Blower Timming Question, need Help!!

Hi everybody

I have this setup in my 49 monarch..

383 Block Dart
JE Piston 8.1 CR
Crank Forged 4340 Eagle
Dart Iron Head 215cc - 72cc combustion chamber
2.050 Valve
1.600
1.550 Spring

Camshaft Lunati 01007 - Hudraulic Flat Tappet - 2,600-6,500rpm
Intake Lift : 509 - Exhaust Lift: 533
112 lobe center

6-71 Weiand Blower
Blower Pulley Top 38
Blower Pulley Bottom

2 Carburetor Holley supercharger 4150 600cfm Carburetor

I have a couple of question. First

What spark plus should I used ?
Second question, Where I'm supposed to set the timming at?
Initial Timming?
Distributor Timming?

I have a MSD 6BTM to retard timming on boost...where i,M supposed to put it if I want to run on the street

Here we have 91 octan gaz (It's a street car)...does the pulley are setup correctly or it's better to inverse them?

If I Go to the drag strip...what setup of pulley is the best and Do I need race gas??? (on what retard I have to put the MSD 6BTM, and the distributor)

Thanks in advance to help me...I'm about to start the car.

really nice to help me!!!!

Stephane


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What are the tooth counts on each pulley? Top is a 38?? Without me looking it up, it that blower 8 mm or 1/2" pitch pulleys?

__________________
''Life's tough, Pilgrim, and it's even tougher if you're stupid.''---John Wayne

Midnight Sun Street Rod Association

1/2 Pitch Pulley

Top 38
Bottom 34

Do you need other information my friend? Thanks to help me!!!

Forgot to tell;

Automatic Transmission 700R4
3.73 Rear Gear
2500 Stall converter

Thanks stpehane

On my motor, 383 8-71 @ 9 to 12 #'s boost. I'm running two BG 750 Blower Carbs. Timing initial 22 total 38 all in at 25 to 2800 RPM. Mechanical advance MSD dist., 6-BTM and haven't pulled any timing out yet, however I am running pretty rich.

I'm having an Innovate wideband delivered today and will adjust my AFR, then possibly make some changes in timing.

Running 31" tire with 4:11's, T-400 3200 stall.

__________________
''Life's tough, Pilgrim, and it's even tougher if you're stupid.''---John Wayne

Midnight Sun Street Rod Association

Are you running pump gaz??? (91 octan)

You'll find the blower and fairly long duration Lunati cam want lots of spark timing at idle, But you don;t want a lot of timing while under full boost.
You'll find 28-30° static locked timing works very well as a safe starting point.

Leave the BTM box disabled or set at 0° (no boost retard) to start.

Start with the distributor advance curve locked out. Set the timng at 28°-30° and work from there. What is the tooth count top and bottom?
If the 600 holleys have not been properly set up for a blower, you will need to do that. (boost referenced power valves, jetting, PVCR adjustment, air bleeds tuning.
A wide band AFR meter really helps. Start rich. rich jetting and conservative timing saves pistons.
91 octane gas sucks. Use the best available.

Once you have got the the carb jetting and timing right (under boost), you can proceed to create an advance curve and employ the BTM box to trim off spark lead as the boost comes up and you get into the throttle.
High boost (beyond around 10LBS) will require high 110++octane race gas.
The high octane gas allows you to run high boost (blower drive ratio) without the requirement to retard the timing under boost.
Don;t confuse the two. 91 octane requires conservative (retarded) total spark lead under boost and somewhat rich(er) jetting. while race gas allows full power producing spark timing under hi boost.

What is the normal spark plug type number suggested for your heads?
From that I can suggest a good plug for your supercharged motor.
if your heads use a 14MM .460" reach plug with a 5/8" hex, like a AC R44TS, then start with a AC R42T or champion RV8C. gap at .035"

Consider a water/methanol injection system if you want to run high boost on street pump gas and make lots of reliable power. very effective.
Google it.

The torque converter stall is low. The th700r4 overdrive offers no advantage over a th350 in your application. When the Th700r4 gives up the ghost, replace it with a th-350 or th400 and a 10" (3200-3500 stall) torque converter.

