Timing curve for BBM heads

[chilly460]

Getting ready to put a new curve in my MSD distributor with the BBM heads in mind.  4100lb car, 4.10 gear, TKO 500 5spd with 3.3x first gear.  Cruises 2200, no issues finding 93 oct, 9.2:1 CR with a 224/230 cam on a 104ICA

Previously I ran 14* initial, 37* total, in by 2900 with no issues, Edelbrock heads. 

My understanding, the BBMs are likely to like 32-34*?  My CR is low so can probably use a bit of initial, but fairly heavy car and fairly low RPM range with some load pushing O/D on the highway. 

Thinking of keeping 14-16* initial, use the Black (I think off top of my head) bushing to give 18* mechanical advance, gives me flexibility to run it at 14/32* or 16/34* depending what it likes.  I'll have it come in fairly quick, by 2900 or so. 

Any thoughts? 

[fryedaddy]

i run 15 int and 33 total with a lite and med spring and black 18* bushing,all in by 2600-2800 in my 433 with bbm and msd pro billet.it fires up before you can get your finger off the button.i was advised to run 33 total buy a couple of the main engine builders on this forum and it seems to be working good on the street.i run it almost every day and it starts good hot or cold

[Drew Pojedinec]

I run 22 initial 32 total, it's in around 3200rpms.

Works for me.... I have a pretty high stall convertor and deep gears tho.

[Stangman]

22 initial how does it start hot or should I say after a. Hot soak Drew. I’m at between 14 and 16
What heads are you running

[Drew Pojedinec]

BBM.
AGM battery, good cables, powermaster mini starter.  10:1 compression, etc
Starts fine in all conditions.
If I leave it idling forever here in the deep south on a hot day it'll get up to 210 and sit there.  Most of the times it never sees over 200.
Took a lot of tuning work both with the distributor and carbs to get it to where it is.

here is a folder with the engine build thread:
https://www.facebook.com/pg/AirFuelSParkTech/photos/?tab=album&album_id=173319843406755

[Stangman]

Very nice Drew, mine starts up well at 16 just never tried to go any higher.

[Drew Pojedinec]

Very nice Drew, mine starts up well at 16 just never tried to go any higher.

On my daily driver 390 I only run 16-17 as it honestly can't crank any more than that.

With my car: it's been my experience with 2x4 carbs that anything more than a tiny tiny tiny bit of the transition slot is exposed the engine will pull enough fuel to hurt your eyes and blacken plugs.
Running more initial makes it to where I can close the blades more.  Idles cleaner, runs cooler, etc.  On mine I'll even close the secondary carb to where no slot is showing and just barely visible on the primary carb.  I set idle speed with the secondaries, the carbs I'm using have the leak hole at the bottom of the secondary transition slot, so it'll still pull from there.
Once I get that set up and the idle mixture screws 3/4-1 turn out I set idle richness with the secondary IFR.  Even the exact same calibration and it'll vary between .033 and .040 so I generally just either put a 4-40 set screw in there or I start at .033 and drill until it idles where I want it to.

Or so I heard

[Stangman]

Ya know I tried the whole transition slot thing and it never works out for me i guess I
just got used to doing it the traditional way.