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| Camshaft upgrade https://slantsix.org/forum/viewtopic.php?t=58762 |
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| Author: | Oppie5150 [ Mon Nov 30, 2015 4:10 pm ] |
| Post subject: | Camshaft upgrade |
Hello everyone I'm getting ready to rebuild my 72 slant six 225, I'm looking to put a rv type lift cam in it. I am simple just looking for more torque and a little more power nothing major just want to wake it up a little. All in all I just want more torque if you have any other idea on how to do that while staying bellow the 400 dollar range for parts please share |
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| Author: | Reed [ Mon Nov 30, 2015 4:51 pm ] |
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Keep your stock cam and mill the head to obtain a dynamic compression ratio of 8.1:1. |
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| Author: | Oppie5150 [ Mon Nov 30, 2015 5:26 pm ] |
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I was going to do that anyway cause it has a bad head gasket. but I want more torque than just that little bit |
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| Author: | Joshie225 [ Tue Dec 01, 2015 7:22 am ] |
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Checking the compression ratio by measuring bore size, deck height, combustion chamber volume and doing the math is the first step. Don't be surprised if you have to take .080" off the head to get 8.5:1. Make sure the valves seal well. Last time I went to change valve stem seals on an assembled engine all the exhaust valves leaked. I had a ported, big-valve head on the shelf so I installed that. The compression ratio increase along with intake and exhaust upgrades made a substantial performance increase. As in over 2 seconds in the 1/4 mile ET. I didn't ever touch the stock 1967 camshaft. Mill the head to get 8.5:1 compression and have a valve job done. Check and correct the ignition advance curve. If you have the money go for bigger valves and a 2 1/4" exhaust system. |
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| Author: | Oppie5150 [ Tue Dec 01, 2015 10:15 am ] |
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I was going to have a shop do the whole rebuild for me and just wanted something to slip in so they don't have a reason to charge more on the rebuild |
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| Author: | Joshie225 [ Tue Dec 01, 2015 10:43 am ] |
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Quote: I was going to have a shop do the whole rebuild for me and just wanted something to slip in so they don't have a reason to charge more on the rebuild
Oh, that has me feeling sad. The compression ratio on these engines may be advertised as 8.4:1, but in reality they are almost always below 8:1. One I checked was 7.6:1. The very first change you need to do is to get the compression ratio correct for the cam you're using. If you're unwilling to spend the time and money to do that you're best off with a stock cam. Spend the $400 on tuning the ignition advance curve and on tuning the carburetor. If there is more left in the bank consider a Super Six 2bbl and a better exhaust system.
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| Author: | Oppie5150 [ Tue Dec 01, 2015 4:21 pm ] |
| Post subject: | |
Like I said I'm going to have them mill the block and head down so hopefully that gets it to where the compression ratio needs to be and then I'll just run the stock cam and intake/exhaust. I was planning on doing just a simple dump style exhaust just after the driver door or behind the front tire |
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| Author: | Reed [ Tue Dec 01, 2015 6:56 pm ] |
| Post subject: | |
Quote: Like I said I'm going to have them mill the block and head down so hopefully that gets it to where the compression ratio needs to be and then I'll just run the stock cam...
You would be much better off and literally get more bang for your buck if you or your machinist take the time to do the measirements and math to give your motor an 8.1:1 to 8.4:1 DYNAMIC compression ratio. Guessing and hoping are not the best ways to achieve your goals.
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| Author: | Oppie5150 [ Wed Dec 02, 2015 12:10 pm ] |
| Post subject: | |
What is the highest compression ratio you can go with stock parts before running into clearance issues, like valve to piston clearance |
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| Author: | SlantSixDan [ Wed Dec 02, 2015 12:25 pm ] |
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Quote: What is the highest compression ratio you can go with stock parts before running into clearance issues, like valve to piston clearance
As Reed said: guessing and hoping (and grabbing at the air for the biggest number with a question like this) will not get you a good result. Don't just pick out a stack of mods and parts that you think are cool. That's a good way to waste money, time, effort, and energy and wind up very disappointed. Start from the very start: Exactly what do you want the car to do differently than it does now, and how much money and time and effort can you afford to put into it?
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| Author: | coconuteater64 [ Wed Dec 02, 2015 3:54 pm ] |
| Post subject: | |
Quote: Quote: What is the highest compression ratio you can go with stock parts before running into clearance issues, like valve to piston clearance
As Reed said: guessing and hoping (and grabbing at the air for the biggest number with a question like this) will not get you a good result. Don't just pick out a stack of mods and parts that you think are cool. That's a good way to waste money, time, effort, and energy and wind up very disappointed. Start from the very start: Exactly what do you want the car to do differently than it does now, and how much money and time and effort can you afford to put into it? |
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| Author: | SlantSixDan [ Wed Dec 02, 2015 4:08 pm ] |
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Quote: Dan, I wish I had that advice when I was a teenager!
Me too.Quote: I bolted on "cool" parts
Me too.Quote: It emptied my wallet and made it undriveable.
Me too.
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| Author: | Oppie5150 [ Wed Dec 02, 2015 5:27 pm ] |
| Post subject: | |
I'm looking for more torque and the car to have a little bit of lope to it. My local machine shop said they would charge 1250 for a rebuild, including mill the head, align bore crank and cam journals, bore the cylinders, and deck the block. I'm looking for some simple bolt on parts that won't raise the price of the rebuild, that was why I was wanting a cam. I myself won't be involved in the rebuild other than removal and instalation. Simply put I'm using all stock parts, intake and exhaust manifold, head and crank. I was just wondering what the highest compression ratio is I can get out of the stock parts before the valves go on a kissing date with the Pistons. I'm looking to spend no more than 2000 on the rebuild parts and labor. I just want a little more go to make a 4 door valiant feel less like a grandma car |
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| Author: | Reed [ Wed Dec 02, 2015 5:35 pm ] |
| Post subject: | |
Have your machinist do the measuring, calculation, and milling using the stock cam to give you a dynamic compression ratio of 8.1:1 to 8.4:1. Nobody can give the "the magic number" of how much material to remove from your head and/or block due to many factors such as manufacturing tolerances, different camshaft profiles used in different year engines, whether your motor needs an overbore, etc... If you have a decent machinist he should be able to do the measuring and calculations no problem. |
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| Author: | Sam Powell [ Mon Dec 07, 2015 3:41 pm ] |
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The pistons sre pretty far down in the hole on a stock slant. You should have no troubles with valve/piston interference, especially with a stock cam. Sam |
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