This discussion started here http://mmb.maverick.to/showthread.php?t=68542&page=53 but continued it here to not clutter Franks great build thread. Maybe adding that crossover in the back is the benefit. The stock intake manifold has a crossover in the back of the manifold. Many high performance manifolds do not have the cross over. This leaves the water that in the back of the heads no place to go exept towards the front of the head and is probably reulting in less circulation. Ford designed the coolant to cross over back there for a reason. My first Edelbrock Performer RPM manifold many years ago did not have a cross over in the back. After a few years I had the manifold off for some reason and noticed alot of corrosion at the rear of the manifold where it blocked off the water. I wanted to get a different manifold that allowed the water to pass through. At the time the Weiand Stealth was the best I could find. A few years later, about 2000 or so, I noticed Edelbrock changed the design on the performer RPM and now had a cross over in the back for the water flow. It seems most dual plane manifold designed for street driving now use the rear cross over, because it helps the circulation to flow as it was designed to. Most of the single plane manifolds are fro race only applications so the heat isnt taken into consideration as that big of a factor.
I am not sure why that is but I have seen people drill and tap the ends of the manifold and run a crossover tube before. this site seems to have it figured out. http://www.fourdoorbronco.com/board/showthread.php?5230-Engine-Cooling-System
Why do you feel that a rear crossover would causes the water to flow differently? Both ports are under the same pressure. Where else can the water flow from the rear other than forward to the intake manifold and thermostat? Water flows from the pump into each bank at the front of the cylinder block, around the cylinders to rear, up into the rear of the heads and then front again to the intake, thermostat, radiator, and pump.
Well it was designed to have a crossover for some reason. I'm sure Ford had a good reason to add it to the design of the parts. Maybe the water the hits the dead end at the manifold stops there and the rest of the water lower in the head flows the path of least resistance. If nothing else that deadend is a good place to hold air bubbles. I know the non flowing water sure corroded the manifold quickly. If anybody has an old intake without the cross overs check out the corrosion and pits left where it blocks the passage.
I do not use a control valve in mine with the set up, because this mod would be usless with the heat off..... and you are correct about a low percentage of the water going throught the bypass, I'll be it's lesst then 25% that flows through there..... My belief is that you are eliminating any possibility of an air pocket, plus it help keeps the temp across all the cylinders more even..... The added bennefit is the engine running temp drops which is a definate plus as far as I am concerned(the least I have seen one drop by doing this is 10 deg, but I have seen as much as a 20 deg drop)..... I have also done this by running the crossover directly back to the water pump when not using a heater.....
Ford intakes had a rear coolant crossover ? Gee that's funny, I've never seen one in all the 35 years I've been wrenching on them. I have seen very few aftermarket intakes with em, but that never seemed to be repeated in later intakes. I wonder why ? If you ain't got one, I don't think you'll ever need one. I never did.
You mean the two coolant ports on the intake side of the head ? That was never the intended purpose of the two ports. The reason they are there is due to the fact that the heads are completely interchangeable between left and right cylinder banks. Imagine an engine assembly plant that suddenly found themselves short of drivers side heads. Wait, maybe that's why the Mod motors are so expensive now to manufacture. Or at least part of the reason.
For what it's worth, there are a few Mod motor builders/shops doing a very similar mod to the heads on the 4V 4.6/5.4l engines. They have you remove the plug at the end of each head and install a heater hose tap to run the coolant from side to side and into the heater core. Supposedly, they say that it eliminates pockets that develop at the back of the left side in particular at certain RPM ranges that might lead to localized overheating around cylinders 7&8. I had concerns on the cars that I was hired to install them on of recirculating too much hot coolant directly back to the water pump without going through an effective heat exchanger because the hoses were a full 5/8" id with no restriction. I started using a cut down washer with a 3/8" hole in the hose on the inlet from the taps to slow the flow enough to allow good heater core flow at idle but still provide the pressure relief function of the kit. (the kit essentially bypassed the heater core in a parallel circuit)
Yeah, for a minute I thought I was having a brain fart and not remembering correctly, so I went out to my shed where I have a stock '68 302 intake and a late 80's EFI intake. Neither has a rear crossover for the coolant.
Yeah, I always thought that it was for interchangeability. But I wasn't going to speak up, since I didn't know for sure.
You got to look long and hard to find those that do have one. It may have benefits, but I've never tried it. It would have been greatly appreciated in my 89 Ranger after the V8 swap.
The Edelbrock Performer manifold on my 351W doesn't have a rear crossover, but it does have a couple of bosses cast into it that look like a great place to tap into in case you want to make one like Frank's.
Well Maybe I was wrong about the factory manifolds. Ive found some that have the rear cross over and some that dont. And on the aftermarket side its hit and miss. some single planes without cross overs and dual planes with them and vice versa. But I'm with Frank inthat I prefer to have the rear crossover for better cooling and less air trapped. Plus my first Performer manifold was trashed from corrosion back where it blocked the passage. I guess its just a personal preference thatmight not even need to be considered when picking a manifold. I havent found anything in print saying one is better than the other, just gotta go off of what you have experienced for yourself i guess. Weiand Stealth With cross over Edelbrock Performer RPM, looks like they are back to no cross overs. At some point they had cross overs bacause I have one Heres an edelbrock perfromer part number 3723, it has water passages But A Torker II has corss overs and ports in the back This one is advertised to have " It has a bridged rear water crossover passage that helps keep engine temps down. "
Looks like these guys are stumped on this too http://www.fordmuscleforums.com/all-ford-techboard/410071-rear-water-passage.html And one guy has an RPM manifold with passage like I do, wish I could find out when they did that. "My old original 289 2 barrel intake has no rear water passage. My Edelbrock RPM intake has a rear water passage. My Victor JR intake has no rear water passage. My later 302 EGR 2 barrel intake has a water passage. Sheesh, I wish they would make up their minds, LOL. "
