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| Cam Choice https://www.slantsix.org/forum/viewtopic.php?t=41872 |
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| Author: | Dizzydean [ Sun Sep 12, 2010 5:27 pm ] |
| Post subject: | Cam Choice |
OK its cam time for me & I need help. The engine specs are: block .30 bore,oil passage mods done,surfaced only,pistons are balanced,head shaved .080,lots of porting & polishing (probably to much),large valves w/ new springs,have the aussie hurricane 4bbl going to run between the 390/500 cfm,split headers. Looking for something aggresive yet good streetability. Have 8 3/4 rear but no special gears and its auto. Thanks for the help. |
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| Author: | Joshie225 [ Sun Sep 12, 2010 6:36 pm ] |
| Post subject: | |
Actual static compression ratio? Torque converter stall speed? |
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| Author: | Dizzydean [ Sun Sep 12, 2010 10:45 pm ] |
| Post subject: | |
The comp ratio is unknown to me and I am thinking of using a stock converter...But am always open to suggestions/ideas |
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| Author: | Joshie225 [ Sun Sep 12, 2010 11:50 pm ] |
| Post subject: | |
A low compression ratio and stock torque converter will limit you to a pretty tame cam. To get best performance with the other modifications you mention I'd get the compression ratio up to at least 9.5:1 (you're almost certainly not there with just the head milling) and plan on spending at least $400 for a good 9.5" or 10" torque converter. Then you could run something like an Erson 280/270 or Oregon Cam Grinding #346 and have a powerful, fun street machine. One data point I can give on compression ratio is my +.040" oversize block was milled .080" as was the cylinder head. The static compression ratio is now 9.7:1. The same cylinder head on my stock short block is only 8.5:1. |
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| Author: | Dizzydean [ Thu Sep 16, 2010 6:26 am ] |
| Post subject: | |
Now that I talked to my machinist and he wants a measurement from the pin to the top of the block so he knows what the total hight should be. Sounds logical to me but how do you measure that with the piston & rod connected? Or if anyone (josh) knows what the finish measurement is can you let me know. Thanks for the great help. Dean |
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| Author: | RustyRamcharger [ Thu Sep 16, 2010 6:58 am ] |
| Post subject: | |
Use a depth micrometer to measure from the deck to the piston. Add that measurement to the piston height measurement. If you don't know the piston height, you can measure it using a height gauge on a surface plate; place the piston upside down on the surface plate. Alternatively you can measure the deck height and subtract half of the stroke, the rod length and the deck-piston measurement. Ken 
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| Author: | Doc [ Thu Sep 16, 2010 8:43 am ] |
| Post subject: | |
We live in a "new world", with all the on-line calulators available these days. What use to take me 30 minutes of "number crunching" know takes a few minute... if you have a few measurments. Measurements you need are: - cc volume of the combustion chamber - cc volume of any dish, valve releifs or piston dome. - The "deck height"... piston top to block deck surface at TDC. - Head gasket thickness. We know all the other specs for a factory SL6 and the common over-size options available. Mock-up the engine and measure. DD |
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| Author: | Dizzydean [ Thu Sep 16, 2010 5:26 pm ] |
| Post subject: | |
The engine has the crank n pistons already in wouldnt it just be easier to just chop off the measurement I ask for? So much technacality for a close shave!! |
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| Author: | sandy in BC [ Thu Sep 16, 2010 6:09 pm ] |
| Post subject: | |
Just measure the deck height......thats the distance from the top of the piston to the top of the block at TDC. If we know the bore and deck height we can calculate so very important things. Measure then chop. If you dont want to measure it makes cam choices very easy....anything will do. |
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| Author: | Dizzydean [ Fri Sep 17, 2010 4:34 am ] |
| Post subject: | |
That does make a lot of sense. Thanks for all the help guys. |
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