Loosing power uphill or under load any ideas?

[Worby876]

Ok Ive posted pics of the compression tests for each cylinder...


I will do some more pictures & Maybe even a Video clip too

[Worby876]

Here are some Videos I did today looking at the motor on LPG and Petrol
and looking at the vacuum gauge settings and then with the timing light.
1. http://www.youtube.com/watch?v=msRoeO33D2o
2. http://www.youtube.com/watch?v=f3XUmFDRc5w
3. http://www.youtube.com/watch?v=uYiIZMaXaqM

I started adjusting the lifters/pushrods but broke my only 1/2" socket

so it'll keep till next weekend

cheers

[Merlin]

theres nothing wrong with the valve train because the vacumm guage would flutter at idle if any valves were unseated so i would be looking at ignition faults for your answer    Cheers Neil

[LS120]

im in agrement with merlin on this one.. after going for a test drive i could idle fine rev it upto 4000rpm+ & all is good, under load it cakles, back fires no power...
just about ready to push it off a ciff...   

then remembered i had a blue Elec dissy setup.. & folowed the wookbook on old holden on replacing the old red dissy with the blue elec one..

2 hours later & it starts first turn of the key.. idles better as well..

i think you prob could be ether the condenser in the dissy or coil as that is what 3 people whom owned 6 & 8 cyl holdens have told me it could be..

and also check the vacume advance is moving ok..

test drive is today with the elec dissy in..

[Warren]

Worby

In one of the vids you state the idle speed as 350 rpm, I'm not sure but that sounds a bit low to me, I thought around the 500 rpm was around what it was ment to be - I could be wrong though.

Also when at low revs you move the lever to the gas position it idles better because ther is more advanced timing, but if you run to much advance at working revs you will have issues.

The timing and tuning should be optimised for the working rev range ie 2500 rpm to 3000 rpm, thats where the engine does most of its work, not idle speed.

Your dads lever setup was to overcome the difference in timing advance needed for gas and petrol, most gas conversions will time an engine half way between, or further towards the Gas advance, predomanatly because it will be running on gas more often than petrol.

This is a compromise that your dads setup counters by manually shifting the dizzy to the optimum position for each fuel.

I would run the engin on gas with the lever in the "gas" position and time the engine at 2500 rpm, then if it idles a bit rough then just up the idle speed a bit.

Then change over to petrol, switch the lever to the "Petrol" setting and check the timing again at 2500, once again if it idles a bit rough just up the idle.
 
Then test drive it and see how it goes.

I'm not sure if you know but when switching from Petrol to gas you need to run the engine with both fuels shut off for a time to allow the carby to be drained of fuel otherwise if you switch straight to gas you get the combination of Gas & petrol and have way to rich of a mixture, this can cause the poping and farting and explosions in the exhaust as the unused fuel mix passes through the motor unburnt and into the exhaust system and is ignited by heat or flames from another cylinder.

The switch to turn between Petrol and gas should be a 3 way switch with Gas at one end petrol at the other and both shut off in the middle.

Warren

[LS120]

well that was it.. after a little fine tuning with fuel mix & dizzy its all good.. the problem was in the dizzy.. either the condenser or points or coil...

hope you find your problem soon..

[Worby876]

The 350 RPM was what it drops to when she is running really rough and nearly stalls when on LPG when the Lever is in the Petrol position.
When running on Petrol she idles nicely around 550 RPM.

IM getting a bit frustrated or confused now..because I thought the problem was definitely the push rods and lifters not properly set.

But now the concensus seems to be that it more likely a timing issue.

I've done a timing light test and it seems the dot or mark the notch on the pully or harmonic balancer is sitting well before the long white
line on idles with the vacuum advance blocked to the dizzy. and then when I move the lever to Petrol its past or advanced by about and inch or so.

I need to do some more reading and research to figure out where it should be.

