Erratic exhaust on BJ8

[NIB]

By chance i passed the exhaust on my Bj8 and felt a significant difference in whats coming from the left vs. the right pipe.
The left was smooth like on my new everyday car, the right was erratic. I suppose its cylinder 4-5-6 thats not running as good as 1-2-3. Is it possible to conclude anything else, whether its ignition or carb. problem? Is the rear carb. primarily feeding cylinder 4-5-6?

I have had problems with the spark plugs. I got the car two months ago and the dealer had put on new Champion N9YC spark plugs. If I idled the car from cold for longer time, perhaps a minute or two, with the choker on, they didnt ignite properly and the engine didnt run on all cylinders. Fixed it first time by removing the plugs and cleaning them, but second time that wasn't possible, so I had to replace them with new ones. Switched to NGK BP6ES as recommended here, because it was described as they would be better to clean themselves. Guess the engine is running to rich on one or perhaps both carbs, or perhaps the ignition is too weak. It has the original ignition system with contact breaker, condenser and a Mallory ignition coil.

 

[Superwrench]

I would check your valve clearances. Do a compression test also. Then look into carbs and ignition. Bob

 

[Michael Oritt]

I would do a plug check before anything else. Warm the car up to operating temperature, then run it in 2nd or 3rd gear at 4000 or so rpm's for 20-30 seconds, then shut off the ignition switch and coast to a stop. Pull all the plugs and see what color the insulators are and whether or not they and thelean, etelectrodes are fouled. With properly set mixture the plugs will be tan. If white too lean, if black or sooty too rich or there are other problems which we will get to if need be. If 1,2 and 3 are radically different than 4, 5 and 6 you will have an idea of your problem--either ne carb is rich and/or the other lean, etc. If only one or two plugs are different then you might want to check valves.

Report back and let us know.

 

[tahoe healey]

I agree on the plugs. They tell a lot. Also lift the pin at the back of each carb (one at a time)to see if the engine dies or speeds up. (You want a moment of faster idle then back to normal). Be sure the vacuum advance is installed properly with no leaks. Check that there is oil (I use Marvels Mistory oil) in the dampers.

 

[Keoke]

By chance I passed the exhaust on my Bj8 and felt a significant difference in whats coming from the left vs. the right pipe.

While all the comments above are pointing you in the right direction, I simply want to point out that a small difference between the outlet pressure of the two pipes can still exist because the dual exhaust system on the Healey does not contain a "Cross Over" pipe.---Fwiw--Keoke

 

[NIB]

Regarding the engine, compression and valves. I haven't checked any of this, but I can tell that the engine is fully restored two years ago with new bearings, pistons etc. The head is rebuilt for lead free petrol. Only the short block and the head was sent to a company to be rebuilt, ignition system, carbs etc. weren't. Whether or not its an honest rebuild, I dont know right now, but so far I have no reason not to believe it has been done properly.
The spark plugs I pulled out were black. They were new a couple of months ago and I have refilled the tank with petrol three times, so they havent done that many miles. I cant see any difference between the cylinders.
I tried the 4000 rpm test, but the engine misfires when driven at full throttle at high revs.
Regarding lifting the pins, they seemed a bit stuck, but I got them to move. If I lift the front I cant see any difference. If I lift the rear not much happens, unless i lift it alot, then the engine almost dies.
Forgot to look at the advance unit.
Checked oil, and there is oil in both dampers.
Something was dripping from beneath the front of the intake manifold, guess its a system removing liquid from the inlet manifold?
Also noticed, dont stand behind the exhaust at start up, black water drops comes out and stained my pants quite abit.
Going on a 150 mile vacation trip tomorrow, have filled the trunk with parts and tools, so guess all will go fine. I will try to take pictures of the spark plugs, that might be smarter than trying to describe the color. When i bought the car i took it 200 miles from the dealer so i guess it runs better on long distances than the short ones i have been doing since.

Thanx so far, for all your good advice.

 

[Michael Oritt]

"Something was dripping from beneath the front of the intake manifold, guess its a system removing liquid from the inlet manifold?
Also noticed, dont stand behind the exhaust at start up, black water drops comes out and stained my pants quite abit."
-----------------------------
Nib--

That something is no doubt dripping out of the intake manifold drain pipe and it is called gasoline! Sounds like you are running rich and that one or both of your float bowl levels is high. Assuming you have a service manual read the section on setting the float level--it is not difficult--and then proceed to lean out your carbs gradually. No amount of spare parts in the boot will make your car run better and if you do this before you depart you will have a much more pleasurable trip. Check to see if one or both of the floats are sunken.

