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| Rebuilding the Head. Nothing Fancy just new to Slants. https://slantsix.org/forum/viewtopic.php?t=58623 |
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| Author: | abloch [ Thu Oct 29, 2015 2:47 pm ] |
| Post subject: | Rebuilding the Head. Nothing Fancy just new to Slants. |
Greeting everyone, Signed up a few months back after lurking for many years off and on. I've had a few slants in the past and I am looking forward to the ones I will have in the future. I've been reading about the builds that all of you have done and I am quite impressed with the time, effort and money you have spent on getting the most out of these wonderful power plants. I've learned a lot and I am reading more. I've got two engines that I am working with to put together one that will be used as a daily driver in my '61 Belvedere. Both engines are early '62 to '65 productions and I have begun this project by dropping off the head at the machine shop. According to the machinist the head is good and really only needs exhaust valves, guides and seats. I've ordered new intake and exhaust valves because I might as well and he's going to get started as soon as the valves come in. FINALLY, here is my question. What is the maximum amount that I can safely have milled off the head without having to look at buying new pushrods? I've seen a lot of numbers amongst all of the builds that you have done. Based on what I've read I should be able to go .050 and not have a problem. Can I go for .070? More? In addition this is just a top end rebuild for now. I'm leaving the bottom in the car so I won't be decking the block or swapping cams. Another reason for doing this is so I can replace the exhaust manifold and install an Offenhauser 2x1bbl intake. I want to make sure everything lines up and is flush before I start wasting gaskets. Thanks guys! |
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| Author: | Joshie225 [ Thu Oct 29, 2015 3:02 pm ] |
| Post subject: | |
I've had zero trouble taking .080" off the head when using stock pushrods. That got me up to a true 8.5:1 on my '67 Valiant's 225 with a Felpro gasket. |
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| Author: | Rick Covalt [ Thu Oct 29, 2015 3:41 pm ] |
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I have done .090 a couple times and .060 & .075 all with stock length push rods. |
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| Author: | kesteb [ Thu Oct 29, 2015 9:17 pm ] |
| Post subject: | |
I have taken .100 combined between the block and head and have used the stock push rods without any problems. |
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| Author: | Pierre [ Thu Oct 29, 2015 11:43 pm ] |
| Post subject: | |
0.050-70 probably won't be an issue but ultimately it will vary block to block. More likely to happen as you get to triple digits. Put it all together and see how things look. Pushrods are easy enough to change after the fact. |
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| Author: | abloch [ Mon Nov 02, 2015 2:49 pm ] |
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Thanks for the help guys! I think I will go a little more than .050, maybe around .070 or .080. So, what sort of CC's did you end up with for the head after milling? My machinist says that my head has had some work done on it in the past. |
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| Author: | SpaceFrank [ Mon Nov 02, 2015 3:30 pm ] |
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The general rule of thumb is that each 0.0067" shaved off a slant six head will remove 1 cc from the combustion chamber, up to a point which I don't remember. My '64 head started with an average combustion chamber volume of 59cc, but with 60s-70s casting tolerances being what they were, yours might be different. I had my head shaved 0.080" with the goal being 47cc. After getting it cleaned up at a different machine shop (the first left a rough finish), the average now is 46cc. This gives me a calculated SCR of about 8.8 It's a good idea to measure your chamber volume before you decide how much to take off, especially if the head has been worked on before. You don't know if it's already been shaved a little. I used one of those $30 measuring kits that comes with a big syringe and a small plexiglass plate with a hole in it. |
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| Author: | Reed [ Mon Nov 02, 2015 4:13 pm ] |
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Quote: It's a good idea to measure your chamber volume before you decide how much to take off, especially if the head has been worked on before. You don't know if it's already been shaved a little. I used one of those $30 measuring kits that comes with a big syringe and a small plexiglass plate with a hole in it.
It is an even better idea to put the work in to calculate your desired and actual dynamic compression ratio instead of just guessing how much should be milled off the head.
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| Author: | abloch [ Mon Nov 02, 2015 4:59 pm ] |
| Post subject: | |
I'd like to do all the measuring but the bottom half that I am going to mount this head to is still running and driving me around. I've go two engines that I am working with and was just looking for a safe ballpark in which to mill. Like I said "nothing fancy". I'm still waiting for the valves to come in and then I will go up and discuss what I have learned from you with the machinist. He'll probably do the valve work, CC the bowls and we'll go from there. |
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| Author: | matv91 [ Tue Nov 03, 2015 2:59 am ] |
| Post subject: | |
Quote: It is an even better idea to put the work in to calculate your desired and actual dynamic compression ratio instead of just guessing how much should be milled off the head.
Those cams in the years you have were small. Not much over lap and early intake valve closing. You can easily check cam events with a degree wheel so you can figure-out the DCR.
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| Author: | Dart270 [ Tue Nov 03, 2015 5:41 am ] |
| Post subject: | |
I would not go above 0.080" to ensure reliable running with stock pushrods. That amount of milling will be a noticeable difference in comp and performance. I advise measuring the head thickness before and after milling to ensure that the shop actually mills it the amount you ask. Best, Lou |
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| Author: | ProCycle [ Tue Nov 03, 2015 7:28 am ] |
| Post subject: | |
The valves can always be 'tipped' to counter some of the need for shorter push rods. |
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| Author: | abloch [ Fri Nov 13, 2015 6:35 pm ] |
| Post subject: | The heads back! |
Well the head is back from the shop and ready to install. Went ahead and installed all new valves, guides, seats for the exhaust, seals and springs. Per your suggestions and my own reading I just had the bowls CC'd to 47.5 which should put me right around the 9.0-9.2:1 ratio. I had know idea machine work was going to be so expensive, but it had to be done. Next I will have the exhaust manifold cleaned up and prepped once I can get my hands on an Offenhauser dual single barrel intake. Keep you eyes peeled for me, will ya? Thanks, Drue |
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