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Proper gas for 374 engine
#1
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don1260
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I have a Caribbean that had to have the engine rebuilt.
When they went to start it after the rebuild...it started squirting gas out of the bowl and the fuel fuel pump wasn't working. My mechanic said the the ethanol in the gas at up the rubber in the fuel pump and bowl. He also said because of the compression ratio I have to run an avgal mixture or I might mess up my pistons. Does anyone have problems with todays gas in their 374's and how do you cope with it? Thanks for any help on this. Don

Posted on: 2011/2/21 17:36
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Re: Proper gas for 374 engine
#2
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Owen_Dyneto
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I run premium pump gasoline with the mandated 10% ethanol. No problems, but if I plan on a long, hard and high speed run, I add a bit of real tetraethyl lead just for a little extra protection of the exhaust valve seats. Aviation gasoline definately not required. But I'd recommend setting your ignition timing, with the grade of gasoline you intend to use, such that you have minimum spark knock which can, over the long haul, do severe damage to the pistons. You may find that setting your timing to 5-7 degrees BTDC is about correct, at least it is for my 56 Caribbean.

Posted on: 2011/2/21 17:50
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Re: Proper gas for 374 engine
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Rusty O\'Toole
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The rule I go by is the octane should look like the compression ratio. In other words today's 92 octane gas is for 9.2:1 compression engines.

Naturally this is not a hard and fast rule, just a rule of thumb. But you should be OK if your compression ratio is under 10:1.

If you notice signs of pinging or heat stress you can back off the timing, add octane booster or even a water injection unit. With water injection you can use over 10:1 on pump gas.

Look up the Thompson VitaMeter. It is a water injection unit that is period correct for your car. There are also new models available if you are not stuck on period authenticity.

Posted on: 2011/2/21 17:59
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Re: Proper gas for 374 engine
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Owen_Dyneto
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Rusty, the compression ratio of the 56 Caribbean engine was 10.0 to 1.

Posted on: 2011/2/21 18:16
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Re: Proper gas for 374 engine
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Rusty O\'Toole
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Here is an article on the Vitameter, first published in 1950. It also describes 2 similar gadgets, the Hydro Jector and Octagane. Plus a new type carburetor that feeds low octane fuel for cruising and hi octane when you step on the gas.

Go to this page and scroll down to the bottom.

http://www.gus-stories.org/PDF/Your%2 ... 201950/YourCar100_114.PDF

I believe the Vitameter was available thru the fifties and would be considered a contemporary accessory on any postwar Packard.

Posted on: 2011/2/21 18:20
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Re: Proper gas for 374 engine
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Jack Vines
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Answer - the highest octane sold at the pump plus a can of octane booster.

Answer to the question you didn't ask - Have your distributor rebuilt and recurved to 374" specs. Over the years, I've seen many Packard V8s with distributors swapped around. There are two manufacturers, Autolite and Delco. There are four different centrifugal and vacuum advance curves. Get the right one for your engine.

jack vines

Posted on: 2011/2/21 18:32
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Re: Proper gas for 374 engine
#7
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Owen_Dyneto
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Rusty, I'm not debating the merits of the Vitameter, I don't really know anything about it. But unless you want your engine compartment gussied up with non-authentic but period-correct gadgets, I'd think it's a lot easier, if you have a borderline preignition condition and don't want to retard the spark a bit, to just add some tetraethyl lead. Easy enough to buy, Jack Podell is the major source and ships everywhere. But for the vast majority of owners, it's really not necessary. But if you use it, there are toxicity issues, be sure to wear impervious gloves, don't breath the vapors, and wash up thoroughly. His TEL is a mixture in gasoline, normal treatment is about a quart per tankful of gas.

Posted on: 2011/2/21 18:37
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Re: Proper gas for 374 engine
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don1260
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Thanks for all the advise. I will print it all out and show it to my racecar mechanic. The distributor is orignal one. The block was the only thing my father had to change out. I found a list of pure gas (without enthanol). The highest octane rating was 93. I tried the tetraethyl before but it didn't seem to improve the performance. That might have be due to the really bad job the people that originally restore the engine. I will give it another try. I will also look up the info on the vitameter. Thanks again...Don

Posted on: 2011/2/21 19:24
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Re: Proper gas for 374 engine
#9
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Rusty O\'Toole
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Tetraethyl lead will not improve performance. All it does is prevent knock.

Any engine will run best, perform best, and run coolest on the correct octane gas. In other words if you have an old, low compression engine it will run best on low octane fuel.

A high compression engine needs high octane fuel to prevent knock, ping and overheating. It does not contain any extra power. Water injection (actually water and alcohol) will cool down the firing charge and allow the use of lower octane fuel.

The article I linked to says the Vitameter uses a special anti knock mixture called Vitol consisting of alcohol, 85%. Water, 15% plus 3cc of Tetraethyl lead per gallon, and a rust inhibitor to protect the mechanism.

I'm not crazy about adding unnecessary gadgets either. But it is an option if all else fails.

Posted on: 2011/2/21 20:48
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Re: Proper gas for 374 engine
#10
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Randy Berger
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I run either Hi-test Amoco (B&P) or Hi-test Sunoco in my 56 400. I have hardened valve seats installed and RARELY take the car over 75. I do not have a pinging problem, but I am a little hard of hearing. No one else who has ridden with me has ever said they heard the engine ping. Engine was rebuilt in 99 (not bored) and crank cut.

Posted on: 2011/2/21 20:52
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