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  #1  
Old 06-02-2006, 11:45 PM
dsmtuned dsmtuned is offline
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Default Advice on use of leaded fuel vs high octane.

There are some intelligent folks on this forum, so I thought I would ask this question here.

I just bought a 1955 Oldsmoblie Starfire 98. This car's engine was designed to run on Leaded Fuel.

My question is: Do you guys think that the engine will be damaged by running 91 octane unleaded fuel?

Should I use lead substitute?

Maybe I just need to add WI to it...


Thanks for any advice and/or knowledge.

-Craig
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  #2  
Old 07-02-2006, 06:32 PM
JohnA JohnA is offline
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It could be that the valve seats will be damaged without the lead content. That is on top of any damage due to the lower octane levels.
If you don't use lead substitute, it might be a good idea to run a tank full of leaded fuel every so often. That's what older European cars had to do when unleaded was phased out.
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  #3  
Old 08-02-2006, 03:21 AM
dsmtuned dsmtuned is offline
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Quote:
Originally Posted by JohnA
It could be that the valve seats will be damaged without the lead content. That is on top of any damage due to the lower octane levels.
If you don't use lead substitute, it might be a good idea to run a tank full of leaded fuel every so often. That's what older European cars had to do when unleaded was phased out.
Thanks John. Keep in mind that 91 octane is the highest that is readily available in Colorado, US.

Yeah I might just run the lead substitute to add the layer of protection. It's not all that expensive, just very polluting.

-Craig
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  #4  
Old 10-02-2006, 04:41 AM
hotrod hotrod is offline
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You can buy leaded race fuel here in Colorado from several fuel suppliers. Adding a couple gallons to the tank every few hundred miles should work for you. I'm not sure if that engine had soft valve seats or hard inserts so cannot say with certainty how much risk you have there. The real question is how many miles you plan on putting on the engine, will it be an occasional use only or a regular driver car.

At the time that car came out pump premium was in the mid 90 octane range so todays premium is not that far off the mark. By the late 1960s pump premium was nearly 100 octane so high performance engines built in that time period are more at risk for detonation damage if intended to run on leaded premium of the day.

Post up the exact engine CID and compression ratio of you know it, and I will check my 1958 motor manual to see if I can tell you anything useful about the heads.

Did the car have the owners manual ?

Larry
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Old 10-02-2006, 05:27 PM
dsmtuned dsmtuned is offline
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Quote:
Originally Posted by hotrod
You can buy leaded race fuel here in Colorado from several fuel suppliers. Adding a couple gallons to the tank every few hundred miles should work for you. I'm not sure if that engine had soft valve seats or hard inserts so cannot say with certainty how much risk you have there. The real question is how many miles you plan on putting on the engine, will it be an occasional use only or a regular driver car.

At the time that car came out pump premium was in the mid 90 octane range so todays premium is not that far off the mark. By the late 1960s pump premium was nearly 100 octane so high performance engines built in that time period are more at risk for detonation damage if intended to run on leaded premium of the day.

Post up the exact engine CID and compression ratio of you know it, and I will check my 1958 motor manual to see if I can tell you anything useful about the heads.

Did the car have the owners manual ?

Larry

Thanks Larry.

Yeah I guess I could run some Bandimere 110 leaded.

Here are the specs on the engine;
Model Designation: Oldsmobile Starfire Ninety-Eight
Wheel base: 126
Valve Location: In Head
Bore and Stroke: 3-7/8 x 3-7/16
Piston displacement, Cubic Inches: 324.31
Compression ratio: 8.50
Maximum Brake Horsepower: 202 @ 4000 RPM
Maximum Torque Lbs.Ft. 340 @ 2400 RPM
Normal Oil Pressure Pounds: 40

I don't plan on putting more than about 1500 miles per year on this car. It's just for crusing and won't be a race car.

I don't have an owner's manual, but I do have a few resources on the car. I haven't found anything other than "use the highest grade fuel available." Well that doesn't mean much considering that the fuels are different 50 years later.

I'd appreciate any insight you have Larry!

-Craig

PS- sorry I never got that Bandi video of your car to you. My camcorder took a dump that day...
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  #6  
Old 11-02-2006, 04:34 PM
hotrod hotrod is offline
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I couldn't find a clear picture of the head so cannot say for sure about valve seat inserts. You might want to call around to older engine rebuild shops they might have and old fart around that will remember if those heads had any problems. Other option is to Google classic Olds web sites.

They only had one V-8 engine from 1954 through 1956 (bore and stroke), the compression ratio going up each year from 1952 through 1958 as gasoline improved and power output became an important sales tool.

Year -- CR
1952 - 7.5
1953 - 8.00
1954 - 8.25
1955 - 8.5
1956 - 9.25
1957 - 9.50
1958 - 10.0

In 1955 the Buick and Cadillac were running 9.0 CR, Chrysler Hemi 8.5, Desoto 7.5 CR, Ford thunderbird 8.1 (man trans) 8.5 (auto), Lincoln & Mercury 8.5, Nash & Rambler started year with 7.8 CR but after 5000 engines jumped to 8.25, Packard 8.5 CR, Pontiac 8.0 CR,

You can assume that the 10.0 compression ratios expected to run on 98 -100 octane premium, so you can see your car, expected something in the low mid 90 octane range (without carbon build up). I can remember comments in magazines at the time that engines that ran on premium did not like running on 85 octane gasoline found in Mexico.

Engine had flat top pistons, valve springs were single with damper coil. Valve spring pressure rated at 156 lbs @ 1.5 inch compressed length. Lift intake and exhaust 0.403. By 1958 valve spring pressure had gone up to 227@ 1.437, with valve lift at 0.435.
In 1955 intake valve opened 14 deg BTDC, exhaust closed 14 deg ATDC. By 1958 valve events had moved to IO @ 16 deg BTDC , EC 20 ATDC.


Ignition point gap .016 , spark plug gap .030 distributor dwell angle 26 - 33 deg, fireing order 18736542, cyl numbered odd drivers side, even passenger side, #1 front drivers , #2 front passenger. Idle speed 400 rpm (transmission in drive). Minimum compression 120 psi . Normal oil pressure 35 - 45 psi.
Oil summer weight 20 , winter 10W ( this is before dual viscosity oils became common)

As you can see from the specs this is a pretty average tune engine for the 1950's. With the low valve spring pressures I doubt you have much to worry about.

Larry
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  #7  
Old 12-02-2006, 12:56 AM
dsmtuned dsmtuned is offline
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Great info to have.

Thanks for the details Larry!

-Craig
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  #8  
Old 13-02-2006, 11:15 AM
janis janis is offline
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Default Re: Advice on use of leaded fuel vs high octane.

Quote:
Originally Posted by dsmtuned
There are some intelligent folks on this forum, so I thought I would ask this question here.

I just bought a 1955 Oldsmoblie Starfire 98. This car's engine was designed to run on Leaded Fuel.

My question is: Do you guys think that the engine will be damaged by running 91 octane unleaded fuel?

Should I use lead substitute?

Maybe I just need to add WI to it...


Thanks for any advice and/or knowledge.

-Craig
I really do not know whether or not this stuff really works:

http://www.broquet.co.uk/

So please don't shoot me if it doesn't, I just read your post and it reminded me of the stuff in the link.

It might work, it might be BS, I don't know.

Janis
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  #9  
Old 13-02-2006, 11:41 AM
JohnA JohnA is offline
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The site is very thin on details or independent tests. Just vague promises of 50% reduction in emissions :lol:

To me it sounds very similar to the tin pellets aka 'Fuel Cat'
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