What's that knocking?

[tonyabacus]

Hello All
Just had my engine replaced and on start up and till it is warm the car has a knocking or tapping sound, as if the carbs are hitting the top of the footwell. But there is sufficient clearance so that is not the issue. Further investigation revealed that the exhaust manifold is touching the chassis and there is no clearance whether she is hot or cold, but knocking disappears when she warms up.

The engine that was previously fitted was a tall block 711 casting, the new engine is a 681F casting, and apart from that nothing has been changed except the correct new mountings (for a Weber engine).

So my question is to do with the width of the two blocks and the spacers on the exhaust side of the engine, were the spacers modified in any way, or was the block wider? It looks as though the whole engine needs to move across towards the carb side perhaps 5mm, to give a little clearance, but is this possible without causing issues with the driveline. Never had this sort of problem with Elans in the past, so getting a bit stumped for why this should have happened. All parts removed to do engine swap were refitted to the 681F.

Anyone else had a similar problem or any other suggestions.
Thanks
Tony

[2cams70]

Yes the 711M block is wider across the mounts than the 681F.

[rgh0]

Yes shorter spacers than standard would have been used to fit the wider 711 block mounting boss

[vstibbard]

You will need to fit OEM length spacers on exhaust side with 681 block.
V

[tonyabacus]

Thanks everyone, as always the forum comes up trumps.

Does anybody have the dimensions of the spacers used with the 681F block or can measure them on their car or a sketch so I can get them made up.Some of the ads for these do not have sizes, so you don't know what you might be getting.
Thanks again
Tony

[types26/36]

Attachment from here.
https://lotusmarques.com/info/technical ... stallation

[tonyabacus]

Brian
Thanks for that piece of info, gives details on the 711 block I removed but not the 681F that is now in place, although I wonder if the width of the 701 was identicle to the 681F, do you have any knowledge of that?
Thanks
Tony

[rgh0]

Yes 701M and 681F and all earlier 1500 height blocks used the same Lotus 1.125 inch spacer

cheers
Rohan