Lotus Elan

Engine.....

PostPost by: vxah » Mon Jan 18, 2016 9:46 am

Did you check the valve timing before you pulled it apart? That would certainly make a difference to the compression pressures and the power output if it was wrong?
You can do all the machining you like but get that bit of assembly wrong and it's wasted?
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PostPost by: Type28 » Mon Jan 18, 2016 11:07 am

vxah wrote:Did you check the valve timing before you pulled it apart? That would certainly make a difference to the compression pressures and the power output if it was wrong?
You can do all the machining you like but get that bit of assembly wrong and it's wasted?


Thanks for the response.
I had the timing checked and it was ok. I was taking the engine out anyway because of the knock on start up, so may as well try and get somemore BHP out the engine whilst its apart is my thinking.
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PostPost by: Type28 » Mon Feb 01, 2016 11:40 am

Well my doubts about my engine have unfortunately been found to be correct.
Problems;
? Crank needs re ground- someone had fitted a set of bearings rather than do the proper job
? Pistons fine, but cylinders 4 thou over bored.
? Bronze valve guides previously fitted are too tight by about a thou.
? Valve seats recessed too far into the head, to the extent that previously someone machined some material of the top of the valves to make them fit!
? Pistons are 14 thou below block face at TDC
? Someone previously fitted front crank thrust washer back to front
? Cam bearings worn
? Fly wheel ring gear worn (even I spotted that!)

I am surprised the car ran so well, idled great, started first time, just felt sluggish, but great once it was going.

So the plan is to;

? Re grind crank and fit new bearings
? Re bore block and fit new high compression pistons
? Fit new valve seats, machine valve guides and fit new valves
? Machine block face removing 10 thou
? Fit new cam bearings
? Fit new ring gear
? Over haul carburettors
? Dyno test.
? Refit engine and enjoy.

When I purchased the car there was many invoices for work done to the car over the years, just goes to show you can?t really rely on that as proof that the work was done correctly. The previous owner paid over 2000 US Dollars for head work only 1500 miles ago- they obviously didn?t know what they were doing.

I can't think of much elso that can go wrong- if I can' find a close ratio box I will refresh the existing box before re fitting as I suspect the synchro rings are worn as you have to be very deliberate when changing from second to third.
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PostPost by: rgh0 » Mon Feb 01, 2016 11:52 am

I would not necessarily machine the top of the block. 14 thou clearance between top of block and top of piston is within the normal assembly tolerance.

Target inlet valve stem clearance is around 1 thou - so 1 thou to tight is certainly a problem !

cheers
Rohan
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PostPost by: Type28 » Mon Feb 01, 2016 12:10 pm

rgh0 wrote:I would not necessarily machine the top of the block. 14 thou clearance between top of block and top of piston is within the normal assembly tolerance.

Target inlet valve stem clearance is around 1 thou - so 1 thou to tight is certainly a problem !

cheers
Rohan

Thanks for reply- thay said the valves would have been sticking?
The idea with the new pistons and reducing the block by 10 thou was to give abit more compression and abit more umph.

Cheers
George
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PostPost by: Type28 » Mon Feb 01, 2016 12:53 pm

Rechecked my scribbled notes from my telephone conversation this morning- they said that the valve stem clearance should be 1 thou and it wasn't and the valves were sticking
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PostPost by: Type28 » Tue Apr 05, 2016 11:37 am

I am going to be re fitting my engine soon.
The gearbox is in the car. The car has a spyder Chassis.
The engine mounts bolt on to the chassis and the block and can be split in the middle.
When I removed the engine I split the mounts leaving half the mount on the engine and the other half on the chassis.
I think the mounts may get in the way of each other when I am refitting the engine- any tips from anyone who has done it before?

Image

Dyno sheet for completed engine- to the people who know about these things, does it look OK?

Cheers

George
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PostPost by: rgh0 » Tue Apr 05, 2016 12:47 pm

Dyno curve looks good. A bit hard to interpret without knowing the rest of the engine specification but the rest of the thread implies a standard sprint specification. 136hp is a bit optimistic even for a 1600 cc with the rest standard sprint twink but that result all depends on details such as exhaust system used on the dyno and what ancillaries were running ( no water pump and no generator running will give higher output measured on the dyno).

The nice smooth torque and power curves imply it is well built and tuned

cheers
Rohan
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PostPost by: Type28 » Fri Jul 22, 2016 1:37 pm

A little update slightly later than planned.
The engine is back in and I rebuilt the gearbox whilst the engine was out.
Although the engine had previously sounded ok and ran fine, it is only now that I appreciate how down on power it was. The car is transformed and it now has the power to match the handling on the great B roads around my area.
These little cars can be fiddly to work on, but just take your time.
I fitted gear box first and jacked it up at the front, the engine slipped straight onto the shaft and that was almost job done!
Again, thanks for all the help and advice received.

George
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PostPost by: l10tus » Wed Jul 27, 2016 12:53 pm

Nice thread, good pictures and happy end, great thanks!

Thanks for sharing with us!

Regards,

Phil.
Philip.

UK '72 Sprint DHC

Sometimes my Lotus makes me cry.
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