351c running poorly

[piper62j]

First things first.. Before you spend any more time and money swapping and theorizing.. Perform a compression test. If all the cylinders are within 25% of max psi, then the engine is in great shape. Not knowing the history of the work that has been done on this engine. From there, you will know if it's valves or rings.. If all checks out good, then move on to the ignition system.. Lastly, if the above items are spot on,, inspect the carburetor for wear at the throttle shaft where it runs thru the base.. The base wears on the return spring side causing a vacuum leak, which can create all kinds of performance problems.

Keep us up to date on your progress..Good luck.

 

[will e]

poper62j - I did get it figured out and it was an ignition problem. I am all for you line of thinking. Rather than toss parts at it (other than a couple of spark plugs and a spare distributor cap) I did some good old fashioned trouble shooting first. I got bit by a bad distributor cap recently so it was up there with possible issues.

A compression test was on the list. If the two bad firing cyl were next to each other it would have been close to the top. A complete compression test is a little time consuming and given the age of the engine (and the randomness of the issue) it wasn't high on my troubleshooting list.

Normally I go this order for 'running funny'. (with some modifications depending on the symptoms)

Visual for vacuum leaks

Check of PCV valve

Hook up vacuum gauge and try to determine the results.

Confirm timing.

Inspect spark plugs. (At this point a compression test might get done depending on the condition of the spark plugs and what the vacuum gauge had read)

Pull each plug wire while running to see if there is a change. (I think I am just going to use the timing light instead. It was really handy at showing me which cyls were not firing).

Check fuel bowl levels.

I am always very hesitant to touch the carbs, especially for a intermittent problem. Since the car is only driven on occasion wear isn't much of a factor however I do get concerned about 'old gas' and 'sludge'. I try to start it once a month during the 'non-driving' season. I will check to make sure the floats are not sticking.

 

[will e]

Update: First long drive (to work). Ran great. Idled as smooth as you would expect given the build. Smooth power. Really fun! I am going to leave the two 'hot' plugs in for a week or so and then pull them and the cold ones and take a look.

 

[mdunlap]

Will e

Please forgive me if you already know this and I expect some pushback from others as well.

There are 3 main places to start in diagnostics with our computer-less engines. And they are the fire triangle; fuel, fire and air.

If you have an intermittent fault that is quickly fluctuating, all of them can be the source from a poorly operating carb, to a vacuum leak to a number of ignition issues and even compression.

First, chose 1 of the 3 based on what you know about your engine. If you just purchased/changed/messed-with something in one of these categories (fuel, fire, air) this is likely the area to start your work.

Second, though I consider all of the given advice valuable, I suggest sticking with that specific point of the fire triangle until you have exhausted all probable cause before moving to the next. For instance, if you start with ignition (fire) stick with it and move on to the next (air or fuel).

Finally, this approach will not only help you better keep track of what you're doing but more than likely reduce your trouble-shooting time and save you money from switching parts.

 

[Mister 4x4]

First things first.. Before you spend any more time and money swapping and theorizing.. Perform a compression test. If all the cylinders are within 25% of max psi, then the engine is in great shape. Not knowing the history of the work that has been done on this engine. From there, you will know if it's valves or rings.. If all checks out good, then move on to the ignition system.. Lastly, if the above items are spot on,, inspect the carburetor for wear at the throttle shaft where it runs thru the base.. The base wears on the return spring side causing a vacuum leak, which can create all kinds of performance problems.

Keep us up to date on your progress..Good luck.

Not to be a turd, and we've all been guilty of it before, but this is a good example of why it's important to read the whole thread before posting.

Piper62j has a lot of good information to share (seriously - good stuff, Man!), but it's pretty obvious they missed the part where will e solved the issue by cleaning/adjusting the Uni-Lite ignition module/distributor rotor.

Anyhoo - just a friendly reminder to get the whole story if you can - and don't forget to present this post to me the next time I do it as well. rofl

 

[will e]

Will e

Please forgive me if you already know this and I expect some pushback from others as well.

There are 3 main places to start in diagnostics with our computer-less engines. And they are the fire triangle; fuel, fire and air.

If you have an intermittent fault that is quickly fluctuating, all of them can be the source from a poorly operating carb, to a vacuum leak to a number of ignition issues and even compression.

First, chose 1 of the 3 based on what you know about your engine. If you just purchased/changed/messed-with something in one of these categories (fuel, fire, air) this is likely the area to start your work.

Second, though I consider all of the given advice valuable, I suggest sticking with that specific point of the fire triangle until you have exhausted all probable cause before moving to the next. For instance, if you start with ignition (fire) stick with it and move on to the next (air or fuel).

