500" R/B Total Advance Timing

I recently went to an end of season test and tune. I had been running a total advance of 36 degrees and reduced it to 32 degrees and the car ran about 7 hundredths quicker? I then reduced it to 28 degrees and it picked up a couple more hundredths? It is a lot easier on the starter when it's warm and at 28 vs 36 also.
I would like to know what others are running for total advance on their 500" R/B engines?
Thanks! MJ

How much is initial?

Did you verify TDC on the dampener and timing tab?
The reason I ask that is when we tested timing at the track or on a engine or chassis dyno all the RB we tested like from 34 to 36 max, the race cars would slow down in the 1/4 with 38 or 32 degrees total
That was a long time ago with stock stroke iron headed bracket motors running in Super Street.
We ran street hemi cars in NHRA stock and had the same results on both of those cars
My last pump gas 518 C.I. BB with iron and aluminum heads seemed to like from 34 to 36 degree also

Depends on the heads and the piston shape and the fuel as well as other things but typically a BB Mopar with aftermarket heads and a flat top piston will like 34 degrees of timing. Maybe more, maybe less but any new build I work on we start with 34 and work from there. 28 seems a little low for max performance so you might have something else going on with that combination.

What it likes will depend on a lot of variables like CR, quench, combustion chamber and cam timing/events. (Edit: I see Andy beat me to this..)

Mine likes 36° total on 91 no ethanol. Starts INSTANTLY and shuts off easily. That goes away when I pull 6° out for the nitrous. It is harder to start and doesn't like to shut off without running on. Eventually I will put a timing adjust knob in it for the MSD but for now I am doing it manually.

Thanks for the replies!
Here is some added info:
Yes, The TDC of the piston and timing mark was verified.
The pistons are flat tops with Indy SR heads Max Wedge type intake ports.
Running 110 race fuel and compression is 12 to 1.
MJ

My Little 383/432 Stroker

Edelbrock E Street 75cc

10.5-1 True Compression

200 # Cranking Compression On All Eight

Comp Cams XE275HL

Loves 15 Initial - 18 Mechanical - 33 Degrees Total
91 Octane No Ethanol

Indy SR heads with flat top pistons and 12:1 CR should like 34 degrees. What do your plugs look like? You might have something else going on. Maybe the wrong air fuel ratio or weak spark.

This has come up before, and I kinda took a poll on racers running timing on B and RB engines.

I don't remember anybody running less than 34 degrees total, with most running 36-38. This is with verified time marks. I also informally did this at the track, talking to Mopar racers with the same results.

If yours is running great at 28 degrees, that just doesn't sound right, in a couple of different ways.

I've been running 38 degrees for years, on a street 440, and a race 500 ci.

Good luck.

John, I know the engine Bill's running with SR's didn't really make a difference between 32 and 36 either. Other than starting easier at 32. It did go slower at 38. We made back to back passes though no dyno like most of these guys.

Joe,
Thanks for the feedback on Bill's engine. I'm a bit disappointed it didn't pick up with the 32 degrees of advance. Like Bill I've been adjusting out there on the track and watching the results. I'm going to pull a couple of plugs and share the pictures here.
John

A lot of factors go into total timing. So much that you really can't go off of anyone else's setup. AF ratio, spark plug heat range, altitude you are running at, RPM range, piston type, cylinder head and combustion chamber efficiency, and on and on and on.

I have a 500 B on alky with 13.3 compression and domes that doesn't like any less than 38 degrees total. And the domes make it want more timing from my experiences and I have ran similar setups with flat tops that want lower total, maybe not like you are seeing but in the lower 30s anyway.. If she wants to run at 28, I would run her at 28!

Mine seems to like about 36 total. I dropped it to 32 and it slowed down. Ron

FWIW my 470" low deck picked up power on the dyno when we backed it down to 32* from 34*.
I haven't put it in the car .


Mark

My 500" wedge always liked 34*. I ran several different cams in the 245* to 255* range.

Here are the # 1 ( right ) and # 2 ( left ) plugs right after the last run at 28 degrees total advance. I had gone back up to 32 degrees and slowed a bit and then back to 28 degrees and picked back up.
Thanks for the replies!
MJ

Can’t see the timing marks on the ground electrodes with those fuzzy pictures

But it’s running rich

It's rich and the plug looks hot. That's why it likes less timing. He is pulling timing to keep the plug from overheating, rather than let the plug function like it was designed.


I've seen that my entire life.

Mine runs 15-1, flat top, 4.5 bore, -1 head. 114 renegade fuel. 32 degrees. Any more timing does nothing for ET or MPH. It's run as little as 28 degrees. Barely killed .10 in ET.
Doug

A most efficient highly developed all race N/A motor on good quality high octane race gas will like less timing than a conventional bracket or Stock super Stock like motor will, I'm talking about Pro Stock and Comp Eliminator motors that like a BSFC in or lower than .32 Lbs. per hour
On your deal with those spark plugs it looks like pitting and blistering on the porclyn and way to hot on the heat range as well as rich on the AFR

I also forgot to say that my car is 10.6 comp and I run 92 pump. Ron

What’s the timing light being used?

FWIW, I’ve never dynoed anything where the best power was made at 28* timing.

