Leaking exhaust valve

[Stevehose]

I have poor compression on #2 cylinder - 75lbs. Other cylinders are at 160-165. I did a leak test and it's the exhaust valve - I can feel the air coming out of the tailpipe.

Valve clearance seems to be in spec but should I adjust either way to effect change?

What if anything can I check or try to fix before yanking the head? A carbon cleaner or anything? Mystery Oil? I want to try all options before surgury.

No coolant or oil is burned - that's tight.

Thanks. :sad:

 

[kasbatts]

If the clearance is correct, there's a good chance it will be a burnt valve, head of I'm afraid, Another possibility is the head itself, hows the oil and coolant? all look normal? I ask because I once had a Peugeot that the exhaust valve seat fell out of the head, I assume it's only running on 5 cyl?

On the up side, It's the perfect excuse to do a big valve head and a cam


Steve

 

[Stevehose]

Doesn't leak or burn any oil or coolant - both are fine. It appears to run on all cylinders but I have a miss at idle - runs well at speed with no obvious loss of power.

Do these valves "stick" like my old muscle cars did?

If the clearance is correct, there's a good chance it will be a burnt valve, head of I'm afraid, Another possibility is the head itself, hows the oil and coolant? all look normal? I ask because I once had a Peugeot that the exhaust valve seat fell out of the head, I assume it's only running on 5 cyl?

On the up side, It's the perfect excuse to do a big valve head and a cam


Steve

 

[kasbatts]

No, valves wont stick, Your old Muscle car probably had Hydraulic lifters, these are what "stuck"

I'm still picking a burnt valve, will be good to get the other guys opinions, I would think the miss will get worse and worse over time as the valve deteriorates and you will drop a cylinder (if I'm right), question is, why has it burnt a valve?? (if it has) from my experience this is from having a too lean mixture, are you carbed or FI?

 

[Stevehose]

I have carbs and if anything I run rich, especially with the triple webers. I think the recent install of them may have exposed this issue. Can't a valve stick open?

 

[61porsche]

What

does number two plug look like? Make sure you're not running lean or rich on that cylinder.

By air out the tailpipe, I gather that you're doing a leakdown test? Make sure you "rocked" the crank since there is a lot of overlap to make sure you're just not off a bit. I.E., it runs fine at speed.

Did this happen all at once? Meaning, how long ago did you check it?

Nothing you can do about adjustment. Rocker moves freely? Compare the adjustment hole in relation to the others and the rail of the head. In other words, is there some abnormal wear?

You can try top end cleaner like Seafoam. Do it outside. Slowly. The go run the heck out of it to see if you can blow it out.

Boroscope?

 

[Stevehose]

See replies, thanks.

does number two plug look like? Make sure you're not running lean or rich on that cylinder.

PLUG LOOKS OK - NORMAL

By air out the tailpipe, I gather that you're doing a leakdown test? Make sure you "rocked" the crank since there is a lot of overlap to make sure you're just not off a bit. I.E., it runs fine at speed.

YES LEAKDOWN - I TOOK THE VALVE COVER OFF AND SET THE CYLINDER TO TDC - THEN HOOKED UP THE COMPRESSOR - IS THIS OK?

Did this happen all at once? Meaning, how long ago did you check it?

THIS IS MY FIRST COMPRESSION TEST, I DID IT BECAUSE I AM STILL HAVING PREMATURE MAIN DRIP FROM CYLINDER #1 ON MY WEBERS SO I DON'T KNOW HOW LONG IT'S BEEN DOING THIS-SEEMS TO RUN OK EXCEPT FOR SLIGHT MISS AT IDLE. CYLINDER RESPONDS TO IDLE MIX ADJUSTMENTS.

Nothing you can do about adjustment. Rocker moves freely? Compare the adjustment hole in relation to the others and the rail of the head. In other words, is there some abnormal wear?

ROCKER MOVES FREELY AT TDC LIKE THE OTHERS - I WILL CHECK HOLE POSITION AND CLEARANCE THIS WEEK WITH COLD ENGINE

You can try top end cleaner like Seafoam. Do it outside. Slowly. The go run the heck out of it to see if you can blow it out.

