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Discussion Starter #1
How much benefit is there to a merge collector vs a std. There 5 to 10 times the $ of a regular collector, are they "that" awesome. I assume all your primarys need to be the "correct" length to take advantage of them. If all your primarys were the same length would that be considered perfect?? As far a std collectors go would a 19 or 20" collector make a little more than say a 14" collector, or wouldn't there be enough of a difference to worry about. I was just curious if there was an "ideal" length for those. Oh btw when it comes to slip on collectors what the best way to keep them fuggers on.lol
 

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steelcomp was here
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How much benefit is there to a merge collector vs a std. There 5 to 10 times the $ of a regular collector, are they "that" awesome. I assume all your primarys need to be the "correct" length to take advantage of them. If all your primarys were the same length would that be considered perfect?? As far a std collectors go would a 19 or 20" collector make a little more than say a 14" collector, or wouldn't there be enough of a difference to worry about. I was just curious if there was an "ideal" length for those. Oh btw when it comes to slip on collectors what the best way to keep them fuggers on.lol
Each application is going to be different , but mostly depends on rpm range and power. Jet boats tend to run better with a longer collector. Merge collectors are going to benefit in high power apps where you're looking for max performance, but in most moderate builds, you won't "feel" the difference.
Most standard off the shelf jet boat headers with straight collectors work real well.
Slip on collectors need welded tabs and bolts.
 

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There's alot to header science, more than one would think. I was talking with Domonic from Dominator headers this morning about some different aspects of header constuction. There are general rules of thumb though, example longer smaller diameter tubes on both primary and collector will favor lower rpm torque whearas larger dia. shorter tubes will make more top end h.p. For a high rpm drag motor I would want the 14" collectors, if I had a motor that didn't see much over 6k rpm pulling an occasional skier or tuber, I would want the 19" to 20"er's. Agreeing with Steel (wow did that come out of my mouth!!:)) You probably wont have any noticable improvement with the merge collector. In a pro stock type application where they are at nearly 3 h.p. per cu inch Im sure it is very noticable to them. Their headers are as finely tuned as can be. For a lake guy or bracket racer, not as crucial. One thing I don't like about slip-on's is that you will usually get some exhaust gases backing out from the joints dirtying up the headers. F1~
 

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How much benefit is there to a merge collector vs a std. There 5 to 10 times the $ of a regular collector, are they "that" awesome. I assume all your primarys need to be the "correct" length to take advantage of them. If all your primarys were the same length would that be considered perfect?? As far a std collectors go would a 19 or 20" collector make a little more than say a 14" collector, or wouldn't there be enough of a difference to worry about. I was just curious if there was an "ideal" length for those. Oh btw when it comes to slip on collectors what the best way to keep them fuggers on.lol
They cost the $ because of the labor involved to produce one. A standard collector is a pretty basic/simple design comparatively.
(pic courtesy of Burns Stainless)

you look at the picture and tell me they're not "that awesome", however as stated above they have they place. I've been told they are a little harder to tune, and i think they typically have a smaller outlet than a standard collector(for the same app).
 

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Discussion Starter #6
Thanks for all the answers... The collector that met an untimely death yesterday was 19" long, the dynatech and the others I've been looking at appear to be closer to 14". I think the 14" wouldn't look as good, sounds like the longer ones will perform a little better also. I probably shouldn't spend the money on these junkyard headers, but I kinda dig the way they look. As far as mounting them I know the way Steel said(tabs and bolts) is how most/all I've seen are done. Dynatech have a collector u tab kit part # 329-60-00320(to attach the collectors) , for the life of me I can't figure out how they would work. Anyways, thanks again...
 

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Cantard
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Are you trying to say my collector wouldn't be lying at the bottom of utah lake if I'd have used bolts:)hammers lol. Btw those would look better with longer collectors.:p
How long do you want!! I got 4-5 sets of these bastards.:D
 

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Discussion Starter #14
And yes...it would still be on your boat.:)hand
Too funny...yeah rub it in.lol Seriously, if you have 5 sets, lets make a deal. The tubes on the ones I have are sooo thin, I know I couldn't weld tabs to em, (not saying it couldn't be done).
 

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Cantard
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Too funny...yeah rub it in.lol Seriously, if you have 5 sets, lets make a deal. The tubes on the ones I have are sooo thin, I know I couldn't weld tabs to em, (not saying it couldn't be done).
K I will dig em out and get you some picks so you can choose.
 

