valve seat recession or poorly set up gaps???
- Thread starter Pilkie
- Start date
Pilkie
Active Member
Harvey???
Am I right in thinking that if the valve gaps are too tight,"1-2 thou less than book figures",that it will affect the compression pressure??
ie!!
The valves are opening/shutting too quick and thus its not getting long enough shut to compress,and open to suck the mix in,to get the full benefit of compressing the mix for making the required bang?
Slower driving speed will be less affected than higher due to the speed everything is moving!
Dave
Am I right in thinking that if the valve gaps are too tight,"1-2 thou less than book figures",that it will affect the compression pressure??
ie!!
The valves are opening/shutting too quick and thus its not getting long enough shut to compress,and open to suck the mix in,to get the full benefit of compressing the mix for making the required bang?
Slower driving speed will be less affected than higher due to the speed everything is moving!
Dave
The smaller the gap, the longer the valves remain open, opening early, and closing late, but I doubt that you would notice anything on a compression test, but it must have an effect on performance, but quite how much of an effect is difficult to say. I'm going to get splinters sitting on this fence.......If you're talking about 1-2 thou below the minimum figures, then the inlets have the biggest percentage difference, but even then I'm not sure I'd be resetting just for one or two, only if they were all like it.
I assume you checked them after leaving the car standing overnight without running it before checking?
I assume you checked them after leaving the car standing overnight without running it before checking?
Pilkie
Active Member
Yep.
All checked stone cold and as per my figures listed earlier!
I double checked to be 100% sure.
Going to double double check all engine settings,and if nothing obvious comes to light,I will take the cam off this weekend and get the shims sorted,either with replacements or ground down by a few thou!
All checked stone cold and as per my figures listed earlier!
I double checked to be 100% sure.
Going to double double check all engine settings,and if nothing obvious comes to light,I will take the cam off this weekend and get the shims sorted,either with replacements or ground down by a few thou!
harveyp6 said:
The reason I suggested it is that when I first put my 2.25 petrol powered land rover back on the road, it had very little power and wouldn't go above 50mph, although it revved freely with no misfiring. On investigation I found the vacuum advance hose blocked, cleaned it out, and almost doubled the performance of the engine allowing it to pull motorway speeds quite happily in a wheezy old land rover.
Shortly before I swapped the v8 in, the fuel pump started to die, again, with a reduction of power at motorway speeds, but largely unnoticeable on normal road driving.
Pilkie
Active Member
Dizzy all seems to be working fine,but I now have another that I will refurb and try.
Fuel pumps valves were iffy after its lay up but ive rebuilt it,also I now have a new replacement to fit and try.
When standing it will not rev above 5000,,well only for a split second it goes to 5500 on initial flooring of the throttle,carb butterfly is opening fully.
It seems free enough on the revs up to that point though!!
Its as if a rev limiter kicks in!
Fuel pumps valves were iffy after its lay up but ive rebuilt it,also I now have a new replacement to fit and try.
When standing it will not rev above 5000,,well only for a split second it goes to 5500 on initial flooring of the throttle,carb butterfly is opening fully.
It seems free enough on the revs up to that point though!!
Its as if a rev limiter kicks in!
webmaster
New Member
I'm starting to support the ignition problem idea, either the advance or a points / condensor / coil issue. I remember my old chevette used to suffer badly if the points gap was out, I ended up using a dwell meter to get a more accurate setting. Might be worth swapping condensor and coil if you've got spares.
My old 2.2TC would happily rev right past the red line, up to about 7k, only really did it when doing timed 0-60 runs, and the points / timing needed adjusting afterwards, but you get the idea, dread to think what sort of damage I was doing !
My old 2.2TC would happily rev right past the red line, up to about 7k, only really did it when doing timed 0-60 runs, and the points / timing needed adjusting afterwards, but you get the idea, dread to think what sort of damage I was doing !
NickDunning
Active Member
pilkie said:chrisyork said:I take it the run up to Rugeley didn't improve Connor then, Dave?