I HAVE READ ABOUT SEAFOM AND BG44 AND OTHER BG PRODUCTS - THESE WILL CLEAN INTAKE VALVES BUT WILL THEY CLEAN EXHAUST VALVES SINCE IT IS BURNED? BY SLOWLY DO YOU MEAN A LITTLE BIT AT HIGHER REVS OR LOWER REVS? WHAT ABOUT BG OIL ADDITIVE TO CLEAN OUT CRAP ON THE VALVE TRAIN? MY VALVE TRAIN LOOKS CLEAN WITH NO VISIBLE ABNORMAL WEAR.

Boroscope?

HMMM.....THAT WILL BE HARD TO GET PAST THE WIFE-SHE ALREADY SENSES TROUBLE

THANKS!

 

[61porsche]

Mmmm

Plug-doesn't sound like a burned valve.

Weber- fix it. dripping= washing crap out of an old engine- But could be #2 effecting number 1. Turn the screws and see if you can get two to fire at idle as it sounds like one is real rich and two is lean. Swap the idles.

TDC- nope. TDC for that cylinder. Valve cover off, dist. cap off. Pointed to number two. Wrench on the crank. Leakdown up. ROck the crank and see if you get both valves closed. Like I said, lots of overlap in an M30 meaning it ain't always where you think both valves are closed. Gots to be closed for a leakdown. Now go buy a real compression guage and spin that puppy.It doesn't care about valves closed.

Tip- rockers and wear- bushes, tips, valve tips, shafts- that little hole for your wire or allen wrench and it's location can tell you a lot. That hole disappears down toward the rail of the head when there's wear. Simple and visual. One that is hard to get to means something's amiss . Now you can measure off the cam. Take 4 thou off. or said another way- use 8 thou/ mm? EXmalibu got me thinking about LS7's and smoking tires. Yeah the cost too much now. Unless you're Clint Eastwood talking to your empty engine bay instead of an empty chair.

Nope. Don't go adding a flush to an engine unless you do so just before you change an oil. I wouldn't at all- too much crap turns loose. Better to just change your oil sooner and much more frequently until it gets clean and stays clean.

Use Seafoam. SLOWLY pour into the carb and keep a high idle. Don't let it die. AND don't decide MO is better. It's not. It's snake oil and it works every blue moon.

Chances are your carb washed crap down and out. AND maybe just needs to be blown out. I mean run that puppy. Like Forest Gump.

 

[Stevehose]

Food for thought:

Plug-doesn't sound like a burned valve.

Weber- fix it. dripping= washing crap out of an old engine- But could be #2 effecting number 1. Turn the screws and see if you can get two to fire at idle as it sounds like one is real rich and two is lean. Swap the idles.

I've gone through the Webers ad naseum, swapped them around, changed up all jets, E-tubes, checked AFM, lean best idled, etc etc and #1 barrel still drips so it is an engine/vibration issue-possibly cause by a pressure issue from #2 exhaust valve back up the manifold to barrel #1 forcing the drip?

TDC- nope. TDC for that cylinder. Valve cover off, dist. cap off. Pointed to number two. Wrench on the crank. Leakdown up. ROck the crank and see if you get both valves closed. Like I said, lots of overlap in an M30 meaning it ain't always where you think both valves are closed. Gots to be closed for a leakdown. Now go buy a real compression guage and spin that puppy.It doesn't care about valves closed.

I set TDC on #2 cylinder-both cam lobes pointed down and no valve movement - sorry I wasn't clear on that. I have a compression gauge - 160-165 on the other cylinders except #2.

Tip- rockers and wear- bushes, tips, valve tips, shafts- that little hole for your wire or allen wrench and it's location can tell you a lot. That hole disappears down toward the rail of the head when there's wear. Simple and visual. One that is hard to get to means something's amiss . Now you can measure off the cam. Take 4 thou off. or said another way- use 8 thou/ mm? EXmalibu got me thinking about LS7's and smoking tires. Yeah the cost too much now. Unless you're Clint Eastwood talking to your empty engine bay instead of an empty chair.

