Camshafts and Valve Inserts

[handi_andi]

Hiya all

Since the head will be off my twin cam shortly I have been contemplating getting an unleaded conversion done. Firstly, and this may seem a daft question but is there actually anyway of telling whether it has already been done? I did notice that the camshaft bearing top shells are all number stamped but don't know if they come from the factory like that.

Secondly, if I do get the valve inserts changed then I would be in a position to change the camshafts. I have just had a look at the QED website and see their 360 and 420 cams, what are peoples views on these and which would people personally recommend for fast road use on twisty scottish country roads.

Thanks

Andy

[Old English White]

... Andy ,
About mine , the Q420's , you should read this topic :
http://www.lotuselan.net/forums/viewtopic.php?t=16004
Many blocks of that forum help me with the understanding of the work to be done ... Simon , from QED , gave me every parts needed for these cams.
If you decide to use them , be sure to have them all .
Nearly one year after , I'm still a bit scared to put the lead on the floor on open roads , and allways worried to have to drive accross a trafic jam ...
This engine doesn't apreciate too long mid-revs progressions ... But on the track , and then on twisty roads ... just great!
This summer , on a run in :
http://fr.youtube.com/watch?v=Hz-xC1uFAwE
Christian.

[steveww]

Also have a look at the offerings from Piper.

Remember that an engine is a symbiosis of its parts. Just changing cams will have limited effect unless everything else matches. Wilder cams develop their power higher up the rev range and a standard cast crank is only good for 6500 rpm.

Where is the car going to be used? On the track it will be most of the time high up the rev range, on the road it will be most of the time low down the rev range. Remember torque gives acceleration and power gives top speed.

[rocket]

I may and often am wrong but i thought that elan heads did not require converting? I am under the impression that as they are alloy heads they came with hardened seats etc so are ok to run with unleaded...

Cheers,

Ian.

[rgh0]

Modern inserts are harder than older inserts for longer seat life with unlead. But "longer" is a relative term. The orignal Lotus seats from 30 plus years ago if there are any left in heads anymore would have been Ok for many thousands of miles on unleaded fuel. I would only bother changing the seats when they need it, and run on unleaded up to then and put in modern harder seats. The valve guides will probably wear and give you a smoky exhaust first anyhow

My plus 2 had the head done before I bought it around 25 years ago so it has older style seats I believe . Run it on unleaded for last 60,000 miles with no problem and only one shim adjustment about 30000 miles ago.

regards
Rohan

[rgh0]

I forgot to mention that any good machine shop should be able to do a hardness test on the valve seat material and tell you how it compares to the modern seats they fit.

cheers
Rohan

[Foxie]

Hiya all
I have just had a look at the QED website and see their 360 and 420 cams, what are peoples views on these and which would people personally recommend for fast road use on twisty scottish country roads.

Andy

Andy,

I have a QED big valve conversion with 420 cams . The result is amazingly tractable, I'd highly recommend

Sean Murray

[denicholls2]

Modern inserts are harder than older inserts for longer seat life with unlead. But "longer" is a relative term. The orignal Lotus seats from 30 plus years ago if there are any left in heads anymore would have been Ok for many thousands of miles on unleaded fuel. I would only bother changing the seats when they need it, and run on unleaded up to then and put in modern harder seats. The valve guides will probably wear and give you a smoky exhaust first anyhow

My plus 2 had the head done before I bought it around 25 years ago so it has older style seats I believe . Run it on unleaded for last 60,000 miles with no problem and only one shim adjustment about 30000 miles ago.

regards
Rohan

Rohan's advice is, as always, right on the money. Those of us who've been forced to use unleaded fuel for decades now know that although modern seats have been made harder, there's no reason to switch "to be safe". This is primarily a gimmick to get people new to unleaded fuel to invest in head work they don't need out of fear of catastrophic engine damage.

The failure mode is that you need new seats as the old ones "recess", which will likely reveal itself as out-of-tolerance valve clearances, the same way it would if you continued to run leaded fuel but at a rate imperceptibly (to somewhat) greater if you believe the hype.

If you need new seats anyway, then specify hardened ones even though it's likely that's all that's available. Otherwise, relax.

[ecamiel]

The 420s if these are the short duration cams, are amazingly tractable and perform well in the upper mid range 4000 to 6000.
But the biggest power and torqe improvement, even to a stock motor, is LARGE bore headers like the race ones TTR sells.

Eric
64 S1

[john.p.clegg]

Or even "blueprinting" the original exhaust manifold to head...

John

[mark030358]

does anyone have the torque/power curve for these cams?

cheers
Mark

[rgh0]

I have attached a sample dyno result for a 420 cam engine. With engines modified to this degree there are a lot of things you need to do to ensure you get the right outcome - it is more than just bolting in the cam.

I cant remember who I got this dyno data from but thanks and I hope you dont mind me republishing it

cheers
Rohan

[msd1107]

Rohan,

I get an Adobe Reader error "There was an error opening this document. The file is damaged and could not be repaired"

This is on both XP and Vista systems with the latest Adobe updates.

Could you try to upload the .PDF again?

David

[rgh0]

I have downloaded using reader version 8.1.3 and have no problem but I have uploaded a second copy to try

cheers
Rohan

[msd1107]

Thanks Rohan. No trouble this time