Yes, I'm running pump gas, and aluminum heads. 91 octane gas isn't bad in this day and age. With a proper tuneup ten pounds of boost isn't a lot either, and does not require "110++ gas", don't cheat yourself pulling a ton of timing out, just dont run lean.

__________________
''Life's tough, Pilgrim, and it's even tougher if you're stupid.''---John Wayne

Midnight Sun Street Rod Association

if I have 2 - 600 Holley Blower carb...are they not alredy tuned for initial start-up ????

Top pulley is 38
Bottom 34

if I have to lock timming at 28-30....what initial timming I need...??

Thanks to give me a answer.....

Stephane

If I have 2 - 600 Holley Blower carb...are they not alredy tuned for initial start-up ???? if you have the blower carbs, they should be close for start up.
flip them over and preset the throttle blade/transfer slot exposure .015".020"
on all 8 barrels before install.
The vacuum lines for the boost referenced power valves connect to the intaqke manifold below the supercharger.

Top pulley is 38
Bottom 34 good to go

if I have to lock timming at 28-30....what initial timming I need...??
The distributor advance curve would/should be "locked out" and will not move with rpm. If its not locked out, do that...then.... Set the intial timing at 28deg for start up. Set the boost retard box on "0"

What jets are in the carbs now? do they have replaceable air bleeds?
What power valves?

make sure the cooling system and the engine is full of water. Fire it up and with the rpm at 2000+, set the (locked out) spark timing at 28deg with a timing light. Do not wack the throttel open with a cold blower. it will back fire.
warm the engine and break in the new camshaft at 2000-3000rpm for 25minutes.

Again do not wack the throttle open with a cold blower or you will get a free haircut. Once the cam is all broke in, shut it off,let it cool off.
Restart and adjust the idle mix screws all even for best idle around 1000 rpm.
You should not have to touch the throttle adjsutment ( idle speed adjsutment) much at all, if you preset the throttles basic idle setting before start up as discribed.
You cannot set up the idle mixture screws until the engine and blower are nice and warmed up.
make sure the engine and radiator have lots of cool airflow when running the motor to break in the cam.
If the rocker arms do not quiet down within a few seconds of starting the motor up, stop, shut it off and reset the loose rockers, (valves closed), then restart and finish the cam break in cycle.

The "just don't run lean." is my concern. It would sure be nice to know the cylinder quench, and the cranking compression of this combination setup to be able to advise more precisely on the tuneup.

135 to 145 cranking compression is more suitable for street, and strip applications. A 170 cranking compression SBC 383 running a 1-1 blower gear ratio, and the max timing of 38 degrees all in by 2500 RPM needs to run a 50/50 mix of 110 and 91 pump gas on the street hitting 20lbs of boost only occasionally. This will keep it from detonating with the 6BTM set at 1&1/2 degrees per pound of boost. To run this cranking compression at the strip is not recommended, but pure 112 race fuel, a richer mixture, and 4 degrees less base timing, and the close to the same degrees of boost retard might work as a starting point on tune.

Keep in mind the higher the cranking compression, the lower the longevity of your engine is.

Not saying it can't be done, just be careful.

i run 12* ini and 18*in the distrib locked for a total of 30* but my motor is 8.4.1cr and i run 7lbs of boost so my final CR is around 12.4.1 thats pretty much max CR for pump gas im in FL so we have 93 as for spark plugs i run NGK with a #8 heat range i run my timming on the safe side because i dont run a BTM yet

Thats not "locked" Locked out timing is when the mechanical advance in the distributor is frozen or eliminated.
With locked out timing you would set the inital timing at idle to 30degrees.
It does not advance with rpm. 30 at idle, 30 at max rpm.

Street supercharged motors running on 92 pump gas 7 to 12 lbs boost, with big duration cams (240°+@.050), and no boost retard, like this kind of setup.

The big cam duration wants lots of spark timing at idle.

High octane 110+ gas allows more timing and power.

the timing in the distributor is locked at 18* i changed the springs and weights so the machanical advance does not go past 18*