This I will check, the question is, do i feel lucky?

Nope. Don't go adding a flush to an engine unless you do so just before you change an oil. I wouldn't at all- too much crap turns loose. Better to just change your oil sooner and much more frequently until it gets clean and stays clean.

My oil is very clean and minimal varnish in valve train. I change very frequently regardless of use.

Use Seafoam. SLOWLY pour into the carb and keep a high idle. Don't let it die. AND don't decide MO is better. It's not. It's snake oil and it works every blue moon.

The snake oil is worth a try before tearing into the patient.

Chances are your carb washed crap down and out. AND maybe just needs to be blown out. I mean run that puppy. Like Forest Gump.

My car doesn not get much highway driving so will seafoam and give it a go.

 

[61porsche]

Fuggetta

best lean. Webers ain't lean and they sure don't like it. 35 cent gas back then.

One barrel lean, one barrel drips.

Swap those idle jets cause it could be some oldtimer ( Crazy German tuners you got those from) just reamed em. Buy a $7 jet guage/ reamer kit for a VW. If you really want to know. And there ain't no other way. Those stamped numbers don't mean a thing.

Compression guage- OK you convinced me. Something's funky. But...... the carb.... it probably washed a boat load of crap out of the combustion chamber.

Go find that vacuum guage. Tell me the needle is jumping like a mexican jumping bean.

ROCk the crank. Then tell me you've got air out the pipe. ROck it till you get air out the carb and tell me you got air out the pipe.

Driving in town- bad. Italian tuneups Good. There must be a reason BMW put it in the driver's manual. Go for a real drive. Fast and Long. Downshift. Feel the force. I figure if it's gonna blow it's better than if the wife's in the car.

Oil change- the real reason you want to change the oil is that it develops acids which is in no way the correct way to alter bearing clearances or reduce high oil pressure. Clean, fresh, at least twice a year. Or if you're going to store.... just before.

 

[Stevehose]

I have tried all different idle jets sizes from 45F9 to 60F8 and swapped out main jets to other carbs - I should have bought stock in Pierce Manifolds - does not affect #1 aux venturi drip which starts at 2k rpm.

DCOE's have no vacuum ports on #1 carb so I can't attach my gauge.

I will seafoam it and take it for an Italian tune up and see what happens.

Ciao!

best lean. Webers ain't lean and they sure don't like it. 35 cent gas back then.

One barrel lean, one barrel drips.

Swap those idle jets cause it could be some oldtimer ( Crazy German tuners you got those from) just reamed em. Buy a $7 jet guage/ reamer kit for a VW. If you really want to know. And there ain't no other way. Those stamped numbers don't mean a thing.

Compression guage- OK you convinced me. Something's funky. But...... the carb.... it probably washed a boat load of crap out of the combustion chamber.

Go find that vacuum guage. Tell me the needle is jumping like a mexican jumping bean.

ROCk the crank. Then tell me you've got air out the pipe. ROck it till you get air out the carb and tell me you got air out the pipe.

Driving in town- bad. Italian tuneups Good. There must be a reason BMW put it in the driver's manual. Go for a real drive. Fast and Long. Downshift. Feel the force. I figure if it's gonna blow it's better than if the wife's in the car.

Oil change- the real reason you want to change the oil is that it develops acids which is in no way the correct way to alter bearing clearances or reduce high oil pressure. Clean, fresh, at least twice a year. Or if you're going to store.... just before.

 

[61porsche]

Bad

ill fitting, not sealing aux venturi. ( Aka leaking, not emulsifying, and leaking... dripping.)

 

[kasbatts]

Ah ha, DCOE's,

so, I'm guessing you have checked the main and idle jet sizes? to make sure there all the same, and just because the number reads the same dosent mean the jet hole is!! all I'm saying is visually check each jet for hole size and to see if the jet is clear and open, no junk blocking them up, if you can find a nice fine needle or pin, or even better jet files to poke through to check their clear and that all the holes "Look" the same size.

