Mercruiser 7.4 MPI Valve Job . . .

tpenfield

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I got my inspection camera 'thingy' this weekend. Tested it out on a few things around the house. Looks to be OK. . . the camera piece itself will definitely fit inside the spark plug hole of any engine. The software is a bit wonky, but it is workable.
 

alldodge

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Look forward to the deep pics, as Scott pointed out be gentle :rolleyes:
 

Scott Danforth

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Tail_Gunner's snake oil mix (AF/Acetone) is the bomb. forgot about it for decarbing.

FYI - is also what a few grey beard mechanics I know used on old flat-heads to get the head bolts out without breaking them. drain the cooling system, fill with the "magic elixir" run the motor until it is hot. let it sit for a day. repeat. then simply drain the cooling system (reclaiming the AF/acetone mix for another use), then unbolt the heads.
 

tpenfield

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I ran some more SeaFoam through the engines today . . . This time I actually sprayed the seafoam into the cylinders via the spark plug holes. I did this at about 20 degrees BTDC on the exhaust stroke and 20 degrees ATDC on the intake stroke for each cylinder. So, 2 bouts of spray for each cylinder. My hopes were to get the spray into the combustion chambers while the valves were open, in hopes of getting a fair amount of liquid on the valve seating surfaces.

Then I ran the engines for a while . . . lots of smoke on start-up (oil in the seafoam burning off). Then I ran some water spray through the engines as well. I'm not sure how much water I should run into the engines in order to provide sufficient 'steam cleaning'. I have been setting the engine at about 2500 rpm and then injecting water into the intake via a 'mist' nozzle. I give it an amount of water to where I can hear the engine laboring a bit . . . probably reduces the RPM down to about 2K.

I used my endoscope to take some pictures and videos of the combustion chambers. I did not have enough time to run another set of compression or cylinder leak tests. I checked a few cylinders and it looks like there is still some carbon buildup on the piston and valve bases.

So, maybe I'll try the Acetone and ATF blend in the spring, just to see if I get any better results :noidea:

Here is a video of some of my viewing of the cylinders. . .


I may get a chance to run another compression test over the Thanksgiving weekend, since I tend to avoid Black Friday, etc.
 
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alldodge

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Think your engine should be in good shape for the hours she has
 

tpenfield

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Think your engine should be in good shape for the hours she has

Yup, they seem to be OK. I am just wondering what it takes to get more of the carbon out of the combustion chambers. The video imagery that I took is not that great (guess I should have gotten the "Hi Def" version of the borescope), but I could see carbon pretty much all over the combustion chamber. The valve seat surface (from what I could see) looked OK.

The Starboard engine is original, whereas the port engine had a valve job at some point. So, there seems to be lots of buildup in the starboard engine.

If I can run a compression test over the holiday(s), then maybe (maybe) I can see if the additional treatment(s) are making any measurable difference.
 

alldodge

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Yup, they seem to be OK. I am just wondering what it takes to get more of the carbon out of the combustion chambers. The video imagery that I took is not that great (guess I should have gotten the "Hi Def" version of the borescope), but I could see carbon pretty much all over the combustion chamber. The valve seat surface (from what I could see) looked OK.

The Starboard engine is original, whereas the port engine had a valve job at some point. So, there seems to be lots of buildup in the starboard engine.

If I can run a compression test over the holiday(s), then maybe (maybe) I can see if the additional treatment(s) are making any measurable difference.

Opinion time: Getting the carbon out is always a good thing, but hope it doesn't cause other issue in the process of doing so. In years back I use to use a garden hose and have the engine revved up and pour water down the carb. It works pretty well but some of the carbon build up on an old engine can also help seal some weak areas. So after all the cleaning if your compression goes down this may be what has happened, hope it doesn't.

I'm still in favor of steam cleaning but only a little with an old engine. Most all carbon is caused by an over rich mixture and oil. So getting the fuel ratio correct and replacing valve seals will allow the engine to clean it self up. When Eddie took my engine apart GM appears to still use the cheap hard plastic valve seals, they will be replaced with rubber ones.
 

tpenfield

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Yea, the last thing I want to do is mess up the engines. The carbon may be holding them together :D

Given that I have done a couple of treatments, I'll see how the compression tests and leak tests look. I need to have longer weekends, as I don't seem to get everything done that I have planned - the shorter day light this time of year does not help, either.

I have only used a fine spray of water (mist nozzle) for fear of dumping too much water into the engines all at once, and causing a hydrolock, which at the usual engine speed for this process, 2500 RPM (+/-), would probably bend the connecting rods.

Maybe I'll do the water thing on an annual basis.

The starboard engine seems to be running rich, based on how the spark plugs looked after the season. The port engine plugs looked good.
 
