Thread: Top speed of 85ish..

Hi Chris. I would start by ruling out stale fuel by running a tank or 2 of fresh fuel through it. Then go to timing/spark plugs etc???
Cheers
Chris

If the motor hasn't been touched for five years then all that should be as it was, so after you put fresh juice in it make sure it's breathing ok. The air cleaner could be restricting air flow or a rat might have nested up the exhaust pipe.
More than likely stale juice though.
After that you have spark plugs, plug leads, carby, points, timing, tappet clearance, etc. to give a good going over.


Good Luck.
Cheers, Mick.

Also check for dragging brakes and soft tyres.

Other checks - throttle opening, badly incorrect toe in, flooding carburettor, manifold leaks, including dislodged pollution equipment, gummed up PCV. split PCV diaphragm.

John

Don't forget VERY significant effect of headwind or tailwind. A slight headwind can take the top off your speed, and a slight tailwind can enhance it significantly. At these speeds there is not much reserve power available, so a slight change in the total aerodynamic drag can make a big difference to your top speed. If you are testing on flat ground, doing runs in both directions is important.
The Land Rover's drag coefficient is around 0.9 (compared with 0.3 or thereabouts for a modern vehicle).
Cheers

C00P
(ours is a '76 LWB with Global Roamer O/D)

Originally Posted by C00P

.........
The Land Rover's drag coefficient is around 0.9 (compared with 0.3 or thereabouts for a modern vehicle).
Cheers

C00P
(ours is a '76 LWB with Global Roamer O/D)

Is it that high? I would have thought about 0.75-0.8. It will differ significantly depending on body type and wheelbase.

John

Theres a reason why Some landie drivers use the saying "aerodynamics don't count in low range."

I've seen sheds with better drag co-effecients than shed class landies (better quarter mile drag times too probably)

Thanks for the replies everyone. A long list of elimination ahead it would seem.

New fuel hasn't helped and I have just noticed a leak where the exhaust joins the bottom of the manifold - could this be the problem for not achieving previous speed? Those 3 bolts are a bugger to get at..

Cheers
Chris

Originally Posted by JDNSW

Is it that high? I would have thought about 0.75-0.8. It will differ significantly depending on body type and wheelbase.

John

My apologies. The figure without roof rack was 0.678 (ie, around 0.7 as you suggested). It rose to 0.917 when a long roof rack was added (which is a pretty typical configuration). There was an 8% reduction in the CD when a tyre was placed on the bonnet (no roof rack condition), and the CD went up to 0.972 when there was gear placed on the roof rack (ie, getting close to the figure for a flat plate of the same cross-sectional area- 1.28).
The model used was a LWB Defender, but I suspect a SIII would be little different (and possibly worse).
To get the full story, see here:

https://www.google.com.au/url'sa=t&r...,d.dGo&cad=rja

If that link fails, google "The Effect of Vehicle-Roof Rack Configurations on the Aerodynamic Drag Coefficient CJ BURGER"

Hope you find it interesting,
Cheers

C00P