Electrodes gone from spark plugs??
 

I need some input please. I have one engine that has two spark plugs, AC MR-43-T, that have lost the electode on separate occasions. The engine has not ever run correctly. It starts to pop out the exhaust, after anything over 3000 rpm, when it warms up, and has progressively gotten worse, missing while idling and dieing while docking. It finally would only run on about 5 cylinders (seemingly). I pulled the plugs and found the electode missing. Pulled the exhaust and valve covers. All the Crane roller rockers had lash except one. This is a Crane 134561 grind# H-296-2 Hydraulic. I am running stock Merc distributor and a V6-14° module.

I was expecting a valve hanging or too tight. (This motor was basically new, but assembled before I purchased it.)

It appears all the rockers except one are loose. It might be the one that is not loose that is loosing the electrode #4 cylinder.

Does this scenario turn on any light bulbs in someones closet of information?

I plan to adjust the valves 1/2 turn down from drag on the push rod and try it again.

I hope this makes sense to someone. I'm tired and want to get this fixed quickly. :)

Jim,
Is this a blower motor? What is your max timing? What carb? & jets are you running? What is the compression ratio?
Your motor is either too lean or has too much timing or bad gas. Colder plugs may help.
This is a serious problem, but not that hard to fix, however you may have more damage. Like burned valves or piston damage.
Run a compression test. If it's gone, you may have to fix the heads or worse.
Give us some more information.
JB

Were the burnt plugs tight --- A loose plug will do that. If not then you have a lean condition. Maybe from a valve hanging up. That valve with no lash-- loosen up the rocker and see if it is the same height as the other valves. Also see if you can push it down and then it returns all the way up freely. You can get a tool to compress the valve. Or put that cylinders piston at the top and just remove the valve spring and see if the valve will move freely in the guide. If you move the piston down slightly you will be able to open the valve all the way. Just don't let it drop below the point where you can pull it back up. DON'T USE THE PISTON TO PUSH THE VALVE BACK UP. A hanging open valve can cause a lean condition.

John,
Not blower motors,

They were originally 1987 Hawk 511's.
427 tall deck truck blocks .125 over
4.250 stoker crank
9.0:1 pistons
Max timing is 34° set at 4500+ rpm.
They've got 830 cfm Holley annular discharge.
Not sure on the jetting.
I did have some bad gas, but thought it was diluted enough. Maybe not.

Tinkerboater,
Most of the plugs were loose. I put the new plugs in myself. If I even thought that I forgot to tighten them I would have to sever my arms at the shoulders, but $hit happens. Ever heard of them loosening up on their own?

What kind of jetting should I have with this setup?

Are you certain the plug wires are not crossed on 2 cylinders?

I know it's a longshot...

LOOSE PLUGS WILL DO EXACTLY WHAT YOURS DID. THEY MUST BE SNUG. The motor will run like crap when that happens. Just try a new set of plugs and see what happens. Run it for 30 minutes ( if it runs good ) then pull the plugs and look at them. If the plugs are not tight they will overheat and burn out the center electrode. The threaded part looked like they got real hot don't they.

Detonation will cause the plugs to loosen. We used to run 84-86 jets in 850 Holleys with headers on 454ci. 420 mercs, which was 4 to 6 sizes over box stock.

The one valve may have tuliped. You may be able to back off the rocker arm and still have it seal.

You should check the fuel pressure above 3000 rpm to see if you have any. Four to five pounds minimum, all the way to full throttle.

It wouldn't hurt to back off the timing a couple of degrees, like 30-32 until you find the problem. Then set it for best top end later.

Also try a cooler plug, it can't hurt at this point!!

Good Luck JB

BTW, I burned down a 525 hp motor on an 89 Top Gun, because of a plugged fuel pick up in the fuel tank on one motor, very expensive. There was no electrode tip and the plug was loose too, #7.

I've got the good dual fuel system setup with a separate mechanical and electric fuel pumps. Gauges show a steady 5 all the way up.

I appreciate all the good advice. Alot I haven't thought of. I'm on the way out to do a compression check if I could only find the figging compression gauge. My father is sharing my shop with me now that I talked him into living on his boat, so he is getting even with me for losing all his tools. (i never did that) :rolleyes: :D

I'll post my findings shortly.

I always like to keep my fuel pressure absolute minimum 6# and max 8.

In my opinion 5 is too low.

just a thought.

