Distributer vacuum tube missing...?
Discussion
Not really, but there is a point where the advance curve defined by the bob weights and springs in the distributor (the centrifugal advance curve) will no longer be appropriate. If you have an electronic system the first thing you do is to tune the set-up but with a distributor this is more tricky and in most cases not changed. I'll leave to those with more knowledge how much tuning gets you to a point where this is critical. I suspect it is just easier to not try to fiddle with the internals of the distributor and simply to disconnect the vacuum advance to allow more static advance to be used. As said though will wait for those more experienced to comment at what point this is significant.
Rob_the_Sparky said:
Not really, but there is a point where the advance curve defined by the bob weights and springs in the distributor (the centrifugal advance curve) will no longer be appropriate. If you have an electronic system the first thing you do is to tune the set-up but with a distributor this is more tricky and in most cases not changed. I'll leave to those with more knowledge how much tuning gets you to a point where this is critical. I suspect it is just easier to not try to fiddle with the internals of the distributor and simply to disconnect the vacuum advance to allow more static advance to be used. As said though will wait for those more experienced to comment at what point this is significant.
I had a word with my TVR guy yesterday, I'm taking the car to him when it's time for its next service, he's going to check the ECU to see if anythings been changed, and either leave alone, or reconnect the hose if necessary. That's really the bottom line on this whole thing, as it's becoming even more boring than watching paint dry.The car runs smoothly, no shunting, and feels fine to me, that's not bad for an 82,000 car.
I'm enjoying it and that's the main thing, I wasn't even aware of this hose until someone pointed it out and ruined my day...
Edited by griff59 on Friday 20th July 09:20
Belle427 said:
The vacuum advance canister had failed in mine so wasn’t working. God knows how long it was being driven around like that but the car ran and does run perfectly well without it.
Don’t worry about it, just enjoy the car.
I agree with you, I know a lot of folks have given very detailed arguments for using the hose, but TBQH, 99% of who I've actually spoken to in the flesh, mechanics, club members have expressed your opinion. I'm not saying advocates of using the hose are wrong, but they seem in a monitory, I think in this context it's a "personal opinion" rather than a "right or wrong fact"Don’t worry about it, just enjoy the car.
My mechanic has told me not to connect the hose until he's had a look at my ECU, as it may have been set-up to run without the hose, I'll do that at the cars next service, and not before, it's just not worth it.
Edited by griff59 on Wednesday 25th July 18:51
Edited by griff59 on Wednesday 25th July 18:53
griff59 said:
I agree with you, I know a lot of folks have given very detailed arguments for using the hose, but TBQH, 99% of who I've actually spoken to in the flesh, mechanics, club members have expressed your opinion. I'm not saying advocates of using the hose are wrong, but they seem in a monitory, I think in this context it's a "personal opinion" rather than a "right or wrong fact"
My mechanic has told me not to connect the hose until he's had a look at my ECU, as it may have been set-up to run without the hose, I'll do that at the cars next service, and not before, it's just not worth it.
I have recently replaced it and gone over to the full vacuum method discussed on here.My mechanic has told me not to connect the hose until he's had a look at my ECU, as it may have been set-up to run without the hose, I'll do that at the cars next service, and not before, it's just not worth it.
Edited by griff59 on Wednesday 25th July 18:51
Edited by griff59 on Wednesday 25th July 18:53
Just giving you an example, I bet it does not work on a lot of cars.
Belle427 said:
I have recently replaced it and gone over to the full vacuum method discussed on here.
Just giving you an example, I bet it does not work on a lot of cars.
Have you noticed any improvement? Just giving you an example, I bet it does not work on a lot of cars.
I have also swapped over to it but haven't had a chance to give it a good test yet.
Why do you think it won't work on a lot of cars?
chris212 said:
Have you noticed any improvement?
I have also swapped over to it but haven't had a chance to give it a good test yet.
Why do you think it won't work on a lot of cars?
Sorry i meant the original vacuum advance cannisters probably dont work or have failed.I have also swapped over to it but haven't had a chance to give it a good test yet.
Why do you think it won't work on a lot of cars?
Ive noticed improved low speed driveability, better mpg and cooler running temps since switching.
RogerDodger said:
This is way too funny. "personal opinion" - it's how vacuum advance works - 100% fact :-)
OK, but it's still a marginal, or a case of "no" improvement on some people's cars, connected or disconnected. I could book my car in to my local TVR mechanic, and get him to fit the hose, and set up the timing, I could drive away after paying the bill with no discernible difference, and if there is a difference it probably won't be in proportion to the amount my bill came to.
Next service, that's when I'll ask him to connect the pipe, I'll keep you all posted as to the results, I'm sure they'll make headline news.
griff59 said:
RogerDodger said:
This is way too funny. "personal opinion" - it's how vacuum advance works - 100% fact :-)
OK, but it's still a marginal, or a case of "no" improvement on some people's cars, connected or disconnected.