Also one suggestion was to time on LPG at 2500 RPM ...er What does that mean?
Um rev to 2500 and turn the dizzy till the dot is in line with the line or 6 degrees advanced or what??/

Cheers

Ian

[JOE RYAN]

Have you checked that when the mark on the harmonic balance is aligned with the TDC mark on the timing gear cover on the block that the No1 piston is in the Top Dead Center position, this can be easily done by taking the spark plug out and with a torching shining into the No1 cylinder through the spark plug hole have an assistant watch the piston come up as you turn the engine over by hand and align the timing marks

Cheers
Joe

[Rothu]

Great collection of videos! By all accounts now that I can see the gauge/s in action, the lifters have settled. So that's settled.

Now I'd check the push rods aren't bent. Maybe when you had that massive backfire, a valve/s were sticking, and so the rods had nowhere else to go but sideways. Set each cylinder at TDC in order, and twirl the rods. You'll see if they are bent.
Good work so far!

[Warren]

The 350 RPM was what it drops to when she is running really rough and nearly stalls when on LPG when the Lever is in the Petrol position.
When running on Petrol she idles nicely around 550 RPM.

IM getting a bit frustrated or confused now..because I thought the problem was definitely the push rods and lifters not properly set.

But now the concensus seems to be that it more likely a timing issue.

I've done a timing light test and it seems the dot or mark the notch on the pully or harmonic balancer is sitting well before the long white
line on idles with the vacuum advance blocked to the dizzy. and then when I move the lever to Petrol its past or advanced by about and inch or so.

I need to do some more reading and research to figure out where it should be.

Also one suggestion was to time on LPG at 2500 RPM ...er What does that mean?
Um rev to 2500 and turn the dizzy till the dot is in line with the line or 6 degrees advanced or what??/

Cheers

Ian

Ian it does seem as if your getting confused.

By the sounds of the engine running in your vids your pushrods are fine.

Ok time to explain timing.

The timing is the point at which the spark plug "sparks" to ignite the fuel mix.

At different revs the timing differs, less advance at idle (500 rpm), greater advance at working  speed (2500 - 3000 rpm)

Different fuels have different burning characteristics, Petrol is an explosive, quick burning fuel, were as LPG or gas is a slower burning fuel und thus they require different timing points.

Advance - the number of degrees before Top Dead Centre (TDC)

At idle the engine requires almost no advance.

In your case at working revs 2500- 3000 rpm 6 degrees befor TDC for Petrol and 12 degrees befor TDC .
  
There are two main types of auto advance systems - Mechanical and Vacuum.

Mechanical - Inside the dizzy there is a set of springs holding weights that are attached to a advance cam.
At low speed the springs are strong enough to hold the weights in and thus the advance cam is at its least position.
As the revs increase the centifugal force acting on the spinning weights gets greater forcing the weights out, this acts on the cam turning it and increasing the advance.
  
Vacuum - a rubber diaphram is connected to the advance cam by a lever, at low revs there is low vacuum in the inlet manifold and no energy to move the diaphram, so it stays at the least position, as the revs rise the vacuum pressure increases, sucking on one side of the fiaphram and movining the lever and advance cam.

Now to time your Van correctly.

Ensure that the TDC mark on the harmonic balancer lines up with the indicator when the engine is at TDC.

Ensure that the vacuum tube to the distributor is connected and working.

Run the engine on gas, with the lever in the gas position, set the engine revs to 2500 rpm and then ensure the 12 degrees befor TDC mark is in line with the indicator, if not move distributor till it is. once it is set right, set the idle to around 500 rpm or where it runs reasonably smoothly.

That should be it.

If you want to check the timing for Petrol, run the engine on Petrol with the lever in the petrol position, all being equal the 6 degree bfeor TDC mark should line up with the indicator. it should not require moving the dizzy - thats the idea of your dads lever.

Note that if the engine is timed at 2500 rpm then the idle speed advance should be close to the Zero dgrees before TDC.

Also when running on petrol ONLY have the lever in the Petrol position, and when running gas, only in the Gas position, don't mix them as this will adversly effect the timing and thus preformance.

Warren