Modified crossflow - poor cold start, holds back when warm
Discussion
Got a 1600 xflow in my mk2, with modded head, l&b flywheel, vernier etc. and a road/rally cam (Burton). Local rolling road has tried getting it running on a 32/36 and also a set of bike carbs but it is a complete b
d to start from cold, and seems to hold back a lot with no power below 3000rpm when warm. Ignition is a vacuum-less dizzy from Bestek, with a curve for twin 40s.
Obviously pretty gutted that it's not running properly! The garage is wanting to check the cam timing but also suggesting a lot of 'breathing' - would either of these cause the cold start problems? Doesn't seem to be any oil burned when driving. My other thought is whether it is worth trying a different distributor?
Any help would be appreciated guys, I am getting really pissed off trying to get this sorted and it's costing a bloody fortune!
d to start from cold, and seems to hold back a lot with no power below 3000rpm when warm. Ignition is a vacuum-less dizzy from Bestek, with a curve for twin 40s.Obviously pretty gutted that it's not running properly! The garage is wanting to check the cam timing but also suggesting a lot of 'breathing' - would either of these cause the cold start problems? Doesn't seem to be any oil burned when driving. My other thought is whether it is worth trying a different distributor?
Any help would be appreciated guys, I am getting really pissed off trying to get this sorted and it's costing a bloody fortune!
It's a modified engine with a hot cam with a 3000 to 7500 powerband running on carbs, it's going to be a bit pants at low revs. Get some decent carbs on there (bike carbs should work but may be tricky to set up, but I imagine the 40s the ignition is set up for will work well) and rev the nuts off it.
davepoth said:
It's a modified engine with a hot cam with a 3000 to 7500 powerband running on carbs, it's going to be a bit pants at low revs. Get some decent carbs on there (bike carbs should work but may be tricky to set up, but I imagine the 40s the ignition is set up for will work well) and rev the nuts off it.
I was just trying to find the powerband on Burton's website but unless I've missed it, I can't find it written down (think it's an A2 cam). Not too worried if it means revving to 3000+ to get it going, just want to cure the cold starting issue as it's bloody embarassing to have to turn it over 10 or more times before it'll run.Would a vacuum distributor make any difference?
A2 is not too bad a cam. I would guesstimate at needing more enrichment on start up. Have you a choke of some discription ? .Unfortunately running carbs and distributors are more problematic than injection enrichment and variable timing from an ecu, which we are blessed with on newer engines. Has the timing been set up for maximum power, because even a 'modded ' curve using spring weights is harder to set up for both sensible running and max power.
When the 32/36 was in, I discovered the choke cable hadn't been connected up properly but as I knew it was getting the bike carb conversion it wasn't really a problem. Since the conversion I haven't driven it but I was there when they first tried to start it - without success.
I believe there is the facility to have the manual choke cable connected but have to assume for the time being, that they have tried this.
Not sure how far they have got with setting it up but again have to assume it has been on the rollers with no joy. My gut feeling is that the distributor is the issue, and keeping my fingers crossed the engine isn't lacking compression. The lad I bought it off seems genuine enough and said when he inspected it the pistons/rings (?) looked in good order.
I believe there is the facility to have the manual choke cable connected but have to assume for the time being, that they have tried this.
Not sure how far they have got with setting it up but again have to assume it has been on the rollers with no joy. My gut feeling is that the distributor is the issue, and keeping my fingers crossed the engine isn't lacking compression. The lad I bought it off seems genuine enough and said when he inspected it the pistons/rings (?) looked in good order.
Edited by PigFilth on Monday 14th March 22:24
I have a 1660cc x-flow, with a BCF2 cam (medium fast road).
The x-flow was never a great starter at the best of times, especially when the oil was stone cold (as it has been the past few months). If everything is set up properly and the battery's charged 100% then it'll start at the first attempt, but if the timing is off, or the carb's not quite set up properly, then all bets are off.
Fitting a manual choke to the carb will help a lot, as the 32/36 auto choke was always unreliable. I got a kit from my local motor factors - took about an hour to install. My engine now has bike carbs, which have given me far more power at lower revs, and far easier starting. They look good, too!
I would recommend fitting Megajolt Lite ignition from http://www.autosportlabs.net/Main_Page - this is an easy-to-fit electronic ignition that uses the EDIS ignition components from later Fords. The benefit is that I have set the ignition advance for cranking to a low value, which makes life easier for the starter motor. It gives a big fat spark at all revs, which also helps with starting. Another benefit is that you can take the distributor away, and give yourself much more room for the bike carbs! There is some work to install it - you have to fit a VR sensor, and either a throttle position sensor (TPS) or a manifold air pressure (MAP) sensor. You will also need a laptop to program it.
Also, as I mentioned above, the battery needs to be at 100% charge to have a fair chance of starting first time. When the car's not in use it is connected through the lighter socket to an Optimate maintenance charger, so the battery's fit even after a long period out of use.
The x-flow was never a great starter at the best of times, especially when the oil was stone cold (as it has been the past few months). If everything is set up properly and the battery's charged 100% then it'll start at the first attempt, but if the timing is off, or the carb's not quite set up properly, then all bets are off.
Fitting a manual choke to the carb will help a lot, as the 32/36 auto choke was always unreliable. I got a kit from my local motor factors - took about an hour to install. My engine now has bike carbs, which have given me far more power at lower revs, and far easier starting. They look good, too!