Along the lines of what Tinker said, if it is a valve is hanging up a valve spring is most likely the culprit.
If it is due to loose plugs, I've heard of holes in pistons also.
do a good check.
loose plugs let more air in causing lean conditions. (Just to back up what has already been said)

my .02
DAVE

I would do leak down test. Everytime I had a plug mess up like that I had to pull the heads & replace a valve or 2, Parts have to go somewhere. You may also need a piston. Sorry for bad news.

:(

I had to buy a new compression tester. I don't have a leakdown tester, but a compression test should tell some tails. I'm going out to do it now.

Bad day for me.
 

Well the bad news is the compression came out like this.

1 - 172
3 - 60 - had previous missing electrode, one lifter a little tight
5 - 70 - One lifter a little tight (test after loosening)
7 - 165

2 - 155
4 - 105 - Something is wrong here.
6 - 0 - Missing electrode this time. Pulled rockers and smacked valves with soft faced hammer. They sound like they are seating just fine. Still no compression with rockers off. :eek: Ventilated piston I would presume.

8 - 150

I am tearing down now. boo hoo....:(

And this was the new motor. :rolleyes:

Did you get that sinking feeling as you were doing test? I am so gun shy that I pull all the plugs after every time I go out. The last 2 times I had messed up plugs I did test & then started tearing down motor.

One word...Detonation

TurboJack, Yes, I did. Especially since #3 was the second one I tested. I just about have the heads off.

Detonation!!!!!!:mad:

Valves closed and still 0 compression.Might as well just pull the motor.You can pull the heads off easier with it on a stand because it sure sounds like you're gonna be needing some pistons.

I don't want to wait that long. I want to know now!!!

Could I get some fries with that too? :D

10 more minutes and I should be able to post some pics.

Dave F, Do you really think I need 6 to 8 psi? It does have pressure regulators but I haven't messed with them.

Here is the latest pic.

The winner is John B

This accounts for #6 cylinder

Detonation is more than likely the culprit.

Thank's to all that have responded.

Now it's off to pull the other head and check my jets!

It's alot easier to pull the motor with the heads off. Putting it back in might be another story.

Why? Detonation. One question is what does the pistons look like? The valves look very clean. Did you clean them up? I do not see any marks from the plug electrode hitting between piston & head.

I do not think compression is too high or had too much timming. Either motor got too hot and/or leaned out. If any parts of the plugs, parts of pistons, or valves look like you took cutting torch to them then not enough fuel is the problem.

You may have so-so fuel pressure at idle but what about during a good long run? Do you still have the anti-siphon fitting in fuel tank?

That's gona leave a mark---- WOW that valve got hot. You caught it just in time. That engine was running lean. The poping tru the carb was from the fuel being ignited by the red hot exhaust valve before the intake was even closed.

I agree, detonation. Fatten her up a bit and back off the timing when you get it back together. I had this exact problem several years ago. Would actually fire the electrode out of the threaded metal part. Scared the chit out of me twice before I did something about it. Thought I may have just gotten a bad plug the first time. Not. That motor is now an anchor.

Be prepared for at least one (sounds like maybe two or three) new pistons. And of course several valves too.

Jim, What type of intake are you running? All the middle cylinders are cooked and the end ones arn't. Does your other motor have all the same parts?
JB

PS, Have someone good check out your exhaust valve seat. Heat (which you had) can cause it to loosen and break and or fall out later and cause piston damage!
I have a set of 420 Merc heads for sale with all the parts.

John B, Funny you should ask about the intake. They are the ones that came original on the Hawk engines. They are the Edelbrock C454 intakes made for 4500 dominators, with spacer/adapter to 4150 carbs, (previous owner made swap) and the spacers from the intake to the Tall Deck block.

I have not made the switch yet, but just received the new World Products / Dart Tall deck to 4150 carb with the Brass clad water jackets. :cool:

Do you think that may be leaning out the inside cylinders? I would think it would be the opposite. I have more pics to post coming up..

Instead of posting the pics here and clogging up the system, I posted these on my site of the heads, pistons, old and new intakes, and spark plugs. I'm tired so I hope the pics are self explaining.

click below
Heads and Pistons

As soon as I saw first pictures it brought back old memories. Of course my motor was a twin turbo motor, & I think I was running 15 lbs of boost at time. I would say not enough fuel. The plugs are result of detonation. The motor I had melted down looked like someone had taken cutting torch between cyls. on both head & block.

I am surprised the pistons do not have any parts missing. I always seemed to lose the corner where valve relief was. From pictures can not tell but area cyls. scuffed up?

What kind of scuff marks would I expect to find?

