It wasn't clear, but it sounded to me like he was saying that the valves for the #1 cylinder are in their overlap position (Ex closing and Intake opening) when the cam wheels are at their pointers -- which is correct, and #4 piston is ready for the power stroke. If that is what was stated, then all should work well.
Please verify that the engine is at TDC when the cam wheels are at their marks. Take #1 or #4 spark plug out, and put a wooden dowel or a straw or something safe in the hole to rest on top of the piston, and verify that it is at the peak of its travel. This is not terribly accurate, but you can get darn close if you are patient. If you have a dial indicator to put into the hole and read the position of the piston, that would be ideal. Anyway, verify TDC is really TDC when the cam markers are at their marks (and that the pulleys are correct).
Yes it may matter where the aux shaft pulley is pointing. On many engines, the lobe on the end of the aux shaft can bang against #2 connecting rod, and you don't want that to happen. To prevent this, the aux pulley marker should be pointed at at about 1:30 o'clock when the other pulleys are at their marks.
Alvon
Backfires through carb
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dcarey
Re: Backfires through carb
Thanks for all the help troubleshooting this problem.
To restate the problem:
- the car has not run in eight years
- I pulled the engine, cleaned it replaced, water pump, starter, plug wires, etc.
- the engine idles very well, smooth at 800 rpm
- the engine revs in neutral, no problem
- but when I drive the car and hit the gas, it backfires hard, through the carb
What I found:
- the keyways on the cams match the marks on the cam drive wheel.
- for some reason when the cam timing marks are aligned with the pointers, the distributor is firing #4 but the cam lobes are properly aligned for #4 and crank is aligned (TDC). When I line up the cam lobes, crank and dist for #1, the cam wheel timing marks are out 180. So I think this is ok.
- This also means that the cams are ok relative to each other.
Most likely causes:
- I installed a new timing belt (prior to running the engine), and I could have sliped the belt one tooth (maybe two but very unlikely) relative to the crank - could that be the cause? But why does it do this only under load?
or
- even though the accelerator pump diaphram appears to be fine, the nozzle is not leaking and is clear and I see a very good stream when I press the accelerator, I don't know what the stream should look like. And this problem does sound like it is running lean under load, so the acceerator pump would still seem to be a cause.
To restate the problem:
- the car has not run in eight years
- I pulled the engine, cleaned it replaced, water pump, starter, plug wires, etc.
- the engine idles very well, smooth at 800 rpm
- the engine revs in neutral, no problem
- but when I drive the car and hit the gas, it backfires hard, through the carb
What I found:
- the keyways on the cams match the marks on the cam drive wheel.
- for some reason when the cam timing marks are aligned with the pointers, the distributor is firing #4 but the cam lobes are properly aligned for #4 and crank is aligned (TDC). When I line up the cam lobes, crank and dist for #1, the cam wheel timing marks are out 180. So I think this is ok.
- This also means that the cams are ok relative to each other.
Most likely causes:
- I installed a new timing belt (prior to running the engine), and I could have sliped the belt one tooth (maybe two but very unlikely) relative to the crank - could that be the cause? But why does it do this only under load?
or
- even though the accelerator pump diaphram appears to be fine, the nozzle is not leaking and is clear and I see a very good stream when I press the accelerator, I don't know what the stream should look like. And this problem does sound like it is running lean under load, so the acceerator pump would still seem to be a cause.
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dcarey
Re: Backfires through carb
One other possible cause:
When I rotated the dist to time the engine, I noticed that the dist cap was conducting (I get a shock when I touch it). Could the cap somehow be energized and triggering a spark in cylinders on the intake cycle? I wiped out the inside of the cap and sprayed it w WD 40 but it is still conducting. Seems an unlikely cause but I will get a new cap.
When I rotated the dist to time the engine, I noticed that the dist cap was conducting (I get a shock when I touch it). Could the cap somehow be energized and triggering a spark in cylinders on the intake cycle? I wiped out the inside of the cap and sprayed it w WD 40 but it is still conducting. Seems an unlikely cause but I will get a new cap.
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ventura ace
Re: Backfires through carb
I had something similar happen to me once. I had the wrong cap. There are some caps that look identical on the outside, but very different gap on the inside. The rotor was about 1/2" from touching the center contact, and about the same distance away from all the other contacts, and it would shock me every time I touched it (electricity trying to find the path of least resistance). It actually ran very well that way for 200 - 300 miles until things got all carboned up from arcing across the big gap, and then it wouldn't run at all. No spitting through the carbs though, that I can recall. But it seems like it may want to do so if all the plugs are firing at the same time, like they were with mine. I would certainly investigate and fix that problem before going any further.
Alvon
Alvon