CMI, Exhaust Reversion and Shoe laces . . .

[mphatc]

Time to clear the waters . .
First I need to apologize and eat a set of my shoe laces . . I jumped to a conclusion by following what have been considered to be "rules of thumb". .
Last week I posted that my new CMI headers had internal leaks . well after more time, a bit of testing, my CMI headers DO NOT leak! My engine suffers from water reversion at idle.
I sealed off my headers and connected them to a garden hose and house water pressure for 15-20 minutes. They stayed dry, with no leaks! FWIW, my house water pressure is 50 PSIG.
The CMI's dump water into the exhaust stream through four 1 /4" ID nozzles approximately 12" beyond the collector merge, this is 20" away from my exhaust port. This is in a 4" OD tube that transitions to 3" further downstream.
This website has a good write up on reversion:
http://www.boatheaders.com/reversionbody.htm
The most common cause for reversion is from an overly aggressive cam. I was cautious of this when we built my 302.
My cam specs are:
Duration 218
Separation: 112
Gross Lift .544"
Engine compression ratio is 10.3 :1
My CMI headers are the Etop , not the sport tubes.
So with all this given, why do I have reversion?
Here's my thoughts, and I'd really like some feedback . . and input!
The CMI headers have huge tubes, the ID is large enough enough for a BIG block, possibly too large for my puuuny 302 Ford . .
It has a crank driven Johnson water pump, which delivers alot more water than the original Jabsco. Water pressure and volume of flow combined with the large volume inside the CMI headers I believe will result in reversion.
My plan to solve this problem includes a water pressure valve to reduce the water flow through my engine and into the exhaust, along with the addition of small tubes to inject the water further down stream in the exhaust from the present points.
I had hoped that the CMI headers would avoid reversion, but between the "too much cooling water" and to low an exhaust flow rate at idle in the huge tubes . .I guess it hasn't . .
Thoughts and input please!!! Am I on the right track?
Thank you,
Mario

[BUIZILLA]

camshaft overlap?

[VetteLT193]

do you have a funky setup where the dumps are not lower than the elbow?

Usually the dumps are significantly lower than the elbow and far down the pipe. Add to that the natural lean of the boat and the engine really has to fight gravity.

What is your idle RPM?

I can't see how a too big of a pipe would increase reversion in a normal setup. Usually big engines = bigger suction. A smaller engine with a bigger pipe will drastically reduce the suction power

112 lobe separation shouldn't cause reversion with regular CMI's.

[mphatc]

Buizilla, I was hoping you'd find this !
The cam is a Bullet FW 270/270-12HR
-------------------- intake and exhaust
Duration at .050 .......... 218 218
Lobe Separation: 112
--------------------open-close open-close
Timing events at .050" ...... 1 37 45 7
Seat duration at .006 ....... 270 270
Gross Lift ...................... .544" 544"
Degree intake lobe at 108 ATDC
this is all I have from Bullet . .
Mario

[BlownCrewCab]

I Know Brownie can tell you to the Degree what durations will suck water back and what will not. When I built the motor for my 18' I was questioning about reversion (I don't remember the exact number he said) but he said anything past XX?? will suck back and questioned what I had, when I told him what I had He said Good God Son You need dry pipes all the way back, I thought that was funny.

[mphatc]

Vette,

My dumps are the 3" standard original outlets on the Corsican with flaps, and are ~~~ 5"-6" lower than the height at which the water is injected.

Water is injected 4" lower than the collector height. . collector height is the location where the 4 tubes merge. the elbow top rises above that by 6"

Idle speed is 900 rpm

Mario

[BUIZILLA]

sumtings no make a sense here

read that cam card again...

[mphatc]

Lobe lift .3400 with a 1.6 rocker arm ratio to get the 544 lift

That's all there is . . .

now maybe you know why I am puzzled .. .

Mario

[BUIZILLA]

fax me the card

305.592.5936

[VetteLT193]

maybe the water is coming from the engine? not very likely but have to throw it out there...

vibration may be a factor too... maybe they only leak bolted up to the engine. I think CMI will do a pressure check for you for free if you eat the shipping cost.

when you did your own pressure check did you have the tail piece clamped on? that clamp area is the weakest link of CMI's

[BUIZILLA]

--------------------open-close open-close
Timing events at .050" ...... 1 37
Degree intake lobe at 108 ATDC
this is where i'm confused...

[mphatc]

Custom grind and made for a 351 Windsor . .

I faxed the card . . did you receive it?

As for engine leaks . . no, just reassembled with new AFR heads, and everything else checked after the last disaster 2 summers ago. Block magnafluxed and pressure tested.

Engine runs GREAT, I have not experienced any misfires or skipping. Recall in my post last week that I discovered the puddled water in the headers "by accident . . " I had no reason to look for this, but found it while wrenching the engine after it's first 5.5 hours use.

The headers were tested with one having the elbow outlet installed, one w/o.

I can access the water nozzles and tig weld injector tubes, and reduce water flow by dumping excess cooling water out thru the bilge pump port till I install another port.

Mario

[BUIZILLA]

monyana

fax in office, not in bordelo

i'm thinking a combination of too large of tubes not promoting exit velocity, and too much water flow...

[mphatc]

so we're on the same page . . your wording is much better:yes:

I'll order the Hardin valve in the AM, and modify the elbow inlet holes
to squirt the water further down the exhaust . .

Mario

[harbormaster]

We have had that problem plenty of time before. All parts of the equation were correct but we were still getting reversion. We usually work with CMI to add a turbulator ring inside the taipipe in front of where the water dumps. You can also move you water dump further down your tail pipe. CMI works with us all the time for custom systems. Call CMI, ask for Mark Marrese. He is at 1-920-886-8233. Tell him Scot VanAlstine at Victory Marine sent you. He can also be reached by email at mmarrese@custommarine.com.


Hope this helps.

[mphatc]

Thank you Scot!

Just off the phone with Mark, conference call with a co-worker of his and they will be sending me anti reversion rings to fit inside the exhaust. Basically a cone that goes inside the 4" elbow that the water would need to climb around to get into the collector section of the headers .

I'll still add the tubes to dump the water further downstream . .

They use these cones on 600SCI Fountains to avoid reversion, so I doubt they'll effect my little 302 Ford.

Mario L.

[BigGrizzly]

They put them in mine when they made them.