Posed this question on the FE forum but not much traffic there. Since many knowledgeable people here, will post here as well.
At time of my engine build, never planned to tow or go below 3000' elevation (I live at 5300'). Now, I seem to be doing both. The biggest obstacle now being the 10.15:1 compression ratio (whoda thunk?). Currently, carb is over jetted a bit and even down to around 1000' no real issues if I run 91 gas. Towing seems to open up a whole other can of worms. Engine will ping pulling uphill and am looking for ways to compensate. Hindsight being what it is, I should've pulled some timing out, but didn't and now also looking for other ideas, even if overkill, to prevent any problems since have plans to go to 0'. So, in addition to timing and maybe re-jetting at a certain elevation point, my mind tells me to maybe install an EGR setup. Any power loss should still be a net gain as elevation drops considering that here @ 5300' I'm already losing abt 15%, hence why engine was built the way it was. I normally run regular gas with zero issues. Wondering anyone's thoughts on this?
Currently, 390 4v, stock heads & intake, RV cam, headers, dual exhaust. Rated 360 hp, 460lb/ft torque. Automatic trans. 4000lb Shasta in tow.

 

Is the intake, heads made for EGR?
If not how do you plan on adding it?
What carb & intake you running?
I take it you are running cast iron heads?

I wonder if MSD dial back timing could work for you?
You set timing where you dont get pining and as you move down and get pinging you dial out advance to stop it.
Would not need to get out to move the dist.

At one time Holley made dial a jet that did the same as the dial back timing.
With a AFR gauge you could see it running rich and you dial it back.
I think I would look into both if you can still get them.

The other thing would be EFI like maybe a Sniper kit.
This way it is always adjusting to run the right AFR and it can adjust timing too.

I would like to hear what others have to say about this?
Dave ----

 

I like the idea of the Sniper too. Before I read Daves post that was what I was thinking would be a good way to go. Fuel injection would get you around some of the issues, at least. And seems easier than an EGR setup.

 

I think your problem is your dynamic compression with the cam you have now. Most "RV" cams are ground to raise the dynamic compression over stock to help engines that had a low static compression from the factory. You can run 10-1 static compression if you pick a cam that keeps the dynamic compression at 8-1 or less.
I know you don't want to change cams, but it may be the only cure if you are going to make big altitude changes.
Here is a calculator, if you know your cam specs see what your dynamic is. Keep in mind you need to use seat to seat numbers not @.050 for it to be accurate.
Wallace Racing: Dynamic Compression Ratio Calculator

 

So you are thinking with the lower compression no pinging?
I guess that would take care of 1 part of the issues he has.
Dialing back timing would stop the pinging also.

What do we do about the lean / rich issue going up & down the hill?
That is not as easy as turning the dist. for timing.

BTW I have used Wallace Racing site for the math, great site
Dave ----

 

Is the intake, heads made for EGR? Nope
If not how do you plan on adding it? Don't know. Haven't thought that far ahead
What carb & intake you running? Holley670 vac secondaries, cast iron Ford
I take it you are running cast iron heads? Yes

As far as how/what method is used to adjust timing, my concern is will it be enough to solve issue. Modern engines use multiple methods.
As far as EFI, basic and simple is what I prefer. Not sure the cost is justified especially when the occasional re-jet is simple to do. Would still need timing control and cost keeps climbing.

As far as changing cams goes, I have considered it but would open up another can. As things are now, based on altitude loss (remember I'm at 5300') my theoretical dynamic CR is just slightly over 8:1. That's how I can normally run on regular gas with no issues. How much compression would be lost with a different cam and at what point does the engine become a pig at higher elevations? 7000-8000' is not out of the question now too. Lower compression would help with the pinging but, also, with a different cam comes changes in power band and may be more appropriate for a car as opposed to a truck.

Yes, I want to have my cake and eat it too

 

High compression has tendency to ignite lower octane fuels before spark.
I'm not too worried abt lean/rich issues as have no problems with re-jetting as needed and do think as jetted now have quite a bit of wiggle room built in. Also, with my manual choke, I can play with things on the fly as well.

 

You need EFI, not EGR.
EFI will compensate for altitude and load.
EGR is like taking a poo on a plate and serving for lunch.

 

Lots of things in play here. EGR lowers combustion temperatures and helps prevent pinging.

 

So it looks like EGR is out as you dont have anything in place to make it happen easily.