The benefits of advancing timing when a spark ignition internal combustion engine is in light load cruise is one of the fundamental basic lessons of ignition timing. The benefits were discovered at the dawn of internal combustion engine development well over 100 years ago, so vehicles were fitted with a advance/retard lever where the driver was able to adjust the timing manually.
As ignition systems developed this feature became automated, designers used the happy coincidence that vacuum on the engine side of the throttle butterfly increased considerably when the engine was in cruise conditions to operate a device that advanced the timing, this device known as the vacuum advance unit worked so well it became standard on all distributors from the late 1940's/early 1950's.
However, apparently the old Rover V8 fitted to a small volume fiberglass bodied sports car built in a shed in Blackpool managed to break all the rules of internal combustion engines and 100 years of learning on the subject of ignition timing. Really clever TVR mechanics who obviously know better than the people who designed the distributor and vacuum advance unit discovered they could make this revolutionary and innovative car drive so much better and make masses more power by disconnecting the vacuum advance pipe.
While this act completely flys in the face of everything known and learnt about ignition timing up to that point, it was quite clear the people disconnecting the vacuum advance knew better, this was probably because the Rover V8 fitted to those low volume plastic sports cars was a unique and revolutionary engine that broke new ground and at the same time broke all the accepted rules of ignition timing learnt 100 years before.
Disconnecting the vacuum advance pipe became a tuning black art secret, the people doing it generally didn't like to share their amazing discovery, others spotted it and copied the practice smug in the knowledge they'd discovered the holy grail of engine tuning. I have so much respect for the geniuses who came up with this amazing discovery, flying in the face of overwhelming evidenced fact they pressed on with their seemingly illogical practice of disconnecting the vacuum advance unit and their reward was incredible performance gains.
But Shhhhhh, dont tell everyone... or they'll all be disconnecting their vacuum advance units, this is our little brilliant engine tuning secret that only really works so well because the Rover V8 engine fitted to Chimaeras and Griffiths is such a revolutionary power plant that breaks all the well understood and totally accepted rules in ignition timing on a spark ignition internal combustion engine.
Lets keep the secret to ourselves
What a load of old bolax
This site is here to share information and help eachother out.
The evidence for the vacuum pipe is overwhelming and 100% correct.
Having a big cam throws a spanner in the works but removing the advance is a very crude way to achieve,,, less timing advance, poor economy etc etc.
You have a chap here who has taken the time to explain and detail what are the facts.
It’s important for other owners that these threads contain facts rather than hear say.
99% of cars would have been fitted with the pipe, that tells it’s own story.
Mine and a few other 450 cars of similar age 2000 onwards so the last made all have the pipe.
Was it simply a way for someone to help the 5.0 with heafty cam to run slightly better and then became a tuning mod
I never considered any of this detail much until I had the joy of an after market Ecu or what is normally called a sports Ecu.
Rapid Ignition advance or retard as where it’s necessary is a revelation in comparison to the distributor anyway so dumbing down this even more by removing the vac pipe doesn’t sound like progress.
If your read up about how these timing changes effect cam over lap and how an engine actually works you’ll soon see that infact to gain economy when in cruise mode you want cylinders containing some exhaust gases etc simply to restrict how much fuel and air will be drawn in. So when you are going down hill or wind behind you the timing advances so reducing power effectively but your on a light throttle so don’t need the power but do want the pistons passing over top dead centre with less compression via slightly open valves which is what happens and creates less engine resistance because of it. It’s actually mainly the gases still in the cylinder from the last firing stroke that restrict how much space is available for fuel and air and this valve timing use is how it’s done to maximise mpg and power when needed
Restricting your timing curve will not be doing good things internally to your engine I believe.
On an occasional fun car it’s hardly the biggest issue to have but prolonged use would surely cost a fortune in petrol and oil changes alone.
The evidence for the vacuum pipe is overwhelming and 100% correct.
Having a big cam throws a spanner in the works but removing the advance is a very crude way to achieve,,, less timing advance, poor economy etc etc.
You have a chap here who has taken the time to explain and detail what are the facts.
It’s important for other owners that these threads contain facts rather than hear say.
99% of cars would have been fitted with the pipe, that tells it’s own story.
Mine and a few other 450 cars of similar age 2000 onwards so the last made all have the pipe.
Was it simply a way for someone to help the 5.0 with heafty cam to run slightly better and then became a tuning mod
I never considered any of this detail much until I had the joy of an after market Ecu or what is normally called a sports Ecu.
Rapid Ignition advance or retard as where it’s necessary is a revelation in comparison to the distributor anyway so dumbing down this even more by removing the vac pipe doesn’t sound like progress.
