Lotus Elan

S1 with Dellorto's??

PostPost by: nomad » Tue Oct 23, 2012 6:23 pm

Once I get to working on this engine I will know but for now my curiosity is getting to me.
My S1 is fitted with a 4 bolt crank engine and a head with dellorto's. According to Ross and Robinshaw these carbs were on the Sprint big valve head and the way to identify that head is by a letter z or n on a boss in front of No.1 cylinder. Would this letter be covered by the valve cover? The head does have the reenforcing webb between No. 3 and 2.
I'm assuming for now that the PO fitted a big valve head and if he did can one live with 10.3 to 1 comp and 91 or sometimes only 89 octane gasoline??

Thanks,
Kurt.
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PostPost by: twincamman » Tue Oct 23, 2012 6:43 pm

Both mine live happily on it ===ed
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PostPost by: hartley hare » Tue Oct 23, 2012 7:04 pm

hi nomad

the letter z or n (denoting big valve) is not covered by the cam cover,but is in the spark plug well next to no1 plug,
it is on a raised round casting about the size of a 10p coin.....

i think that some heads are left blank, dont know why.....

hope this helps.....
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PostPost by: types26/36 » Tue Oct 23, 2012 7:07 pm

nomad wrote:Would this letter be covered by the valve cover? The head does have the reenforcing webb between No. 3 and 2. Kurt.


No the letter is not covered, here are mk1 & 2 heads.
Mk1 9.5:1?
mk2 9.5:1
sprint 10.3:1
Attachments
sprint.JPG and
mk 2 head.JPG and
mk1 head.JPG and
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PostPost by: garyeanderson » Tue Oct 23, 2012 7:17 pm

Nomad
Got photos? Brians pictures should help. There are numbers on the head that should match the engine number (if original), these are stamped into the back of the cylinder-head near the deck face, take a look at this topic for what and where top look. Mirrors and cameras help

elan-f15/cylinder-head-stamped-with-lotus-production-numbers-t15867.html

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PostPost by: nomad » Wed Oct 24, 2012 12:39 am

Thanks to Brian's excellent pics I'm now quite sure I have the Mk1 head.(Darn...no big valve!) Thanks to all for the input and I will check out the serial no's when I get a chance.
Haven't a clue why its got Dellorto's and suppose I will have to do some measuring to see just what I have for carbs. Many more questions will be following when I get into the engine I'm sure.

Thanks,
Kurt.
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PostPost by: nomad » Fri Oct 26, 2012 12:20 am

Found the number on the head. It is LP 1832. This is on car 26/3754. I can't seem to find the block number and trying to determine where its at thru the archives gives me eye strain! No engine number on the serial tag.
Again, for curiosity, can anyone tell me if this seem's like the original engine and would this late of an S1 have the improved rod's??
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PostPost by: bill308 » Fri Oct 26, 2012 1:24 am

My S2 has the 116 rods, not the 125E rods. I'll fit 125E rods during the next rebuild.

Given that the carbs have apparently been retrofitted, there is a chance the PO may have also changed the rods. I don't see how 125E rods would have been available for an OEM S1.

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PostPost by: StressCraxx » Fri Oct 26, 2012 4:29 am

Nomad,

Neither the parts book nor Robinshaw & Ross advise the exact changeover from the 116E to 125E rods, only R&R saying it was during late S1 production. So, you might be lucky.

Its good you have what may be the original head. The difference between the standard and "Big Valve" heads are 0.1" intake valve diameter and a slight increase in compression. It was mostly Tony Rudd's first project at Lotus and Graham Arnold's marketing buzz to boost sales anyway. The additional compression from milling the head, the sprint cams, and bigger chokes in the Webers to make the difference in power. The upgrade can be done by a good machine shop/builder. I would only do that upgrade if you have the 125E rods and use the 12pt rod bolts.
There is no cure for Lotus, only treatment.
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PostPost by: trw99 » Fri Oct 26, 2012 6:07 am

nomad wrote:Found the number on the head. It is LP 1832. This is on car 26/3754. I can't seem to find the block number and trying to determine where its at thru the archives gives me eye strain! No engine number on the serial tag.
Again, for curiosity, can anyone tell me if this seem's like the original engine and would this late of an S1 have the improved rod's??


Nomad

Your car was indeed originally fitted with engine no. LP1832 and was invoiced by the factory on 30 July 1964.

Dellorto DHLA 40?s began to be fitted to Elan Sprints in about May 1972. A service bulletin detailing the changed specifications was issued on 9 June 1972 so Dellortos must have been fitted to Sprints in the factory by May 1972. Dellortos were fitted by Lotus to the Twin Cam Europa from December 1971, so clearly Dellorto was a factory supplier by then. One reason for this change was that Dellorto had been quicker and more willing to change their designs to meet the new European regulations that were due to come in force. They may also have been cheaper than Webers too.

Tim
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PostPost by: nomad » Fri Oct 26, 2012 8:07 am

Thanks much for the info, folks. I may get into the engine this winter if I can get some other projects out of the way.

Kurt.
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PostPost by: nomad » Fri Oct 26, 2012 2:14 pm

One more question, if I may!
Will the 4 bolt crank stand up to more power? I assume that the move to a 6 bolt crank was done for strength reasons but perhaps that is wrong. I know the seals were also changed.
Its hard to have enough power isn't it? :lol:

Kurt.
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PostPost by: types26/36 » Fri Oct 26, 2012 5:17 pm

StressCraxx wrote: The difference between the standard and "Big Valve" heads are 0.1" intake valve diameter and a slight increase in compression..


I think that should be 1.0 mm (0.040") diameter larger inlet valve and the same amount (0.040") skimmed off the head to give a 10.3 CR.
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PostPost by: Esprit2 » Fri Oct 26, 2012 5:29 pm

nomad wrote:(Snip)... can one live with 10.3 to 1 comp and 91 or sometimes only 89 octane gasoline??
There are two common methods for measuring the octane rating of petrol/gasoline... Research Octane Number (RON), and Motor Octane Number (MON). It's like the difference between measuring the same part with a meter stick, or a yard stick... you'll get different numbers for the exact same thing. In this case, RON produces octane numbers that are about 8 to 10 points higher than the MON method produces for the same sample.

To complicate things, some countries (including the USA) use an average of the two, (R+M)/2, for the octane value posted on the pumps. Those results are typically 4 to 5 points lower than straight RON values.

In the UK, octane is rated by the RON method, so a 92 octane there is about equivalent to 87-89 octane in the USA. I'm in the USA, and the octane of the fuel I buy is 92 (R+M)/2, or 96-97 RON.

All of which is a long way around saying your question, and the relevance of any answers, depends upon the frame of reference being used. Just throwing out numbers doesn't necessarily translate well. Lotus being a Britcar, the manual recommends a minimum fuel octane expressed as a RON number.

For 10.3:1, I'd be using premium (high octane) fuel exclusively.

Regards,
Tim Engel
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PostPost by: Vincent Haydon » Sun Jan 05, 2020 12:53 pm

Hi Kurt
Hopefully we are now in touch. My email address is [email protected] and my contact numbers: 10590 682508 / 07860 391320. I will endeavour, I think in future to post more items and maybe have an advert on Elan.net as I have many parts suitable for the cars. Speak soon. Vincent
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