Unleaded juice in a twink

[Stevie-Heathie]

Easy question for you guys, this. I would be very surprised if it
hasn't been discussed before, but it must have been before I joined the
list (August 1998). Apologies therefore for repetition:

My plus 2's twincam has a 1993 rebuilt QED big valve head, with colsibro
bronze valve guides. What else do I need to do to the head, and what
adjustments to the timing to I need to make to switch to unleaded?

I am aware that I should use "Premium" 98 octane unleaded, rather than
the standard stuff.

Alternatively, should I trust one of the emerging lead substitutes,
despite the fact that the BSi still haven't developed a British Standard
for these products?

5 months, 2 days to go!!!

Cheers

Stephen
1970 Plus 2S



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[BrianMartley]

Stephen,

I'm in the same position, I think you/we will have to replace the valve
seats, the ones in mine aren't hard enough - just standard replacements.
Bronze guides should be ok. Sounds cynical, but I'm not going to pull the
engine apart until it shows signs of distress, I don't do any real mileage
and most times I'm not blasting along.

I was going to use a lead substitute/octane booster if the proposed LRP
isn't up to it. I hear about this LRP, but haven't seen any in a petrol
station around here (West Yorks) Anyone know what the octane rating will be
?

To all you guys in the US, etc, what do you do ? New valves/seats at
overhaul time ?

Brian

[rodbean]

Brian Martley wrote:


Brian,

I live in California and have had numerous twink-engined cars, mostly Elans
and Lotus-Cortinas, currently with one running Elan.

We've had leaded fuel for a number of years now and I use lead substitute (STP
brand) now and then. The head is off now (water pump rebuild) and I see no
problems with the seats or valves. The car is a S1 but it has a complete
Sprint bottom end under the Weber head.

My gut feel is that lead substitute will be good enough until, as you
suggest, valve grind time when seats, guides and valves can be upgraded. No
problem with the last Lotus-Cortina I ran for regular use either.

I've had race cars also but the race fuel has lead and I used lead aviation
fuel anyway.

Rod Bean

[BrianMartley]

Rod,

Thanks for the info. Currently there's a lot of hype and debate over here
about additives, putting metal (tin ?) capsules in the tank/line, what does
work, etc, etc, so it's good to hear that the STP one looks to work.

To be honest, I'm more bothered about the octane rating, everything over
here seems to run on 2* - 95 I think - which I'm sure would upset the car
despite it's design.

Brian

[rodbean]

Brian Martley wrote:


I haven't had to add octane booster (do you have it?) on a stock, 9-to-1
compression ratio twink but it couldn't hurt, if you sense any detonation.
You can also retard the timing a bit if there is a problem. Or you can buy
some 100 octane race fuel and mix a little in every tankful.

Rod