Whats the logical method in pairing up cylinders? I want to use "Y-pipes" and pair up two cylinders at a time, eventually ending in one pipe. Is it just a matter of matching up cylinders so the pulses are equally spaced?
Thanks,
Jan
Across from one another on the distributor. 1-6, 2-5, 3-4 but you can't "pair up" and start with 6. Make or find a 3 to one merge header. Check out this site:
http://www.coneeng.com/collector_components.html
These guys could answer your questions possibly & maybe you could get ideas of making parts like them.
Top notch stuff but $$$$$
http://www.burnsstainless.com/MBHD
I did some searches and found some examples of I6 headers. It looks like the first three, and last three cylinders are grouped, and then Y together, like this example from ClassicInlines.
3 lots of 2 to 1 with a 3 to 1 collector at the end is what was recommended to me by a builder down under. Check out
http://www.mandrel-bends.com as well for tubing. This is also a very technical book that will help with header design.
http://www.amazon.com/Scientific-Exhaust-Systems-Engineering-Performance/dp/0837603099 There are cheaper sources out there, I paid $13 shipped for my copy.
Smith has some interesting theory, but there are no dimensions and no formulas - it's not a "how to".
I can save you $13.00: join #1-2-3 and #4-5-6, and don't merge them.
join #1-2-3 and #4-5-6, and don't merge them.
That's probably what I will do.
Here is a Fairchild Ranger I6 airplane engine, and thats what they did too.
That's a coincidence. Also note that the outlet is biased to one cylinder, and even the discharge angles do not match.
The thing about A/C engines,the exhaust is not always made for best performance,a lot has to do how to make it fit in a small enclosed engine cowling/s,some,engines have just straight pipe,not optimal always.
Most engines turn low RPM & therefore I think most typicle engine exhausts are designed for peak torque .
At least thats my take on them,they (the exhaust systems) do not look very well designed. I have been working on planes since 1988 & most look like crap,especialy the lower cost airplanes ,which would be 30,000-70,000 range & very old I might add.
MBHD
Most engines turn low RPM
I think that's an important factor - they can't fit any tuned length into a cowling, and the next best thing is reduce the weight and make it simple.
Some of the small aircraft enthusiasts do take exhaust system design fairly seriously. Here are some links to some interesting
reports. These are for a four cylinder engine, however.
looking for info on header size and jet size 302 gmc 5 97 stromberg on howard manifold also need linkage thanks gary 67vett@sbcglobal.net
Primary size: large enough ID to cover the port shape. The #1 & 6 cylinders can be round (1-3/4"?), the siamese #2-3 and 4-5 may need a bigger round primary (1-7/8"? 2"?) to be flattened a bit to match the port rectangle on its longest dimension (the diagonal).
A tuned length is only going to work better than a simple independent system if the overlap triangle area is big enough - but I have no idea what that is for this motor, perhaps 75°?
Primary length: the Bell formula is a useful start:
850 × (XO point + 180°) ÷ RPM, minus the exhaust port length from the valve seat to the flange in inches.
Example: exhaust opens 70° BBDC; add 180 = 250; times 850 = 212,500; divide by 5,000 RPM = 42.5"; minus 3" port = 39.5" flange to end.
Join 1 & 2-3, and 4-5 & 6 separately.
thank you looking for some stainless steel flanges ill give you some info on the moter see what you think 302 gmc .060 over ported head 2.02 in 1.60 ex cam is duration 268 0.050 230 lobe center 107 io btdc 8 ec atdc 8 ic abdc 42 eo bbdc42 lash 0.18 5 97 strombergs on howard manifold ign is a magneto id like to run 1.3/4 1-6 2.0 2 3 4 5 id like to use two merge collectors and balance tube let me know what you think thanks gary
Need the XO at nominal or lash, not .050".
not sure what you mean gary
Need the actual exhaust opening point in degrees, not the .050" point.
intake opens btdc 8 intake closes abdc 42 exh closes atdc 8 exh open bbdc 42 and thats checked at .050 lift lobe center 107 running duration 268 valve lift 450 0.050 230 valve lash .018 i hope this helps thanks gary
Yes, I read it the first time.