I would recommend fitting Megajolt Lite ignition from http://www.autosportlabs.net/Main_Page - this is an easy-to-fit electronic ignition that uses the EDIS ignition components from later Fords. The benefit is that I have set the ignition advance for cranking to a low value, which makes life easier for the starter motor. It gives a big fat spark at all revs, which also helps with starting. Another benefit is that you can take the distributor away, and give yourself much more room for the bike carbs! There is some work to install it - you have to fit a VR sensor, and either a throttle position sensor (TPS) or a manifold air pressure (MAP) sensor. You will also need a laptop to program it.
Also, as I mentioned above, the battery needs to be at 100% charge to have a fair chance of starting first time. When the car's not in use it is connected through the lighter socket to an Optimate maintenance charger, so the battery's fit even after a long period out of use.
Edited by Jerkins on Tuesday 15th March 08:35
PigFilth said:
Not quite that simple I'm afraid, without incurring a huge amount of extra cost.
I am not bothered about the cam, but want the thing to start properly!
Is it turning over quickly, or does it sound sluggish and does the starter stall occasionally? If so then you may well have too much static advance, which would be easy to prove by backing it off a good bit. A geared starter (e.g. Brise) will also help spin it over quickly. I am not bothered about the cam, but want the thing to start properly!
I'd also recommend ditching the clockwork ignition and going for a mapped system, it can make a significant improvement on an engine with 'big' cams as you can program the advance curve you need, rather than a very rough approximation. You can also add a throttle position sensor to get a 3D map, which will help fuel economy.
Thanks for the advice, very useful.
The battery had been losing charge quite a bit over the winter, to the extent that I had had to keep charging it up. However, when it first came back from the garage with the 32/36 it seemed to have been charged OK. The starter seems to turn a few times and then make the usual weird noise, necessitating another twist of the key.
I'm hoping to call at the garage this afternoon to see what they've found.
Cheers.
The battery had been losing charge quite a bit over the winter, to the extent that I had had to keep charging it up. However, when it first came back from the garage with the 32/36 it seemed to have been charged OK. The starter seems to turn a few times and then make the usual weird noise, necessitating another twist of the key.
I'm hoping to call at the garage this afternoon to see what they've found.
Cheers.
Mr2Mike said:
Is it turning over quickly, or does it sound sluggish and does the starter stall occasionally? If so then you may well have too much static advance, which would be easy to prove by backing it off a good bit. A geared starter (e.g. Brise) will also help spin it over quickly.
I'd also recommend ditching the clockwork ignition and going for a mapped system, it can make a significant improvement on an engine with 'big' cams as you can program the advance curve you need, rather than a very rough approximation. You can also add a throttle position sensor to get a 3D map, which will help fuel economy.
Ditto .. fully mapped means you can have a start up value of 0 degrees that will make starting very easy and then reverts to proper values once started.I'd also recommend ditching the clockwork ignition and going for a mapped system, it can make a significant improvement on an engine with 'big' cams as you can program the advance curve you need, rather than a very rough approximation. You can also add a throttle position sensor to get a 3D map, which will help fuel economy.
Latest update:
The car wouldn't start at all with the battery running down, but with a battery pack attached and a little shot of Easy Start in the bike carbs, it fired up on first turn of the key. Garage still insist that the distributor is not the problem, but want to check cam timing.
When revving hard, the carbs seem to be chucking petrol back out - something that I now remember happening when it was running on 40s with the previous owner. There is also an amount of breathing through the catch tank when the filter is removed from the top.
The other anomaly is that the thermostat was in place but had a hole drilled through the side, which may explain why the temp gauge is not moving.
Will wait and see what happens when the cam timing is checked/adjusted, hopefully later in the week. I have asked for a new thermostat and battery to be fitted - the latter kept going flat during the winter anyway, and they are talking about a higher rated one to cope with the starting.
The car wouldn't start at all with the battery running down, but with a battery pack attached and a little shot of Easy Start in the bike carbs, it fired up on first turn of the key. Garage still insist that the distributor is not the problem, but want to check cam timing.
When revving hard, the carbs seem to be chucking petrol back out - something that I now remember happening when it was running on 40s with the previous owner. There is also an amount of breathing through the catch tank when the filter is removed from the top.
The other anomaly is that the thermostat was in place but had a hole drilled through the side, which may explain why the temp gauge is not moving.
Will wait and see what happens when the cam timing is checked/adjusted, hopefully later in the week. I have asked for a new thermostat and battery to be fitted - the latter kept going flat during the winter anyway, and they are talking about a higher rated one to cope with the starting.
PigFilth said:
Latest update:
The other anomaly is that the thermostat was in place but had a hole drilled through the side, which may explain why the temp gauge is not moving.
This is a common mod on x-flows - it can be a pain to bleed all the air out of the coolant pipework, and air often gets trapped under the thermostat. On my car, this air stopped the temp gauge working as it wasn't in contact with the water. A small hole (~3mm) in the side of the thermostat body lets that air out when you're filling up with coolant.The other anomaly is that the thermostat was in place but had a hole drilled through the side, which may explain why the temp gauge is not moving.
My thermostat is modified in that way.
PigFilth said:
When revving hard, the carbs seem to be chucking petrol back out - something that I now remember happening when it was running on 40s with the previous owner. There is also an amount of breathing through the catch tank when the filter is removed from the top.
That is called "stand off" and is very common when running long duration cams. Ideally you'd have trumpets fitted to the carbs that are long enough to contain it.Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff