carb spitting mixture back out, pushrod not in lifter bore, success inside! Options

[purple]

Hey guys, I have a bizarre problem with my engine. I'll give you guys some back story after describing the problem.

The engine runs, poorly, it sounds like it's running on 3 cylinders. And wonder of wonders, it IS! Cylinder #3 is doing something really weird. It's blowing all the air & fuel mixture out of the carb throat! the other 3 are drawing down just fine, but this one if i pull on the throttle the engine spins up a bit faster and it becomes a HUGE plume coming out of #3.It eventually ignites and makes a sick ass crack...not that i'm in to that kind of thing.

it's running at 150 degrees where the other 3 are likely 200 degrees higher. why is this happening?

I have a 2.0L (i think ) with 1.7L heads and I just put the weber 40 IDF's on there and set the timing as best as i could on the mallory unilite, which has run the engine well for a few miles. the engine also has a eurorace header and a hydraulic cam and lifters.

the rocker for cylinder #3 exhaust was kinda loose against the valve, and as i've read it's got to be in constant contact, so i adjsted it per webcam's specs.

Is it possible my intake valve on #3 isnt closing all the way, making all the compression go back up the carb throat? I'm kinda lost with what to do with a puking carb, i've never seen anything like this!

Thanks guys! please ask me questions to get closer to what's going on if you need info!

[tagtmeyer914]

that dont sound very good at all. my experience on a similer problem is not porsche or even air cooled related but my grandpa gave me a truck that he couldnt get running he said it needed a new push rod so i took it. when i opened the valve cover i noticed that the valve keepers fell off and the spring was unnattatched so i put evrything back together and tried to start it only to have huge flames come out the intake. when i took the head off the valve was in the piston and had managed to crack the cylinder wall. (IMG:style_emoticons/default/mad.gif) hopefully your problem isnt as bad but it does sound like your valve is not closing. i would say to check the oil for water but that wouldnt solve anything on an air cooled engine but maybe next time you access your valves you should try to pull on it to see if it goes back any further than the spring.

good luck i am curious to find out what ended up being the problem. hopefully its an easy fix.

[SGB]

Your intake valve is too TIGHT.

[Jake Raby]

Yep, tight intake valve or massive leak down past that valve...

A severe lean condition on that cylinder could cause this as well, but if it's that radical I doubt it.

[r_towle]

Start by loosening the intake on cylinder number three so its REALLY loose.
If the condition continues, you may have dropped a valve seat and you could be proping the vavle open.

Next test would be a leak down test, or just fill the number 3 cylinder with and air compressor and listen for leaks...if you get air out of the carb you need to open up the motor.

RIch

[rhodyguy]

quick checks. how does the syncronometer read as compared to the other clys? what effect does turning the idle air mixture screw in have? count the turns to know where you started. no effect? check idle jet and blow out the circuit.

k

[purple]

Your intake valve is too TIGHT.

Okay, when you say this....does that mean

A: the valve spring is keeping the valve too tight against the seat or

B: the little screw on the rocker arm is too hard against the back of the valve stem?

I ask because if it's B, wouldnt that mean, taken as a whole...the valve is too LOOSE against the seat?

I'm new to this deep a level of engine understanding, so I'm REALLY grateful for your responses.

[purple]

Also, with hydraulic lifters, shouldnt the lifters take care of any tightness or looseness in the valve train to a point?

[purple]

quick checks. how does the syncronometer read as compared to the other clys? what effect does turning the idle air mixture screw in have? count the turns to know where you started. no effect? check idle jet and blow out the circuit.

k

i dont have a syncronometer. i was going to get it running and then have a carb tech tune & synch the carbs.... i dont have enough experience in the black art of carb tuning

[Jake Raby]

Oh... You have hydro lifters.

I think we might have just found your issue..

More than likely one the lifters on that cylinder has collapsed seriously killing the valve's timing.. This will result in the problems you are experiencing and it happens all at once when one of those 5 pieces inside the lifter fails.

Start taking things apart, get that cylinder to TDC and then check the valve lash as you go. Pull the rockers, then the pushrods, tubes and then slide the lifters out and inspect them... Post results and pics and we'll continue to help.

BTW- Carbs are the most simple thing in the world of enrichment.. There is no black art- it is ALL common sense. The only way to learn about themn is to make adjustments and drive the car and keep on till you get it right or break something.

My Carb DVD is on schedule to be shot this summer with Carb Specialist Art Thraen...

[SGB]

Hydraulic lifters are quite a challenge sometimes. I have 'em too.
What we mean is that the valve adjusting screw has been turned in too far. With hydro lifters, I think in terms of "number of turns". On the #3 intake valve adjusting screw, loosen the keeper nut, then turn the screw 1/2 turn counterclockwise. Tighten the nut back down (try not to let the adjusting screw change), put the cover back on, and fire it up. You might need to do it again. The screw slot might more or less align or parallel with the screw slot on the other intake valve on that side if everything is properly symetrical.

Read up on valve adjust (search) and do 'em all for a happy motor.

Jake, wouldn't lifter failure result in a valve that didn't open much?