If your read up about how these timing changes effect cam over lap and how an engine actually works you’ll soon see that infact to gain economy when in cruise mode you want cylinders containing some exhaust gases etc simply to restrict how much fuel and air will be drawn in. So when you are going down hill or wind behind you the timing advances so reducing power effectively but your on a light throttle so don’t need the power but do want the pistons passing over top dead centre with less compression via slightly open valves which is what happens and creates less engine resistance because of it. It’s actually mainly the gases still in the cylinder from the last firing stroke that restrict how much space is available for fuel and air and this valve timing use is how it’s done to maximise mpg and power when needed
Restricting your timing curve will not be doing good things internally to your engine I believe.
On an occasional fun car it’s hardly the biggest issue to have but prolonged use would surely cost a fortune in petrol and oil changes alone.
I've noticed an improvement since going manifold vacuum. The shunting has virtually gone.
As instructed by ConG, I ran a t-shirt piece from the fuel regulator and used the original pipe with the one way valve to the advance. Checked the timing and that was it.
I've suffered shunting since I've had it (8 years) and this is the best improvement towards eradicating it. With the vac advance disconnected, its as it was ( shunting).
Mine is a 4.3 precat.
As instructed by ConG, I ran a t-shirt piece from the fuel regulator and used the original pipe with the one way valve to the advance. Checked the timing and that was it.
I've suffered shunting since I've had it (8 years) and this is the best improvement towards eradicating it. With the vac advance disconnected, its as it was ( shunting).
Mine is a 4.3 precat.
chris212 said:
I've noticed an improvement since going manifold vacuum. The shunting has virtually gone.
As instructed by ConG, I ran a t-shirt piece from the fuel regulator and used the original pipe with the one way valve to the advance. Checked the timing and that was it.
I've suffered shunting since I've had it (8 years) and this is the best improvement towards eradicating it. With the vac advance disconnected, its as it was ( shunting).
Mine is a 4.3 precat.
Great stuff Chris, I assume you mean T-Piece not T-Shirt and the one way valve you're using is actually a vacuum delay valve like this?As instructed by ConG, I ran a t-shirt piece from the fuel regulator and used the original pipe with the one way valve to the advance. Checked the timing and that was it.
I've suffered shunting since I've had it (8 years) and this is the best improvement towards eradicating it. With the vac advance disconnected, its as it was ( shunting).
Mine is a 4.3 precat.
You wouldn't want a one way valve as it would hold your timing advanced which would be engine damaging dangerous!
Good results though, you're now in the ever increasing group that are seeing real benefits from switching to full vacuum
Predictive text! ( May get the t- shirt though!)
I've sucked as hard as I can on the damper and there's no way anything can get through the other way, unless it's very high pressure rated? Maybe it's faulty and I should do without it?
I've got it the wrong way around if you follow the "carb" and "dist" orientation, as I can't see how it can draw any vacuum the correct way?
I've sucked as hard as I can on the damper and there's no way anything can get through the other way, unless it's very high pressure rated? Maybe it's faulty and I should do without it?
I've got it the wrong way around if you follow the "carb" and "dist" orientation, as I can't see how it can draw any vacuum the correct way?
chris212 said:
Predictive text! ( May get the t- shirt though!)
chris212 said:
I've sucked as hard as I can on the damper and there's no way anything can get through the other way, unless it's very high pressure rated? Maybe it's faulty and I should do without it? I've got it the wrong way around if you follow the "carb" and "dist" orientation, as I can't see how it can draw any vacuum the correct way?
You shouldn't really need a vacuum delay valve with a full vacuum signal, unlike a ported vacuum signal that can fluctuate as the throttle butterfly passes over the port a full manifold vacuum signal applied to the vac advance unit should be significantly more stable and consistent.This is especially true at small throttle openings where ported vacuum can give on/off spikes in vacuum and so rapid undesirable changes in ignition timing which potentially will make the engine shunt.
chris212 said:
I've noticed an improvement since going manifold vacuum. The shunting has virtually gone, I've suffered shunting since I've had it (8 years) and this is the best improvement towards eradicating it.
As an experiment try it now with the vacuum delay valve removed and see if the improvement remains, which I suspect it will.OK, I said that I've now got the hose, can someone please tell me if it's just a matter of going out to the garage and connecting it? or, do I have to get the engine timing checked as well? The reason im asking this again is that I'm not capable of timing the engine myself, I'd have to take the car in to have it done.
Belle427 said:
You should get it checked but in reality it probably won’t make a huge difference by reconnecting it yourself.
The issue is that it could cause detonation/pinking which is almost impossible to hear on these engines and is a bad thing if left like this.
Yet another reply that confirms my doubts about this whole thing. It's like having the ever so slightly cracked sound board replaced in my grand piano just because an expert said it would make a huge difference to the way the instrument sounded, and played, even though it sounds great and plays superbly to me. I've had a few piano technicians around and all gave conflicting opinions, the last guy said if it plays well and if you like the sound leave well alone, I'm adopting the same attitude with my Griff. The issue is that it could cause detonation/pinking which is almost impossible to hear on these engines and is a bad thing if left like this.
Gassing Station | Griffith | Top of Page | What's New | My Stuff