O/T: Leaded or Unleaded Gas??

[jorgensensc]

Hey all,
I got the '66 MG this weekend for the wife. It's a pretty cool little car. Long story short, right after the guy (he's 75) bought the car(the next day), he had medical problems and wasn't able to drive it. The car was sitting on empty when I bought it and I need to know what type of gas to put in it. The Chilton says it takes Leaded gas, 98 octane! He said when he bought it he put unleaded supreme in it for the trip home, but never thought to ask the previous owner. I know in order to run unleaded gas your supposed to do some head work.

My questions are:
If I run unleaded gas, will it hurt it if the heads haven't been reworked?
If I run Leaded gas will it mess up the engine if it is setup for unleaded gas?(I thought the lead was used as a lubricant)
How can I tell what kind of gas the car needs without removing the head?
Do I really need 98 octane gas?? I know I can add an additive, but really, 98 OCTANE?
Thanks for the help guys!

[stelth2002]

The lead shouldnt hurt the car unless it has a cat. If it does and you run lead thru it it will clog. So i would probably add some. If it says 98 octane, then put some 95 or whatever you have and see how it runs. Worse case is it pings under load and you drive home pretty easy with her for that tank.

['70_402]

if the motor has never been rebuilt then i would say add some lead additive just in case....

[Dean]

There is definitely some conflicting stories about the unleaded gas damaging the old leaded heads. The more I read the more I think it was a story made up by the gas companies. I've never had a problem with any of mine so far.

Fill the gas tank with the gas/octane that you are going to use and set the timing so it will not ping. You will be fine then.

I can't believe it needs 98 octane anyway. You will be running racing gas at that point and who can afford that all the time. The last time I filled my Chevette race car up it about broke the bank.

[StingRay]

Gee I thought the only leaded gas that you could get these days was aviation or racing fuel. Where would you buy leaded fuel? I think you are going to have to run unleaded. If it is designed for leaded 98 then you will probably be needing to do some or all of back off the timing, running a cooler t-stat ,running octane boost. If the head doesn't have hardened seats eventually you'll probably wear the seats out and have to have the head re-built.

[68racer]

How many miles are you intending to do? If it is about a thousand a year, you will get problems in about twenty years time.

Check carefully which octane rating system they are referring to. The US and European are different, refer to MG sites on the net.

If you want a recon head it may be cheaper to ship one from the UK. I know a good shipping agent.

That engine is as common as grass here, good luck.

[smitty62]

You can certainly do as you please, but if it was mine, I'd run 97 octane unleaded. Those tiny 4 holers won't take much pre-igniting. Watch your temp gauge too. Where would you get leaded anyway besides at a race track or airport? Additives are a worthless scam. Some people won't like to hear that but they are the ones that have invested a small? fortune in them over the years.

[Palf70Step]

I agree with smitty62. Run the highest octaine you can find. Those British fours need it. Got to remember 2 things.
1. In 1966 there was nothing but leaded gas. It is not a big deal either if you run unleaded.

2. Hitest back them was 98 or above as the norm. I ran 103 or 104 from the pump in my Hiperf cars (Sunoco 260). It may be a 4 popper but they have some good/high compression and need the octaine. They will self destruct pretty easy if you try to cheat them of that high ocatine for too long.

(prior owner of Truimph TR4 and TR4a and TR7 and MGA).

On another note. Look the electronics over VERY carefully. Lucas Electronics, whioch I believe was used in all the British vehicles of that era and are notorious for failure. Starters, starter relays, alternators, and regulators failed at alarming rates back then.

But they are FUN to drive. Hope you the the Mrs enjoy it!

[jorgensensc]

Thanks for all of the info guys. I think the best octane I can get around here is 93. Are the octane additives really crap? Can anyone recommend a good Octane additive? What about a good lead additive? Thanks again for all of the help!

[dwaite72lnghrn]

I think the english car use a different method to calculate octane. 98 RON used in england is equal to about 89 RMC used in the USofA. I looked it up awhile back on a google search. If you get pinging on 89 try 92 then water injection.

[Palf70Step]

I don't remember either, but there has been changes in the way octane has been calculated over the last 40 years. I really don't think you'll have a problem running today's high test in it. That's what the local folks here do in those style cars or other old hipo engines.

[smitty62]

Tetraethyl lead has been outlawed for years. There is no "lead" additive and would be worthless if you had any--how much would you use? Just pouring something in a tank of gas is not nearly accurate enough for a proper mixture. All other additives are just as good as the so-called "lead" additives--ie; they're all JUNK.
If the MG was made for US export the octane data in the manual should be accurate for the US.

[Terry S]

Unleaded gas will cause the valve seats/guides to wear out prematurely, but not so mutch that it's probably worth doing anything about it. I've had two 60's era mgb's and I ran unlead in both of them for years without noticing any effects other than what was brought on by the fact that the engines were going on 40 years old with no rebuild.

I personally would run the highest octane pump gas that I could afford and forget about it. The factory shop manual for these cars (not the same thing as a chiltons manual!) called out different timing settings depending on what octane gas you were running. I can't remember the numbers exactly, but you might try finding that information with a google search.

I second the fact that the lucas electrical system on all these cars was pure junk, as were the dual side draft carbs. The carbs afe difficult if not impossible to keep synched and sooner or later you'll have electrical problems, guaranteed.

One more tip, in case you haven't already discovered it. LMC Trucks has a sister company out of the same warehouse in KC called Victoria British Limited, which is an excellent resource for parts for those cars.

