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| Over my head (Cylinder Head Alignment) https://slantsix.org/forum/viewtopic.php?t=30147 |
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| Author: | 62 alum [ Wed Jul 23, 2008 10:03 am ] |
| Post subject: | Over my head (Cylinder Head Alignment) |
I have rebuilt a couple of iron slant sixs in the pass with good result. I got my alum. block back from the machine with an .020 overbore. When I bolted the head to the empty block to check bore alignment I found that all the bores have shifted about .060 to the plug side of the head. I ground the alignment pins off center to compensate but am unable to shift the head. Any ideas appreciated. |
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| Author: | SlantSixDan [ Sat Jul 26, 2008 6:20 pm ] |
| Post subject: | |
Usually it's easier to leave the alignment pins in the block unground (install new ones) and grind the alignment pin holes in the head oversize. Then use half the head bolts to put the head on the empty block, shift the head around until the bores line up nicely, and make four marks across the head-block junction: one front, one rear, one manifold side, one distributor side. You can make these marks with a cutoff wheel chucked into a Dremel tool. Then go ahead with your engine assembly, and when it's time to install the head, run the bolts down finger tight, carefully shift the head until all four marks line up, then torque the head down. |
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| Author: | 62 alum [ Sat Jul 26, 2008 8:15 pm ] |
| Post subject: | |
Great information, I have another set of pins and will start over. Thank you |
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| Author: | Doc [ Mon Jul 28, 2008 11:43 am ] |
| Post subject: | |
Hopefully, you resurfaced the block's deck while it was at the machine shop. Also inspect the head bolt through holes in the head, I have seen interference between the head bolt and the thru hole(s) that prevents the needed location shifting. Factory head bolts have a larger shank diameter right under the hex head, that is the area that usually interfers. DD |
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| Author: | 62 alum [ Tue Jul 29, 2008 6:34 am ] |
| Post subject: | |
The block and head have both been milled flat as well as the manifold surface.I also ran a 1/2 drill bit down all of the head bolt holes to clear any burrs. I opened up the alignment holes in the head to 5/16 ". This has allowed me to center the head over the bores.Thanks again for the good information. One more question-My service manual does not state any thing about using any kind of sealant with my head gasket,I only have the one nos gasket and want to get it right the first shot? |
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| Author: | CARS [ Tue Jul 29, 2008 8:05 am ] |
| Post subject: | |
Can this be done to an iron head also? I don't see why not but I figured I would ask. |
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| Author: | Doc [ Tue Jul 29, 2008 9:49 am ] |
| Post subject: | |
Yes, this can be done with any cylinder head that is located with dowel pins. One additional "trick" is to use some epoxy "dough" to re-cast the enlarged pin holes in the head. This takes extra time but take a lot of the alignment "guesswork" out of the final head installation. Do all your fitting and marking as already discribed, then wrap the dowel pins with one layer of tape and apply a small dab of grease around the base of the dowel pins. Mix and push some epoxy dough into the drilled-out pin holes in the head. Use a small nail, toothpick or tool to pack it onto the walls and to start a center hole. Under-fill the holes by 30% and keep the rough center hole small. Carefully install the head and re-center it as it goes down, snug it down with a couple of bolts and allow the epoxy to conform to the pins and set. Once set, you will have to carefully pry-off the head, try to remove it as evenly as possible. (the tape and the grease is important, it makes removing the head and clean-up a lot easier, once the epoxy has set) With the head off, you can clean-off excess epoxy and full any voids as needed. I usually drill the recasted holes a little deeper just t be sure they clear the top of the pins Recheck your alignment... it should now be "spot-on" and repeatable. DD |
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| Author: | Pat Dawson [ Tue Jul 29, 2008 12:20 pm ] |
| Post subject: | |
I sprayed my head gasket with Permatex spray copper head gasket sealer on the advice of my machinist. Don't know if it's necessary or beneficial. My machinist would not bore or deck my aluminum block and guess the bore shift you experienced is why (I know, get a new machinist). There is nothing holding the top of the bore in place when that machinery hits it. So I ended up using a flat bar wrapped in 80 grit sandpaper and ran it one way across the head several times (per my machinist's suggestion) and honed the cylinders with the new rings ending up under the .030 gap max per the FSM. Not exactly new but it runs good and doesn't smoke. A bit of blow-by though. 4000+ miles since rebuilt. I did find that re-torquing the headbolts after you fire it up and put a few miles on it is a must. |
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