What he said.
Tuning my 383
Thread Starter
Melting Slicks
Joined: Oct 2011
Posts: 2,748
Likes: 90
From: Sacramento California
C2 of Year Finalist (performance mods) 2019
2018 C2 of Year Finalist
Tuning my 383
After a year and a half of fiddling, I am ready to begin tuning my 383 for best performance.
As a refresher, Its a .040 bore 3.75 6" rod 388. 11:1 (10.8 actually I believe) AFR aluminum 195 Eliminators. 237/237 .560/.560 110 roller cam with 1.6 rockers. (.590 total lift). Z28 intake, Holley 750 vac (3310) with mildly ported factory 2.5" exhaust manifolds and true duals. Car is about 3200 lbs with a 5spd and 3.73s. Its in a 63 vette.
Timing is currently set at 10* initial and 26* with mechanical.
I have about 17" of vacuum at idle.
I have a B2 advance can, but don't believe its providing any advance at idle.
The car runs fine as it sits. Spark plugs are nice and toasty brown.
It has tons of torque, but perhaps the throttle response could be crisper?!
Where to start? Timing advance? Jetting?
As a refresher, Its a .040 bore 3.75 6" rod 388. 11:1 (10.8 actually I believe) AFR aluminum 195 Eliminators. 237/237 .560/.560 110 roller cam with 1.6 rockers. (.590 total lift). Z28 intake, Holley 750 vac (3310) with mildly ported factory 2.5" exhaust manifolds and true duals. Car is about 3200 lbs with a 5spd and 3.73s. Its in a 63 vette.
Timing is currently set at 10* initial and 26* with mechanical.
I have about 17" of vacuum at idle.
I have a B2 advance can, but don't believe its providing any advance at idle.
The car runs fine as it sits. Spark plugs are nice and toasty brown.
It has tons of torque, but perhaps the throttle response could be crisper?!
Where to start? Timing advance? Jetting?
Last edited by DucatiDon; Jan 23, 2018 at 08:28 PM.
Team Owner
Joined: Jan 2006
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From: Crossville TN
Save yourself a lot of varying opinions. Send an e-mail to Lars Grimsrud at V8FastCars@msn.com and ask him the same questions. He is an expert tuner of engines and has intimate knowledge on carb tuning. I think he will advise you well to get the most out of your setup.
Safety Car
Joined: Oct 2004
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From: Youngstown Ohio
I'd nail down the timing first. Your 383 is similar to the one I had. Mine ran best with 36° total @ 2500 rpm. Dist. was recurved for 14° initial advance with 22° mechanical. Once you're satisfied with your timing, then move to the carb.
Melting Slicks
Joined: Dec 2009
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From: Thunder Bay
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Thread Starter
Melting Slicks
Joined: Oct 2011
Posts: 2,748
Likes: 90
From: Sacramento California
C2 of Year Finalist (performance mods) 2019
2018 C2 of Year Finalist
Current timing specs:
12* idle
+24* mech
= 36* total all in by 2500
Vac can B28 which should give me +16 (but is limited by the adj plate to 14* I think...Ill have to double check it)
12* idle
+24* mech
= 36* total all in by 2500
Vac can B28 which should give me +16 (but is limited by the adj plate to 14* I think...Ill have to double check it)
Thread Starter
Melting Slicks
Joined: Oct 2011
Posts: 2,748
Likes: 90
From: Sacramento California
C2 of Year Finalist (performance mods) 2019
2018 C2 of Year Finalist
It could be the characteristics of a vac secondary carb vs a double pumper as well. Nothing a slip of the clutch cant alleviate for tire spinning grins.
Team Owner
Joined: Jan 2007
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From: Southern Cal Ca
St. Jude Donor '22
at 36 and have another 14 at cruise for 50?
are you pinging?
i know the general thinking is all mechanical in by 2500.
i still have not seen you write anything about
what the motor is doing and what you would like it to do?
Tech Contributor
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From: At my Bar drinking and wrenching in Lafayette Colorado
Lars
Last edited by lars; Jan 23, 2018 at 09:40 PM.
Had a 1976 L-82, 4-sp
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Lars has given you a starting point but for best performance tuning I would install an afr sensor/gauge and a programmable distributor. This will allow for easier adjustment for retarding mech'l advance and increasing initial advance. I think your initial will end up around 20* give or take a degree or few to get best performance that you seek. Also, try a timing curve with 32-34* total in the range of 2500-3000 rpm.
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
I agree that the total timing with your heads should be about 32 - 34, not the conventional 36. I just reread your engine specs, and those AFR heads will need less than 36 total. 
Thread Starter
Melting Slicks
Joined: Oct 2011
Posts: 2,748
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From: Sacramento California
C2 of Year Finalist (performance mods) 2019
2018 C2 of Year Finalist
I have the vac adv limiter plate.
The task before me is to try to limit the mech advance and increase initial.
Fun fun.
The task before me is to try to limit the mech advance and increase initial.
Fun fun.
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Modern chamber designs and higher compression create very high pressures with all in mechanical advance at sub 3000 rpm. The so called gurus that tell you all in at 2500 are old lost in the 70's smog motor sub 9 to 1 compression era.
Like other said 18 - 20 initial and max at near 32 especially since you are right at sea level and California 91 max unleaded.
I really don't believe or have not seen a dual plane intake manifold that has the same port size and AFR 195 heads. The mismatch will cause port velocity and fuel atomization problems.
Like other said 18 - 20 initial and max at near 32 especially since you are right at sea level and California 91 max unleaded.
I really don't believe or have not seen a dual plane intake manifold that has the same port size and AFR 195 heads. The mismatch will cause port velocity and fuel atomization problems.