Vette(s): '68 Corvette with Engine Factory 383 Stroker
I need to set the timing on my 383 Stroker. I bought the crate engine from Engine Factory. They told me to disconnect vacuum advance.
At 3000 rpm set 32° btdc
At idle 12° btdc Does this seem correct? When I look up instructions on line, none mention disconnecting the vacuum. Is this common knowledge? 32° seems like a lot. Thank you for any response. Mark
Thats probably very close. My 350 I have set at 35* at about 3300 RPM's and at idle its at 14*. Both settings are with the vacuum disconnected. I came to 3300 RPM's as thats where my timing stops advancing as I increase my throttle. There are so many different methods and this is the one I used. Good luck with engine. Rodney
Vette(s): 1972 conv., sunfire yellow, blk interior, blk vinyl and convertible top. Off frame restoration with American Speed 383 stroker engine producing 500hp plus a 200hp NOS system. MSD ignition. Hooker super competition headers with chambered exhaust.
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
[QUOTE=rod7515] I came to 3300 RPM's as thats where my timing stops advancing as I increase my throttle. [/QUOTE]
That's the key...you have to include the total mechanical advance in the reading. If your dist still has more mechanical advance happening after 3000 rpms, then you timing setting is gonna be off. You must determine where(what rpm) the mechanical advance stops...that's where you want to do the calculation of initial + mechanical.
Ben(cthulhu) is really good at figuring this stuff out...perhaps he'll see this and give an opinion.
____________________________________ Joel Adams C3VR Lifetime Member #56 My Link
Vette(s): 70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe
In dyno test after dyno test, traditional small blocks with traditional style heads run best at 34 to 36 degrees total. That is with vacuum disconnected and plugged, and after all mechanical is in (like Joel described). A stock distributor will probably have more than 20 degrees mechanical built in, so either modify the stop, or ignore the idle advance and just use the top number. If you have poor off-idle performance, you might be forced to modify the distributor.
This is an old thread so the problem is likely solved by now... but for the record... figuring out the correct timing when the distributor is "all in" is a very small portion of properly setting timing.
Any fully maximized tuning will require changing springs to adjust ramp rate and optimization of idle timing for best off idle response.
a fairly typical chevy sb with a typical distributor and typical cam profile will typically do well using the 34-36 at 3300.
thats a whole lot of assumptions and generalizations. Ive written a few very long detailed posts here about optimizing timing through all rpm ranges. not just the top or "all in" and not just the bottom or idle.
basically I sent the bottom end at the minimum advance to achieve peak vacuum then use various springs to adjust the ramp rate to achieve optimal perfomance.
the vac advance is intended to add appx 15 degrees of advance when the engine is not under a load, ie cruising. this is strictly an emissions/mileage enhancer without any real detrimental effect on performance.
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