454 pinned at 3k rpm at WOT

Good luck with all this. Let us know what they find
 
How can I check if the secondaries are opening? Seems like an adjustment of the new carb is also in order. Fires up quickly now but settles at 750 with the occasional spike to 1100 at idle for no apparent reason.
 
If when you are in neutral you have no problem getting it to full RPM, my money is on hull and or prop growth...
 
rcknecht said:
If when you are in neutral you have no problem getting it to full RPM, my money is on hull and or prop growth...
Click to expand...

Don't do this. It will answer nothing for you unless a rod comes out the side of your block.

Your vibration under load could be caused by a dead hole as mentioned by another poster. Do you feel a vibration or hear a miss at idle while in gear? If your low idle rpm was set while running on 7 cylinders, then the surge to 1100 is probably that 8th hole cutting in and out.
An easy way to identify which cylinder is missing is to cancel one cylinder at a time and check for rpm drop. The bad hole will have little to no change. If you have a test light you can clip it to the engine block and carefully slide probe end along wire into back of the spark plug boot. If you identify a bad cylinder, swap plug and wire with known good cylinder and see if it follows. If it doesn't then a timing light clipped to that lead will help rule out everything upstream and compression must be checked. As others have mentioned an intermittent problem with coil or ignition module could also be an issue. This would likely be indicated with the timing light not firing. If all cylinders drop the same then you will have to go thru the other checks previously suggested. A vibration can also be caused by a warn coupler, ujoints or gimbal bearing with the outdrive trimmed.
 
Before my 290, I had a Larson 270 with a VP 7.4.
All of a sudden, I couldn't get it past 3000rpm in gear on the water.
Turns out one of the exhaust flappers came loose and was stuck in the Y-pipe.

Just a thought!

Jeff
 
Really appreciate all the feedback guys. Took a short video of the engine fluctuating idle yesterday, not sure it'll help but here ya go.

[video]https://youtu.be/-APAyaYwXDg[/video]

It doesn't start surging until about 25 seconds in.
 
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It's hard to say if I notice a miss at idle because I am very hard of hearing. When you say cancel one cylinder at a time I assume you mean pulling one wire at a time with the engine off and then starting to see what it idles at and if there's a significant drop in RPM's. This is a bad idea to do while the engine is idling correct lol? What would the drop in RPM's be, are we talking 50 or 200? Thanks again for all the suggestions. Its getting harder to keep throwing money at this old bull.
 
Sorry if this all comes across a little hash. A clean bottom will thank you later but is not going to fix this. Your motor sounds horrible. Is your "mechanic" the person who has done all these repairs so far? If that is the case, you should do yourself and your pocket book a favor and find someone a little more competent. These engines are as about as simple as they come. If you were near by, I would be happy to help you with it. Maybe someone here can recommend someone close to you.
 
Thornton69 said:
Sorry if this all comes across a little hash. A clean bottom will thank you later but is not going to fix this. Your motor sounds horrible. Is your "mechanic" the person who has done all these repairs so far? If that is the case, you should do yourself and your pocket book a favor and find someone a little more competent. These engines are as about as simple as they come. If you were near by, I would be happy to help you with it. Maybe someone here can recommend someone close to you.
Click to expand...

I agree with this, after hearing your engine... My money is no longer on the bottom fouling....
 
Thornton69 said:
Sorry if this all comes across a little hash. A clean bottom will thank you later but is not going to fix this. Your motor sounds horrible. Is your "mechanic" the person who has done all these repairs so far? If that is the case, you should do yourself and your pocket book a favor and find someone a little more competent. These engines are as about as simple as they come. If you were near by, I would be happy to help you with it. Maybe someone here can recommend someone close to you.
Click to expand...

No offense taken. Yes my "mechanic" has done all of the work. He was recommended to me by a family member however I haven't exactly been satisfied. Can you elaborate on what sounds horrible? Any thoughts after hearing it what it may be? Thanks for the help. The frustration level is off the charts at this point.

