Looking for Guru who can interpret Vacuum readings...
Discussion
Normally I can find the answer for just about anything car related on the internet but I can't seem to get any positive direction for this vacuum reading..
you can see it at https://vimeo.com/244265209
It's a stock v6, running points, everything is new. No leaks anywhere on manifold. It runs great sometimes, but always starts spitting at some point. No consistency.
Cheers!
you can see it at https://vimeo.com/244265209
It's a stock v6, running points, everything is new. No leaks anywhere on manifold. It runs great sometimes, but always starts spitting at some point. No consistency.
Cheers!
If the valve guides were worn that badly, there would be a fair bit of oil smoke surely?
Could you have some sticking valve(s)?
It sounds as though this is fresh engine, and it's not inconceivable you could have some sticking valves.
It's difficult to tell from your video if the engine is misfiring.
How is the idle mixture?
If you hold the revs at about 1500 - 2000 rpm, what happens to the gauge then?
EDIT: Are the valve clearances 100%?
Could you have some sticking valve(s)?
It sounds as though this is fresh engine, and it's not inconceivable you could have some sticking valves.
It's difficult to tell from your video if the engine is misfiring.
How is the idle mixture?
If you hold the revs at about 1500 - 2000 rpm, what happens to the gauge then?
EDIT: Are the valve clearances 100%?
Edited by TonyRPH on Saturday 2nd December 22:40
Thanks for the responses.
I've adjusted the valves by the book a few times. But I'm not certain about them.
I hear clacking when it's cold, and it seems to run better...after heating up, the clacking is less and it runs like crap.
The vacuum gauge will stabilize a little bit after revving it up to higher RPM.
I may have to try to adjust the valves while they're running which is really hard to do...
I've adjusted the valves by the book a few times. But I'm not certain about them.
I hear clacking when it's cold, and it seems to run better...after heating up, the clacking is less and it runs like crap.
The vacuum gauge will stabilize a little bit after revving it up to higher RPM.
I may have to try to adjust the valves while they're running which is really hard to do...
If I'm reading that correctly, it's just fluttering but with negative pressure (i.e. vacuum) all the time, which is exactly what I would expect. If you were to put an orifice-restricting damper in the line, it may smooth out the pulsing - the gauges I use for balancing my TBs have a little screw-restrictor in each line for this reason.
It would be more concerning if the gauge was fluctuating into positive pressure, as this could indicate a valve not seating/clearance too tight.
You may possibly have just embarked on your first bit of engine education and seen the actual effect of cam timing and rpm - as the inlet remains open after BDC to allow for better cylinder-filling at higher rpm, this results in fluctuating vacuum at low rpm as the ingoing flow is temporarily reversed because of low velocity.
Spitting back is another matter, often caused by weak mixture or ignition-related faults.
Why would you want to adjust the valve clearances with the engine running, BTW?
It would be more concerning if the gauge was fluctuating into positive pressure, as this could indicate a valve not seating/clearance too tight.
You may possibly have just embarked on your first bit of engine education and seen the actual effect of cam timing and rpm - as the inlet remains open after BDC to allow for better cylinder-filling at higher rpm, this results in fluctuating vacuum at low rpm as the ingoing flow is temporarily reversed because of low velocity.
Spitting back is another matter, often caused by weak mixture or ignition-related faults.
Why would you want to adjust the valve clearances with the engine running, BTW?
foursix said:
It runs great sometimes, but always starts spitting at some point. No consistency.
The vacuum gauge show what you'd expect for an undamped, unrestricted gauge. The spitting doesn't sound right, though, and you might want to go into a bit more detail about what's going on there.trickywoo said:
Bonkers. If you do though get someone to video it and post it up, it’d be great to watch.
Steve_D said:
foursix said:
....I may have to try to adjust the valves while they're running which is really hard to do...
A very good technique for destroying a perfectly good set of feelers.Steve
Thanks for the inputs...there seems to be more knowledge here than in some of the land cruiser enthusiast forums...
Edited by foursix on Sunday 3rd December 19:24
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