Merge collectors

[Gary Smith]

Originally Posted by Darrin Christen

Interesting read. What would be the tell tale signs that a engine may be over scavenging? Anything noticeable in the tune up that would be an indicator of this condition?

The topic of lean rear cylinders is what drove my question. We haven't even run the motor yet, not looking for gains, just don't want to go backwards. Headers are nothing special...straight 2" primaries about 40" length. Last year we made some fixes (new fuel pump) and added 13" to the collectors and picked up 2 tenths. I suspect much was from the exhaust. But everything is bigger now, with lots of other changes with same basic induction. We'll probably put straight 4" collectors on to start. FYI this is not for my stocker. It's a bracket motor built with a lot of S/S technology.

[Ed Wright]

Mine is very responsive to timing changes, likes to run richer than some others. I talked to Jere Stahl quite a while, twice when I ordered mine. Always used his stuff on my old "Jr Stockers". Tried to order a set from him when I make it a race car. At that time they had no jig for the LT1 Camaro/Firebird. Whoever I talked to then told me they could build a set for me if I wanted to bring my car there. York, PA is a long drive from Oklahoma. Talking to Bobby Warren a couple years later, I learned he had taken his there to have a set built, so they now had a jig.
Jere had me fax him my dyno data (both steped & straight 1 7/8" headers) and engine specs. I told him I had tried my friend's merge collectors at the track, and what I found.
Jere told me he saw no way it would like the 1 3/4" to 1 7/8" steps, he said the non-step 1 7/8" should be right, and it MAY like 1 7/8" to 2" steps. He didn't see it liking merge collectors, either.
I tried backing the ex lash off with both styles collectors, didn't like it. I have not tried less than 4 degree int/ex duration split @.050". Less than 3 at .200" lift. Tried wider lobe centers, even with more gear. Dyno liked it, short times suffered. Back half about the same. May need a 7" converter with that cam? Don't know. The normal cam did not like one at all.

[HawkBrosMav]

Quick question, and I know this may be more complicated than this, but as a generic rule of thumb would you need a better scavenging header setup for a cam with more or less overlap?

assume generally the same cam specs for a cam with 80 degrees overlap compared to one with say 70 degrees. only change being lobe separation. you you need more scavenging going to the smaller overlap to be as efficient?

[chassis1]

Originally Posted by Ed Wright

Mine is very responsive to timing changes, likes to run richer than some others. I talked to Jere Stahl quite a while, twice when I ordered mine. Always used his stuff on my old "Jr Stockers". Tried to order a set from him when I make it a race car. At that time they had no jig for the LT1 Camaro/Firebird. Whoever I talked to then told me they could build a set for me if I wanted to bring my car there. York, PA is a long drive from Oklahoma. Talking to Bobby Warren a couple years later, I learned he had taken his there to have a set built, so they now had a jig.
Jere had me fax him my dyno data (both steped & straight 1 7/8" headers) and engine specs. I told him I had tried my friend's merge collectors at the track, and what I found.
Jere told me he saw no way it would like the 1 3/4" to 1 7/8" steps, he said the non-step 1 7/8" should be right, and it MAY like 1 7/8" to 2" steps. He didn't see it liking merge collectors, either.
I tried backing the ex lash off with both styles collectors, didn't like it. I have not tried less than 4 degree int/ex duration split @.050". Less than 3 at .200" lift. Tried wider lobe centers, even with more gear. Dyno liked it, short times suffered. Back half about the same. May need a 7" converter with that cam? Don't know. The normal cam did not like one at all.

If you measure the port on the LT1 head, last time I checked, 1 5/8 tube covered the port. The reason you see no change is the header isnt even working at this point....13/4 and 1 7/8 are way too big... proven many times over... you guys are not talking to Calvin Elston obviously....

my proven $.02... race track and dyno

[Ed Wright]

Originally Posted by chassis1

If you measure the port on the LT1 head, last time I checked, 1 5/8 tube covered the port. The reason you see no change is the header isnt even working at this point....13/4 and 1 7/8 are way too big... proven many times over... you guys are not talking to Calvin Elston obviously....

my proven $.02... race track and dyno

Two header gurus told me steps are what I need, one even talking three steps, (with a 1 5/8" first step) but THE master header builder, (IMHO), Jere Stahl, (knew Jere from Jr Stocker days. Happily he remembered me) told me what it should like after I sent him all the data he asked for, and it agreed what I had found on Patterson's dyno, and (since we don't race Dynos) A-B-A testing during a track rental test session.
More to header fabrication & layout than I realized. My 1 7/8" Stahl headers (one of the very last set they built) are a full MPH faster than my old 1 7/8" Hedman Hustlers, which were on the dyno. And, I can get all my spark plugs out. Haven't been back on the dyno with the Stahl headers.
I just went back and looked, I typed the correct numbers in: 1 3/4" to 1 7/8". I cut a pattern, like cutting a gasket, and sent it to Jere, he had his guys water jet (I think) cut a set of flanges for the 1 3/4" tubes, for my Stahl bolt pattern on my aluminum adaptor plates. So they were centered correctly.
Elston is one I have not talked to.
Btw, Sir, who are you?

[chassis1]

http://www.speedtalk.com/forum/viewtopic.php?p=75639

start reading here. lots to learn about the correct header before any of you should consider merge collectors....every winter there is a new thread it and it dies the same way.... this winter, lets start with Calvin and maybe we can convince him to swing in the forum and educate people....

[Ed Wright]

I tested what Jere Stahl recommended. It was faster. Good enough for me.
Thanks.

[Pvt Parts]

Originally Posted by Ed Wright

I tested what Jere Stahl recommended. It was faster. Good enough for me.
Thanks.

I went the fastest in B/A and C/A with merge collectors from the same guy that was building them for Glidden. David ran them as well.

[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.