To clear up comments from the peanut gallery yes I realize they will not perform as well as long tubes, and yes I did a search. (PS search button on this site is now useless)

NOW the question what kind of gains would I see with shorties on a 98 Z28? I know on later models 01-02 the manifolds flow better but from what I have read the manifolds on a 98 are worse. Has anyone put them on a 98-99? What kind of gains did you get? 10-20? What kind if y pipe are you using stocker/aftermarket?

 

Now im not usually part of the peanut gallery, but why would you want to use shorties? Cost? The way i figure, for as much of a pain in the *** it is to remove the old manifolds, why not just save up, and do it right the first time. I picked up a set up used pacesetters for 250 in real nice shape, and they worked great. Just my opinion. Other than that, i would think 10hp at the most with shorties. maybe 15 but that would be pushing it.

 

Need stainless regardless of which type of header; the wife and I may be moving to California(near LA) from what I hear emmissions is a pain in the *****.

 

yes, emissions are a bitch here. buy some LTs, keep your stockers and switch them out whenever you have to get smogged. the shorties are not worth the money. just remeber to keep your stockers or you'll be paying out the *** for smog "hook-ups".

 

I gained 8whp/8wtq with hooker shorty's and dropped .17
1/4 mile. They were easy to install and hooked right up to
my stock y pipe. I did go to mac mids though. It's worth the
trouble IMO If u have to worry about emissions. Lt's are the
way to go if u don't.

 

To actually answer your question I saw a post where a guy swapped his manifolds directly out for shorties and bolted up the stock exhaust and put down 10hp and 10tq more on the dyno. The gain for LTs is down low and the fact that most people open up the exhaust when they do headers.

 

Thanks for all the info guys pretty much spot on what I was looking for. Narrowed it down to either
LPP headers+y pipe with some high flow cats welded in(although price of ebay headers are tempting) or JBAs. How accesable are these smog hook ups? I mean inspection is no problem in NJ, but out in Cali if we go I know no one.

 

Why are longtube headers better than shorties considering they are of the same quality. It would seem to me there would be less pumping losses with shorty headers. What makes long tube headers better?

 

1989 Think about how air flows... if you push air threw a straight hole the air flow will be consistant and even, when you push air into winding bends and curves your air is being restricted or slowed down.. in the case of exhaust the longtube headers try to prevent the curving and bends as much as possible for a more even flow of air.. the shorties are are smaller and take up way less space so their are more bends ect in them.. although anything is better then stock.. IMO..

sorry to hear about you moving to a gay emmissions state man that blows.

 

2 words.....EXHAUST SCAVENGING.....

 

Thanks for the replies. First why would short tube headers have any more bends than long tube headers? I would think the opposite might true from what I have seen. I would think the shorter tubes would have less pumping losses with less frictional losses.

OK, exhaust scavenging. What is it about exhaust scavenging that gives the long tube headers and advantage over short tube headers?

 

It's not whether the air is restricted or not, it's how quickly the gases are pulled out of combustion chamber and out through the primaries to the collector. If the gases reach the collector at the same time from 2 cylinders they're forced to compress into the single hole on each bank, then to the y...thus a loss in efficiency. There are good reasons why "tuned" exhausts are quite a bit more expensive. My tuner swear's by 27'' length primaries with 1 3/4'' stepped to 1 7/8'' to a 3'' collector for a 346.

 

Lazylongboarder thanks for joining in on the discusion. You have come up with exhaust gas speed and tuning.

Let's take exhaust gas speed. If the short tube header has the correct diameter primary tube would not the exhaust gas speed be the same as for the correct size long tube header?


Tuning. What is the most important criteria for a header when "tuning".

1. Primary pipe length?
2. Primary pipe size?
3. Collector pipe diameter?
4. Collector pipe length.

A short tube header would have a shorter primary length but equal in the other categories. What effect would that have?

 

"If the short tube header has the correct diameter primary tube would not the exhaust gas speed be the same as for the correct size long tube header?"

Yes and no, notice i said "pulled out", there is a vacuum at your tail pipe, that's why exhaust leaks cost you power.

"Tuning. What is the most important criteria for a header when "tuning".

