21 replies to this topic

[mikal]

Hi all. I just found the spec sheet for the camshaft fitted to my modified 1293 engine. I'd like to know what exactly it is.
The info I have is below;

Grind: Speco 4LA417
Cam lift 0.294
Valve lift 0.350
Duration: 290 for Inlet and Exhaust
Inlet opens 38 BTDC, exhaust 76 BBDC, overlap 72
Inlet closes 72 ABDC, exhaust 34 ATDC 

The cam is street friendly with very good low down torque, pulls away from 1500 rpm. I'm curious to know what this cam is equivalent to as I'm tossing up whether to change it. (Gearbox has to come apart due to dodgy batch of synchros). The engine has a highly worked head (11:1) running with a 45 weber, LCB and close ratio gearbox so it should be suitable for coping with a hotter cam.
Wondering what people's opinions are and what cams you are using for a similar spec engine.
I don't want a pig of a car down low but would like to use a cam that is appropriate for the engines potential. (In a previous life I had a car with a 649 cam that was fun but tedious down low. I lived on a steep hill and the only way to get the thing going was to spin the wheels..)
Thanks for any comments..

Cheers

 

Mikal

[mini13]

looks like an odd configuration for a mini, long duration and not much lift, i suspect its a profile from another engine.

 

I would recomend changing it, for somthing like a 286 or RE13,

[Spider]

Sorry but I just can't see that Cam pulling away from 1500 RPM, I think / feel closer to 3000 - 3200 would be closer to the mark. It does have - for the street - a long duration, fairly long overlap and a late closing Inlet. It would be a little better than the 649 you once had, but not by a lot. Certainly not a Cam I'd choose for the street.

[carbon]

+1 for Mokes comment.

 

When you say 'The cam is street friendly with very good low down torque, pulls away from 1500 rpm' is this your experience or part of the cam spec?

 

Also can't see how a cam with 0.294 lift at lobes should give more than 0.350 at the valve, even with standard rockers.

[ACDodd]

Unfortunately it is impossible to tell what cam you have from the figures given. We need to know 4 things to be able to tell you how it would run.

The duration at a stated check height,
The lobe lift (you stated this),
The rocker ratio,
And the lift at split overlap

Without these 4 it impossible to make a comparison.

AC

[mikal]

Hello AC and all,

 

My description is the way the car behaves. I've retarded the ignition timing because it's difficult to get high octane fuel in Indonesia, perhaps this is factor in the manner the car performs.  Also the car has not been dyno tuned though it does seem to have lots of grunt. Below is the info that came with the cam. Perhaps it has enough data to make sense of what I have?

 

[ACDodd]

Ok that makes sense, its about the same range as an MG metro cam looking at that spec. This is a good cam for a road engine. What are you looking at achieving?

AC

[mikal]

Thanks for the prompt reply. Does that explain why its friendly down low? I'm looking for a camshaft that relates to the engines potential but is not silly to drive in traffic. Perhaps I should stay with what I have? What do you think the useful rev range with this cam is? Having said that, I can't see me going beyond 7000rpm. The close ratio g/box is 1st, 2.839 2nd, 1.779 3rd, 1.309. The final drive I believe is 3.7:1

Thanks again for your input.

 

Cheers

 

Mikal

[ACDodd]

This would be max power at 5.5 to 6krpm, not really needing the close ratio box. It is an older design, low lift higher duration type profile. What fuel octane have you got available?

Ac

[mikal]

Here in Indonesia 95 RON if you can get it but the car is returning to Australia soon where I use 98 RON fuel..

[ACDodd]

For 95 ROn consider 9.75:1 max cR.

For 98 Ron consider 10:1 with that cam.

AC

[Spider]

Ok that makes sense, its about the same range as an MG metro cam looking at that spec. This is a good cam for a road engine. What are you looking at achieving?

AC

 

Respectfully AC, how do you come to that?

[ACDodd]

Cause their is about 0.060" inch of overlap lift delivered to the valves. And Mg metro is about 0.052" Ish at the valves. Its this figure which determines drivebility more than any other with camshaft specs. Duration is not a very good indicator at all.
This is why the cam pulls from such low rpm. It also has a wider LSA at 109 degrees. Again a nod to the tractable side of bringing that big duration under control. What this cam lacks is lift. Modern cam thinking would reduce the LSA by 4 degrees, punch this lift upto 0.310" at the lobe and knock 10 degrees off the duration would see more power everywhere in the rev range and a smoother idle if the overlap lift was retained at the quoted 0.060".
Ac

[Spider]

Cheers AC for that, I'll chew on it a bit.

 

I would agree it does appear a dated grind.

[ACDodd]

If you have been bought up on the duration rates a cam thing what you read from me will make little sense. Its one of the reasons I run 1 day cam workshops to enlighten those who have interest.

AC