383 with tunnel ram wants 30 initial timing

[mouserider]

Sorry for posting that much, but im here alone trying to get my charger properly set, and due to where i live, there is no one can help me.

So, long story short, again
383, tunnel ram, 204 0.5 cam, holley sniper efi 2x5. Car is bogging on acceleration even since carb setup.
So today i finally got my vacuum gauge from amazon, got the reading 13hg at idle (no wonder my brakes was super hard)

my initial timing was set at 15, so i have decided to tune it with vacuum gauge, so i was advancing it till i got almost 17hg, engine sounds way better, checked timing with timing light, gosh its 36.

either i have bad balancer or....

anyway, is it a proper way to adjust timing to the highest vacuum? should i just give the engine what he wants? even if balancer is wrong? I didnt check total, im just scared that with such a high timing (in case balancer is ok and timing is really that high) total will be too much and might damage the engine.

Please advise

 

[RemCharger]

Yes, sometimes you have to, especially with 340s and 383s. But at that point you would lock out all forms of advance.

I hate to say it, but you can try knocking the initial back down and hook up the vacuum advance to full manifold vacuum. It's a cheesy chevy bandaid, but may help in your situation...

 

[Gunner1]

Is your cam 204 degrees at .050? Lobe spread and compression? Also cranking pressures if you have them. Most tunnel rams have a lot of plenum volume which could need more fuel enrichment on accelerating

 

[mouserider]

Yes, sometimes you have to, especially with 340s and 383s. But at that point you would lock out all forms of advance.

I hate to say it, but you can try knocking the initial back down and hook up the vacuum advance to full manifold vacuum. It's a cheesy chevy bandaid, but may help in your situation...

oh, forgot to mention, i have msd box with billet distributor, so there is no vacuum advance. So you say that in some specific situations such a timing might be ok to go?

Is your cam 204 degrees at .050? Lobe spread and compression? Also cranking pressures if you have them. Most tunnel rams have a lot of plenum volume which could need more fuel enrichment on accelerating

yes it is
here are specs
ntake Duration at 050 inch Lift:
204
Exhaust Duration at 050 inch Lift:
214
Advertised Duration:
270 int./280 exh.
not sure what you mean by lobe spread, here is my cam Edelbrock 2192 Edelbrock Performer-Plus Cam and Lifter Kits | Summit Racing

yes, i know about fuel enrichment, thats another step to tune, but firstly i wanted to make sure timing is good, before proceeding, im now on EFI, so next step to play with base fuel map.

 

[Gunner1]

Ok that’s a pretty common mild performance cam on a 112 lobe spread. Should be a real torquey motor. 5 to 55k top end. How does it start with 36. If it spins up easy then you could lock it at 36 with no additional advance. My guess is things will change when your fuel map gets closer to optimal.

 

[Don Frelier]

I would think the Sniper can control advance.
You should set it up so the EFI system controls the advance.
30 degrees is where my 383 with MSD atomic likes to idle.
The maximum on the atomic is 42 degrees I would actually like more during cruise.

 

[mouserider]

Ok that’s a pretty common mild performance cam on a 112 lobe spread. Should be a real torquey motor. 5 to 55k top end. How does it start with 36. If it spins up easy then you could lock it at 36 with no additional advance. My guess is things will change when your fuel map gets closer to optimal.

starts and idles like a champ with highest vacuum i ever seen, but havent drove it yet. can you please guide me how to lock the advance?

I would think the Sniper can control advance.
You should set it up so the EFI system controls the advance.
30 degrees is where my 383 with MSD atomic likes to idle.
The maximum on the atomic is 42 degrees I would actually like more during cruise.

my sniper is set with no timing control yet, im waiting rotor cap to get it connected. then yeah sure i will move to ecu timing control.
thats nice to hear, so i might be on the right way!

 

[67_satellite]

Sorry for posting that much, but im here alone trying to get my charger properly set, and due to where i live, there is no one can help me.

So, long story short, again
383, tunnel ram, 204 0.5 cam, holley sniper efi 2x5. Car is bogging on acceleration even since carb setup.
So today i finally got my vacuum gauge from amazon, got the reading 13hg at idle (no wonder my brakes was super hard)

my initial timing was set at 15, so i have decided to tune it with vacuum gauge, so i was advancing it till i got almost 17hg, engine sounds way better, checked timing with timing light, gosh its 36.

either i have bad balancer or....

anyway, is it a proper way to adjust timing to the highest vacuum? should i just give the engine what he wants? even if balancer is wrong? I didnt check total, im just scared that with such a high timing (in case balancer is ok and timing is really that high) total will be too much and might damage the engine.

