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Old 04-26-15, 11:30AM   #1
devtech
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Default 78 TA 400 Running hot

So I've got a 78 TA 400 and had the motor gone through. Ever since I've had it, it had ran anywhere from 220-240 degs. I've checked the thermostat, replaced the water pump, checked the clearance and changed the gap so it was as tight as possible. I have a new radiator and put on an electric fan with a good shroud. While trying to find out why it was running hot the 1st fan decided to catch fire so I just put a spal 3000cfm on it. So with it tearing into the motor is it possible for either the intake or head gaskets to if been install backwards or blocking a water passage?
Any help would be greatly appreciated.
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Old 04-26-15, 07:01PM   #2
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It could be a number of things, right down to the radiator cap. Could even be a timing problem, were the timing keeps advancing. Couple of questions, does it run hot when just sitting there idling or gets hot when your driving down the road.
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Old 04-26-15, 07:23PM   #3
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I doubt it's a head gasket install wrong. I'd check the little things that cause it to run hot first. First make sure it's a 160 thermostat, and it's installed the correct way. Make sure it's not the thermostat that's not opening enough. second make sure you have the right pressure radiator cap. Third timeing, put a running light on it, make sure the timing doesn't keep advancing, I've seen timing that keeps advancing all the way up to 50 degrees, that will definitely make it run hot.

When you say you checked the clearances, and there tight what clearances are you talking about.
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Old 04-26-15, 07:43PM   #4
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get a lazer digital temp gun.I keep one on my boat and in my garage tool chest.You can take temps where the water goes into and out of the radiator.You can check it at the X over.Also exhaust temps.I had a engine that I thought was running hot and found out it was the gauge.Tom
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Old 04-27-15, 01:18AM   #5
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I just got my Lazer temp gun today to check for myself. For the radiator cap it is the that came with the radiator. It is a Champion three row and it was there fan that almost caught fire. When idling it says right about 184 is driving down the freeway it creeps up to 220-240 (According to my Fast EFI computer and temp sensor). I have a 180 thermostat and it is installed the correct way (I double checked). I believe my timing is set to 12 deg with the advance disconnected. I'll verify that in the next day or so. As for the clearances, that is for my water pump and divider plate. When I pulled it apart there was about a 3/16 gap between the impeller and the plate so I got it as close as I could without touching through impeller.
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Old 04-27-15, 02:32AM   #6
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Sounds good, a 400 typically likes a total of 36 degrees. All in around 2500 rpms if it keeps advancing that's your problem. I've seen the advance up to 50 degrees. If it's not the timing Id try a 160 thermostat. Can't hurt. Let us know what lb that radiator cap is I'll do some checking and see if I can found out what lb cap it should have.
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Old 04-27-15, 03:40PM   #7
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So what psi should the radiator cap be? Also the 36 deg total timing @2500 rpm is that with the vacuume advance hooked up.
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Old 04-27-15, 11:05PM   #8
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I really don't know what the pressure cap should be, but I think any auto parts store would know if you give them the year, like acreplacement cap. I'd say with the vacuum advance disconnect.
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Old 04-27-15, 11:24PM   #9
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16 psi on the radiator cap
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Old 04-28-15, 10:35AM   #10
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Thanks for the replies, im going to try to check it out soon. Been helping my father in law with his 71 nova dropping in an ls3. My gut is telling me that I have a flow issue. With the cap off and the car running at temp with the thermostat open I hardly get any water moving compared to the 71 nova or a 85 camero. Seems like I only get about 25% the flow of those two. I think either somthing is obstructed or blocked. The motor was done before I got the car and come to find out the guy who built the motor has had lots of issues with other motors he had built (the joys of living in a small town, you can find out about anything). Is there any easy way to check water passages through out the motor with out a complete teardown? I'll check the timing and cap first but I cannot shake my gut feeling.
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Old 04-28-15, 11:17AM   #11
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I had the same issue, drove me nuts. Turn out to be the timing kept advancing. It would keep advanceing up to 50 degrees.

Let's us know when you figure it out.
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Old 04-28-15, 11:19AM   #12
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Quote:
Originally Posted by Mb125 View Post
16 psi on the radiator cap
Did check mine and that's what mine is 16 psi.
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Old 04-29-15, 01:57AM   #13
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Got a little time with my car today just as it started to rain. I disconnected the vacuume and checked the timing and it was at 12 degs, then when I went to 2500 rpm it was way off the timing marks as they only go to 14 degs so I'll have to measure and mark my own (unless there is another way?). The radiator cap has no making so still not sure what psi it is but grabbed it to head to the parts store to grab another. I'll let you know what I find by swapping the cap out.
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Old 04-29-15, 09:33AM   #14
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get a timing light that has a degree wheel on it. dial the degree wheel to about 32 now at 2500 you should se the mark.
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Old 05-05-15, 01:30AM   #15
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Ok, so I got another timing gun and it's not the timing, at an idol at 900 rpm it's at 14 degs and at 2500 rpm total it's about 34-36 degs, bought a new radiator cap and will take it for drive later. I also pulled the thermostat out to check my flow and was a lot better with it out so I'm going to check it in a boiling pot of water tomorrow. It is a 180 deg Stat now so I'll replace it with the 160 I think you mentioned.
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