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Hi my Olds Dynamic with 425 ultra high compression and 2 jet carb are a little strange.
Should try to explain , runs fine on idle and highway driving at low rpm but if i came to a crossing
and need a little more power the engine feels like misfiring and feels like poor power,can feel vibrations of
this in steering wheel and car.
Runs fine when i rev it up in Park , the issues came under load.
ignition set and dwell ok ,new coil,points,condesator,rotor,cap,wires,plugs,vacum advance clock,timing gears.
The carb is a rebuilt carb from Autoline and vacum advance taken from the carb.
Verify that that you have good fuel delivery to the carb. Take the fuel line off of the carb put it in a container and check how much fuel comes out while cranking (you should probably disable the ignition). You want to see about 375 ml in 15 to 20 seconds. If you aren’t getting that, check for restrictions or leaks between the fuel tank and fuel pump, plugged sock in tank kinked line, plugged line, maybe a leaking check valve in fuel pump, a leak in this area will allow the pump to suck air.
Tough call, many gremlins can cause this problem. Maybe new battery cables, clean grounds are very important. Is the fuel an ethanol blend 10-15% ethanol like in the US: A lean condition under load would signal a lean condition, but there are many factors as gs72 mentioned, some as obscure as a plugged exhaust.
Hi,was under the car and checked the fuel tank and the fuel feed hose was almost flat under
the "support tab" on the body. The car feels better now but i should replace the hose as soon as
the fuel level in tank are lower and testdrive more. The hose feel very "soft"
Could see in my 1965 Olds Chassies manual that there should be an "saran" filter on the suction end
in the tank so that maybe be next step to check ( if i find where to buy this filter )
Hi again. Has replaced the gas filter in the gastank now but the car runs bad yet. When i drive my 98
i can notice a huge differance in engines , the 98 runs so smooth and strong.
The 88 runs "better" on low idle than high idle and feels like misfiring and hesitates , maybe something with
distrubitor ? Have checked all sparkplug wires with my ignition timing light for flashes.
Did you replace the flat rubber fuel line in the rear? That can cause your problem. I'd also replace the rubber fuel line from the metal gas line to the fuel pump.
Where is the vac advance line connected at the carb?
Above or below the throttle plates?
It could be many things,..
Ported vacuum (above throttle plates) can give too much advance at elevated throttle openings causing a surge or misfire.
Post a picture to be sure.
Where is the vac advance line connected at the carb?
Above or below the throttle plates?
It could be many things,..
Ported vacuum (above throttle plates) can give too much advance at elevated throttle openings causing a surge or misfire.
Post a picture to be sure.
I'm not sure I agree w/ you on this.
If the vacuum advance were hooked up to ported vacuum (above throttle blades) as opposed to manifold vacuum (below throttle blades or directly into intake manifold), once you open throttle blades ported vacuum becomes the same as manifold pressure (or lack thereof).
Ported vacuum & manifold intake pressure are the same after the throttle blades are open - albeit, you should not see any surge or misfire as the result of using ported vacuum or manifold vacuum once the throttle blades are open - there will simply be no affect of either manifold or ported vacuum because (1) the throttle plates are open & (2) atmospheric pressure has now equalized the pressure - e.g. no effect when throttle blades are open. If anything, you might see a difference at idle using ported versus manifold, but it would still be negligible; and, the OP has stated he has no issues at idle and when increasing RPM in Park - only under load (apparently).
...runs fine on idle and highway driving at low rpm but if i came to a crossing
and need a little more power the engine feels like misfiring and feels like poor power,can feel vibrations of
this in steering wheel and car.
Runs fine when i rev it up in Park , the issues came under load.
Many people might not have the same understanding about how an engine feels like misfiring and feels like poor power. These are tough calls to make.
However, addressing this one particular statement: "...can feel vibrations of this in steering wheel and car."
IMO, that's a serious misfire and a serious lack of power if you have vibrations in the steering wheel and car.
QUESTION:
How does your car shift? Does it shift with authority into each gear - no hesitation, no stumbling about, no slow shifting, no problems shifting under load? Do you have to baby-sit the throttle pedal getting up to speed? IOW, you cannot get up-to-speed and achieve a low rpm without a great deal of hesitation and very poor transmission shifting?
If you have any of the above symptoms, you might not have your ATM modulator hooked up, your ATM valve needs to be replaced (or adjusted - I don't know if your model vehicle has a valve adjustment), you have the ATM modulator hooked up in the wrong port, or you have a busted ATM modulator vacuum line. It doesn't take long to visualize your ATM modulator vacuum line and I would check the state of its condition.
I'm not sure I agree w/ you on this.
If the vacuum advance were hooked up to ported vacuum (above throttle blades) as opposed to manifold vacuum (below throttle blades or directly into intake manifold), once you open throttle blades ported vacuum becomes the same as manifold pressure (or lack thereof).
Ported vacuum & manifold intake pressure are the same after the throttle blades are open - albeit, you should not see any surge or misfire as the result of using ported vacuum or manifold vacuum once the throttle blades are open - there will simply be no affect of either manifold or ported vacuum because (1) the throttle plates are open & (2) atmospheric pressure has now equalized the pressure - e.g. no effect when throttle blades are open. If anything, you might see a difference at idle using ported versus manifold, but it would still be negligible; and, the OP has stated he has no issues at idle and when increasing RPM in Park - only under load (apparently).
While your description is good, I have seen many people increase the initial timing to improve idle (because of no vac advance at idle), then as you open the throttle, you get even more added vacuum timing at light to moderate throttle. In some cases, it is too much, causing a surge under cruise conditions.
In summary ported vacuum was an emissions band aid & serves no good purpose otherwise.