Look at MSD dial back timing to see if it will work for you and with your dist.
Timing you want to get under control as that will kill your motor / pistons.

As for jet changes I dont know how often you go up & down but you would have to jet change up top and again down at the bottom.
To me that is not as easy as it sounds even on a Holley.
I guess you could run it lean and use the choke to make it richer.
Dose Holley still make dial a jet?

I wonder how much it would run to do timing & jet changes as needed and for EFI?
Dave ----

 

I do like the idea of the dial back controller. Makes adjustment real simple and can do it on the fly.
Changing jets are easy and certainly don't mind doing that as elevation changes warrant. Will look into holley dial a jet. Sounds amazing if still available.
Currently run a bit rich and can still play with choke to richen further even though not optimal. I would never purposely run lean and try to fudge the other way tho. Way too risky there.

 

Where is the air coming into the carb from? Is it pre-heated by the radiator and exhaust manifolds? Cooler intake air temperatures will go a long way in reducing detonation. Use an intake with ducts that go forward and pull in cold outside air from in front of the radiator support.

Do you have an efficient exhaust system that can carry away exhaust without restriction? Backpressure will bottle up exhaust (heat) in the chamber and will make detonation more likely. Properly sized headers and dual exhaust with non-restrictive mufflers can scavenge the exhaust port/chamber and pull exhaust out on its own, which also pulls more fresh air/fuel in during the overlap period. The engine must be able to breathe freely to get cool air/fuel in and heat out.

What is the deck height, and what is the chamber design? You can get away with a lot more compression than normal if you run a tight deck height with flat top pistons and chambers that have flat quench pads. .040" between the piston top and quench pad is optimal for squeezing the air/fuel mix out from between the tight deck clearance areas into the open part of the chamber at really high velocity near/at tdc, increasing swirl/mixing of the air and fuel for a more even mix and cooling off hot spots in the chamber. Any sharp edges in the chamber need to be smoothed to prevent hot spots.

Timing control is needed if you can get a more efficient chamber- it'll need less total advance so you'll need a way to limit full advance under load. Not sure what's available for Ford engines as I'm mostly a VW and Chevy guy, but if you can get a Chevy style HEI distributor it's easy to get a kit that will allow you to set the rate and amount of both centrifugal advance and the total amount of vacuum advance.

What temperature thermostat are you using, and is the radiator up to the task of shedding heat efficiently while under added load of towing? What condition is the water pump in- are the impeller blades rusty or worn down from cavitation? Keeping the heads as cool as possible will help with detonation. Use a coolant flush like "THERMOCURE" to clean out rust and scale from the coolant passages in the block and heads for improved heat transfer.

A small cam that makes low end torque isn't really ideal for towing- the first thing you do when you hit a hill with a load is to downshift. Pick a cam that makes good midrange power. A small cam with low compression will kill power everywhere in the rpm range.

Sniper or other EFI swap units are only as good as they are tuned to be- same as the carburetor you currently have. EFI also won't fix problems like the wrong cam, wrong compression, inefficient chamber design, restrictive exhaust, etc. I've seen tons of posts by people who thought adding efi would magically solve their cold start and poor mileage problems, then ended up with the same mpg as before because they never went further with tuning than what the built in auto-tune function provides. Get an Air/Fuel ratio gauge (AEM seems to be a current favorite) to see where your carb tune is at and where it needs to go to improve how its running. Under load you'll want to be at 12.5 - 12.75:1 with appropriate timing. Spend the money on redoing your heads and cam to get a more efficient combustion chamber instead of adding EFI.

Running e10 instead of pure gas will help slightly with detonation, the alcohol content will cool the chamber.

 

Much to digest here. Cold air intake being one of the simplest thing I've overlooked but, compared to EGR which is more efficient? May not be the easier choice. I'm in AZ. Outside temps can get a bit high.

 

Does it ping/rattle/knock at wide open (zero" vacuum), at part throttle (say 8-10"), or under both conditions?
Higher-octane gas would likely fix the former, less vacuum advance might fix the latter. You can determine if you have too much vacuum advance at part throttle by removing and plugging the vacuum hose. If that helps, maybe experiment by adjusting the vacuum pot to get less total advance to the distributor.
Some guys swear by mechanical-only spark advance even knowing they use more fuel at cruise.

 

The reason I said EFI was 2 fold
It will 1 control timing and 2 AFR for when going up and down.

Instead of going thru the cast iron heads why not a set of alum. heads.
Or dont they make a set for that motor?
Dave ----