Technical Reducing octane requirement

I have a 1970 302 that even though it was a 2 bbl originally it still has 9.5 to 10 compression so it really is not happy with regular gas,years ago I read that adding a EGR valve could reduce the octane requirement of a engine. I screwed up a few years ago when I burnt a valve and had the heads off and could have found a set with slightly larger combustion chambers but that did not cross my mind at that time. Back when premium was only 20 cents more this would not be a problem but now it could be a dollar more and the car the engine is in has a 24 gallon tank so a full tank of gas will be 24 dollars more so a intake change with a EGR might pay for itself and not hurt the engine. Has anyone ever done this or know anyone that has and it actually worked.

 

Thicker head gaskets, turn the timing down some, octane booster or try mid. grade gas. How many miles do you drive this car? The expense might not be worth it in the end. I also found that when I moved from LI (sea level) to Flagstaff AZ (7000) elevation I could use regular gas in my 10 to 1 comp engine. I don't expect that you will move.

 

EGR will reduce pinging. To add it you need to get all the controls that go with it. It's not just as simple as connecting a vacuum line. It really needs to be a setup tailored to your specific engine. I remember early EGR setups on Fords causing a part throttle surge.

 

I would try less timing, less aggresive timing curve and more fuel, try running it without the vacuum advance plugged in . Try different brands of gas, I've always found that Standard Gas was piss water even my new vehicle would rattle on. Also put a cooler thermostat in it.
I would change the cam before putting EGR on it, giving it 10 two 15 degrees more duration razing peek torque 500 rpm.

 

not so much more duration as late intake closing. Crower offered cams that did this in early 70's for all of us with 9.5+:1 engines when even premium gas went crappy. I added a cheap home made water injection to get by. Used a $20 windshield washer, a $10 aquarium valve to fine tune and a $30? Ford vacuum switch that turned on a dash warning of poor economy. Best to add a $25 valve that is used to shut off power to fuel pump if no oil pressure so you don't fill oil pan if switch on and engine not running. Vara jection on that site for $115.

 

I have everything except for a intake to put the EGR on and its also for a 302,I am going to back off the base timing first and see how it does. Not really wanting to pull the heads off again and thought a intake change would be the eadiest to do. The car is my summer daily driver old car and I do drive it a bit.

 

I have been thinking about moving to a warmer climate.

 

I forgot I have a 90s 302 in a friends garage that I can convert to a carb and keep that 1970 302 and my 4 speed for a lighter hotrod project,its presently in my 65 custom 500 and would be better on a early Falcon.

 

I've never had any issues with running 'regular fuel' SBFs on 'regular' pump gas, even the stuff they sell these days. But I have found that it does matter where you get vacuum for the vacuum advance. I've always gotten the best results with a manifold source, not at the carb, with initial timing at 8 degrees BTDC.

The early carb versions of EGR aren't anywhere near as precise as the new EFI-driven versions. I can see a calibration nightmare...

 

It's a damned if I do, damned if I don't deal.
If the car is a special occasion I only drive it for fun rig. I don't see the savings of making changes unless you have a lot of road trips planned.

Basically how many miles you drive it a year divided by mpg x cost per gallon as apposed to how much you will spend to save that difference.
That said, I have two OT daily drivers that both take premium and it does hit you hard in the wallet on a daily diver.

Personally If I had a later engine that was designed for unleaded regular that I could bolt in with just a carb swap and be able to drive the car on anything that said "gas" on the pump that is what I'd do rather than make changes to the engine that is in it.

That said I have a 75 Cad 500 in my 71 GMC haul anything tow any thing for the hot rods truck that I got primarily because it was lower compression and prepped for unleaded gas from the get go. Has funky air injection tubes in the heads but I don't have to worry about the grade of gas it drinks.

 

Water injection/alcohol mix injection like the old Edelbrock vari-jection might work?

 

That 70 302 runs better then any of my later 302s and do not want to make it run worse,its not a big power house but just runs so good so I will back off the timing some since I think I have it set around 12 BTC and see how it does. I have most of the parts to convert the 90s 302 to carb except for timing chain cover and need to get a front sump oil pan and pick up tube.

 

I have a SBF that was really bad about pinging on regular. After some detective work, I found that the mechanical advance was stuck. The grease between the upper and lower shafts had hardened with age and caused the upper shaft to stick full advance. Cleaned everything up, added a bit of high-temp grease and no more pinging.

 

I might have to look further in the distributor,the engine had a slight bog right above idle and I noticed when I hooked the vacumn pump to the distributor the idle barely went up. It has a adjustable vacumn advance and I had it where it was barely advancing so I adjusted it out a couple turns and the bog is gone but still pinging when on a load sometimes but running much better. It has a late 70s Duraspark ignition.

