What octane fuel should I use - 413 engine?

Winnielover4078 · November 18, 2008, 08:39 PM

Sent: 10/28/2005 10:29 AM

When I bought my 72 brave last year, the previous owner said he always ran premium fuel in it. The owners manual says to use minimum 91 octane fuel. Do I really have to use premium with these prices or can I bump it down a little? The other question is regarding no lead fuel, do I need to be adding some kind of substitute to the fuel or is this engine o.k. with it? 413 engine......Thanks Kenny

xerofall · October 16, 2015, 12:43 PM

Searching and reading I'm still left with a few questions because of so many different factors and my own ignorance...

I live in Utah, most of the elevations are in the 6000 miles above sea level range. The typical fuel octane levels at the gas stations are 85/87/91. I have a 1973 Brave D20 with a 1978 Dodge 440 replacement engine.

My questions are: Do I need the leaded additive? What octane should I be putting into the tank?

MotorPro · October 16, 2015, 02:15 PM

Since I don't know the compression on your engine I will not give an Answer on your octane question. If your engine is a 1978 you do not need lead additive . Any engine after 1975 was built with hardened valve seats for unleaded gas.

Rickf1985 · October 16, 2015, 03:33 PM

And being a 78 it is almost guaranteed to be low compression so regular gas should be fine. If it stars pinging them move up one grade and try that.

xerofall · October 16, 2015, 04:10 PM

Quote from: MotorPro on October 16, 2015, 02:15 PM
Since I don't know the compression on your engine I will not give an Answer on your octane question. If your engine is a 1978 you do not need lead additive . Any engine after 1975 was built with hardened valve seats for unleaded gas.

I do not know the compression, sorry. Thanks for the info on the valve seals.

Quote from: Rickf1985 on October 16, 2015, 03:33 PM
And being a 78 it is almost guaranteed to be low compression so regular gas should be fine. If it stars pinging them move up one grade and try that.

I haven't had any issues in the past with the other engine... but I'm going to start driving it more since getting it back and all fixed up and needed to know what to use. If it starts pinging I will follow your instructions.

Thanks a ton everyone!

Lefty · October 16, 2015, 05:52 PM

I don't think your 1975 cut-off date is correct in every case. Our 1976 Chieftain had a sticker at the gas tank fillers that said it required regular leaded fuel only. I bought bottles of lead substitute by the case and kept it in the RV. As far as grade of fuel, mine had the stock compression ratio and ran fine on regular, even pulling hills.

EldoradoBill · October 16, 2015, 06:27 PM

All engines in the US from 1972 and up were designed to be used with unleaded fuel (some even earlier). My 72 Caddy had the big fuel fill opening but the manual recommended low lead or unleaded fuel. Even the one-ton and over trucks that skirted around the 1975 catalytic converter issue (I think by 79 even that loophole closed) that could use leaded fuel but would do fine on unleaded.

Don't forget that Amoco "white gas" which was the "Premium" since the 50s was always unleaded (it's what we used in our Coleman stoves and lamps).

Bill

Oz · October 18, 2015, 01:48 PM

Sent: 10/28/2005 12:25 PM

Using the Message Search, here's an abridged version of what I found from member contributions:

Since the engine was designed to run on leaded fuel, the un-leaded gas may cause the valve seats to wear over a long period of time or if you put like 60,000 miles on it in a year or two, so it shouldn't be a concern. Still, it has been advised to use lead additive, which is readily available, even at WalMart where I get mine, and not very costly.

If you ever have your heads worked on, it's advisable to have hardened valve seats installed at the time and you won't have to think about it anymore.

