I was taught when tuning ignition timing to set as much base timing as possible, until it pings then back off 2˚ and set total timing to be no more than 36-38˚. The mechanical advance should be all in by 2500 rpm; then using and an adjustable vacuum advance canister, increase vacuum advance until it pings at part throttle then back off a couple of turns. I'm struggling with tuning my SBO stroker as things aren't working as expected. In the past, I've only tuned stock-ish motors, never tuned a performance oriented motor. I'm currently at 22˚ initial timing, total mech advance is +21˚ all in by 2500 rpm. I know, this is way too much total timing; I was planning to use a limiter bushing on the advance weights once I found where it started to ping, but it doesn't ping. WOT throttle response is sluggish but eventually gets going, breaks the tires loose on the 1-2 shift (which is very satisfying) but can't roast the tires from a dead stop. Here's my engine combo following a Mark Remmel stroker recipe:

Stroked crank to 3.5" yielding 375cid
10.1:1 compression
ProComp BMRE aluminum heads cut down to about 69cc chamber size
Custom Lunati hydraulic roller cam, spec'd my Mark: duration 223/229 @.050, lift .557/.541
Idle is rough but smoothes out with a little throttle (could just be the cam)
Has 12-15 inches of vacuum at idle
FiTech GoEFI 600HP #30002 throttle body EFI (dialed in the IAC steps and zero'd the TPS not much else)
Transmission is a built 200-4r with D5 convertor, 2500 rpm stall
Rear gear is 3.42 with Eaton Truetrac posi
Rear tires are 285-40-18

Current timing: 22˚ initial + 21˚ mech advance all in by 2500 rpm; +15˚ vacuum advance
I pulled a plug to "read" the jetting; plug looks very rich even though the EFI is reporting 13.6:1 at idle.

Is the AFR overly rich? Could that prevent the motor from pinging?
Do I need hotter plugs?
What should be my next step??

Rodney


Accel #784 plugs

 

What converter and rear gear? What AFR is FI Tech running, part and WOT? That plug looks rich and maybe wet with oil. I wonder if it is like Holley, richer than what the AFR reads.

 

That plug looks oil fouled, perhaps subject to misfire as a result. I would investigate and correct the plug fouling before continuing with tuning.

 

I edited my initial post; TH200-4r transmission, 3.42 rear gear, 285-40-18 rear tires. The FiTech target AFR at idle is set to 14.1, the dashboard reads 13.6; WOT target is 12.6, the dashboard reads 10-11 when I make full throttle passes.

 

Could the oil fouling be left over from initial engine break-in? Can I pull the plugs to clean them up at start again?

 

The 13.6 isn't so far off but the 10 and 11 is way too rich. I wonder why it is so far off? My Holley Terminator X Max goes the other way, spikes lean often. You should be laying rubber really hard off the line as is. I would clean the plugs and adjust the WOT AFR up about 1 to 1 leaner, like 13.5 to 1 and see what it does.

 

I pulled all the spark plugs tonight after dinner with the wife and took a few pics to help with the diagnosis. In the group shot, plug#3 looks more wet than the others; but it smells like gasoline not engine oil. This is the same plug I showed in post#1. My catch can captured about 2.5ml (2cc) of oil in 50 miles of hard driving. The PCV is downstream of the catch can and shows no sign of oil so I don't think the engine is pulling oil into the throttle body from the PCV system. The close-up pics are plug#1 and plug#2. Does the black soot around the threaded part of the plug indicate a rich condition? The insulators are kind of brown, not white, does that look like detonation?

Rodney


Spark plugs arranged by bank location


This is plug #1


This is plug #2

 

There is no real reason for only one plug to be black, unless it is oil. They would all be black, if it was fuel. Being a new motor, the rings may not have seated. How does it run with less timing? Dropping the base 5 degrees would still be 17 at idle and 36 WOT.

 

How many miles on the engine ?

