I have a set of heads off of a 4.1 and was just wondering if these heads were the same as the 3.8 turbo heads I think the casting numbers are "9263" I'll have to double check but I think thats what it is. If these heads are ported will they flow as much as a set of ported 8445's?
9263 cyl heads
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Jerryl
Tall Unvaccinated Chinese Guy
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They are 6293. They are cast slightly different than the 8445's. Some 6293's are bridged on the end water passage and some are not. They both flow so close that its not worth mentioning. The quality of the valve job will determine the better flowing head. Bowls cleaned up and equally ported and a good valve job they will flow the same. Ive got a nice set of unbridged 6293's on an engine i just put together and plan on pushing them to 10.90's at over 125 mph on a mild tune at 25 psi. Im limited by the stock bottom end in the block or i would push it even harder.
turbofabricator
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Stage I heads ARE 6293's WITH bridged water ports. Nothing wrong with "bridged" 6293's. Not sure if the bridging really helps or not, though. Smokey Yunick felt that it was worth the effort to weld the water ports up on both the heads and the block. But he was building them for endurance. The cost of a good set of 8445 castings is cheap enough to buy a set of them instead, though. Watch for excessive core shift, though.
I looked at them today and the set that I have are unbridged. If I had the water ports welded do you think that it would affect the cooling of those cylinders (would they be more prone to detonation). If they would then I'm not even going to bother with them. I'll just save up the dough for the TA's.
turbofabricator
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Welding cast iron is an expensive proceedure. It should be done by a cast iron specialist. They heat the head to red hot, then use oxy-actylene torch to weld the head (while it is still being heated red hot in a brick oven) then it is litterally tossed into a sand pile and covered up with heat blankets to be cooled VERY slowly over about 12 hours. If you try to weld it with a TIG or other methods it can crack. Some guys have sucess with Ni-rod AC-reverse stick welding, but it is pretty thin in that area and might crack. Just buy a set of 8445 casting at your local wrecking yard. They'll be MUCH cheaper than welding the water port up. The "bridged" water port is done to help hold the gasket in place. The early Buick V6's would blow the gasket there quite often. If you use a good gasket they should work fine with the passage open, though.
Core shift is when the internal mold portion shifts in relation to the outer mold, prior to molten metal being poured into the mold. The inner mold is the mold section that forms the water passages/ports and the real reason for "freeze" plugs being needed. The inner mold is made of waxed sand and needs to be knocked out of the cylinder head after the cast iron cools. It is shaken/vibrated out through those holes. If the "core" shifts, it can cause thin spots in the castings. Look closely at the parting lines in the exhaust and intake ports for uniform parting lines. If there is thicker and thinner areas inside the port, or "steps".......keep looking for a better casting. Some are good, some are bad. If you end up with a poor casting, it will be OK if you leave them stock. If you port heads with bad core shift, you may end up with water leaks.
Core shift is when the internal mold portion shifts in relation to the outer mold, prior to molten metal being poured into the mold. The inner mold is the mold section that forms the water passages/ports and the real reason for "freeze" plugs being needed. The inner mold is made of waxed sand and needs to be knocked out of the cylinder head after the cast iron cools. It is shaken/vibrated out through those holes. If the "core" shifts, it can cause thin spots in the castings. Look closely at the parting lines in the exhaust and intake ports for uniform parting lines. If there is thicker and thinner areas inside the port, or "steps".......keep looking for a better casting. Some are good, some are bad. If you end up with a poor casting, it will be OK if you leave them stock. If you port heads with bad core shift, you may end up with water leaks.
turbofish38
Le Pétomane
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Some 6293 castings use smaller intake valve guides. .552" compared to the 8445s .600".
