Heater plumbing (Ford 351/GT40)

TX Foilhead wrote: With your limited knowledge of fluid dynamics, what would happen if you opened the hole in the Y to let mor water through?

I've thought about it, but I have to assume they made the diameter that small for a reason (uniform engine heating would be my guess). But it's so small, I struggle with how well it would work. And of course, if I open it up and mess it up, I just wasted $50 since I can't easily replug it back down to the original size. I'd much rather not use the Y and pump water to the heater core like it's done in my car.

With your limited knowledge of fluid dynamics, what would happen if you opened the hole in the Y to let mor water through?   

The side of my block is usually the hottest temp I measure with the IR thermometer, you may not have the issue your thinking using that for the shower. Keep us updated, I've got to instal my shower before the motor goes back in. I was thinking about picking the hot up before the Y and getting the cold after the Vdrive so it has some heat in it. Probably not ideal for heat, but being able to drain the heater with the shower head would be nice and I could turn the cold off.   No winterizing here, just a bildge heater.

Okay, so I have to admit that I have NOT put the Y in yet. The problem I have been having is I'm getting air into the heater line such that my in-line pump sucks air. I replumbed so that my shower is the "highest" point so air will get pumped out the shower (when it is on) rather than going down the heater line. But even though I've checked and rechecked, tightened, etc. every last connection between the hull intake fitting and the input side of the RWP, air is still somehow getting into the engine, getting up to the highest point (which is just before the thermostat on the intake manifold where I tap for the heater and shower(, and I get air into the heater line. If I first bleed the air out via the shower, the heat I get from the heater is so hot you almost can't aim a hose directly at skin (perfect). But after about 2 passes, there is enough air in the engine that the in line heater pump sucks air, and it gets cold at idle, and just warm at RPM. I actually ran my shower hose out the transom, and at the end of each pass while at idle, I'd turn it on for about 30 seconds to get the air out again, and the heater was hot the whole time. Just not practical.

Barring building some sort of elaborate tank to capture and bleed out the air, I am going to have to try the Y (against my better but admittedly limited fluid dynamics physics and heat transfer knowledge) since at least it will HOPEFULLY suck through the air (unless the air gets trapped in the heater core because that opening in the Y is so small it doesn't create enough flow to pull the air through.

If I still have an air problem even with the Y in (and assuming I'm not just missing a leak somewhere but instead air gets pulled into the intake due to turbulence of the hull while on plane), then I'm going to have to pull my hot water from somewhere else such as the block, which is MUCH colder than the top of the manifold......

Dang It!! What a pain. It will be summer before I get this to work right!! (if I'm lucky; I've been dinking around with heater plumbing for years....

That hole is so small that I don't think the pumps will so much of anything. One of the pumps is rated at around 500gph; that little hole would probably do about 30 per hour. I'd like to try enlarging it as well but we'l see. I'm going to put a shut off valve on it, so if I enlarge it too much, I can just close the valve a bit.

But what a pain!

gun-driver wrote: Use the "Y" fitting before the raw water pump. Water going to the raw water pump draws the water from the Y better than a T fitting improving circulation. After I installed the Y fitting heat at idle improved greatly.

I just got the Y fitting. I can't believe how small the hole is in the return on the Y. It seems that I'm not going to get anywhere near the flow I'd like for maximum heat. Since the engines run cooler than car engines, you need more flow so the heater core temp doesn't drop as much.

Since I bought the Y fitting, I'll go ahead and put it in and see how it works.

Thanks,

Use the "Y" fitting before the raw water pump. Water going to the raw water pump draws the water from the Y better than a T fitting improving circulation.
After I installed the Y fitting heat at idle improved greatly.

Heres a pic of the stock plumbing on my '95 (the brass T in the upper right)

I have not run this yet. I will install it in the spring time.

I'm aware the manifold port is likely not 5/8" npt, an adapter will be needed for my application. If someone wants to fund this research ill install it next week...

Thanks all for the replies. To answer all, I was thinking of making up a T before the RWP (rather than buy the Y from heatercraft/SKIDIM, and then putting a valve on it to shut it off when filling our hot tub. However, as some of you have mentioned, manifold to circulation pump should be good (I've also tried manifold to block but that did not flow as well).

I don't think it is a worn RWP impeller that is starving the engine of water because 1. it has only about 50-75hrs on the latest impeller and this is a problem I've always had without the inline 12v pumps, 2. it sucks and pumps water fine at idle, and 3. even if it was starving water, I would think that it would retain water in the engine (ie: if water isn't flowing into the engine through the thermostat, then water is not leaving the engine for the exhaust manifold) so water would still flow through the heater line (and of course, the engine would overheat which it does not).

So I think my two options at this point are:

1. plumb the return to the input side of the RWP
     + can remove the inline pumps since the vacuum of the RWP should pull water through it quickly
     + vacuum/suction should eliminate any air, so higher water flow which equals higher heater output
     - may slow warm up slightly and cause shower / hot tub water to be cooler if I don't install a valve to stop heater flow during warm up or filling the hot tub

2. plumb from block to circulation pump
     + will eliminate any air trapping due to low location on engine
     - will require inline pumps as that flow is not great (especially with the 3/8 tap on the block
     - water temp will be lower than at the manifold so air not as hot

I liked plumbing from the manifold to the circulation pump with the inline 12v pumps since that was the best of both worlds. But if I keep getting air bubbles at the top of the manifold that then gets into the line, I'm going to continue to have this problem (and even high speed runs don't always blow out the bubbles).

I'm leaning toward option 1 because I want the highest possible temperature out of the heater. One additional concern with that method is what potential issue can a continual stream of cold water entering the engine have? Since it was mentioned that the Y adapter is partially blocked off to restrict the flow, if I make my own with just a T, am I going to have excessive flow that causes cooling issues?

Dang! The way I have it plumbed now is perfect except for those stupid bubbles in the line!!

Gordon

I run like you had, and most auto applications, intake to Circ pump.

This year suddenly had trouble with idle heat taling off

Found....impeller was moving water, in tack, but didn't move water well at idle.

So try a new impeller. you could just be starving for water

I really don't feel your warm up time or shower temp will be much affected by returning the heater line to before the rwp. Try it, that's where many Ford PCMs have the return line.

I went round and round with this in my head last week. I've settled on 5/8" off the intake manifold and 1/2" out of the core to a simple T before the RWP. This should provide good heat, won't take half a dozen adapters to assemble and keep winterization simple.