High VE means higher cylinder pressure: less spark

Come on now, you know you meant less lead, not less energy on the spark plug tip? correct

Here are some pictures of my timing light. It is still set at 28 degrees from the last run.
MJ

Here are some more pictures of the #1 and #2 spark plugs. The first 2 are #1 and the last 2 are #2. The one turned out real well and should help analyze.
MJ

What plug n heat range...........looks rich, wet and unhappy........

Your plugs look horrible. Either those plugs have 100,000 miles on them or else you have something really wrong with your tune. Here is a plug out of my 514 engine after making 900 hp on the dyno. This engine is 15:1 compression.

Dial-back timing lights...... I don’t trust them.

The first thing I’d do is get a light without the dial-back feature and redo the test at the track.

That is another possibility. Your timing light could be lying to you and you are actually running 40 degrees of advance. That is why your plugs look like that and would explain why the engine is happier when you retard it a few degrees.

Those plugs look quite unhappy....First how many passes are on them? What plug is it?

I thought I was the only one that felt this way. Only used two dial-backs, and they were both incorrect. I'm still using my 45 year old Sears non dialback timing light.

Have you ever dialed zero on that light and checked the timing? I'm like the other guys, have doubts about the accuracy of the timing light. Only reasonable explanation or best power at 28 degrees.

Those plugs in the pics have short straps, mine are NGK BCP7ES have straps that are over the electrode. Any benefit from a short strap ?

The short strap plugs are a little more fool proof. I like to use them on high compression engines. I don't think there is a power difference, they are just a little more robust since it is harder to bend the strap if someone on your pit crew drops the plug on the ground when you aren't looking.

The exposed gap into the combustion chamber is usually a small benefit for race motors, especially if your close to the piston tops with the plugs
Try them and see if you like them

The plugs have no more than 20 passes on them.
I have attached a picture of a new box of plugs.
They are Champion product number 297 plug number C61CX.
The heat range is the 61 in the part number.
I hope this helps?
MJ

Lawn mower plugs...........

Nothing wrong with that plug. I use champions and that's all I use unless the customer has some weird aversion to them.

That 61 is a fairly cold plug, yet those look hot. Unless you are at sea level and 15:1 that plug should be the correct range. You can try the 59 but I'm not sure what's going on.


You got a ton of fuel moving through the engine, no timing and plug that looks hot. Something is weird.

I just skimmed back through the thread and you are at 12:1 so that plug SHOULD be too cold. I would have started with a 284/C65YC or if you don't want the extended tip you can use the 285/C65C and tune from there.

So I've switched horses mid stream. I'm going to say get a hotter plug, verify TDC and your timing light and tune from there.

As AndyF said your plugs look bad. Sometimes looking at pictures isn't the same as looking in real life.

If there is no reason you can't run an extended tip plug, I'd use the extended tip.

The C61CX is at the top of the heat range! They make a C63CX and it is at the top. They also make cooler C59CX, C57CX, C55CX and C53CX. I have attached a chart showing these numbers hot to cold. So my C61CX is one of the hottest heat cycle plugs. So now my question is how far to go down in heat range?
Thanks! MJ

are these aluminum specks on the plug??

I like NGK’s.

At 12:1 you’re in the -7 or -8 heat range(higher is colder).

I run NGK #8's at 12.1.1 comp and they last a long time on the street testing carbs and general cruising BUT my motor is in a pretty optimum tune verified by track times, afr's, plug readings and a good street tune before I hit the track. Plug looks glazed over which is as stated HOT combustion chambers weather too much timing, lean, too hot of plug etc...........Good luck...........

Rule number one is NEVER use a cross reference for plug heat ranges. They are somewhat close approximations, but not good enough to use as a fool proof heat range indicator.

Again, like I said, I don't think you need the cut back ground wire plug. At your compression ratio, you just don't need it.

IMO, you'll be better off with an extended tip plug.

The C65YC and the C65C are both two ranges hotter than what you are running.

I'd have to look but I'd bet the plug that Porter just posted isn't a cutback ground wire plug.

So as I said, I'd order the hotter plugs and start over after you verify TDC and your timing light.

Don't be married to the CX plug. It may look cool but you just don't need it.

BTW, did you mention what ignition you have? That sort of greenish tint can be from a weak ignition.

If you call NGK they will recommend the correct heat range. At 15-1 I run -9. I would bet at 12-1 the suggestion of -7/-8 is very close
Doug

The ignition is MSD all the way!
MSD distributor, MSD coil and MSD coil wires. New cap and rotor also.
MJ

Which MSD box?


Like AndyF said many posts ago...your plugs look strange. At first look I thought they were too hot and reducing timing and adding fuel were keeping it from killing itself.


Once we got deeper into it, it seems to me those plugs are plenty cold for what you are doing. That doesn't explain the green tint, what looks like a ton of heat and not being able to see a timing line on the ground wire.


The insulator should be a dull white from the top down to the fuel ring. Most likely, you'll see some clouding on the porcelain from coming up the return road, especially if you don't run a power valve.


The plugs look strange and your timing is also an anomaly.

Is the ICU a 6,6A,6AL, 7AL2 or which MSD box are you firing the coil with and which coil are you using?

As stated in so many ways, your timing is not at 28 degrees. Get the timing right and put some of those recommended above new plugs in, and go again.

From all the replies and ideas I am going to verify the timing first.
Then before I make my first pass I will install one of the recommended plugs and see how it goes. If it looks rich at that point I'll adjust the carb.
Thanks! MJ
P.S. The MSD box is a 6AL with a MSD BLASTER 3 coil.