Finally, this approach will not only help you better keep track of what you're doing but more than likely reduce your trouble-shooting time and save you money from switching parts.

No worries, that is really good advice. There is always a little bit of a balance of course. Often a quick check on fuel/fire (ignition) if the engine isn't running at all will help you narrow it down.

One good thing I got out of it. A brand new fuel pressure gauge (under hood) right at the fuel rail. This not only gives me a baseline value but will give me quick reference for the fuel part if the engine isn't running. (False positive possible if I have fuel pressure but the carb is messing up).

 

[mdunlap]

Not to be a turd, and we've all been guilty of it before, but this is a good example of why it's important to read the whole thread before posting.

Piper62j has a lot of good information to share (seriously - good stuff, Man!), but it's pretty obvious they missed the part where will e solved the issue by cleaning/adjusting the Uni-Lite ignition module/distributor rotor.

Anyhoo - just a friendly reminder to get the whole story if you can - and don't forget to present this post to me the next time I do it as well. rofl

Mister 4x4,

I read every word. I even stated, "I consider all of the given advice valuable." I'm not quite sure how my comment became a "good example of why it's important to read the whole thread before posting."

The reason I posted what I did is because I felt that the advice given, though sound, was given in a manner that a novice reading this thread would be confused. I simply wanted to categorize the process into bold-print, troubleshooting, language. I guess it's the teacher in me.

I agree that Piper has great information and stated that it was valuable.

In addition, I'm not quite sure how posting what I did meant that I "pretty obviously missed" that problem was resolved. I'm confused and feel a bit insulted. It seems that I struck a nerve and would like to know the real reason you posted what you did. Did I come across insulting or disrespectful?

 

[Mister 4x4]

Mister 4x4,

I read every word. I even stated, "I consider all of the given advice valuable." I'm not quite sure how my comment became a "good example of why it's important to read the whole thread before posting."

(snip)

I'm confused and feel a bit insulted. It seems that I struck a nerve and would like to know the real reason you posted what you did. Did I come across insulting or disrespectful?

Oh the irony - please go back and read it again... I had quoted Piper62j - not you. My quoted post only fell into the mix right after yours. While he had good information (just as you did), it appeared as if he hadn't read through to the point of seeing will e had actually fixed the issue, but offered advice (albeit, good advice) on how to fix it anyway.

I'm sorry if you were confused and felt insulted - nothing in my post was pointed in your direction. Please let me know where you saw that.

As well, to Piper62j (if you happen to see this, and just in case there are any misconceptions), I was not trying to be mean, or minimize anybody's thoughts or comments in the slightest... just pointing out something I noticed - in a friendly manner (I've seen other efforts in other places that are much less accommodating).

Hope this clears things up.

 

[mdunlap]

I'm sorry if you were confused and felt insulted - nothing in my post was pointed in your direction. Please let me know where you saw that.

"pretty obvious they missed..." This means more than one person missed. Piper and I were the only ones to comment after the problem was corrected.

I just noticed that you were a moderator so your post makes more sense now. I'm no longer confused. Feeling insulted comes with comments like "Oh the Irony." This insinuates that, once again, I didn't read the posts. No further comments on this end. I understand you better now.

 

[Mister 4x4]

I'm sorry if you were confused and felt insulted - nothing in my post was pointed in your direction. Please let me know where you saw that.

"pretty obvious they missed..." The means more than one person missed. Piper and I were the only ones to comment after the problem was corrected.

I just noticed that you were a moderator so your post makes more sense now. I'm no longer confused. Feeling insulted comes with comments like "Oh the Irony." This insinuates that, once again, I didn't read the posts. No further comments on this end. I understand you better now.

Not trying to pick a fight or stoke the fire, but the word "they" is also singularly descriptive when you're unsure of the gender of an individual (he, she, or they) - which is exactly how I meant it. If you can't see that, then I can't help you any further.

Seriously, I'm sorry for the confusion - and I'm done apologizing for this. But, if you're trying to keep this going by insinuating I have some kind of a superiority complex because of my Moderator status, then we're done here.

Have a nice day.

 

[will e]

BINGO Ign Problem Glad its Running Better!

\

I just installed a chevy type HEI for a 351c had to make a 1 inch

rubber spacer to raise the air filter to clear the huge HEI cap.

The point dizzy left me stranded when the condenser crapped out

at $50 the HEI is a steal but will not work with the stock air cleaner.

