5.0L Ignition Timing

Pat

Supporter
Like many, I'm struggling with adjusting to ethanol content fuel. I've seen fuel filter gaskets turned to crumbly bits and suffering from vapor lock. I've solved the vapor lock by shutting the pumps down before I turn off the car and adding a phenolic block to the carb (Edlebrock four barrel). But I'm struggling with off idle throttle performance that simply isn't a crisp as it used to be.
I spoke to the fellow that built the engine and he suggested that I go one step richer on the jetting and advance the timing from 34o @3,000RPM to 36o. Midrange and up is just fine now that I've gone a little richer but low end isn't as clean. I haven't as yet changed the timing.
Has anyone else adjusted the timing to address this?
 
Pat,
On my Windsor 36 is the timing on my setup for max advance. Mine is FI but the timing, response is better there. What is your curve setup. Is it distributor or computer? If distributor what brand are you running and how is it setup. If MSD what spring setup are you running? If computer can you set the curve every 200 rpm or so??

Bill
 

Pat

Supporter
Thanks Bill,
I have a pretty standard setup with a stock Ford distributor with a Petronix Ignitor II in lieu of points. It's now set at 34o @ 3,000 RPM. At idle I’m running about 15o BTC. All I can really set is the distributor position.
 
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... But I'm struggling with off idle throttle performance that simply isn't a crisp as it used to be.

Hi, are you sure you don't have an issue with pump shot or transition fueling from idle to main circuit. Not familiar with Edelbrock/Carter carbs, but on a Holley (although it's often not easily adjustable) the transition circuit plays a major role in transition from off-idle to mains in a progressive/rolling throttle situation, and pump obviously plays a big role in a "snap-open" situation. Have you got a wide-band o2 meter so you can see if you have a lean flat/stumble? Going up in mains could be a band-aid.

Cheers, Andrew Robertson
 

Pat

Supporter
Thanks Andrew.

The Edelbrock is the same design as the Carter AFB. I've rebuilt the carb to include a new accelerator pump as well and verified the float and other settings after I discovered a partially dissolved fuel filter gasket. From 1/4 throttle on, it's great even under hard acceleration so I think the pump is OK. So now I'm down to timing and possibly a bad seat in one of the idle screws. (On screw's adjustment is almost a full turn less than the other's).
However, with the exception of ingesting some rubber bits from the filter seal, nothing on the carb has really changed. So I'm questioning if I need to further advance the timing to accommodate the higher ethanol content in the fuel.
 
Hi Veek,

How much ethanol by percent is now present in your local fuel? Has it increased recently?

If your problems presented after finding some dissolved rubber gasket material in your fuel system (fuel filter bowls), I would be more suspicious of something clogging a passage in your carb. Your statement that one of the jets adjusts much differently than the other also gives rise to the same suspicion.

If you have thoroughly checked all the carb passages during your rebuild, you can tell me I am nuts and tweek your timing. I don't think another 2 degrees of advance will cause you any serious long term harm since it is still in the "normal" range.

Mike
 

Pat

Supporter
Thanks Mike,
I belong to a local car club and the complaints I've had are very common among carbureted members of the group. The issues seem to have started in early summer with the arrival of the summer blend of fuel. The gas stations say it's "up to 10% ethanol" but many are wondering if we may have gone from some lower number to the full 10%. In discussion with the engine builder, he reports similar complaints. He also speculated that the demise of my filter gasket was ethanol related.
As far as the carb goes, I've rebuilt it and blown out the passaged with compressed air to they should be clean.
I'll add a couple of degrees of advance and see what happens.
 

Howard Jones

Supporter
Pat, give this a try. Keep the same 35-36 degrees total but get it all in by 2500-2600. I think you will find that the engine responce is just crisper. I have a 5.0 with 9.8 to 1 compression ratio, FMS "B" cam and home ported FMS "X" heads. It makes right at 300HP at the wheels.

I live in California so I have the shitty 91 octain 10% Al gas too.
 

Jack Houpe

GT40s Supporter
I agree with Howard, get the timing in as early as possible, my motor see's 35 anything past 1800 rpm.
 

Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
If you have a vacuum advance distributor, I have found much better off idle response if the vacuum advance was plugged into the manifold vacuum port rather that "ported" or "timed" ports on the carb.

Also...

Depending on your heads, static compression and dynamic compression, you may be doing more damage than good by going much beyond 32 degrees total timing. SBF's actually respond much better to timing than do SBCs for instance. Head design is one area that Ford had the advantage and it would seem that 32 degrees on a Ford is about the same as 40 degrees on a Chevy.
In dyno testing a number of 302 variants with both iron and aluminum heads in the 9 to 10:1 compression ratio range, Torque figures remained almost constant over 32 degrees until such point that detonation occurred. Detonation being the enemy, I would rather give up a couple of Pound-Feet of torque to give me a little better margin of safety..

Food for thought..
 

Pat

Supporter
Randy, I think at issue is the effect of ethanol fuels and the impact their burn rate has on timing. That's the basis of my engine builder's recommendation to go to 36o. I've not had any engine ping or other danger signs since I made the adjustment.

Here is a translated ignition advance table for a 5.0L HO extracted from a factory computer.
 

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Jack Houpe

GT40s Supporter
Randy, I think at issue is the effect of ethanol fuels and the impact their burn rate has on timing. That's the basis of my engine builder's recommendation to go to 36o. I've not had any engine ping or other danger signs since I made the adjustment.

Here is a translated ignition advance table for a 5.0L HO extracted from a factory computer.
Haltech has a ethanol percentage detector which will change values on the AFR table based on the amount of ethanol detected, not sure but it may do timing also. I know that ethanol has a higher octane rating so it would make sense to increase timing dependent on % of ethanol. With ethanol additive in most of our fuels we might as well take advantage of it. I wish there was a gauge that could measure percentage. I think the FLEX fuel cars use some system like this, again a gauge on the dash would be nice.
 
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