Leaded or unleaded - That's the question, Need advice on which type of fuel to use.. Options

[reineg]

Hi there, Laymen and Experts alike!

I have recently acquired a 914/4-70 with a newly built engine. Up to 2.2litre and some extra horses to boot. But now to the question:
The car has got new cylinders and pistons from Pelican Parts, but I do not know much more about the engine. So do you guys (and gals) reckon it would be safer to use modern fuel and add lead, or shall I just go for modern fuel and not add lead?

What is most detrimental to the engine; to add lead to an engine that doesn't need it, or not to add lead to an engine that requires it?

Appreciate any and all thoughts on this..

[GregAmy]

I can't imagine any heads rebuilt in the last 30 years needing lead (to protect the valve seats).

And I can't imagine any engine built for the street needing lead (for octane) especially when you can get 110 unleaded racing fuel (if needed). Honestly, street engines should be built to safely handle 93 octane max (91 if that's what's typically in your region).

Lead isn't pleasant stuff but it should not hurt your engine, even if it doesn't need it. But leaded fuel can have its own problems such as precipitating out if it evaporates from non-use. The photo below is the main jet stack from the Dells in my race car, photo taken earlier this month. For whatever reason (I think it was cheaper) I bought 112 Leaded at an event in June instead of 100 Unleaded, and then parked the car after the weekend. When I pulled it out the week before Memorial Day to get it ready for an event that weekend, it was running like hell...and this was why.

Ask your engine builder for minimum fuel specs, but I just don't see any rational reason to need leaded fuel these days. - GA

[930cabman]

I can't imagine any heads rebuilt in the last 30 years needing lead (to protect the valve seats).

And I can't imagine any engine built for the street needing lead (for octane) especially when you can get 110 unleaded racing fuel (if needed). Honestly, street engines should be built to safely handle 93 octane max (91 if that's what's typically in your region).

Lead isn't pleasant stuff but it should not hurt your engine, even if it doesn't need it. But leaded fuel can have its own problems such as precipitating out if it evaporates from non-use. The photo below is the main jet stack from the Dells in my race car, photo taken earlier this month. For whatever reason (I think it was cheaper) I bought 112 Leaded at an event in June instead of 100 Unleaded, and then parked the car after the weekend. When I pulled it out the week before Memorial Day to get it ready for an event that weekend, it was running like hell...and this was why.

Ask your engine builder for minimum fuel specs, but I just don't see any rational reason to need leaded fuel these days. - GA

Ouch, what happened to this main jet/holder? Probably water (IMG:style_emoticons/default/screwy.gif)

[GregAmy]

Ouch, what happened to this main jet/holder? Probably water (IMG:style_emoticons/default/screwy.gif)

It cleaned right out; the holder, jets, and air correctors are fine.

The engine ran fine when I parked it in June. And though it lives in the garage since - no significant exposure to water except maybe sitting outside with Perry's umbrella cover* if it's raining and I need the lift - I had no reason to run it so it was just pushed in and out as needed.

Best I can figure, I didn't fully drain the float bowls when I shut it down** and the fuel in the float bowl evaporated, leaving behind these precipitates, same as salt water will leave behind salt if you evaporate it. When I turned on the fuel pump it filled the bowl, mixing those solids in there, and when I fired up the engine it got sucked into the jet ports and stacks. I removed the top of the carb and there was grey lead deposits in it, and after cleaning that out I blew through the passages and more came out into the main stack ports.

I purged the rest of the tank of all that fuel, and there were no contaminates in the system. The fuel filter was clean.

Avoid the lead if at all possible.

GA

*Perry's cover does a decent job of keeping water out of the grill, but it has to be stretched tight. I'm running Sergio's GT grill and there's no water tray. Also, the air filters are using Claude's aluminum cast tops so I really don't see that there was much way for water to get into the carbs. And there was no reasonable way for water to get into the fuel cell, which is mounted in the front trunk (I didn't see any water when I purged the tank).

**At the end of a weekend I will typically turn off the fuel pump and let it idle it until it dies, using throttle to keep it running as needed. The left side carb was fine, only the right one had these precipitates. So I'm guessing the left side ran out first and the right side was not cleared out when I let it die and shut it down.