Any experienced exhaust Guru out there?!?!?!?!

[Dan Jones]

Vizard covers anti-reversionary headers in "Performance with Economy".  
His testing was on a V8 with bank separated 4-into-1 headers with the AR
cones built into the flange.  The cones act as a diode, allowing flow
out of the exhaust port but not back in and are less sensitive to larger
primary sizes (though you should still pick the best diameter for your
operating range).  His conclusion was that AR headers work well, providing
better fuel economy and power but a cross-over is mandatory.  Also, the
carb will need to be retuned as the AR headers provide a stronger signal.
The extra power comes primarily in the low and mid-range if the primary
pipe diameter is held constant.  One example cited was a 305 SBC powered
Malibu that went from 17 to 21 MPG with no other changes other than fitting
AR headers.  Another example was an engine that wouldn't run smoothly below
4000 RPM due to reversion was able to run at 3000 RPM.  Blackjack and Cyclone
were the holders of the patents but have since been bought out and, AKAIK,
the AR line was dropped.  You may be able to buy pre-made flanges from a
company like Headers by Ed.  The Japanese import crowd have been using AR
chambers in the primaries similar to the exhaust shown.

Dan Jones

[MGB-FV8]

Here's a link that explains exhaust almost to perfection:

http://www.popularhotrodding.com/enginemasters/articles/hardcore/0505em_exh/index.html

[BlownMGB-V8]

Not much said there about the resonator cones. It occurred to me that I'm in a perfect position to add those to my system as I have to shorten the pipes about an inch due to added engine width. Somehow I keep removing simplicity. Now the question is the best method.

One point I'd like to add is that the recommendation in using the primary sizing chart was to concentrate on the "RPM range of interest" in determining primary size. Note that the closest thing to rpm given was the amount of flow, so if your primary range of interest is daily driving the flow rating will be a mere fraction of what it would be for maximum performance, and better to err in a downward direction. So then, if your heads flow 150-200 cfm but you only put your foot in it on rare occasions, maybe those 1-5/8" primaries aren't needed.

Another point, relating equal length primaries to race engines where a <3000 rpm band makes such unnecessary, in street driving, and especially spirited mountainous driving where the desired usable RPM range can be in excess of 4000 rpm easily, equal length primaries make a whole lot more sense.

YMMV

JB

[roverman]

Jim, are you expecting to have "reversionary flow" problems, with that bad-boy blower strapped on there ? Going to dyno this build ? Measure "pressure" in the exhaust ? If so, I suspect you'll find 1 3/8" primaries, overly restrictive ? Good Luck, roverman.

[BlownMGB-V8]

Doubt they'll be any more restrictive than the exhaust valves and ports. Remember Art, this is not a max HP project. Despite the blower, the goal is not ultimate top end performance, but all around driveability and good economy. Adequate power will be there. There is nothing to choke power down to levels below what I was producing with the 215, which was in the 300hp range and the headers were quite adequate for that application. If you'll recall, Vizard's recommendation was to err downwards in tube size, and I also had the opportunity when they were built to pick the brains of Ed Henneman ("Headers by ED"), one of the most knowledgeable exhaust system guru's on the planet at the time. (mid 80's) The tube size was optimized for a 300 cu.in. engine so yes, for a normally aspirated 350 at full tilt-n-boogie it'd probably be a little undersized and a few ponies might be lost at the top. But for a blower motor that is going to spend 99% of it's life under 4 grand? Even if it does see 7 on occasion I think these tubes are going to turn out just fine. Remember, I consider 300hp in an MG to be adequate and the goals of durability and low maintenance are equally important. I could put a cast iron manifold single exhaust on the car and meet that goal sitting in the shade, so how are those 1-3/8" primaries going to hurt?

JB

On the dyno question,.... maybe. I'm not sure what real purpose it'd serve. I'm not aware of a shop that has one around here so it's an investment in time and money that can be better spent other places.

[Dan Jones]

> One point I'd like to add is that the recommendation in using the primary
> sizing chart was to concentrate on the "RPM range of interest" in determining
> primary size. Note that the closest thing to rpm given was the amount of flow,

The amount of flow is a function of the valve lift for a given cylinder
head, not an indicator of RPM.  If you click on the graph, the primary
sizing curves are explained:

 "Fig 4 This chart applies to normally aspirated engines. For street headers,
 where low-speed torque is of prime importance (especially with a stock
 converter and high rear end gears), use the lower line to select the
 appropriate primary size. For hot street machines having reasonably big cams
 and decent compression, use the middle line to size the primary. For race
 engines, use the top line. If nitrous is involved, check out the nitrous header
 section."