 

Less than 200 miles on the motor. I cleaned and re-gapped the spark plugs before reinstalling them last night. I have an adjustable Wagner PCV that has 2 circuits which are dialed in to the engine vacuum at idle and cruise. The manifold vacuum is affected by the timing, it drops to 10-12 inches when I pull the base timing back to 15˚; with the timing set at 20˚ the vacuum increases to 15 inches, with vac advance disconnected. So this morning I pulled and capped the hose to the PCV to eliminate one variable during tuning. The throttle response improved with more vacuum advance, but still no audible pinging or tire shredding. I tried increasing the AFR settings but hit FiTech max setting values. Idle=14.7, 1100=14.7 (maxed), 3000=15, 6000=13; WO1100 13.5 (maxed), WOT3000=13.5, WOT6000=12.6.
It seems like the FiTech is swap it out? I have the FiTech O2 sensor in the passenger side header collector, I could get wideband AFR meter and install it in the driver side collector to compare AFR values. I think the AEM kits start around $200 so kind of expensive way to check. Should I be looking for an exhaust leak? Seems like that would cause the over-rich condition Im seeing.
Looking forward to the comments, thanks!

Rodney

 

I found quite a variance between the Holley Terminator and the AEM sensor. About 1.5 richer showing on the AEM, I believe. But Mark mentioned the Holley is richer than it shows. I would spend money on a Progression distributor before a second wideband. I still say it should spin both tires hard. What is the converter actually flashing too? About the lowest I seen any factory 2004R converter stall is 1900. Probably tune related, also where is the trans shifting?

 

I was gonna say a 375 cid engine with 3.42 rear gears and a low 1st gear TH2004R should shred the tires. Then I saw they are 285s, which have 11.2” tread width and likely a sticky rubber compound.

But still, it’s a 375 cid engine.

 

You're right, the 285 tires are Continental, Extreme Contact DW and have a sticky AA traction rating. The engine wasn't dyno'd but I was expecting 370-400 HP from this engine combo; wouldn't this be enough to overcome the wide, sticky tires? The 200-4r has a first gear ratio of 2.74 and the 3.42 rear gear gives an effective ratio of 9.37:1. I always heard than 10:1 was the magic ratio for strong launches. The transmission builder had the D5 converter rebuilt to stall at 2500. I felt that stall speed might be too loose for a street driven car that should cruise around 2000 rpm in OD at 70mph.

Rodney

 

I think a good quality 2500 RPM converter is optimal.

My car has a Hughes 2500 RPM converter and it has worked very well with the 3.23 rear gears and also, surprisingly, with the 2.56 gears while I was rebuilding the other rearend. It has about 250-300 RPM slippage which is the same as the factory converter, even with the 2.56 gears and cruising at 1800 RPM.

 

Kenneth:
I've owned five 71-72 Cutlasses in my lifetime, all were mostly stock-ish builds, 350-4B, TH350 with highway gears (2.56, 2.73 and the last car had a 3.08 gear). The 2500 stall convertor feels very different from these previous cars (I guess you could say it's looser) but with the 3.42 rear gear it accelerates much more quickly. I'm gonna let the AFR issue rest for now; I'm dropping the car off to the upholstery show tomorrow to install a new convertible top. After I get it back from the shop I need to figure out how to do a data log from the FiTech to see what's going on with the tune.
Big thank you to everyone who chimed in this thread.

Rodney

 

Yeah, those Extreme Contact are grippy and expensive tires, have them on my Challenger. But you should be knocking on 500 ft/lbs with the extra stroke. Even if that is past your converter stall it should be pushing good torque at stall. Being at 10 to 1 compression, that isn't a big cam with the extra cubes. It sounds like a tune issue. If it was a timing issue, retarding or advancing should make a difference on launch. Is it still going very rich with the WOT leaner?

 

I dropped off the car to the upholstery shop this morning to get the convertible top installed, so I'll resume tuning after I get it back. My current timing is 18˚ base + 21˚ mech at 2500 and about 20˚ of vac advance. One thing popped into my head this morning as I drove the car to the upholsterer; I was hearing kind of a light rattle at part throttle but couldn't be sure what i was hearing or it's origin. This is my first car with aluminum heads; I know what pinging sounds like with iron heads but does it sound different with the aluminum heads?

Rodney

 

20* vacuum advance is too much, it needs to be limited to 10.