QuestionQUESTION: Have a couple of questions. I have a 1973 Triumph Spitfire MK4. It had a crack in the exhaust manifold however it was running pretty smooth. Got a new one and replaced the carcked one, now engine funs alittle rough and wants to stay running after ignition is turned off. Does an exhaust leak effect the timing, in other words, would it change if there was no longer a leak? Also, when slowing down there is a ticka ticka sound from the rear end. Could this be my u-joints? Thank you...Jim
ANSWER: No Jim, a cracked manifold or not cracked manifold can not change timing. Changing the exhaust manifold would not change how it runs except that when you change the exhaust manifold you had to disturb the intake manifold which can change the way it runs. The only other possibility would be if the replacement exhaust manifold has an EGR valve that is leaking or triggered at the wrong time.
A clicking noise can be a U joint and several other things so first try to determine if it is in time with a wheel rotation or faster than wheel speed (like a drive shaft U joint). If it is wheel speed check for something in the brake drum or a wheel bearing or worse yet a chipped tooth in a differential. There are also U joints on the rear axles that can be at wheel speed. Either way you should be able to raise the car on a lift and hand rotate the wheels and drive shaft and check for noise and / or loose play.
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QUESTION: I think I found out what might be another problem. This Spitfire has the Stroberg 150 car. It has the damper in the top with oil. As I pulled the damper up and almost out the engine smoothed out alot. I have the adjustment tool and have got the engine pretty close. As I remove the tool and start to put the damper back in, just as I start pushing the damper in the engine really smooths out and runs great, as it goes all the way in it runs fairly good but not as good as with it partially advanced. Is this a mixture problem? Thanks for all your help. Jim
ANSWER: Yes, but a mixture problem can be from several sources. First you need to understand what you are doing when you push the piston down. The metering needle on the bottom of the piston is tapered and goes into the jet so you might think that pushing the piston down was leaning out the mixture but another factor is involved. This is a "Constant velocity" carb meaning the air going across the jet is constant no matter what throttle setting is used, so forcing the piston down speeds up the air across the jet which draws more fuel. When you push down and it runs better it means it is too lean and starving for fuel.
You can first try to adjusting the mixture with the 3 mm allen wrench down in the top in the oil. Clockwise as viewed from the top richens the mixture. If it is already all the way then look for a vacuum leak in the intake manifold gasket or a hose. Another possible is a problem in the float chamber venting.
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QUESTION: Thank you. Is there an easy way to check for a vaccum leak around the intake manifold and hoses? Jim
ANSWER: Jim, there is a method that is used in a lot of repair shops. Warm the engine up and set the idle to where it runs rough. Slowly restrict the air going into the carb. Restrict it a little at a time more and more. A normal engine will just keep getting slower and slower until it quits. An engine with a manifold leak will at some time smooth out and may even speed up. That would only tell you that there is a leak not where it is.
There are several methods to locate the leak once you have established that it is a leak.
First pinch off all hoses one at a time to look for an RPM change. Then you can use an oil squirt gun to put oil all around the joints of the manifold. (messy) some mechanics use Argon gas or Nitrogen gas depending on it's availability in the shop. CO-2 works too. Another method is to get a piece of plastic or rubber hose and put one end in your ear and use the other end as a sniffer to probe into tight places around the intake. The leak will be a strong hiss when the engine is running. Most mechanics have a stethoscope for this.
But first rule out the adjustment of the needle and that the float chamber is vented, so you are not chasing ghosts.
Let me know how you do.
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QUESTION: Thank you. I will try this. When you talk about float chamber venting, can you tell me where that is at on this Stromberg, this could be the problem. There are two brass tubes that have a rubber plug on them. One on each side of the carb. There is also a small brass tube at the intake where the carb cleaner is attached (kind of just below the flange)it is open to air, It is just above where the gas line attaches. The photos I have in an old triumph manual of the engine looks like a breather hose sould attach to one side of the carb and another to a black cannister. There is a black cannister (Carbon cannister) on this vehicle and a breather hose comes off the valve cover and attaches to the center. There are two small outlets on each side of this cannister. Again, thank you for all, you have been very helpful and patient to answer my dumb questions. Jim
ANSWER: If you have two or three brass tubes, usually the lower one on the side is fuel supply and the other is a vent and if you have two besides the fuel line, both are vents. One on the side (usually) is the float vent and must be open. originally it went to the charcoal canister to vent and if the other is on top of the front, it is the air vent for under the piston diaphragm. Either way, both must be vented not plugged.
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QUESTION: Thanks again. The old picture I have shows what looks like a "y" coming from the rocker cover "breather", one goes off to the black cannister and one looks like it attaches to the carb. Should I reattach it this way or just leave them open to vent.? Jim
ANSWER: If you have a large hose connection on the carb near the throttle plate, it is probably that hose connection.
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QUESTION: Thanks again, just about ready to give in on this. I still think it is in the carburetor. I have been all over the engine and cannot find an intake leak. When I connect the breather hose to where the picture in the book shows it dies immediatly, it actually starts running really rough when I pull the rubber plug off before I can get the hose on. What confuses me is when I take it out on the road it runs fantastic, but just won't idle. Is there something in the carb that could cause this? Thanks again...Jim
AnswerJim, do you have a digital camera? If so take a picture of the area where the plug is that you are removing. Also the hose connection that the breather hose fits.
E-mail it to me at fitzcharlesh@bellsouth.net If you don't have a camera but do have a scanner. Scan the picture in you manual that shows the ports you are talking about. Open the picture in a editing program and draw an arrow to the two ports. If you don't have an editing program try Microsoft Paint which should work also or even a writing program. Also give me the numbers off of the carb.
Don't let this whip you.