The lower curve is best applied to heavier vehicles with automatic
transmissions and/or tall final drive ratios and would be conservative on a
lightweight British car with a big American V8, a 5 speed, good cylinder
heads and a decent cam.  AFR 165's flow nearly 190 CFM on the exhaust side
(184 CFM @ 0.500", 188 CFM @ 0.0600", 189 CFM @ 0.700").  Assuming a cam
with modest 0.5" lift on the exhaust side, even the lower curve calls for
1 5/8".  Furthermore, a 5.0L HO with the stock E7TE heads only flows around
110 CFM at the same lift (grinding out the Thermactor bumps will help that
some) and Ford's stock tubular exhaust manifolds were sized at 1 1/2".

I'm working on a SBF with Floo Tek heads where I may use 1 1/2" primaries
for clearance reasons.  The Floo Tek heads are cast in Australia, assembled
in Indy and are essentially copies of the FRPP GT40 turbo swirl heads.  They
flow around 160 CFM @ 0.500" lift on the exhaust side.  They will be used in
a 1971 Mustang convertible with 2.79:1 final drive ratio and an automatic
overdrive transmission with 2500 RPM stall speed.  With an HO servo, the
transmission up shifts around 5200 RPM and there is only room for 2 1/4"
intermediate pipes through the convertible chassis bracing (though I'll
likely step up to 2 1/2" for the axle hop and Magnaflow mufflers).  If the
same engine were in a lightweight sports car with 5 speed manual transmission,
I'd for sure use 1 5/8", especially with heads like the AFR 165 with their
excellent exhaust port.  That assumes there is space permitting.  On the
convertible Mustang, I'll be running simulations to compare primary diameters
and collectors to help me make up my mind but I think the 1 1/2" primaries
will be okay if I optimize the collectors.

> where the desired usable RPM range can be in excess of 4000 rpm easily,
> equal length primaries make a whole lot more sense.

The paragraph following that discussion explains that, even with equal lengths,
much of the potential benefit is lost in V8's that use a dual plane crankshaft.
Things would likely be different with a flat plane crankshaft.  Also be aware
the presence of bends changes the apparent primary length.  180 degree headers
are much more sensitive to equal lengths and one builder of such headers I know
sizes the lengths acoustically so that each pipe tunes in on the same note.
You'll usually find better payoff by concentrating on the collectors.  It's
relatively easy to change collector length and styles.  One of the SBF drag
racers I know has had very good results with the merge style collectors on
evrything from a relatively stock fuel injected 5.0L to a high winding 289.

Dan Jones

[BlownMGB-V8]

It's also interesting to note what some of the SBB guys are doing with ported stock exhaust manifolds. Getting into the 12's with full sized cars running the 350 small block and cast iron manifolds, they claim about a 5-10 hp loss over tubular headers. That's 2nd hand, but those boys are fairly serious about their drag racing so even if it's padded a little it's still sort of impressive. The Buick manifolds are a pretty free flowing design.

JB

[Dan Jones]

> It's also interesting to note what some of the SBB guys are doing with
> ported stock exhaust manifolds. Getting into the 12's with full sized
> cars running the 350 small block and cast iron manifolds, they claim
> about a 5-10 hp loss over tubular headers. That's 2nd hand, but those
> boys are fairly serious about their drag racing so even if it's padded
> a little it's still sort of impressive.

The biggest difference between exhaust manifolds and long tube headers
tends to come at lower RPM (see my dyno data at the bottom).  Also, the
can be 20+ HP difference among different long tube designs.  I'd wager
those Buick headers aren't optimized and/or there is a much larger
difference at lower RPM.  The best of the SBF iron manioflds were the
K-code 289 hipo manifolds.  A better alternative would be the 5.0L HO
Mustang tubular steel "shorty" manifolds.  In addition to the OEM, there
are a wide variety of aftermarket versions available in 1 1/2", 1 5/8",
1 3/4" and 1 1/2" to 1 5/8" primary diameters, equal and unequal lengths
in mild or stainless steel.  Long tube headers still out-perform them but
they are useful where stock location catalytic converters must be retained
for emissions purposes or where long tubes won't fit.

Here's a magaxzine test of stock, K-code and long tube headers on a
dynojet.  Note it's a fairly mild 302 engine, through the mufflers and
the power is at the rear wheels.

 http://www.mustangandfords.com/techarticles/mufp_0607_ford_mustang_performance_exhaust/index.html

There's another test which recorded a much bigger differnce on a 347 SBF
stroker:

 http://www.mustangandfords.com/techarticles/engine/5157_headers/index.html

They claim 104.5 hp and 96.6 lb-ft of torque difference between Hooker
Super Comp headers and K-code manifolds. though it appears they also
installed a K&N air filter at the same time.

> The Buick manifolds are a pretty free flowing design.

The Ford 351C-4V engine has larger valves (OEM size is 2.19" diameter
intake and 1.71" exhaust) and their iron exhaust manifolds have
ports that are much larger ports than a Buick 350.  Here are
the results from dyno testing I conducted on a fairly mild
Ford 351C.  At 4200 RPM, where we started the pull, the iron
manifolds are down 59.1 HP and 72.6 ft-lbs of torque.  It
would be even worse down at 2500 RPM.  This is because of the
short length of exhaust manifolds.  The long tubes are able to
tune in at a lower RPM.  The gap narrows at higher RPM but is
still 26.5 HP at 6100 RPM.  Note that the long tube headers
are no where nearly optimized for this combination.  Still,
if you plot this data, you'll see the difference in area under
the curve is huge (more than you'd likely get from an expensive
set of aftermarket heads or port job).  Couple this with the
50 HP difference in mufflers we saw and you can turn a 400 HP
engine into a 300 HP with a restrictive exhaust.

Ford 351C-4V Dyno Project Engine
hydraulic roller street cam
flat top pistons
unported iron 351C-4V heads
12 inch extension and Magnaflow mufflers

Iron 351C-4V Exhaust Manifolds  Hooker 1 3/4" primary headers
RPM     HP      Torque (ft-lb)  RPM     HP      Torque (ft-lb)
4200   259.7   324.9      4200   318.8   397.5
4300   274.3   334.7      4300   325.0   397.7
4400   284.8   340.1      4400   331.6   395.9
4500   294.8   344.0      4500   339.4   396.1
4600   305.4   348.7      4600   349.9   399.2
4700   315.1   352.2      4700   360.6   402.9
4800   330.1   360.6      4800   368.0   402.8
4900   343.2   368.8      4900   372.4   399.5
5000   345.5   363.1      5000   378.0   397.0
5100   354.0   364.2      5100   388.6   399.7
5200   364.8   368.7      5200   397.1   401.1
5300   368.6   365.4      5300   401.3   398.2
5400   377.5   367.0      5400   404.9   393.8
5500   382.5   365.5      5500   409.9   390.9
5600   383.0   359.2      5600   412.1   386.7
5700   384.7   354.4      5700   407.9   375.8
5800   383.8   347.0      5800   401.4   363.8
5900   376.6   335.6      5900   398.9   355.1
6000   369.3   323.2      6000   401.3   351.2
6100   380.5   328.4      6100   407.0   350.2

Dan Jones

[roverman]

For the record, are we discussing ID. or OD. on tubing sizes ? Any solid data on merge collectors ? Stepped primary headers, properly built, function similar to anti reversion cones? Port mismatch at port can be "a" on flooor, "b" on sides, and "c"never on roof ?. Why not use oval tubes to fit available spaces ? Is it not the "area" inside the tube and bend radii ?Thanks, roverman.

[BlownMGB-V8]

Good info Dan, about the hp/rpm losses and the area under the curve. I have long been a believer in chasing that volume vs. absolute hp peak so to me this is very revealing (and to be honest, 5-10 hp loss sounded like pie-in-the-sky). I'm also a firm believer in long tube headers for the street. Art, I can't speak to others' comments but my measurements were inside diameter.

About the anti-reversion cones, I looked at some test results (Harley) and the graphs I saw showed no gain and an upper end loss due to restriction. These were slip-in cones that are simply inserted into the end of the header pipe. Starting to sound like snake oil, and I'm suspecting that any advantage is going to be in a very specific application under ideal conditions (racing perhaps). Without more than that they would hardly be worth the trouble. But having said that, a Harley exhaust is hardly an ideal tuned system. Also it seems they were primarily interested in eliminating a dead spot in the power curve where reversion was thought to be interfering and causing a power loss. All of this leads me to suspect that a properly designed set of headers is not going to have much of an issue with reversion and therefore the cones will be of little benefit.

JB

[Dan Jones]

> For the record, are we discussing ID. or OD. on tubing sizes?

The data is for ID.  Headers vary in their wall thickness with street headers
typically having thicker walls compared to race headers.

