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can you plug the coolant crossover

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Old 08-09-2009, 11:12 PM
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Default can you plug the coolant crossover

i ve got an ls1 in a69 camaro and im using an afco conversion radiator without any ports other than the overlfow. im going to bypass the t.body. instaead of putting a hose and bolt on the nipple, can i just get two of the same rear plugs and cap off the heads. That line isnt the main flow line so i cant see there being an issue. has anyone done this?
Old 08-10-2009, 05:07 AM
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Originally Posted by lsxfirstgen
i ve got an ls1 in a69 camaro and im using an afco conversion radiator without any ports other than the overlfow. im going to bypass the t.body. instaead of putting a hose and bolt on the nipple, can i just get two of the same rear plugs and cap off the heads. That line isnt the main flow line so i cant see there being an issue. has anyone done this?
You can't cap off the front and rear, only the rear. You may have to drill and tap a hole in the top of the water pump.
Old 08-10-2009, 05:17 AM
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Yes, you can cap them.

People do it all the time with no problems.

This is a common arguement on here. Some people say the vents were put there for a reason and that it shouldn't be done. Others routinely do it and don't have any problems.

So who do you believe? The guys who guess it will be a problem of the ones who know for a fact it isn't?
Old 08-10-2009, 05:28 AM
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Originally Posted by Pop N Wood
Yes, you can cap them.

People do it all the time with no problems.

This is a common arguement on here. Some people say the vents were put there for a reason and that it shouldn't be done. Others routinely do it and don't have any problems.

So who do you believe? The guys who guess it will be a problem of the ones who know for a fact it isn't?
So you're telling me, that GM spent all that money, installing them, and they were not needed? Do you have proof that nobody ever had a problem with them plugged? If this is the case, why does the GM LS swap manula say you need to hook them up? By the way I speed all the time and never get caught, since I've never had a problem with this, does it make it OK?
Old 08-10-2009, 06:03 AM
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Because the intake is Dry, no coolant crossing over, you need the front tube to help remove air that gets trapped at the top of the engine.

If you want to take a chance of overheating and ruining your engine just listen to guys like Pop N wood and cap them off.
Old 08-10-2009, 08:35 AM
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As already correctly stated; NO, you cannot cap both front & rear. Keep the fronts, tie them together & then to the top of the radiator. It's an air vent that allows the trapped air to be purged. You can put a sleeve w/ a nipple into the top radiator hose & run the front head vents to it, if there is nothing to connect to on the radiator. Good-luck.
Old 08-10-2009, 09:16 AM
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I ran my 04 gto with the front and rear capped and no problems at all car never ran hot. Even at the local track spraying it every pass and hot lapping the car like mad. 0 issues. So you decide.
Old 08-10-2009, 10:02 AM
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as it sits right now, i have it plugged with a hose and bolt. i have not had any problems with it. So whats the difference of plugging it and capping off the heads? air cant be purged out either way so i dont understand how capping the heads shouldnt be done. with the pipe plugged any air thats in the enigne will stay in the pipe.
Old 08-10-2009, 10:13 AM
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Question To Plug or not to Plug ??

If you got all the AIR out, prolly would not be a problem. However, If you can drill and tap a hole into the suction side of the water pump, I'd do that for safetys sake ! However, it would be best to pipe it to the top of the radiator to omit the possibility of any air in the system !
Where that pipe connects is the highest point in the cooling system. If there is ever any air, it will get trapped there if they are plugged off and could possibly cause a hot spot in the head ..

Last edited by davidws6; 08-10-2009 at 10:15 AM. Reason: .
Old 08-10-2009, 10:22 AM
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Dorman makes a heater hose adapter thats 3/4x3/4x3/8 that give yous a place to run that small line too. I did it on my 442, haha which hasnt run yet, but I think its fine.

https://www.dormanproducts.com/cgi-b...tegory_list=:0
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Old 08-10-2009, 10:22 AM
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Well like I said. This is a subject of some debate on this site.

Just giving you enough information to make an informed decision.
Old 08-10-2009, 10:26 AM
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it makes sence to have it on the factory setup. my radiator is the highest spot in my system. Im not to concerned with air in system becasue i use a cooling vacuum system to fill it which takes air out, creates vacuum and pulls coolant in. I dont think that a crossover pipe that is plugged off is any different that capped heads. with it plugged, a small amount off coolant is just going from one head to another regardless of any air in there. i have ran my last two conversions like this, this time i want to cap them for the asthetics and not have a hose and bolt.
Old 08-10-2009, 11:04 AM
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i take it this has happened to you? i ran a car hard for 3 years with the nipple plugged and 0 issues. if having the crossover is necessary than i can find a way to permiently cap it. i just dont want to run an unecessary line or have a shitty looking hose and bolt. I would preffer to have a threaded fitting attatched to the nipple so that i could bleed out air if needed. It just seems easier to cap the heads off. I am not concerned with not have the line hooked to the rad cause i have ran these engines this way before. Is there anyone elsse who has simply put caps on the heads?
Old 08-10-2009, 04:05 PM
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Run it with them all capped and let us know how it works.
Old 08-10-2009, 04:35 PM
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This is a good solution. GM actually did this very thing on some of their trucks and SUVs. I agree with poconoe joe, knowing that the auto makers will do anything they can to reduce costs, I would think it if was not needed, then they would have eliminated it. It's not just air that it gets out of the heads, but steam as well. Clearly some folks have plugged them without apparent problems. Your mileage may vary. I drilled and tapped my water pump, you don't even notice unless you are looking for it.

