Engine modifications...

[scoots]

We haven't got the full report on the damage to the engine in my S2 (see other post titled "Engine Fire"), but the head definitely needs to come off.

Sooo.... I was think that if the head is off and probably having machine work done, even if it's only a light skim, it may be worthwhile finding out what else can be done to improve things. Bearing in mind that this is a road car, is there much scope for gains from porting, changing combustion chamber shspes, increased compression, larger valves, four or five angle valve seats etc etc? I am not planning on changing the induction or exhaust system in the short term.

I live in Australia, so Lotus specialists with this kind of experience are thin on the ground.

Any advice/contacts appreciated....

cheers,

Ian....

[lotusguy]

scoots said:

We haven't got the full report on the damage to the engine in my S2 (see other post titled "Engine Fire"), but the head definitely needs to come off. Sooo.... I was think that if the head is off and probably having machine work done, even if it's only a light skim, it may be worthwhile finding out what else can be done to improve things. Bearing in mind that this is a road car, is there much scope for gains from porting, changing combustion chamber shspes, increased compression, larger valves, four or five angle valve seats etc etc? I am not planning on changing the induction or exhaust system in the short term. I live in Australia, so Lotus specialists with this kind of experience are thin on the ground. Any advice/contacts appreciated.... cheers, Ian....

Ian,

Porting is definitely a plus. Changing valves and grinds really won't yield that much. Better to look at a more agressive Cam.

So far as the seats are concerned. Given there was a fire, have them carefully inspected or plan on replacement. The seats are inserted into a hot expanded head which cools and contracts around them. Consequently the reverse is also true... heat up the head too much and your seals can work loose. I have an acquaintance who lost his waterpump 'V' belt and tried to limp the car home. It overheated so much, that he had 4 seats come undone. Much more spendy than just calling for a tow.

Also, if skimming the head, Lotus says that 0.040" is the maximum the head may be skimmed and still be serviceable. If you know it's not been done before, that's your limit. If you're not sure, I would not go beyond half that - 0.020". It is an issue of strength, but also one of altering the cam timing geometry. I know a guy who was ignorant of this limit, went beyond it and was forced to change to a different tensioner to keep the timing belt on and adjustable pulleys to get the timing right.

I would also plan on installing new valve guides as these too have probably been effected in the same way as the seats, and if you are over 40k mi., you're coming due anyway. Switch to the Bronze/Silicon guides which give a longer service life before starting to leak. If the fire was intense, consider springs as well as these may have been tempered by the heat. Happy Motoring! ...Jim'85TE

>> Edited by lotusguy on Tuesday 15th June 02:00

[bojangles]

seems to me if it was hot enough to temper the springs.. that the aluminum head would be melted....
Al melts at around 600, soft at 400...
and the steel would have been heat treated higher than that. Technically it should be fine inside the motor if the aluminum is ok..

Bruce

[lotusguy]

bojangles said:

seems to me if it was hot enough to temper the springs.. that the aluminum head would be melted.... Al melts at around 600, soft at 400... and the steel would have been heat treated higher than that. Technically it should be fine inside the motor if the aluminum is ok.. Bruce

Bruce,


Your logic is sound, I definitely concede the point. Happy Motoring! ...Jim'85TE