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Tail_Gunner

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If you do that mixture i would test some current valve seal's..grommets making sure it does not degrade them. You will never clean the internal's with just water a good three 3 or 4 day soak will soften up the carbon and hopefully free any stuck ring's. Follow that with your water process and you may get lucky. Marine engine's run cold as you know and very rich so at the end of the day it might work. At least you will have very shiny combustion's chamber's....:D
 
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tpenfield

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Yea, I was not seeing anything 'shiney' with the borescope, except the edges of the valves. So, even though I saw some improvement on the compression test after the first treatment, it looks like there is still some build-up remaining after the second treatment. Maybe it just needs to sit there longer as you say. I gave it an hour, then fired the engines up. BTW - the cloud that initially emerges from the engines seems like it would be a good way to get rid of mosquitoes during the summer :D

If I try your ATF/Acetone cocktail, I may just stay away from the valve seals for now and focus on the combustion chambers.

Won't really know the next step(s) until I run another compression test, which hopefully will be in the next week or so. After that it may be too cold to run the engines. If we get any snow, then I'll have to forgetaboutit until spring.
 

Bondo

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Yea, the last thing I want to do is mess up the engines. The carbon may be holding them together :D

Given that I have done a couple of treatments, I'll see how the compression tests and leak tests look. I need to have longer weekends, as I don't seem to get everything done that I have planned - the shorter day light this time of year does not help, either.

I have only used a fine spray of water (mist nozzle) for fear of dumping too much water into the engines all at once, and causing a hydrolock, which at the usual engine speed for this process, 2500 RPM (+/-), would probably bend the connecting rods.

Maybe I'll do the water thing on an annual basis.

The starboard engine seems to be running rich, based on how the spark plugs looked after the season. The port engine plugs looked good.

Ayuh,.... For the steam cleanin' to work, ya need a warmed up motor, turnin' 'bout 1500 rpms or so,....

Then dump a 16oz. soda pop bottle of water down the throat of the carb,...
Ya need to pour it fast enough to "Labor" the motor,....
The neck of the bottle helps ya regulate it, ya almost can't pour it too fast, as the bottle gulps for air,...

I learned the trick way back in my British years,... 1st Austin Mini's, 'n later Series Land Rovers,...
It's right from the British Leyland Shop manuals of the day,....

I've done it on a few motors I knew were bein' torn down for repair(that still ran)...
The combustion carbon is Gone,... Clean cast iron, steel, 'n aluminum,.... Nothin' to clean up after the tear-down,... ;)
 
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tpenfield

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Ayuh,.... For the steam cleanin' to work, ya need a warmed up motor, turnin' 'bout 1500 rpms or so,....

Then dump a 16oz. soda pop bottle of water down the throat of the carb,...
Ya need to pour it fast enough to "Labor" the motor,....
The neck of the bottle helps ya regulate it, ya almost can't pour it too fast, as the bottle gulps for air,...

I learned the trick way back in my British years,... 1st Austin Mini's, 'n later Series Land Rovers,...
It's right from the British Leyland Shop manuals of the day,....

I've done it on a few motors I knew were bein' torn down for repair(that still ran)...
The combustion carbon is Gone,... Clean cast iron, steel, 'n aluminum,.... Nothin' to clean up after the tear-down,... ;)

Thanks, Bondo. I appreciate your voice of experience. I think that I was going a little too light on the water for fear of hydrolocking, and probably did not get enough water going through the engine. It would be really awesome to see clean metal in those cylinders.
 

tpenfield

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Come to think of it, my MPI engines have the air intake on the sides of the plenum . . . So pouring the water in isn't so easy. I have been spraying it into the intake with a spray nozzle from the hose, set to a fine mist. Probably has not been enough of a spray.

Maybe I can change that up a bit to get some better results.

What is the octane rating of water? I am also wondering if it turns to gas on the compression stroke or the power stroke . . . ?
 

alldodge

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I don't see you being even able to hydrolock your engine spraying as you mentioned. As previously posted I used to use a garden hose and while it did gush it did go in pretty heavy. The motor was warmed up and I would even get the rpm above 3500 and pour it in to where it was struggling to keep running. It only died once doing it but a bit more fuel and it fired right back up

EDIT: I'm not so sure you can do the same type cleaning with an MPI
 
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alldodge

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Here is something I just thought of. Your plenum is about 1.4 inch thick. The runners stick up inside the plenum about an inch inside, By spraying water into the throttle body not all the water will make it down the runners. Some of the water could wind up in other areas like the oil pan, vacuum lines and pressure regulators. Might want to think about this a bit more
 

Scott Danforth

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Have you tried GM's upper engine cleaner?


