4-2-1 merge collectors

anyone here ever try them? a few years back i tried a custom 4 into 1 stainless merge collector and seen nothing on slip. do ya think these 4-2-1 collectors are just another way to get your money? i see them used in nascar.

There was a discussion on Classracer about the merge collectors and cam timing changes needed to make them work. I think there was some discussion on the Tri-Y headers as well. It might be worth a read if you haven't read it already.

http://classracer.com/classforum/showthread.php?t=59745

They certainly do work but they might not work for you. One reason is that you might not be able to get a set of headers built for your car that both fit and work. The primary pipes need to be really short to use the 421 collector and that can be hard to package into a car.

Another point is that the guys who pick up power with the merge headers are typically doing something different with the head and cam. One example is using the header design to pull harder on the exhaust. Once you do that you can put a smaller exhaust valve in the head which then lets you put a larger intake valve. This is the trick that NASCAR guys did a few years back and it is the trick that some pro drag race teams use. But it is super expensive for the average guy to try and do these tricks.

OK. Sounds like that's not for me. I'll read the LINC above.

I have flowmaster 4/2/1 collectors on both sets of headers I made. First set is on the sm block in the demon and the other set is on the big block in the lebaron. Both cars run pretty well for what they are.

I understand those are good for some mid torque.

thanks for the linc. I will call elston headers when I get a chance. he should be able to point me in right direction being he builds headers for nascar as well as nhra and others. he also uses Burns stainless for collectors. learned a lot from your linc

You mean these ? lol
I bought them , welded on the evac tubes and had them coated.......only to decide that I really didn't need to enhance torque.
I went with a straight 3 1/2 " collector.
1 7/8ths primaries and they look like they'll lay pretty well against the floor.
I'll let them go cheap if anyone wants to try them out.

yes, exactly. from what i'v read they can be hard to tune. they need to be tuned to the combo and mostly the cam timing or duration. i still may be interested. pm me the lenghts and all tubing sizes with a price. i'm heading north now so i'll get back later. whos are they?

Those will work if you can cut your primaries down to about 20 inches. You have to get the primaries really short for that combo to work properly and most shelf headers just can't be cut short enough. There isn't anything wrong with the idea, it usually just doesn't fit in a Mopar very well.

yes, i'v seen that before. i dont know the length of my primarys, but i know their longer than 20 inches. thanks Andy

Check out this picture of NASCAR headers. Good luck getting that setup to fit in a Mopar with the torsion bars, steering box and steering linkage all in the way!

And they have them paired correctly. Very important for merge collectors to work.

What do you mean by paired?

You want to space the exhaust pulses out in the collector. So on a Mopar with 5-7 that fire next to each other you would put those cylinders into different sides of the collector. If you use a 4-7 swap cam then you might need to change the way a 4-2-1 header is routed.

The Schoenfeld header page shows some of this stuff. They sell 4-2-1 headers for race engines and they'll tell you which ones work with which firing orders.

I'll check that out. Thank you.

Hey Andy:
I have a manual from "Headers by Ed". He says that the primaries should lay out in rotation of firing order. Clockwise or counterclockwise isn't critical. But it should go 1-3-5-7 and 8-4-6-2. Standard cam firing order. That's not how the drivers side header is set up. But I have seen the pattern on the Chevy motor before on other headers. Is it just ease of fitment, or another theory on what works best?

Do we know the firing order of the NASCAR Chevy engine? It might have the LS1 firing order (1-8-7-2-6-5-4-3)

20 inches for the primaries ?
Is that to maximize h.p. when using them ?
To my way of thinking , there is a balancing act when you change anything in header design.
A longer primary will cost you peak h.p. , but typically will enhance torque.
I don't know that these will have the same effect as a merge collector , where a smaller primary can be used due to scavenging being enhanced.
Given that they have a 3" collector to finish , I don't know that they had high r.p.m. in mind when they designed them.
But I think you could go longer than 20 " and not lose much.