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| Ignition timing question | Login/Join |
| DRR S/Pro |
How much would be too much, Dart 325 pro 1 head, 4.250 stroke, 4.280 bore. Huge intrusive dome, about 13.5:1, maybe 14:1. Sonoco 116 fuel. I was at 37° and it was terrible wouldn't get on the converter. Went to 40° and it got way better. Plugs look good still. Still a little lazy getting on the converter. Added another 2 degrees just now, total of 42° and it's very good at getting on the converter. Is 42 too much?? I'm use to spread port motors with very little timing and small combustion chambers .991 60' 4.36 @ 159 so far..... 6.86 @ 198 trying for more...... 533" single carb 235" Harrison 4-link | ||
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DRR S/Pro |
Just out of curiosity did you confirm TDC? Seems like you are compensating for something | |||
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| DRR S/Pro |
I did actually, I thought the same thing. So I took an exhaust valve spring off and used the valve with a dial indicator and the balancer timing marks to do a verification that TDC was in fact TDC. .991 60' 4.36 @ 159 so far..... 6.86 @ 198 trying for more...... 533" single carb 235" Harrison 4-link | |||
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| DRR Top Comp |
IMHO an ideal set-up would be to leave with 42*-44* and ramp the timing down so you're at 38* right after the high gear shift. Those small bore/cubic inch BBC engines have that awful dome that the flame has a hard time getting over at anything under 40*. But it will really like going threw the lights at 38*. I guess at 7000-8000 rpm all hell is breaking loose in there and the flame probably never stops. But, since it seems to really like the timing at 38* I would definitely make some runs like that before you start monkeying around with timing retards and stuff....Keep it simple anytime you can.. . Dave F J B | |||
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| DRR S/Pro |
I had actually given that thought as well and I already have the wired to have a timing retard, it would be as simple as changing chips and turning a timer on. I run my 12 degree motor with a 2° retard down track now, so that's not out of the question .991 60' 4.36 @ 159 so far..... 6.86 @ 198 trying for more...... 533" single carb 235" Harrison 4-link | |||
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| DRR Sportsman |
What’s the jetting and plug range? | |||
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| DRR S/Pro |
94 in the front 96 in the rear. And AR3933 plug .991 60' 4.36 @ 159 so far..... 6.86 @ 198 trying for more...... 533" single carb 235" Harrison 4-link | |||
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DRR Top Comp |
It is relatively cheap and easy to dyno a motor and you can find out exactly what timing it likes and get fuel right. You will also learn exactly where peak torque is and that will help you get perfect converter. The key is going to a good dyno operator who knows what to look for. https://postimg.cc/gallery/np3zpruo/ "Dunning-Kruger Effect" -a type of Cognitive bias where people with little expertise or ability assume they have superior expertise or ability. This overestimation occurs as a result of the fact that they do not have enough knowledge to know they don't have enough knowledge. Before you argue with someone ask yourself, "Is this person mentally mature enough to grasp the concept of a different perspective?" If not there is no point to argue. 4X NE2 CHAMPION. 2020 TDRA NE2 Champion | |||
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DRR Pro |
Let the time slip and spark plug timing marks be your guide. "Despite the high cost of living, it remains popular." Dave Cook N375 | |||
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| DRR Trophy |
Also works on mine. Over the winter I went to a megasquirt system, but only running the spark. Distributorless using Volkswagen 4 tower coils (2 ea). 40 degrees at the launch, above 6500 it pulls timing. bigger inch SBF loves it. Idles a LOT better too, cleaner on the limiter, cleaner at the line. Have a second timing map for when the primer is on, stays at 30 deg from 400 rpm+. Cranks at 10. When I ran distributor, I did some R&D and found the timing was moving around 2-6 degrees depending on RPM, load, etc. and we all know that spark timing is critical. We found a bit of consistency with this setup. | |||
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DRR S/Pro |
No reason it should need more than 35-36 degrees Conventional head, typical dome I've run that exact combination on gas and alcohol injected and never ran more than 36 degrees Jetting sounds a little high but may be fine.... I did not understand how you verified TDC by removing a spring ? With the head on use a piston stop thru the plug hole is the typical way of doing it It's a stretch to think the TDC mark is off a lot....unless there is a bad mismatch of balancer and timing tab.... When I build an engine and don't have the front assembled enough to verify TDC.....I mark the rear crank flange at the back of the block and it is an easy way to see TDC even with head on... | |||
