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P 15 hardened valve seats


larryconnors

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Larry,

Yes. These engines could have run unleaded gas in the 1930s.

-Randy

Just to reaffirm Randy's comment: All Plymouth L-6 engines from 1933 up had hardened exhaust valve seats from the factory. The 1933 sales literature says that it nearly does away with the need for valve grinding.

Keep in mind too that the cheap gas back then was unleaded and you had to pay extra to "fill it with Ethyl" and the Plymouth was a car sold to the economy minded many of whom would not pay extra.

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Is it true that P15's came with hardened valve seats and that I don't have to add lead substitute with valve lubrication to my fuel?

That's good news. I guess I'll give the gunk lead substitute that I bought to my next door nighbor for his 35 ford.

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Whoa !! Todd...... did you mean to say that unleaded gas WAS USED IN THE 30'S?

i dont think so..the lower rated fuel was leaded but lower octane....Ethyl was just a higher octane.....

lets see the response....

bill

You think you are right that by the late 40s, 50s and 60s pretty much all gasoline had Ethyl. Exceptions being Amco (I think) on the East Coast and Richfield (used a boron based anti-knock) on the west coast.

We know that all gasoline was unleaded, but might have had other anti-knock additives, prior to July of '23 when Ethyl was introduced for sale. And it cost something like 10% to 20% more per gallon for Ethyl gasoline than for non-Ethyl (non-leaded) up through at least the mid-1930s.

Because of the extra cost the majority of the motoring public were slow to start buying it. So for years after the introduction if you didn't specifically pay extra for the Ethyl you didn't get it. If Ethyl was in all grades of gasoline then there would have been little need for the Ethyl Corporation to exhort the public to say "Fill it with Ethyl" when getting gasoline. And those Ethyl ads in magazines run all through the '30s. So I think it is a safe bet that regular gas through at least the mid-1930s was unleaded.

So the question becomes when did regular get Ethyl and "Ethyl" get relabeled as "high test" or "premium". Based on the strong branding pursed by the Ethyl Corporation, I'm pretty sure that in the pre-WW2 era any gasoline company that had Ethyl anti-knock additive in all of its grades of gasoline would have proudly advertised it and I haven't seen evidence of that. I suspect that regular grade gasoline got Ethyl when the higher compression short stroke OHV V8 engines were introduced after WW2 but I haven't found definitive information for that.

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very interesting and great info. then why not all cars back then having hardened seats.?? i remember regular and Ethyl. and I remember the switch to high test and premium. sounds like a time when gas was

standard and grades were established with differing amounts ? rain=sing octane. Sunoco used to have a 'dial-it" system where you could dial your octane rating and pay accordingly..

interesting stuff.

bill

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very interesting and great info. then why not all cars back then having hardened seats.??

Cost of manufacture and people were used to having valve jobs done pretty regularly so they didn't expect otherwise.

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Am I to understand, then, that I don't need to add a lead substitute to my gas for my '49 Dodge?

Hi, we have similar cars, mine is a 50 Meadowbrook.

Hows your car running now?

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Can't put my hands on it just now but I read somewhere that the gasoline of old days wouldn't match up to the gasoline we have now as for octane, etc. In other words, the best gasoline then wouldn't match up to the "worst" gasoline now.....

I haven't found anything authoritative but I have found a reference claiming that typical octane ratings in the mid-1920s ranged from 40 to 60. And another one claiming that just after WW2 regular was typically 79 and premium was 85 octane. I am not sure, but I think they typically used the research number back then which is higher than the "pump octane" rating used nowadays which is the average of the research and motor test cycles.

If true then, yes, the lowest octane gas you can get now (87 here in California) is better than the highest octane that you could have purchased up until maybe 1950 or so.

If I can find some authoritative source(s), I'll post them.

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Before WW2 gas stations sold Premium, Regular and Straight run gas. The straight run gas was low octane with NO additives or lead. It was meant for dump trucks, hit or miss engines, tractors and other low compression engines. It was great for Model Ts, Rolls Royce Silver Ghosts and other older model cars.It was only about 50 or 55 octane. Regular around 65, Premium 75.

The real heavily leaded high octane gas did not come in until 1953 or 1954. Before that even Cadillac and Chrysler hemi had a compression ratio of 7.5:1. It was not many years before pump gas of 100 octane became available and compression ratios of 10:1 were offered in the hot performance cars.

So, practically all cars before 1953 or 54 will run on unleaded gas with no trouble. They were designed for gas of lower octane than anything you will find today, and little or no lead.

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