Headers
 

There seem to be a wide range of headers available and I always find it difficult to make a decision on what to buy.

The basic RSR style are similar to the European Racing Header and the flat collector seems to help with ground clearance.

The OBX and many of the other headers now offered have triangular merges which are an issue due to Omega Spring clearance on SCs

The RaryL8 look interesting and the Patrick Motorsport Headers look great but at $3200 seem a bit pricey.

Has anyone carefully evaluated the differences and which work best?

As you know parts like headers are a culmination of compromises based on space, cost, usage etc.

w/o cams having a decent amount of overlap and w/ muffled systems about all you are looking for is decent flow, hopefully w/ minimal turbulence.

w/ happy cams and unmuffled the benefits of details like merge collectors and pipe sizing/geometry become much more important.

You'll have to look at the design features and cost wrt the intended application.

SSI are a fine design for up thru 3 liters but become increasingly compromised as displacement and revs go up, they can be improved by replacing the splayed collector w/ a properly designed rotating merge collector, but if the system is muffled benefits decrease, same for cam specs, less overlap implies a decreased benefit for detail improvements that may be expensive in terms of money and/or packaging.

The Patrick headers appear to be an excellent well thought out design using the best ideas, but if muffled will lose a lot of their benefit, w/o heat it is a great race setup for unmuffled applications.

the 3 into 1 headers tend to be most effective over a fairly narrow range of rpm, you can spread out the power band by using a tri-Y(3-2-1) design. When properly implemented these produce a power band that isn't quite as high but is far broader than the 3-1 design, muffler don't affect these systems quite as mush either.

the OBX are cheap flow ok but suffer from a poor collector design, local shops improve their performance by grafting Burns rotating collectors in place of the stock ones, again benefits are dependent on cam and muffler used.

Rarely also appear to flow well enough and on a muffled system the effect of the collector design is going to be minimized anyway.

One of the biggest variables that is easily controlled is pipe size and geometry, you want to minimize the radius of the bends, equalize(w/i a fairly broad range) length, use a reasonably efficient(non turbulent) collector and transitions and size the pipe for the maximum volume of gas flow that it will regularly see.

Looks like Patrick now sells a set of B&B 1 5/8" headers with heater boxes and '65-'74 outlet flanges. Not cheap at $2300, but one of the few options if you want larger primaries, heat, and normal muffler options.

Bill you didn't mention George's headers and Bursch.....

Bill,

Thanks, we have an on-going problem with a range of cars.

Noise limits at most race tracks are now 105dBA which is measured at 3/4 of maximum rpm.

The noise is measured 0.5 metres from the end of the tail pipe at a 45deg angle with the meter being between 0.5 an 1.0 metres above the ground.

The background noise at the test location must be at least 10dBA lower than the measured value.

If there are two tail pipes both are measured and the highest reading used.

Some trackdays are now limiting noise to 100dBA as the amount of 'noisy days' that circuits can be used is being constantly reduced.

Most of our interest would be 3.0 and 3.2 litre cars with around 260BHP typically with GE60 or similar cams.

From your comments it seems as if most systems will be reasonable and that there may not be a be gain due to the level of silencing.

I have some good merge collectors that we made a couple of years ago so I guess we will try the cheap solution fisrt and then change the merge collectors and see what happens.

I have custom(964 heat in/911 heat out) B&B 1 3/4" on my C3 mit 3.6 motor , Nothing really special about them, they flow well enough for 3.8 w/ SS cams to 7k, have a rotation collector, are good quality ss and have heat. The weakest point is the heat, but weak heat is better than no heat for my purposes.

Again w/ stock late cams w/ little overlap and w/ muffler that's all you need.

Both are mild steel copies of older 911 systems, I'm not that familiar w/ either so don't know the design specifics, seems to me that they are a mild steel version of SSI w/o heat.

The thing that always turned me off from them was the material used, mild steel rusts too quickly for my taste and budget. It is also dangerous if heat is implemented. The original 911 headers were mild steel and everyone ran w/ CO detectors in the cabins, the first improvement was SS tubes w/ mild steel heater boxes, then finally all SS but the heater boxes were designed to rust through before the tubes.

GE60 have decent overlap and can surely benefit from the resonance effects of tuned headers, but again once a muffler is hooked up the benefits are greatly diminished. As you say try the simpler cheaper solutions first.

My C3 was retired from track use primarily due to similar noise restrictions, my stock exhaust( except for no cat) barely gets by on most days, stock late GT3s can have issues.

Don't forget that noise also comes from the intake, I had to tape up my Motorsound airbox to pass. Similar steps may help others to get by.

I had 1.75" B&Bs on my 3.2 for a while and it ran and made good power well also, but I'm talking about these:
911 Exhaust Manifold Headers Heat Exchanger Set - (Early Heat Exchanger SSI Style to Dual Inlet Muffler) By Patrick Motorsports Porsche & Mid Engine Performance Specialists
The advantage being the wide variety of street and race mufflers available off the shelf.

