what type of fuel?

[Gearhead]

Would like to know what other members are using in there cars racing lead additive just plain unleaded /ubbthreads/images/graemlins/driving.gif

 

[jcatnite]

Just mid-grade unleaded, but I know what I am doing to my valve seats and plan to replace them with hardened seats in the near future anyway.
JC

 

[dklawson]

My 1275 engine has the later 12G940 head with hardened exhaust seats. However, I still run regular gas and still add the lead substitute. I've been told by an engine builder in the U.K. that he has seen improved valve life (even when hardened seats are present) when owners continue to run lead substitute. Mine is a street engine so I can't comment on what more serious drivers use/do.

 

[aeronca65t]

For my brother's 1275 Midget, 89 octane mid-grade unleaded.

For my racer (10.25:1 comp ratio) I'm running 100 octane Sunoco unleaded (CAM-2).

Most of the lead-substitute additives available in stores have very little affect on octane unless you use massive amounts of them. I'm not sure how they affect valve life.

 

[Matthew E. Herd]

I use Sunoco Ultra 94 only for my (or anything 93 if I'm in a pinch) 10.5:1 CR 1500 engine, with cam, etc. The hotter the cam, theoretically the less octane you need at the same compression (due to increased overlap, there is effectively less cylinder pressure at low rpm/high load conditions -- where octane is generally needed most, reducing octane requirement of your fuel). That's oversimplifying the situation, but see David Vizard's book (Tuning the A Series Engine for Performance or Economy) if you're curious about such things, but it might just be easier to see what you're looking to do and we can point you in the right direction. I haven't had trouble with my setup, at least due to octane, although I do admit I have some carburator issues which I am currently working on resolving.

 

[JohnnyB1275]

I use 93 in my race car, I think it has the stock cam, an it seems to run pretty well. I just wish the everything on the car would work at the same time.

 

[77MidgetMkIV]

I use Mobil 93 in my Midget, and have since I got it. No issues thus far. Not too too worried since the engine is getting a rebuild, most likely after next driving season. Runs smooth, no pings, no smokes, no nothing.

 

[GreenHornet]

I have been using amoco ultimate. White gas. I have the no lead head conversion. with about 4 oz of marvel mystery oil per tankful, no problems.

 

[donandmax]

Does a 1975 1500 engine have hardened valve seats? In other words were the 1500's set up for unleaded. (ex-Ca. car)

 

[jcatnite]

No I don't think it would have hardened valves and seats in '75. I think the split between leaded and unleaded happened in '76.
JC