1. Primary pipe length?
2. Primary pipe size?
3. Collector pipe diameter?
4. Collector pipe length."



You couldn't use one criteria and there isn't 1 recipe for all motors.

Primary length should be equal and tuned to the power band of the motor...cam, intake...

Unfortunately i'm running Hooker 1 5/8'' shorty's due to no space. I have a conversion Porsche 911 LS1 with a G5X2 cam + PP 243's and it's always in the back of my head bugging me that there's way more power under the curve i COULD've had. I cut the 2 1/2'' flange off and had a local shop weld on a 3'' collector.
I'm running 3'' diameter true duals (not much, maybe 11'' of pipe between the collector and the 3 chamber flowmasters...damn loud, no space for cats).
It helps that the car is 2550 lbs.
Russell

 

Let me just cut to the chase. Larry Meaux of PipeMax fame and highly regarded head porter and engine builder has defined the most important elements in header design. I listed them above but in reverse order but here they are again. Let me say the collector is the most important piece.

1. Collector length is the most important dimension.
2. Collector diameter is the 2nd most important dimension.
3. Primary pipe diameter is the 3rd most important dimension.
4. Last and far down the list is the length of the primary pipe.

I have had discussions over on Speedtalk with Larry, Joe Sherman and Calvin Elston regarding exhaust. Here is the most recent reply from Calvin in a thread about "exhaust termination boxes" which also happens to pretty well sum things up regarding primary tube length. Here is a quote from that thread.


"Years ago I was instrumental in introducing "merged collectors" into Cup which is pretty much where they got started. When we reduced the "choke" in the final collector, we found we could shorten the tube lengths and not hurt bottom end power. There is still an incredible amount of confusion over this reality. The "choke" becomes instrumental in protecting torque at the bottom of the power curve not tube length, and power can increase because the primaries are shorter, less pumping loss (major increase), shorter tubes "tune" at higher rpm,(lesser importance). In fact in all out racing engines, the collector becomes the most important part of the system. If folks can think back to "log manifold lessons", the difference across the board is because of the lack of the collector, (never discussed). I have done tests with current 2.8-3.0hp/in engines with very short stubs for headers and do not give up any torque on the dyno, hello?.. "

Almost all my realities revolve around race engines and unrestricted systems at WOT. I do find however that the proper "choke" in the headers final collector still functions in the above regard and basically isolates the engine from the exhaust system "tuning" wise, but if you have a restrictive system, you will lose horsepower no matter what, eh?

I agree with MadBill in has last post but the operative word is "significant" and I would bet the main area of contention is the power at the top of the power curve. Last time I checked you don't need mufflers at Bonneville,

so... if you are pulling a 2000-2500rpm band, the motor will spend the least amount of time at the top of the curve and the most important single thing to do is build a good crossover setup, "Terminator Box", X-Pipe or a large H-Pipe. After that you are wasting time and money unless of course you just want to get that last 8hp @ 7200 rpm!
_________________
Calvin Elston
Elston Exhaust Inc.
Matthews, NC 28104
704-821-4494 "

According to Joe Sherman from what he has seen on his dyno long tube headers tend to favor rpms below 4500. Above 4500 things are equal and the shorty may in fact make more power higher in the rpm range.

So the bottom line is a well constructed set of short tube headers may in fact be better than long tube headers. So things are not always so in internet lore. The problem is does anyone really make a set of good shorty headers with the proper collector?

 

excellent info..thanks

 

The western forum is your friend when it come to these favors but please do not post what your looking for make it descrete. Eventually you'll get a PM. I know someone who know someone who know someone. Get it.

 

Seems like making a merge collector bolt-on (that
maybe just happened to look like a stock cat-shell
from the outside) is a marketing opportunity of
epic proportions.

Anybody wants to build it, you can use my idea
for free if you give me a prototype.

 

Jimmyblue you are getting on the right track. One just needs to get the dimensions correct. I work on ThirdGens and don't have the problem with the converter up close. I'm in the process of building a custom set of shorty headers based on the dimensions from PipeMax and using Exhaust Termination Boxes. I don't think I will be giving up a thing to the long tube headers.

 

ask around on the western forum. you should get a lot of replies to "good" smog shops.