Another question about Cams

[pauljones]

Guys,

Im after some solid advice about camshafts swaps, Firstly,i dont want to take the head off,i intend to change the camcover,and cams to get a bit better performance.So what cams are reccommended,im thinking the QED 360 or this one.

http://www.burtonpower.com/parts-by-fit ... 6-ltc.html.

Does any one have anything else that works,mine is EFI so i know it will need a re set when done.

Thanks all.Paul

[gearbox]

EFI and hot cams, a bit beyond my experience, but suggest you call QED or Burton and get their advice. Don't think many here have gone down the same road. Good luck.

[john.p.clegg]

Paul

No good solid advice but I've got EFI with a 420 cam on the inlet and a 360 on the exhaust and after fiddling (tuning) with the EFI will be on the lookout for some good timing figures,so will watch this space as they say...

John

[rgh0]

Paul
What cams do you have now.

Without talking the head off and changing the valves and springs to suit a higher lift you will not do much better than the Lotus big valve sprint cam with 0.360 lift and 272 degrees duration.

The QED 360 is the equivalent sprint cam.

The Burton BLF46 at 0.380 lift is marginal with the standard springs as I would not increase the lift above 0.360 inch without removing the head and checking the valve spring installation and probably changing the springs. The 280 degrees duration is good for a higher lift cam but I would go for something like the QED 420 if going for a better road cam. The 0.420 inch lift and 280 degree duration of this cam is close to optimum for a fast road cam.

cheers
Rohan

[pauljones]

Thanks guys,

My problem is I don't want to take the head off and as I understand it, And stand ready to be corrected, that 360 too 380 is about as much as you can go as a straight swap. To go any more lift will require the head off and being machined for the correct springs.

Rohan, I think looking at my dyno that I will have standard size valves and 105bhp, B spec cams I think. So the point of the exercise is best "bang for buck"

John, I also thought of different cams for inlet and exhaust, will be interested in your findings. Its the same technique ive used for building v8's,we call them dual pattern camshafts

[john.p.clegg]

Paul

There is a mathematical formula re.the amount of lift required to give maximum airflow for certain valve head diameters and with 1.625 inlet and 1.4 exhaust the 420 and 360 cams are about right...


John

[MickG]

X=1/4 of Y
X is the maximum lift
Y is the valve diameter
Further lift will not increase the air flow.

Taken from the Burton Engineering catalogue

Mick G

[rgh0]

The 25% of diameter for lift formula is a starting approximation. But for the twincam head when it is well ported you find flow increases up to around a 0.5 inch lift for both the inlet and exhaust with 1.62 diameter inlet and 1.4 diameter exhaust . The maximum lift you should use is a road engine is governed by what lift can you get at a usable maximum road duration of around 280 degrees beyond that duration you start to loose midrange torque which you don't want on a road car. Thus maximum lift possible for a road car is around 0.42 to 0.44 cam lift depending on whose 280 degree cam you buy.

The maximum lift for a standard valve and spring set up on a twin cam is 0.37 to 0.39 depending on the assembly tolerances. Burtons advise caution on using their 0.38 cam without checking the assembly tolerances and that modification to the valve train assembly may be required. I would not use a cam above 0.36 lift without taking the head apart to check all the dimensions and to determine if I need to make changes. If I did that then I may as well go to a 0.42 to 0.44 lift cam

If you don't want to take off the head replace your B cam with the Lotus big valve sprint D cam or the QED 360 cam which is basically the same and you will get a major improvement.

cheers
Rohan

[pauljones]

Rohan,

Thanks for the advice. I got to speak to Paul Exon while chatting to Qed,he just happened to be there at the time. I was told i will need to check for larger valve cutouts in the pistons anyway. So it looks like my simple aproach isnt exactly going to work and the head needs to come off. Now all i need is a small lotery win!!

Thanks,Paul

[john.p.clegg]

Post by: Etienne 7 ? Thu Apr 25, 2013 8:38 am
Hello all,
Paul sent me a personal message on Sunday 21 April, I try to reply to it but I am unsuccessful as it says: "Some users couldn?t be added as they have disabled private message receipt.".
Would one of you know him and could either give me his personal details or tell him that I am trying to contact him.
Thanks in advance,
Regards,
Etienne
Lotus Seven 1965 S2
can be seen here, if not on the road...

Etienne 7
Second Gear


Posts: 56
Joined: 23 Sep 2011
Location: Bristol, UK

[pauljones]

John.

Thanks for forwarding that. I didn't realise my setting had changed.

I thought people were ignoring me, I AM joking off course.

Paul

[Mazzini]

So is a CPL2 much the same as a Sprint/Q360 cam?

[john.p.clegg]

Not got details for the Q360 but the CPL2 is

.350 lift, 270 duration, 25/65/65/25 timing, 110 mop, 1500-6500 Power-band.

John

[collins_dan]

I just switched from l2 to qed 360. Both are about the same. Qed 360 has a bit more mid range torque. L2 are more high reving. The car has strombergs and is very quick. Dan

[john.p.clegg]

Dan

Do you have the specs. of the qed 360?
Thanks
John