 

[IanIrving]

Agree with Michael, one or both of your floats are sticking or set wrong. I had exactly the same problem with rough running, sooty exhaust and heavy fuel consumption till I noticed the fuel from the overflow pipes. Float level fix is easy and worth doing before you leave.

Black spots from exhaust on choke starts not unusual but they should stop once choke is off. If they don't, you are running way too rich.

Ian

 

[NIB]

Have finished the trip with no problems, but still have the problem that if I give too much throttle under acceleration it doesn't ignite properly. I will check the floats today, just looking for that piece of pipe in the right dimension as described in the service manual.
The petrol comes from the underside of the manifold, its not from the overflow pipes of the carbs. Its called a petrol drain in the Moss Motors catalogue, key no. 32 on this picture, https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=28856 . It sometimes drips after i shut off the engine after a drive. It looks like a system where the driver manually can drain the manifold, not a system that should work automatically, but perhaps its not working properly, or I dont undertsand it?

I have had problems with the chokes not returning after being in use, but so far I manually pull them back. I have seen advice on using springs, so either I do that or I replace the wires or something.

Niels

 

[NIB]

According to the manual, float height should be 7/16 = 0.44.
I measured the front to 0.56 and the rear to 0.36, both are adjusted to app. 0.44 now.

Niels

 

[tahoe healey]

When the engine stops, there should be some drops of excess fuel coming from those copper tubes (there are two).
If the choke is not returning fully you have probably found the problem. Too rich of a mixture. Do you have the return springs attached on the underside of the carbs?

 

[Michael Oritt]

Niels---

Good that they are adjusted correctly and BTW you can always use a twist drill for an accurate measuring device. The copper tubes drain excess fuel out of the manifold which is what I was referring to. The other tubes off the tops of the carb float bowls drain them. Neither is designed for "manual draining"-they work automatically (gravity and hydrostatic pressure) in case either the bowls or carb bodies are overfilled, which they should not if the floatbowl/fuel level is correct.

Now it would be good to check the actual height of the fuel in the bottom of the carb bodies whch is ultimately what you are after--do this by removing the carb domes, springs and pistons carefully and seeing where the fuel level is at the bottom of the carb. It should be even with the jet bridge and this is adjusted by the float levels which may still need some fine tuning.

Remember that there is a price to pay for running around with rich mixture (or your choke on): The oil tends to get washed off the inside of the cylinders leading to piston ring/wall wear.

 

[NIB]

Took out the pistons on both carbs. The fuel level is like 0.1 inch down the brass in the center, should it be all the way to the top of the brass thing, thats called the jet bearing.

 

[Michael Oritt]

It should be level with or just below the jet bridge. 1/10" below might be okay and I'd suggest running the car and checking the plugs after a run to see how they look and you should be able to get the lasst little bit by the mixture adjustment. If you decide to raise the fuel levei to be level with the bridge do so by carefully bending the float arms or levers or try the next drill sizw snaller to raise the fuel level in the bowls/at the bridge that little bit.

 

[NIB]

Had a look at the oil in the dampers, on the front it looked like engine oil, noncoloured, on the rear, it looked abit red. Switched both for 10W30 engineoil, can see it should be SAE20 oil originally, but the workshop manual also says 10W30 is usable.
Filled up the tank and the fuel economy on the 150 mile trip before I adjusted the floats etc. was 18.8 mpg for cruising at 60-65 mph. I believe that is about normal fuel consumption.

Niels

 

[Michael Oritt]

I use 3-in-one machine oil which is SAE 20 weight.
As long as you are in your carbs you should also check that your springs are of the same color and length and that your pistons drop in the bores at about the same speed. Test this by removing the air cleaners, pulling out the damper rods,holding both pistons all the way up with both hands and releasing them simultaneously. They should both land "clunk" at the same time. If the time is very different make sure your needles are centered and not bent and also are set in the pistons to the shoulder on the needles.

 

[Johnny]

Here's a trick I learned long ago:
Take a dollar bill and stretch it tight and place over one side of the pipe. The pressure from the exhaust should not allow you to seal up the exhaust and if you have a stuck valve or one that's not closing it'll actuall try and suck in the bill.

 

[NIB]

Took a picture of the plugs:

And a small film clip, 2MB of the exhaust.
https://850r.dk/healey/irregular%20exhaust%20320x240.avi