[rhodyguy]

spend $45 for the syncro and whatever the cb weber book costs. prob cheaper than the first hour with the carb guy. first thing he SHOULD do is ensure the valves and timing are correct. there goes an hour or 2 of shop time and the carbs haven't been touched yet. post a wtb for a syncro in the classifieds. basic tunning/setup is NOT a black art. straight forward and easy with a little thought and some patience. when you get comfortable with your carbs, most if not all of the answers are to be found here and at a few other web sites.

k

[SGB]

Thats absolutely true, you gotta have a synchro tool of some kind. I have the old uni-syn, but there are better...

[purple]

Hydraulic lifters are quite a challenge sometimes. I have 'em too.
What we mean is that the valve adjusting screw has been turned in too far. With hydro lifters, I think in terms of "number of turns". On the #3 intake valve adjusting screw, loosen the keeper nut, then turn the screw 1/2 turn counterclockwise. Tighten the nut back down (try not to let the adjusting screw change), put the cover back on, and fire it up. You might need to do it again. The screw slot might more or less align or parallel with the screw slot on the other intake valve on that side if everything is properly symetrical.

Read up on valve adjust (search) and do 'em all for a happy motor.

Jake, wouldn't lifter failure result in a valve that didn't open much?

Hmmm, is it possible I may have re-assembled the valve train and didnt get the pushrod to seat down into the lifter? I ask because when I opened up the valve cover, the rocker box was really dry, like there wasnt a whole lot of oil getting up in there. is it possible the pushrod is setting on the side of the lifter?

Oh, and to those who say it's NOT a black art....i've futzed around with RC car 2 strokers for something on 8 years, those goddamn things are the most fiddly, annoying carbs to tune. are you saying that big car carbs are different? my dad's always talking about his MGB with side draft webers being a bitch to keep tuned and his old pinto with a weber progressive also being a bitch to keep tuned.

I mean, the sheer number of adjustment screws on these webers alone is enough to make me keep tools away. Methinks a book is in order because i have no f'n clue what most of them do! and dont get me started on this 'jetting' (IMG:style_emoticons/default/screwy.gif)

you old skoolers need to realize that if you havent been around it for 30 odd years there is a bit of a learning curve, just sayin. people like me (had nothing but F.I. cars) our whole lives see these carbs and go (IMG:style_emoticons/default/WTF.gif) how's this thing work?

i'm crabby because my car sounds like a tractor... (IMG:style_emoticons/default/headbang.gif)

[purple]

what's a good sync tool to get? what kind of adapter would i need?

[degreeoff]

You only have TWO screws to mess with....Idle mixture and throttle position. YES get a book and the $50 unisync. Everything else is jets and that requires removal of them to change. (carb on the car procedure)

[mudfoot76]

Next test would be a leak down test, or just fill the number 3 cylinder with and air compressor and listen for leaks...if you get air out of the carb you need to open up the motor.

Back in 2004, when I woke my car up from winter hibernation, it started making funny noise and was down on power. After some tinkering, it started sounding like a UPS truck. Turns out the valve seat dropped on #1 cyl intake. It was puffing out of the top of the carb.

I don't know anything about hydro lifters, but try the leakdown. It sounds to me like you might have lost the valve seat.

[purple]

Next test would be a leak down test, or just fill the number 3 cylinder with and air compressor and listen for leaks...if you get air out of the carb you need to open up the motor.

Back in 2004, when I woke my car up from winter hibernation, it started making funny noise and was down on power. After some tinkering, it started sounding like a UPS truck. Turns out the valve seat dropped on #1 cyl intake. It was puffing out of the top of the carb.

I don't know anything about hydro lifters, but try the leakdown. It sounds to me like you might have lost the valve seat.

for leakdown tests....where do i find an air thing for this?

man, i dont get how i'd drop a valve seat on an engine that's been sitting for just a little bit. I just dont get this. it sucks that I have to pay for all the P.O's neglect and abuse, makes me sad

I guess you were right all those months ago Jake, the engine got over 450, and apparently that's what killed it. God I'm bummed. What do i do now?

[HAM Inc]

If you dropped an intake seat one of two things would have happened.
1) it would have shattered and gone through the piston or it would have broken the valve head which would have done the same thing.
2)the seat turned sideways and stuck back in the head. This is the most "popular" of the two.

If 1) happened it would make an awful racket and you would not (likely) be inclined to continue running it. If 2) happened the dislodged seat will keep the valve way open. If this has happened the offending spring will be very collapsed (as in a valve that is open a lot). Follow Jake's instructions and you'll get it figured out quickly.

[purple]

Hey HAM, i was just looking at your site to see what i'm going to be out if my valves s**t the bed.

I remember rotating the wheel backward in gear and doing valve adjustments and the valve IS going in and out. it's not sitting any further in than the exhaust valve is. at least I dont remember it being any different from any of the other valve springs. i would have noticed that for sure!

I remember the lifter looking really high in its bore when i pulled the rockers/pushrods. this valve was being actuated at the time. i really wonder if i didnt seat the pushrod correctly in the lifter, really.