Heat difference in heads

[rdeyoe]

Particulars: 1981 J140TLCIM, just completed new pistons (.040 over on 1,3,4....064 on 2), new rings and gaskets.

Took her out to the river today to do initial break in. Started after a quick backfire. Got her to idle at 1500 for warm up. Checked temp on heads with IR thermometer. Port side is cold...only 100* or so. Starboard side is about 136. I have serviced the thermostats. I pulled the cooling outlet hose off of the starboard side, and restarted. I have lots of flow on that side.

My question is, should the heads be hot or cold? Which side sounds right? I was thinking that the starboard side was getting hot, and port is nice and cool. But I'm wondering if the thermostat might have slipped on the port side and it's just flowing free, staying cold.

Going to check again, and do a link and sync....think the timing may be advanced.

Thanks.

 

[boobie]

Re: Heat difference in heads

If you checked the temps after the mtr was warmed up the port side is running to cold.

 

[Solittle]

Re: Heat difference in heads

Around 140 is the norm for those engines.

 

[emdsapmgr]

Re: Heat difference in heads

The stats open at 143. The 136 temp is close to what you want. If you are only getting 100 out of the port head, the stat may be stuck open or the nylon pressure relief valve may be stuck open. You are doing the right thing to question this temp variance and work toward a solution. When you say you "serviced" the stats, do you mean that you installed new ones-always the right thing to do on any overhaul.

 

[rdeyoe]

Re: Heat difference in heads

emdsapmgr, yes, replaced them, springs, relief valves and gaskets...whole kit. I did it with the engine mounted and with a bubbleback, it's kinda tight in there. I'm thinking that maybe the port t-stat slipped. Got a drum and cut it for a test tank. Put it in there and started it. Water is flowing immediately out of the outlet ports in the lower unit pretty much right from start, so I must have that port stat off center or not sealed.

I had replaced the port head, as the ring damage in the old one was too much. I didn't do the starboard one. Only one cylinder on that one was hammered, and not too badly to smooth out...other cylinder was clean. But on the start in the test tank, we're getting some serious leaking externally. Think I'm going to change out that head too, with another new gasket (they can't be re-used, right?). Unfortunate, as I think that head is heating correctly, but it must not be flat enough to seal. It idles pretty well, but every once in a while, backfires and i'm pretty sure it even started running backwards at one point (can they do that?). It's just pouring out too much water between cyls. 1 and 3, and it's coming out into the cowling, so better to be safe, i figure. Thanks all!

 

[emdsapmgr]

Re: Heat difference in heads

An occasional miss at idle may be a lean sneeze. Not an ignition problem, a sneeze is a lean condition in the idle circuits (passages) inside the carb body. Caused by a fuel restriction-maybe dried fuel in the passages. You may have to pull the carbs apart and clean the idle passages out with a gumout type product. I'd don't reuse head gaskets. You can pull the head off, scrape the old head gasket off. Put the head on with no gasket. Try to rock the head back and forth on the block. Or, put it on a pc of glass. You may sense whether the head is flat (true) or not. If it's slightly warped, you may be able to have the head planed flat. (be sure not to plane much off the head.)

 

[daselbee]

Re: Heat difference in heads

A true backfire, and kicking the engine into running backwards says to me that the ignition coils are not wired right. The cold side is not firing at the right time, and sometimes produces a backfire. Re-check the coil primaries, and if necessary, index the flywheel and check spark timing on all four cylinders.

It is very easy to get the coils switched (upper for lower) on that motor. Just for grins, do nothing except swap the spark plug leads...i.e. pull the lead off #2 and put on #4, and pull #4 and Put it on #2. (ASSUMING THAT IS THE COLD SIDE). If not, then swap #1 and #3.

Remember that the orange primary wires are color coded. Orange/blue will be for the top coil, and orange/green will be for the bottom coil.

If not firing right on a bank, that side will run cold. Post back please.

 

[rdeyoe]

Re: Heat difference in heads

Hmmm, now you got me thinking dalesbee. It could be mixed coils. We did replace the 2-4 head. I'm pretty sure we put the coils on the new one just as it came off the old one, but maybe, juuuuuust maybe....

On our first crank, it backfired out the prop like a gunshot....even some sparks (it was getting dark). But it did start and idle, which always was so hard to do before anyways so I figured it was firing ok. Perhaps I'm assuming too much and missing a simple thing. I'll look at it tonight. Sometimes ya gotta step back and start simple.

Still thinking I'm going to change out the starboard head too though....too much water leaking out that side. My girl was watching it in the tank while i was starting. She said she could see it streaming a bit between cyls 1 and 3 on the outboard side of the head. I didn't notice that...i just saw it dripping off the bottom of the head.

 

[dazk14]

Re: Heat difference in heads

If you prefer... Normally, the head can be easily resurfaced on an 80 grit belt sander at any automotive machine shop.

Your cost probably ~$25. Just let them know it's a light weight, 2cyl., 2 stroke head - to keep the quote reasonable.

It's done by hand and takes ~3minutes.

 

[daselbee]

Re: Heat difference in heads

Backfiring like a shotgun out the prop is absolutley ignition timing way way off. I have worked on an engine with the same issue. Guy did his own head swap, and accidentally swapped coils...look carefully.

