MisFire above 4000RPM after 20 min

It newer helped me thats for shure so I agree with Jack here.

Higher rpm has produce more heat that has to escape trough the cylinderwalls at a smaler timeframe witch is imposible and therfor instead increase the temperature.

Depends on several factors, if you do a compresion test on all cylinders they are seldom the same, but has a smal diference. Also the shaping off the manifoils will in moust cases favor some cylinders filling over others. Hopefully you did not develop a hot spot.

pre detonation does not come from the rocker boxes and could not be desrcribed as a knocking, more of a tinkling.

Lets hope not since this is suposed to be a new engine right?

I can't remeber we ever came to the conclution that it's only 1 cylinder.

Did you do anny changes? And how did it work out?

 

Not sure who or what gave the indication of one cylinder down during this thread. When it happens it feels like 4 are down LOL. Its a very scary noise along with loss of power that will last until I back down.

No changes done yet. Wife has me doing kitchen floors.

I want to soon but lack of time has prevented such.

Could I be running lean?

If yes would running lean along a mixed bag of problems casuse this high RPM/High load misfire / noise?

 

Using quotation as this might ave encouraged me.

 

That is sooo sweet.

I know what it feel's like

 

So I guess it was me that indicated single cylinder. Thanks JF

Regards

Kevin

 

Cut me some slack Stian, She is the boss right?

How about on your end?

 

A man that claim he's the boss is not a honest man

I'm her *****. You have no idea what she make me wear

 

Wow,

Weather is nice hear. Wish I was on the lake.

I know what’s going to happen and that is she will make me finish this kitchen project this week and will want to go on lake all weekend. I am scared to tell her I spent over 2K USD on engine and she’s not right.

I am somewhat reluctant to tell her the possibility exists of major work that will put the boat down until fixed.

No money to have someone look at it for me nor do I trust the local marina mechanics.

Ugh! Where did I go wrong Stitan. LOL

 

It would appear that you have 2 major problems. However I think that niether of them can be solved untill you get off your knees.

Now that we have a glimpse into your financial situation it is becoming more evident that your wife would be correct in her assumption of irresponsable spending.

You could try staying on your knees and find other kitchen projects, or get up stand tall,-- grab the keys for the boat and the car---and ---
naaa----- stay on your knees!!!!

 

Kevin,

This may sound a bit at odds with the previous focus on misfires, but I was wondering if the noise might actually be caused by metal parts tapping or banging. This link discusses a problem that sounds like it might be similar to yours: http://findarticles.com/p/articles/mi_qa3828/is_200408/ai_n9453109 .

A few questions and observations that might help in diagnosing:

Exactly where does the noise come from and how many cylinders are affected? One way to tell, if you can arrange for someone to run the boat or listen while you run it, is to listen with a mechanic's stethoscope. A long screwdriver will do in a pinch; touch the blade/probe to the valve cover and hold the handle to your ear. Move the listening device along the valve covers while the noise is happening. It will become obvious if it is limited to one or two cylinders, or all on one bank, or all cylinders.

Try touching the noise probe to other parts of the engine. Wherever the noise is loudest is the source.

You said your engine had 21 hours on a "fresh 350 Vortec"; later you said new wires, plugs, rotors, etc. If the engine is "fresh", does that mean a new or rebuilt engine? In that case you might have a warranty issue.

The problem discussed in the link may be what you have. A restriction of oil flow will quickly result in loud metalic noises. Draining the oil and checking for particles that shouldn't be there can be instructive. If you can't drain the sump, like many marine installations, put a narrow magnet on a rod down the dipstick tube and move it around as much as possible. A few powdery grains of metal are OK, anything larger could be the source of the problem if ir's somehow restricting oil flow. Metal bits larger than a grain of powder, howver, could be a symptom of a bigger problem.

 

Sounds like ignition breakdown.

 

Hilarious.... True!

 

One thing to mention concerning oil is I have performed 3 oil changes now following this problem. I cut all three filters open and 1st one had about 10-15 very small particles along with build up of metallic dust at filter folds.

The second oil change and filter opening was at 15 hours time since rebuild and same dust in folds but negligible.

Most recent one performed at 21 hours has no debris at all.

Compression check performed at 15 hours was:
#1:190 psi #2:190 #3:180 #4:184 #5:182 #6:185 #7:187 #8:188

As I mentioned once I finish the honey due I will borescope cylinders and look for metal to metal contact. Wish I had a place to post pictures on this forum.

The engine is in fact in warranty but would require a reason for which none exists at present. Borescope of cylinders may prove otherwise.

Thanks

Kevin

Oh I will read the artical link. Thanks again

 

Thats what I thought but replaced all once again since start of problem. That is with the exception of spark plugs, distributer and thunderbolt 4 computer box/module. Cap, Rotor, Wires are new.

I do still think it is ignition but noise is louder than spark leakage and where would it be coming from?

Very similure sound though...

I thought of someting real strange. What would happen with poor contact of distributer to ground cause?

I already had to remove paint to get oil pressure, water temp to work. This was due to the thick paint causing no ground for sending units. Also had to scrap massive paint from head to get starter and ground wires to make contact.

 

get a stethiscope,,this will give you somewhat of an idea of wear the sound is originating from,.