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Discussion Starter #1
Hey everybody! Guess what! I just got done rebuilding my 350 v8 for my 75 El Camino. I put some double hump heads on it, and they do not have hardened valve seats. I intend to drive this car almost daily. Should I run leaded fuel additive, or a little bit of diesel in my fuel, or what? Is there a good study on it? I've read about it on other forums, and nobody really came up with a definitive conclusion. I always run 91 octane, usually with no ethanol. This is a high compression engine. I read about the rash of head jobs back in the 70s, and something about ultra lean fuel tuning for the emissions tests having something to do with it.
 

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If the compression is under 9.75 I'd use 87, if over, I'd use 93... I wouldn't use any kind of additive. I've ran soft seat heads on unleaded fuel for decades without issue..
 

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Discussion Starter #5
Well... Alright. The old 350 had some exhaust valves that were sucked in. I decided ultimately to run a little diesel in the tank, help with the octane, and give it a little lube. Why not, right?
 

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Diesel in gasoline, don’t see any benefits in that. Just run regular low octane you’ll be fine.
 

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Diesel in gasoline, don’t see any benefits in that. Just run regular low octane you’ll be fine.
There is a benefit. It will help wipe all that nasty oil off the cylinder walls and ensure that an engine upgrade is required in the near future.
 

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Why not get hardened valve seats for those heads, unless you plan on rebuilding it again. It has been about 45 yrs since gas went unleaded.
The reason nobody hears about the leaded gas valve seat problem is because you have the last one without hardened seats. Either run lead additives or have valve seats installed.
 

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Discussion Starter #9
My machine shop that I use has worn out equipment, so they would be ruined if I took them there. I don't see how diesel fuel would be an issue in a gasoline engine, seeing as how it's fine in an actual diesel engine. Perhaps you guys can enlighten me.
 

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A diesel engine has the benefit of being able to actually burn the diesel. It will not burn in a gas engine unless it has a compression ratio of somewhere around 15 - 25 to 1. So it the diesel isn't burning what exactly is it doing? I suppose you might say it's lubing the valves? There isn't any lead in the diesel so no benefit from that either. It's either going to end up in the oil pan or out the tail pipe. I've never heard of anyone doing this in a gas engine, I even tried a google search and came up with nothing. Could you enlighten me on how you came up with this? Or do you have some uncle that told you this was a good idea? I'm actually very curious on this, seen lots of stuff added to gas from moth balls to hydrazine, but this is the first time I heard of someone adding diesel.
 

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Discussion Starter #11
A diesel engine has the benefit of being able to actually burn the diesel. It will not burn in a gas engine unless it has a compression ratio of somewhere around 15 - 25 to 1. So it the diesel isn't burning what exactly is it doing? I suppose you might say it's lubing the valves? There isn't any lead in the diesel so no benefit from that either. It's either going to end up in the oil pan or out the tail pipe. I've never heard of anyone doing this in a gas engine, I even tried a google search and came up with nothing. Could you enlighten me on how you came up with this? Or do you have some uncle that told you this was a good idea? I'm actually very curious on this, seen lots of stuff added to gas from moth balls to hydrazine, but this is the first time I heard of someone adding diesel.
A diesel engine has the benefit of being able to actually burn the diesel. It will not burn in a gas engine unless it has a compression ratio of somewhere around 15 - 25 to 1. So it the diesel isn't burning what exactly is it doing? I suppose you might say it's lubing the valves? There isn't any lead in the diesel so no benefit from that either. It's either going to end up in the oil pan or out the tail pipe. I've never heard of anyone doing this in a gas engine, I even tried a google search and came up with nothing. Could you enlighten me on how you came up with this? Or do you have some uncle that told you this was a good idea? I'm actually very curious on this, seen lots of stuff added to gas from moth balls to hydrazine, but this is the first time I heard of someone adding diesel.
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My dad told me about it awhile back. Diesel fuel itself is like an oil, so yes, it seems to me that it could lubricate the valves, it’s a very small amount, but, the amount of lead that used to be in gasoline was also a very small amount, which makes me question what lead was actually used for in the first place. From my research, it seems that it was a good octane booster, higher octane runs cooler too, and the two “hot” valves in my old engine that were closer together than the others, were much more worn in. So I think the real issue is the heat. I’d think to boost the octane, for that cooler burn, that also lasts longer therefore, being more efficient than low octane fuel. About the moth balls though, I thought that destroyed cylinder walls, much like sugar is supposed to.
 

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Moth balls or naphthalene will actually raise octane of the fuel but it also very corrosive so you are correct about destroying the cylinder walls. As for the diesel I suppose it isn't really hurting anything and if you get the ratio right you could also have the added benefit of smoking all the mosquitoes out of the yard. You might be better off using lucas fuel conditioner or sea foam though.
 

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Discussion Starter #13
I'll look into those fuel conditioners. I do like the smoke though, haha. Have to take it easy on these cylinder walls especially, new rings and pistons, but the walls were worn and somewhat scored, it'll be alright, a little extra upper cylinder lube, just have to keep an eye on the oil level.
 

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I put over 50,000 on a 1964 Pontiac 389 running nothing but premium unleaded gasoline.. I would just use Premium gasoline, no additives..
 

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Discussion Starter #16
I always run the premium gasoline in my old engines. I think the biggest reason for valve issues is the fact that people try to run 87 octane in these old engines. They need that cooler burn from the higher octane.
 
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