225V6 rough Idle

My 225 is acting up. At idle it misses and sounds like a exh. valve is staying open on the right side of the eng. Also the exh. temp. on the right side is 250 deg. at idle and the exh. temp on the left side is 520 deg. at idle. When I rev it up and hold it for a while the temps even out but the miss is still there. I have tryed new lifters thinking one was pumping up, I also pulled the head and lapped the valves and checked for a blown head gasket but found nothing. I adjusted the carb thinking that fuel could be the problem but no change. All 6 cyl. have 150 lb. cranking comp. and 60 lb. running comp. All cyls. tested the same on a leakdown test also. Why would the left side of the eng. run fine and the other not??? Could I have an exh. valve hanging up causing the missfire?? or possibly some weak valve springs?? A vacuume check also shows a fluctuation of 4in. vac. at idle. That makes me think it's a valve. Any help would be great.!!!! Thank's.

 

At first I would say a sticking valve or bent pushrod. but, since you've pulled the heads and lapped the valves, you "should" notice a sticking one and/or a broken valve spring. It could be that a valve is sticking only when it heat's up.

Have you checked the plugs and wires? Just a thought. A bad plug wire can cause something like this--1 cyl not fireing. Check the color of the plugs also.

HTH

 

wrong distibutor(odd vs even fire),HEI module, bad timimg, incorrect firing order, crossed plug wire,check plug wires, arcing inside dist cap/rotor, leaking intake manifold or vac leak, dist off 1 tooth,
Aren't you gald you asked
back to basics with thorough diagnostics
most likely carb or ignition issue(s)

 

with HEI, is ballast resistor bypassed ?
need 12 volts for HEI to function proerly

 

thinking....... more coffee.........a little history please
just start acting up or were mods made and problem began shortly thereafter?

 

Jim, and Mike too: I've learned the hard (very hare and ) way to start with the simplest things first.

When I was in college, my best friend had a '69 Mustang. He is no stranger to engines. He did a tune up on it and it was missing after he got done. He couldn't figure it out. At the time I was working as a mechanic at a 66 station that had a great owner/mechanic. He said bring it in and he would look at it.

Diagnosis: When my friend put in the new plugs he dropped one and closed the gap on the plug. He didn't think to re check it--he just installed it. Problem solved!

 

Check the timing of the motor. Mine was like that due to the dist become loose and having around 50 degrees of advance.

 

Thanks for the info. A little history: I pulled the eng. downthis winter because it was missing out the exh. on the right side and because the timing chain was making a lot of noise. I put a new Cloyes True roller chain and gears in ( I rechecked that too) and installed a DUI dist. I thought the miss in the exh. was a pumped up lifter so I put new lifters in. Put it all together and it was quiet at the timing chain but it still missed at the right exh. I checked the fireing order and that was right, I changed plugs and wires and it still missed. Next I figured it MUST be a burnt or sticky valve so I tore it apart again and had a shop touch up the valves and seats but they did not do a full valve job (valve guides and seals.) Put it back together again and it still missed. Next I put the old Delco dist. back in just for the fun of it and it still missed. I even went as far as to buy shorter pushrods to see if maybe the valves were not closing all the way. Not the problem, just got ticking rockers . I changed carbs. because a local shop thought that the right side was not getting fuel but that did nothing. The plugs look the same on both sides of the eng., comp is the same on all cyls.,I just pulled the intake off again tonight on the hunch that I might have a intake leak on the bottom side of the intake gasket on the right side, but it looks like it had a good seal. I also pulled the right head again because a friend of mine who builds engs. listened to it and said that it was a sticking valve due to loose valve guides. I'll send the head in Monday and hope he finds something. A couple questions: 1) When installing the intake, I used the supplied rubber seals for the ends of the manifold, could they be too thick and keeping me from getting a good seal against the heads??. Also, could I just use a bead of silicone on the ends like I do on all Chevy engs.?? 2) Is there a kind of sealer I could put on the metal intake gaskets to make sure I don't have a vac. leak on the inside of the gasket? I'm thinking of Three Bond Sealer which is what I use when I rebuild snowmobile engs. on the two case halves. ( can be used in direct contact with fuel) Thanks again for the input,!!!!

 

well, you certainly are getting very personal with that :v6:
my thoughts:
lets define the "miss"
A) dead cylinder, miss all the time
B) dead cylinder, goes away off of idle
C) engine miss, popping out of exhaust pipe at idle, goes away off idle
D) engine miss, popping out of exhaust pipe, all the time

Your compression readings looked okay, but if you were having valve problems, cylinder leakage test should show varying results on suspect cylinder (s) as the valve reseats its self.
At idle, have you pulled the plug wires off, 1 at a time, to help identify the weak or missing cylinder?
The rubber end seals for the intake can't really be the cause; they can give trouble squeezing out and causing an oil leak, but that won't cause the miss. 3 bond should work okay, I have used Copper Coat (?) in the
past.
With all of the work you have performed, nothing has changed. I assume all the valve springs and keepers are okay; keepers not starting to pull through. blah blah blah
I would try and identify the cylinder that is missing; this would help in the diagnosis, rather than just a cylinder on the right side.
When I hear comments about "sides" of the :v6: missing, this usually indicates ignition problem: timing, distributor, wires, firing order etc.
Do you have a good ground for the HEI ?
Do you run headers? Any visual discoloration (pink, blue) on any of the tubes that might be a give away as to which cylinder might be burning leaner than the others?
When it returns to running stage, if no change, then thorough diagnostics are needed; this is not to say that you aren't already, I am just saying stand back and recheck everything. Keep us posted

 

Hello Mike,
What type of plugs? Also, do you have a mechanic's stethoscope?