As for the octane, numerous members have run on 87 and haven't had any probems or noticeable difference in performance. However, if you get a "knock" or "ping" in your engine while under load and you know your timing is set correctly, you may want to go with a higher octane or use the lead additive.

denisondc · October 18, 2015, 01:49 PM

Sent: 10/28/2005 1:46 PM

The compression ratio in the 413-1 in a motorhome is only 8 to 1. It would probably run fine on 80 octane. If the prior owner was using premium, it could be the spark timing was over-advanced, causing some pinging, a.k.a. detonation. This could be caused by a broken spring in the centrifigual advance mechanism, or timing set way too early. The timing at an idle should be about 5 degrees BTDC, plus or minus 2 degrees. I run mine at 8 degrees BTDC, and it runs fine, no pinging.
I am assuming your has the original 413-1 engine. If it had a replacement 413(no dash) from one of the late 60s Chrysler cars, like a 300D, some of them had 10 to 1 compression ratios, and were NOT designed for motorhome use.
You should also lube the centrifugal advance mechanism, there is a felt wick under the rotor inside the distributor for this purpose. A drop or 2 of oil each 10k miles. (Which is how often i replace my points.)

As far as adding any lead substitue to protect the valves and valve seats in the head; the 413-1 heads came standard with induction hardened valve seats, and the exhaust valves had stellite faces. This is according to the Chrysler Technical Training pubs. The service manual lists the 413-1 having sodium filled valve stems, but solid valve stems for the 440-3 and 318-3.
I use the Bardahl additive, if I happen to have some with me, and happen to think of it, and Im not in a hurry, and if it isnt raining when I am putting the fuel in. My engine has passed 100,000 miles. When i need to rebuild it, I expect it to be due to corrosion on the piston rings from sitting so much of the time.

Winnielover4078 · October 18, 2015, 01:49 PM

Sent: 10/28/2005 9:00 PM

Thank you guys for your info. The next time I fill it up or put in some fuel I will try dropping to a lower octane. Gas in Vegas is about $2.90 gal for premium. diesel is worse $3.19 a gal which I run in my little v.w. jetta.

Floridabaked57 · October 18, 2015, 01:50 PM

Sent: 10/29/2005 2:32 PM

Mine ran on regular 87 octane, no additives, no misses. Ran better than my '05 Hyundai!!! Also a 413, 1971 with 121,000 miles on it. And I was the only one smokin'... : )

John T.

terrapin619 · October 18, 2015, 01:50 PM

Sent: 1/8/2006 2:14 AM

My dad had a 72 titan with a 413 in it we went to cabo San Lucas and other baja spots many times in it and also to alaska...and back. It would ping on mexican gas which was 94 octane so he installed an Edelbrock water injection system and not only did the pinging stop, but he always said he got better mileage. We were always either towing a 20' boat or a 4X4 mini truck.

ClydesdaleKevin · October 18, 2015, 01:50 PM

Sent: 1/8/2006 10:27 AM

I also didn't know what octane to use when we first bought our rig with a 413, and asked the very same question. I followed Dave Denison's advice, which as always is reliable and correct: The 413 has a low compression ratio, the valves are already hardened, and they are filled with sodium to keep them cool, just like a Porche...lol.

I have put over 10,000 miles on our engine in the last 7 months or so...and I run the lowest, cheapest octane I can find for it. I don't bother with any fuel additives, since I fill the darn thing so often...and I don't have any ping or predetonation.

Kev

denisondc · October 18, 2015, 01:51 PM

Sent: 1/8/2006 8:11 PM

I had pinging problems with pemex regular, back in the 1980's and early 90s, in a 1972 Chevy powered by the 6 cyl 250 c.i. engine.. I have only bought gasoline in Mexico in the last 2 years now, still regular, and have had no problems with pingin in my cars; an 87 omni and an 87 dodge caravan.

xerofall · October 18, 2015, 01:51 PM

Searching and reading I'm still left with a few questions because of so many different factors and my own ignorance...
I live in Utah, most of the elevations are in the 6000 miles above sea level range. The typical fuel octane levels at the gas stations are 85/87/91. I have a 1973 Brave D20 with a 1978 Dodge 440 replacement engine.

My questions are: Do I need the leaded additive? What octane should I be putting into the tank?

MotorPro · October 18, 2015, 01:52 PM

Since I don't know the compression on your engine I will not give an Answer on your octane question. If your engine is a 1978 you do not need lead additive . Any engine after 1975 was built with hardened valve seats for unleaded gas.

