Cant drive 55 Literaly

[FetchMeAPepsi]

Originally Posted by cg285

wait awhile until this is 10 pages long, with hundreds of off the wall theories, and he is still at the beginning

LOL, yeah that's possible, but what fun it'll be getting there. he'll be a pro at everything by that point!

[66CHEV]

I am really glad everyone else is having a good laugh over this. btw I have had it to a shop where everything is not technical and they "merely fix things" and that mechanic who has many years of experience has re-checked everything that I have done and it still runs like crap. In fact I have spoken with several people who know about these old trucks, including you guys on here. To this point I have tried and checked everything that has been suggested on here short of tearing the engine apart piece by piece which I would rather not do. Yes I may be getting technical at this point but right now I am grasping for anything that could be the slightest bit off that would cause the problem. That was the reasoning behind the whole question about the resistance check on the coil.

[cg285]

Originally Posted by 66CHEV

I am really glad everyone else is having a good laugh over this.

i'm not laughing i've just seen this movie too many times. it's bad enough with a customer in front of you and you have to go to extremes to try to pry any information out. it's way worse online. so far you are giving us only information that you want to or think we need.
you have yet to answer some simple questions.

[66CHEV]

cg285
per the questions you asked

vac reading at idle is a very fast fluctuation between 10 and 20 in. (will not stabilize until i give it a little throttle around 700 rpm) at which point it will stabilize at around 12 in. The more throttle I give the higher it climbs but will top out at around 17 in. with the throttle wide open. This is all being read from the vacuum port on top of the intake manifild that the pcv valve connects to.

yes at one time the truck ran fine, started to develop a stumble/hesitation when shifting through the gears from a dead stop. thats when I decided to do the tune up a couple weeks back. (new plugs, cap, rotor, points, cleaned carb, fuel filter is good, plug wires are good, dist. shaft is not loose, mech. advance is working, new vacuum advance, changed intake/exhaust manifold gasket)

firing order is set 153624, timing is set 4 deg before zero with vac advance disconnected and plugged, points are gapped at 0.19, plugs are gapped at 35, fuel pressure is fine around 4 lbs, all valve springs checked good at 180 lbs, rocker arm travel is fine i.e. the exhaust and intake are travelling the same distance, there is fire out of all six plugs, still have the miss and no power.

dont know if i have mentioned before or not but everything under that hood has less than 30,000 miles on it. I ordered an new short block stock setup, took the original head to a machine shop and had it totally re-worked and tested.

dont mean to sound like a jerk but its just got me so frustrated at this point. This is my daily driver and so i am driving it each day as is because i have no other choice. that is why i really need to get the thing running better.

also i verified last night that the throttle plate is opening all the way, however when you punch the accelerator instead of a steady stream like out of a water gun it comes out more like a pour out of a straw, could that be what is causing all this trouble.

[cg285]

ok, so you stated hesitation then later "still have the miss" - so which is it?
1. you can do a cyl bal by pulling one plug wire at a time out of the cap and noting the change in rpm (of course the eng needs to be running). no change is a dead cyl. as a bonus you can chk your coil by watching the blue flame jump to the wire when you reinstall it.
2. still don't know about the condition of the fuel filter and
3. you still need to chk the fuel flow. you can do this by taking the coil wire out, take the line off at the carb, put a hose on in and stick the hose in a clear, empty, clean water bottle - crank the engine and see what kind of flow you have. like taking a piss you either have a strong stream or a dribble. as a bonus you can inspect the fuel and see if water settles to the bottom.
4. does the engine sound like it is laboring? does it slow and pickup? or just get slower? or....

[ACK]

Just throwing this into the mix ... over the years, the harmonic balancer timing marks have been manufactured in different locations. If you don't have the original balancer, there's a chance it was replaced with one designed for a different timing location. Confirm TDC on the #1 to see if the mark is accurate.

Another possibility is the balancer is separating. To check, place a mark on the rubber section that lines up with the mark on the metal section, hit it with the timing light and see if they appear to move in unison or separately. If they move separately, that's a dead give away that the rubber and metal are separating.

[66CHEV]

ok,
i have took the plug wires off one at a time from the plugs not the cap but anyway all cyls make a difference in the running of the engine however cyl 1 and 6 have less effect than the other 4 do (which tells me these are the two that causing the problem for whatever reason??).

there is no fuel filter on the truck. the old tank was rusty i am running a 12 gallon marine grade plastic tank mounted in the bed of the truck the only filter is the sock on the end of the line in the tank.

fuel flow is a good solid stream, carb bowl is always full when i have taken the carb apart.

as far as the hesitation and question 4 this is the best way i know to explain it.

with the motor warm (idle at +/- 600) if i am sitting still motor sounds pretty smooth can maybe hear a slight miss. when i take off in first gear still pretty smooth then when i clutch it and change to second as i am letting off the clutch and giving throttle this is where i get what i am calling a hesitation. the motor is running rough at this point and continues to do so for a short distance it seems that if i let off the throttle slightly to where i can hear the whistling sound through the top of the carb then i can give it gas and as long as i am not trying to pull a hill it will go back to a pretty smooth run. switching to third is the same effect.

now once its in third gear and i am driving down the highway if i hold it around 40 mph it is decent but when i try to accelerate faster it seems as if the engine bogs down and then starts to run rough once again until i let off of the throttle.

and ACK i thought of that as well and checked the harmonic balancer twice just to be sure, it is lined up right on the mark

[cg285]

sounds like you are describing a missfire under load. double check your firing order. did you change the plug wires when you did your tuneup thing?

