A
Anonymous
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My old worn out 170 I just pulled ran fairly well- idle was a bit rough and it had that typical autolite 1100 hesitation at part throttle going down the road. Once I put my 200 in 2 weeks ago (rebuilt with about 1k miles on it- I did not run/drive it before I bought it ) everything got worse- I figured it was due to the carb being too small for the engine. Idle was still a bit rough, and there was that same hesitation but also what felt like a misfire or “surging†when going down the road at about 2,000 rpm or lightly accelerating at that speed.
Last week, thinking it might be the 200 distributor (dual vac. advance with only one hooked up) I put the distributor from my 170 in the 200- a remanufactured single vac/centrifugal advance unit for a ’68 mustang. I had no change in performance. (I had it timed at 14deg. of initial advance, with about 36 deg. of total advance at about 3500rpm with no misfire when I had it in my 170 ) I figured the problem was the small 170carb with the 1.5 opening not giving enough air/fuel to the big log head with the 1.75 opening.
Last night I put on my new remanufactured Carter YF for a 200. After tuning idle speed and mixture, the idle was the smoothest I’ve ever seen on either of the engines, and the exhaust note quieter and smoother as well- not that ugly “spitting†sound. When I hit the road, the hesitation when accelerating part throttle was gone but the misfire was much worse- now at about 1500 rpm, most noticeable at low speeds in 2nd gear holding steady at about 20mph the car really misfires. . I don’t feel the hesitation much at all cruising at higher rpms, going up a hill, or accelerating full throttle.
When I hold the engine at high idle (maybe 1500-2000 rpm) it misfires- as I retard the timing it gets smoother. However, by the time I retard timing enough for the misfire to go away, my initial timing is down to 0 deg. BTDC, if not slightly retarded, and off-line performance is lousy as well as idle, and the exhaust note is awful.
Checked timing again this morning-
14deg intitial, misfire beginning at 1500 rpm with 48 deg total advance, 56 deg. total at 2500 rpm
0 deg. initial, no or very little misfire, 44deg. total at 2500rpm
10deg initial (factory setting), misfire at 1700 rpm with 42 deg. advance, 50 total advance at 2500 rpm. This is what I left it at for the moment – the car has tons of low end now, and better idle, but still has surging/misfire cruising at about 2000rpm. If I hit the gas, it accelerates smoothly, though.. It seems there is much more advance with the carter YF over the 1100 – but why?
I’ve put the timing light on each of the plug wires at the rpm where the misfire occurs, and don’t see a misfire there. Could this problem be with the Carter YF pulling too much vacuum, another internal carb problem (like being too lean), as well as something else causing the misfire? I have not played with the cent./vac. Advance settings as I’ve never done that and don’t want to cause more problems, and besides this distributor is intended for the 200 anyhow.
All plugs are uniform- whitish –tan tip with a tiny bit of carbon fouling at the base so maybe it’s a bit lean (drove less than 10 miles last night) I’m running no air filter with the YF at the moment as the old housing does not fit. I’m using the same fuel pump, plugs (.035 gap) flamethrower coil, points (.025 gap), 38 deg. dwell, plug wires, and generator off my 170 as well, so could it be an internal problem with the engine? I can’t find any vacuum leaks. Gas mileage is much worse than the 170, but that could be due to the larger displacement and that it's not broken in yet as well as whatever else is going on.
I don’t want to drive it much with fear of damage to my new engine- please help- Sedanman's in distress!
Thanks,
Thor
Last week, thinking it might be the 200 distributor (dual vac. advance with only one hooked up) I put the distributor from my 170 in the 200- a remanufactured single vac/centrifugal advance unit for a ’68 mustang. I had no change in performance. (I had it timed at 14deg. of initial advance, with about 36 deg. of total advance at about 3500rpm with no misfire when I had it in my 170 ) I figured the problem was the small 170carb with the 1.5 opening not giving enough air/fuel to the big log head with the 1.75 opening.
Last night I put on my new remanufactured Carter YF for a 200. After tuning idle speed and mixture, the idle was the smoothest I’ve ever seen on either of the engines, and the exhaust note quieter and smoother as well- not that ugly “spitting†sound. When I hit the road, the hesitation when accelerating part throttle was gone but the misfire was much worse- now at about 1500 rpm, most noticeable at low speeds in 2nd gear holding steady at about 20mph the car really misfires. . I don’t feel the hesitation much at all cruising at higher rpms, going up a hill, or accelerating full throttle.
When I hold the engine at high idle (maybe 1500-2000 rpm) it misfires- as I retard the timing it gets smoother. However, by the time I retard timing enough for the misfire to go away, my initial timing is down to 0 deg. BTDC, if not slightly retarded, and off-line performance is lousy as well as idle, and the exhaust note is awful.
Checked timing again this morning-
14deg intitial, misfire beginning at 1500 rpm with 48 deg total advance, 56 deg. total at 2500 rpm
0 deg. initial, no or very little misfire, 44deg. total at 2500rpm
10deg initial (factory setting), misfire at 1700 rpm with 42 deg. advance, 50 total advance at 2500 rpm. This is what I left it at for the moment – the car has tons of low end now, and better idle, but still has surging/misfire cruising at about 2000rpm. If I hit the gas, it accelerates smoothly, though.. It seems there is much more advance with the carter YF over the 1100 – but why?
I’ve put the timing light on each of the plug wires at the rpm where the misfire occurs, and don’t see a misfire there. Could this problem be with the Carter YF pulling too much vacuum, another internal carb problem (like being too lean), as well as something else causing the misfire? I have not played with the cent./vac. Advance settings as I’ve never done that and don’t want to cause more problems, and besides this distributor is intended for the 200 anyhow.
All plugs are uniform- whitish –tan tip with a tiny bit of carbon fouling at the base so maybe it’s a bit lean (drove less than 10 miles last night) I’m running no air filter with the YF at the moment as the old housing does not fit. I’m using the same fuel pump, plugs (.035 gap) flamethrower coil, points (.025 gap), 38 deg. dwell, plug wires, and generator off my 170 as well, so could it be an internal problem with the engine? I can’t find any vacuum leaks. Gas mileage is much worse than the 170, but that could be due to the larger displacement and that it's not broken in yet as well as whatever else is going on.
I don’t want to drive it much with fear of damage to my new engine- please help- Sedanman's in distress!
Thanks,
Thor
)I cannot tell if it's detonating under acceleration
) the test results;