Rickf1985 · October 18, 2015, 01:53 PM

And being a 78 it is almost guaranteed to be low compression so regular gas should be fine. If it stars pinging them move up one grade and try that.

xerofall · October 18, 2015, 01:54 PM

Quote from: MotorPro on October 16, 2015, 02:15 PM
Since I don't know the compression on your engine I will not give an Answer on your octane question. If your engine is a 1978 you do not need lead additive . Any engine after 1975 was built with hardened valve seats for unleaded gas.

I do not know the compression, sorry. Thanks for the info on the valve seals.

Quote from: Rickf1985 on October 16, 2015, 03:33 PM
And being a 78 it is almost guaranteed to be low compression so regular gas should be fine. If it stars pinging them move up one grade and try that.

I haven't had any issues in the past with the other engine... but I'm going to start driving it more since getting it back and all fixed up and needed to know what to use. If it starts pinging I will follow your instructions.

Thanks a ton everyone!

MotorPro · October 18, 2015, 06:13 PM

Quote from: Lefty on October 16, 2015, 05:52 PM
I don't think your 1975 cut-off date is correct in every case. Our 1976 Chieftain had a sticker at the gas tank fillers that said it required regular leaded fuel only. I bought bottles of lead substitute by the case and kept it in the RV. As far as grade of fuel, mine had the stock compression ratio and ran fine on regular, even pulling hills.

even though the motorhome was exempt from emissions and thus unleaded gas because of the weight ,all engines after 1985 and many before that had hardened seats. Ford put hardened seats in many flatheads starting in the 1940's.

DRMousseau · October 19, 2015, 12:23 AM

"What octane fuel should I use?" THIS,... is the nightmare question of everyone, from mechanics to engineers, and everybody else too.

The Dodge 440 has had the compression ratio reduced from the 10's and 9's of it's early designs. I believe it's had the 8.2/1 compression ratio since '72 when it was "detuned" to meet the use of lower octane un-leaded fuels and the new emission standards. Of course it also suffered a reduction of fuel efficiency and the corresponding HP, performance and mileage. IMO,... a horrible era in the service departments of garages and shops and among mechanics who were forced into adhering to the new specs by law. Yes, RV's and many others were "exempt" from the early requirements, but eventually they were phased in too. I hated those years!!! As a mechanic, we were "REQUIRED" by law to eventually become "certified". I rebelled dearly, and delivered to customers everything I could to meet their expectations regardless of rules, until the day finally came,... and I was forced to quit, or meet the new laws requirements. And I became "an outlaw" mechanic/engineer.

IF,... your RV meets all dealer and manufacture specifications of equipment, adjustments and settings,... then use the fuel recommended and suggested. You shouldn't have any problems. Before this era, if these engines knocked or pinged a bit, we would jus add some "ethyl" at the gas station. If it still had these problems with a tank full of straight ethyl,... then we backed off on whatever settings necessary to prevent engine damage. Getting a stock 2 1/2ton '59 Caddie to bust it's tires into screamin' smoke was GREAT fun!!! And rather challenging against the lighter "Runners" of the late 60's!! LoL!!

If your engine knocks a bit goin up hills or when ya tromp on it, then either back the timing a bit or maybe try a grade of gas with higher octane. There's other adjustments too, if you REALLY know what your doin. I've run "hot" tune-ups that limited me to running in cooler temps below 70degrees. GREAT mileage and power,.... but too hot to run in warm summers with an old copper radiator. Heck, ya might find the cost per mile may actually be LESS with a good tune and a better gas grade!!! But ya have to be good to that engine.

Denisondc noted,.... "As far as adding any lead substitue to protect the valves and valve seats in the head; the 413-1 heads came standard with induction hardened valve seats, and the exhaust valves had stellite faces. This is according to the Chrysler Technical Training pubs. The service manual lists the 413-1 having sodium filled valve stems, but solid valve stems for the 440-3 and 318-3."

These "dash-3" engines have redesigned heads to run cooler with added sparkplug changes too. This allowed those strong solid valves to be used without seat damage. These cooler running heads also helped prevent knock and ping in the heavy industrial use of these engines.