BB guys with Edelbrock\any other brand alum heads. Whats your total\initial timing?
10-13-2006, 12:14 PM
#1
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BB guys with Edelbrock\any other brand alum heads. Whats your total\initial timing?
My 10.5:1 solid Cam 454 with Edelbrock 110cc Performer RPM heads is set at 20* initial and 36* total between 28-3000. I have read all the aricles on timing and have a good feel for it. I have heard that some of the newer style heads like mine do not need as much total timing. As I posted before with these settings I feel like I have lost some power although the car runs and idles good.
What are you other BB guys running for timing with similar setups?
Thanks
What are you other BB guys running for timing with similar setups?
Thanks
10-13-2006, 01:55 PM
#3
Team Owner
I don't know alot about modern BBC heads. But if they are anything like SBC with modern fastburn technology 32 degrees max advance is what you want.
In the past i had my mallory unilite recourved to 14 degrees of mech advance. Then i would set the initial at 18 or so. I've since changed to a full electronic MSD dist. and I change my max advance and courve with small switches. I now use 15 degrees max added advance all in at 3200 rpm
From Edelbrock tech articles.
CFM and Engine Control: Spark timing must be matched to Volumetric Efficiency because VE indicates the quantity of charge in each cylinder on each stroke of the engine. Different engine families require distinctly different spark advance profiles. And even engines of equal CID but different CR require their own unique spark advance profiles. Rule: Expect 0.1% to 0.5% loss in Torque for each 1 degree error in spark timing advanced or retarded from best timing. Also, detonation will occur with spark advanced only 3 degrees to 5 degrees over best timing and detonation will cause 1% to 10% torque loss, immediately, and engine damage if allowed to persist.
In the past i had my mallory unilite recourved to 14 degrees of mech advance. Then i would set the initial at 18 or so. I've since changed to a full electronic MSD dist. and I change my max advance and courve with small switches. I now use 15 degrees max added advance all in at 3200 rpm
From Edelbrock tech articles.
CFM and Engine Control: Spark timing must be matched to Volumetric Efficiency because VE indicates the quantity of charge in each cylinder on each stroke of the engine. Different engine families require distinctly different spark advance profiles. And even engines of equal CID but different CR require their own unique spark advance profiles. Rule: Expect 0.1% to 0.5% loss in Torque for each 1 degree error in spark timing advanced or retarded from best timing. Also, detonation will occur with spark advanced only 3 degrees to 5 degrees over best timing and detonation will cause 1% to 10% torque loss, immediately, and engine damage if allowed to persist.
10-13-2006, 02:13 PM
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Thanks guys. I am really thinking that I have to much advance dialed in. I am going to play with it some more when I get home. It just doesn't seem to be as strong @ 36* total as it was with a little less. I also have not hooked up the vacuum can on my MSD distributor yet so that would probably add an additional 12*.
Anybody else??
Thanks
Wade
Anybody else??
Thanks
Wade
10-13-2006, 03:10 PM
#5
Safety Car
I run 18 initial and like I said 36-38 total.
George, the primary reason the fast burns heads need so much less timing is due to the efficiency and size of the combustion chamber. The same holds true for the race 10-18* heads. Even though they are on a 550++ in. motor they run total timing in the 20* range.
Black rat, if you really want to do it right put the car on a chassis dyno and check your plugs for signs of detonation. When the car is on the dyno you will often see little spikes all through the graph if it is detonating. You can do it without the chassis dyno, but like George said you will see power dip when you get to much timing in the motor.
George, the primary reason the fast burns heads need so much less timing is due to the efficiency and size of the combustion chamber. The same holds true for the race 10-18* heads. Even though they are on a 550++ in. motor they run total timing in the 20* range.
Black rat, if you really want to do it right put the car on a chassis dyno and check your plugs for signs of detonation. When the car is on the dyno you will often see little spikes all through the graph if it is detonating. You can do it without the chassis dyno, but like George said you will see power dip when you get to much timing in the motor.
