Timing on rover V8

[walker]

Hopefully someone has had similar experience to this and let me know what is wrong.

I have just finished installing the 4.6l into the rangie. It is a fairly new block with the reconditioned heads from my 3.5 and a WW Stromberg carby.

With my old moter, it ran best when the timing was set with a huge advance (about 22 degrees BTDC) and there was no pinging. I thought it must have been something worn in the motor ie cam.

I have a new cam in this motor and again it will only run ok when far advanced. The main pulley is ok and the marks are right as I have already checked the TDC mark against the piston on #1.

My only guess is that there is something wrong with the distributor??? It is really the only comon link between the 2 motors. Both the mechanical & vacuum advance seem to work ok but there must be something badly wrong somewhere. Even though I have it set at 24 degrees I don;t actually believe it can be that high as surley the motor would not run...or at least ping.

Any ideas?

Also, is anyone running a 4.6l motor on carby's? I so what carby are you using? I have a feeling the WW is not letting enough air in!

[MacMan]

Sounds like there is something has skipped a tooth somewhere. 22 degrees is about 1/16 of a full rotation. Definitely suss!

[MacMan]

BTW, how are you measuring the advance since you'd be off the scale on the pulley?

[walker]

Really just estimating. I measured from 0 to 12 degrees and I was just under double that.

I was thinking also that it is roughly the degree of 1 tooth but I have no idea what is going on. I think I will take it down to the "ignition shop" and get them to check it and rebuild if necessary. It is running a "Luminition" electronic ignition system so I am wondering if that is stuffed up somewhere.

[PhilipA]

Have you actually checked the position of TDC vs the TDC mark on the pulley????
My first guess would be that is the problem.
I saw this recently and thought it was a cool idea.
Stuff some string into no 1 cylinder through the plugol.. I recommend string that will not break.
Turn the engine to push the piston up against the string. you may have to do it a few time s to compress it and get a consistent reading.
Then turn the engine backwards until the piston stops in the other direction.
Hopefully you have marked the first place on the harmonic balancer that it stopped. Mark the second place and midway between is TDC. Voila!!

I doubt that the engine would run consistently at 50% advance 24+30 as the rotor would probably not be to the contact in the dizzy then.
regards Philip A

[walker]

I did check TDC with a dial guage into #1 cylinder and it matched up perfect with the mark on the pulley.

[PhilipA]

IsThe distributor advancing and retarding as you rev the engine?? Have you checked with a timing light by revving to say 3000 and then back to idle?
I would think any engine would spit back on the starter with that much advance.
Once it happened to me that the mechanical advance was sticking on a Vdub I had. When I timed it it was Ok then it would advance up but not retard straight away and I would check the timing and it was 20plus. Sure this isn't what happened . Whack some oil down the spindle and check that the advance is moving freely.
regards Philip A

[DEFENDERZOOK]

<span style="color:blue">i wouldnt go spinning any engine backwards.....

they dont like it.....it rips ***** out of the timing chain tensioners.....


did you have the vaccuum advance disconnected when you adjusted the timing....?
do you know if both the mechanical and the vaccuum advance work....?

if your dizzy is out by one tooth its simply a matter of remove and refit in the correct
position....for best performance.....advance the timing out on the raod...
advance it till it pings then back it off a few degrees......
they used to always like running advanced....but you will lose a bit of low
down torque....
do you do more on road or off road driving.....?</span>

[walker]

Wow lots of questions there.

Phillip - With Vac advance disconnected, it does advance about 1/4 of a pulley when revved and it seems to come back to normal as the motor goes back to idle.


Yes I had vac advance disconnected when timing.

Moving the dizzy up or down a tooth does not change the actual degree it is advanced, only the position of the distributor. Which tooth you go in is usually determined by the vac advance mechanism as it limits rotation of the distributor. I have played around with different postitions.

I did advance it till it pinged, then backed it off about 4 degrees. It is now running ok but according to the pulley it is at 22 degrees BTDC. I could just say "stuff it" and leave it as it is (this is what I did with old motor) but with the new motor and all I would like to work out the problem.

It is a dedicated offroader, only driven a couple of times a month.

[PhilipA]

Well. it all sounds like there is nothing wrong.
I would drop it back to about 14 BTDC.
What happens if you do that?
You will not have much over 4000 anyway with a Stromberg I wouldn't think.
What about exhaust manifolds? what are you running, the old single outlet ones?
It may be that the distributor does not have enough total advance or that the springs are too strong and it is coming too late if it doesnt ping with 20plus degrees static. It could also be that the carby is very rich.
You are really just trading low down torque for revs by advancing so much.

A good dyno session would be in order to tell you what is happening. I reckon from what you say that you could pick up a LOT of power. A good operator could do timing swings at different revs to plot the best curve.

