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Discussion Starter · #1 ·
im thinking about buying a set of merge collectors from someone like burns on my 70 468 drag car to pick up launch rpm torque. anyone else have experience with these?
 

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What size header primary tubes and collector OD and length do you have now? sometimes all you need is a collector extension to move torque down ..... I just trading emails with Jere Stahl right now on the same subject .....i have his headers and thinking about his version of a merge collector .........in general he does not see an advantage for a drag car if rpm does not drop below 5000 rpm for a merge type collector .....again just a generalization collectors are like carb spacers every engine is different some engines luv em and some dont .........merge work really well for circle track and road race cars FWIW
 

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Discussion Starter · #3 ·
the primaries are 2 1/8 and 36-40 long andthe collecteris 4 " in diameter and about 11 long i think. launch rpm is 500 on a brake. thanks
 

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you have a lot of header for a 468. My 540 has 2" and 60' 1.34 at 3400lb. I am planning on going to a 2 1/8 in the future though
 

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I've talked with Larry Meaux on the subject of merge collectors and his comment was "I've never seen an engine that has the correct size and length collector pick up (on the dyno) with merge collectors".
 

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I was running a set of 2 1/8" with 3 1/2" collector Hooker Super Comp Headers on my 461ci BBC with 3 1/2" exhaust and dynomax mufflers. Because of spark plug interference I had a set of headers built by Dawson Racing Headers. I told him I was stepping up to a 468 next year, 13:1 with some minor head porting and a cam to match. He built my headers and they ended up being a 2 1/8" to 2 1/4" step header with a 4" merge collector and open header (no exhaust). First race with the new headers I lost .01 in 60', but picked up .02-.03 in the 1/4. I leave off a foot brake at 1900rpm. I also need to hook up the evac.



 

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I've talked with Larry Meaux on the subject of merge collectors and his comment was "I've never seen an engine that has the correct size and length collector pick up (on the dyno) with merge collectors".

Jere Stahl told me the same thing especially when it pertains to a serious drag car ....... Gary I would play with collector extensions on your current set up first ......whether you have properly sized headers for your combo is another question
 

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Jere Stahl told me the same thing especially when it pertains to a serious drag car ....... Gary I would play with collector extensions on your current set up first ......whether you have properly sized headers for your combo is another question
Jere was the first person to explain to me (back in 1963 when I bought my first set of headers from him) that primary tube size was related to hp... not ci or rpm. He and Larry Meaux are on the same wave length when it comes to headers.
 

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Discussion Starter · #11 ·
i talked to joe sherman and he basically said nothing i would do with the exhaust over what i have now would give anything more than a tenth at most. i think playing with collector length might help as allready stated
 

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Jere was the first person to explain to me (back in 1963 when I bought my first set of headers from him) that primary tube size was related to hp... not ci or rpm. He and Larry Meaux are on the same wave length when it comes to headers.

Yep my first set was about 69 and same thing ,all about HP as it is to-day when you order a set ...........in those days if you had Stahl headers you had the best ..............wow he has been talking to racers about headers and cams for 40yrs plus
 

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do the Pro Stockers still run a merge collector that necks down to about the same diameter as a single primary tube?
 

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Many run an adjustable merge collector. It has an insert that changes the venturi size.
 

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Bikes have run merge collectors successfully for years. Their advantage probably wont show on a dyno but may on the track.
 

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the primaries are 2 1/8 and 36-40 long andthe collecteris 4 " in diameter and about 11 long i think. launch rpm is 500 on a brake. thanks
In the book "How to hotrod Big Block Chevys" by H.P. Books there is a sketch on exhaust collector on page "23" showing an experimental exhaust collector as used in dyno testing a 427 of the day. It started with an overall 4" diameter collector and necked down to 2 1/2" over the next 7.5" and then flared out in a megaphone ending back at a 4" outlet, twenty inches back of the 2 1/2" spot. It picked up power and torque over the entire range from 4500 rpm on up. Be advised this is only a race setup. It could easily be built by Jere Stahl or Ed Henneman of "Headers by Ed".
 

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do the Pro Stockers still run a merge collector that necks down to about the same diameter as a single primary tube?
Yes, somewhat, they're quite interesting too. In looking over some i saw at Houston Pro Stock Superbowl a few years ago i noticed that the had a 4-2-1 setup with different tubes paired on each side of the engine, they necked down where the four tubes became two pairs, then expanded back out. I can't recall how large the collectors were but they weren't too big. I bet "Burns" could tell you for sure.
 

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Discussion Starter · #19 ·
i have another situation. i climbed under the car and started measuring the primaries. they are actually anywhere from 32 to over 42 so theres atleast 10 inches diff. the way these are built 2 tubes run over the frame on both sides and these are the long ones.i know some difference doesnt hurt anything but this much would i think. i think optimum length would be 32-34. ofcourse the problem is trying to package headers in a stock frame. i think i could build a new set and get them closer but i dont think i could change them much with the space constraints. these are from lemons. what do you guys think?
 
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