Hi,
I apologise in advance for this long post.
I have had my 1987 V8 90 for about 6 months now and I have been teaching myself some basic mechanics while trying to improve it a little. It did run seemingly ok to start with but not knowing this engine I had no 'norm' to compare it to.
Anyway, although I cannot see the engine number due to the exhaust manifold having a link bar which blocks being able to see the number on the engine, I am fairly certain it is a low compression V8, and is the original engine fitted to the 90, with SU carbs.
The first thing I did was buy a compression tester and tested each cylinder, results are below;
8: 120 7: 115
6: 120 5: 120
4: 125 3: 129
2: 124 1: 120
I do not know if these results are too low or not, however since they are all quite similar they should be ok? maybe?
Next I removed the pulsair system as it looked very rusty and research online suggests this will not cause any issues to pass an MOT. While doing this I also removed the huge airbox / filter and elbows, and fitted some cone air filters on to the carbs. I was not too sure what to do with the pipes that had connected to various bits - the one connected from inlet manifold to airbox, I have but a mini crankcase breather filter on after the flametrap. The other pipe that used to connect at one end to a large, metal flametrap like item, then on to the 'T-junction' just before the air inlet joining each carb elbow, and the other end went to a '2-1' flametrap (which connected to both the left rocker-cover and the left carb), now does not go anywhere (at the end where it used to connect to the T-junction.
So, my first question, could I just change the '2-1' flametrap for the left crankcase to a '1-1' smaller one, like there is for the right-hand rocker-cover? This way I could just remove this extra pipe and large metal flametrap like item.
The sparkplugs looked ok on the first check (although read on for why they don't now), and the HT leads look ok, along with the distributor looking clean inside albeit with a little white mark on each of the metal pegs inside the cap. So ignition system seems fine to me.
When I changed to cone air filters, I noticed one carb seemed to suck in more air than the other, so I bought a carb balancer (which turned out to be a very cheap, basic tool which gave roughly accurate readings), disconnected the carb linkage and balanced the carbs. Since I was doing this I decided to tweek the mixture screws because under very hard acceleration, there was a misfire occasionally and I thought this would fix it (it did).
After doing this and noticing performance improvements, I next decided to tweak the timing by turning the distributor. (Yes I know now that I should have done this before playing with the carbs) I noticed that I could gain a good performance gain by 'advancing' the timing a little, although I was careful that because I do not know what 'pinking' sounds like I had to be careful with this. Due to a noise being heard when the engine was cool and under load, I turned this back to roughly where it was originally. In fact, I actually 'retarded' it past the original point as that was what it took to quieten down the noise to a level I was comfortable with.
Around this time, I noticed the engine had got louder than when I first bought it, and actually seemed to have less power than I remembered. After looking around under the car with it running, I noticed there was a hole in one of the down-pipes from the left exhaust manifold. Looking at replacements online, I found that my manifolds are not standard, but mild steel versions of what look like 'sports' manifolds (i.e. they look like the stainless steel sports option manifolds but obviously not stainless). Not wanting to buy a complete exhaust at this time, I bought an exhaust repair kit and paste, which seems to have worked (although the 'nice' sound I used to enjoy the V8 make now isn't there and it sounds rather quiet and average!).
Now the car is a lot quieter, I can hear other bits clearer. Under hard acceleration at low-ish revs, there is a 'fluttering' noise similar to the noise that used to come from the manifold, but slightly different. I guessed it may be due to a rich fuel mixture so have turned this down a little, but this has made no difference.
I have tried the 'lifting the pistons in the carbs 1mm' and see if the engine revs go up or down, and although the revs do rise a little, I am reluctant to lean the mixture any more because I feel I am starting to lose power at mid - full throttle compared to where the mixture was before. Although I assumed the mixture was too rich, for example the idle when warm is much smoother, it almost seems that it is the correct mixture for idle, but too lean for pulling well under load.
Questions 2 and 3 are, what could I do to solve this? As a side note, I have tried pulling the choke out while driving / accelerating and this makes no difference. In fact, when the engine is fully warm and the car is sat idling, if I pull the choke out approx. 10mm, the revs rise to about 2000rpm, but if I pull the choke out any more, the revs drop and the engine stutters and does a similar sound to the flutter I mentioned earlier, but much worse (this is what led me to think it was running rich at full throttle, which now doesn't seem to be the case). Is this what is supposed to happen when you pull the throttle out with a warm engine?
The latest thing I have done is re-check the sparkplugs. These now look a little more 'sooty' on the circular part the 90 degree angle is attached to, but then quite white / cream on the tip near to the electrode. I can only assume this means I was running too rich and now running correctly, or maybe a little lean during my experimenting with the mixture. I have also noticed that there is wet oil on the sparkplugs, mainly the threads and sat in the little 'ridge' of the hole the plug goes into. There was a tiny amount of oil on a couple of the plugs the first time I removed them, however now there appears to be more oil than before. What could this be due to?
Another point I have noticed is, when driving around normal 'A-roads' and 'B-roads' (30-40mph in 5th gear, approx. cruising along at ~1000rpm), when the engine is warm with no choke, when I stop, it now idles reasonably smoothly at 750-800rpm. After a reasonable motorway run however, when coming to a stop shortly after, e.g. a slip-road to roundabout, the revs idle much higher around 1000-1100rpm, for about 30 seconds, then very slowly return to normal 800rpm ish. Any thoughts on this?
Any answers to my questions or any thoughts on any of the points mentioned would be very much appreciated. In case I haven't specifically mentioned, the power loss is in the form of, lack of acceleration unless setting the fuel mixture seemingly rich at idle, and that it loses speed going up hills unless again, I set the fuel potentially rich.
