merge collectors

[Lockwire]

or change valve timing the exhaust duration is like 280 @ 0.039
id have to check my notes for centerline.

Don't be afraid to go less exhaust duration than intake either if you get to that question in development...

That is engine religion thinking there...

Part of the gain in using a cone is from the shorter exhaust timing mentioned above. Stuart.

[hoffman900]

Thanks for the tips, Calvin.

I must say, I'm glad this topic exists as it has brought you out of hiding on this forum. Certainly one of the best posters on this forum over the years.

Cheers,
Bob

[exhausted]

Thanks for the tips, Calvin.

I must say, I'm glad this topic exists as it has brought you out of hiding on this forum. Certainly one of the best posters on this forum over the years.

Cheers,
Bob

Thanks Bob, I am realizing how much more folks on this general forum need help understanding what is going on here.

[proheader]

For us next generation guys, we need to gain all the knowledge we can get as people move on to other parts of life and retire. It is vital we learn and then apply to keep the learning alive...

Proheader

[4banger]

I have ran into a problem that might be perfect for this thread. According to an online calculator, my header primary is too big. Can I put a header reducer in the collector and use it as a kind of merge? I am thinking of cutting collector off and inserting the reducer and welding it back up. will this work? Found a smaller header but don't have it yet. tell me what you think.....

ford 2300 pinto engine, 3.780 bore 3.126 stroke stock size valves(rules) 1.74/1.50...... 350 or 500 holley carb I think the
calculator called for primary of 1.33 the header I have now is a 4-1 with 1 5/8 to 1 3/4 primaries to 3" collector... will putting in reducer help me? gonna use the 350 carb but has the 500 on it now. Thanks for your thoughts

[Belgian1979]

I think you can obtain header inserts that are a venturi and therefor make the collector a merge.

[exhausted]

I have ran into a problem that might be perfect for this thread. According to an online calculator, my header primary is too big. Can I put a header reducer in the collector and use it as a kind of merge? I am thinking of cutting collector off and inserting the reducer and welding it back up. will this work? Found a smaller header but don't have it yet. tell me what you think.....

ford 2300 pinto engine, 3.780 bore 3.126 stroke stock size valves(rules) 1.74/1.50...... 350 or 500 holley carb I think the
calculator called for primary of 1.33 the header I have now is a 4-1 with 1 5/8 to 1 3/4 primaries to 3" collector... will putting in reducer help me? gonna use the 350 carb but has the 500 on it now. Thanks for your thoughts

It is important to point out here a couple of things.
The things I am speaking about here are not the whole sum of what is involved in "making" a more powerful header.
Example:

the interface between the exhaust port and the header tubes is very important to what kind of results you will get with any other modifications further down the system.
Headers in a box, (mass manufacturing) and to a large extent even custom built headers, do not grasp nor can they afford the time it takes to make this area as good as possible. Loosing velocity and flow here is not recoverable. Hurt flow at the head and there is a direct measurable loss of maximum power. This is the case from your grocery getter car to the most powerful motors. You can not just put a smaller diameter tube header and expect it to run better. It is possible if done correctly but store bought pieces usually need to be larger as the larger tubing is the way to overcome flow losses (power) at the flange, not to mention tight radius bends. Bolting the larger header can show more power upstairs but what you give up in overall power is overlooked or ignored. This is why you see 1.75 or even 188 tubes on SB chevies that only make 450hp.

So when I point out that most headers are too big, I am talking objectively and the other part of the story is that it is not simple or cheap to get a correctly sized system that really changes things.

Glad people pick up that the collector sizing is a good way to reduce reversion and get a larger power band. Reducing tube size at the end of primaries or modifying an existing swedged collector can effect the amount of reversion but if you reduce flow potential you probably wont be happy.

[4sfed]

The interface between the exhaust port and the header tubes is very important to what kind of results you will get with any other modifications further down the system.

. . . store bought pieces usually need to be larger as the larger tubing is the way to overcome flow losses (power) at the flange, not to mention tight radius bends . . .

So the best design would have the flanges machined to match the head, with a smooth transition up to the correct tube diameter if necessary?

How does a step at the head differ from steps in tube diameter further down the pipe (step headers)?

Thanks,

[DaveMcLain]

How does the merge collector interface with the rest of the exhaust system if there is one? Are there any particular rules that need to be followed if the collector isn't at the end of the exhaust system? Also what would happen if after the expansion of the merge if another contraction/expansion were to take place at X distance down the pipe could this be tuned to produce a beneficial effect?

[englertracing]

The interface between the exhaust port and the header tubes is very important to what kind of results you will get with any other modifications further down the system.

. . . store bought pieces usually need to be larger as the larger tubing is the way to overcome flow losses (power) at the flange, not to mention tight radius bends . . .

So the best design would have the flanges machined to match the head, with a smooth transition up to the correct tube diameter if necessary?

How does a step at the head differ from steps in tube diameter further down the pipe (step headers)?

Thanks,

I think you want something like this if the port is too big or oddly shaped.
Most aftermarket would rather slap a larger tube over it instead of forming the exhaust to fit the port.

It's better to preserve velocity at the port and step her @ about 8" where its useful.
Too large a step at the port, then too large at the step and too large to the collector.

[Belgian1979]

That looks almost like the exhaust stubs from a Rolls Royce Merlin engine.

I have been tuning my engine for a while now and based on the VE values I'm seeing in my fuel tables it looks like its hard to go to 100% or more VE without a very tuned exhaust system.

How would you go about to tune out a dip in the 2000-3000 rpm range and an increase in VE at higher rpms ?

[exhausted]

The interface between the exhaust port and the header tubes is very important to what kind of results you will get with any other modifications further down the system.

. . . store bought pieces usually need to be larger as the larger tubing is the way to overcome flow losses (power) at the flange, not to mention tight radius bends . . .

So the best design would have the flanges machined to match the head, with a smooth transition up to the correct tube diameter if necessary?

How does a step at the head differ from steps in tube diameter further down the pipe (step headers)?

Thanks,

Most ports are larger than they should be so it can result in a reverse step… not a good thing for flow…
BBC NHRA stock is a good example. A 188 od tube is almost 20% smaller than the port, still makes more horsepower, and how well one makes the reduction, losing the least flow, the more power.

Hope that helps.

[RevTheory]

Hey Calvin, thank you for taking the time to post. I for one, really appreciate your time

[dirtracr5]

I have been tuning my engine for a while now and based on the VE values I'm seeing in my fuel tables it looks like its hard to go to 100% or more VE without a very tuned exhaust system.

It really isn't hard to get 100% or more VE. We do it with our 2bbl circle track engines. I can't imaging not being able to do it with something unrestricted.

[exhausted]

Well, this is a F1 piece. It makes a transition from the wide oval port to the round tube. Area is the same going in as coming out. If you do not have time to make the transition from 2 valves port merging to one round port in the casting then you have to do it in the header.....