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Discussion Starter #1
430 SBF with Edelbrock SC1 heads and 11:1 compression. Pure race motor on Methanol. New Garrett 5020r-88mm twin turbo's should allow me to make over 40 lbs boost. SC1 heads have efficient chambers so I think they require less timnig than other heads. My base timing at zero boost is 28 degs. What sort of ballpark timing numbers should I be looking at with 40 or 50 lbs boost? Just trying to get an idea before I take the car to the track. I will of course be reading the plugs I simply have no experience at the 40 lb boost level. My previous turbos only made 25 lbs max on my combo. I'm also using Holley efi.
 

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Any chance the chambers have been softened?? If not do you know who ported them?? Search the forum on timing map and find my method. Someone will probably post the link to one of several times I have explained it.
 

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This is one of the first times I shared my method back in 2016.

I'll share how I go about defining the timing map. I begin by figuring out what is the highest average timing for the combo if run as a NA engine. In your case let's say 30* is max timing under power in NA form. Then based on fuel being used we can safely run 8-10psi boost before pulling any timing. This makes spool up and launch area pretty simple. Then use the simple formula to fill several XY points on the map, select the entire map area and then click on interpolate. Take max boost the engine will see, such as 35psi, deduct the 10psi boost that we will not pull timing and this gives us 25psi net boost. For every PSI above 10psi pull 0.5* of timing. Now the map points can be easily calculated such as the following:
35psi - 10psi= 25psi(net) × 0.5 = 12.5* timing pulled from 30*(base) - 12.5* = 17.5* @35psi

20psi - 10psi = 10psi(net) × 0.5*= 5*
30* - 5 = 25* @20psi

This simple formula can be used to spot check cells and make adjustments if they did not all get interpolated as you wanted. Again, I have never seen this approach hurt any parts but you must have a good understanding of what the base timing would be run as NA engine. You can always start a few degrees low on the base timing and work your way up as data is acquired. I hope I explained this in a way that can be understood, if not please feel free to ask questions.

I will add that the spool up areas of the spark map do not necessarily fall under this formula, it is only meant to be compared to a base NA timing under load. I have seen spool areas of the map as much as 10* above max timing under power. Every combo/converter is different and needs to be treated as such. As always start low and work your way up carefully.
 

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Discussion Starter #4
Any chance the chambers have been softened?? If not do you know who ported them?? Search the forum on timing map and find my method. Someone will probably post the link to one of several times I have explained i
Any chance the chambers have been softened?? If not do you know who ported them?? Search the forum on timing map and find my method. Someone will probably post the link to one of several times I have explained it.
TEA ported the heads and chambers are not softened. The problem I'm having with your recommended formula is when I look at the timing numbers at high boost they seem way to low.
Highest base timing NA is 28*
I start pulling timing at 8* ( 1/2* per lb boost)
50 psi minus 8 =42
42 times 1/2 =21
28 base -21 =7
7* timing at 50 psi seems awfully low to me. Maybe not but that's why I'm asking. Hopefully my math is correct.
 

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My method is not to establish maximum timing. It is to build a safe base map to begin the tuning process with that will not hurt the engine before you have a chance to optimize the tune-up. It is meant to be a safe starting point. Go slow and read the plugs.
 

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Discussion Starter #6
My method is not to establish maximum timing. It is to build a safe base map to begin the tuning process with that will not hurt the engine before you have a chance to optimize the tune-up. It is meant to be a safe starting point. Go slow and read the plugs.
Your advice on building a safe timing map is priceless and works well. I guess I was looking for other Yates head owners who had raced their cars and could get me a little closer to real world timing numbers to use at 40 lbs boost and up. Not many folks running that much boost. I did however get in touch with someone with a similar combo to mine who offered some track tested timing numbers at 40 lbs/boost to start with which should help me shorten the tuning time.
 

