unleaded with volumex

[scorp77]

Is it true that the vx engine runs only leaded fuel? Is it possible to convert to run unleaded?

[cstorry]

I'm running mine on unleaded. I use the highest octane I can find here in Canada.

Chuck

1985 Pininfarina Spidereuropa Volumex (#390)

[Hamish]

I run my VX coupe on the highest octane unleaded I can (with additives :twisted: ) to make up for the lack of leaded petrol :x .
I'm reliably told that there's no problem running the cars on either leaded or unleaded but certain unleaded fuels can cause pinking and require adjustment to the engine timing to compensate.
There is a debate over wear to the valve seats when running unleaded, but I had the head off my VX engine earlier in the year after it had done 20k miles in my ownership :wink: running unleaded and there was no evidence of recession of the valves. I think you'll be fine on unleaded, but it might be an idea to run an additive :P to be safe.......

[Will]

Croft says leaded fuel only for the Vx head!
What exactly this is based on, I'm not sure.
I believe that valve seats can be replaced to convert a motor from leaded to unleaded fuel.
My scorpion was built six years earlier, and said "unleaded only" in several places.
I'd be interested in hearing more on this issue.
-Will

[Hamish]

I believe that valve seats can be replaced to convert a motor from leaded to unleaded fuel.

When I had a '78 Beta Spyder (Zagato across the pond :wink:) it was 'finished' just as leaded fuel was discontinued in the UK :roll: It ran fine on unleaded until I lunched the bottom end going round a long corner a tad too quickly and starved the bottom end of oil :oops:
I had the engine rebuilt and sent the head down to Bazza at Evocars (it was Barry Waterhouse Engineering then) for an unleaded conversion. They did a great job on the head but I sold the car on with another engine in it and never used the head which I sold seperately at a huge loss over the cost of getting the work done. :x
The upshot of this is that yes, you can indeed have the cylinder head adapted with inserts to allow you to run unleaded but unless you've got the engine apart anyway what's the point when you can run the car quite happily on unleaded with additives :?:
It's a major expense getting the cylinder head 'done', that's fine if you can afford to do it or feel it's really worthwhile but an exercise that might not be 100% necessary particularly in an engine which isn't spending all day at 6000rpm :wink:

[Bazza]

Croft says leaded fuel only for the Vx head!
What exactly this is based on, I'm not sure.
I believe that valve seats can be replaced to convert a motor from leaded to unleaded fuel.
My scorpion was built six years earlier, and said "unleaded only" in several places.
I'd be interested in hearing more on this issue.
-Will

Guy Croft does seem to have some funny ideas - VX cylinder heads on the exhaust side have sodium filled valves, bronze guides and diamond hard seats - you could make the head more suitable for running unleaded fuel.

[Will]

What then should be done to convert the head to unleaded?
Shipping this head across the pond is a non-option, so I need to know what should be replaced. Valves? seats? guides? All of the above?
What spec should I be replacing these parts WITH??
-Will

[cstorry]

I assume that Bazza was speaking rhetorically ?

How much harder can you make the valve train in order to replace the "lead" lubrication factor ?

[Will]

That's what I want to know, Chuck!
-Will
PS> David doesn't like sodium valves, he claims the ends fall off. He's going with SS I believe.

[Bazza]

What then should be done to convert the head to unleaded?
Shipping this head across the pond is a non-option, so I need to know what should be replaced. Valves? seats? guides? All of the above?
What spec should I be replacing these parts WITH??
-Will

It's true that the heads fall off sodium filled valves that are 20 years old or more but you can still get new sodiem filled valves (from the later turbo engines) with exactly the same dimensions as the original VX valves - part number 7631719 - they are not cheap at £34.90 each but they are the dogs danglies and they'll be good for another 20 years. I can't see solid stainless ones lasting that long.

You will not need to replace any other parts unless they are worn.

[John Allen]

I believe one of the reasons the VX *should* use leaded gas is that leaded gas has a higher knock rating than comparable unleaded.

John Allen

[Bazza]

I believe one of the reasons the VX *should* use leaded gas is that leaded gas has a higher knock rating than comparable unleaded.

John Allen

If you are lucky enough to find unleaded in the UK it is 97 octane. Almost all petrol stations have 97/98 octane unleaded.

[cstorry]

Don't forget that we measure octane differently in North America (well at least we publish different numbers).

I believe that what you see at the pumps here is R+M/2 which is on average 2 or 3 points less than what's listed on the pumps in Europe

Chuck

I always use the highest octane I can get to avoid pinging (pinking) which is usually 93 or 95 depending upon the garage

[Wallace]

John Allen[/quote]

If you are lucky enough to find unleaded in the UK it is 97 octane. Almost all petrol stations have 97/98 octane unleaded.[/quote]

.. if you're bloody rich enough, more like :wink:

[Will]

Wallace...
I think you missed Chuck's point, which is that our octane ratings on this side of the pond are the average of the RON (Research Octane Number) and the MOTOR octane number (the one you use).
This makes for a significant discrepancy, as in some cases the two can vary by as much as 10 octane points.
Furthermore, we have a lot of performance fuels available (I think VP has at least ten different formulations available) but they don't store well, and so nobody locally likes to order them in - especially in the off-season. So we really need to build our motors as being capable of running on 95 octane. Since we're talking about forced induction here, detonation can also be controlled by a throttle stop on supercharged motors or dropping the blowoff valve pressure on turboed beasts.
-Will

[Will]

Oh, sorry- didn't see it was a QUOTE!!!!
Sorry, Wallace!

[Wallace]

My fault ! I'm not clever enough to put bits into "quote" boxes - unlike everyone else on the group .. . dohhhh !!!