Pat

Originally Posted by cutlass_455
Dorman makes a heater hose adapter thats 3/4x3/4x3/8 that give yous a place to run that small line too. I did it on my 442, haha which hasnt run yet, but I think its fine.

https://www.dormanproducts.com/cgi-b...tegory_list=:0
Old 08-10-2009, 04:44 PM
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Originally Posted by LS1MCSS
Run it with them all capped and let us know how it works.
Did you see these two posts?

Originally Posted by jashell1562
I ran my 04 gto with the front and rear capped and no problems at all car never ran hot. Even at the local track spraying it every pass and hot lapping the car like mad. 0 issues. So you decide.
Originally Posted by lsxfirstgen
as it sits right now, i have it plugged with a hose and bolt. i have not had any problems with it. So whats the difference of plugging it and capping off the heads? air cant be purged out either way so i dont understand how capping the heads shouldnt be done. with the pipe plugged any air thats in the enigne will stay in the pipe.
I know users jomomma and superwake502 have posted in other threads that they run with them capped also. There have been others who have posted the same. The guy I originally got the idea from, who’s user name I can’t remember, said he has done 10 LS swaps and all of them capped the vents.

I cannot for the life of me understand why people seem to take this so personally.

Like I said, you can listen to all the people speculate on why they THINK it can’t be done, or you can listen to the people who run that way with no problems. If someone has something definitive then I would love to see it.

That whole argument about steam and air traps just doesn’t hold water. These things aren’t air ports subject to the whims of gravity. This is a dynamic system under pressure. If air gets trapped in the head then there is a flow problem, not a venting problem. So if anything these are flow ports, not vents, meant to increase flow in localized areas of the heads. But if that is the case, then why did the almighty GM engineers see fit to remove them from the rear of the engine when they went from the LS1 motors to the LS6 and beyond? Why are the flow characteristics different in the front of the head rather than the back?

But now I am speculating. Basically making thing up.
Old 08-10-2009, 05:55 PM
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Why do we even try? People live according to their own reality regardless....... This is simply another thread where the OP wants to justify a bad idea. It's not a good fck'n thing to do...ever. I already removed the post where I explained the dangers to the OP. Based on his reply, he is not @ all interested in hearing anything other than, "It's a KNARLY CONCEPT DUDE," epic. So, Good-luck & post those picks once tops of the two front pistons deform.
Old 08-10-2009, 06:08 PM
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Originally Posted by Pop N Wood
Did you see these two posts?





I know users jomomma and superwake502 have posted in other threads that they run with them capped also. There have been others who have posted the same. The guy I originally got the idea from, who’s user name I can’t remember, said he has done 10 LS swaps and all of them capped the vents.

I cannot for the life of me understand why people seem to take this so personally.

Like I said, you can listen to all the people speculate on why they THINK it can’t be done, or you can listen to the people who run that way with no problems. If someone has something definitive then I would love to see it.

That whole argument about steam and air traps just doesn’t hold water. These things aren’t air ports subject to the whims of gravity. This is a dynamic system under pressure. If air gets trapped in the head then there is a flow problem, not a venting problem. So if anything these are flow ports, not vents, meant to increase flow in localized areas of the heads. But if that is the case, then why did the almighty GM engineers see fit to remove them from the rear of the engine when they went from the LS1 motors to the LS6 and beyond? Why are the flow characteristics different in the front of the head rather than the back?

But now I am speculating. Basically making thing up.
I'm not going to turn this in to a pissing contest, since I know I can out **** you, Since I can overflow a 44 oz Sonic cup, ask the girl that was holding it. But back to the subject, since the front ports are higher then the rear ones, eliminating the rear ones, was an engineered choice. The motor does tilt to the rear, so the air pocket will move to the front. GM figured they could save money by only using the front ones. By the way, they eliminated them in the vans, I think before the LS6. If you think that air can't get trapped, in a pressurized system, how can a water pump get cavitated?
Old 08-10-2009, 06:18 PM
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Originally Posted by LS1-450
Why do we even try? People live according to their own reality regardless....... This is simply another thread where the OP wants to justify a bad idea. It's not a good fck'n thing to do...ever. I already removed the post where I explained the dangers to the OP. Based on his reply, he is not @ all interested in hearing anything other than, "It's a KNARLY CONCEPT DUDE," epic. So, Good-luck & post those picks once tops of the two front pistons deform.
like i said above, has it happened to you? Im not looking for your un-expert advice, i am simply aksing who has and who has not plugged the caps. I have my own reasoning about why or why not to cap them. obviously you have not capped them so stop posting thats all the info im after.
Old 08-10-2009, 07:56 PM
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Originally Posted by lsxfirstgen
like i said above, has it happened to you? Im not looking for your un-expert advice, i am simply aksing who has and who has not plugged the caps. I have my own reasoning about why or why not to cap them. obviously you have not capped them so stop posting thats all the info im after.

Can't stop posting when you keep asking me questions??? No, it hasn't happened to me because I would never plug the fronts. I don't know how much time you have spent on this site lurking, but w/ only 17 posts would think that you have not read enough to have learned of the 3 cases (that I know of) where members plugged the fronts, ran low on fluid & subsaquently (didn't spell check; so may be miss-spelled) warped the top of pistons 1 & 2 from the heat in the voided area. Their posts usually begin with "missfire #2 or #1 piston" or "blowing oily air out of oil fill cap," or "WTF, my engine is spitting coolant out of the overflow."

I'm too old to waist my time posting "un-expert" advise. These things have happened & my comments are made in an attempt to keep it from happening to you. Good-luck & I'm out.


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