Just once more (exhaust)

Well, I wasn't really thinking about a whole system from magnaflow, just the mufflers. Think I saw em on amazon for about 80/per. Or, I guess it wouldn't hurt to consider pype's race pro or violator mufflers. Either way, I was thinking just getting the mufflers and having the guy build a crush bent system.
If I did buy a whole mandrel bent system, I was thinking that first pypes system I linked. But even their smallest system is 2.5"...
I don't want to rob myself of low end with pipes that are too big, but I still don't have Any metric to judge what kind of power difference we're talking about. Something probably any average joe would notice in the seat of their pants, or something only track racing guys notice when they're trying to shave off tenths?

I had the transmission rebuilt a year ago. The issue with it not kicking down was worse then, so I thought they had fixed it. It only kicks down to second if I'm going slower than 50mph, maybe even less than that..
It only kicks down to first if I'm under about 20.

 

Good to know I'm not the only person who jumps into these kinds of things without really knowing much about it and learning along the way.
One thing I have learned, many times, since starting on this car: even when I think I'm 100% prepared, there's always something I'm missing or didn't account for. Working on cars sure is frustrating sometimes when you don't have a shop, lift, and immediate access to all the tools you could possible need. haha
I've been held up more than a few times because I needed to order an obscure part or some tool, usually because of some unexpected complication that I should have somehow expected haha ou:

 

Sure go get the magnaflo mufflers. And that trans needs to be checked. A 350 trans should downshift better then you describe. They may have messed up cable or valve . Sounds like it's shifting more on vacuum modulator only. 2.5 is ok for stock engine. But H or X pipes would improve power

 

There's also this Pypes system with violators and an X pipe..
http://www.summitracing.com/parts/pye-sga10v/overview/make/buick/year/1972/model/gs


Whoa, what happened?! Up until just today, there had been an abundance of the Magnaflow's I was looking at (#11226).
All of them were between $73ish and $80. Now there is less than a handful on amazon, starting at $87.
I wouldn't have expected that to happen overnight.

 

Check eBay and summit racing

 

Idk, I still think I'd rather stick to true duals for the sound, over possible gains I may or may not notice with the x pipe.

I think I'm just gonna have to decide if I would rather pay maybe Around $200 more for the complete Pypes system (after install)http://www.summitracing.com/parts/pye-sga30v/overview/year/1972/make/buick/model/gs

Or save a bit by just buying those Magnaflows and having the crush bent exhaust shop system.
I feel like It might make a little more sense to get the Pypes 2.5 Now, so that in the future when I get around to waking up my engine I'll already have an appropriate exhaust, right?

 

You will realize ZERO gains with a full X-pipe 2.5" system with your current engine with manifolds! But with an upgraded engine with a bigger cam the 2.5" X-pipe system could be a good choice?

Your $$ would be better spent on a set of headers rather than mufflers or a whole exhaust system for now, just hook them up to your current dual system. If you want your exhaust to be more obnoxious sounding then a cheap set of cherry bombs would do the trick.

I went from a 2.00" dual system no crossover with cherry bombs and manifolds, to headers and a pipes 2.5" X-pipe system that netted virtually ZERO gains at the strip! To top it off it didn't sound as good with the new mufflers than it did with the Cherry Bomb glass pak mufflers! And this was with my sbc 383 stroker engine, with 33 less cubes you will probably lose power instead of just being a wash.


If you have a 2.00" dual system now that is in good shape, keep it add headers and some cheap Cherry Bombs and enjoy the loudness! Even with keeping your manifolds and just adding the C/Bs you will get the sound you want for even less $$$ that can be saved for future work on your car like a better rear gear that will give you way more gains than all this exhaust WAY over engineering discussed here. GL



Derek

 

Haha I been there too! Every time I say estimate how long a job is going to take, it always ends up being at least twice what I thought. Stick with it! Wrenching can be a real pain sometimes, but driving something that you worked on yourself is worth it.

Also if you end up going with cheap glasspacks, try a pair of Dynomax Race Bullets. They aren't much more expensive than your run of the mill cherry bombs and they have drilled, not punched holes. They also sound mean as hell!

 

Interesting May not apply to SBB


https://youtu.be/_PVXvHkr-Vs?list=PL7bCv2WuVwPR4vuk6T_wI6Wy-O-jZuHE_

2.5 vs 3 inch comparison

 

^^ Agreed :grin:

 

Not being critical...
Was the formula using a temperature constant?
The need for pipe area isn't as critical the further back you go as the gases cool and contract...

Anyways, borrowed from Google;

Generally road engines will require the manifold to be tuned to the max torque rpm whereas race engines will be tuned to work either at max bhp rpm or a speed midway between the max bhp rpm and max torque rpm.

4 -1 manifolds restrict the the power band whereas 4-2-1 manifolds give better mid-range power but reduce top end power by as much as 5-7%.

Generally speaking with a 4-2-1 manifold the starting point for Primary pipe length is 15 inches, thus Secondary pipe length is P - 15 inches. Changing the length of the Primary pipe tends to rock the power curve around the point of max torque. Shorter Primaries gives more top end power but less mid-range, and vice-versa. There is, however, little change in the peak torque or the rpm where this occurs.

Ideally the Primaries should come off the cylinder head in a straight line for around 4 inches before any turns occur.

Inside diameter of the pipe can be gained from:

ID = ? [cc / {25 x (P + 3)}] x 2.1

Where:
cc = cylinder volume in cc.
P = Primary length in inches.

In some engines it can be useful to have a 'step' between the exhaust port and the Primary (ie the Primary bore is greater than that of the exhaust port). This tends to be the case in engines with rectilinear exhaust ports.

