Engine advice

[jimj]

Throttle spring fell off at Estoril last October approaching hairpin. Dipped the clutch to avoid dieing before turning off ignition, revs. went right round the dial. Oh! Oh! Taking the head and sump off revealed no visual damage but the exhaust has been getting smokier. We went on the Celtic Malts (just got back in the hired Fiesta......oh! oh!) and over the first 2 days and about 500 miles the engine got smokier and smokier and smokier, other competitors were seeking compensation for Linctus. At the first test I dropped the clutch at about 4000 rpm and the engine died, coughed, spluttered, misfired, then blew the oil filter off, then really died and won`t turn over. So what is the consensus? Could it be that the over revving reduced the hardening on the piston rings causing rapid wear or ?????????????
No sympathy required just good advice, we`re booked on the 3 Castles on 4th June.
Jim

[neilsjuke]

Hi sounds not good ,sounds like it started of with broken ring/s .now piston poss bent rod not what you want to hear you will have to take it out and have a look.

[rgh0]

I agree it sounds like cracked piston that has now finally failed and maybe also had a cracked crank, rod or rod bolt that has also finally let go.

What crank, pistons , rods and rod bolts were you using?

When rebuilding add a good quality electronic rev limiter to your rebuild budget and also add independent throttle return springs on each carb shaft as insurance against next time.

At least if no holes in the block you can probably start your rebuild by reusing it.

cheers
Rohan

[jimj]

Rohan, the engine was rebored at some time but otherwise was standard Big Valve.
As a matter of expediency there is a rebuilt 1700cc engine for sale on ebay finishing today, a bank holiday. Will this fit under the bonnet? how can I be sure it`s a Weber head from the photograph?
Jim

[tower of strength]

http://cgi.ebay.co.uk/lotus-twin-cam-17 ... dZViewItem

if this is the engine you are refering to then it is a webber head, the stromberg head has only two intake runners for the carburetors, the webber/dellorto head has four. This engine is built on a crossflow block to achieve the capacity increase, and will be taller than the standard twincam, I believe the difference in hight is between a 1/4" and 3/8", not a problem on plus 2 and the europa but I'm not sure if there are any issues on the 2 seat elan,

Also as you compete with the car, will it still be compliant with a crossflow block?

hope this helps

Mark

[jimj]

Yes Mark, that`s the engine. I was sure it was a Weber head but just wanted to be sure. Unfortunately Newark engines aren`t working today. The sort of competition we do is very amateur and scrutineering is more about safety. The MGTD that won the Celtic, for example, seems quicker than an MGB, though the test points are versus the cars in it`s class, no-one seems to mind. My pal with the XK120 enters several classic rallies a year and his 285 bhp, disc brakes, zetrag `box etc. raise no eyebrows. I don`t think the cross-flow block number is ever likely to be read, any more than my Voight `box is objected to.
As my car is still in Belfast I can`t check the bonnet clearance but I`m pretty sure there`s enough.
Thanks,
Jim

[types26/36]

[quote="jimj" I don`t think the cross-flow block number is ever likely to be read,Jim[/quote]

The cross flow engine number is impossible to read with a T.C. head as its on the top face but it has probally been removed anyway as its normal to deck the block when useing the 1600 block (although it can be done without decking)
I think you are refering to the casting number (711) well just grind it off as Lotus did it to some blocks anyway.
The give away is is that it will have a spacer fitted on the top of the timing case,cant quite make it out from the pics but it looks like it has the spacer.

[rgh0]

Before buying a twink built on a tall block you want to understand exactly how it has been built. The tall block (1600 block ) is about 12 mm taller than the 1500 blockas standard at 210mm versus 198mm high from crank centre line. How you build it by decking the block and what crank , rods and piston deck height you use is an individual choice.

Decking the block to much can lead to serious weakness in the top of the block. What worried me with the engine you referred to was that I could not see a spacer and the top of the timing cover looked to match the top of the block. People do make taller timing covers but if the block had been decked down to match the standard cover I would be worried.

cheers
Rohan

[types26/36]

[quote="rgh0"] I could not see a spacer and the top of the timing cover looked to match the top of the block.
quote]

Rohan, blow this picture up and it looks like you can see the "step" where the spacer would be fitted, well it appears that way me.

[Petter Hval]

What should the correct (max) 711 M block height be to suit
the 122 link timing chain??
Regards
Petter

[garyeanderson]

What should the correct (max) 711 M block height be to suit
the 122 link timing chain??
Regards
Petter

The 122 link chain is for a stock height 711 (full height of 8.21 inches) which is set up with 5.23 inch rods Crossflow stroke (3.056) crank and a pin height of 1.46 inch. The 121 link chain is used where they mill all of the strength off the deck of the block. These are set up with same crank but the rods are 4.928 crossflow length and stock twin cam pin height of 1.53 inch. this gives a block height of 7.988. The block needs to be milled .220 inch or there abouts.

Gary

[Petter Hval]

121 link chain?? Please correct me, I`v newer heard of
chain`s with odd number of links.
Petter