A perfect exhaust system would have the exhaust from each cylinder scavenge the next cylinder in the firing order. However, unless the exhaust system is designed correctly the pressure pulses in the exhaust system are higher than the intake system and the exhaust gases flow back into the intake. Sort of like a built-in EGR.
One way to overcome this is to have short, stubby "zoomie" type headers like most of the smaller aircraft have. It isn't the best system but it's cheap, fits the airframe and isn't too bad power wise.
Ron
Here is a link to see an
example of how to do headers for a six with siamesed ports. According to JD: Designed by Burns Stainless. Work done by one of the guys they recommended. Picture was taken a few years ago prior to putting the engine back in the roadster in 2007 for Bonneville and El Mirage.
Thanx Hoyt.The megaphone end is hard to keep polished...The front wheel throws a lot of salt.
One of the nicest compliments I recieved on the header was from Mike Kirby. When asked by a fellow Inliner at one of the So Cal Inliner get togethers where I showed the roadster what he could do for improving his his performance he said, "When your done on the inside you do what JD did on the outside" Ill never forget it.
I know this thread is old, I had to dig for it, but I have to ask:
Most say merge #'s1,2,&3, and #'s4,5,&6. that's pretty much been settled, and Don't merge them further ie: keep dual exhaust. But does it help to install an "X"or"H" pipe? or keep them separate?
Specifically on my blown 292 I'm building. (2"tubes into 3.5"collectors.)
IIRC, Clifford used to print in there catalogs that the exhaust would be really loud if you did not have a X-over pipe or make a "Y" pipe into a single system?,louder than a typicle V-8 engine when running dual exhaust?
At least I thought thats what they used to say?
Personnally, I would run a X-over pipe just so it would not be too loud, & smooth out the idle,,,if that's a concern?
MBHD
I'm not sure about the noise level, but a cross-over is generally quieter.
However: the pipes should be completely separated for maximum power.
I agree: all supercharged V8 engines should have crossovers.
A V-8 with dual exhausts and a straight 6 with 1-2-3 and 4-5-6 connected duals are two entirely different animals. The six is very even in it's firing. The V-8 (unless you have a 180 crank) is not. By adding a cross over pipe to the V-8 you allow the firing order to fill in and become smooth. You can see this on the V-8 by looking at the distributor cap and noting the firing order, 1 5 4 2 6 3 7 8 with 1-2-3-4 being on one side and 5-6-7-8 on the other. Our sixes make more power when a good system goes into a single pipe, like JD's a couple of posts back but we like the sound of split pipes a lot better for the street.
It would be interseting on testing a car on a chassis dyno or some track time to see the actual difference.
MBHD
The link you posted had dyno tests included and it definitely showed an increase in power. This has been proven for years on V-8's. The Bonneville salt flats have been called the great white dyno and the ultimate track. JD's roadster is the fastest ever in it's class and has been since Noah first sold him the aux 302 Jimmy from the Ark. I personally feel the reason racing sixes develop more power through a single exhaust is because there are fewer pulses and that allows them to help scavenge each other. Maybe Tom Lowe can do this in a future dyno test. I doubt if it makes any real difference on a street car.
Are you saying JD's roaster had a x-over pipe before & tested that also & was slower?
If not ,that does not prove much,,,if you know what I am getting at.
Maybe JD's roadster can have an x-over pipe installed next year & see the difference?
I am not saying to run a single exhaust system,just install a x-over pipe.
MBHD
I really don't know what to say.
I am not picking on you Armond.
I am just saying it would be interesting to see a run back to back on a street car,chassis dyno,track,or Bonneville.
I really don't know what to say.
The way my system is made and installed the double merge system is best and if you look at the one picture of it you will see it's not practicle to install any other pipe which could be called an X-over. The combo is in the merge megaphone which is where the next HP will come
Last week we were able to reach a goal I set for myself 29 years ago of reaching 170 MPH at Bonneville with a carburated stock head GMC. I was able to run 171+ in a qualifying run. Our return run was slowed by a broken rocker shaft but I was still able to average 168.8. There is still more so I'm hopefully not done yet.
Burns was very instrumental in the designing of many NASCAR teams engines in the past that that's why their shop was chosen. You go with a winner even if you are pushing a 32 grille shell with an obsolete 7 port engine.............JD