> Any solid data on merge collectors?

I've not personally tested them yet but will likely in the future on
mid-length Pantera 351C headers.  However, a SBF racer I know has installed
them on both his car and his son's (both record holders) and gone faster.

> Stepped primary headers, properly built, function similar to anti reversion
> cones?

Stepped headers approximate a constant taper angle.  I'm not sure if the
abrupt area changes have an effect on reversion or not.  If so, the mechanism
would be different (via finite amplitude waves).

> Good info Dan, about the hp/rpm losses and the area under the curve. I have
> long been a believer in chasing that volume vs. absolute hp peak so to me
> this is very revealing (and to be honest, 5-10 hp loss sounded like
> pie-in-the-sky).

Agreed.  Peak numbers are irrelevant.  The area under the curve in your
desired operating range (between shift points) is what really matters.

> About the anti-reversion cones, I looked at some test results (Harley) and
> the graphs I saw showed no gain and an upper end loss due to restriction.
> These were slip-in cones that are simply inserted into the end of the header
> pipe. Starting to sound like snake oil, and I'm suspecting that any advantage
> is going to be in a very specific application under ideal conditions (racing
> perhaps).

On a two plane crank V8 with bank separated 4-into-1 headers, Vizard's
testing indicated the AR effect required a cross-over to work.  That
testing used cones in the header flange.

> All of this leads me to suspect that a properly designed set of headers is
> not going to have much of an issue with reversion and therefore the cones
> will be of little benefit.

Reversion is more of an effect of the cam overlap, particularly the component
provided by narrow lobe separation angles.  Reversion occurs at lower RPM,
so don't expect to see any benefit at higher RPM.  Vizard's testing showed
the largest effect occurred at low RPM and trailed off as RPM increased.
He presents before and after testing in both "Performance with Economy" and
"How to Build Horsepower, Volume 1".  BTW, Vizard has a new version of "How
to Build Horsepower" coming out.  The second edition appears to replace
Volume 1 (an overview that covers everything).  Volume 2 covers induction
(carbs and intake manifolds).

Dan Jones

[BlownMGB-V8]

>Jim, have you read The High Speed Internal Combustion Engine by Sir Harry R. Ricardo?
>Funded to develop piston engines for the war effort, Ricardo did so without any
>regard to class rules. His work is at the base of everything hot rodders do, whether
>they realize it or not.

>Dan Jones

I'm not sure if you realize it Dan, but this book costs ~$350.00, not the sort of thing the average guy just goes out and buys. My local library is trying for an intra-library loan but I'm not holding my breath.

But I did run across a Vizard book in my personal library and will look it over again during thanksgiving.
Happy Turkey Day all. Let's not forget how we got here.

JB

[HealeyRick]

"Happy Turkey Day all. Let's not forget how we got here. "

The Pilgrims could have got here faster if they had stuck a V8 in the Mayflower!

[bsa_m21]

>I 'm not sure if you realize it Dan, but this book costs ~$350.00, not the sort of thing the average
>guy just goes out and buys. My local library is trying for an intra-library loan but I'm not holding my breath.

Oh come on.  There's a bunch of used ones on Amazon for as little as $250.   !!

Martin

[roverman]

Reportedly, the Pilgrims had a"Ford" in their fleet,(Pinto). Is that why it tookem soo long ? Perhaps "Sir Harry" charges soo much, posthostumously, is because his brother,"Ricky", got all the Press ? lol. and Happy Pilgrim Day.roverman.

[castlesid]

Dan,

Did I read somewhere above that your expecting 350 BHP from your 4.2, I built a stroked 3.9 with 4.2 crank, 5.85" Chevy rods and flat top with cut outs 305 Hypereutectic KB pistons to give 4350cc.

I have modded alloy 300 heads with 1.63" In and 1.4" Ex. with the seats taken out to actual seat size and the throats and bowls all blended to match, port runners are left as standard with a minor clean up as specifically for road use.
Static comp ratio a bit lower than I would have liked at approx 9.4/1

Induction system is currently Edelbrock 500 and manifold and exhaust is a RV8 through the inner wings system with single pipe.

Cam is Crower 50232

Ignition is a recurved lucas 35DLM8

Haven't had it dynoed as the result from rolling roads seem to vary wildly,  what would you think it should produce, I was aiming for 260+ BHP.

Regards,

Kevin Jackson.

[DiDueColpi]

Hey Jim,

Ricardo's book is available to read on line.
It's been a while and I was never able to print it but I'll try and find the address again for you.

