group buy on Stahl headers ??

[rsporsche]

i spoke to Judy Stahl ... she says they will give a discount on orders for 3 to 5 and 6 to 10. i have asked what the discount is ... list is $1186, 3 to 5 is $990 and more than 6 is $810.

that's a great price, who else is in? we need 4 more if Stan is still in.

 

[Brian D]

Do all of the headers in the group buy have to be the same diameter tubing? I have something a little more serious than the original 3.0 going back in the Bav and I'd like 1 5/8 primaries. How long is this offer going to be good for?

Thanks for starting this out.

 

[Stan]

Carl Nelson like the 1 5/8" for the 3.5L engine
Would the price be the same?

 

[JFENG]

15/8 is the size

Carl Nelson like the 1 5/8" for the 3.5L engine
Would the price be the same?

What does SFDon recommend for a 3.5l m30b35?

 

[Stan]

you have to ask him

 

[rsporsche]

i have emailed Judy and asked if we can get different size tube diameters and still qualify for the discount. will post the reply when i hear back.

for those thinking of bigger diameters, korman recommends that if you have a schrick 304 cam + 45 dcoes to go bigger. but if you don't have a real fire breather ... this is one of those times when bigger isn't necessarily better. i have emailed korman to ask under what conditions that you would use the 1.5" and the 1.625". i will report back on the findings, i know they have built + dyno'd a lot of engines and have tested stahl headers. i also guess that the long tube header breathes better than the spaghetti design that ireland has. (that's a guess) ... yes ireland's is inexpensive. coupeking's design is similar to ireland's ... but its 1.5". he also will make a 1.625" (if you have a stroker, or a very hot m30.)

if you are thinking about this or interested, please drop me a line and what size you are thinking about.

 

[kwyjibo]

OOOooooohhh! Shiny metal thingeees.
Actually, I'm very interested, depending on the outcome of the sizing question (I'd go with the 1 5/8")... will keep an eye on this thread.
Thanks!

 

[rsporsche]

OOOooooohhh! Shiny metal thingeees.
Actually, I'm very interested, depending on the outcome of the sizing question (I'd go with the 1 5/8")... will keep an eye on this thread.
Thanks!

i presume you have a fire-breather? you might want to see the comments under the stahl header discussion in the general forum. a larger header will create more top-end power, if you have the cam and carbs to support it, at the expense of low-end torque. it doesn't matter to me, which you buy ... just want it to be worth your while and meet your expectations.

 

[rsporsche]

guys - i just got the word - we CAN mix sizes. 1 3/8", 1 1/2" or 1 5/8".

please read the article that Brian D posted the link to in the stahl headers general discussion forum. its worth the read, it also shows dyno results for comparative purposes - that bigger isn't always better. you need to look at the engine description - and the header descriptions ... then look at the rpm / power variations ... and then consider how you drive ... and where you want the power to be. in all practicality, consider how often do you drive for extended periods above 5000 rpm?

 

[Stan]

could be six are in?

rsporsche
stan
kwijibo
david
BFeng
BrianD

 

[TodB]

Besides the size choice, I'm curious to hear from those who plan to install what the plan is down steam of the headers. Are you going to tie into the existing exhaust system or do something else?

 

[Bert Poliakoff]

Correct me if I am wrong, but, Jere Stahl was known as the "king" of small diameter long tub headers. The belief on the E24 boards are 1 5/8"for an M30 engine

 

[rsporsche]

in regard to the downstream question, i am staying with stock for the time being. i like the idea of the unit that W+N sells - except i have a 3.5, and probably always will ... perhaps it will be changed to a b35 instead of a b34 ... or my head will get worked on to make my b34 more robust. there's always the coupeking piece. i will wait until i get a cam / headwork before i worry more about the exhaust. i will be going with either a schrick 284 or a paul burke 272 or 284 (not sure of the actual numbers) ... not the radical 300+ cams.

i know that Jere Stahl was king of the long tube header ... not sure about the small diameter thing. interesting, the articles also compared headers by ed as a long tube guru along with stahl. the article by ed was enlightening.

don't care too much what the thought on the e28 board is ... it depends on where you want to make power, and what you want the throttle response to be. for me, i want an increase in power below 4000rpm. so that's is smaller tube. if your goal is ultimate power at the top end - go with the 1.625. the biggest i would consider is 1.5, but i think i will be happiest with 1.375. that's what the articles that were posted led me to believe. that's what korman's people tell me. bigger is NOT necessarily better in this case. but its your money, your dreams, do what you want and what suits your goals.

cheers

 

[Mike Goble]

Performance Welding Racing Headers also has some good reading...