[cg285]

and pulling the wires off at the plugs instead of the cap is a good way to get jolted. pull one off at the cap and verify your spark.

[63burban]

Everything I ever learned has been trial and error, at 13 I got the old 1946 Chevy 2 ton farm truck running that was sitting out behind the shed. I ran around the fields with it, hauled hay and oats and it never had brakes. Go through one system at a time and make sure it's correct, process of elimination. These trucks are almost as simple as a Model "A", ask an old timer in your neighborhood for help. No offense but some people are just not cut out to be old car people.

[66CHEV]

that is a good way of putting it "missfire under load" dont know why i didnt just say that may have saved a lot of time but anyway. I have checked the firing order 5 or 6 times taking every wire off and very slowly putting them back on one at a time verifying the order to me (from past experiences) it runs like the firing order is off or the timing is off.

did not change the wires, just inspected them and checked the resistance reading through each wire, they are all to spec. no arcs in the dark if you look under the hood at night with the engine running, check that last night.

i will keep in mind the pulling off at the cap i have for whatever reason just pulled them off at the plugs

[cg285]

remember compression, or lack of, doesn't missfire under load.usually plug or wire. you could have cracked a plug or 2 putting them in. or the wires are arcing or ... or your firing order is off because you are dyslectic

[1966shortwide]

so many pages lol have you done a compression check on each cylinder????

[66CHEV]

i will guarantee that the firing order is correct (153624) i know that order better than i know my own name, unless this 250 is different from all others. if the wires are arcing it is a invisible arc but i will change them anyway just to give it a shot.

63burban, i have asked every old car guy i know including some who are mechanics and we still havent figured this out. no offense taken about being old car people but i have grown up around old cars all of my life including model a's in fact i have one, i would take an old car over a brand new one anyday, but this thing is just a hurdle i cant seem to jump over.

[1966shortwide]

reading i see you checked comp,,,, have you tried removing exhaust pipe from manifold to rule out plugged exhaust , and drive it see what it does.Tke needle bounce on vacuum guage is a concern also.

[66CHEV]

yes did the compression check, have good even compression on all cylinders, however it was tested with on that you hold against the spark plug hole so when the compression stroke occurs it does blow the tester away from the block so depending on how tight you are holding it readings could be off slightly

[cg285]

suggestion:
find someone with a sun scope. it shouldn't take long and you will learn something

[cg285]

for those that don't know: even compression is checked electronically these days - actually it's been done that way for quite some time.

[1966shortwide]

Year's ago i had a car with no power on a 396 engine in a car i had bought . The previous owner had a mechanic try everything under the sun to make it run decent.He got tired of messing with it and sold car to me . I did not try to get it to run correctly as i wanted to sell it anyway,as i was putting car back to factory engine 327 it came with. I removed 396 engine and seen the problem.The right side exhaust pipe was a double walled pipe and the inner pipe had collapsed and plugged off the pipe right next to the manifold.I sold the engine to a friend and he installed in a 65 chevelle and talk about a tire fryer, it did just that.That is why i would disconnect at manifod to rule out exhaust.

[cg285]

Originally Posted by 1966shortwide

Year's ago i had a car with no power on a 396 engine in a car i had bought . The previous owner had a mechanic try everything under the sun to make it run decent.He sold car to me , as i was putting car back to factory engine it came with. I removed 396 engine and seen the problem.The right side exhaust pipe was a double walled pipe and the inner pipe had collapsed and plugged off the pipe right next to the manifold.I sold the engine to a friend and he installed in a 65 chevelle and talk about a tire fryer, it did just that.That is why i would disconnect at manifod to rule out exhaust.

that's why you do a vacuum test - so you don't have to work as hard.

[1966shortwide]

Originally Posted by cg285

for those that don't know: even compression is checked electronically these days - actually it's been done that way for quite some time.

Well aware ,i run several for 30 year's,

[1966shortwide]

Originally Posted by 66CHEV

yes did the compression check, have good even compression on all cylinders, however it was tested with on that you hold against the spark plug hole so when the compression stroke occurs it does blow the tester away from the block so depending on how tight you are holding it readings could be off slightly

Not A good test you need a tester that screw's in and get a accurate reading so you can watch the total cycle of each cylinder.

[awbrown]

Originally Posted by 1966shortwide

Year's ago i had a car with no power on a 396 engine in a car i had bought . The previous owner had a mechanic try everything under the sun to make it run decent.He got tired of messing with it and sold car to me . I did not try to get it to run correctly as i wanted to sell it anyway,as i was putting car back to factory engine 327 it came with. I removed 396 engine and seen the problem.The right side exhaust pipe was a double walled pipe and the inner pipe had collapsed and plugged off the pipe right next to the manifold.I sold the engine to a friend and he installed in a 65 chevelle and talk about a tire fryer, it did just that.That is why i would disconnect at manifod to rule out exhaust.

I think I mentioned this earlier about the double wall exhaust and that would have the same effect when you back off the throttle..,.. but would like to ad ,if the engine picks up at 40mph when you back out of the throttle tells me the power enrichment circuit may not right , with Q-jets it ment the primary metering rods where stuck in the down position.. What carb do you have???

I rebuilt a carb for a guy once and he said it ran the same , so I went and looked at it and figured it had a plugged exhaust ,the guy swore up and own it was ok , so I asked him for a hacksaw and promptly cut the exhaust pipe and it ran and idled perfectly ..........

[66CHEV]

I have a 1 barrel carb

[awbrown]

old style Rochester or is it a monojet ?? the monojet has a rod connecting the primary metering rod ,I think the old style rochester has a spring loaded piston controlled by vacuum , I think .. it has been a while since I have had one apart ......