I'm getting all sorts of stories on what to do here. Good idea, waste of time, etc. I'd like to see some pics if you decided to plumb lines from rear of heads & where the heck you ran them to. At the LA Roadster Show- I saw a 34 Ford running a blown hemi He was running 2- 1/2" stainless lines from the rear of the heads to bungs on his radiator. Never saw the owner to ask about the install & how it works. A few guys said it's better to run the block-off plates on rear of heads & use a crossover on front that takes a thermostat- that's the best way. My way of thinking- seems like there might be dead spots in head if block-off plates are used which could turn to steam. Routing a line from each head in rear might increase circulation & more even temps. So- anyone plumb lines from rear of head? Got pics? Where did you run them to? To radiator? To a remote Milodon thermostat housing? Plumb them both to the BBC mech water pump return? Right now, my plan is to run lines from rear of my 392 heads & tee together- and run them back into the water pump. What's your opinion? Post up pics if you have them.
The engine does not care where the water enters and with the Hemi you really do not need another cross over. I ran block off plates on the back of mine and modified the radiator to accept to 3/4in heater hoses one going in to each side of the head in the front instead of a crossover. A friend of mine had the same setup and his ran about 10 to 15 degrees cooler and the only reason we could come up with was that his was a standard transmission and mine was an auto. I have attached a picture of another friend of mine who put the fill for his raditor on the back of his head.
Interesting. This is not the 1st time I've heard someone suggest running the bypass off the back of heads. My thoughts & I could be crazy- isn't the water just sitting there at that rear block-off plate? That's why I thought it would be a good reason to run lines from there.
There might be a little water that just hangs around there but I would not think that it would cause any hot spots. We shot a thermal gun on a couple of our Hemi engines and there was not 10 degrees difference between the front of the block where the water inlets were to the back where there were block off plates. The 392's hold about 4 or 5 gallons of water with a 33/34 Walker radiator, that is a lot of water... Attached image of water inlets 392 in a 33
The factory blocked them off on car hemis so they must have figured that it wouldn't cause problems. They were worried about heat in truck hemis for big trucks & used sodium filled ex valves & wet intakes on those with heads solid on both ends.
So on trucks- they blocked off both the front & rear & ran through the intake? I'm now wondering why they even bothered w/ a pad on rear of heads at all if it wasn't used. Interesting.
The heads are interchangeable side-to-side, like many other V-type engines. There is no front or rear, so they'll work on either cylinder bank.
I believe you are correct on stagnet water movement/hot spots. Use 1/4 aluminum plate and copy the factory plates. Drill and tap them for 1/4 pipe and use #6 AN, or good ole barbed brass fittings and the appropriate hose of choice. I run them to the thermostat housing. You can drill/ tap your existing one or Moroso & Canton Products sell a cast aluminum with the ports already for you they come with a flat block off vented or not for the top, or one that uses a radiator cap. I've done this to many an engine including a 289 Studebaker that has similar plates. Every engine ran 10-15deg cooler. Make sure no part of the cooling system is above the radiator including the hoses, or you'll need a fill/expansion tank mounted on the firewall etc., so it becomes the highest point. After the initial coolant fill, make sure the engine has been properly "burped" to relieve any air bubbles.
PS. If you run the lines to some point on the engine (thermostat housing, water pump etc.) you may go hard line if you prefer, as long as the return ports are engine mounted and NOT body/chassis mounted.
I already have a pair of these plates from Hot Hemi Heads. This is a 41 Willys w/ a crossflow radiator. EVERY part of this engine is above the radiator. I am using this to bleed the air. It's the highest point in system.
You can "tee" the rear return lines in at your front cross over hose, or weld bungs into the "vent box" your using.
Am using my left rear HH plate to run my heater hose off, tidier, 1 less hose running across the engine. Cheers Ian S
On 51-4 hemis they used a wet intake with the water going out the hole in the flange between the 1st & 2nd cyls. In '55 they changed the car hemis to dry intakes. DeSotos are all wet intakes, & all Dodges are dry so even the engineers between the Divisions couldn't agree on what was best. None seem to have seen a need for a rear crossover.
I run a small pro stock style radiator in the trunk with a remote pump under passenger seat that has a y block I made twards the front that goes to the front of the motor where the water pump would go stock, then it goes out the back of the heads with lines off both heads to another y block, then back to the radiator has a restrictor in the return pipe with I believe a 5/8" hole to slow the coolant no thermostat. Runs about 180° all the time. The car is driven on the street all the time and I have temp gauges on both heads in the water fills up front and they are pretty close to the same temp as the gauge in the car that is in the bottom of the block no hot spots at all checked it with a temp gun. It's been on the road for 3 years without a problem I'll post more pics tomorrow when know know the garage hope this helps Jeff Posted using the Full Custom H.A.M.B. App!
Here is more pics kinda hard to see what's going on but if u look close u should be able to figure it out to much stuff in a small car Posted using the Full Custom H.A.M.B. App!
Ok- here's the update. Ran the motor w/ rear block off plates & head temp was 8-10 degrees different front to back. Car runs at 185-190 degrees w/ a 180 degree stat. Removed the block off plates & found this. Hard to convince me we don't have a circulation issue here. FYI- this motor was run on tap water/antifreeze, not distilled water. Bought the rear plates from Hot Hemi Heads that were tapped for 1/2" & installed 2- 1/2 mip x -6an 90's. Pretty nice piece but notice raised areas at allen bolt heads. Was a problem for my Moroso oil dipstick mount so I milled one end flat- forgot to get a pic of that. Time to flare some 3/8 hard line. Thought about running 1/2" line but do I really need that much water movement? Close up of Mastercool hydraulic flaring tool. Best money you ever spent if you run a lot of hard line (I do) I have all dies for 45 & 37 degree including inverted flare. Here's the plate & fitting mounted on rear driver's side head. You can see the oil dipstick right next to it. I bent the 3/8 line 90 degrees & ran it right next to base of blower. Here you can see the -8x-6x-6 tee & used to tie in both heads. I installed a brass bleeder painted black to remove any trapped air. Waste of time. Air is pushed out by the water pump. I got no air in lines. I'll go back later & either remove bleeders & plug or bend longer lines. -8an braided line from tee to water pump inlet. Better view View of driver side plumbing w/ bleeder. Results? Temps front to back of head are nearly same temperature & is running right at 180 degrees. Next mod- replace 180 degree stat w/ a 160 high flow w/ 3- 3/16 holes drilled in it, mounted in my new HHH crossover w/ black fittings. Yesterday, it was 95 degrees out, extremely humid w/ off & on sprinkles. Drove car, idled it in my garage for nearly 2 hours & never got over 170. Was it all worth it? Hell yea!!!
Considering how few miles most of these projects actually get driven, I don't think cylinder wear is going to bother these guys... .
I took out the 160 stat & re-installed the 180 I had before. Runs right at 180 after all the air is out of system.
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