No miss at idle, but miss in gear

[BobbyFord]

...vacuum leaks...

[JMcTurnan]

http://www.secondchancegarage.com/public/186.cfm Check this out.

This is great, thanks. Mine looks more like scenario 3. Ill look at em all though

[JMcTurnan]

What does

When in gear it drops way down

mean?

If it is 18hg and drops below 16hg something is wrong, but way down could mean anything...

Is this the 351 you put the cam in? If so I would be looking at valvetrain, tight valve or perhaps lobe going bad...

Yes, it drops below 16, and it moves back and forth alot. So maybe a bad valve? I doubt its the lobe. Some of the rocker arms could have been tightened down too much. This weekend, I am going to use the torque wrench. If that works then good. If not, ill be looking at some rebuild heads maybe.

[JMcTurnan]

How can you tell it's random? Are you sitting there counting how many times a cylinder fires? I highly doubt that. Take this advice or not:

Take the advice the others here are offering you for the unbelievable price of FREE. Actually read, re-read if needed, comprehend and then attempt to try it out. Or quit asking for more advice. When you ask for help, then take none of the steps to act on the advice that others are willing to offer, and then refute what they said, it's like spitting in their face.

I'm sorry if I sound harsh, but I'm tired of nobody talking about the giant pink elephant that is sitting in the corner of the room. I was young once too, and I understand that. I learned quickly though that if you don't listen to the advice from those who are in the know, they will quit taking their time to give any of that advice.

I attemp almost everything, what I mean by at random its not like hit hit hit hit hit hit hit miss everytime, it sounds more like hit hit hit hit hit hit hit - miss hit miss miss hit hit hit hit- hit hit miss hit hit hit hit hit, hit hit hit hit hit hit hit, like it doesn't sound like there is a miss like if the spark plug was completely off is what I'm trying to say. I don't know if that makes a difference, Im just still new to engines and trying to explain it the best I can.

[cep62]

I have a major exhaust leak so its hard to hear.

So do feel this miss or just hear this miss?
If the exhaust is just blubbering out of the front pipe it's hard to tell how its running.

[JMcTurnan]

I hear it, I have always had a slight exhaust leak but not a major one. Now it's major. But I know its a miss because it makes the truck rock when it misses. I guess thats because it becomes unbalanced when it misses?

[TNIceWolf]

If you are going to try to figure out an engine JUST by ear..... and with out diagnostic tools on hand.......you are going to guess wrong more often than not. A mechanics stethescope will give you a world of info for not much. You have to treat an engine like the living breathing thing it is. As stated before......if you arent willing to go and bite the bullet and check things to their ultimate end......you arent going to get very far. Most of engine work is check.....recheck and recheck as often as needed till the problem is isolated. Guesswork really doesnt solve anything.

[Redcap]

You are going to waste a ton of money unless you learn how to think logically about a problem and to LISTEN to advice.

[JMcTurnan]

I have listened to advice, and I've tried everything you guys have told me. Right now I dont have the time to attempt to fix the problem. But Ive narrowed it down to the problem. It is the valves, it cant be anything else. It's a new cam, it has partially the same problem the last one did. Which means it wouldn't be the cam. It is timed. So I am going to try the rocker arms and adjust them again. If that doesnt fix it then I will have to rebuild the heads I guess. TNice wolf, I am not trying to guess what exactly the problem is. I by ear no that something is wrong, but I have to find out exactly what. Which in my case, from everything everyone has given me, how the vacuum goes way down in gear, and everything else that that is probably the most logical problem.

[72Highboy]

Is this the 351w you put the cam in? If so I would be looking at valvetrain, tight valve or perhaps lobe going bad...

My would be your a little off on adjustment if it is the same engine you put the cam in. It would kinda coenside with you not being able to pin point which cylinder is missing. Lets say your off just a bit on the first lob and tightening the rocker arm, then rest are going to be off a little and making the cylinder( if its the cylinders) act just a little funny.

Anyone kinda get what I am saying hope my picture helps, one more thing every book I got says that 351 have hydraulic lifters and that they shouldn't be too over tightened.

[JMcTurnan]

Well I tightened the rocker arms according to my mechanic. That seam to have a seat that the nut sits on. He says tighten them all the way down, he said it won't matter if the valve is up or not. So that what I did, i torqued them all down to the rating my book said.

[JMcTurnan]

Hydraulic flat tappet right? That what it has. It is an omc 351w boat motor. I completely get what you are saying, if one is off, than the rest will be.

[72Highboy]

Tighten them all the way down wow. Thats how they were on my brothers 351W it took 15 full turns of a ratchet to get the rocker nut off. If tomarra you going to check the clearence of the rocker arms just for sh*ts and giggles make sure its with-in specs and if you dont mind wasting 20 mins take the rocker off and check the push rod. Thats how we figured out my brothers 351W push rods were bent because the rocker arms were tightened all the way. Hope its not that way for you.

[JMcTurnan]

Yikes, me too. Well I couple I torqued right, unfortunately I always hand tightened them a little bit. And more than half torqued without even turning the nut, which meant I tightened them too much by hand. If I bent them I guess Ill just have to get new ones. Hopefully thats not the case.

[DuckRyder]

Unless they are bolt down rockers with positive stops you don't use a torque wrench on them...

Numerous links on this were posted on a previous thread... go back and read them and properly adjust the rockers and hope you didn't destroy the cam.