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Precision Craft Marine
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The most over looked issue on production headers is the fit of the exhaust flange to the head, and how the tube is positioned on the flange. If you bolt a set of production style headers on to your head, with out the valves installed, and flip the head over, look down through the valve pocket and you will realize the port alignment is not so good. Most flanges are built for cars that exit through the chassis, and not up like our boat applications. We have seen more power and quicker e.t. s at the track in this area of the headers, than changing collector sizes, and primary lenth and sizes. What happens on the dyno does not happen at the track, as much as we would like it to. The rpm window on a jet is narrow, and header testing on the dyno should be close. Flat bottoms, if geared and proped correctly should have up to a 1500 rpm window in a 1/4 mile. Hydros can have up to a 3000 rpm window, without a transmission. The worst thing I have ever seen is the twisty style headers that roll over the valve cover. Nothing like adding heat to the valve train, and killing the springs faster.
 

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The most over looked issue on production headers is the fit of the exhaust flange to the head, and how the tube is positioned on the flange. If you bolt a set of production style headers on to your head, with out the valves installed, and flip the head over, look down through the valve pocket and you will realize the port alignment is not so good. Most flanges are built for cars that exit through the chassis, and not up like our boat applications. We have seen more power and quicker e.t. s at the track in this area of the headers, than changing collector sizes, and primary lenth and sizes. What happens on the dyno does not happen at the track, as much as we would like it to. The rpm window on a jet is narrow, and header testing on the dyno should be close. Flat bottoms, if geared and proped correctly should have up to a 1500 rpm window in a 1/4 mile. Hydros can have up to a 3000 rpm window, without a transmission. The worst thing I have ever seen is the twisty style headers that roll over the valve cover. Nothing like adding heat to the valve train, and killing the springs faster.
X2!!!

The closer to the exhaust valve you get, the easier it is to piss things off! The farther away (collectors ect) the lesser the gains/losses get. Not saying there isn't anything in a properly tuned/blended/merged ect. collector (lord knows we've spent allot of time there) but realistically the gains are typically minimal and vary with output and combo.
 

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The most over looked issue on production headers is the fit of the exhaust flange to the head, and how the tube is positioned on the flange. If you bolt a set of production style headers on to your head, with out the valves installed, and flip the head over, look down through the valve pocket and you will realize the port alignment is not so good. Most flanges are built for cars that exit through the chassis, and not up like our boat applications. We have seen more power and quicker e.t. s at the track in this area of the headers, than changing collector sizes, and primary lenth and sizes. What happens on the dyno does not happen at the track, as much as we would like it to. The rpm window on a jet is narrow, and header testing on the dyno should be close. Flat bottoms, if geared and proped correctly should have up to a 1500 rpm window in a 1/4 mile. Hydros can have up to a 3000 rpm window, without a transmission. The worst thing I have ever seen is the twisty style headers that roll over the valve cover. Nothing like adding heat to the valve train, and killing the springs faster.
X2!!!

The closer to the exhaust valve you get, the easier it is to piss things off! The farther away (collectors ect) the lesser the gains/losses get. Not saying there isn't anything in a properly tuned/blended/merged ect. collector (lord knows we've spent allot of time there) but realistically the gains are typically minimal and vary with output and combo.
Exellent info in both posts. Chasing the collector aside from length and diameter is a time consuming and costly dyno deal and even then proves nothing in the boat. Personally, I think there is more to the order in which the primaries tie into the collctor is worth more than the type of collector. The big one here is what J Shelfo said about the flange. they are almost all cut for cars, and I have even seen the problem in upswept dragster headers. Like Warp said, there is more to be found at the head than the collector. the first few inches of the header should be viewed as just part of the port, and just as much thought should be spent there as you would on the port itself. One of the biggest things I question is the change from a downward curving/facing port to an upswept pipe with virtually no straight. And almost all the boat hearders suffer from this.



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Village Idiot
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There is a post on another site regarding what Joe, Warp Speed and GN7 are talking about. There was a lot of discussion about how the header matched up to the port and not just the up and down angle but the forward or back angle too. Thanks for bringing up some of these points guys as it is just one more thing to keep me up at night thinking.LOL I love good detailed tech posts.

Paul
 

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There is a post on another site regarding what Joe, Warp Speed and GN7 are talking about. There was a lot of discussion about how the header matched up to the port and not just the up and down angle but the forward or back angle too. Thanks for bringing up some of these points guys as it is just one more thing to keep me up at night thinking.LOL I love good detailed tech posts.

Paul
Not just up and down, foward and back angles, but the actual placement of the pipe on the head high or low compared to the port opening all play into it. As far a lack of straight pipe, look and the first pipe on this header (cyl #2?) Sorry 71 Hallett, it just happened to be the easiest pic to post.



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