bennymac

I just read some where that "C" head were used with leaded gas only? I have "C" heads, is there an issue if I'm running regular unleaded pump gas? Also with the gas prices the way there are am I going to see or feel the difference between 93 and 87 octane, cause I'd rather not spend the extra money if there is no real benefit?

frdmftr

I have a 67' Delta 88 convertible, 425ci with 'c' heads (10.5 to 1 comp). I run the hi-octane along with a lead additive. My latest mpg is 9.5 (all around mpg) and I don't get any 'octane ping'. I'm no rocket scientist (or engineer) but something is better than nothing.

My take on the gas prices? I like the ride, so I pay the price (currently $3.20 gl here in Spokane).

Just a few thoughts.

FRDMFTR

Redog

I'm soon to be running a 68 Delmont motor in My 85 Delta with 5 heads. This also requires lead.

Go to the local auto parts store and buy a bottle of additive, but you gotta use it every tank

Oldsguy

When I rebuilt the C heads on my 455 I added added hardened valve seat inserts on the exhaust valve locations before grinding them down to match the new valves because of what you are asking about. I am told it is true that since these heads were manufactured before the common use of unleaded fuel the best bet is to do that to prolong valve seat life. I understand that the heads built after unleaded fuel was commonly used have hardened areas around the exhaust valve seats. So, if you have original C heads or any other of the older ones for that matter, then it is safest to use a lead lubricant additive or suppliment. Although, I have also read that the newer fuels have lots of additives in them now for that purpose. I think I would rather be safe than sorry though.

Eightupman

I have read on other forums that the Olds valve seats are still harder than the Chevy or Ford motors of the same era and do not have the same types of problems with lead free gas and softer seats. I have heard daily driving C heads (or 5 heads) on pump gas is A-OK...

Something to look further into I guess.

John

bennymac

Thanks for the input guys.. I've went with the safe road and put some 93 with lead additive. It hasn't seem to make any change, but better to be safe than sorry..

frdmftr

I agree with all. Everything being correct (timing, block temps, fuel mixture), pump gas (87 octane) should be adequate for daily cruising/driving. Now for a demo 'burnout' in front of a couple thousand spectators, pinging would be a crowd killer (and embarrassing), not that I would ever do that, now and then

88 coupe

Depends how it is used. Is it a stock engine?

Are you an "aggressive" or "conservative" driver?

That same philosophy has served me well.

Should be a given in any case, but still well worth mentioning.

And a different issue.

Norm

shaks 442 clone

what do you mean by pinging?

could pinging be confused for like a tickiing sound?

Kahuna

The compression ratio of your engine determines the octane rating of the gasoline you must use in the car. The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. Think of Octane as an ignition inhibitor -- the higher the Octane rating, the less likelihood that the air/fuel mixture will spontaneously ignite. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can potentially damage an engine. Lower-octane gas (87-octane gasoline) can handle the least amount of compression before igniting. If you have an engine with a compression ratio of 10:1 or greater, 91-octane gasoline or higher is recommended. If you have a low-compression engine (8:1 ratio), high octane fuel would be a waste of money.

I use 89-octane in my '62 Olds but that's because I have the lower-compression (8.75:1) 394-2 bbl. This engine was a no-cost option that allowed the use of regular gas. I also use a lead substitute additive.

Oldsguy

Pinging also comes from improper timing, but as 88 coupe said, that is a different issue.

frdmftr

In my 'garage' laboratory, I fell victom to the ever increasing costs of fuel in Washington state (reg-$3.25 gl, premium- $3.49 gl). I filled up the Olds with regular, just to try it out. I have the 425 'c' heads and hi-comp motor.

You know the rest of the story. When I finally get below half a tank and after a couple of bottles of octane booster, I will re-fill with the correct (higher) octane fuel.

So much for trying to save $5 on a fill up.

Oldsguy

Speaking of "garage labs" I read a post over at R.O.P. about blending their own high octane race gas using Xylenes and other dangerous chemicals. Talk about a scary read! These guys were literally playing with fire, not to mention their own respitory health. I wouldn't consider that in a million years. This isn't to imply a comparison to what you did, that phrase just made that memory pop into my head.

frdmftr

Never took it as an 'implication'. This thread reminded me the same way, that is why I made the reference. Quite a few years ago we actually 'blended' our own fuels too. I primarily used tolulene, which at the time was the primary ingredient in techrolene. Ran the blend in everything from trucks, sleds, bikes, rototillers. Anything that 'exploded' fuels got the blend as subjects for our 'mad scientist' brains.

Thank god I survived and matured (I'll never grow up).

Bottom line- my Ultra-High Compression 'banger' does not live well below 92 octane and I'm sure does well with a 'lead' enima every tank as well.

Oh ya. I caught a cool segment of 'Rides' on the tube last night. It featured Leno's 'barn find' of a rare Duesenburgh. The cool part was his talks about the history of steam engines in autos and how (in the 20's) they were perceived as far superior to the 'exploding' gas engines.

My how far have we come........

FRDMFTR

Oldsguy

Yeah, I hear you. I would love to see some of his stuff in real life. What an opportunity he has and he doesn't seem to squander it either. People that have met him say he is a real nice guy too.

Redog

What is the correct CR of the 1968 Rocket 350 then. I've heard 10.1-1 and 9.0-1.

Seems like the difference of using 87 and 91 octane with the lead addtive. I have a full tank of 89 in the car right now (since Feburary) but I put in Stab-le