Thanks
 
My money is still on the ICM. It's acting the same as mine when it went.

we to thought it was fuel so we rebuild the carb and changed filters.
replacd the coil thimking low spark.
replaced the cap, wires, plugs, pickup, and yes did a compression check.

check the wiring first double check the connections. Don't let this thing frustrate you, it's going to be something simple and stupid.
 
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Any way to tell if its the Ignition module or the ignition sensor?


dwna1a said:
My money is still on the ICM. It's acting the same as mine when it went.

we to thought it was fuel so we rebuild the carb and changed filters.
replacd the coil thimking low spark.
replaced the cap, wires, plugs, pickup, and yes did a compression check.

check the wiring first double check the connections. Don't let this thing frustrate you, it's going to be something simple and stupid.
Click to expand...
 
Best way to do that would be to go online and look at the procedure. I got lucky, I have twins

with the things you say you've done, check the connections first. Unplug and check its pins. Then plug it back in
 
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First things first, before you monkey with anything check the health of your engine with a compression test, then proceed
 
Update : did a compression test this afternoon and all 8 came back within range of 110-120. Changed the spark plugs. See the attached pictures, these are the plugs after only a few hours of run time. Is it me or does it look like I'm running super rich ?

As always, appreciate the feedback.
b6bfc7046a19718cf0734a1c2b96247c.jpg
e10525adbbf721e62c7ca876af0ca833.jpg


Sent from my SM-P600 using Tapatalk
 
Jwing128 said:
No offense taken. Yes my "mechanic" has done all of the work. He was recommended to me by a family member however I haven't exactly been satisfied. Can you elaborate on what sounds horrible? Any thoughts after hearing it what it may be? Thanks for the help. The frustration level is off the charts at this point.

Thanks
Click to expand...
Your engine sounds sick as is reflected by the performance you are reporting. The video has a lot of noise in it and it is hard to make out what it all is. I hear belt chirps, echoes and a tick to slight knock. This can be from a simple exhaust leak, bad valve timing (too tight or loose) or faulty ignition. At 750 rpm a V8 has cylinders firing 50 times per second. Properly tuned, it should be smooth to sound and touch. My comment (concern) is due to the list of repairs and parts you have thrown into it with presumably little to no improvement. With an older engine, the parts were probably justifiable but did not fix your problem. This is where my competence concern came from. Proper diagnostics will eliminate component that are functioning correctly. There has been many legitimate questions and comments brought up by members here without a clear response. I would suggest going back and rereading from the beginning. There has been several different experiences shared.
You did your compression test which looks to have respectable results. This is a good indication your cylinders are in decent shape. It is only cranking speed though and may not indicate correct lifter adjustment. Your (new) plugs indicate a rich burn. Why is there only 6 in your photos? Were gaps confirmed before they were installed? Did you confirm the correct choke operation someone had brought up? Your surge is strange. I would bet it is either a vacuum leak or faulty ignition system.
Here are a couple easy things you could try.
External vacuum leaks can easily be identified with lightly spraying something like wd40 near the obvious places below throttle plates at carb base and where intake meets head at idle. Watch for rpm to increase. Internal leaks probably a bit more difficult. Could try removing the vent lines on the valve covers, blocking them and put a vacuum gauge on the dipstick tube. It should not show vacuum.
I have not ran into the ICM issues that others have mentioned that would cause a surge like you are getting. If the timing is up and down then it would cause a surge I would think. Intermittent spark will without doubt. To check for erratic timing/spark, I would take a paint pen. Mark the dampener in four places 90 deg from each other starting at the 10 deg before top dead center mark. Run the engine at idle and check the timing (with light) at each spark plug lead. Check for an intermittent spark or inconsistent position of your paint mark.
If you can tie yourself to the dock good, then doing these tests in gear will add a light load and may help identify things quicker. Use your judgment on that one.

Your mechanic should be able to justify what he is doing and why. If your guts don't sit well then you should listen to them. Hope you can get this figured out quick and enjoy the water.
 
Compression is on low side and the fresh heads will only put more pressure on your old rings increasing blow by. Is that carbon dry or sticky with oil ? Looks to be running pig rich. Have you adjusted the carb properly ? Try turning those idle mixture screws in.
 
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