For a 4-2-1 system then, Primary pipe diameter is calculated as above. Secondary pipe diameter is given by:

IDS = ?(ID x ID x 2) x 0.93

Where:
ID = calculated inside diameter of the primary pipes.

The pipe diameter can be used to change the peak torque rpm – a reduction in diameter of 0.125 inches will drop the peak torque rpm by 500-600 rpm in engines over 2 litres and by 650-800 rpm in smaller engives. Increasing the pipe diameter by 0.125 rpm has approximately the opposite effect.

The total length of the Collector and Tailpipe (to the front of the silencer) sould be equal to P + 3 inches (or any full multiple of P + 3 for a road car).

Tailpipe internal diameter is given by:
IDT = ?[(cc x 2) / (P + 3) x 25] x 2

Where P is calculated as above.

Collector length is given by:

CL = [(ID2 – ID3) / 2] x CotA

Where:
ID2 = diameter of Collector inlet
ID3 = diameter of Collector outlet.
CotA = Cotangent of angle of Collector taper (which ideally should be around 7-8 (certainly less than 10).

The design of the collector should be such that the inlet pipes terminate abruptly otherwise the tuned exhaust pressure wave will carry on into the tailpipe and the calculations done to get the negative scavenging wave back to the exhaust valve on time will all be wrong

[tailpipe calc is there but I included the entire excerpt. You can leave out the author's opinion and just use the math if desired]

 

Much more powerful engines CAN breathe though a more restricted exhaust, you just begin to lose some of the max potential.
Kind of like an air cleaner not quite up to snuff, might not be noticeable except for that last "blip" at peak rpm.

 

So, what if I decided to consider headers?
Would a low Hp stock motor like mine benefit at all from them?
If it does have a noticeable improvement (Hp worth $500??) in power even on my car, how would the rest of the exhaust be set up ideally?

I wanted headers in the beginning, but I talked myself out of them. My biggest issue with them is how low they will hang. I just redid the suspension and it dropped the car 2". I don't need anything hanging really lower, looking to scrape on unanticipated bumps in the road.
On top of that, I've read a lot about people having problems with leaky headers. And that they make the car hot.
Do people with headers have to routinely check and tighten them back down?

 

Headers do have maintenance. As in retorqueing. In most cases. Some people have good luck , some don't . Yes they will give you a increase in mid to upper power. 2 inch exhaust from headers will be ok but if you plane to improve later you may want to consider bigger system. Also consider price. Summit has a house system of just pipes for about 200 for 2.25 pipe. Flowmaster American thunder is 300 plus for their pipes no muffler but has balance tube. Nice system my brother has it on my old car. I have a magnaflo with X pipe. I don't have headers . TA head pipes. Was not hard to do myself. My engine has higher compression with a TA 310 cam and 3.73 gears. Cherry bombs are not for me. Sounds like a truck. Afterburner or thrush welded sound like flowmaster . But cheaper.

 

Long tube headers will usually help low and mid range power as well as part throttle, not just mid to high rpm.

 

Does anybody have pictures showing how low headers will hang?
I saw a photo a while back that made me worried about the clearance. And that was when the car rode 2" higher.
You've also gotta remember, this is my daily driver and only car. So clearance is definitely an important concern. Sometimes I go places I've never been, and there's no telling what road conditions are like somewhere you've never been lol.

If I wasn't so worried about clearance, then Maybe the constant maintenance thing wouldn't seem like such a big deal.
I think this is basically how I talked myself out of headers in the first place. The 'cost' of having them just doesn't quite match my personality..
It sounds like a pain to have to be torquing them down all the time, And always being super cautious like granny on unexpectedly rough roads. And uneven transitions, like driveways. Lots of roads turn off with steep-ish spots like that.

Guess I can rule out jumping the railroad tracks anymore if I install headers. Hahaha jk

 

As far as I can remember from when I was able to look at it in the air (obviously should've done some measuring in retrospect), my current exhaust is set up like this:
2" downpipes, to what seems to be 2.5" all the way back to the mufflers, which Are cherry bombs, and then 2" tailpipes. All crush bent.
The problem is, like I mentioned, the system is not in great shape. There are little holes throughout. But the most noticeable leak is conning from the manifold I believe.

 

Gary, your info is good but WAY to much for a simple question from someone new to old cars. Instead of being "educational" you may be confusing the guy more than helping, turning his thread in your personal technical outlet instead of starting your own to keep(IMO) your over engineering of exhaust that would probably be good for possibly factory "stock" racing rather than for a DD car for someone that doesn't have the resources to pickup the an extra 2 to maybe even as much as 7 more HP using your techniques with trial and error on the dyno to see which one gives the 7 instead of just the 2 extra HP.

The guy wasn't trying to add performance, he just wanted to sound like his car can perform by adding some cheap mufflers that make more noise.(is what I got from his posting anyway)

Well the real world answer is a set of cheap glass paks that won't break the bank if his current dual system is in good enough shape to swap mufflers?(as in not to badly rusted out) At this point headers aren't really necessary if the funding isn't there?

That way he can save his $$ for real upgrades like better gearing either from a trans swap or a rear gear upgrade.( $500 would be better spent on a trans or rear gear at this point.)



Not trying to start a long debate on this with you Gary(I usually enjoy reading your technical writings), just my opinion of what the answer he really wanted is. :beer





Derek

 

Well I kinda meant a picture on the ground from the side. But thanks.
Just curious, is your swaybar not completely attached in this picture? Mine curves around the pumpkin, not under it. Looks pretty low hanging