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back pressure,needed or not

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MrSmog View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrSmog Quote  Post ReplyReply Direct Link To This Post Posted: 25-July-2017 at 4:38PM
I love when engineers talk, you know, the ones that bury oil filters behind things so you remove all flesh on your hand gettin it out, require truck cab removal to work on a engine and all sorts of other glorious things. I recall a whole forum of engineers told me I couldn't swap a inboard jet drive to a bracketed outboard (I did it easily), another half dozen told me I couldn't swap a v10 in place of a 318 without massive frame damage/suspension failure ( I did it easily), and a few other things they said was impossible. Some people over think things. To the original poster, many people run cats with no mufflers, you'll be fine. As for the zoomies destroy engines, tell that to all the rat rod/street rod guys who run them and have run them for years with no ill effects.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fordpower Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 12:57AM
Who would have though my question would make such a topic. All I know is remove all smog s plug the egr valve and the car ran worse. Gas millage went down car vapor locked seemed t less power. Everyone had said get rid of all that sh*t it will run 100% better wrong.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Don V. Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 3:01AM

Originally posted by MrSmog MrSmog wrote:

I love when engineers talk, you know, the ones that bury oil filters behind things so you remove all flesh on your hand gettin it out, require truck cab removal to work on a engine and all sorts of other glorious things. I recall a whole forum of engineers told me I couldn't swap a inboard jet drive to a bracketed outboard (I did it easily), another half dozen told me I couldn't swap a v10 in place of a 318 without massive frame damage/suspension failure ( I did it easily), and a few other things they said was impossible. Some people over think things. To the original poster, many people run cats with no mufflers, you'll be fine. As for the zoomies destroy engines, tell that to all the rat rod/street rod guys who run them and have run them for years with no ill effects.

I'd like to know what forum of engineers told you this and the circumstances of your question. Attitude can make a difference too. Maybe the information you got was about something other than your question?

If you want to blame engineers for putting 10 pounds in a five pound bag, feel free too. It's really ignorant but if you need someone to blame. . . .

I decided to leave the NHRA rules about top fuel cars and the time they get between races used to rebuild the engine out of my last response. What does anyone know about the effect of zoomies when the engine they are using has a quarter mile lifetime? The blocks? Maybe a 3 mile lifetime.

This is from Jim Thorton who the NHRA recognizes as the inventor of the funny car. Paraphrased, "Nitro burning cars are no different from any other car when evaluating exhaust. Power is forfeited with straight pipes but the cars run so rich headers become a pipe bomb halfway down the track. Choosing between the advantage of headers or nitro with straight pipes didn't take a lot of thought. There's also no doubt straight pipes are the better crowd pleaser." 

Mixing street cars and track cars about zoomies? OK I guess? The effect of zoomies on engine life and power I thought was pretty well understood since the 50's. Typically the same engine on a dyno with both zoomies and tuned headers creates more power with headers. It didn't take much searching of hot rod websites to verify this. The earliest versions of the Merlin engine in the P-51 Mustang engine is a good place to start to learn about the effect zoomies have on engine life. There's not much to compare between an engine designed to operate at ground level to 25,000+ feet but it is a good place to start. On the street, the effect zoomies have on engine life I thought was pretty much taken for granted.

On the street zoomies are about some combination of looks and sound and have little to do with performance. The few places where you might get away with running zoomies legally on the street usually at least require zoomie baffles. I don't know this for sure but I imagine true, straight pipe zoomies are pretty rare on the street. Legally anyways.

If anyone wants to limit back pressure to the purvue of exhaust then I agree, back pressure restricts exhaust potential. If anyone wants to consider the exhaust as part of the balance of the entire system then the answer begins to look a bit different.

I would like an explanation though of why of the two common header designs, restriction and velocity, velocity is the better performer? Restrictions increase back pressure in the exhaust system so why are designs aimed at restriction reduction the poorer performer?

Don V.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote fordpower Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 3:21AM
Please do.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Don V. Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 3:23AM
Originally posted by fordpower fordpower wrote:

Who would have though my question would make such a topic. All I know is remove all smog s plug the egr valve and the car ran worse. Gas millage went down car vapor locked seemed t less power. Everyone had said get rid of all that sh*t it will run 100% better wrong.
The early days of emission control involved taking existing designs and adapting the emission controls to them. It was fairly simple to remove the controls and return the engines to their original designs. As the engines evolved and became more sophisticated there was no original design to revert to. Unfortunately a lot of people held on to their "engine lore," when it was just foolish to do so. Specific built, high performance engines aside, the typical engine today gets better gas mileage while producing substantially more power than it's predecessor. Why would anyone try to change it by removing\deleting components that are integral to its performance? Still. a lot of people believe they can improve an engine while having zip knowledge of ECU programming which would be required for any chance of succeeding. Bear in mind the "Tuners" mentality is often to refer to tuning as programming which it isn't. Tuning is akin to changing the font on your word processor. That's not programming and has nothing to do with what would be required to remove the emission controls on a modern engine.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 3:47AM
Originally posted by fordpower fordpower wrote:

Everyone had said get rid of all that sh*t it will run 100% better wrong.
 
