Rigging/plumbing things
 

I noticed alot of guys are anti "header" on here. I will agree, that headers, especially when buying used, is a gamble.

I've had this conversation with buddys, but thought I'd bring it up here too for discussion. I can't tell you how many engines I see guys posting pictures of, with headers, whether it be CMI, Stellings, Lightnings, etc, that have too SMALL of line feeding them. There is nothing worse for double walled stainless headers with many welds, than getting them super hot, and then cold, then hot, then cold.

Most header manufactures, and Mercury Marine, recommend, or use, 1 inch, or 1 1/8, lines, to feed the headers with water. I see alot of guys feeding them, with -12 AN, or even sometimes, -10an. At idle speeds, there isn't a whole lot of pressure in the system. The sea pump can move alot of water, but it cannot make a lot of pressure, at low speeds. In order to get flow from small lines, you need lots of pressure. Just for comparisons sake, take a look at what a 1 inch line, can move, vs a -12 AN line.

-10 AN = 5.5 Gallons per minute

-12 AN = 9 Gallons per minute

1 inch = 24 Gallons per minute.

1 1/8 inch = 30 Gallons per minute

On top of this scenerio, you often see guys runnign a crossover setup, with Bypass's. When the thermostat is closed, very little water is moving past it, and most jumper hoses, are also very small. Now you are restricting flow to the headers even worse. Or those not running thermostats, will run "restrictors" in an attempt to build heat in the engine, and are really building heat in their exhaust .

I'm sure there is someone here with an engineering backround, that can chime in on this topic, that knows flow capacities better than me.

Another complaint I often hear is

" I installed a crossover setup, and my water psi was too high, went back to a circulating pump, and its all good now".

The problem wasn't the lack of circulating pump, causing high water psi. The problem is, the setup wasn't plumbed properly more than likely, and the cooling system, simply couldn't get rid of the water fast enough, so psi builds up. I've seen it before, where a buddy had -10 lines feeding his exhaust. I suggested changing to 1" lines for his exhaust, or -16 AN as minimum. He didn't want to spend for the -16, and didn't want to use a hose with clamp setup, so he went to -12AN. His water psi did drop by doing so, and his exhaust manifolds were not as HOT , as before.

If you've ever hooked a sea pump hose directly to a 55 gallon drum, and simply idled the engine, you'll see how quickly it can empty that drum of water.

Water flow not only helps cool the exhaust, it makes the oil coolers, transmission coolers, and engine, simply run cooler. Oil coolers, are much more efficient with volume, as long as theres enough supply. With a raw water cooled setup, we have unlimited supply.

I was talking to a guy at Teague a month or so ago and he told me they run -12 to all there header connections, nothing larger.

Provided you are flowing enough water to fill the system, I dont see the benefit of pressure. Sure there will be some pressure as the system is full of water that is moving thru it, but excess pressure to me would mean either your trying to stuff too much in or you have a restriction and not letting enough out. Pressure is a byproduct of flow vs restriction is it not?

Volume is what we want, not pressure.

These builds are the first for me not running a circ pump, going with a cross over with the whipple water pump delete kit, Im running CMI sweepers, it would be nice to know what the gap is between the primary and outer tube. if you put a large amount of water volume to the header manifold and it cant disperse it through the tubes you build pressure.

https://www.youtube.com/watch?v=vXB5RRwC_l8

https://www.youtube.com/watch?v=HWGcvwHZSE8

Most headers I have seen, have a 1 inch bypass tube for the exit to the tailpipe. The BIG TUBE headers, for the big power engines, usually have 1.25" bypass tubes if I recall.

My stellings headers, have four, 3/4" nipples, one for each tube.

You can do water output volume tests right off the impeller housing per Mercruiser specs for non closed and closed cooled engines. Water flow volume is the numbers you are looking for to be within spec rather than water pressure.

also clear hose testing thru out the cooling system can and or will tell you a lot. You do not want air bubbles or water flow to back up

I think the minimum spec, is about 7.5 GPM, from the sea water pump at idle if I recall. Which would make sense. In that CMI video, with a fresh impeller/housing, they are seeing about 10 GPM from the sea pump.

That is at idle though. At 6000rpm screaming across the lake, making big hp, and big HEAT, I am sure the system is capable of much more water flow. I'd want to keep those headers as cool as possible, by giving them as much water as they can take.

At idle speeds, you aren't seeing 1300, 1400, 1500+ degree exhaust temperatures.

I think the big problem with headers, especially at idle speeds, is the distribution of water. Each tube is its own channel so to speak. Its being fed from a single line. There is no guarantee, that each tube, gets an even amount of water flow.

I know for a fact, certain tubes tend to run hotter than others on mine, at idle. one of the things I was looking into last year, was a better drive ratio for the water pump.

