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Old 09-29-2011, 02:26 PM
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Fine tune my SBC 350

My 67 El Camino is running pretty good. I want to fine tune the car now...It has 350 engine, 9-1 compression, RHS vortec 64cc heads, headers, HEI, Comp magnum 286h cam, TH350 with 3000 stall, 4.10 gears, Holley 670 carb, etc...

My vacuum gauge shows 9" of vacuum with car in drive, at idle. The plugs show a little lean. I was thinking of changing the power valve from 6.5 (stock) to 4.5 and change the 65 (stock) primary jets to 67 for starters. The initial timing is set to 24 degrees with 700 rpm's in drive. Any thoughts or suggestions....

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Old 09-29-2011, 02:55 PM
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Quote:
Originally Posted by Madmax305
My 67 El Camino is running pretty good. I want to fine tune the car now...It has 350 engine, 9-1 compression, RHS vortec 64cc heads, headers, HEI, Comp magnum 286h cam, TH350 with 3000 stall, 4.10 gears, Holley 670 carb, etc...

My vacuum gauge shows 9" of vacuum with car in drive, at idle. The plugs show a little lean. I was thinking of changing the power valve from 6.5 (stock) to 4.5 and change the 65 (stock) primary jets to 67 for starters. The initial timing is set to 24 degrees with 700 rpm's in drive. Any thoughts or suggestions....
The motor may be a little soggy because of the mis-match of compression ratio and camshaft timing. The cam you're using has an intake duration of 236 degrees, while the static compression ratio is calling for a cam with an intake duration of around 204 degrees.
http://www.crankshaftcoalition.com/w..._compatibility

Do a compression test to see what you have for cylinder pressure.
1. Fire the motor and bring the coolant up to operating temp.
2. Disable the ignition system so that you don't have a fire in the engine compartment.
3. Remove all spark plugs so the starter can turn the crank easily.
4. Wire the carburetor primary throttle blades wide open so that the motor can breathe.
5. Turn the motor through 4 or 5 "chuffs" on each cylinder to make sure you have maxed the gauge each time.
Your change of power valve agrees with info from Holley....
http://www.holley.com/data/TechServi...wer_valves.pdf

Last edited by techinspector1; 09-29-2011 at 03:08 PM.
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Old 09-29-2011, 03:39 PM
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Quote:
Originally Posted by techinspector1
The motor may be a little soggy because of the mis-match of compression ratio and camshaft timing. The cam you're using has an intake duration of 236 degrees, while the static compression ratio is calling for a cam with an intake duration of around 204 degrees.
http://www.crankshaftcoalition.com/w..._compatibility

Do a compression test to see what you have for cylinder pressure.
1. Fire the motor and bring the coolant up to operating temp.
2. Disable the ignition system so that you don't have a fire in the engine compartment.
3. Remove all spark plugs so the starter can turn the crank easily.
4. Wire the carburetor primary throttle blades wide open so that the motor can breathe.
5. Turn the motor through 4 or 5 "chuffs" on each cylinder to make sure you have maxed the gauge each time.
Your change of power valve agrees with info from Holley....
http://www.holley.com/data/TechServi...wer_valves.pdf
Good points. At some time in the future, I plan on switching out to a more agressive short block. Keep the suggestions coming guys...
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