Lotus Elan

High lift low / duration camshafts

PostPost by: Petter Hval » Tue Jul 01, 2008 9:56 pm

I`m after a set of hig lift camshafts with an ekxpressed
period and a seat to seat duration of 290 - 293 degr.Does
anyone here know where to go?
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PostPost by: garyeanderson » Tue Jul 01, 2008 10:27 pm

Not exactly the spec you state but probably worth looking at.

Q420 cams 285 degree wit h .420 lift
The link has a chart with specs

http://www.lotuselan.net/forums/viewtopic.php?t=16004
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PostPost by: rgh0 » Wed Jul 02, 2008 1:30 am

John McCoy at Omnitech does a 490 lobe height ( nominal .480 valve lift) with seat to seat of around 290 degrees and duration at .050 lift of 260 degrees.

He currently recommends this on the inlets for his competition heads with his .440 lift 280 degree seat to seat, 250 degrees at 0.050 lift cam on the exhaust.

He is currently struggling to get good quality new cores to grind these cams out of so you may need to source your own new cores if you want the cams soon.
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PostPost by: garyeanderson » Wed Jul 02, 2008 10:11 am

more cams from Elgin Cams

http://www.elgincams.com/c-lot.html

main link with lot of cam info
http://www.elgincams.com/
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PostPost by: bill308 » Wed Jul 02, 2008 10:43 pm

From a fast road occasional track day perspective, moderate duration/overlap and moderately high lift cam profiles seem the way to go, especially if some porting and a modest CR increase are also factored in.

Does anyone have experience with John McCoy, Elgin, or D. Bean cam grinds?

What's the impact of today's oil formulations on fast ramp and moderately high lift cams?

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PostPost by: rgh0 » Thu Jul 03, 2008 10:04 am

The McCoy .440 lift, 280 seat to seat, 250 at .050 lift cam on inlet and exhaust suitable for road and track use with a very good flat torque curve. It produces max power around 7500 to 8000 rpm with a good ported head and big valves and big carbs and exhaust but with its flat torque curve still good to use in a less developed road engine with a 6500 to 7000 rpm limit.

There are several keys to good cam and tappet life regardless of the amount of zinc on your engine oil in your twin cam.

1. Always use new tappets with a new cam
2. If using steel tappets and steel cam try to get a 5 to 10 Rc hardness difference between the two. if using cast iron cam or tappets this hardness difference not so critical but ensure hardness of both tappets and cams in 50 to 60 rc range whether steel or cast iron
3. Keep the nose load on your cam less than 200 lbs
4. Phosphate coat the cam and tappets if using steel components
5. Use a lot of good quality assembly lube.
6. Use a good quality running in oil that will have the correct level of ZDDP to prevent scuffing and galling during the run in period.
7.On startup run for 20 minutes between 2000 and 3000 rpm constantly varying revs
8. Change to a good quality synthetic oil after the first 500 to 1000 miles. If really paranoid about zinc levels select one of the diesel engine synthetics, racing sythetics ( eg Redline) or others normal brand name synthetics now being formulated with higher levels for the concerned enthusiasts.

Steps 1 to 7 are more crtical than what oil you choose to use in step 8 in achieving a good cam and tappet life.

cheers
Rohan
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PostPost by: elandoc » Mon Jul 07, 2008 1:10 am

Hi Rohan,

Currently running in new engine on Castrol 15/40 diesel. One of our members is a chemist with BP and recommends this as the one with the highest ZDDP levels. Also diesel oils more detergent - handy with all the mud being made by all those new bits rubbing. Make sure engine temp at least 85. Cooler is good for power, but the oil needs heat to burn off combustion by-products, especiallt at the relatively low revs of the running in period.

Cheers

Patrick
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PostPost by: rgh0 » Mon Jul 07, 2008 2:12 am

Hi Patrick

I have used Penrite Running In oil for the last few years for the initial break in of my engines with good success. it has the right formulation to engine good bed n of rings and cams. i change it after the first 2 to 3 hours of running to Redline 20/50 synthetic..

cheers
Rohan
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PostPost by: fjbm » Mon Jul 07, 2008 9:21 am

Hi

Can anyone please recommend a good fast road cam without this high lift so I can use it with the normal pistons and head?

I was thinking about Burton's BLF46... looks like the BLF14 but with less lift.

What about the Kent's BD3?

Have any one ever tried any of these?

Thanks
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PostPost by: rgh0 » Mon Jul 07, 2008 11:57 am

Generally a longer duration cam without more lift and head porting is a waste of time.

You may get a little more top end power from something like the Kent BD3 with 290 degrees duration and .35 lift but it will only be 5 or 10 more than a sprint cam and it will all be at the top end and at the expensive of a big hole in the torque curve. Maximum out of an unported twink head below 7000 rpm in a 1600cc engine is around 135 hp.

