Worst first drive ever.....

[LONGHAIR]

Originally Posted by Frkypunk70

Also are you sure your not 180 out on your distributor that alway caused a lot of popping for me. I didn't see that anyone had mentioned that.
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Physically Impossible.........He says that it runs, just pops and bangs. If the timing was 180 degrees out, it would not run at all...

I'm with the others who have suggested that the valve covers need to come off. It sure seems like a valve issue to me. A bent, loose, or "off" pushrod could cause this,as well as bent or broken rocker arm. The most likely though is a flat cam lobe9 (or 2)

[72TealnWhite]

thanks for all the tips and hints... I believe i have tried everything as far as timing and carb... I'm confident i'm dealing with a valvetrain issue here... the next step is to vac the cylinder... basically pinpointing the valve and or cylinder that is bad.. its obvious its on the driver side.. so i think i'm almost there... No to thrilled with the idea of a worn cam.. hoping for a stuck valve... that was originally diagnosed by a friend of mine ... used some oil additive to unstick the valves... i guess ill see what's up tomorrow...


Just really disappointed in the previous owner"

I was told.. original motor ... rebuilt with 14,000 miles on it
wtf: 14,000 miles of cracking and popping down the road and blowing manifolds ... thats what happens i guess.


nate

[LONGHAIR]

If it has been doing it the whole time, it may have the valves adjusted too tight. That can hold one (or more) open when it is supposed to be seated.That can cause a pop too.

[68 TT]

Originally Posted by LONGHAIR

If it has been doing it the whole time, it may have the valves adjusted too tight. That can hold one (or more) open when it is supposed to be seated.That can cause a pop too.

x2

Every engine I have had likes a different amount of preload on the lifters to make it run the best. None have liked much beyond what is needed to quiet down the lifter clatter, maybe 1/8 turn more on average.

Try adjusting the valves with a vacuum gauge on it to see what gives you the best vacuum.

[jhwkns]

Originally Posted by Frkypunk70

.... Popping through the carb means that it's definitely valve related.....
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^not true

Could be right about the flat cam though.

Sorry 'bout your truck Nate. It seems that you've ruled out fuel, and ignition as your problem. If that's the case then it has to be a mechanical issue. Have you done a compression test?

Learn how to do some things yourself. Your truck dollars will go much further when you're not paying a mechanic. G/L

[LONGHAIR]

Originally Posted by Frkypunk70

Popping through the carb means that it's definitely valve related.

Originally Posted by jhwkns

^not true

Could be right about the flat cam though.

How is a flat cam not valve related? It does open and close them

[Frkypunk70]

Originally Posted by jhwkns

^not true

Could be right about the flat cam though.

Sorry 'bout your truck Nate. It seems that you've ruled out fuel, and ignition as your problem. If that's the case then it has to be a mechanical issue. Have you done a compression test?

Learn how to do some things yourself. Your truck dollars will go much further when you're not paying a mechanic. G/L

Aren't the two related? If you have a worn cam it is not opening the valves properly. It's kind of a domino effect. Or if you have a loose or overtightened rocker arm. Or if you have a stuck lifter. They all affect the valve.
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[jhwkns]

Originally Posted by LONGHAIR

How is a flat cam not valve related? It does open and close them

Originally Posted by Frkypunk70

Aren't the two related? If you have a worn cam it is not opening the valves properly. It's kind of a domino effect. Or if you have a loose or overtightened rocker arm. Or if you have a stuck lifter. They all affect the valve.
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Read it again guys.
Originally Posted by Frkypunk70
"Popping through the carb means that it's definitely valve related."

There are several things that will make an engine backfire through the carburetor.

[Frkypunk70]

Originally Posted by jhwkns

Read it again guys.
Originally Posted by Frkypunk70
"Popping through the carb means that it's definitely valve related."

There are several things that will make an engine backfire through the carburetor.

Ok. Give me an example of popping through the carb does not have something to do with a valve then.
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[BMERDOC]

Not wnting to jump in the middle of an argument but who was the last guy here to dance around a carb fire when first starting a new engine because his ignition timing was off? Carb backfires occur for multiples reasons. Remember, the distibutor is driven of the cam and the cam is driven off the crank.

[Frkypunk70]

Originally Posted by BMERDOC

Not wnting to jump in the middle of an argument but who was the last guy here to dance around a carb fire when first starting a new engine because his ignition timing was off? Carb backfires occur for multiples reasons. Remember, the distibutor is driven of the cam and the cam is driven off the crank.

Yes I agree but popping carb says valve not opening when it should ( no matter what the reason) Depending on which valve it could also pop out the exhaust.
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[BMERDOC]

Ive been sitting here with my imaginary push rod V8 running. If all ignition related items have been eliminated its either a worn cam lobe (exhaust) or a burnt, stuck intake valve. Depending on how bad the backfire is (popping or backfire) you should be able to hold it off idle (1600 rpm) and notice it is rythmic. Either way its not good. I'd rather have a wiped cam. If its a pop then its gotta be unspent compression entering the intake manifold, if its a backfire then the intake valve is not sealing and the ignition process is escaping into the intake. A worn intake valve spring wouldn't normally show up until higher in the rpm range in my imaginary engine because it should still have enough tension to hold the valve correctly. Again, a vacuum gauge would show this defect but it happens too quickly to isolate the cylinder. A static, then a dynamic compression test would be in order after that to determine the cylinder.