Did you do the carb conversion yourself?, and if you did, did you run the engine or drive much before you tuned / changed jets?

Still, at the end of the day, if you have done a leak down test and you are sure that both valves are closed and not being held open by the cam or followers and you have air coming out the tail pipe..........?

as for the dripping carb, do you have the anti vibration rubber isolators between the carb and the manifold? and the rubber isolating fitting kit (nyloc nuts, rubber spacers, special washers etc) fuel pressure/volume all correct?

On my Toyota starlet many years ago I had DCOE's (was my road car) I ended up having a fire because of leaking carbs, it dosent take much pressure to get past those little float valves, when your just driving slow around town the fuel pressure can build up in the system, My tuning guy (a legend with carbs down here in NZ) suggested the following.

this was using the standard Webber / Dellorto fuel line fittings

Get another carb fuel inlet fitting, not the single one, the double one that Tee's the fuel from the inlet carb to the next carb in line, drill and tap the outlet side of this and wind in tight a small bolt, cut of the head of the bolt, thus leaving you with a blocked of outlet.
next, drill a 1mm hole through this block off, assemble this onto the last carb in the row (closest to fire wall if your fuel comes in from the front) and put a return fuel line onto this back to the tank, any excess pressure will bleed back to the tank and hopefully not through the carbs.

Worked a treat for me

 

[sfdon]

IF.....

Your cam lobes on #2 are pointing down
and you have a feeler gauge
and the exhaust side is so tight that the gauge won't fit in no matter what
and the adjuster can't adjust anymore
Your valve seat is eaten away.
Which can be repaired....

You really should do a wet test next. Once the head is off you can't go back.

 

[JFENG]

if you had an intake air leak on

that specific cylinder (e.g. manifold to head or via emissions plumbing (brake booster), etc. it could cause a single cylinder to go lean.

 

[JFENG]

Don't people normally just run a pressure regulator

It's been 25 years since I last had a Weber (well, just bought a car with 45's), and we always ran a pressure regulator set at 2psi. Steve, I doubt you would do an install without one.

 

[JFENG]

wet test

all good mechanics (e.g. not me) will run a wet test whenever they see low compression or leakdown numbers. Usually helps identify bottom/top end problems.
However, a ring problem wouldn't cause air to come out of the exhaust.

I'd take the good advice and repeat the test and rock the crank is it's common to mis TDC enough to get a false leak.

 

[Stevehose]

Yes I am running 2.5lbs of regulated pressure. I have been through the carbs, changed jets, floats and swapped the order of them and the drip it is not caused by the carb. Either it's a vibration or weird back pressure thing from #2 cylinder. When revving it up I can see the level in #1 main well quickly rise up and dump into the venturi tunnel, with or without the aux/chokes in. The other mains do not do this. I've tried all soft mounts available and this did not solve the problem. I need to fix #2 compression before addressing the drip. I will do a wet test and rock the crank per 61Porsche but I did the leakdown with the valve cover off and visibly setting the cam lobes away from the rockers. Will also check the valve seats per SFDon. Thanks.

It's been 25 years since I last had a Weber (well, just bought a car with 45's), and we always ran a pressure regulator set at 2psi. Steve, I doubt you would do an install without one.

 

[Stevehose]

Interesting - will explore - thanks.

Get another carb fuel inlet fitting, not the single one, the double one that Tee's the fuel from the inlet carb to the next carb in line, drill and tap the outlet side of this and wind in tight a small bolt, cut of the head of the bolt, thus leaving you with a blocked of outlet.
next, drill a 1mm hole through this block off, assemble this onto the last carb in the row (closest to fire wall if your fuel comes in from the front) and put a return fuel line onto this back to the tank, any excess pressure will bleed back to the tank and hopefully not through the carbs.

Worked a treat for me

 

[sfdon]

The wet test will tell you if you have a weekend job or a weeklong job ahead of you.
If it is just the head and carbs- talk to David in Tupelo. He has a nice setup to sell that is sitting in my shop.