MC
I apologise in advance for this long post.
I have had my 1987 V8 90 for about 6 months now and I have been teaching myself some basic mechanics while trying to improve it a little. It did run seemingly ok to start with but not knowing this engine I had no 'norm' to compare it to.
Anyway, although I cannot see the engine number due to the exhaust manifold having a link bar which blocks being able to see the number on the engine, I am fairly certain it is a low compression V8, and is the original engine fitted to the 90, with SU carbs.
The first thing I did was buy a compression tester and tested each cylinder, results are below;
8: 120 7: 115
6: 120 5: 120
4: 125 3: 129
2: 124 1: 120
I do not know if these results are too low or not, however since they are all quite similar they should be ok? maybe?
Next I removed the pulsair system as it looked very rusty and research online suggests this will not cause any issues to pass an MOT. While doing this I also removed the huge airbox / filter and elbows, and fitted some cone air filters on to the carbs. I was not too sure what to do with the pipes that had connected to various bits - the one connected from inlet manifold to airbox, I have but a mini crankcase breather filter on after the flametrap. The other pipe that used to connect at one end to a large, metal flametrap like item, then on to the 'T-junction' just before the air inlet joining each carb elbow, and the other end went to a '2-1' flametrap (which connected to both the left rocker-cover and the left carb), now does not go anywhere (at the end where it used to connect to the T-junction.
So, my first question, could I just change the '2-1' flametrap for the left crankcase to a '1-1' smaller one, like there is for the right-hand rocker-cover? This way I could just remove this extra pipe and large metal flametrap like item.
The sparkplugs looked ok on the first check (although read on for why they don't now), and the HT leads look ok, along with the distributor looking clean inside albeit with a little white mark on each of the metal pegs inside the cap. So ignition system seems fine to me.
When I changed to cone air filters, I noticed one carb seemed to suck in more air than the other, so I bought a carb balancer (which turned out to be a very cheap, basic tool which gave roughly accurate readings), disconnected the carb linkage and balanced the carbs. Since I was doing this I decided to tweek the mixture screws because under very hard acceleration, there was a misfire occasionally and I thought this would fix it (it did).
After doing this and noticing performance improvements, I next decided to tweak the timing by turning the distributor. (Yes I know now that I should have done this before playing with the carbs) I noticed that I could gain a good performance gain by 'advancing' the timing a little, although I was careful that because I do not know what 'pinking' sounds like I had to be careful with this. Due to a noise being heard when the engine was cool and under load, I turned this back to roughly where it was originally. In fact, I actually 'retarded' it past the original point as that was what it took to quieten down the noise to a level I was comfortable with.
Around this time, I noticed the engine had got louder than when I first bought it, and actually seemed to have less power than I remembered. After looking around under the car with it running, I noticed there was a hole in one of the down-pipes from the left exhaust manifold. Looking at replacements online, I found that my manifolds are not standard, but mild steel versions of what look like 'sports' manifolds (i.e. they look like the stainless steel sports option manifolds but obviously not stainless). Not wanting to buy a complete exhaust at this time, I bought an exhaust repair kit and paste, which seems to have worked (although the 'nice' sound I used to enjoy the V8 make now isn't there and it sounds rather quiet and average!).
Now the car is a lot quieter, I can hear other bits clearer. Under hard acceleration at low-ish revs, there is a 'fluttering' noise similar to the noise that used to come from the manifold, but slightly different. I guessed it may be due to a rich fuel mixture so have turned this down a little, but this has made no difference.
I have tried the 'lifting the pistons in the carbs 1mm' and see if the engine revs go up or down, and although the revs do rise a little, I am reluctant to lean the mixture any more because I feel I am starting to lose power at mid - full throttle compared to where the mixture was before. Although I assumed the mixture was too rich, for example the idle when warm is much smoother, it almost seems that it is the correct mixture for idle, but too lean for pulling well under load.
Questions 2 and 3 are, what could I do to solve this? As a side note, I have tried pulling the choke out while driving / accelerating and this makes no difference. In fact, when the engine is fully warm and the car is sat idling, if I pull the choke out approx. 10mm, the revs rise to about 2000rpm, but if I pull the choke out any more, the revs drop and the engine stutters and does a similar sound to the flutter I mentioned earlier, but much worse (this is what led me to think it was running rich at full throttle, which now doesn't seem to be the case). Is this what is supposed to happen when you pull the throttle out with a warm engine?
The latest thing I have done is re-check the sparkplugs. These now look a little more 'sooty' on the circular part the 90 degree angle is attached to, but then quite white / cream on the tip near to the electrode. I can only assume this means I was running too rich and now running correctly, or maybe a little lean during my experimenting with the mixture. I have also noticed that there is wet oil on the sparkplugs, mainly the threads and sat in the little 'ridge' of the hole the plug goes into. There was a tiny amount of oil on a couple of the plugs the first time I removed them, however now there appears to be more oil than before. What could this be due to?
Another point I have noticed is, when driving around normal 'A-roads' and 'B-roads' (30-40mph in 5th gear, approx. cruising along at ~1000rpm), when the engine is warm with no choke, when I stop, it now idles reasonably smoothly at 750-800rpm. After a reasonable motorway run however, when coming to a stop shortly after, e.g. a slip-road to roundabout, the revs idle much higher around 1000-1100rpm, for about 30 seconds, then very slowly return to normal 800rpm ish. Any thoughts on this?
Any answers to my questions or any thoughts on any of the points mentioned would be very much appreciated. In case I haven't specifically mentioned, the power loss is in the form of, lack of acceleration unless setting the fuel mixture seemingly rich at idle, and that it loses speed going up hills unless again, I set the fuel potentially rich.
MC