Cheers
Fred

[BlownMGB-V8]

Thanks Fred, I'd like to see that. It turns out my library was able to get it for me and I've had a few days now to read it. A wealth of information there. I particularly liked this passage:

"...the finest achievement ever reached in any sphere of mechanical engineering, for it constitutes the best example of what can be accomplished by the co-operation of the scientist and the practical engineer working together in harmony. In every successful example it will be found that the actual designer of such an engine is neither a great scientist nor an expert mechanic, but an artist with an artist's temperament and intuitive genius, though none the less ready to appreciate and accept all the aid that the scientist and the practical mechanic can give him, and competent to blend his and their conflicting demands into a perfect picture. Such men are rare and in any one country can be counted on the fingers of one hand. Without doubt the greatest of them was Sir Henry Royce."
Sir Harry R. Ricardo: The High Speed Internal Combustion Engine pp. 280-282 (5th edition reprinted 1972)

To that I'd like to add a quote of my own:
"Aim high. You may fail miserably, but you will also know moments of true greatness. For this there is no substitute."

 JB

[Dan Jones]

> Did I read somewhere above that your expecting 350 BHP from your 4.2

Using the flow numbers from my GM race heads, Dynomation predicts between
323 and 359 HP, depending upon how efficient the single plane intake is.
The GM race heads were designed for Mickey Thompson's Indy car effort and
Lance Reventlow's mid engine Scarab.  Compared to my ported Buick 300 heads,
they GM race heads are better on the exhaust but worse on the intake due
to the smaller intake valve size.  On the flow bench, the exhaust flows
173 CFM at peak compared to an unported Rover flow of 92 CFM.  Because of
the strong exhaust port, a custom cam was required to match the flow
characteristics to maximize the horsepower.

> I built a stroked 3.9 with 4.2 crank, 5.85" Chevy rods and flat top with
> cut outs 305 Hypereutectic KB pistons to give 4350cc. I have modded alloy
> 300 heads with 1.63" In and 1.4" Ex. with the seats taken out to actual
> seat size and the throats and bowls all blended to match, port runners
> are left as standard with a minor clean up as specifically for road use.
> Static comp ratio a bit lower than I would have liked at approx 9.4/1
> Induction system is currently Edelbrock 500 and manifold and exhaust is
> a RV8 through the inner wings system with single pipe.
> Cam is Crower 50232
> Ignition is a recurved lucas 35DLM8

Entered into Dynomation.

> Haven't had it dynoed as the result from rolling roads seem to vary wildly,
> what would you think it should produce, I was aiming for 260+ BHP.

With my ported Buick 300 heads with Stage 1 Buick V6 valves, the prediction
is 279 HP.  With unported Buick 300 heads and standard valves, the prediction
is 232 HP.  Unported Buick 300 flow numbers but your valve size, the prediction
is 238 HP.  Adjusting the throat sizes gets 242 HP.  Your flow numbers would
be somewhere between these two, figure something between 240 and 280 HP,
so your 260 HP guess is in the ballpark. These use the dimensions of the
Performer Rover dual plane intake and an assumption that is "standard flow".
If the intake assumption is "high flow", expect 15 additional HP.  If you have
space for a plenum spacer, that would help the intake rating and increase the
peak power.  I'd need your actual cylinder flow numbers and min/max port sizes
to be more accurate.

Dan Jones

[DiDueColpi]

Hey Jim,

So here you go.
www.scribd.com/doc/40610101/The-High-Speed-Internal-Combustion-Engine-by-Sir-Harry-Ricardo

It just boggles my mind that one man could have such a firm understanding of all these principles so long ago.
90 years on, with countless hours spent by countless people, and no one person understands these principles any more completely than he did.

Cheers
Fred

[BlownMGB-V8]

Thanks Fred. He was impressive no doubt. Since that is the 2nd edition it will be interesting to see what he changed between that and the 5th edition. Some 40 odd years was bound to have made a difference.

JB

[castlesid]

Thanks Dan.

Yes forgot you were using those specially cast heads.

Kevin

[roverman]

Ok, Most will accept that 4 into 1 merge collectors, add power. What about a "gullet" in center of the 4 pipes,inside the collector ? Old skool therom of up to 10 hp gain for conventional 4 into 1 collectors,(2). roverman.

[California Kid]

To Dan Jones:

I sent you a PM in regard to this thread last night...  Hope you are still watching and can reply.

In the meantime, thank you again for all your valuable guidance!

Cheers,

Mark Griffin