Have fun!

TS

[walker]

T'aint no lead no mo' in automotive fuel. You can get it in av gas, but running av gas has its own set of problems, including harsh additives to prevent if from detonating, and octane ratings that are for high altitudes that differ from those here on the ground.
IMO just run it on high octane till the valves give you trouble the rebuild the head. But most of all enjoy it.

[Terry S]

Oh, one more thing, 100 low lead av gas still has more tetraethyl lead in it than old style leaded car gas, but it's illegal to put into anything that's licensed for road use, since there's no road tax on it. Also, around here, avgas costs about $2.70 per gallon. If you drive the car 5,000 miles a year (assuming about 20 mpg). you would be spending an extra $250 per year compaired to pump gas. It's been a while since I priced a top end job on an MG, but I'm guessing it's probably some where around $500 or less. If that's the case, you could go thru the head every two years and shill be ahead in the game.

[jorgensensc]

Thanks guys!! Y'all have answered the questions perfectly.
Terry S, I actually got a catalog for them with the car. The guy was planning on buying all kinds of stuff for the car.
We enjoyed it for all of a half a day before the Master Cylinder went south. The PO had a new slave cylinder for the clutch put on, but never drove the car. Well, when we drove the car the master cylinder went out after a few miles of driveing. Just goes to show you that you should always replace both at the same time. I guess the pressure from the slave was too much for the old Master. By the way, The brakes went out at the same time. It seems this car uses one master cylinder for both the brakes and the clutch. Great for simplicity, but so much for safety
I already had an experience with the electrical system, and yes it is Lucas. Seems the electric fuel pump was wired backwards, that is why the car wouldn't start, it only took me about 30 minutes to figure it out, but I can see the issues coming. So far the lights and signals work, but the only gauge that works is the oil pressure gauge. Can't wait for that nightmare!!!
By the Way, I noticed the positive side of the battery bolted to the chassis (as per Lucas Positive Ground). If I need to jump the car, do I still hook the cables up normally, red to red? or do I reverse them?

[jimfulco]

Red to red. Just don't let the cars touch.

And on a lighter note...
Why do the British drink warm beer?
.
.
.
.
.
.
Because they have Lucas refrigerators.

[72C203503ONTHETREE]

Lucas elctronics----the prince of darkness.

[mrein3]

I don't doubt the fact that Dean has never had a problem with unleaded gas damaging heads but I have.
When I bought my truck in 1994 is had a 350 of questionable lineage. The guy I bought it from lived in an area that had leaded gas available and that is all he put in it. 6 months after I got it I noticed a remarkable loss of power. I did a compression test and discovered I lost two cylinders to low compression. When I pulled the heads two of the valves - one in each cylinder with the low compression - were sucked way up in to the head. I handed them over to my rebuilder and he recommend I make boat anchors out of them and start with a set from the yard for my valve job. He set those heads up for unleaded gas and I haven't had a problem since. All I have been able to put in the truck since then is unleaded gas.

The old timers tell me Chevrolet changed their heads in 1971 for no or low leaded gas. I have two 1971 engines (307 and 350) and one 1972 engine (307) that have never had a problem and all ran the last 15 or so years on unleaded gas.

Originally posted by Dean
There is definitely some conflicting stories about the unleaded gas damaging the old leaded heads. The more I read the more I think it was a story made up by the gas companies. I've never had a problem with any of mine so far.

Fill the gas tank with the gas/octane that you are going to use and set the timing so it will not ping. You will be fine then.

I can't believe it needs 98 octane anyway. You will be running racing gas at that point and who can afford that all the time. The last time I filled my Chevette race car up it about broke the bank.

[smitty62]

Mrein3: Were you more likely to work the '94 harder than the other trucks, such as pulling a heavy trailer? The only time I have seen recessed valves in a SBC has been a very hard worked truck--not like most of us use our pickups. Of course, you may just have been stuck with a poor pair of heads to begin with. Adding hardened seats to heads are a good idea if you have the engine down anyway, or you are going to be working it hard (hot) but I would never tear one down just for the seats.

[shortymac83]

I'd throw gas in it and run it. We do that with our 1951 Dodge M37 flatheads, I do it with my C10's unrebuilt 250, and everyone I know runs the "leaded" cars with at least mid-grade unleaded. Not a one of them pings, detonates or blows up.

[mrein3]

Originally posted by smitty62
Mrein3: Were you more likely to work the '94 harder than the other trucks, such as pulling a heavy trailer? The only time I have seen recessed valves in a SBC has been a very hard worked truck--not like most of us use our pickups. Of course, you may just have been stuck with a poor pair of heads to begin with. Adding hardened seats to heads are a good idea if you have the engine down anyway, or you are going to be working it hard (hot) but I would never tear one down just for the seats.

The truck I was talking about wasn't a 94, it is the truck in my signature that I bought in 94. The block is out of a 78 truck, the heads from who knows where. The truck actually lead a charmed life in the 6 or 7 months I had it. Then that November on the way up deer hunting I went to pass somebody on a 2-lane. I got next to the vehicle and it started losing power.
Long story short my rebuild guy said toss the heads. He got me a different pair out of the bone yard and put hardened seats in and did something he calls "bronzwal" or something like that. I just said do it right. $250 later I had a fresh set of heads that are still on there. (100/head for the valve job and 25/head for the different heads)
The bottom end of that engine is finally making noise so I can now justify a new engine.
You're right, I'd never take one apart that was working. However mine had to come apart at that time.