10-13-2006, 04:24 PM
#6
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If you can't make it to the track to tune it..the chassis dyno is a great alternative.
As mentioned, every combo is different.
When my Brodix heads were unported, which have an "old school" style chamber, they picked up 17 hp moving from 36* to 39*. A couple of years later, the same heads and pistons, but with chambers opened up and polished, it was a lot less sensitive to timing. It made about the same at 37* as it did at 39*. Moving on out to 42* started to get noticable power drop on dyno..just about what GKull mentioned.
ML67 recently found that his 540 with AFR CNC heads liked 34* overall. Pushing it up to 36" only picked up 1 RWHP. Might as well leave it nice and safe at 34*.
You can always play with curve to keep initial timing up there and still have less total.
JIM
As mentioned, every combo is different.
When my Brodix heads were unported, which have an "old school" style chamber, they picked up 17 hp moving from 36* to 39*. A couple of years later, the same heads and pistons, but with chambers opened up and polished, it was a lot less sensitive to timing. It made about the same at 37* as it did at 39*. Moving on out to 42* started to get noticable power drop on dyno..just about what GKull mentioned.
ML67 recently found that his 540 with AFR CNC heads liked 34* overall. Pushing it up to 36" only picked up 1 RWHP. Might as well leave it nice and safe at 34*.
You can always play with curve to keep initial timing up there and still have less total.
JIM
Last edited by 427Hotrod; 10-13-2006 at 05:40 PM.
10-13-2006, 04:35 PM
#7
Team Owner
I just sent Edelbrock tech some e-mail about your heads and also about a friends VJ small block. I want to see what they have found. It just stands to reason that an efficient chamber and tight quench would have less residual dilution and faster flame travel. Requiring less advance. I do know that real race motors actually take timing out as rpm goes up. The cost of that technology is just kind of out of reach.
Off the post - but NOX RATT are you going to Vegas? NHRA
Oct 26-29 Las Vegas NHRA?
Is anybody else going? We are staying at the speedway in our motor home (no Vette) this year.
I'm going for all 4 days. I have friends competing in the sportman C/E and S/C classes. Our group has 4 day passes and we have seating in both A & D sections. Refreshment breaks are on the east side of the track.
Off the post - but NOX RATT are you going to Vegas? NHRA
Oct 26-29 Las Vegas NHRA?
Is anybody else going? We are staying at the speedway in our motor home (no Vette) this year.
I'm going for all 4 days. I have friends competing in the sportman C/E and S/C classes. Our group has 4 day passes and we have seating in both A & D sections. Refreshment breaks are on the east side of the track.
10-13-2006, 10:03 PM
#8
Racer
I run 12* initial and 20* centrifugal (all in by 3200 RPM) for 32* total with aluminum TFS Twisted Wedges on a 406ci SB.
I can't remember what I have in the Vacuum Can, but something like 10* - 12* I think (use as much as you can without detonation)?
It's really dependent on your unique combo though, with combustion chamber/quench, cam timing, and compression ratio being the biggest variables...
Doug
I can't remember what I have in the Vacuum Can, but something like 10* - 12* I think (use as much as you can without detonation)?
It's really dependent on your unique combo though, with combustion chamber/quench, cam timing, and compression ratio being the biggest variables...
Doug
Originally Posted by gkull
I don't know alot about modern BBC heads. But if they are anything like SBC with modern fastburn technology 32 degrees max advance is what you want.
In the past i had my mallory unilite recourved to 14 degrees of mech advance. Then i would set the initial at 18 or so. I've since changed to a full electronic MSD dist. and I change my max advance and courve with small switches. I now use 15 degrees max added advance all in at 3200 rpm
From Edelbrock tech articles.
