Rover Engine Cam Specs

[Ian Anderson]

The Dax hit the road in July and since then I've been battling with what I thought was bad fuelling causing serious kangarooing when trying to drive as a slow speed in traffic (say 30mph 3rd gear 1500 rpm) Suddenly the beast kicks in and damn near lifts the front wheels before shutting down and almost locking the rear end.

I fitted the replacement (and known working) ECU the kangaroo stuff is worse than ever.

After replacement I found a hand written note on the back of my ECU saying modified for 102 cam.

I then asked the question elsewhere and was told the cam was
43/79/79/43 302 degrees .500" lift

And someone else says it is a very high end fast road / rally cam no good for under 3000 rpm and better suited to oval racing between 3000 and 6500 rpm.

So perhaps I've been hitting on the ECU when the problem was elsewhere.

Do these numbers look radical to the engine gurus on this site? Or is it a tamable thing with correct fuelling. Would a carb system be better?

Hell I'm confused! but can offer the following

Just have the bill where the bloke that started the project paid JE £3247.60 in 1990 to balance and build the engine.

Work sheet says
Strip unit (brand new engine)
M/c piston cut outs for JE102 cam and balance
Balance Conrods
Balance crank and front pulley
Lighten and balance flywheel
Balance Clutch cover
Fit 102 + Hi rev lifters
Fit Vernier and duples timing chain
Fit JE Double valve springs
Curved Seats and Large Exhaust Valves
Open exhaust ports to "our" size
Fit large trumpets andmatch to inlet manifold
Latest shape combustion chambers
Modify ECU and tune resistor
Dyno with "Tommy Cooper" installed
Oii feed kit and tadpole

When I got it the heads were marked in pentel pen "TVR spec"


Ian

 

[Ian Anderson]

Ok
The engine is a 1990 Rover engine 3.9 with hotwire fuel injection

Suppose that would help

Ian

 

[Russ Noble]

Ian,

That does appear to be a fairly radical cam for a 3.9 Rover on the road. It would be handy to know the specs at .050". The cam in my 4.9 TR7V8 race/rally engine seems to be smaller than that one. But there are other factors that govern cam characteristics.

Wouldn't it be easiest just to phone JE and ask them how the cam should behave?

Cheers

 

[Jac Mac]

Ian ,

With 86 deg of overlap (43+43) there has to be some reversion taking place at low rpm which will be giving some confused info to the ECU. Also 300+ deg duration is quite a lot for a 3.9 litre (238 cu in) capacity.Your cam is ground on 108 deg lobe centers so is more suited to short track/sprint type operation than continous high rpm operation. ( I am working off the figures you have given above). A good road cam with this duration would have 110/112 deg lobe centers.

Jac Mac

 

[Ian Anderson]

Jac

Thanks for that
So would it be better suited to a Carb feed?

they are using a Weber / Edlebrock 500 over here on these motors and getting some reasonable results.

Russ

Yes I need to get hold of JE again and get more info out of them - last time it all sounded like costing a fortune (£1600 to check tune and reset the ECU so cheap they ain't)


Thanks for the info - makes more sense why the car does not like travelling at low hrottle

Ian

 

[Jac Mac]

Ian,

If those specs for the camshaft are correct I would suggest that you look at replacing it with another of less duration. Around 270deg total duration[225 deg @ 0.050"] on approx 110 lobe centers should make you a happier driver, and still keep your injection. Speak to some local guys who road drive/race TVR/TR7 and find out what they are using, avoid the local pub bullshit types.

cheers
Jac Mac

 

[Russ Noble]

Ian,

I agree with Jac Mac here. Change the cam.

I think the spec's he's suggested will give you a pretty sweet road motor. Although a little more duration and lift on the exhaust doesn't go amiss with Rover heads.

If you change your cam, don't forget to put in new lifters at the same time.

Cheers

 

[Ian Anderson]

I spoke to JE motors again and with the info on the cam being a 102 they agreed that the cam eas a "fery high end road cam and would probably be better suited to a rally type Rover Saloon. They thought they could remap the ECU in about 4 hours of work (£300 ish) and get it drivable but never good as a road car. They could suggest a number of cams with newer grinds that would give similar performance but be more Road happy. Cam about £150 - £250 + followers and fitting then remap - best part of £1000 plus VAT.

Perhaps just time to buy a second motor and build a street one from scratch. There seem to be quite a few Range Rover breakes around. £250 for a running high mole engine.

Oh what to do?

Ian

 

[Russ Noble]

Ian,

Once you talk about electronics and ECU's, I avoid them like the plague! Conventional distributor and carb for me!

But changing the cam to something more suited, and fitting standard Rover lifters which should be more than adequate for road use is not rocket science and there should be nothing to worry about with P/V clearances as you're going to a smaller cam. Springs should probably be OK so long as they're not rock hard. Do it yourself and save some money. May be the standard ECU would work OK with a mild road cam? Could be worth a try, you've got nothing to lose. You can always get it remapped later if it needs it.

All the ECU literate guys will probably chime in with better info than me

Buying a stuffed motor when you've got a good one seems like a hiding to hell IMHO.

Cheers