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Aragorn

V8 Performance Oddness

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I should add that i think the engine is a little rich, judging by the smell from the tailpipes, i'll need to back off the mixture just a smidge.

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Its better for sure, but still doesnt quite meet my expectations.

Well the first question is what are you judging it against? What do you usually drive? Have you driven any similar vehicles to see if they're better or worse?

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Well i guess thats it. I dont drive anything at the moment (no licence), but the missus drives an A4 1.8T as her daily.

I just assumed that 2tonnes of landrover plus 140hp would be better than this. The missus' previous car was a 1.3 fiesta which has about 70hp and weighs just under a ton. So power to weight ratios should be similar, yet the fiesta didnt seem this slow.

I've been in my mates defender 300tdi a while ago and it seemed a lot more willing and responsive than the disco does.

I guess its just a tired engine combined with usually driving (well being a passenger in) a 150hp saloon car skewing the perception of "normal".

I took the videos so some people could make some comparisons.

An idea of how it compares accellerating from 40 to 50 for instance would be useful to see if this engine is actually down on power, or if i'm just expecting more than i should be!

Cheers

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running rich does not mean slow. when you rebuilt the carbs, did you replace all the gaskets, or at least re-seal them?

yes lean out the mixtue and make sure your carbs have both buterflies set the same on there adjustments. really rich mixtures will keep your spark plugs wet, and the engine wont like to start easily. pants power might be a weak spark. check you timing and advance it if anything, on the dizzy. but not too much.

in fact, check the butterflies, thencheck your dizzy is set at the correct advance before you touch the carbs mixture as it might be you are simply not burning the fuel as the timing is off.

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Timing is fine, if anything its over advanced below 3k (EFI dizzy on a carb engine) but theres not a sniff of pinking.

I didnt replace any seals or gaskets (bar the carb to inlet) but there wasnt anything wrong with the carbs, they were in really good condition inside. I just reset the butterflies to default and the jet height to default and then set them up as per the rebuild manual. All this is covered earlier on in the thread!

Engine starts perfectly. Cranks over two or three times and burbles into life, didnt even need the choke after being parked outside tesco for over an hour.

It certainly has got better after each fix (leads, plugs, cap and rotor first, then the dizzy itself, and now the carbs) but it just still doesnt meet my expectations.

If someone with a Disco (even a TDI would do) could take a similar shot (or even just time it) of accellerating from 40 to 50 in 4th gear, it would give me a reasonable idea if my truck is performing as it should and my expectations are waay off, or if it is actually poor.

Looking at my video, it seems to take 8 seconds to pull from 40 to 50, and over 20 second to accellerate from around 20mph to 60mph. As an example, a Corsa 1.2i with 45hp and weighing 800kgs (56bhp/ton) can accellerate from 0-60 in around 17-18 seconds. This truck with (apparently) 140hp and weighing around 2 tonnes (75bhp/ton) is taking 20secs just to accellerate from 20 to 60...

Even a TDi, with 110hp, should be able to match the corsa's 18 second 0-60 so that suggests to me that the V8 is making LESS than 110hp... :(

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Yes, I would say its making well less that 110bhp and the reasons for lack of low to mid range performance are fairly clear.

You have already measured the valve lift and the figure quoted indicates that the cam is badly worn, so couple those numbers together with the fact that the rockers and shaft will also be worn and the valve lift on some cylinders is maybe half (or less) what it should be. Remember, hydraulic lifters are very good at hiding top end wear and the engine will sound quite sweet……..

However, also factor in that OEM timing chain will have also stretched considerably and this has the effect of retarding the cam timing. Retarded cam timing has the effect of making the engine very lazy and destroying the bottom end and mid range torque. OK for a racing application as it does improve the very top end torque……. but not with reduced valve lift !

See here for streched chain (I have seen much worse than this) ......... http://forums.lr4x4.com/index.php?showtopic=49222

If you are not convinced, you could always measure the point of lift and check it against the manufacturers data. This process is done on engine builds with vernier cam gear and normally refered to as 'dialling in the cam'. Look here at post #27 also look at post #34 wihich details rocker & rocker shaft wear... http://forums.lr4x4.com/index.php?showtopic=14006&st=20

TBH, I would be very surprised if you are making 80 – 100 bhp, but because of the worn cam & timing chain the power curve will not be as expected .

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Bear in mind a LR has a lot more inertia and softer suspension than a Corsa, so it will wallow and feel a lot softer/slower even when it's going fast. 100mph in a Range Rover is a lot more relaxed than 100mph in a Corsa.

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