In the aftermarket world, say with roots blowers, alot of the crank accessory pulleys, are small. Smaller than mercury used. That slows the pump down. I did some calculations last year, and forgot what they were, but just because you may be idling at 700 engine rpm, depending on the pulley setup, your pump certainly may not be.

My headers have a 1 inch ID connection to the the distribution manifold and the same size ( single ) to the tail pipe, Im a bit concerned going to a -12 5/8 ID connection on the input side of the header.

The gap between the two walls? Almost non existent at the bends which is probably why that's the first place you'll see the discoloration from overheating.

Which tubes are hotter?? maybe look at how it is fed and how it exits... Water takes the path of least resistance. Turbulence can also decrease flow.

Thats what I was looking for, I didnt figure it was much, 1/8 inch at best, thanks for the post

With that much area in the tube,,, I am almost inclined to think that the water at that point it almost working more as an insulator, keeping the heat from transferring to the outer tube rather than removing the heat (cooling)

Mild, with your stellings dumping a 3/4 inch fitting per tube to the tail, I have to think there is a larger volume of water passing between the inner and outer tubes compared to the CMI

that is correct about not much area gap in between the header tubes especially at the bends and very easily for stuff to collect / clog in those narrow areas causing restrictions of water flow thru, hence why sometimes one header portion of the header runs hotter than the one next to it,

Another thing to consider is how the water flows through the tails. Mine have "dams" in them so the water is forced to fill the pipes and not just flow along the bottom. These were added in, I'm not sure if that is a common practice or not when they are made.

Dam's = restriction ?? which builds pressure to fill the tube's for cooling,...............all this pressure is giving me a headache.....:sport009:

https://youtu.be/a01QQZyl-_I <iframe width="560" height="315" src="https://www.youtube.com/embed/a01QQZyl-_I" frameborder="0" allowfullscreen></iframe>

I'd guess that the opening at the top is large enough to allow the water to flow freely once it fills the tube. I don't think it would increase pressure.

I meant four 3/4 inch lines feeding the tubes at the inlet side At the outlet, it is a 1 inch tube , to the tailpipe. The connection at the headers "supply" , coming from tstat , is also 1 inch, like your .

Here one example off the top of my head cause I know this one in my sleep.

Merc 496 and of course closed cooled - Sea water output test.

in the water testing only at 1000 rpms for 15 seconds needs to equal min of 2.5 gallons of water flowed in a empty bucket

Here is some figures I dug up while sourcing parts on diesel builds. I used an online calculator that takes orifice sizes and pressures then gives a maximum GPM flow rate possible.

.50" Dia @ 20psi = 23.31GPM
.50" Dia @ 30psi = 28.55GPM
.50" Dia @ 40psi = 32.97GPM

.75" Dia @ 20psi = 52.45GPM
.75" Dia @ 30psi = 64.24GPM
.75" Dia @ 40psi = 74.18GPM

1" Dia @ 20psi = 93.25GPM
1" Dia @ 30psi = 114.21GPM
1" Dia @ 40psi = 131.88GPM

1.25" Dia @ 20psi = 145.71GPM
1.25" Dia @ 30psi = 178.46GPM
1.25" Dia @ 40psi = 206.07GPM

1.50" Dia @ 20psi = 209.83GPM
1.50" Dia @ 30psi = 256.99GPM
1.50" Dia @ 40psi = 296.75GPM

Also according to Hardin, a single stage merc style impeller pump flows the following based off the pump RPM not engine. Seem to line up with the examples above.

1000 rpm: 11.5 gpm
1400 rpm: 15.5 gpm
2000 rpm:​ 22 gpm

Hope that helps.

10-4....I was thinking that collector must look like medusa LOL CMI are the same

I had thought about running a bypass so I could run a T-stat ?? seems like one thing is good to do but it will possibly lead to other issues. I hate boats

What some run, on the jet boat side especially, is called a "cracker valve".

Basically a spring pressure valve on the headers that only opens above 5-10lbs line pressure. This setup allows the headers to heat up more at idle, so when you jump on the throttle the cold tubes ain't screwing with your fueling mixture. Also claims to help with reversion issues. Did some reading on it a while back, some Merritt to the design. However this mod does require a small bypass tube dumping that 10gpm idle water flow somewhere down stream.

The bypass system is almost a must have on cammy lightweight jets.these pull water out of the jet pump bowl and can deliver over 50 psi on the cooling system side causing burst hoses and intake gaskets .
Baffle inserts work better on those too ,with some water dump management.Did run a similar system on a zz502 with cmi headers that was running a sherwood trs style pump ,headers got quite warm to the touch but never cracked , plus it sounded better at idle lol.
Never had a hint of reversion ,even with the long local no wake zones.