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Old 02-03-2013, 05:11 PM
sjzdx sjzdx is offline
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Default 383 head gasket question

I have a 1965 383 engine in a 64 Chrysler 300. I have the heads off and about to put it all back together with new gaskets. I noticed the old head gaskets and the new gaskets actually block some of the antifreeze holes. On the gasket they are long ovals but on the heads and on the block they are circle holes. The holes line up but the gaskets would seriously slow down the flow of coolant in 3 holes on each side of the engine. The problem is I cant find the correct head gaskets. All parts listed are for the wrong head gaskets.

Does anyone know the correct head gaskets part number? If I cant find them should I just enlarge the holes of the gaskets I have?

Thanks for your help!
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Old 02-04-2013, 06:00 PM
John Kunkel John Kunkel is offline
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The narrow slits in the gasket that connect two passages at the top of the block/head aren't really intended to move a lot of coolant volume, they're just steam ports.
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Old 02-04-2013, 08:01 PM
sjzdx sjzdx is offline
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Thanks for the help John. Do you think it would make a difference if I drilled open the slats on the gasket to match the holes on the block/heads? Figured it couldn't hurt.



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Old 02-05-2013, 02:56 PM
John Kunkel John Kunkel is offline
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Don't mess with them, they're designed that way for a purpose.
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Old 02-05-2013, 03:59 PM
sjzdx sjzdx is offline
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Im curious as to why.
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Old 02-06-2013, 02:36 PM
John Kunkel John Kunkel is offline
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Air/steam needs less space because it will compress, unlike a liquid. As I stated earlier, the two passages that are connected by the slot in the gasket aren't intended to move a large volume of liquid coolant....just steam.
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Old 02-06-2013, 03:32 PM
sjzdx sjzdx is offline
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Right, I understand your answer. I just don't understand why they made gaskets to slow the flow or restrict the amount going through the passage. That is what is confusing to me. I am asking all this because I have had issues with this engine running hot and I always have had this issue. I have tried, re coring rad, high flow water pump and diff temp thermostat. None of which helped the problem. I stumbled upon this gasket question while replacing the head gaskets and cant help but wonder if this is a potential contributor to the engine running hot or is this gasket created this way to actually help the running hot issue.

Again thanks for your insight John.
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Old 02-06-2013, 09:26 PM
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DanL DanL is offline
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What did the old gaskets look like? Did they have the same (small) opening or were they more like full-size to the holes in the block and head?

I can't speak to the science of the small openings, though I believe I'd trust John's judgment on the issue. But here's why I ask.

If the original head gaskets had a small opening (either the slits like these, or round but smaller than the holes in the castings), and at some time during the life of these gaskets the engine did NOT overheat, then simply opening up these gaskets would be the wrong thing to do. In other words, don't re-think what the engineers came up with.

Last year I bought a 66 Mustang with a 289 that ran hot, though it didn't boil over. I had an oil leak at the intake manifold and while I had that apart to fix it, I decided to pull the heads to take a peek inside. All was in pretty good shape so I re-assembled the engine. I suddenly had an engine that not only ran hot, but would boil over after about 20 miles or so. I struggled with it for most of last summer. I kept finding chunks of rusty crap in the top of the radiator that I could get out of the top tank with a magnet. I eventually wound up with a Gano filter in the top radiator hose to catch the crud, and a bottle of Evap-O-Rust in the block to free the scale. I'd drive it for 15 miles or so and clean the screen. Drive it and clean it. Again and again and again. The amount of crud gradually decreased and the engine stopped overheating.

OK, the reason for this diatribe is that I had a block that had been neglected by the prior owner, and had a LOT of rust in the system. Removing the heads, I think, dislodged a lot of it and began to clog my radiator. When I finally got the crap outta there, the engine ran nice and cool in all types of weather.

I learned a lot about cooling systems last summer. If you have an infrared thermometer you can measure the temps at the top and bottom of your radiator. If you have more than 20 degrees or so difference, you're not flowing through your radiator quickly enough. I also learned that the old yarn about the coolant "going through the radiator too fast to give up its heat" is a lot of hooey. You can't change the laws of thermodynamics and even though it spends less time in the radiator, it circulates through there much more often and also doesn't have the dwell time in the block and heads to absorb as much heat on each cycle through the engine. High flow rates are fine as long as your pump isn't cavitating (pressure in the system helps prevent this).

If it was my engine, I'd leave the gaskets alone and assemble the engine. If you still have overheating issues, keep looking because your trouble is elsewhere.

Here's the link to a page that was a tremendous help to me in fixing that little pony car:

http://yarchive.net/car/radiator_diagnosis.html
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