Thread: 86 3.5 With a Lack of Top end Power HELP

Sorry guys.

Yeah when driveing on the highway.
Fifth gear you can get the engine to between 2000 and 2500 and thats the max, the speedo only shows 80K but allowing for tyre size 32's that would be about 85K.
At this point the foot in pressed into the carpet, you can let it go and then press it again it will accelerate untill it gets to between 2000 and 2500 again then it gets no more. Unless you find a down hill bit
Will try the timing in the week, and also inspect the cams.
Cheers for the advise so far.

Originally Posted by twigman

Fifth gear you can get the engine to between 2000 and 2500 and thats the max, the speedo only shows 80K but allowing for tyre size 32's that would be about 85K.

Your Tacho readings don't make sense ......

My 90 RRC has approx 30" tyres and it = 2200rpm for 100 kph (approx)
Your ride is in fifth (overdrive) with 32" tyres and so, should it not be be less revs to achieve 100kph (let alone your 80kph) ....

Originally Posted by twigman

Will try the timing in the week, and also inspect the cams.

There are a couple of more checks to do, before you remove the manifold & go down to tha "bowels of the motor" to look at the CAM


How far is Newman from your location?

Cheers
Mike

Newman is about 280K's from Tom Price?

About the speed thing I think I might take it out with the satnav and see how the speed looks on that they are useualy accurate.

Originally Posted by twigman

......
Record advance with vacum connected, what sort of figures am I looking for?.....

Mike 90RR's link to my advance curve is "all in" at 31 degrees BTDC at 3K RPM without vac. This is a modified curve for a 3.9. Stock curves for a 3.5 and 3.9's will not be as much and will occur later in rev range than that.

A vacuum pump is best to test a vacuum unit but not having one try this. Plot the amount of mechanical advance at say 250 RPM steps both with and without vacuum connected. Vac advance should kick in by 1,100 RPM and majority of vacuum advance component of say 15° be all in by 2,250 RPM and certainly all in by no later than 2,500 RPM (at no load).

If not and say vac advance is still working beyond 3,000 RPM and doing most of its work between 2,000 and 3,000 RPM then vac advance is either well past its use by date (vac rubber gone stiff) or maybe the wrong unit for a EFI RV8. Note this is test only as actual vac/RPM are quite different under load.

Not quite sure what your synptoms are but a siezed mechanical advance will feel OK at low revs but power falls away and feels flat as the revs rise.

just a thought, is the accelerator cable ok ? pedal all the way down in the car = throttle butterfly all the way open ?

Thank you for all the advice with this one so far.
Did a bit more investigating today.
Checked mech advance and it moves with a little bit of resistance.
I did note that the electronics under there look well worn and dirty, would a new one of them make any differnace.
I know it says no adjustment required on the cover but the car has done 300K km's and it looks like the original one.
Checked the fuel presure and its getting a full 5 PSI from the pump.
Just thought as I was under there would check that out.
Checked the timeing at idle can only get it to TDC accroding to the marks.
Now for the wierd thing when you rev the engine the timeing redards to between 3 and 6 after TDC.
Not sure but that last bit does not sound right.
Gonna wait now till I get the new leads and a Lucas rotor arm.
As all this started when I changeing, plugs, leads, rotor arm and distributor cap thinking new parts will work more effeciently.
Teach me for thinking.
Have changed the vacum advance unit for a new one, but today put the old one on to see if it made any differance it didn't.

Something is not right......Timing at idle should be between 3 and 10 degrees BTDC with no vacuum. If you had vacuum connected when you reved engine and it retarded you may have a retard style vacuum which is wrong unit (proper unit should provide around 15 degrees of advance) or vacuum arm may have slipped off. Check mechanical advance with timing light...with no vac you should get steady not jerky advance increasing to around 28 degrees BTDC at 3,500 + RPM. Fuel pressure at the rail should be 36 - 39 psi (not 5 psi) with no vacuum connected.

Are you sure you are reading the advance the right way? Advance, ie BERORE as written on the crank pulley is to the right of the timing pointer. Turn the crank with a socket so the marks are visible under the car. white-mark TDC with a long mark and the 6 and 12 BEFORE marks with shorter marks. To get more advance the dissy body needs to be turned anti-clockwise, so the advance capsule is turned towards the radiator. BTW the pick-up under the clear plastic cover isn't strictly electronic, it's magnetic. It is rarely the problem with electronic ignition, the amp and coil are.

Also make sure the vac advance is hooked up to the advance plate.

For piccies of the dissy internals see my threads on ignition upgrades, linked here:

Lucas ignition amplifier replacement by Bosch 024

Lucas V8 dissy nylon clip repair method.