Timing for aluminum heads (TA)

Discussion in 'Small Block Tech' started by Jim Blackwood, Jan 23, 2020.

  1. Jim Blackwood

    Jim Blackwood Well-Known Member

    Considering the advances used in TA's heads I'd be interested in seeing what ignition timing curves or maps are being used. Here's a reference discussing the matter in some depth:

    And here's a screen shot of a stock LS6 timing table. I would think it would be somewhat close to what would be used for the TA heads.


    You'll notice in the table that one axis is in Grams/cyl. Very roughly speaking, idle correlates to the .o8 end, WOT to the roughly .7 region and boost to anything over about .9 or so. So what do you guys think?

  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I have found that the TA heads in my engine likes more advance. I have run as much as 38* and seen an increase in trap speed. On the street, I run 34*.
  3. Jim Blackwood

    Jim Blackwood Well-Known Member

    Thanks Larry. What are you running at idle and WOT?

  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I run my advanced locked out, Vacuum advance of 10*. MSD has crank retard of 20*. On the street, 34*.
  5. Stevem

    Stevem Well-Known Member

    There's nothing carved in stone with timing even if we talking about comparisons in the same basic Motor!

    Big factors are mostly related to cylinder pressure rise determined by Intake valve closing point, the motors stroke and its static compression and chamber shape.
    Comparing a LS headed motor that needs only some 32 degrees of lead time to the TA heads as in post number 2 can lead you far astray!
    Also the amount of Intake swirl and or tumble that a Intake port produces just before TDC can have a 3 degree effect on the timing needed.
    Mark Demko likes this.
  6. Mark Demko

    Mark Demko Well-Known Member

    Every 350 Buick engine that ends up with TA aluminum heads is going to differ as far as piston design, comp ratio, cam profile, intake, carb, A/F ratio, fuel used.
    Then there's the factor of convertor, gearing, and vehicle weight.
    Automatic, or manual trans.
    This will be the fun part, tuning, testing, discovering what the 350 wants and can tolerate.
    Heck, the SP3 I/we haven't really tested. Only thing I've discovered is I can run it to 7 grand and the engine likes it, and it obviously is making power up there as I FINALLY broke 100 mph, and got my lowest ET so far.
    68Rivi_In_Cali, cjeboyle and MrSony like this.
  7. Jim Blackwood

    Jim Blackwood Well-Known Member

    I know what you guys are saying is true. However some things remain constant as a usable "rule of thumb" that you can use to set up the timing initially. For instance, somewhere between 0 and 8 is usually going to work for cranking. Somewhere between 8 and 22 is usually going to work for idle. Somewhere between 20 and 28 is usually going to work for WOT-N/A, and somewhere between 28 and 38 is usually going to work for cruise, is this not so?

    However, the new TA heads are a bit more modern. The Rover heads have the heart shaped combustion chamber for instance, do the 350 heads also? I hadn't looked but they came after the Rover heads so it seems likely. That is now considered the optimal design for swirl I think and with other changes I suspect the new TA heads may be every bit as modern as an LS head. And there are variations in the LS heads too, where an LS6 head takes less advance that the earlier heads. I mean, it's not like we're talking about Hemis here, these are at least a little more forgiving than that.

  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    The optimal amount of advance will produce the most HP. Below that, less power, beyond that, less power. Today's cars have microprocessor controlled smart ignition systems. The PCM advances the timing until it hears knock, then pulls timing out. Without a PCM to make adjustments 60 times a second, I am afraid we are left with trial and error.
  9. Stevem

    Stevem Well-Known Member

    Pro stock engine builders fight like mad to keep there needed timing for peak power within 1.5 degrees so your stated timing range of 28 to 38 degrees is like the distance between the earth and the Moon to them!
  10. Mark Demko

    Mark Demko Well-Known Member

    Yep, were comparing stone age tech, with space age tech:eek:
  11. Jim Blackwood

    Jim Blackwood Well-Known Member

    Well sure, but you have to start somewhere. Even the most expensive engine builder on the planet has to plug in some initial values and sneak up on it. Yes, they do have theories, formulas, and computer modeling to help out but in the end it's all about the dyno testing. Unfortunately, most of us do not have a dyno in the backyard. Or usually a dragstrip either. Maybe not even a G-tech, though that's not such an expensive option. And it isn't all about WOT either. Think it's easy to get optimum timing in part throttle cruise mode? Well your dyno guy will tell you to advance it until it stops making power but your knock sensor method will have you advancing it until just before it begins to knock. Guess what? You might have 10 degrees between the two, maybe even more, and every degree past the power peak, no matter how flat, causes strain on the engine and uses more fuel. so the knock sensor method is seriously flawed in any engine except one with the peakiest power curve in cruise. Which a SBB is decidedly not. Probably not even with the TA heads. So you are flying blind with that method.

    Then what about idle? It'll run at idle with anywhere from 3 to 30 degrees and if you set it where it is happiest you might have some fun with the fueling and throttle plate opening (IAC) getting it back down below 800rpm, then there are off idle performance, heat production, and even emission concerns.

    What if you are running boost? Certainly don't want to guess too much about that. Retard a degree per psi? 1-1/2? Some rule of thumb here would certainly help at startup, though of course it is highly dependent on what you are doing about WOT.

    How about the deceleration zone? Acceleration at part throttle? Idle dip? Cranking? All very important parts of the map, though the more modern ECUs have a separate table for cranking speed.