Nope! It didnt get above 70 even downhill,nor coming back either!DaveHerns said:
Unfortunately Nick was busy, so he didnt get a chance to have a spin.
Wish I had - I (sadly) - am of the opinion there is nothing really wrong with the car - it's just a slow one.
Demetris
Well-Known Member
pilkie said:
That alone does not sound right.
Presuming that the tachometer is correct, it should easily take the needle off-scale when you floor the throttle in neutral.
Also remember that closed up tappets will quickly lead to burned out valves and seats, especially the exhaust ones.
Pilkie
Active Member
Right,,, little bit of an update.
When standing and revving gradually,the counter goes up evenly 1,2,3,4,5000rpm,but sticks at 5000rpm,although the engine clearly IS revving to beyond this point!!!
If you floor the throttle it goes up to just over 5500 then drops back to 5000,so I suspect the rev counter has a fault showing high revs.
I was gentle,ish!! :wink:
Back to the performance!!!
It seems quite good up to 50-60 then it starts to struggle!
I can only assume therefore that this is due to the valve gaps being tight,as lack of power is one of the faults given in the book for faulty gaps,it just doesnt say too loose or too tight!
Probably both cause it anyway!
If there is an electrical breakdown at higher loads in the cond,cap,rotor,coil,ballast,HT or plug lead,etc thats causing it,then I will swap them one by one with known good items this weekend to test,and see whats what!
When standing and revving gradually,the counter goes up evenly 1,2,3,4,5000rpm,but sticks at 5000rpm,although the engine clearly IS revving to beyond this point!!!
If you floor the throttle it goes up to just over 5500 then drops back to 5000,so I suspect the rev counter has a fault showing high revs.
I was gentle,ish!! :wink:
Back to the performance!!!
It seems quite good up to 50-60 then it starts to struggle!
I can only assume therefore that this is due to the valve gaps being tight,as lack of power is one of the faults given in the book for faulty gaps,it just doesnt say too loose or too tight!
Probably both cause it anyway!
If there is an electrical breakdown at higher loads in the cond,cap,rotor,coil,ballast,HT or plug lead,etc thats causing it,then I will swap them one by one with known good items this weekend to test,and see whats what!
webmaster
New Member
Both too tight and too lose will give reduced performance, if too lose then the valves won't open for long enough and won't allow enough air/fuel in or enough exhaust out, if they're too tight then they will be open too long and you won't get the full benefit out of the combustion.
NickDunning
Active Member
pilkie said:Right,,, little bit of an update.
When standing and revving gradually,the counter goes up evenly 1,2,3,4,5000rpm,but sticks at 5000rpm,although the engine clearly IS revving to beyond this point!!!
If you floor the throttle it goes up to just over 5500 then drops back to 5000,so I suspect the rev counter has a fault showing high revs.
I was gentle,ish!! :wink:
Back to the performance!!!
It seems quite good up to 50-60 then it starts to struggle!
Sounds pretty normal to me....I ran a 1972 2000 auto for eight years and it was wasn't very happy at all over 60mph.
Plus you hit the built-in vibration at 70mph - once through that though it would go up to about 80mph. But that's really no way to treat a lady.
My 2200 auto is quite a bit more flexible and will cruise at about 65-70mph if pushed. But you can still feel she's getting a bit stretched at speed.
Demetris
Well-Known Member
harveyp6 said:
Oh dear! :shock:
I did not actually mean that Dave should do that, but when he said he could not make it go over 5000 rpm, i presumed that he had floored the throttle pedal, in which case i would expect the engine to go over 6-7 K rpm.
SC autos are supposed to be able to reach 95 mph which cerresponds to almost 5000 rpm.
So, there is a lot to be expected.
I don't remember if somebody else mentioned it before, but are you sure that when the throttle pedal is at the end of its travel, the throttle is actually wide open?
Brian-Northampton
Administrator
Pilkie said:
Sorry Dave - you need to find your micrometer!
and when you take them out ... put them back in the same order, there is one thick one and one thin one. I forget which goes on the top/underneath, but do it as per the book.
Cheers,
Bri.