"[FONT=Arial, Helvetica, sans-serif]So being very general, a low horsepower 350 CID V8 engine making only 1.5 horsepower per CID ( that's 525 hp, 65 hp per cylinder ) may only require a primary tube size of 1 5/8"stepped to 1 ¾". This particular engine would only require a merged collector throat size of approximately 2 ¼" with a 3" outlet."

http://www.perfweldheaders.com/primary.html

"[/FONT][FONT=Arial, Helvetica, sans-serif]A properly sized header and merge collector is a critical component on your race car if you are trying to obtain maximum VE. The header and merge collector combination needs to be designed to pull the maximum allowable amount of air into the engine without over scavenging. This meaning use as small of a header tube and or merge collector throat as possible. Years ago the term over scavenging was less common then it is today. Today we are trying to pull as much air in the competition engine as possible and over time we are learning how to accomplish this feat. Most professional engine builders and header fabricators are trying to use a smaller header and a merge collector when allowed by the engine combination to increase acceleration on the race track. This in turn increases exhaust speed and helps scavenge the engine. The key to designing a header and merge collector combination is trying to pull as much air in and not lose much or any out to the exhaust on overlap, which is where the term over scavenging comes from. This is just another way of increasing VE, by packing the intake charge in the cylinder."

http://www.perfweldheaders.com/headerscavengetech.html


[/FONT]

 

[Stan]

ditto

I too have the b34

RE Paul Burke cam..."The best camshaft for a stock M30 B34 motor is Paul's N11 grind for $579.00. It is a single pattern cam with a 278 degree duration. This bumps rear wheel torque 35 ft/lbs and adds 20 rear wheel horsepower. It retains the same operational characteristics of the stock camshaft. A more aggressive cam would require higher compression ratio than your stock motor to perform properly"

For now I would run the headers into the stock exhaust system. A cam and different carburetos would come later.

 

[TodB]

For now I would run the headers into the stock exhaust system. A cam and different carburetos would come later.

So your theory is that you are going to get more power just by adding the headers or said another way, the headers will create better flow because you think your current exhaust system is holding the power back.

I added my headers (which I found used), Stahl 1.5s into a 2" collector, after I modded my B34 motor. The rest of the exhaust included an X pipe just beyond the headers, bypassed the cat, and then reduced a bit into the OEM dual pipe exhaust that had been "opened up" by Dinan years ago.

The result was that I lost a little bit of mid range low torque (noticeable) but its a bit happier on the upper end. It sounds a little different but not louder unless you get on it and even then its not loud - I'd call it sporty. Some of the noise difference may be because I bypassed the cat also.

I'd like to hear more from folks who have actually added the header and what their performance experiences were pre and post header install. Added to just a stock motor, I think you will be disappointed unless you drive around at 4K or above all the time and even then, the difference will be negligible.

 

[rsporsche]

Tod,

your experience is exactly why i am not going with a 1.5" or 1.625" header, unless you have an ultra-fire breather, the noticeable loss of low / mid range power is not what i want - even with an increase at the top end.

you should read the articles that Mike + Brian posted links to. a 500hp 350ci +/- v8 - using a 1 5/8". so lets break that down to about a 5.7 liter engine. so cut that down by 63% to get to a 3.5L w/ 315hp (we don't really have that much power, but this is a comparison) ... now extrapolate an approx. air volume size of the primary tube. 1.625" tube has 1.83 square inches of area, while a 1.375" tube has 1.28 square inches of area - a difference of 43% of volume. so ... why do you need that big of a primary tube?