    I realize you guys who are still running distributors don't worry about most of this. If you change your distributor's curve at all that's sort of a big deal. Usually you just set the static advance and forget the rest. But as the ECU crowd has found, there are improvements to be found in the advance map far beyond the dragstrip ET, but getting from here to there can be difficult.

    So yes, the numbers can be all over the map. Anywhere from -10 to +40 if you look at the factory LS setups. And this is with a head and intake design that is supposed to reduce the timing range? Well clearly there is something else going on here and you find out what it is when you begin to look at the part throttle acceleration curve and the unused parts of the map. In actual fact the part of the map really being used does have a reduced range.

    So the original point is that all this should lead us to expect the TA heads to have a range that is reduced from that of the old iron heads or the aluminum 300 heads. Of course, other than the BBB and Rover heads TA has been the only ones able to test this so far. And I haven't seen Mike jumping in with any suggestions.

  12. Mark Demko

    Mark Demko Well-Known Member

    Its all going to be trial and error:D
  13. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Not sure what I can contribute to this thread. Like I said, I have found my TA heads like more advance to make maximum power at WOT. I have no way to measure what is happening at part throttle but running my advance locked out makes the engine idle better with more vacuum. At cruise, my vacuum advance adds 10* so I am in the mid 40's at light load. It doesn't ping or surge, and gets great gas mileage. My AFR meter says it idles in the mid 13's, cruises at high 14's to low 15's, and WOT says 13.0.

    I understand you are looking to come up with a fuel injection map. Not sure how you are going to do that with trial and error with no real way to evaluate your results except the butt dyno. We all know the butt dyno doesn't have enough resolution to be of any use. By the time you can feel it, it's a pretty big difference. Then there is the differences inherent in multiple combinations of parts, no ones engines are exactly the same in our hobby. The LS engines for all intents and purposes are. GM had the resources to optimize everything. Might be a good starting point for you, but I doubt it will be anywhere near optimal. I think you might get more feedback from guys who have been messing around with FI for some time. TheSilverbuick comes to mind,

  14. Jim Blackwood

    Jim Blackwood Well-Known Member

    Well, I've been creating fuel and timing maps for Buick engines for about 2 decades now and have at least an idea of what they should look like so that helps. It's not something that worries me. But I was working up a new timing map for the GM '411 ECU now wired to my 340 (with 300 alloy heads and an Eaton blower) and thinking about the set of TA Rover heads sitting on the bench and thinking SURELY there can't be that much difference between those heads and early LS heads. But you know what? Those stock advance maps for the Camaro are about the roughest thing I've seen. It's hard to imagine how GM ever let that get out into the wild.

    And I'm not suggesting that by guess and by gosh should be the watchword. What I am suggesting is that there is a lot of historical information that can be taken into account to get things a lot closer than one might think. Yes all engines are different, but usually they are close and there are many duplications, so the scope can be narrowed. For instance, most engines of the same family do like a similar sort of advance curve. Most of those with similar compression like a similar total advance, static advance, and cranking advance. That gives you most of the map right there, within a few degrees. Then fine tuning can take advantage of many options. In my case, vacuum, coolant temp, EGT, O2, datalogging, and G-tech all come into play. And probably the most important key of all is to continue to think of it as play. As long as it is fun it will get done. So it's important to try and eliminate all potential sources of frustration and make the tuning easy. In our not so perfect world sometimes a reminder of that is a good idea.

    I do also feel that in terms of timing it is important to sneak up on it, and I've had the eroded pistons to know whereof I speak. But at the same time it's almost as important to not start out too low. Nobody needs cherry red headers. So finding that good middle ground before the first startup is a fairly important key to keeping up the fun factor.

  15. Mark Demko

    Mark Demko Well-Known Member

    Me thinks IF the Buick 350 was still in production and had all the latest and greatest engine management we do today, AND then TA's heads come along, we bolt 'em on, THEN we could probably do some comparisons between the LS timing map and the thoroughly modern 350 Buick V8 WITH TA's new aluminum heads.
    But were it stands now, the technology is decades apart.
  16. Jim Blackwood

    Jim Blackwood Well-Known Member

    Yeah, but you can retrofit all that stuff.

  17. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    I'm adding a EGT probe to each header primary. That combined with an air fuel meter and reading plugs should help.
  18. Mark Demko

    Mark Demko Well-Known Member

    It would actually be fun to strip an LS engine of all its electronic management and retrofit it to a 350 Buick, and I mean EVERYTHING!
    No aftermarket EFI, no aftermarket distributorless ignition, just ALL OEM controls.
    Lotta work fabricating for sure, and lotta money and time, but the results would be interesting:cool:
  19. GraySky

    GraySky Well-Known Member

    It's an interesting question. The LS motors seem to be very quick burn and don't need a lot of timing; particularly with boost.
    Maybe we should back up and discuss what aspects of the design are responsible for that. Efficient chambers? Plug placement? Velocity and cylinder charge?
    How does that compare with the 350 head?
    Unfortunately, there are some major differences, like port and valve arrangement, so maybe it's not a good comparison.
  20. Jim Blackwood

    Jim Blackwood Well-Known Member

    That is sort of what I was getting at. The chamber shape is a big part of that and on the TA heads it is much different from any of the stock Buick chambers. On the Rover heads the chambers are even smaller. So small in fact that a large piston dish is required in order to get the compression down to streetable levels and still have any squish. Either that or enlarge the chamber, which is something that I'm considering. I wouldn't mind being able to run flat top pistons, and with a 5/8" thick deck on the heads to work with that might be a possibility.


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