I'm curious if these still need the B&B S-hose replacement.

I had never seen those, but they look like a great solution for 3.2-3.4 maybe even mild 3.6 that want to be able to use stock mufflers.

The biggest drawback of the B&B is the proprietary spacing of L/R banks.

Here's a set of factory SC/RS headers

http://forums.pelicanparts.com/uploa...1441910707.jpg

and a pic from the SC/RS manual, these were good for 280hp w/ RSR cams and muffled

http://forums.pelicanparts.com/uploa...1441910786.jpg

lastly an interesting but antique design from the 906/910, the best feature here is the long cone stingers, a short reverse cone could be added for wider torque power band. Noisy though

http://forums.pelicanparts.com/uploa...1441911162.jpg

These are Bursch 1 5/8 on an 87 with hydraulic clutch. Holding up quite well after 15k miles. Steel but very reasonably priced.
Will the top tube interfere with the Omega?

http://forums.pelicanparts.com/uploa...1441915680.jpg

http://forums.pelicanparts.com/uploa...1441915593.jpg

I am eagerly awaiting some RarelyL8 Headers w/heat and an M&K 2-1 exhaust. I chose them on their reputation on build quality and power for a street car. Cannot wait.

I have had many permutations of headers and exhaust on my cars, and I even have a dyno I can use.. however, I can never seem to control the variables... I change to many things at once....but...

This may not be germaine to the the discussion... its the results of of a shop in England who tested a number of different mufflers on the same engine... and they posted some dB info as well....

http://forums.pelicanparts.com/uploa...1441929884.jpg


Comparison of M&K vs Georges ( European Racing)..... on my recently refinished spruce floors...

http://forums.pelicanparts.com/uploa...1441930159.jpg


http://forums.pelicanparts.com/uploa...1441930174.jpg

underside of my #1850 911 with the LRP package....


http://forums.pelicanparts.com/uploa...1441930052.jpg

One of the problems with Rarlyl8's headers (at least for my 90/10 street track car) is the short primaries that optimize high end HP over low end torque. Brian has told me as much himself. He was testing a longer primary version but haven't heard back in about a year and a half.

For my own uses I need heat and torque, which leaves me with stock or SSIs. But I'm having a hard time putting 1 1/2" primaries on my 3.2.

Have always looked at B&B but didn't want to mess with the proprietary mufflers. Patrick's new option is intriguing.

Anyone (Bill?) want to comment on B&B headers and mid range torque? Would be looking at the 1 5/8".

I have B&B 1 5/8 headers into GT3 muffler, with straight pipe option.
It all came together power wise after a Steve Wong chip for my set up.

http://forums.pelicanparts.com/uploa...1442257882.jpg
http://forums.pelicanparts.com/uploa...1442257977.jpg
http://forums.pelicanparts.com/uploa...1442258177.jpg

yep, George's , Bursch and B&B have the long primaries.
Here is a clip of the Bursch + M&K ste up at Sebring during some track turing, they start to sing at 5500!

https://youtu.be/3KiPOUTGvdk

for the rev range that stock 911s work in, primaries ~31" work well.

but again w/ stock smog cams w/ little to no overlap timing it makes little difference, for these cams all you can go for is adequate non turbulent flow.

The resonance effects that 31" tubes can capitalize on depend on both the intake and exhaust valve being off their seats at the same time, this overlap allows the acoustic resonance in the tubes to place a low pressure region around the exhaust valve at ~ 6700rpm+/-, this low pressure regions sucks additional fuel/air mix into the combustion chamber super charging the motor in a limited rev range. There is this good resonance and there is also a bad resonance @ ~2k rpm which does the opposite

additionally mufflers usually mute the resonance effect greatly, The resonance is highly dependent on pipe length and width and the transitions and terminations. Each has an effect on the systems performance. But again all depend on overlap timing.

So are "we" saying the RarelyL8 headers would perform noticeably worse than B&B, or Bursch, or George's on a typical "sweet street" 3.2? Something like a stock US or Euro compression car with a K&N type filter, open airbox top, Steve Wong chip (91 or 93 octane), with headers/exhaust?

I would guess that in a street car, driven at "fun street" speeds we would not be able to tell the difference. Now maybe at a track, pushing 9/10ths AND being a very god driver we might feel the supposed better top end of the RarelyL8's vs the other's supposed better mid-range punch....since that is what it seems people are saying would be the case. Am I wrong?

Duc -- I'd suggest discussing this directly with RarelyL8 -- consensus DOES seem to be that undersizing exhaust a bit on a stock 3.2 (i.e. running SSIs) will boost low/midrange grunt at the expense of ultimate (and high end) power (i.e. the back pressure helps in "sweet street" situations at the expense of dyno #s). Would seem that the combination of short primaries and generously sized exhaust pipes would increase exhaust efficiency and provide high rev/ultimate power benefits at the possible expense of low-end "grunt"