbers. But taking them both at their words, modified manifolds and a well designed exhaust sytem on engines averaging just over 300hp (i.e. between 280 & 350) CAN see 65% of what they COULD see with headers. Not that they will, they could. And as you point out, the more you modify your engine the more of a gain you can get. Because it's just a fact that you have to burn "x" amount of gas to get "y" amount of HP. As x and y go up, so does the amount of air you'll need to support combustion.

Last edited by BinderDriver; 01-18-2009 at 02:36 PM.
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Old 11-09-2009, 04:11 PM
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OK, and now ...

Building a small small block, as in 283 bored 30 over. We'll be making about 9.5 CR with small chamber 305 heads (601 53cc castings). Those heads have miserable exhaust ports with EGR ports, but they can flow if opened up. Early Vette Rams Horns are about 33% bigger at the port than the 305 manifolds (with bolt boss intrusions) and they are known to flow better than log manifolds.

So round one is to use some old Vette iron manifolds so I don't need gaskets, they don't add noise in the cab, and they are tight fits so they don't interfere with other things going on under hood. Since it's a truck, it'll spend most of it's life at 3K or less.

But, it is a 283 and they like to wind. So after it gets broken in and all the tuning is out of the way, we'll likely wind it once in a while even if only passing (I do live on a 2 lane road and passing is a contest). With that in mind, I may step up to the lovely True-Ram style. They will flow a bit more and they look cool. The down stream parts are already 2.25" all the way back with H pipe.

Now my curiosity about bad mouthing the factory guys? If headers fit a wide range of uses and made more HP, that is free efficiency and should make the car easier to demo and sell? I know some iron manifolds are purely for fit in the engine room, but others like the ones on my 454 are sort of cast iron headers with individual runners.

No, not sonic lengths, but maybe minimum lengths to keep pulses from interfering in the critical first few inches until they have had a chance to spread along the pipe and soften their bark? There has to be some pressure pulse/charge volume length factor here to consider? Where do these pressure pulses soften enough to not be to much problem running into each other? 2" out, 6" out, maybe on foot if the engine is big enough?

I'm thinking back to all the 1960's factory hot rods like the hemi and wedge headed Mopars and their sweeping cast iron headers. Same for Ford and the 427 motors and other big FE engines. I'm guessing here, but I think the engineers worked to the point of diminishing returns and that's where they drew the line?

Also, other than corvette SS short tube headers, I don't know what will last 100K miles without replacement, blown gaskets, etc. Trucks need power, but they need to finish the day to. Race cars, maybe not ? It's the truck that tows the race car home, good day or bad
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Old 12-25-2012, 08:51 AM
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follow up question/update on an old thread

Quote:
Originally Posted by 49willard View Post
I am trying to decide which cast iron exhaust manifold to run with my sbc 330hp crate motor in my 49 Ford pickup set up with a Jag xj6 IFS. After trying essentially every available header set (none will fit on the drivers side), I come down to a choice between the 2" curved dump rams horn (straight dump will not fit therefore no 2 1/2" rams horn), the under the plug log style or the over the plug log style. Does anyone have data or comparison performance info on these different manifolds? Since the truck is being setup to tow a car trailer, mid range torque is really more important than high rpm hp. I understand that I could custom build headers but that is more effort than I want to expend on exhaust.
I apologize for bringing this thread back however I have an update and a follow up question. Back 3 years ago when I started this thread, I had planned on a GM crate 330 hp. An engine builder friend then said why not build a 383 instead since I already had a 350 4 bolt block. To make a long story short, I built a clone to the GM 383HT. Another restoration interceded however I am back now on the F-1 and am at the point of putting together the exhaust system. The way that I will use the truck has not changed i.e. low to mid range torque to tow up to a 5000 lb. trailer and I do want to stay with the 2" GM angled back rams horn manifolds for reasons of fit (around my Jag IFS) and $ (I own them). The question is, is there any advantage in trying to run the dual exhaust any larger than 2 " diameter pipe? Given the donut design of the 2" angled rams horn manifolds, the only way would be to transition up to larger pipe greater than 2 " would be an expander in the pipe downstream of the 2 " restriction at the exit from the manifold. It does not make sense to me but I would appreciate the thoughts of others on the forum. I do appreciate the postings in the past to this thread. What do you think?
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Old 12-26-2012, 09:21 AM
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Quote:
Originally Posted by 49willard View Post
I apologize for bringing this thread back however I have an update and a follow up question. Back 3 years ago when I started this thread, I had planned on a GM crate 330 hp. An engine builder friend then said why not build a 383 instead since I already had a 350 4 bolt block. To make a long story short, I built a clone to the GM 383HT. Another restoration interceded however I am back now on the F-1 and am at the point of putting together the exhaust system. The way that I will use the truck has not changed i.e. low to mid range torque to tow up to a 5000 lb. trailer and I do want to stay with the 2" GM angled back rams horn manifolds for reasons of fit (around my Jag IFS) and $ (I own them). The question is, is there any advantage in trying to run the dual exhaust any larger than 2 " diameter pipe? Given the donut design of the 2" angled rams horn manifolds, the only way would be to transition up to larger pipe greater than 2 " would be an expander in the pipe downstream of the 2 " restriction at the exit from the manifold. It does not make sense to me but I would appreciate the thoughts of others on the forum. I do appreciate the postings in the past to this thread. What do you think?
Having a short restriction coming out of the manifold into a larger diameter exhaust pipe isn't ideal, obviously. But intuitively I would say it would be less restrictive overall than using 2" all the way to the back.

Using 2" dual exhaust pipes is a case where a connection between the two sides (made as close to the engine as practical) should make a difference.
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