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Ok I have a really stupid question that I need answered.
With a BBC that is a little hot.
Where do you set the Initial Timing?
I keep seeing people settting their small blocks with 12-14 degrees of initial timing. And on all my BBC I have always been taught 10-12 at the most. Is this correct?
8 to 10 is a good start. :cool:Quote:
Originally Posted by 4speedTerror
How much do you have built into the distributor?
What is your total timing?Quote:
Originally Posted by 4speedTerror
I need to hit it with the timing light again.
The car just recently started back firing through the carb as soon as the secondaries kick open. It will pop, have a milisecond bog, then the car runs like it always use to.
Before, the transition to secondaries was smooth. Now it pops, and then hauls ass.
So i am looking at the fuel delivery right now. The bowls are set right in the middle, and i just rebuilt the Demon.
Motor is 496 roller
11:1 static
MSD HEI with 6AL
Pro Topline Heads 320's with worked 11/32 valve stems
Demon 850 Mech. Sec
Timing right now is set at 10.....I will post total timing tonight.
110 low lead race fuel mixed with 93 from the pumps (60% leaded with 40% pump)
I use to have 12 degrees in the motor with strictly race fuel, but it would detonate through the intake. I rolled it out to 10 and now it only does it at a heavy load. IF i gently and gradually put the pedal to the floor, it runs great. But if i floor it from a stop, or a slow roll it pops, bogs, and then boils the tires and its like the car is on glass.
I used to have this thing running 10.80's with 10.5's out back and my CalTracs. Now she is kinda sick.
So I am going to check fuel pressure at about 3,000 rpm on the road. So i will start there.
any other ideas would be great
thanks guys
I hope your not still using pump gas! Another thing I would look at is Valve timing, if this thing has been sitting around awhile, try Degreeing in the cam to spec and be sure. Then most important, use timing tape on the damper and time your rat to 38 degrees total advance, then at the best idle you can get with vacuum unhooked, check the initial ignition timing on the tape at the Vibration Damper. And there you have it, the magic timing mark for your very own Rat Motor. All kidding aside...page 2-22 in the Chevrolet Power Service Manual, (otherwise known as the Chevy Power Book) typical spark curve for a big block chev racing engine is 38 degrees at 3000 RPM. Now this is total timing advance, so be sure to have vacuum hooked.
LOOSE THE MSD HEI! USE A BILLIT RACE DISTRIBUTOR,W/HVC&6AL BOX.
SET THE CURVE &LOCK OUT THE DISTRIBUTOR.36-38 DEGREES IS GREAT@3000RPM.
A .688 ROLLER WOULD BE GOOD W/260-270 DURATION@.50 112LC/@110CENTERLINE.DEPENDING ON YOUR ROD TO STROKE RATIO.
RIGHT DOWN ALL THE SPECS ON THE ENGINE AND GET BACK TO ME.
IVE GOT AN EL-CAMINO W/A500"BBC SET UP ALOT LIKE YOURS. I HAD IT DOING FLAT 10's @9:1CR. IVE GOT ALOT MORE TO TELL YOU IF YOUR INTERESTED. I HAD THE SAME PROBLEMS YOUR HAVING.
I have had nothing but big blocks for the last 9 years, and not a single one that was built up a little, or a lot, would run good with any less than 18* initial. (without vacuum of course) You still want your total at 38*. You shouldn't have detonation problems with 11/1 and hi octane fuel, so there must be something else happening. What's your dynamic c/r?? What are the cam specs?
[quote=1JohnnyO]I have had nothing but big blocks for the last9 years,----------- :eek: only 9years who let them damn kids in:LOL: better late than never:3dSMILE: i have had them back 1980 and there is not a day that i do not see one or think about one or work on one. i like to have some around just in case:3dSMILE:hate to run out .you can run 12 on the crank and have it all in just before 2500 i have had many and tune many every one may likes some thing diff so play with it you can try more on the crank the only way to find out this to try this msd dist red bushing blue spring one lite sliver 12 on the crank all in at 36 try that. if that will not do it then try two lite slivers .did the damper outer ring slip? you do have a sfi damper??? are you sure your at TDC