Originally posted by Don V. Don V. wrote:

I'd like to know what forum of engineers told you this and the circumstances of your question. Attitude can make a difference too. Maybe the information you got was about something other than your question?
 
I've seen that response here several times fairly recently, sometimes w/o regard to inspection regs
and certainly with no plan to recalibrate the tune after removing 'all that sh*t'
 
FWIW the laws regarding emissions systems are still alive, and the board here needs to be respected
concerning careless shooting off at the keyboard with 'get rid of all that sh*t it' replies
 
=======================
to the OP, not sure if you've seen my comments regarding reduced  ~backpressure~ for a daily street driven car but I've been shocked at the difference between a 2>1 single pipe to the rear bumper and a simple dual dumping before the rear axle. night and day would be an understatement it was more like an equatorial eclipse. the gas pedal went from a very sensitive throttle control to an old beat up work boot stuck in a bucket of 1/2 cured concrete. a previously nimble 350-2bbl lost all it's off idle finesse and required a significant amount of throttle angle just to get out of it's own way
 
it was not a Win Win Win
 
 


Edited by Rockatansky - 26-July-2017 at 3:48AM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stanman Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 4:08AM
Rock.....so going from single to dual exhaust made performance worse?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 4:41AM
pretty much that sums it up. as a daily driver 350-2bbl there was nothing to gain in the mid or on the top end that it didn't already do as a single exhaust. throttle response and driveability were in the toilet compared to before the exhaust system 'upgrade'
 
tailpipes would've probably helped get some back but those benders are proud of their work and demand to be paid accordingly, at that time an appointment with the fancy pipe machine wasn't in the budget
 
the exhaust system is certainly a deal maker / breaker for sure
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fordpower Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 5:12AM
I in know way am advising removing smog or emission system. In NY car is old enough that it makes no difference though. My exhaust system uses the cats because 15yrs ago they could not legally remove them.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrSmog Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 5:28AM
Originally posted by fordpower fordpower wrote:

Well thinking of replacing my cats.
tried to do some research on back pressure.I found it very confusing to say the least. does anyone have opinion . I like sound with cats and no mufflers.


my reply was in my own personal experience with the engineer types online, the reply to don who said zoomies destroy cylinder heads and the OP's question above. There is no reason a properly sized dual exhaust with just cats should hurt performance, in fact it should help. The same could be said for a stock 350 2bbl, can't imagine a set of properly run 2" duals on that engine would do anything but good. I think some people read too much of others opinions and then second guess themselves. I am about to put a set of 2" duals with 2.5" mufflers/tailpipes on my blue stock 302 car, I'll report back just how badly it runs, loses power and mpg afterwards. LOL
I have put duals on just about every V8 powered vehicle I had had for almost 30 years now, never had anything but positive results from it. Power always went up, mpg always went up if drove normally and the only negative I can think of is there was never enough tunnels to go through to hear it when I stomped on it.




Edited by MrSmog - 26-July-2017 at 5:28AM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 5:40AM
Originally posted by fordpower fordpower wrote:

Well thinking of replacing my cats.
tried to do some research on back pressure.I found it very confusing to say the least. does anyone have opinion . I like sound with cats and no mufflers.
 
to the original ? those old cats are Dead to any kind of performance / efficiency, today we have high flow cats that even allow a really decent exhaust note through them. a full system to the back bumper w/o some type of muffler or resonator might be too loud for your taste
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Bird Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 5:44AM
My cats are still in place, but the insides "fell out" probably 14-16 years ago.
I can't imagine having a big expansion chamber at the start of the exhaust is good for exhaust velocity or flow. However, they were still looking for converters on 1979 cars when I put it together.
The above post should be read in a "Grumpy Old Man" voice.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Don V. Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 6:34AM
Rockatansky,
 
If I gave anyone the impression that removing anything to do with emissions was a good idea or advisable I'm not. As far as the quote of mine you used, it was a response to comments from Smog that were about mounting engines which was part of his trashing of engineers. It had nothing to do with emissions.
 
Mr. Smog, I never said using zoomies will destroy an engine. The fact that zoomies "CAN" destroy heads or engines is not new or groundbreaking information. They have a long, documented history starting with burning valves. I also don't think zoomies shortening engine life is new or groundbreaking information. I don't equate shortening engine life with destroying an engine because there are numerous engine modifications that will shorten engine life. A common one I see is building a high performance, tight tolerance engine for the street. Tight tolerance engines are not for stop and go traffic and ideally they require a start up routine to avoid cold starts. Heck, cold starts aren't good for any engine let alone tight, or close tolerance engines.
 
My advice was that zoomies are not for the average garage mechanic. Just properly figuring optimum tip angle involves some intensive math. Most just weld up their idea of cool and that's not a good idea.
 