 

try setting secondaries to open about 2500 rpm - maybe add a MSD 5 box? - normal timing should be 35-38 degrees as a starting point

 

I have a .60 over 350 with 461 heads. Have to keep the timing down to keep the pinging to a minimum. It was in one of my daily’s and did ok on 87, ran much better on 89+
I installed it in my sons c40 flat bed. This engine doesn’t perform well with the truck 4 speed. Doesn’t like being lugged during a hard pull. Pings real bad. The high compression and mild cam isn’t happy in this truck.
Probably swap it out for a straight 6.
My other daily has a 73 302. Not a lot of HP, but runs great on cheap gas.
I also built a 500 caddy. Guys asked me why I built a low compression smog version. Your issue with fuel is the reason why.

 

It may be carbon try some upper engine cleaner and I have used water injection systems.

 

If you have Duraspark, not only can the advance mechanism get gummed up, but there is also a slotted system where you can change the amount of advance the distributor can do. It's why you don't see 'recurve' kits for Durasparks really just re spring kits.

Check out the is site for better details.
http://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_index.html


As for adding EGR, if you did a bunch of highway part throttle driving it might be beneficial in MPGs, but you would have to spend some time on retuning to get it right. You would need a carb that had a decent ported part throttle or 'EGR' port and would have to watch the timing curve so as to have advanced timing when the EGR was activated(ported timing, not main).
Ford EGR carb intakes are kinda crappy, really small intake ports, and really flat. Best one would be the Edelbrock Performer EGR, ports are as tall as head ports.

EGR works by diluting the air intake mixture, hot inert exhaust gases are recirculated into the intake and cool the combustion chamber temps due to only a partial fill with fresh air/fuel. But this requires more advanced timing to get the combustion to be acceptable/useful at part throttle.

I'd look at making sure everything is working correctly, as-is, first. Then look into changing things. Don't forget that carbon buildup can cause detonation issues as well. Not only by adding compression artificially but by creating hot spots. Carbon acts like a sponge for fuel(just like lighter fuel on charcoal briquettes), it can saturate and cause undesirable running characteristics.

Water spray down the throat at part throttle or the ole Sea Foam treatment can do wonders for a pinger.

 

Thicker head gaskets works but reduces squish that creates chamber turbulence that limits pinging in the first place ...Best to try other tricks...

 

If you keep backing off the timing your engine will run slightly hotter, which is the opposite of what you want. I would try keeping under hood temps down also. Keep the fuel cooler, water wetter?, 160 degree thermostat, maybe even colder plugs.

 

Put the stock valve covers back on and the factory timing is at 6 and I had it at 12 so I backed it down to 8 and going on a test drive after I finish a beer,it has a 195 thermostat and will eventually put a 180 in it.

 

I don't know about the gas in your area, but I don't even run regular in my lawn mower or tractor. My drivers get mid grade, lawn equipment gets non ethanol mid grade. My 99 F150 will ping on regular, and it's got all that computer controlled injection and ignition junk that I don't understand.

 

Lawn mowers will be getting 100 percent gas when I run out,seems to still run good with the timing set back but further drives will be needed.

 

I've played with the Duraspark on my 351W, and eliminated/reduced the pinging. Can't give too many details, as I did it quite some time ago, but basically cleaned and lubed it, changed some springs, and added an adjustable vacuum advance.

 

The one I have has a adjustable vacumn advance and need to allow for a little more now that I took some of the base timing out,the carb I have according to Holley was supposed to have 68 jets in the primaries but had 66s so I stepped them up one size a few years ago so thinking about going one size again.

 

Drop a bore scope in a plug hole and check the pistons for carbon cake. Run nitro cleaner in the tank and take it for a 30 minute Italian tune-up once a week.

Joe

 

I think I was trying to get away with too much initial timing and should have looked it up instead of going with 10 degrees that I usually start with on any engine and eventually go for more,probably will have to go through this with my 65 Montclair that has a fresh original 390 when I start driving it more frequently and a few years ago when I put a 66 390 in my Country Squire I had to play with it to run good on the gas then.

 

If your only complaint is that filling the tank is $24 more than running cheaper gas, readjust your fuel tank sender so it reads “empty” when the tank is half full. Now your fill up is only $12 more. Problem solved.

 

I think I had been using premium when I first got it on the road and that is why I was trying to get away with so much timing and never set it back when I went to regular. With what I done over the last few days has helped and I hope stepping up the jet size will get me closer to what I would like but its still a engine that was designed to run on almost 100 octane regular that will never be again.

 

If the complaint is pinging under load , then less initial & more vacuum advance is called for . Instead of changing the main jets , increase the delivery systems initiated under load, I.e. the power valve & accelerator pump circuits .