[BADDTA]

Is there a reason why the center hose is a -6 and the other 4 corners are -8? I was gonna plumb them all at -8. If you’ve had experience with this please answer.

[Scott Stoneburg]

I have no experience with it, but possibly due to the size of the hole that can be drilled at that location?

[Bobwiththe66]

www.pas4performance.com

These guys are great and very knowledgeable Pontiac people.

They helped me with my build.
Bob,

[Dave Polichena]

Mine is the opposite, I have -8 in the corners going into the Y and out to manifold is -12, -10's are in the middle. I want as much flow in the middle as possible. This has worked well at 15:1

[BADDTA]

Thanks Dave. I appreciate the info

[cgeise]

the head modification in the center is usually a very small diameter. You can feed it all it wants but will still pass only so much

[Tom Vaught]

Without more info we are just sitting around the computer and throwing out general
ideas. General ideas rarely work.

Tom V.

[Tom Vaught]

Without more info we are just sitting around the computer and throwing out general ideas. General ideas rarely work.

Tom V.

[Formulas]

If you had a laser thermometer you could take temperatures at each hose exiting the heads as soon as possible after a run,
Increase hose size at the hotter exit and if you have a cold reading perhaps decrease to give flow volume priority to the hotter areas
Stands to reason the front would be the coolest but testing can prove strange things

[steve25]

Some things are a cut in stone, like wherever you find the hottest coolant is where you will also find the highest pressure trying to get coolant out of that area.
In places / locations like that if your trying to pump into it you need to overcome that pressure that’s there and that may not be possible with the water pressure you have coming out of the pump at a given rpm , or possibly ever!

In cases like this you want to just allow the coolant out and into a cooler location so it continues to flow into the radiator.

A common problem with the front water crossover even if you have a T stat there or not is that the front outlet of each cylinder head are constantly having a temperature induced pressure war with each other.

The head with the highest coolant temp will have the highest pressure and then block off the flow of the other head into the upper radiator hose.

Then once that head has cooled down the other head now being hotter starts to pass it’s coolant into the upper radiator hose.
This war is constantly going back and forth while the engine is running and the amount that one head sits there not flowing gets longer as the level Hp goes up with rpm.

This condition is why the unfortunately short lived Edelbrock pro port heads had a water take off in the middle of the head around where the exh crossover use to be on stock type heads.

[R 70 Judge]

Originally Posted by BADDTA

Is there a reason why the center hose is a -6 and the other 4 corners are -8? I was gonna plumb them all at -8. If you’ve had experience with this please answer.

This should answer some of your questions. Tons of great info in here!

https://forums.maxperformanceinc.com...Water+manifold

[R 70 Judge]

Info from the above link

“ Here's some "Basic Recommendations":
1) Belt Driven Pumps and Mechanical Pumps with the Moroso Water Pump Drive.
>> Bare Minimum = 4 x -8AN Hoses. Two from the Front and Two from the Rear. <<
(This Calculated Volume is Slightly Greater than Running a Single 3/4" Restrictor in Place of the Thermostat.)
2) 30 GPM Electric Pumps.
>> Most Racing Applications = 4 x -10 AN Hoses. Two from the Front and Two from the Rear.
(This Calculated Volume is Slightly Less than Running a Single 1" Restrictor in Place of the Thermostat.)
>> Optional = 2 x -10 AN Hoses Front. 2 x -10 AN Hoses from the Rear coming off of a "Y" Fitting where Two -8 AN Hoses are Plumbed to the Rear of the Heads and 2 x -6 AN Hoses are Plumbed to the Center of the Heads.
3) Inline Water Pumps and High Volume Electric Pumps above 30 G.P.M..
>> Three -10 AN Lines Per Cylinder Head for a Total of Six. These Six Lines Plumbed into a Coolant/Water Outlet Manifold like the One Offered by John Marcella and CSR to just Name a Couple.”