If you look in the cyld. & do not see any scuff marks (lines/scraches in bore going from top to bottom of bore) you are probably OK. When the motor is in detonation it is wanting to make the pistons go down in bores crooked, thus scuffing the sides up. I would say if pistons look good & bores look good you are very lucky. If you do not see the hash marks in bores I would rehone & rering pistons. Easier to do now than after you get it back together again.

I do have some vertical scratches. Guess I'm gonna have to look at those more closely.

Thanks

Here is picture from a turbo motor that I melted down. You can see the scuff marks on the side of piston from rocking back & forth. Since detonation is not a smooth burn it cause the piston to put extra pressure on the piston skirts & cyl. walls. Thus the scratches.

This piston was result of not having a new motor dialed in & letting my son go out with some friends in boat with out me.

From the pictures it looks like those heads got real hot-- You may have a cooling problem also. Check to see if you can rock the pistons in the bore by pushing on the top and tring to rock it on the wrist pin.

Turbo, Great picture!

Jim,
Those look like domed pistons to me. I thought 9 to 1 would be flat tops, anybody?
Some times a peice of crap in the float bowl can become lodged in a carb jet and cause a lean out on cylinders it supplys.
I might want to know what happened to this engine, why was it rebuilt? Has this happened to it before?
How is the other motor holding up? What is different? How long did this one run, and did you get to full throttle?

Regards, John

Another idea. Intake vacum leak ? How was the idle of this motor ? Also , might wanna ck. the # 6 rod brg. while on the stand. Detonation can pound out a brg.

John B. I thought the domes were a little unusual for 9:1 also. The only explanation I can think of is these are tall decks with longer rods and I think the pistons are a little different. The numbers are from the specs I got from the guy that re-built the port engine the last time. Apparently the riser failed on the port engine causing extensive salt water damage to some cylinder walls and all the valve train. The block was replaced, all the valve train was replaced including the cam and lifters. I grilled him about the parts in each engine being identical and he convinced me that he was well aware of the importance of that.

The 830 cfm Holley's had #78 jets front and rear. This engine came from Hawk with 1050 cfm Holley's. I think the jetting is too lean. The 830's are sitting on an 2" adapter and the manifold had spacers under it.

Interesting note: The #3 and #6 cylinders were the hardest hit. They are also the cylinders that have the sharpest corner to make in the old intake manifold. #6 also had the furthest to go.

Thanks for the tip Donzi. That's why motors are coming out.

Compression ratio- The compression I had in 454 with piston in picture I think was 7.5-7.75 with 119CC OC heads. I now have a 540 with 119cc OC heads & the dish on the pistons looks like a soup bowl. I am told I have 8.00 now. I though that flat tops in that cu. in. engine was about 8.75. With those domes compression may be more that 9.00 & that would not be helping your detonation problem.

On Fuel- does carb have power valves in it? If so what sizes? Both primary & secondary? I think the jets in primarys are OK. (No surging while low throttle cruise) Secondary's ?? depends on power valve questions. I know there have been a lot of posts on jetting. Might need to do search & see what other people were using. Remember jetting has to do with Cu. In., carb size, cam & other things. Going from a big carb to smaller carb jets sizes are not necessary the same. If I remember correctly the smaller the carb w/ same engine jet size goes down since signal is stronger.

The #'s on the power valves tell when they open not how much they flow, that is determined by the channel restriction, (the passage which allows the fuel to by pass the jet). Jets #78 sound about right for a car, ( box stock carb ). Open headers, cool air and that open plunum spacer would require much larger jets. If it were mine, I wouldn't run less than #84's all around.

Since all the carb barrels are the same size(?), when you are wide open they all should feed the same amount to the cylinders they feed. I would keep them all equal, like they are now.

You are lucky on the pistons, checking the rod bearings is a good idea. Check pictures of big block pistons to see what you have likecompression ratio.

You probably will need high test (91 or 93). Most dyno tests I have seen on modified BBC's make max power between 29 and 32 degrees total advance.

Check the carb on the other motor. Who put the carbs on?

Looks like reversion to me. Washed appearance of chamber, detonation, center cylinders pounded. Water takes up combustion space which increases compression astronomically. I would take a hard look at the exhaust. BTDT

My .02

BT :cool:

I don't think it's the exhaust. It's got Gil manifolds that don't leak and dry risers.

Interesting thought, if they leak it would most likely occur between the manifold and the tailpipe. It wouldn't hurt to check this out. The center cylinders look like someone cleaned them!
Did someone get water in your gasahol. Reversion?, what cam are you running?