'73 Camaro NETO/N
A different perspective from the original post.
Note the center water passage between where the exhaust valves are. It's big while the ones on the other 2 are small. On older small blocks the center passage in the block is small and needs to be enlarged. Can't remember for sure but I think it's 1/2inch.
But as the general rule the water makes it way back to the rear cylinders and then flows through the heads all the way to the front. It's a very long path to get to the radiator, gathering more heat all the time. If the rear cylinders really are warmer with the stock coolant flow setup, then don't the rear-to-front coolant bypass hoses slightly alter the stock flow providing additional cooling "bias" towards the rear? -If you're pulling more coolant out of the top rear by making it's flow path back to the radiator easier, you get more coolant pulled towards those hot rear cylinders, evening out the temps, no?My concern has always been the water in the by-pass hoses is not going through the cylinder heads and provides no cooling. I do run -4 hoses to remove any steam that might form.
I don't know if there is any "one answer fits all" for this issue. If it works for you.... do it.
Scott, there are LOADS of differences in those gaskets, including front-to-rear...For reference, here are two different sbc head gaskets, Fel-pro and Cometic. Absolutely no difference in coolant regulation front to rear….
Is it going to "rob flow" from the cylinder heads, or just alter the path of the front so that it's more towards the rear? The flow is still exiting the rear cylinders of the heads. -You're just robbing flow from the front and giving more of it to the rear; given that the rear cylinders are the hottest, that actually makes sense if your goal is more even heat distribution, no?I can understand using small (-3 or -4) to vent the system. Any significant flow is going to rob flow from the cylinder heads.
It makes sense not seeing a temp drop at the water neck. The same amount of heat being transferred, but more equalized between cylinders.This modification has been around forever. What it does is helps promote more water flow at the rear of the engine block and head. I have seen A-B testing and never saw more then 5-10 degree drop in the back of the head and didn’t see any temp reduction in the water coming out of the water neck. This was 20+ years ago so I don’t remember the exact numbers and I’m pretty sure it was on a Pontiac engine in a daily driver. In my opinion it doesn’t help in a drag race only application using an electric water pump. In a road car or endurance application it can help but you need to use at least a -6 hose to move enough coolant.
The head gasket holes are symmetrical front to rear, if you fold the gasket or flip it over.Scott, there are LOADS of differences in those gaskets, including front-to-rear...
The Cometic has the early SBC water pump bypass hole highlighted in thick red blocked off, while the Felpro has it open. The Felpro 1003 has the hole right next to it opened up larger than in the Cometic -both of these features would push more coolant towards the back of the block rather than from the front of the block and up to the head and then out the front of the head back to the thermostat exit.
The Felpro has a bunch of extra coolant holes right around the troublesome siamesed exhaust ports, which, I like, though.
The Felpro looks to have better center exhaust port cooling, but the Cometic pushes more coolant to the rear as far as I can guestimate...
Regardless of what the differences in flow accomplish, they are definitely different towards the front of the block.
@ChopperScott Do you have the Cometic Gasket #? I'd love to look at it in more detail.
Thats because R07 engine is not an gen1 sbc...Hmmm, modern roundy round guys don’t seem to need all them extra hoses. There are bleeds in the rear though. Still waiting for real data on ET consistency within .003 due to extra coolant hoses. Anecdotes don’t count. Carry on.