(from headers by ed - the tube sizes were changed to make a more direct comparison to our situations)
keep in mind that, as the tube size increases, exhaust gas velocity INSIDE the tube at any given RPM decreases. choosing a 1.5" tube rather than 1.375" lowers the gas velocity in the header tube about 20.5%; Choosing a 1.625" tube rather than 1.375" lowers the gas velocity in the header tube about 43%.
These much lower gas velocities effectively take away the headers' ability to scavenge exhaust gases optimally - resulting in reduced bottom end and
mid-range performance and sometimes even reduced top end power as well!
While the above Tube Area Differences compares inside areas of various header and collector tube sizes, maintaining high gas velocities in the exhaust system is also important. (Think of the exhaust system as a secondary scavenging system located immediately behind the headers!). This is why many switching to or using 3" exhaust systems often complain about the poor bottom end and mid-range performance of their engines - the inside area difference between these two tube sizes can end up simply too big and the resultant much lower gas velocities inside these 3" systems actually ends up hurting performance in many situations!

 

[TodB]

Yep, get all that which is why I question the big excitement about headers in the first place especially for a street car that's near stock.

What I don't know, and there are competing opinions about it, is how restrictive the OEM exhaust system is. Jim Rowe sells hogged out exhaust manis for example that allegedly help. What about the size of the stock down pipes? Are those restrictive? And for those of us with B34 heads, we already know flow through it is not the best. So you might free up one thing and be restricted from another.

My end game was torque not so much HP and torque where you could use it and not just at the track. Frankly, I think you'll get more of that with a cam using the OEM exhaust manifolds and stock exhaust over just adding headers regardless of size. I'd go that route first. My opinion.

 

[Mike Goble]

One of the features of stock exhaust manifolds is the relatively neutral scavenging effect. The exhaust ports are separated by tubes only inches long, so the standing waves are quite high in frequency and relatively weak, giving you no torque peaks caused by scavenging waves. Adding length to the tubes by moving the primary junction 30+ inches away reduces the frequency of these waves and increases the intensity. This produces waves that are good and bad, appearing at the exhaust port in and out of phase. Generally the bad waves occur in the lower rpm ranges, presenting a positive pressure at the port, reducing scavenging and performance. As the rpm's increase, the waves present a negative pressure at the exhaust port, increasing scavenging and torque. With a well designed exhaust system this wave can be quite powerful, and during overlap can evacuate the cylinder very well. The CAFE Foundation has some very interesting pressure graphs in their report on aircraft exhaust systems:

http://cafefoundation.org/v2/pdf_cafe_reports/EPG PART IV.pdf

 

[rsporsche]

Yep, get all that which is why I question the big excitement about headers in the first place especially for a street car that's near stock.

What I don't know, and there are competing opinions about it, is how restrictive the OEM exhaust system is. Jim Rowe sells hogged out exhaust manis for example that allegedly help. What about the size of the stock down pipes? Are those restrictive? And for those of us with B34 heads, we already know flow through it is not the best. So you might free up one thing and be restricted from another.

My end game was torque not so much HP and torque where you could use it and not just at the track. Frankly, I think you'll get more of that with a cam using the OEM exhaust manifolds and stock exhaust over just adding headers regardless of size. I'd go that route first. My opinion.

Tod,

are you using carbs w/ the b34, or fuel injection? if the latter, how did that work with getting the L jet to work with the cam? i think the pipe is the pipe after everything is joined together - the longer that is, the more back pressure. the long tube reduces the length of the co-joined pipe and therefore reduces the back pressure to some degree. there is a decided difference with the bigger 3.5 manifolds than with the stock 3.0 manifolds - so jim rowe's hogged out manifolds work in that manner. the difference is, where are you creating the venturi? closer to the head, it congests the flow at the head ... move it away and that restriction is less of a problem. i think when you consider short + wide headers vs. long + narrow - you run into the same discussion ... then the collector becomes more of the topic.