It is easy to move the connection & see if it helps. Verifying the total timing is a good idea.
Also a 2bbl carb is somewhat restrictive & may still see some vacuum at wide open throttle & provide a corresponding vacuum advance.
Last edited by Lonnies Performance; April 24th, 2019 at 07:30 AM.
Did you replace the flat rubber fuel line in the rear? That can cause your problem. I'd also replace the rubber fuel line from the metal gas line to the fuel pump.
Yes all rubber hoses from gas tank to carb replaced.
Originally Posted by classicmuscle.442
Check the mechanical weights on dist., looks a bit crusty, clean and lube.
I cleaned them a couple years ago but should check again.
Originally Posted by Lonnies Performance
Where is the vac advance line connected at the carb?
Above or below the throttle plates?
It could be many things,..
Ported vacuum (above throttle plates) can give too much advance at elevated throttle openings causing a surge or misfire.
Post a picture to be sure.
Many people might not have the same understanding about how an engine feels like misfiring and feels like poor power. These are tough calls to make.
However, addressing this one particular statement: "...can feel vibrations of this in steering wheel and car."
IMO, that's a serious misfire and a serious lack of power if you have vibrations in the steering wheel and car.
QUESTION:
How does your car shift? Does it shift with authority into each gear - no hesitation, no stumbling about, no slow shifting, no problems shifting under load? Do you have to baby-sit the throttle pedal getting up to speed? IOW, you cannot get up-to-speed and achieve a low rpm without a great deal of hesitation and very poor transmission shifting?
If you have any of the above symptoms, you might not have your ATM modulator hooked up, your ATM valve needs to be replaced (or adjusted - I don't know if your model vehicle has a valve adjustment), you have the ATM modulator hooked up in the wrong port, or you have a busted ATM modulator vacuum line. It doesn't take long to visualize your ATM modulator vacuum line and I would check the state of its condition.
Yes you can feel the vibrations in the car. My brother ( who drives us cars also ) took a ride with me some days ago and noticed this very well.
Have not noticed ( thinking ) something wrong with transmission before. But you have right about thats more easy to baby sit throttle pedal to get up speed.
Very intresting,should check the vacum line to the transmission
Is there any way to check the vacum modulator ? Looked in chassis manual and it looks that
the vacum modulator is connected to the modulator valve in the transmission.
The vacum modulator maybe have a rubber membran that gets old.
Checked the vacum line (steel) from engine and the short rubber hose between vacum
modulator and vacum line was very crappy .( replaced )
Is there any way to check the vacum modulator ? Looked in chassis manual and it looks that
the vacum modulator is connected to the modulator valve in the transmission.
The vacum modulator maybe have a rubber membran that gets old.
Checked the vacum line (steel) from engine and the short rubber hose between vacum
modulator and vacum line was very crappy .( replaced )
Turn the ATM valve so the ATM vacuum line stem faces straight downward. If transmission fluid comes out of the ATM stem the vacuum diaphragm inside the ATM valve is bad and needs replacement. Sometimes you will see either white or blue smoke coming from the exhaust - not a ton of smoke, but some (sometimes) - depends how badly the diaphragm is ruptured.
You could have a dead cylinder. Is the plug oily, soot black or caked with residue? Buy a new plug, check the resistance of the wire and for visible cracks that may cause the misfire.
You could have a dead cylinder. Is the plug oily, soot black or caked with residue? Buy a new plug, check the resistance of the wire and for visible cracks that may cause the misfire.
Hi i suspekt that cylinder nr 5 is dead .
The plug was just like you write.
And when i pull of the plugwire engine idling it
Is hard to notice any difference on engine
There is no reason to disturb wires on other cylinders for testing.
1. Verify the #5 plug wire is connected to the spark plug. The plug wire can get pulled back in the spark plug boot and not making contact.
2. Connect a new spark plug or timing light to #5 to check for spark. Be sure plug is grounded, you may have to try laying it a couple places, if using a spark plug.
3. If you have spark at the electrode of the new spark plug, replace #5 spark plug,
4. Connect OLD #5 plug to spark plug wire to test for spark (same way you checked new spark plug) . If it sparks, you may have other problems.
5. Connect #5 spark plug wire to new #5 spark plug and start car.
Try switching wires around and that plug. But I would throw a compression tester on that motor.
Thanks for tip all Was thinking , if i turn the engine so the mark on the flywheel aligns with zero mark,will both valves on cyl 5 be fully closed ?
Was thinking to blow air thrue the sparkplug hole with a threaded connector. And try to see were the air goes.
Or take off the valve cover to look att the valves when they are closed are easier ?
Putting the timing mark at 0 would put #1 on compression (every other revolution)... this is the front left plug as you sit in the car.
From this, rotate 1.25 turns clockwise looking from the front of the car to put #5 on compression at TDC.
Putting the timing mark at 0 would put #1 on compression (every other revolution)... this is the front left plug as you sit in the car.
From this, rotate 1.25 turns clockwise looking from the front of the car to put #5 on compression at TDC.
It could be the valves aren't closing. You might want to pull off a valve cover. Could be too tightly adjusted valves (if you've replaced the stock unadjustable valve train), bent valves, broken valve spring, etc... You will probably have to remove the head to know for sure.
BTW. If you can take a picture with the piston down in the cylinder, you might be able to see if the cylinder walls are scored. If they look great all around, it's probably in the head.
It most likely is more than rings when you get a compression of zero in one cylinder. I run my compression tests both dry and wet to gain an impression of the health of piston rings.
Squirt some engine oil (2 or 3 teaspoons) down #5 then take another compression reading of #5. If you gain compression, it generally points to bad rings. However, if you you gain no compression at all, it's most likely more than bad rings.
October 11th, 2018, 12:28 PM
