Merge collectors

[Ed Wright]

Originally Posted by Alan Roehrich

Much as I like and respect Jere, I'm not at all convinced his opinions on steps and merge collectors are completely correct.

In fact, when I pressed Jere a little further, he admitted that step headers were worth some power. Ours are one step, 2" to 2-1/8". They were in fact quicker and faster than the Hooker 2-1/8" headers. Even when the Hookers, which were too big and too short, had a set of Mark's merge collectors on them. Later, after some testing and data crunching, Jere and I discussed a set of two step headers, 1-7/8" to 2" to 2-1/8", and a set of merge collectors. Development on that combination stopped before they were built.

Jere's main thoughts on stepped headers, and merge collectors, were for the most part along the lines that few would ever do what was necessary to see what he told me he felt were possible 2-3% gains. As such, he felt for 95% of his customers they were not worth the extra money. The truth is, Jere is probably right. As Billy said, and I agree, for the vast majority of racers, a basic set of single diameter headers with regular collectors, properly sized, will be all they can ever use. They will never do the development necessary to take advantage of anything else.

Now, the flip side of that is that 3% on a 650HP engine is almost 20HP. Well worth the upcharge Jere was asking for two step (three diameter) 4 into 1 headers.

I spoke at length with Jere's head fabricator, who actually runs the new business, and makes genuine Jere Stahl pattern headers. He told me that he would not make single diameter headers anymore, they would at least be one step, for both performance and ease of fabrication. Odds are, my next set will be built there, and they will be two step, or three diameter headers. They will get a set of merge collectors.

I've also talked to Larry Meaux (mostly by email and private message), who developed the PipeMax software that many of us use. Larry said that even some of the most well funded racers, even after seeing what the right size and lengths of primaries and collectors did for their expensive race engines would not spend much more time and money testing cams, and especially not on merge collectors. Larry has in fact expressed the same thing Jere, Billy and I have said. Most racers either cannot or will not do what is necessary to make the higher end headers and collectors work, and will see no gains. Larry has spent a couple of decades on the dyno and the track learning about this stuff, and then writing software to quantify it.

I've spoken with Calvin Elston many times, He is a very sharp individual, and a great fabricator who makes a top shelf product. They are absolute automotive artwork, no doubt. That said, his headers are more than twice what Jere was getting for his, and few people would make the effort and spend the money to see the gains they potentially have. A set of 4-2-1 headers requires even more camshaft development than a set of step headers with merge collectors. Calvin quoted me over $3500 for a set 4-5 years ago, and I know it might take 3-4 cams to take full advantage of them. At a bare minimum, that's $1400-$1600 worth of cams, and 2-3 days ($1800) worth of dyno time. For the vast majority of racers, that's just plain out of reach, and out of the question.

Jere told me mine might like a 2" step on mine.
No more int/ex split than my cam has ( 4 @ .050"), and I backed the ex lash way off, still nothing. Some run single pattern cams, or "reverse split" cams to make merge collectors work? My heads do have very good exhaust ports. Best I have seen for an SS LT1. I have seen, owned and flowed LT1 heads from a few shops. Was no huge difference between the two most popular. (Have not seen Gulius heads) I have tested all five of my cams. I have bigger & wider, smaller & closer, more split, and the one I keep going back to. Done fuel loops & timing loops on the dyno. So far found nothing. May just be too stinking dumb. Likely so.
Got two more races till I'm done anyway. Through looking for more. Trying to watch the average for the other guys these last two.

[dmir55]

We set a national record with a set of Hedman step headers on 302 ford. The pipes were 1 1/2 to 1 5/8 step. You can't use there collectors as they are no good for a race car. The collectors we used were made by Headers by ED of Minneapolis MN. He doesn't use a merge type of collector but uses his own style that seems to work just as well. And it is a lot easier to make. Ed no longer makes complete pieces, but has every thing you need to make your own. Now day there is a lot of satisfaction in doing your own stuff. Eds collectors when we finished them were 2 3/8 minor od 2 1/2 major od. One last thing. I talked at length with the late great Jack Davis of Hooker and Davis headers about design. Of all the information he shared with me, one thing he said was about testing. He felt headers had to be tested at the track not on a dyno. Hope this helps and happy motoring.

[Exhausted]

A friend told me that this thread was getting some attention so I thought I might put in my 2 cents.

IMO, I have never seen a exhaust port that was smaller than it needed to be.
If you can change say header tube size or step length, or no-step to two step, or collector diameter or length or 421 to 4into1, and not see any difference your motor is not sensitive to what kind of a header it has on it. Another way of saying that is your header is not working to add anything to the way the engine runs, is it?

It is certainly possible that whether you buy headers that come in a box or made for you custom, if the above is the case, it is not simply the fault of the header, ok?

If you do not want to change things in the motor so you can gain the extra power available from the exhaust system, then keep bracket racing and praying you don't have to run heads up with someone who does.

[Billy Nees]

Originally Posted by Exhausted

It is certainly possible that whether you buy headers that come in a box or made for you custom, if the above is the case, it is not simply the fault of the header, ok?

If you do not want to change things in the motor so you can gain the extra power available from the exhaust system, then keep bracket racing and praying you don't have to run heads up with someone who does.

Although I won't disagree one bit with what you're saying, I think that you'll find that a good number(I won't say majority) of Stock and SS Racers today are buying an "engine package" because of the lack of time they have to test these days. I don't believe that they have gotten lazy or stupid. They have their stuff dynoed and put it in the car for lack of time. Now, more than ever, they're counting on us to have done the work.

[Exhausted]

Originally Posted by Billy Nees

Although I won't disagree one bit with what you're saying, I think that you'll find that a good number(I won't say majority) of Stock and SS Racers today are buying an "engine package" because of the lack of time they have to test these days. I don't believe that they have gotten lazy or stupid. They have their stuff dynoed and put it in the car for lack of time. Now, more than ever, they're counting on us to have done the work.

Ya know your absolutely right.

Every once in a while I will get a spec on how a builder wants a header for his engine. All I have to do is ask a few questions and they will admit they really have no idea outside of their dyno header.

So I am asked to figure it out for him or "whatever" I think. So now I am responsible for making his engine run better. Seems most racers know there is something there but few answers...

[Alan Roehrich]

Originally Posted by Billy Nees

Although I won't disagree one bit with what you're saying, I think that you'll find that a good number(I won't say majority) of Stock and SS Racers today are buying an "engine package" because of the lack of time they have to test these days. I don't believe that they have gotten lazy or stupid. They have their stuff dynoed and put it in the car for lack of time. Now, more than ever, they're counting on us to have done the work.

Yeah, Billy, I agree. Given the amount of time it takes to actually go racing on a reasonably regular basis, and the amount of money required, it is no surprise that so many of the people who actually can afford to race have little or no time to spend on testing. Most of them don't have the money, either.

[Alan Nyhus]

Originally Posted by Exhausted

A friend told me that this thread was getting some attention so I thought I might put in my 2 cents.

IMO, I have never seen a exhaust port that was smaller than it needed to be.
If you can change say header tube size or step length, or no-step to two step, or collector diameter or length or 421 to 4into1, and not see any difference your motor is not sensitive to what kind of a header it has on it. Another way of saying that is your header is not working to add anything to the way the engine runs, is it?

It is certainly possible that whether you buy headers that come in a box or made for you custom, if the above is the case, it is not simply the fault of the header, ok?

If you do not want to change things in the motor so you can gain the extra power available from the exhaust system, then keep bracket racing and praying you don't have to run heads up with someone who does.

Calvin, a couple of questions. I've got a set of your 4-2-1 headers on my 327/275 stocker motor and want to spend some time on the dyno this winter doing some camshaft work.

- Is backing up the exhaust duration by 4 degrees is a good place to start. Your thoughts?

- If an engine really is over scavenging due to the header design, what are some of the things to look for on the dyno or the track?

Thanks for joining in. -Al

[dmir55]

I tied a set of headers together on Line's dyno and picked up five foot pounds of torque with no other changes. A two into one set up. Back to Jack Davis, he told me he made a set of two into one collectors for a NASCAR team. When they ran their car at Michigan the car was so much faster that Nascar banned the two into one set up. Hence they went to the "X" pipe. All we are trying to do is to keep fifteen pounds of atmospheric pressure from running back up the pipes. The fewer openings you have for the exhaust pulses to exit the better headers and collectors will work. Just think of how small that exhaust pulse is at six to eight thousand or more r.p.m.

[Billy Nees]

Originally Posted by dmir55

Just think of how small that exhaust pulse is at six to eight thousand or more r.p.m.

I'm not understanding what you're trying to say. If X cfm of air and fuel is going in then X cfm of air and fuel must be coming out. The exhaust pulse may be getting faster(and stronger) but it's not getting smaller!

[Ed Wright]

So, we are supposed to buy the trick of the week header, then build an engine combo around that?