Please advise

Give it what it wants. My timing on my current engine(470) is Sniper controlled and I got the highest idle vacuum at 30 deg. initial. I have it at 35 deg. total. If I were you,for now, I would set the total at 35-36deg. and hook the vac. advance to manifold vacuum.Ran my old 383 that way with a cam very similar to the specs. of yours. It worked very well.When you get the parts to use the Sniper to control the timing, you can create a custom timing curve with the laptop software.

 

[Geoff 2]

Mouse, you tuned the idle almost exactly right. 36* is not excessive. Sometimes as much as 50* is needed [ yes, 50* at idle !! ].

383, tunnel ram, bad idea. Buuuuuuuuuut you got it now......

Go back & advance the timing. Listen for highest idle rpm, not vacuum. Although both will be very close.
I tune a car for drag racing; it needed 53* at idle with a large cam.

 

[mouserider]

Mouse, you tuned the idle almost exactly right. 36* is not excessive. Sometimes as much as 50* is needed [ yes, 50* at idle !! ].

383, tunnel ram, bad idea. Buuuuuuuuuut you got it now......

Go back & advance the timing. Listen for highest idle rpm, not vacuum. Although both will be very close.
I tune a car for drag racing; it needed 53* at idle with a large cam.

gosh! maybe all my problems for the past year was just hiding behind this, i never thought timing can we that advanced. cant wait to give it a test drive.

Since you know my timing situation now. let me ask you this, so the car was bogging/stalling on acceleration like crazy, i switched to EFI, the same, then on EFI wizard i put engine displacement 500+ instead of 383, and it did help, car runs reach, yes, but it drives, no torque on low rpm, but at least it was not boging stalling. Could that be because of timing? just wondering, if it was timing, how bigger engine displacement overcome it (at least partially)

 

[Wietse]

Mouse, you tuned the idle almost exactly right. 36* is not excessive. Sometimes as much as 50* is needed [ yes, 50* at idle !! ].

383, tunnel ram, bad idea. Buuuuuuuuuut you got it now......

Go back & advance the timing. Listen for highest idle rpm, not vacuum. Although both will be very close.
I tune a car for drag racing; it needed 53* at idle with a large cam.

How you are going to dial that in for a streeter? Its not going to be an idle & full throttle situation only here.
Coming from 50 deg advance at idle, including vac advance or without?
How you think you can set a decent transition?

 

[Gunner1]

Your lucky. You can tune your system without vac cans or spinning weights. You can just go into your ignition table and build a curve that works best for your package.

 

[mouserider]

Your lucky. You can tune your system without vac cans or spinning weights. You can just go into your ignition table and build a curve that works best for your package.

You mean via sniper efi timing control?

 

[Geoff 2]

Wietse,
I suggest you read post #1 again. OP got highest vacuum with 36* at idle.

The cam is quite small, but he has an induction system with a huge amount of air space inside it & it is poorly matched to the cam. It makes sense to me that the resulting poor carb signal is going to want more timing to burn a very poor quality A/F mixture.

 

[Wietse]

My question is how you are planning to tune that in to idle with so much advance and get a good curve for the rest of the throttling?
Most of these engines will have highest vacuum with some high advance numbers, but then what?
You gonna have 36 deg incl vac can?

 

[Geoff 2]

Mouse,
I have no experience with EFI. But what you say about setting it up for a larger engine & improving the bogging situation does not surprise me. Nor does the fact that it has ' no ' low rpm tq. It has no tq because a TR intake it is not a low rpm tq intake. Because of the weak signal [ post #14 ], richening up the mixture has helped.

About initial/idle timing. Chrys missed the boat on Man Vac Adv. GM did not. They used it on production cars, 10.75:1 CR & low duration cams [ under 200@ 050 ].

My GTO was driven off the showroom floor, idling at 26*.
6*init + 20* added via MVA. Note all these settings, irrespective of car make, have to be conservative to allow for severe use by owner[ s ].

This following quote comes from David Vizard's Holley book. It is about idle timing.

So why is idle/ign timing in a carb book? Because DV ' gets it ' .

" The optimum idle advance is typically about 35-40 degrees for a short cammed street engine [ & though not commonly realized ] as much as 50 deg for a street/strip engine."

 

[Geoff 2]

Wietse,
Every adj VA can I have seen & used has a 30* range.
If the OP is using a dist for ign, he can choose any combination he likes for idle timing.
Example: the idle rpm tests shows 38* at idle is best. He can use 12* init [ static ] & add 26* with VA. If he uses 20* init, he can add 16* with VA. He will have to fabricate a stop to limit the VA plunger travel. That is what hot rodding is about. Tuning. Trying different things.

 

[Gunner1]

He said he has the sniper module for ignition he can literally set any curve he wants.