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Man there is no way to do what you want to do. Timing is not a number you can take from one engine and apply it to another. What Brian suggested is where I would start. I have seen plenty of times something simple as a hone and new rings require a totally different tune up than the engine did previously. Converter, gear, and tire will play a big role as the way the engine gets loaded and will require a different tune up. Please take Brians advice and go from there reading the plugs and watching carefully for it to slow down as your adding from your base. Best of luck and take it easy!
 

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Man there is no way to do what you want to do. Timing is not a number you can take from one engine and apply it to another. What Brian suggested is where I would start. I have seen plenty of times something simple as a hone and new rings require a totally different tune up than the engine did previously. Converter, gear, and tire will play a big role as the way the engine gets loaded and will require a different tune up. Please take Brians advice and go from there reading the plugs and watching carefully for it to slow down as your adding from your base. Best of luck and take it easy!
Brian's advice is sound. His method provides a safe somewhat conservative place to start with timing. I've been racing blown engines for decades and have a bunch of experience at 30 lbs boost and lower but not at 40lbs and higher. I actually know people with championship cars who run the same equipment as me (engine wise) who've been down this road and were able to provide me with their expierence on where to start with timing that shouldn't hurt my motor. I wasn't looking for the actual max timing number just a little help on shortening the tuning time and not wasting runs on low numbers that would show no heat in the plugs. Wasn't bashing Brian, I think his advice is great.
 

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The SC1 head is not the same as a Yates C3 which most run. If it's a Edelbrock SC1 they are super fast chambers un-softened due to extremely shallow valve angles. I would send them to Race Flow Development or BES and have them softened. I would also highly recommend running Fuel Hoops or o-ring/receiver at a minimum. I honestly would not trust anyone else's timing maps unless it is the identical combo down to piston design, cam and porting ptogram. If it's a steel rod engine I would be twice as careful.
 

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Discussion Starter #11
if I was tuning that motor I would treat it like a LS7 headed setup. fast burning etc, I would start at 15ish at 40psi and it would probably end up around 19-20 after getting the fuel dialled in and the plugs read..
Thanks for all the advice and concern everybody. I've raced my combo before on low boost (low 20's) with smaller turbo's. Timing map is tested good thru about 25 psi. Trying to run 4.0's in the 1/8th mile when racing starts back up. I figure it will probably take at least 40 psi. I've already been 4.3s at 21psi. Engine has aluminum rods, O-ringed heads, solid block etc. Gotta admit, the Eddy SC1 heads are bad ass.
 

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They have a much shallower valve angle and corresponding chamber than a 12* inline LS head. They are closest to a Edelbrock LSR head but are still more extreme on valve angle than the LSR. Just be careful and go in small increments looking at plugs/data very close. When the max timing is exceeded it will do so very quickly with very little warning. I would call Curtis Boggs at RFD and at least get his opinion on the chambers and tuning window. He has a ton of experience with those castings and some of the best port programs in the country for them.
 

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Thanks for all the advice and concern everybody. I've raced my combo before on low boost (low 20's) with smaller turbo's. Timing map is tested good thru about 25 psi. Trying to run 4.0's in the 1/8th mile when racing starts back up. I figure it will probably take at least 40 psi. I've already been 4.3s at 21psi. Engine has aluminum rods, O-ringed heads, solid block etc. Gotta admit, the Eddy SC1 heads are bad ass.
if your good to 25psi then you wont be pulling too much more out from there to 40psi... 6 deg out from there on all the SBF stuff i have done which use CHI 3v pro series which are a similar head, IE 19deg at 40
 

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No worries KevinL, I don't have thin skin even if you were. I came up with the idea of generating the timing base map looking at a number of cases where engines were badly damaged on the first couple dyno pulls or hits at the track. I took those values and did a little math. Everyone that I had good info on would have never been hurt using the process I have laid out. Obviously you have to use some fairly accurate info on the heads, fuel etc to derive the max NA timing but once you have that its really easy to generate good, consistent values as a starting point. It is also a good tool to spot check areas you see in the map that look high/low.
 
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