Gas for your Z?

[Corganx33]

yes, I did a search for "leaded gas"

The majority of the discussions seemed to be held by our aussie brethren, many used something called optimax, most seemed to use 98 octane gas straight up, claiming they didn't need the substitutes.

So what do people stateside use? What Octane? Do you add in the substitute lead or no? I thought the lead in the gas acted like a lubricant for the engine. If you ran unleaded gas in a engine not designed for it it would run to hot and break down?

I just got my new "toy" , a '73 240z, and am trying to figure out what I need to do to take care of it.

[Zrush]

I run Premium Unleaded in both Z's, the 72 240Z and the 77 280Z. They run fine. Octane is 93 to 95 here in my area.

Vicky

[ChrisA]

The old rule on unleaded gas was it didnt have any protection for the valve guides and valve seats. You would get excessive seat pounding. This was on the 240/260Z heads. The 280Z heads had hardened seats to accept unleaded. Those that have had a valve job with new seats installed are ok to use unleaded. I have an original E31 head and I havent noticed any problems with unleaded gas (91-93 octane here). Valve timing is always good and motor has great compression. I used to run octane booster but that seemed to decrease my gas mileage so I stopped using it and just look for the highest octane I can find.

FWIW

Chris

[2-4-T-Z-MAN]

I run 93 to 95 octane in my 72.

Chris is correct about the purpose of the lead.

With the hardened valve seats, unleaded is no problem.

I have heard that unleaded has an additive to protect engine parts as the lead did.

There where a lot of cars on the road that where not designed for unleaded when it first appeared.

Could be an urban legend!

[Corganx33]

I'm pretty sure my 73 has stock internals... so I'd have to rebuild the engine with the hardenned seats to run unleaded safely?

Otherwise use the subsititute?

[sblake01]

I always thought that you run the lowest octane that your car will run on without pinging and anything else you're just spending extra money. As far as the leaded/unleaded thing goes gas has an additive to serve the function that lead once served at least that is what I have read on the labels on the gas pumps.

[beandip]

sblake , you are right . If the compression is low enough you can run the lower octane fuel. the '73 is the first emissioned engine and the compression is lower than that of the three privious years. The higher octane fuel on a low compression engine is waisting $. If it doesn't ping under load it is ok. Corgan33 if you are going to have a valve job done , have the hardened seats put in . In anny case. You might concider milling the head and uping the compression. The real guru is this area is phred give him a pm or email . He does this stuff for a living and builds race engines for Z cars. My L-24 out of my '73 was running at 145psi compression to 150 accross all 6 . Not that high but a stock 88 head . How does this compair to your engine. I was getting 23MPG on the road .

[deadflo]

I have read in some automotive literature that if you originally ran leaded gas in an engine with non-hardened valve seats, that that was enough to permanently lubricate the seats and you could run unleaded after that . Not sure how long you had to run the leaded gas, but I know for certain that the unleaded gas didnt arrive until 1971 (having worked in chevron station that year at the age of 15). Very few cars could use the unleaded when it hit the market.

Obviously if you have a pinging problem, you need to switch to higher octane.

[gramercyjam]

I run pump regular unleaded in my L24 autox car with late E88 head, standard 18 deg BTDC timing with no pinging. That motor is about 8.5:1. My flattop L28 with .020" shaved E31 with turbo valves and seats will be fed leaded C12 VP (MON 108) race gas. That motor combo is good for about 11.5:1. As well as having a high octance rating, the lower specific gravity of that fuel should be a good match for my antique Weber 45's that currently run slightly rich on pump gas.

[kmack]

If you have the Bronze valve seats, then you either need to run a lead substitute or have the vlave seats swapped out for hardened ones. To my knowledge, only the very early cars (69-70) and the early 280's (75-76, N42 head) had the bronze valve seats, everything else has the steel valve seats.

http://geocities.com/zgarage2001/heads.html

[Bambikiller240]

My 1972 240Z (mfg 11/71) was delivered with an early E88 head which had bronze valve seats.

[kmack]

The original engine for my late '71 with E31 head had steel seats in it when I rebuilt it. PO pulled the motor out at 50k and replaced with L28 back in the day. The orig. motor was never touched.

I guess it can all be hit-n-miss then. Best to find out what you have is to pull it and check it then.