[Frkypunk70]

Originally Posted by BMERDOC

Ive been sitting here with my imaginary push rod V8 running. If all ignition related items have been eliminated its either a worn cam lobe (exhaust) or a burnt, stuck intake valve. Depending on how bad the backfire is (popping or backfire) you should be able to hold it off idle (1600 rpm) and notice it is rythmic. Either way its not good. I'd rather have a wiped cam. If its a pop then its gotta be unspent compression entering the intake manifold, if its a backfire then the intake valve is not sealing and the ignition process is escaping into the intake. A worn intake valve spring wouldn't normally show up until higher in the rpm range in my imaginary engine because it should still have enough tension to hold the valve correctly. Again, a vacuum gauge would show this defect but it happens too quickly to isolate the cylinder. A static, then a dynamic compression test would be in order after that to determine the cylinder.

So what you are saying in that in lamins terms is that it's still a valve?
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[BMERDOC]

If diagnosis eliminates ignition, then yes, valve events. I had to take a time out and listen to you and those who would agree with you because I was too focused on timing. I did not focus on what effect an improperly sealing (and unsealing) combustion chamber would have on an engine.

[Frkypunk70]

Originally Posted by BMERDOC

If diagnosis eliminates ignition, then yes, valve events. I had to take a time out and listen to you and those who would agree with you because I was too focused on timing. I did not focus on what effect an improperly sealing (and unsealing) combustion chamber would have on an engine.

Thank you , someone who understands the how a combustion engine works. I only answered this because I thought I could help someone.
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[BMERDOC]

In my line of work stubborness should not be in my vocabulary. I am never afraid to say I am wrong or not completely right. Time is money and all input should be evaluated to come up with the correct answer. I work around a lot of smart people who give smart feedback. Listening to someone else should be held in high regard.

[Sillyoldman]

Sorry if this has already been stated but I'm too tired to read the thread. I'd find TDC and drop the dist again. I think the issue is most likley in your heads. Properly adjust the valves (not running) or at minimum check for a loosened rocker nut. If it backed off, replace it. It will just back off again.

[jhwkns]

Originally Posted by Frkypunk70

Ok. Give me an example of popping through the carb does not have something to do with a valve then.

That's simple. Bad spark plug wires will do it.

You stated that it was definitely a valvetrain problem. That's just not true. You're ruling out everything else. I even agreed with you that it could be a flat cam. I just can't rule out definitely that it's not something as simple as a cracked distributor cap, or a stuck choke on a carburetor. You can't be absolutely sure. You are likely correct that it's a valvetrain issue. It's just not definite. Nobody can diagnose the problem over the internet. They can only speculate. Hopefully for Nate's sake it's something simple.

[72TealnWhite]

the results are in.. 2 bent push rods.. Not too bad.. Compression is fine.. everything seems to be on the up and up. Pop the heads off and do a little refurb job on those and Hopefully i have a smooth runner ..

Thanks all for the information.. you were right there with me with some stellar diagnosis... Thanks again..

cant we all just get along

nate

[BMERDOC]

Ok, valve events.. Happy to see it got figured out! Do a burn out for me when you get it back!!

[68 TT]

Originally Posted by jhwkns

That's simple. Bad spark plug wires will do it.

You stated that it was definitely a valvetrain problem. That's just not true. You're ruling out everything else. I even agreed with you that it could be a flat cam. I just can't rule out definitely that it's not something as simple as a cracked distributor cap, or a stuck choke on a carburetor. You can't be absolutely sure. You are likely correct that it's a valvetrain issue. It's just not definite. Nobody can diagnose the problem over the internet. They can only speculate. Hopefully for Nate's sake it's something simple.

I agree. Timing being off can make it backfire through the carb too.

My Camaro will pop & backfire through the carb if it doesn't have enough advance. Too much compression and cam to run less than 8 degrees. I tried to take enough timing out of it to get it to run on 87 unleaded pump gas but it won't let me back it off enough to do it.

[68 TT]

Originally Posted by 72TealnWhite

the results are in.. 2 bent push rods.. Not too bad.. Compression is fine.. everything seems to be on the up and up. Pop the heads off and do a little refurb job on those and Hopefully i have a smooth runner ..

Thanks all for the information.. you were right there with me with some stellar diagnosis... Thanks again..

cant we all just get along

nate

They don't tend to bend for no reason so you need to check for interference at the head pass thru holes and for rocker arm slot binding.

Chances are the stock rocker slots are hitting the rocker studs at full lift and the push rods are bending as a result. Too much cam for the stock rockers will do this. Sometimes it breaks a rocker and others it bends push rods.

Get a full set of new push rods and a set of 1.5 ratio long slot rocker arms and you should be on the road again without having to do anything to the heads.

A set of 1.6 rockers most times will require head machine work to make the push rod hole elongated enough to clear. If you are going to have the heads done then have them slot the push rod holes while they are at it so you have the option of running the 1.6 rockers later if you want.