Maybe also try a vacuum gauge to see whether you have the cam mistimed.
There are instructions somewhere on the internet on how to read a gauge. someone on either this forum or teh Range Rover Disco one has posted on this.
Regards Philip A

[DEFENDERZOOK]

<span style="color:blue">you connect the vaccuum guage to the inlet manifold and adjust the timing
for maximum vaccuum.....



if it is only for off-road.....i would retard the timing a bit from where it is now...
this will give a bit more power in the lower rev range.....
where you need it most for off roading....

if its running right then just enjoy it.....dont stress over it.....
if the engine isnt happy with the timing it will let you know.....</span>

[walker]

Thanks both of you.

I have check the vacuum re the cam and it is fine.

If I drop the timing back to about 12-14 degrees then it just dies at anything over about 2500 RPM and is terrible to drive.

I was wondering if the Stronberg would be able to handle the 4.6. I have only had it on short runs around the block but when I pulled out the plug it was very very very sooty so it must be running rich. You are right, I really need to get it set up and tuned by a pro. I am running jets which I think are from a 4.4l but I dont even know that for sure. It may be that it cannot suck enough air at higher revs which is causing it to die although I thought that if this were the case no matter where I put the timing it would die at higher revs and that is not happening.

Since I have already spent the money reconditioning the rest of the engine, it is probably woth while getting the distributor reconditioned as well.

If it is the carby, then I am not sure what I will do. i have been very happy with the WW. Since I reversed the mounting it has been fantastic offroad

[PhilipA]

Look 4.6 is only 200CC or about 4% bigger than the Leyland. In other words the carby should have enough capacity for a 4.6, and it should go like a P76above 3000RPM, which was OK I think. Never driven on but I remember once haviong a dice with one in a 302 falcon and thinking it went well.

What cam did you put in? Was it a short duration towing cam?

It all depends I guess on what "fixes" have been done to the carby and distributor over the years.
maybe you should once again go back to basics
1 Is the choke going off
2 has the carby got full throttle plate opening with your foot flat to the floor
3 How many degrees advance are you getting. Should be 30total advance so mark this plus static on the balancer and check whether it is happening.

4Have you got too much or too little lifter preload. too much will cause pump up . Too little noise and valve not opening.

5 Is the cam lift compatable with valve collet to guide clearance . less than .430
6 What is the compression ratio. Did you use tin gaskets with 35 CC heads or composites. If composite and no head shave of 35 thou Min to 28CC chamber you have CR of mid sevens. Come to think of it this could cause your symptoms.
Regards Philip A

[walker]

Ok, we will do a bit more research today...if the cool change comes in https://www.aulro.com/afvb/

The cam is a standard 3.9 cam which I was told should be better for low down torque.

Heads were shaved when reconditioned and a composite gasket was used.

[barney]

i did a similar thing with a 4.0 litre block and 3.5 heads, inlet manifold, zenith carbys and even kept the original dizzy with the points. i have an electronic unit but something is wrong with it and it cuts power when the engine is laboured under 1200rpm.
i have a stage 1 cam from bruce davis performance landy's. my timing usually sits around 8 deg BTDC, standard it should be 5-7 deg BTDC. i set the dwell at around 24-26 deg. because of the cam, it idles a little lumpy and is herefore hard to get exactly right to the degree.
these settings are pretty much what they should be for a 3.5L.
as the others have said, you have either misaligned a tooth or maybe your dizzy is ****ed.
when the timing marks are lined up at TDC, the rotor in the dizzy should be pointing towards number 1 ignition lead on the cap.

[PhilipA]

I just had a thought.
Did you use exhaust manifold gaskets when you put the exhaust manifold on??

You know there are two ways that the gaskets go on, the right way and the wrong way. The wrong way covers half the exhaust manifold opening, so would give OK power down low but none up high.

Please do not be insulted , but sometimes it is just some simple thing. And someone else can come along with fresh eyes and see it.
Regards Philip A

[walker]

Thanks everyone for the help. I finally got it all fixed.

It was...........the mechanical advance mechanism. The pins which hold the weights were totaly worn and about to break off. I had the distributor fully reco'ed and now it runs perfect! https://www.aulro.com/afvb/ https://www.aulro.com/afvb/ https://www.aulro.com/afvb/ https://www.aulro.com/afvb/

It idles heaps better and accelerates great with no flat spots all the way to the limit.

Now I am a happy chappy. https://www.aulro.com/afvb/

Best thing is it was a cheap fix at $90

[PhilipA]

Well, you have to admit it was one of the guesses!!!!!
Regards Philip A

[walker]

It was...well done.

Since I really had no idea what was causing the problem and there were so many variables I decided it was a process of elimination and work out what WASN'T the problem

1. Marks on crankshaft pulley -checked against top of piston 1 - OK
2. Cam not aligned properly - checked agains valves - OK
3. problem with distibutor - Sent in for service - BINGO