CFM and Engine Control: Spark timing must be matched to Volumetric Efficiency because VE indicates the quantity of charge in each cylinder on each stroke of the engine. Different engine families require distinctly different spark advance profiles. And even engines of equal CID but different CR require their own unique spark advance profiles. Rule: Expect 0.1% to 0.5% loss in Torque for each 1 degree error in spark timing advanced or retarded from best timing. Also, detonation will occur with spark advanced only 3 degrees to 5 degrees over best timing and detonation will cause 1% to 10% torque loss, immediately, and engine damage if allowed to persist.
In the past i had my mallory unilite recourved to 14 degrees of mech advance. Then i would set the initial at 18 or so. I've since changed to a full electronic MSD dist. and I change my max advance and courve with small switches. I now use 15 degrees max added advance all in at 3200 rpm
From Edelbrock tech articles.
CFM and Engine Control: Spark timing must be matched to Volumetric Efficiency because VE indicates the quantity of charge in each cylinder on each stroke of the engine. Different engine families require distinctly different spark advance profiles. And even engines of equal CID but different CR require their own unique spark advance profiles. Rule: Expect 0.1% to 0.5% loss in Torque for each 1 degree error in spark timing advanced or retarded from best timing. Also, detonation will occur with spark advanced only 3 degrees to 5 degrees over best timing and detonation will cause 1% to 10% torque loss, immediately, and engine damage if allowed to persist.
10-13-2006, 10:33 PM
#9
Race Director
Three of my engines fit the description. Actually four fit but one is a A990 426 Hemi. The Chevies are two 427 L88`s and one 454 LS7. However all of these engines are a little higher in compression at a minimum of 12 1/4-1. The L88 engines are naturally GM aluminum heads and the LS7 that came with iron heads now have a set of Dart aluminum. All the engines vary at 36-38 total degrees all in at 3000. Plus all are run without any VC can connection. Idle at 850 rpms equiped with 850 Holleys on both auto and stick pieces. The LS7 car was kicked off the strip for lack of a roll cage and I never went back to see if any more lead would improve it as I have run as high a 40+ with a AA/A supercharged gas Chrysler. 
10-13-2006, 10:54 PM
#10
Senior Member since 1492
I'm running 18. Tried less than that and it ran like crap.
Now it idles 800-850.
Now it idles 800-850.
10-14-2006, 10:15 AM
#11
East bound and down...
My setup is very similar to yours. 496, alum rect port Edelbrock heads, CR is about 10.5 to 1, cam is flat tappet Comp XE284H, carb is 825 Mighty Demon w/ annular boosters.
My initial timing is 16* and total is 36* all in by 3200. I fooled with it quite a bit to find what the engine liked and it seemed the happiest with this setting. It idles well, is very resposive, pulls hard, does not detonate, and it will yield about 16-17 mpg on the highway.
My initial timing is 16* and total is 36* all in by 3200. I fooled with it quite a bit to find what the engine liked and it seemed the happiest with this setting. It idles well, is very resposive, pulls hard, does not detonate, and it will yield about 16-17 mpg on the highway.
10-14-2006, 08:23 PM
#12
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Thanks for all the advice guys. I didn't have a chance to fool with it today but plan on doing it tomorrow. I would love to put it on a chasis dyno but I have to find one in my area first.
Thanks again!
BR
Thanks again!
BR
10-18-2006, 10:49 AM
#13
Team Owner
From edelbrock tech support
My Big Block Chevy heads are your 110 cc #60459. I was told that they put out the most power at 32-34 max timing advance. Is this true? Are they "Fast Burn type heads"?
That 32 degree timing spec is accurate on a street driven engine. Fast burn simply refers to combustion chamber design; we optimized our combustion chamber design independently of GM
My Big Block Chevy heads are your 110 cc #60459. I was told that they put out the most power at 32-34 max timing advance. Is this true? Are they "Fast Burn type heads"?
That 32 degree timing spec is accurate on a street driven engine. Fast burn simply refers to combustion chamber design; we optimized our combustion chamber design independently of GM