Here is a step-by-step from one of the Guru's on a caddy northstar forum I have book marked for my N-star Opel GT project



My suggestion
  1. Drain the oil first Not the filter.
  2. Leave the drain plug out.
  3. Blow off intake around the fuel injectors.
  4. Remove the fuel injctors.
  5. Add 2oz of the UEC to each cylinder through the injector holes.
  6. 16oz bottle 8 cylinders.
  7. Mark the balancer just as a reference.
  8. Turn the crank 720° by hand.
  9. This will push the cleaner into the piston ring lands.
  10. If you do this from the bottum you will see the cleaner run out the oil pan.
  11. Let the chemical set for 1 & 1/2 hours.
  12. Add 2oz of UEC to each cylinder for a second time.
  13. Turn the engine over 720° again by hand.
  14. If you need to work it back and forth to get it to go over.
  15. You should be close to or hydo lock on each cylinder.
  16. Let sit another hour.
  17. Spin engine over by hand until free. 720°?
  18. Add 1 quart oil and let it drain out.
  19. Install drain plug back into the oil pan.
  20. Fill with oil.
  21. Reinstall the fuel injectors.
  22. Start the engine and let it idle until it reaches operating temp.
  23. Drive the car in first and second gear keeping the RPM's above 3500 for 10 minutes.
  24. Perform many WOT launches.
  25. Change oil and filter.
Parts list
2 UEC
16 quarts of oil

This was followed a few months later by

GM has now picked up on my proceedure. Well kind of. I have you pull the intake and add the cleaner to the intake ports. Then turn the engine by hand. Then let it sit for 3 hours.
  1. Verify the oil consumption concern following Corporate Bulletin Number 01-06-01-011F. If oil consumption is found, continue on with this bulletin.
  2. Remove the spark plugs and ensure that none of the pistons are at top dead center (TDC).
  3. Clean the pistons by putting 118-147 ml (4-5 oz) of Upper Engine and Fuel Injector Cleaner, GM P/N 88861802 (in Canada, use 88861804), in each cylinder. Allow the material to soak for at least 2.5-3.0 hours, but no more than three hours and then remove the cleaner. A suggested method of removing the cleaner is cranking engine over. Make sure to unplug the ignition coils and fuel injector before cranking the engine over. Also make sure that the painted surfaces are covered so no damage is done.
  4. Reinstall the spark plugs. Replace the spark plugs if necessary due to full of carbon. Refer to the parts catalog.
  5. Change the oil
  6. Re-evaluate the oil consumption. Document on the repair order. If the oil consumption is still greater than 0.946 L (1 qt) in 3,200 km (2000 mi), replacement of the pistons and rings will be required.
 

tpenfield

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That is too many steps for me, but thanks anyway. . . . however, I think I did a few of those steps this past weekend.
 
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tpenfield

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Here is something I just thought of. Your plenum is about 1.4 inch thick. The runners stick up inside the plenum about an inch inside, By spraying water into the throttle body not all the water will make it down the runners. Some of the water could wind up in other areas like the oil pan, vacuum lines and pressure regulators. Might want to think about this a bit more

Good point . . . I have been spraying a fine mist and running the engine at 2500 RPM. also running for about 5-10 minutes after the water just to clean things out. I would hope that any water not immediately making it down the intake ports would be evaporated and consumed during the time that I continue to run the engine . . . . not sure, so point well taken.
 

tpenfield

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Quick Update:

I plan to do one more decarb with water tomorrow (Sunday) and then do another set of compression tests and cylinder leak tests. After that, a final winterization process. Today, I made a 'mist sprayer' to do the decarb from the hose and I shopped around for more winterizing supplies.

Since I have a full closed cooling system on the engines, winterization is not too bad . . . run some AF and then drain the heat exchanger. I did shop around to get the -100 F variety of the antifreeze, based on my freezer test of the -50 F stuff. I have a sea water strainers that I usually remove for the winter to prevent freeze damage, but I may just leave them in place having used the -100 F stuff.

I thought I would start a new thread on the decarb and compression test, since it does not look like I will be doing a valve job . . . for now. :)
 

alldodge

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Quick Update:

I plan to do one more decarb with water tomorrow (Sunday) and then do another set of compression tests and cylinder leak tests. After that, a final winterization process. Today, I made a 'mist sprayer' to do the decarb from the hose and I shopped around for more winterizing supplies.

Since I have a full closed cooling system on the engines, winterization is not too bad . . . run some AF and then drain the heat exchanger. I did shop around to get the -100 F variety of the antifreeze, based on my freezer test of the -50 F stuff. I have a sea water strainers that I usually remove for the winter to prevent freeze damage, but I may just leave them in place having used the -100 F stuff.

I thought I would start a new thread on the decarb and compression test, since it does not look like I will be doing a valve job . . . for now. :)

Maybe next year use the Sierra antifreeze, cost 8 bucks a gallon and is made to be diluted 50%

http://www.tractorsupply.com/en/store/sierrareg;-automotive-antifreeze-1-gal
 
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