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BN7 Starts after 25 years [but with problems]

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J

JJS

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Hi,

I have spent the morning working on starting my 60 BN7 for the first time. It starts (HurraH!!!) but runs very poorly. The engine was rebuilt about a year ago. I have a posi-flow electric pump, and HD8 carbs installed. Pertronix ignition.

The problem ... the carbs are not sucking air, they're blowing air. There isn't an obvious sticking valve. I haven't done a compression test. Any ideas?

Thanks

Joe
 
Hi Joe,
Did you set the static timing? What do you mean when you say the engine is running poorly? Are the carbs spitting as in a backfire? Does the engine run better on full choke?
 
Thanks Greg,

I set the static timing. Seems to be fine.

The engine sounds like it's chugging. It doesn't start easily, it trys to start right away, but takes 10 seconds or so with the throttle wide open to start running. The carbs don't backfire, there is a constant stream of "air" coming our of the carbs. You can see the gasoline blowing from the carbs.

Choke or no choke does change anything.

Joe
 
Thanks Greg,

I set the static timing. Seems to be fine.

The engine sounds like it's chugging. It doesn't start easily, it trys to start right away, but takes 10 seconds or so with the throttle wide open to start running. The carbs don't backfire, there is a constant stream of "air" coming our of the carbs. You can see the gasoline blowing from the carbs.

Choke or no choke does change anything.

Joe
 
Hmmm, honestly I've never seen that before. Obviously fuel is going in or it wouldn't fire at all. Do you know what the PSI of that pump is? It should be something around 3lbs. Is it one of these? Facet
 
Hi Greg,

That's the one I have. Could it be a sticking valve or something similar that would blow air back through the carbs?

I plan to do a compression test tomorrow. Maybe it'll will tell me something.

Joe
 
You say the carbs are not sucking air but "Blowing" it. Sounds either like your timing is grossly off or perhaps the intake valves are not closing all the way. I am surprised the engine runs at all. Try to do a static (leak down) compression test and see what readings you get.
 
If the valves completely close, and I'm suspecting they do, then I'm with Michael on the timing.

At 180* (plus or minus) out, you can still get it to fire and run, but just barely.

Firing order 1,5,3,6,2,4. With the plugs out, hold your finger on the #1 plug hole and rotate the engine (bumping the starter) until you get PPHHTT! out the hole; verify at the crank pulley TDC. Look at the rotor under the distributor cap, and verify it's pointing to the #1 terminal. Verify the rest of the terminals go to the correct cylinders, and it should run much better.
 
Michael Oritt said:
You say the carbs are not sucking air but "Blowing" it. Sounds either like your timing is grossly off or perhaps the intake valves are not closing all the way. I am surprised the engine runs at all. Try to do a static (leak down) compression test and see what readings you get.
Click to expand...
Ditto on the intake valves. Be sure you use the normal "Healey rule" for adjusting the valves! Also make sure the vacuum advance is working...particular attention to the mechanical weights...they need to move easily.
Patrick
 
Healey 100 said:
Make sure the ignition wires are in the proper order.
Click to expand...
Bingo, I have to agree the wires aren't correct. You might also check that all the intake and exhaust manifold nuts are tight. Also there are holes in the intake manifold make sure they are all filled with something.
 
Thanks for all of the advice.

I rechecked the static timing and advanced the timing 1 cog on the gear.

I checked compression, 190 lbs on 4 cylinders, 185 lbs on two cylinders.

Valve clearance is good. No unblocked holes in the intake manifold.

And these changes worked, the car now runs and will idle at 1,000 rpm. It's sounds a bit rough though.

The carbs still spit fuel out the carb inlet, but I can feel suction at the carb inlet. It's a bit of a mystery. I suspect something is amiss with the carbs, I purchased them used and sent them off to be re-built. But I notice that the piston in the rear carb is bouncing at idle (it chatters) And I'm not able to give them much throttle without them spitting a cloud of fuel.

Thanks again for the help.

Joe
 
JJS said:
Thanks for all of the advice.

I rechecked the static timing and advanced the timing 1 cog on the gear.

I checked compression, 190 lbs on 4 cylinders, 185 lbs on two cylinders.

Valve clearance is good. No unblocked holes in the intake manifold.

And these changes worked, the car now runs and will idle at 1,000 rpm. It's sounds a bit rough though.

The carbs still spit fuel out the carb inlet, but I can feel suction at the carb inlet. It's a bit of a mystery. I suspect something is amiss with the carbs, I purchased them used and sent them off to be re-built. But I notice that the piston in the rear carb is bouncing at idle (it chatters) And I'm not able to give them much throttle without them spitting a cloud of fuel.

Thanks again for the help.

Joe
Click to expand...
When you say "spitting" out the carb inlet, do you mean that it does this if you increase the engine speed? If, yes, is it more like a "loud popping/spitting sound/characterist? Got oil in the carb dampers?
Patrick
 
Re the piston bouncing did you check the oil in the damper, esp. in the one that chatters? Also see if the springs are correct and the same length.
 
Are both carbs doing this blow back or only the one that chatters? Check the damper at the end of the rod that goes into the piston (with the black cap on top). You should feel equal resistance as you push this device into the top of the damper chamber.
What do you hear at the end of the exhaust? Is it rhythmic?
Isn't that a little high for compression? I would think if you are bowing back through the carbs, there is something wrong with the valve s not opening at the right time. You should be able to put your hand over the carb and feel it suck on your hand. That's how a carb synchronizer works. I would not run the engine until you get this straightened out.
Who put on the timing chain?
 
The engine was built by a english car restorer in Venice Beach. He's done a bunch of Healey's, so I feel comfortable with the timing chain installation.

The exhaust is rhythmic, with a few misses.

There is suction when I put my hand up to the intake of the carb. The carbs aren't blowing fuel, on closer inspection it looks like fuel is coming out of the jet and hitting the bottom of the piston, then spraying out of the carb intake. Some of the fuel is making it to the engine as well.

I'm going to take a close look at the carbs over the next few days and make sure that I don't have too much fuel pressure, the jet/needle combination (and spring) is correct, and that the dampers are working properly.

Thanks again for everyone's help!
 
JJS said:
The engine was built by a english car restorer in Venice Beach.
Click to expand...
Peter, by chance?
 
HI,

I'm in Bakersfield. Peter did the rebuild of the engine. He has been great to work with,

I'm in the middle of taking apart the carbs. The damper in chattering carb is about 1/2 inch shorter than the other carb, So it looks like I need a replacement. The springs are not color coded, so I'm not too sure if they are correct. Is there another way to tell?

Joe
 
"Is there another way to tell?"
--------------------------------
Yes--overall length. It is all spelled out in the SU book but I do not have access to mine right now. Someone on the forum will probably come back with this within the day. In the meantime get the correct damper and also do a drop test on both carbs to see if the pistons are hanging up in the bores, etc.
 
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