Rover V8 with no pulling power!

[wee_arthur]

Hi there,

After getting our project running we have found that our genuine 3.5 v8 defender has no grunt behind it and a very slight misfire which we think is the problem.

When rebuilding and cleaning the engine we removed all the air recirculation system as there was already holes in it. So with all this gone we found today we had blocked up the two ports on top of the carbs. So with these unblocked the engine runs better. But in third sitting in the low rev range it just cannot pull away with the foot to the floor. (not the way we thought a v8 would be)

So my request is can anyone think of any critical pipe etc that we have maybe "misplaced"?

The Leads have been replaced along with the plugs and the rotor arm and distributer cap.

So any ideas ?

Thanks for reading

[wee_arthur]

Just realised im talking about the pulsair system with the pipes that loop from the air intake to the exhaust manifold. Will these have any effect if removed and plugged?

[Quagmire]

I have no experience of the pulsair system so cannot say what effect it has on performance exactly- its job is just to clean up unburnt hydrocarbons for emissions.

All i know is that plenty of people block them off with no problems.

When you took the engine apart, was the cam ok? A flat cam will give low power.

For perspective, my 3.5 which has 20k miles on it since i rebuilt (new cam, followers, rings etc) will pull away from stationary in 5th. Its a struggle, but it will do it - i wouldnt recommend it though as it cant be good for clutch etc!

How many miles has it done?

[reb78]

Have you checked the timing with a light?

[wee_arthur]

Sorry, the engine was not stripped just cleaned from the outside (via old steamy) and we removed the system and blanked the holes off, So we have not seen the cam but before it was taken out it was running okayish but the grunt was definately there.

We havent touched timings either since it was in the old truck, would this help?

Do you think the engine would need retuned after removing the pulse air system?

And also there is a small pipe from the block on which the carbs sit. We blocked it up to save dirt getting in and the removal of this has made the engine run smoother but not perfect, I have realised that this pipe is sucking air in constantly at quite a rate. i.e. i can hear it sucking beneath the bonnet is this normal?

Sorry for all the questions just a bit gutted we dont have that burble of a rover under the hood yet

thanks again

[reb78]

Did you get all of the water out after washing? I reckon douse anything electrical in WD40 and make sure all of the water is gone. Like you say, if timing hasnt been touched, not sure that would have caused it (unless you have been fiddling with the distributor during the re-build)

[moore101]

And also there is a small pipe from the block on which the carbs sit.

is this not the pipe for the vacuum advance on the distributor? could you get a picture of said pipe as as far as i know the only air that should be sucked in is through filters

[cackshifter]

If it's on SUs might be worth checking the pistons are free, and the dashpots are full of something thin like ATF not EP140. Should be able to feel with the lifting pin, without having to strip anything. If they aren't that'll limit the air that can get in.

Nigel

[wee_arthur]

If it's on SUs might be worth checking the pistons are free, and the dashpots are full of something thin like ATF not EP140. Should be able to feel with the lifting pin, without having to strip anything. If they aren't that'll limit the air that can get in.

Nigel

would this cause a large suction from the pipe?

Will get pictures of the pipe in question this afternoon.

[mickeyw]

would this cause a large suction from the pipe?

Will get pictures of the pipe in question this afternoon.

If it is a pipe approx 3mm dia bore that faces forward at the centre of the inlet manifold, between the carbs, it is indeed the vacuum advance pipe. This should be sucking air, but it should be connected to the distributor. Without this you have no vacuum timing advance and this will cause a distinct slugishness.

[wee_arthur]

If it is a pipe approx 3mm dia bore that faces forward at the centre of the inlet manifold, between the carbs, it is indeed the vacuum advance pipe. This should be sucking air, but it should be connected to the distributor. Without this you have no vacuum timing advance and this will cause a distinct slugishness.

great sounds like the problem . where abouts on the distributer does it connect ?

thanks i think the end is near.

[cackshifter]

I'd beware of premature elation, vacuum advance doesn't normally have a huge effect on much except fuel consumption, after all with the throttle wide open there is no vacuum much, and the pipe to the distributor is so small that an air leak through it doesn't hugely affect things, especially with a v8 sucking once it gets going. It's really just there to provide some advance at part throttle, to eke out oil supplies a bit further. Sounds like if it is pulling air from somewhere and bypassing the carbs enough to stop it pulling you have a much bigger leak than vac advance.

Nigel

[wee_arthur]

okay iv just been out and had a look, i think we have put the pipes in the wrong way so iv taken some photos.

Any chance you can tell me where these go by the numbers? :

Thanks

[cackshifter]

Sorry I can't tell you from that- it's maybe 30 years since I messed with Strombergs and I'm just no longer that familiar. It does look like those pipes are going to take air into the inlet manifold, they're either for breathers or vac advance so I can't see blocking the stubs is going to hurt in the short term. It sounds like something bigger of a problem if it wont't set off in low 3rd - were talking about a rover v8 here. The remarks about the SU pistons apply to Strombergs, though - they are very similar. I'd go back to basics. Check the ign timing with a strobe & check the centrifugal advance is working ish when you give it a rev - you should see the timing marks move as the speed changes (paint with tippex). If it all seems OK it's got to be either shortage of air or fuel. The fuel's dependent on air htrough the carbs, so I'd block those holes pro tem, and take off the air cleaner and make sure the pistons on the carbs are free & when you blip the throttle the pistons lift smartly. If so, maybe you have a fuel shortage - blockage, duff pump, pump sucking air? I do have a Rr manual. According to that those hoses from the carb should go to each rocker cover via a flame trap. The air cleaner should feed the valley via a flame trap so fumes are drawn through the engine.

Nigel

[moore101]

1 & 2 can both be blocked off each with a short length of pipe and a bolt all jubilee clipped together. have heard that connected the 2 together can help with balancing but i blocked mine up and they ran fine. you can get propper blockage caps but i dont know where from.

3 is one im not familiar with, does it suck air when running? where have you got it connected to?

4 is the one that needs to go to the vacuum unit on the side of the distributor (the small flying saucer object, has a place on the side for it to attach)

5 i blocked up with a machine screw and a bit of gasket sealer, cant remember what its use is for, another vacuum controlled device maybe.

can get some pics of some plumbed in carbs if your still stuck but my strombergs are in the shed somewhere

[wee_arthur]

hi thanks,

i currently have 3 and 5 connected to the advance as these are the only two pipes that suck air. No. 3 goes through what looks like a small restrictor (in photo) and to the underside of the passenger side carb.

There are two outlets on the vacuum advance. Anyone know if there is a difference or if one is a breather etc.

Thanks again