The Burton BLF46 is a little better with shorter duration at 280 degrees and higher lift. At .38. Its pushing the limits on the standard spring assembly and you would have to check carefully for coil binding.

I assume both suppliers are quoting seat to seat duration but they may be quoting cam period above base circle which is typically about 10 degree longer than seat to seat. I always ask for 3 durations for any cam.

Cam period above base circle
Cam period from valve seat to seat ( allows for design clearance ramps)
Cam period above 0.050 lift.

If you get all three then you can do a real comparision between cams and have some chance of assessing their performance potential via a computer simulation. If you cant get that data then dont buy the cam unless you like experimenting.

I personally would put in the Lotus Sprint cam or equivalent and put in the sprint carb jetting and dizzy curve if you dont have it already if you want to leave the rest of the engine standard.

cheers
Rohan
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PostPost by: fjbm » Mon Jul 07, 2008 1:19 pm

Hello Rohan

Thanks you very much for the explanation.

I'll fit new valve springs which are intended for high lift cams. The only reason I'm thinking about normal lift cams is that I plan to use the std pistons I already have (with the small valve cuts).

I think that I need to change to the hepolite pistons with the large valve cuts to fit a Q420, right?

I'm also going to port the head to stage II/III.

What should I have in attention if I'm going to fit a high lift cam?

Cheers
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PostPost by: steveww » Tue Jul 08, 2008 9:43 am

There is the Piper LOTBP270 which is very close to the standard Sprint profile.

As Rohan has already pointed out wild cams are no advantage unless matched to a bottom end that can handle the rpm. If you are going to use the car mainly on the road then a good spread of torque across the rpm range is more important that absolute top end power.
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PostPost by: fjbm » Tue Jul 08, 2008 10:48 am

Hello steveww

Piper's LOTBP270 look like a copy of the CPL2 profile...

Have anyone ever tried the Burton's BLF46?

Does anyone know the values of QED's Q360? Is anyone running it?

What I intend id to have more torque all the way and also a little bit of more top end power until the 7K rpms.

Thanks
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PostPost by: rgh0 » Wed Jul 09, 2008 10:59 am

fjbm wrote:I'll fit new valve springs which are intended for high lift cams. The only reason I'm thinking about normal lift cams is that I plan to use the std pistons I already have (with the small valve cuts).

I think that I need to change to the hepolite pistons with the large valve cuts to fit a Q420, right?

I'm also going to port the head to stage II/III.

What should I have in attention if I'm going to fit a high lift cam?

Cheers


Sounds like your aiming to build a 150 style hp engine based on a standard cast iron crank and rods with upgraded head. The Dave Bean catalogue gives a good description of this sort of development

Bottom end needs large cut outs in pistons as you describe. ARP rod bolts worthwhile if using above 6500 rpm max on occassion. But put in a good electronic cut out set at less than 7000rpm as the standard bottom end goes bang at around 7300 rpm and the engine if built well will be more than happy to rev to 8000 rpm. The rest can be left as standard but carefully balance everthing. Careful measurements also needed to confirm you get the 10.5 to 1 comp ratio you need.

Ported head and larger valves needed to get the true benefit of a higher lift cam. A cam like the QED 420 is a good one for this application and delivers the 150 hp target which is about the max you can get out of road compression 1600 twin cam at 7000 rpm. In the for sale section is a dyno curve of an engine in a plus 2 with this cam that produces this figure. Off set dowels or vernier adjustable sprockets requied to ensure you can time the cam correctly.

Setting up the valves for a high lift cam takes some attention to component detail to get it right. The high lift cams typically come with a 1.1 inch base circle versus 1.2 on the original Lotus cams. This keeps the nose of the cam small enough in radius so its still fits on the bucket and also provides more room for high lift springs when used with longer valve stems and thin steel tappet followers. You need to work through the detail of your head and cam measurements to ensure you get a correct set of components that work together. Some one like QED should be able to help you with component selection but you need to do some critical head measurments to make sure you get them right as most heads have been worked on lots by now and often a long way from standard in dimensions.

The high lift cams if cast iron should have a special long bolt fitted to ensure they dont break under the increased drive loads they require.

You also need to go to around 34 mm chokes in the carbs and rejet them to suit and a big bore exhaust header and tail pipe to match the breathing capacity of the head and cam. You also need an ignition advance curve to suit the engine. The UK non emissions sprint curve is pretty good

The link that Gary posted in the second post on this topic has some more detail on the head set up and measurment requirements with high lift cams that I previously posted.


cheers
Rohan
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PostPost by: Petter Hval » Wed Jul 09, 2008 10:18 pm

Rohan
Where is this special long bolt for the cast iron cams fitted?
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