 

[rdeyoe]

Re: Heat difference in heads

@dazk14: I would sand the head, but I think I'll just replace it (the service manual says to put it on a piece of glass with 80 grit paper and do figure eights with it). There was damage in the #1 combustion chamber (the #3 is fine), just some pocking from the ring bouncing around in there. The machinist told me to just take off the sharp edges on the pits, as carbon will fill them up anyway. I Dremel'd the chamber (there were quite a few pits, one fairly deep) , but it left it pretty smooth. I'm a bit worried about the shiny surface promoting a pre-ignition situation. The other 3 cylinders have a textured surface to them, kind of a bumpy matte finish. The gasket is leaking anyway so I might as well put a head on that I'm confident in....or am I being too paranoid?

 

[dazk14]

Re: Heat difference in heads

Shiny surface is fine. As your machinist indicated, edges are the enemy. Without seeing the head, it is difficult to confirm that it was a good candidate for hand finishing. You can remove too much material, etc..

Glass is very flexible. You need an absolutely flat substrate, which is not very common. Thicker glass is better, but that's another discussion. I have had plenty of heads come in the shop "DIY straightened" and were out to lunch, spec. wise.

If you have another head available, sure use it. Just make certain it is straight. You cylinder deck could also be out of spec..

Be sure to re-torque head after it has come up to temperature and cooled. One at a time, slightly loosen each bolt and tighten to correct torque going in the correct pattern. You want a quality dynamic torque without "sticktion". Repeat @~10 hrs.

Good Luck!

 

[daselbee]

Re: Heat difference in heads

I gotta modify my post...I remembered...the coil primary wires are orange/blue and solid orange. Orange/blue is top, orange is bottom.

Post back what you find.

 

[boobie]

Re: Heat difference in heads

I thought orange/green was the bottom. Solid orange is the center cyl on a v-6.

 

[daselbee]

Re: Heat difference in heads

I thought orange/green was the bottom. Solid orange is the center cyl on a v-6.

You are right, BUT...
We are talking about a 1981 V4. I am almost positive...my memory...urrfff...that the wire colors were orange/blue and orange.

Orange/blue top, Orange middle, orange/green bottom on a V6.

 

[dazk14]

Re: Heat difference in heads

You are right, BUT...
We are talking about a 1981 V4. I am almost positive...my memory...urrfff...that the wire colors were orange/blue and orange.

Orange/blue top, Orange middle, orange/green bottom on a V6.

I think you both have good memories.

I have seen them BOTH ways. Always Orange/blue top. Always Orange/green OR Orange on bottom. Each bank with it's own power pack. The OP can easily verify what he has installed...and the correct orientation as noted.

I can check the service manual tomorrow to see how it began life, but what's on it now - 30 years later - is all that matters.

Now, let's move to the V8 which looks like a circus!

 

[rdeyoe]

Re: Heat difference in heads

Didn't get the chance to check the wires last night. But I did come on the pictures of the cylinder heads before replacing / cleaning. Cyl 1 was the one I cleaned up. Didn't go very deep to cover most of the marks. Chamfered / blended any edges of larger pits, like the one at about 5:30 in the pic of cyl 1. Cyl 3 was good.

The cyl 2 is the one that had punched a lot of ring into the head, and the one that had to be bored .064 over to clean up the cylinder. The 2-4 head was replaced with one that had perfect combustion chambers and had been planed.

 

[rdeyoe]

Re: Heat difference in heads

@daselbee: Welp, checked all the coil wires and plug wires again. Fortunately, or not, they're all in the correct positions. I double checked them all and I have orange / blue (looked like a black stripe though, didn't have my glasses on!) on the top coils and solid orange on the lower ones. The plug wires were top coil to top plug and bottom coil to bottom plug on port and starboard. I was kinda hoping that you were right on the port head (cold one),....now I can only think that the thermostat is slipped or leaking and flowing too much. I've done the link and sync from the OEM manual also. I think i'm going to try and index the flywheel and put a timing light to it and check each cylinder. Is there a firing order on these? Usually, on a four cyl. auto engine it would be 1-3-4-2. I haven't looked in the manual yet...i'll check that too. I'll make some marks on the flywheel for each cylinder and move the induction clamp to each plug and see if I can tell where each is firing. All the plugs looked wet / oily, but the #1 looked more burnt than all the others. Still thinking the head blending I did may have made that cyl. too hot. Plugs are Champion UL77V, per the manual...

Any other ideas are very much welcomed and appreciated....

Edited to add: I also double checked the plugs to the power packs, and they're on the right sides also. Would be kind of hard to plug those in across the motor anyway.

 

[dazk14]

Re: Heat difference in heads

Didn't get the chance to check the wires last night. But I did come on the pictures of the cylinder heads before replacing / cleaning. Cyl 1 was the one I cleaned up. Didn't go very deep to cover most of the marks. Chamfered / blended any edges of larger pits, like the one at about 5:30 in the pic of cyl 1. Cyl 3 was good.

The cyl 2 is the one that had punched a lot of ring into the head, and the one that had to be bored .064 over to clean up the cylinder. The 2-4 head was replaced with one that had perfect combustion chambers and had been planed.

From what I can see - I would not use either of those heads - and we do not toss out every head that has been dinged.

 

[daselbee]

Re: Heat difference in heads

Well crap...it was a shot anyway. I too would index the flywheel at this point. Firing order is 1-2-3-4, but double check that on me to be sure. V6s are 1-2-3-4-5-6.