Between 36- 40 degrees, gasoline ,no adders.

 

for your tipical BBC that mild to fairly hot but nothing crazzy like an 8 second street fighter i would run 36-38 deg max total timing not including vac advance.

Closer to 36 deg total if you only have 91 fuel like in CA.or up to 38 deg total if you have 93 fuel.

I have a mild camed 69 396 now 402 with approx 9;6-9:8 comp running stock cast high rise intake,stage 2 modified q-jet,stock sextrude honed ex maifolds,flowmasters,2.5" pipes.

I run arrrox 17-18 deg intial advance with total of intial & mechanical of 38 deg btdc not inc vacuum advance.

My cam is farily mild (too mild but too late now) flat tappet hyd cam with 222/226 deg dur @ .05,.525/.525 lift,112 deg L/S angle.

Scott

 

I should have been a little more specific, we are talking naturally aspirated, street/strip bbc combos..Please keep commenting even if you're restating the same information..

Please keep them coming,
Scott

 

35-38* under normal conditions

 

Mine seems to run best at 40* total, 93 octane fuel. John

 

36º-38º total is optimum for most apps but some aftermarket heads may like more/less. Don't be fooled by seat of the pants power improvement you can get with too much total. More total often provides better torque/hp BEFORE total is all in, which may be more noticeable than the power loss once total is all in. For example, if you have 6º more total than optimum (for best peak power) that 6º might add 10hp at 2k rpm but it costs 20hp at 5k. If the engine makes 150 hp at 2k and 400 hp at 5k with optimum timing, the improvement at 2k is going to be more noticeable than the loss at 5k. End result is that it will "feel" more powerful but will be slower at the strip. The cure is to curve the distributor so that you have as much initial as is practical for your particular situation and that total comes in as soon as your combination allows.

 

38-40 on 110 race gas. But I know some are certainly lower normally asp. Just adjust where your engine runs best without detonation and best ET!

 

BBCs tend to like a bit more timing IME. Larger bore size, chamber, and oftentimes domed pistons require additional timing.

My flattop closed chamber 10.2-1 505 seemed to like 38* locked out. Ran fine on 93. Had a 248/254 solid roller on a 112 LSA. (sold the car before I ran it)

My 9.6-1 427 with domes and open chambers also likes 38* (best ET). 228/228 hyd flat tappet with 112 LSA.

I've messed with some combo's (bigger domes, open chamber, race only) that liked 44* (best ET).

So I would say 36-44* is the typical range for a BBC.

 

38 degrees with 90 octane fuel.

 

Thanks for the info, that's exactly what I needed.. My brother-in-law was trying to tell me that my motor should have NO MORE then 34* of total timing.. Hell, my car wont even run at 34*:clonk:

He's getting his data from a book from 1970, oh the times, they are a changing

Thanks again,
Scott

 

40 with GM iron heads, 9:1
38 with Canfields 9:1
38 with Canfields 10:1
? with AFR's 10.9:1

All with 93 fuel

 

38 degrees...locked.

 

Thousands and thousands of years ago, when I was in High school, we ran the timing at 38--42, maybe even experimented at 44. (then add in the vacuum advance) Nothing blew up, and they "seemed" to run pretty good. Now that's considered "way too much"; and I don't doubt that Jerry 70 is correct: We enjoyed low and midrange torque but sacrificed up on top.

The Gen 6 L-29 heads want no more than 30 degrees, (plus vacuum) with massive torque losses if you add more. (according to an article in the Chevy Thunder GMPP supplement to Chevy High Performance)

 

I run 38-40 total.
I have 8 degrees at the crank in the distributor.
So initial is 8 degrees less than the total.
Dyno showed 41 deg best, but 38 works best at the track.
This is a 93 octane pump gas combo.

Ron

 

I have mine locked at 40.

 

MIne is locked at 37*, where it made best power on the dyno. I have seen engines with very similar combos, that liked anywhere from 32*-38*. These are high compression race gas engines with heads that have been angle milled. No way to know what will work best without testing. Ball park to me is between 34-40*.

 

Azzdyno seems to think the 427 preferred less than 38, but its never been track tested. Ran 17/35. New iron heads will monkey with that .

 

40 with GM iron heads, 9:1
38 with Canfields 9:1
38 with Canfields 10:1
? with AFR's 10.9:1

All with 93 fuel

My son's 598 seemed to like 37 degrees with the AFR heads.

 

38 here. The '69 and '70 Chevy Service Manuals spec from 30 to 36 initial plus mech, depending on engine. Most performance engines were spec'd at 36.

 

I'm going to show him these results, but I can already hear him saying that none of know what we're talking about :clonk: :clonk:

 

My son's 598 seemed to like 37 degrees with the AFR heads.

Thanks Harold, I planned to start at 36

 

I'm going to show him these results, but I can already hear him saying that none of know what we're talking about :clonk: :clonk:

So what does he say? does he understand the concept of what total timing is or is he just misinformed to what each timing setting means?

 

i found 36 is a sweet spot for most street bbc's

 

Thanks Harold, I planned to start at 36

On the motor the car ran 9.41 with 35* and picked up a tenth to 9.31 at 37* on the only two runs we made on the motor. Both speeds were relatively the same at 145.44 and 145.59.

 

I'm going to show him these results, but I can already hear him saying that none of know what we're talking about :clonk: :clonk:

The race gas definately burns slower but the big block Chevies have large domes and big combustion chambers which require quite a bit of timing. Most average open chamber combustion chambers are in the vicinity of 118 cc and that is the reason for the big timing. Tighter combustion chambers would need a little timing as a general rule.