I put in Moroso cent adv spring and weight kit to get 23D adv in at 2500RPM

and this thing is a neck snapper now goodbye points! I dont use the vac

adv at all 31D all in is good enough no pinging on reg gas with 2v OC heads.

Thanks for the followup

Grab a spare HEI module. They are like 20 bucks. (DR 101 is the part number for the one I use in my AMC). There were a couple of different kinds. When they go they go dead. Easy road side repair.

 

[73vertproject]

Somehow this thread went south, taking with it a moderator and one of our members.:huh:

But word has it that relations have been restored to normal (and I'm not talking about "relations" in the Clintonesque meaning).

So let's go have a beer and bash some Chebbys, shall we? ::chili:: ::chili::

::beer::

 

[mdunlap]

Sorry for jacking up the thread guys. I should have PM'd Eric instead of airing my thoughts. He and I have touched base and resolved our misunderstanding. It won't happen again.

Sent from my iPhone using Tapatalk

 

[will e]

Interesting. It started running just a little rough at idle again and may not be as smooth as cruise. I will use my timing light RPM function again to see if any of the cyl's are misfiring. It's a handy new troubleshooting technique for me.

 

[csgt428]

Interesting. It started running just a little rough at idle again and may not be as smooth as cruise. I will use my timing light RPM function again to see if any of the cyl's are misfiring. It's a handy new troubleshooting technique for me.

Honestly....when you said it was fixed I was puzzled by your description of the "fix". I was thinking what you described would have most likely made for a wandering misfire...not specific to a particular cylinder. When I made my suggestions I wasn't really thinking/realizing that most people probably don't have "extra" parts they can just start throwing on the engine one at a time, like I can, till finding the problem(s). Of course I DO perform all the appropriate tests first to try and isolate the problem beforehand...... It's quicker/easier that way. Trouble shooting is an art...especially with intermittent problems!

 

[c9zx]

Interesting. It started running just a little rough at idle again and may not be as smooth as cruise. I will use my timing light RPM function again to see if any of the cyl's are misfiring. It's a handy new troubleshooting technique for me.

Are the carbs from a 67-69 Chevy 427? Do you have LIST numbers? I ran 3 deuces on a FORD 390 and a PONTIAC 389 back in the day. Both were sensitive to float level settings (3 of them). If I remember correctly, and I'm not saying I do, the end carbs I think you have, do have an idle circuit, even though it is not adjustable. How many turns out on the center carb Idle volume screws? Chuck

 

[Mister 4x4]

Sorry for jacking up the thread guys. I should have PM'd Eric instead of airing my thoughts. He and I have touched base and resolved our misunderstanding. It won't happen again.

::thumb:: ::thumb:: ::thumb::

Couldn't have said it better myself.

 

[will e]

Interesting. It started running just a little rough at idle again and may not be as smooth as cruise. I will use my timing light RPM function again to see if any of the cyl's are misfiring. It's a handy new troubleshooting technique for me.

Are the carbs from a 67-69 Chevy 427? Do you have LIST numbers? I ran 3 deuces on a FORD 390 and a PONTIAC 389 back in the day. Both were sensitive to float level settings (3 of them). If I remember correctly, and I'm not saying I do, the end carbs I think you have, do have an idle circuit, even though it is not adjustable. How many turns out on the center carb Idle volume screws? Chuck

I would have to go take a look at the list numbers.

And I think your are right, I think the outboard vacuums had a small idle (non-adjustable) used to make sure the gas didn't get old. (Not much of a problem with my lead foot).

They are either Corvette or Mopar.

I don't think it's the carbs. I had a beautiful two days of smoothness and now it is just starting to act a little funny again. No where near as bad as before. It's possible my two new 'hotter' spark plugs are causing an issue or it might be back to the ignition not firing correctly.

Well, at least I can drive it. Mid 70's today and not a chance of snow...

 

[csgt428]

I'm done....common courtesy and all. Good luck with the problem....

 

[will e]

Over the past couple of days it seems to be going back to running poorly. Vacuum is a little lower and a little more unsteady. Exhaust sounds a little different. The 'smell from driving' is back. It is getting progressively worse. Still no where near as bad as it had reached before. Since I have driven it over the past week and a half each day I am more 'in tune' with how it is running. It's not my daily driver and it is unusual for me to drive it more than a couple of days in a row. Over the summer it can sit for a few months with nothing more than a monthly starting and running.

That all adds up to me not recognizing it not running at 'its best'. But I got a flavor of it earlier this week. In my mind I know how it 'should' run.

Tomorrow I will check the ignition module again, give it a cleaning and see if there is any dirt there. It kind of makes sense it might get worse as it gets more dirty. We will see...