You can use a bead of silicone on the intake ends, but wait until you're sure you won't be going back in (it's like welding the intake on). Gotta make sure none of it gets in the valley, so I use the rubber seals and a dab of gas/oil resistant RTV in the corners where the intake meets the head.
Good luck and let us know what plugs you're using.

 

I'm running headers, the odd thing is that all three cyl's on the right side act the same when I take one plug wire off at a time. There is some diff. in the way it runs when I take the wires off but it don't change the sound at the exh. The miss is at idle and at driving rpm, but seems somewhat better when the eng. is under load, but is still there. At around 3000-3800rpm the eng pops once in a while out the right exh. when I hold it at that rpm steady for a little while. The #6 cyl looks a little cleaner on the piston top and the exh is a little darker but the plugs look the same throughout the entire eng., and the valves look the same on all the cyls. on the right side. I do have a good ground on the HEI and great spark to all cyls. I have never heard of the right side sounding diff. than the left as Patrick said. Is this a common trait of this eng. I don't remember it sounding like this when I first got it. Thanks again. :?

 

The :v6: will idle rough and shake at idle. Mine will pop out the pass side once in while; at about 3000 rpm, not driving, the ehgine will also pop out the right side; maybe unburned fuel detonating in the ex pipe; it runs perfect otherwise, no problem while driving or under load.
A quick story, but did happen to me and my :v6:
Shortly after installing the :v6: it rained one night. I still had the hole in the hood from the :hurrican: I had removed. I did not have a rubber sealing washer under the air cleaner wing nut. The next morning, I went to start the Jeep; the engine turned over once and hammered to a stop.
@#$#@$# What was that? I waited a minute or two, then tried to turn it over again; it ran but was running "funny". Lots of popping out the pipes, especially passenger side; I let it warm up and took for a drive, ran great, but there was a small knocking sound. At the time I didn't think anything of it.
Over the next year, I had noticed discoloration in the header tube coming off #6 cylinder and the popping was getting worse. Compression and leakage tests showed acceptable results. Carb work, ignition work, did nothing, same results.
On a fluke I removed the intake manifold, not knowing what I was looking for. I found a very small chip of piston skirt material, lying in the lifter galley; where did this come from?
As you stand there looking at your exposed lifter galley, try to imagine a piece of piston skirt the size of a penny lying there, waiting to be discovered.
Removing my oil pan revealed a real nice, bent, #6 conn rod. This had bent when the cylinder had water enter it through the wing nut for the air cleaner. The way the engine sits, and the way it was sitting in my driveway, the lowest point for the water to go. When I tried to start the engine, water doesn't compress and the rod bent; after starting the engine, the knock I heard was one of the crank counterweights hitting the piston skirt, becuase the piston is now lower in the cylinder bore from the bent rod, resulting in the fractured piston, and the piece somehow ended up in the lifter galley, quite a ricochet !
I have that rod and piston hanging above my work bench.
FWIW, I put about 3000 miles on that engine before I found this problem; it was annoying sounding, but not enough that I could pin it down.I know this won't help you, but I know what you are going through.

 

Jim: Ouch! I guess it just goes to show how tough these :v6: engines really are.

Mike T does have a courious one here. Any bets going on? My best guess is a weak valve spring--sloppy guide--something still wrong in the ignition.

Now, if this was my engine, it would be a cloged carb jet that I only discovered after completely rebuilding the engine!

 

Jim: I think we have all " been there, done that" at one time or another

If I were betting I would say ignition/distributor problem, even though dist's have been swapped out; gotta be something there
no disrespect meant to MikeT, probs like this are tough to find

 

Mike what kind/type/size plugs are you running???

 

Hippo393 asked what plugs I was running: I am currently using AUTOLITE 85's but have used Champion UJ12Y 's in the past. I do have a mechs. stethoscope and listened to about everything on that eng. relating to valves, exh. at the headder tube up by the heads, I even listened to the spark plugs fireing. Everything sounds the same on both sides of the eng. Tonight I just had to pull the valves out of that head before I send it in tommorow to get checked. I found the exh. valves moved very roughly in the guides and the valves were loose in the guides. The valves had rough spots on the stems. I'm hoping that the valves are binding in the guides when there is tension on them causing my problem. I just wish the guy I had clean up the valves and seats would have noticed the loose guides and just done a complete valve job right away. Guess he was just trying to save me a buck. After hearing Jims story I might just check that too!!! I've done everything else!! Thanks again. The way this is going you would think this was some kind of a test!!

 

Like Patrick mentioned, mine too sounds different on the passenger side; kinda like a miss. Mostly noticeable at idle. I've never done a compression test, but I might in the near future just for the heck of it. It has about 139,000 on it and I've wondered if this "newer" gas has eaten up the valve seats. It does seem to run good though.

 

Just wanted to add another :v6: that does the same thing. I just converted to HEI (Cape Conversions) over the weekend and the EXACT (to the word) symptoms you are describing have become apparent. I think think it has always been this way, but with the HEI smoothing everything else out so much, this "noise" really stands out.

 

Dave: Weird. I have an HEI that was on there when I bought it. PO put it on about a year before that. I have none of these symptoms.

At a 600 rpm idle, it purrs like a syncopated kitten.