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| DRR Sportsman |
Rich, You would bring the piston close to tdc pull the spring and install and indicator on the valve stem top. Rotate to highest reading and there’s tdc. | |||
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| DRR Sportsman |
Not accurate. Remember the piston dwells at TDC as the rod rotates around to change direction. | |||
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| DRR S/Pro |
Good Morning Will: I'm an old school plug reader (I'm old and I went to school) so I go by what the spark plugs are showing , correct heat range, correct jetting, and correct timing. Sunoco Maximal (116) may not give you the best results, I've basically use the same bore/stroke, Dart 325 combination and Sunoco Supreme (112) gave me better results, when I tried VP C16 and Sunoco Maximal it didn't produce the same results regardless of how much timing I used, including upwards of 42 + degrees. That longer rod (.400) slows the piston as it approaches TDC plus the dwell time at TDC is longer. I'm not a big fan of high dome pistons/large combustion chambers (120cc +) with long rods. Personally I would try Sunoco Supreme (112) and read the plugs to see what the combination will tolerate while producing better power. EGT's and 02 sensors are great but to me the plug tells me more. Move a EGT probe 3/8th of an inch and the reading changes, that spark plug is IN the cylinder it does not move, it creates the flame and the corresponding flame propagation, it sees everything. Just my .02 Bob | |||
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| DRR S/Pro |
I never thought of using that method.....it's a good way...not perfect but if done right would be very close... | |||
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| DRR Top Comp |
I agree with most of this. Read the plugs. A few things to note here, if you are fat you can get away with more timing than needed. Still 42* is a lot of timing here. If you have verified your TDC then try another timing light and see if it is the same. I would try opening up idle mixture screws some and see if that helps you get on the converter. Could possibly use some tuning on your booster pumps and nozzles. Or try a different carb. Another possibility is you could have a problem with the converter? Hard to say but it may not all be timing as the basic problem. The timing mark on the plug is a window in the chamber but it is really only telling you highest reading. I think O2 are great but those numbers are useless until you get a good baseline, good ET and good plug readings. Then you use the O2 to keep that tune up and improve on it. I have ran EGT and they were not reliable and repeatable in my stuff so I no longer run them. Firm believer in O2's if you know how to use them. Just like EGT, O2 and even timing they are just a number for reference. The only number that really matters is ET and MPH. https://postimg.cc/gallery/np3zpruo/ "Dunning-Kruger Effect" -a type of Cognitive bias where people with little expertise or ability assume they have superior expertise or ability. This overestimation occurs as a result of the fact that they do not have enough knowledge to know they don't have enough knowledge. Before you argue with someone ask yourself, "Is this person mentally mature enough to grasp the concept of a different perspective?" If not there is no point to argue. 4X NE2 CHAMPION. 2020 TDRA NE2 Champion | |||
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| DRR S/Pro |
There are methods/tools you can use to manipulate the timing, induction and exhaust systems to better serve your combination. They can get a little expensive and they will require constant testing. Back in the mid to late 70's I used the smaller bore longer stroke but with a 6.135 rod combination. My son Mike and I made several alterations to the cylinder heads opening up those 325's to 357. At the same time we also made a cam change from a really good Schneider flat tappet to a slightly larger Crane roller. The power improved over the entire power band plus I was able to use less lead. In that case we used the same Munsinger 8 inch converter with a 4.88 (Super Gas) gear. Bob | |||
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| DRR S/Pro |
Now that's a name I haven't heard in years, ran his converters back when I ran S/G in the 90s | |||
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| DRR Sportsman |
You can rotate cw set you 0 then ccw and pick the space in between for tdc | |||
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| DRR Sportsman |
That does make sense. | |||
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