Big Bird's comment raises a good point. There are a lot of people with more money than sense so why aren't they running 8" exhaust pipe or 3" x 12" tube? That would sure mitigate any exhaust back pressure issues.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrSmog Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 7:27AM
I know guys who have had those open zoomie headers on their street rods goin on 20+ years, still the same engine, still runnin good. Go tell them they are killin their heads and see what kind of response you get. I'm sure they lead to more wear then a proper exhaust system, but how much so probably has way too many variables to give an exact number. The OP to this thread has no intention of puttin those goofy headers on his car, so it's really just a bunch of hot air gettin blown around for nothin, my own included.

as far as trashin engineers, It wasn't really meant that way, just sayin even they do some things that seem questionable to us common people.  I'm sure they are all smart folks, but sometimes you can over think things way too much and overlook simple solutions or alternatives. I have done a lot of oddball things in regards to boats, cars and trucks over the years. Not so much because I want to be a pioneer or anything, but more out of necessity or the hot rodder in me. Almost always I was met with the nay sayers who would spout off all this technical mumbo jumbo of why it wouldn't work, or would implode unexpectedly because it was never designed that way.  So far, so good by usin good ole common sense and my own "backyard engineerin".

If you felt I personally insulted you in any way, I apologize. If I can make it up to the pure stock drags this year in Mich, I'll buy you lunch and tell you a few lawyer jokes. Beer
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 11:31AM
we're all fine as far as i know, my comment wasn't aimed at anybody in particular but as i said I'm pretty sure the blanket 'rip that crap off' advice does come out quite frequently and we need to be careful. i should've went on further as i was thinking at the moment that it's easy enough to specify usage being 'for off road use' or 'educational purposes' that there's no reason to risk attracting unwanted attention.
 
for that matter they already are going outside intended use of statute and threatening off road vehicles sheesh
 
and don't get me started on engineers LOL they are a special bunch. if the part number doesn't match exactly it won't work. long story short there was a guy at work that insisted the tube in a radiator is called a jacket water because that's what the print called it, 'jacket, water' jacket water my Censored
Originally posted by MrSmog MrSmog wrote:

Go tell them they are killin their heads and see what kind of response you get.
 
i can imagine a Steve Austin 3:16 beer over the head?
 
who said zoomies? i still have the set i had on my 72
 
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fordpower Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 12:49PM

rock you sort of ans my org question. My garage said my cats are plugged causing my problems.He said they are to hot at intake and to cold at exhaust so should I do away with and go with mufflers.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Bird Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 1:42PM
Originally posted by Rockatansky Rockatansky wrote:

for that matter they already are going outside intended use of statute and threatening off road vehicles sheesh 
Misuse of laws/expansion beyond mandate should be a criminal offense, punishable by a swift kick in the crotch on Primetime national TV, administered by the kicker from the previous year's Super Bowl champions. Big smile
The above post should be read in a "Grumpy Old Man" voice.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Don V. Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 2:07PM
How do you get a zoomie that's not really a zoomie? You buy a header from a company that puts the word zoomie on some header lines and buyers can say they have zoomies.
 
Rock, the dragster you posted is an example of zoomies. One tuned straight pipe per cylinder pointing down and then up. They weren't about looks or sound. They were\are functional. They create a lot of down force that helps counteract both torque twist and front end lift. Top fuelers today have so much power zoomies are factored in to suspension and chassis design. This is information that can be found on the internet and not from anyone referring to jacket water.Confused
 
Are pipes that don't turn up zoomies? According to the old timers no but they became popular when zoomies made it to the street where the upturn wasn't appreciated by the cars to your right and left. FWIW and again from the old timers, the term zoomie was slang in the nuke industry for the unseen energy emitted from radioactive materials. Hot rodders co-opted the term.
 
zoomies:
 
 
Put a collector on the end of straight pipes and you've got a header which is not a zoomie.
 
I'm not interested with arguing this with anyone but when I refer to a zoomie I'm talking about a single, stand alone straight pipe per cylinder.
 
Smog, I appreciate the clarification.
 
Ford power, sorry about your post getting hijacked but it seems your answer is in here. My 2 cents, go for it. If you need to go back to using mufflers there's nothing in your plan to prevent you from adding them if there turns out to be a reason to. The effect a muffler has on emissions is minimal.


Edited by Don V. - 26-July-2017 at 2:11PM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Don V. Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 2:17PM
"Misuse of laws/expansion beyond mandate should be a criminal offense, punishable by a swift kick in the crotch on Primetime national TV, administered by the kicker from the previous year's Super Bowl champions. Big smile"
 
Is this an updated version of "Get off my lawn," "Grumpy old man," or both?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrSmog Quote  Post ReplyReply Direct Link To This Post Posted: 26-July-2017 at 2:22PM
ford power, if your new cats don't have the sound you like, try a set of glasspacks after the cats. This is my cheap hi-po exhaust on anything I have with cats, the cats take enough starch out of the exhaust note that the glasspacks aren't cackly and obnoxious, has a nice deep mellow sound that really comes alive when ya tromp on it.
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