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 Post subject: BBC timing
 Post Posted: Thu Feb 23, 2012 9:32 am 
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I'm just curious as to what you guys that are running big blocks with conventional heads are running for timing. I had my motor at 36*, but I've been told to run 38*-40*, especially with the altitude we have here in Colorado. I'm planning on starting at 38* and playing with it a bit, but I just wanted some ideas as to what others are running.

Thanks guys!!!

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 Post subject: Re: BBC timing
 Post Posted: Fri Feb 24, 2012 6:55 pm 
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Nobody has any input??

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 Post subject: Re: BBC timing
 Post Posted: Fri Feb 24, 2012 7:01 pm 
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Mark, My 540 made it's best power at 36* more than that power went down alot...I think it mostly depends on how big the dome is and how big the motor is,,big motor usually does not need a lot
of timing...

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 Post subject: Re: BBC timing
 Post Posted: Fri Feb 24, 2012 7:55 pm 
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Mark,
I agree with Barry, the bigger the bore, the smaller the dome, the better the flame travel, the less advance needed. My 427 with TRW 12.5 pistons (big domes) and 990 heads made best power at 44*. I think combustion chamber shape and cam timing are a big factor, but I think your AFR, whether you are a little rich, a little lean or right where you should be, has a bigger affect on timing than most realize.

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 Post subject: Re: BBC timing
 Post Posted: Sat Feb 25, 2012 1:04 am 
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My 489 BBC is around 36 or 38, I was waiting to check it this weekend before I replied. If I do get to run it, I'll confirm it. It has Dart Pro 1 heads and SRP large dome pistons for about 12.8 CR.


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 Post subject: Re: BBC timing
 Post Posted: Sat Feb 25, 2012 11:00 am 
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As has been said it is depends on chamber design, dome size and displacement. Then there are fuel differences.

I don't mess with BBC's much but a friend who raced a 468 w/open chamber factory heads (ported) and a big dome needed 42º.

Others can give you a guide, but unless they have ran the same heads, pistons, displacement and fuel you can't say that's what yours will want. Testing is the best method.

Rick


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 Post subject: Re: BBC timing
 Post Posted: Sat Feb 25, 2012 1:02 pm 
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rick360 wrote:
As has been said it is depends on chamber design, dome size and displacement. Then there are fuel differences.

I don't mess with BBC's much but a friend who raced a 468 w/open chamber factory heads (ported) and a big dome needed 42º.

Others can give you a guide, but unless they have ran the same heads, pistons, displacement and fuel you can't say that's what yours will want. Testing is the best method.

Rick



Thanks for the input guys. Rick, all I was looking for is a general "area" that others are running. I know there will be countless differences in combos, but if I can identify even a slight trend, that helps. I know guys here running as low as 32* and some as high as 45*. To me, that' just too large of a gap to try and tune through, hence my posting to see what others are running as well. So far, the general range is from roughly about 36-40*, and that's a much narrower range for me to play with. I do plan on making some tuning changes this year and testing them on the track, I just wanted it to be a smaller "target" to work with, and now it is. I've changed several things with my combo as well, and it's more along the lines of what's "common" these days. Still different in it's own way, but not so far out of the box this time that I had to start from scratch.....

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 Post subject: Re: BBC timing
 Post Posted: Sun Feb 26, 2012 10:43 am 
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I've also found that LONG stroke engines seem to like LESS timing. Proved that with a iron head 406 TRW engine years ago. I'd always been a 40* guy on SBCs but the 406 liked 35* with all else the same.

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 Post subject: Re: BBC timing
 Post Posted: Mon Feb 27, 2012 8:36 pm 
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Thanks for the info guys. Good luck to everybody this year!!!

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 Post subject: Re: BBC timing
 Post Posted: Mon Feb 27, 2012 9:11 pm 
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In testing you really should make a 4* change per run and once you find the high and low boundaries change 1 or 2* per run to find the sweet spot. Most likely it will be between 35 and 42

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