UNLEADED PETROL-SIMPLE QUESTION

[phatmendus]

hello,

to anyone who knows for sure can you please answer this question for me. I please only want a simple answer, not the history of tetraethyle lead, octane numbers and such else.....my question is this:

Is it ok to run my elan plus two (standard) on long journeys, with high octane unleaded without ruining the valve seats? (I am not sure if the inserts used were made durable enough for running on unleaded)

At present I am using either optimax or the 99 octane unleaded from Tesco. I am not adding any other additives.

Thanks very much

Simon

[nebogipfel]

Simon, this has been discussed so many times and I am confident you are not going to get a quick definitive answer.

I think the best people to ask are the guys' n' gals from across the pond who have been running on unleaded for a long time now ........ and I'm sure they will tell you

Lots of anecdotal evidence seems to suggest that Elan valve seats are OK with unleaded and I know of one chap who specifically looked for seat recession and found none.

I use normal unleaded and Valvemaster ..... just in case

[ppnelan]

Simon,

The std valve seats are NOT 'suitable' for unleaded, unlike the later 907 (Elite & Eclat) engine.

HOWEVER, I have a +2 with std seats which does a few thousand miles a year on mainly long journeys, and I use Super Unleaded without additives. The previous owner said he used 'normal' unleaded !
I do not 'thrash' the car, but use it as more of a 'cruiser', so I do not expect the valve seats to wear out 'overnight'.

My opinion is that you may as well keep using it until it starts to show a problem. Check the valve clearances every few thousand miles, and you will see whether the seats are wearing. Unless you use maximum acceleration all the time, valve seat recession will not happen suddenly and will only gradually develop. A compression test at a similar interval should indicate if the seat faces are getting pitted, which is the main problem I've come across, even with hardened seats.

To summarise (sorry!), if you have standard seats, I would wait until they NEED changing before getting hardened ones fitted.

I wonder if others agree...?

Matthew

[steveww]

If you do want to have harder seats fitted it does not cost an arm and a leg. I had all new valve guides (The reason for pulling the head) and new super hard exhaust seats fitted by my local cylinder head specialist for about ?200. A good winter project to keep you busy while not driving the Elan

[M100]

I've found the engine runs just fine with super unleaded - usually bought from BP as I don't trust anything that Shell has touched! I've got bronze valve guides, standard valves, standard seats (fitted a few years before unleaded was introduced to the UK), and they haven't measurably recessed in 10 years of (summer only) running, nor do they appear to be pitted as the cylinder leakdown is still around 5%. Call it a good 30-40,000 miles without problems.

[phatmendus]

WOW!

could the answers have been more varied! Thanks very much for the info. I recon I will continue to use the 99 octane, and maybe every other tank stick some reddex or similar in for good measure.

In terms of different petrol, I thought I would give me small bit of advise...

Working on the UK's oil refinarys I thought I would investigate all the hear say regarding different petrol qualities from various companies. I read a blog on the pistonheads website which summed up the complete mythology surrounding fuels, for example, someone wrote that supermarket petrol is bad quality and the s**t from the bottom of the tank, and that is why it is cheaper! anyway, I have asked this question to several people on different refinarys and their answer was this: Basically whoever you buy your petrol from it is the same stuff, refined by the same places. The only difference is that each company litteraly sticks its own cocktail of chemicals in with the petrol to give its makers mark, i.e optimax or super or whatever. So anyway, sorry to waffle but as far as I have been told the petrol you buy anywhere is basically the same apart from the additives, i.e cleaning agents and octane booster.

That is my useless fact for the day, although I may be wrong! let the debate begin!

Thanks for the advise on unleaded.

Simon

[chrishewett]

I have just read an article in january Sprint magazine (TVR Car club), which basically says the same thing about all fuels being basically the same except for additives. I had my head rebuilt by PNM about five years ago at a cost of about ?500 and I can't remember if he put hardened seats in! Here in lincolnshire you just have to put in whatever you can, although I try to use optimax when possible.
Chris

[twincamman]

I run both my twin cams on regular 87 octane unleaded from any gas pump available at the time of need --with no problems -- ed

[archigator]

Dave Bean's Elan catalog (my copy circa 1987), page E5 states,

"... Guess what Lotus fans, we don't have to worry. At least not right away. Lotus T/C engines use excellent stainless steel valve material, the same as many F1 race engines. The seats, while not realy very hard, are... by virtue of living in an aluminum head... high in nickel content to achieve a coefficient of thermal expansion compatable with the aluminum head. This helps durability and negates the need for an external lubricant (lead). While they have never been very hard (you could never rationally get more than two valve jobs out of a seat), the change in fuel (to unleaded) has little real effect on actual seat life."

" Obviously if you need a valve job (and you will most likely need seats too... most people try to go too long), change to hard nickel/chrome/moly seats. It will certainly extend seat life."

I defer to Mr. Bean...

Gary
'71 Elan Sprint
Miami, Florida

[phatmendus]

ED, please tell me you meant 97 octane rather than 87!!! Unless you are buying your fuel from Mauritania or similar! I dont think even the hardest of seats, or for that matter the thickest of cylinder walls would put up with an 87 octane fuel for long. I used a low 80's octane petrol in west africa and the engine knocked like crazy! Also the petrol had the look and consistency of syrup!

Anyway, thanks for the info everyboy I shall do my 100 mile journey each day with confidence that at least the valves will seal ok!

Simon

[twincamman]

nope -- 87 ---thats regular fuel here -just up from tractor gas --runs fine ------you sure you weren't at the diesel pump ?--- ed

[marcfuller]

Depends on what octane rating system is used. I think commonly used octane values in the UK and North America are different Fuel station pumps in North America display an octane value that is the mean of the research octane number (RON) and the motor octane number (MON), or (R+M)/2 . IIRC, the RON value is used in the UK for automotive and is often as much as 8-10 points higher than MON.

In Colorado, because of our elevation, "regular" grade gas/petrol has only an 84 octane (R+M)/2 rating.

[handi_andi]

Just thought I would drop a note in here as I have been wondering about the regular unleaded or super unleaded with or without ever since i brought my lotus last week. The first few tanks of fuel I put in I used super unleaded plus redex addicitive and the engine pinked and knocked lie crazy. However, when I put regular unleaded in the engine knocked less and pinked less. I know my engine is out of tune bt did find this phenomenom rather interesting. Since then I have switch to my old favourite valve master but with octane booster and the pinking has returned. Is this likely to mean the engine has been re-timed for regular unleaded?

[twincamman]

I really dont like to get to my destination ---thats why I drive a lOTUS ------ ed