Gasoline Additives

[TX-302]

Are any of you DZ owners running fuel additives for todays unleaded gasoline...or is that a only concern that has a long term effect on the valve train? If so, what brand do you recommend?

[sam]

I used to run a lead additive with 93 octane but now I just go and buy Sunoco 112. Don't like the ethenol in the gas today. The 112 makes the plugs more readable and the car seems to start and run a little better with the 112. Expensive but I don'r drive the car real far but drive it weekly, maybe even twice a week in nice weather.

[JohnZ]

Are any of you DZ owners running fuel additives for todays unleaded gasoline...or is that a only concern that has a long term effect on the valve train? If so, what brand do you recommend?

Valve seat recession is a myth, unless your engine is in a boat, a loaded dump truck, or you're pulling a trailer at 100 mph. Millions of engnes have run on unleaded gas for 35 years without issues. The effect of any additives in a bottle are purely psychological, not mechanical.

[Dusk_Blue_Z]

Not trying to argumentative, but you're saying hardening seats to run oxygenated fuel isn't necessary?

[JohnZ]

Not trying to argumentative, but you're saying hardening seats to run oxygenated fuel isn't necessary?

That's correct - there's no need for hardened seats in our vintage engines; they'll never see the kind of continuous high power setting duty cycles I noted above, and it doesn't take much of a machining error when cutting the seat openings to ruin a perfectly good set of 2.02/1.60 heads.

[Dusk_Blue_Z]

Like so many things, its become convetional wisdom to harden seats in classic engines. Any thoughts as to why?

[JohnZ]

Like so many things, its become convetional wisdom to harden seats in classic engines. Any thoughts as to why?

I wouldn't call it "conventional wisdom" at all - I'd call it machine shops telling customers that terrible things will happen to their cylinder heads unless they have hardened seats installed, which isn't true at all. If it makes you feel better, go ahead and let them do it, but there's no need to do so. I've been building vintage small-block Chevys for 40+ years, and have never seen a single instance of valve seat recession in street use.

[jdv69z]

My 69 Z 302 has never had any problems; I've had it since 1982, had it rebuilt in 1993, and the mechanic at that time said I didn't need the seats. Glad I didn't do it.

Jimmy V.

[tom]

There were a lot of predictions there would be problems back in the early 70's when unleaded gas was introduced that it would destroy the heads on all our older cars. I never saw the predicted damage materialize. Kind of like predictions that airplanes were going to fall out of the sky, and banks were going to lose all your money at the stroke of midnight December 31 1999 (Y2K).

[Dusk_Blue_Z]

JohnZ, in MN we have both fuel oxygenated with ethanol (up to E15 I believe) and fuel without ethanol (non-oxygenated). Does it make a difference which fuel to run?

We can get 93 premium that contains ethanol or 91 of the non-oxy fuel. Since break in, I've only used the non-oxy. Just curious which I should be using.

Thanks.

[JohnZ]

JohnZ, in MN we have both fuel oxygenated with ethanol (up to E15 I believe) and fuel without ethanol (non-oxygenated). Does it make a difference which fuel to run?

We can get 93 premium that contains ethanol or 91 of the non-oxy fuel. Since break in, I've only used the non-oxy. Just curious which I should be using.

Thanks.

We've had E10 fuel in Michigan for at least 25 years, and I've never had any issues with it; from a performance standpoint, what matters is the pump octane rating, not whether or not the fuel contains ethanol. A higher octane rating means it's more resistant to detonation (pinging), so you can run more ignition advance.

Your ethanol fuel is E10; E15 won't be seen for a long time - it's tied up in the courts.

[KurtS]

As an asided, the only thing downside with E10 is it can attack some metal cans.
We had a farm and brought back gas for the tractors. Soon after E10 was introduced, some of the 5 gal metal cans started leaking. Cans that had been fine for the prior 20 years......

Never heard of having a problem in vehicles where there are coatings on the metals.

[69Z28freak]

Very interesting. Does that apply to all? Does it make a difference with a 12 to comp motor? I have been told constantly that a motor can't run more than 10 to 1 with Pump gas. We can get 94 octane in Canada. I am thinking of building a motor and want to know what would be the correct comp ratio to use. Obviously higher comp will make more power.

[JohnZ]

Very interesting. Does that apply to all? Does it make a difference with a 12 to comp motor? I have been told constantly that a motor can't run more than 10 to 1 with Pump gas. We can get 94 octane in Canada. I am thinking of building a motor and want to know what would be the correct comp ratio to use. Obviously higher comp will make more power.

Depends on the engine and the tune - there are LOTS of 11:1 60's small-block Corvettes and Z/28's out there with factory "30-30" cams that run just fine on pump premium; the "30-30" has a late-closing intake valve that bleeds off some cylinder pressure at low to medium rpm that makes it much less sensitive to detonation. Aftermarket cams all close the intake valve much earlier in the quest for more power, and most of them won't work without detonation at 11:1 as a result.

[Kelley W King]

I too have run pump gas in my 11 to 1 without harden seats for years with no problems. But it sure is fun to through in about 5 gallons of race fuel.