SBC 350 Basic timing and Vacuum reading with CAM

G

Gavin

Member
Morning Folks, I'm wanting to find out a few things on my engine. I have a 350 SBC with Dart Vortec heads, and this engine has a 220/224 duration @ .050, .495/.502 lift with 120 Lobe separation. I have the Edelbrock 1406 carb running it. My questions to you all would be What is the best base timing (10* ?), what vacuum should I be looking for (15-17 Hq ?) and at what idle RPM (550-650 ?) Any suggestions would be greatly appreciated!
 
Gavin said:
Morning Folks, I'm wanting to find out a few things on my engine. I have a 350 SBC with Dart Vortec heads, and this engine has a 220/224 duration @ .050, .495/.502 lift with 120 Lobe separation. I have the Edelbrock 1406 carb running it. My questions to you all would be What is the best base timing (10* ?), what vacuum should I be looking for (15-17 Hq ?) and at what idle RPM (550-650 ?) Any suggestions would be greatly appreciated!
Click to expand...
You Tune the Engine to what it wants not what you want.

8 to 15 degrees BTDC Initial timing is typical for a SBC at idle 650-900 RPM.
With mechanical advance total timing at the crank checked with a good timing light will be typical 28- 39 degrees BTDC.

Some engines like a Pontiac V8 with reworked Edelebrock heads and modified combustion chambers want just 21 degrees total timing BTDC.

Vacuum advance is used by factory for fuel economy purposes & part emissions.
Can bring total Initial + mechanical + Vacuum advance to high as 52 degrees BTDC. Oldsmobile did it this way in mid 1970's with the 403 engine.

We do not have a good way to compute or calculate predicted engine vacuum with a chosen cam profile.
Have to go by personal experience using same grind or similar cams.
Should pull 15 -20 inches the cam with 120 degree lobe separation angle.
 
With a 120 degree LCA the SBC Vortech may run great on 87 octane gasoline.
Pick a fuel you want to tune with octane level.
87, 89, 91, 93 RM/2.
 
I appreciate your input, I'm hoping someone has this combination or very similar that can provide what they are experiencing for comparison. I've been working with mine to see what she likes the best.
 
maybe this may help
http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/
Chart-282122363.gif

camcomp.jpg


https://www.hotrod.com/articles/0607phr-camshaft-basics/

http://garage.grumpysperformance.com/index.php?threads/camshafts-8-lessons.5154/

http://garage.grumpysperformance.co...ectly-and-get-it-to-last-cam-install-info.90/

http://garage.grumpysperformance.co...mbers-or-a-good-street-combo-your-after.5078/

http://garage.grumpysperformance.com/index.php?threads/semi-fool-proof-cam-sellection.82/

http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/

0607phr_11_z+camshaft_basics+lobe_centerline_angle_determination_chart.jpg

http://garage.grumpysperformance.com/index.php?threads/calculating-overlap-and-lsa-or-lca-etc.480/

http://garage.grumpysperformance.com/index.php?threads/cams-explained.324/
 
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