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| To shave or not to shave. https://slantsix.org/forum/viewtopic.php?t=36391 |
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| Author: | Dave95693 [ Tue Jul 21, 2009 11:22 am ] |
| Post subject: | To shave or not to shave. |
For all you slant six guru's: Engine with unknown mileage. All holes measure approximately the same compression with only slight variance. Oil pressure is 48 lbs at 1200 rpms and 20 at idle. Spark plugs all burn same with a tan coloring what I would consider normal. Question: What is the risk of taking the head off and shaving it .050 and reinstalling it? Nothing else would be done to the engine except a new head gasket. 
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| Author: | SlantSixDan [ Tue Jul 21, 2009 11:49 am ] |
| Post subject: | |
Me, with an engine in such apparently good mechanical shape, I'd leave it buttoned up and focus on other (bolt-on) upgrades for now. And I definitely wouldn't shave!  
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| Author: | Dave95693 [ Tue Jul 21, 2009 12:15 pm ] |
| Post subject: | Ha Ha Ha |
Coming from you Dan, that answer does not surprize me. But now you have my curiosity up. What else could you do besides the supersix upgrade to a 2 barrel? Headers seem like overkill to me with a stock engine. My exhaust is already at 2.25 with a Magnaflow muffler.
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| Author: | SlantSixDan [ Tue Jul 21, 2009 1:22 pm ] |
| Post subject: | |
Well, rather than headers I'd look at Dutra Duals if you need more exhaust capacity. Already got the Super Six, eh? Well, what's your ignition system look like? Good recurve and HEI upgrade, maybe? What's the overall goal here, and what year engine/car is this? |
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| Author: | Dave95693 [ Tue Jul 21, 2009 3:05 pm ] |
| Post subject: | Goal |
Right now I'm just experimenting since I am fairly new to slant six engines. The goal I suppose...in the end is to end up with me at the drag strip. Its in a 71 Demon, 904 tranny, 8.75 3.23 posi rearend. |
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| Author: | Dave95693 [ Tue Jul 21, 2009 3:07 pm ] |
| Post subject: | Ok, that didn't make any sense. |
The goal is to end up with a hp motor that will not embarrass me at the drag strip. |
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| Author: | SlantSixDan [ Tue Jul 21, 2009 4:21 pm ] |
| Post subject: | |
Ah, drag racing; I assumed street use. Then yeah, I guess you might reasonably look at increasing the compression ratio, changing the cam, etc. |
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| Author: | ceej [ Tue Jul 21, 2009 7:36 pm ] |
| Post subject: | |
Do you know the chamber volume and how far down the hole you are now? Check that out before cutting. On a stock uncut engine, 0.50" isn't going to equate to much. Perhaps a tad better ET, but you'd be better off getting into the 0.090 to 0.100 range for a drag car. Then you get the chance to decide if you want it off the head, or off the block. Get up into the 0.100" range and custom push rods may be needed. What kind of ET are you shooting for? CJ |
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| Author: | 1980volare [ Tue Jul 21, 2009 7:55 pm ] |
| Post subject: | Re: Ha Ha Ha |
Quote: Coming from you Dan, that answer does not surprize me.
But now you have my curiosity up. What else could you do besides the supersix upgrade to a 2 barrel? Headers seem like overkill to me with a stock engine. My exhaust is already at 2.25 with a Magnaflow muffler.which magnaflow muffler do you have? how do you like it? |
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| Author: | Greg Ondayko [ Tue Jul 21, 2009 8:14 pm ] |
| Post subject: | |
You can go .100" off the block and .110" off the head and That might get you to about 10:1 and yes you will need .100" to 1.50" shorter push rods. Check you Head CC's to be sure of the compression. This upgrade would only make sense with correct cam and carb - tinake / and exhaust improvements to support the Milling of the head and block. Greg |
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| Author: | 66aCUDA [ Wed Jul 22, 2009 5:01 am ] |
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Greg where are you getting your numbers? With .210 off total you will be alot higher than 10 to 1. Im at better than 11 to 1 with .150 off. And for most combinations .100 off(in what ever combination you want) is about the max before you need push rods. My02. Frank |
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| Author: | Charrlie_S [ Wed Jul 22, 2009 5:43 am ] |
| Post subject: | |
My opinion: .050 is not worth doing. The OEM head gasket was about .022 thick. most replacement gaskets are about .020 thicker, so your net gain is only .030 |
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| Author: | Dart270 [ Wed Jul 22, 2009 6:10 am ] |
| Post subject: | |
If you bother to pull the head, do some port work and maybe bigger valves, and definitely don't mill off less than 0.080" as others have said. 0.080-100" off will get you to high 8s or 9:1, but it depends on piston-deck ht and gasket and chamber... Lou |
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| Author: | stonethk [ Wed Jul 22, 2009 7:12 am ] |
| Post subject: | |
Personally, I do not like unknown, arbitrary numbers when dealing with my engine, but thats me. I'm still a novice here but what I have read and repeating what others are saying- knocking .05 off the head you might not notice any substantial gains. I have come to find out the most important thing is taking measurements- cc chambers, check piston/deck heights, etc. will give you a point of reference. With this info you can then figure what you want to take off and where. Check the Articles section, there is lots of info on stock heights, diameters and other useful numbers. 
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| Author: | Greg Ondayko [ Wed Jul 22, 2009 9:22 am ] |
| Post subject: | |
Quote: Greg where are you getting your numbers? With .210 off total you will be alot higher than 10 to 1. Im at better than 11 to 1 with .150 off. And for most combinations .100 off(in what ever combination you want) is about the max before you need push rods.
Well I never Officially CC'd My heads So I really do not know. Maybe my engine is higher than that.My02. Frank Greg |
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