CAPTAIN JACK

For the life of me, I can't find the articles I read about this. I remember it said something like, you can benefit from doing the hose from the rear cooling port to the front port to help keep the rear of the heads cooler. It always seems like number 8 gets hot and drops seats. I've bought 2 sets of heads from people this has happened to. Now I'm putting my motor together and nows the time I could do it easy. I won't do it if its a wait of time. Looking for some good solid advice, and I don't really want a dump hose running out the back or sides either. What do you all think?? Thanks!!

Finally found one thread on this subject:
http://www.offshoreonly.com/forums/g...ter-ports.html

Rookie

iTrader: (4)

When I switch heads on my GenV engines I kept seizing exhaust valves on #8 and #6 until I drilled out the intakes. 3 valves destroyed in all. I have 2 identical engines and one engine ran +80*F hotter on the backside of the engine near #8 cylinder. Drilled out the manifold and now they are all even. I will drill out all of my intakes from now on.
I actually just Tee it into my exhaust manifold and dump there.

johnnyboatman

iTrader: (5)

what do you mean by t into exhaust? wondering

Young Performance

We put the hoses on just about every engine that leaves here. However, we either dump them overboard or into the tail pipes. I don't see why it wouldn't help by just running the hoses to the front of the intake. It has to be better than nothing.
Eddie

Rookie

iTrader: (4)

No problem, I just plumb it to the top of my SM manifolds.
The red hose goes from intake to exhaust manifold.
I wanted to propagate flow that is why I did not plumb to the front of the manifold. When the thermostat is closed it would run really hot back there. I used an infrared pyrometer and hit all 4 corners to determine that I needed flow at all times. Also I can somewhat regulate water pressure with different size diameter fittings and hose.

dandercam1

iTrader: (1)

I like your idea. Do you have any trouble getting heat in the motors when the seawater is cold (say 50 deg.). Are you running aluminum heads

Budman II

iTrader: (1)

I have been thinking about doing this as well, but the Merlin marine intake that I am running had the bronze liners in the water passages, and on the back ports it is plugged with a solid bronze insert. The bosses are there, but they are filled up with bronze. Is it possible to drill and tap these?

IRWIN

Yes budman you can just drill and tap them NPT and put AN fitting in. We have done this several times with no issues what so ever. The Merlin intake is a pretty good piece with just a little work. Joe Irwin

Budman II

iTrader: (1)

Thanks Joe. How large do you drill them? Didn't look like the brass allowed for much more than a 3/8 hole before I would get into the aluminum.

IRWIN

I want to say I tapped them 3/8 NPT with a 37/64 drill bit but I do remember them being very close to the aluminum. If it looks like the 3/8 NPT will be to big just go down to 1/4 NPT the biggest thing is just trying to get the water and air out of the back of the heads so they don't create hot spots. I run a lot of external lines on my LS engines and even a #4 line moves a lot of water. So don't be worried about the line being to small. Joe Irwin