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Posted by: purple Feb 9 2008, 01:55 PM

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!

Posted by: tagtmeyer914 Feb 9 2008, 02:08 PM

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. 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.

Posted by: SGB Feb 9 2008, 02:17 PM

Your intake valve is too TIGHT.

Posted by: Jake Raby Feb 9 2008, 02:22 PM

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.

Posted by: r_towle Feb 9 2008, 08:52 PM

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

Posted by: rhodyguy Feb 10 2008, 09:13 AM

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

Posted by: purple Feb 10 2008, 11:38 AM

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.

Posted by: purple Feb 10 2008, 11:40 AM

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

Posted by: purple Feb 10 2008, 12:06 PM

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

Posted by: Jake Raby Feb 10 2008, 12:45 PM

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...

Posted by: SGB Feb 10 2008, 12:48 PM

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?

Posted by: rhodyguy Feb 10 2008, 12:53 PM

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

Posted by: SGB Feb 10 2008, 01:12 PM

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

Posted by: purple Feb 11 2008, 10:53 AM

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'

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 how's this thing work?

i'm crabby because my car sounds like a tractor...

Posted by: purple Feb 11 2008, 11:39 AM

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

Posted by: degreeoff Feb 11 2008, 12:06 PM

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)

Posted by: mudfoot76 Feb 11 2008, 12:37 PM

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.

Posted by: purple Feb 11 2008, 01:07 PM

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?

Posted by: HAM Inc Feb 11 2008, 05:16 PM

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.

Posted by: purple Feb 11 2008, 05:33 PM

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.

Posted by: rhodyguy Feb 12 2008, 07:55 AM

the syncronometer to buy, imho, is pictured on the front page at mark harney's site. www.carburetorclinic.com. go there and read the info about your webers. GREAT pictures and text. aircooled.net has a nice writeup too. the syncro is avail from pelican, among other vendors. item PEL-TOL-STESK.

k

Posted by: HAM Inc Feb 12 2008, 09:38 AM

Purple, if you pull your rocker arms off and all of the springs are about the same ht. then the cause is not likely in the head. If you didn't seat the pushrod properly, make sure it isn't bent now.

As long as you have the rockers off it would be a good idea to do a leak down on the offending cylinder to make sure the open valve didn't encounter a rising piston.

Posted by: Brando Feb 12 2008, 03:33 PM

The only reason I can think of for the mixture of air and fuel to spit back out the carb would be the intake valve staying open.

I also vote to follow Jake's advice.

Posted by: purple Feb 12 2008, 03:42 PM

All right you guys, i'm going down to the garage tonight to see what's up. Thanks for all your input and I'll keep you posted with pics and info as appropriate :-)

Thanks to all of you!

Posted by: Cap'n Krusty Feb 12 2008, 06:07 PM

A severe lean condition will make 'em spit back. The Cap'n

Posted by: purple Feb 13 2008, 11:21 AM

well hell!

I had all intentions of going to the garage last night and a buddy calls up with a car that wont start because he ran it all the way out of gas.

he poured in a puny can of gas and i could hear the fuel pump 'knocking around' from priming itself. the car BARELY started but kept running and we got him a full tank.
the car ended up dying a few blocks away and wont start even when jumped. methinks he sucked a bunch of crud into the fuel lines off the bottom of the tank

a 99 maxima, he doesnt maintain it, the oil is black as night, and the tires were 10 pounds low WARM.

people that dont maintain their cars shouldnt be allowed to share the road with the rest of us...

no work got done on the 914, maybe tonight

Posted by: purple Feb 13 2008, 09:15 PM

IT WORKS!!!




I have the P.O. to thank for adjusting the valves to utter slackness on a hydro lifter that i didnt bend a valve or some other terrible buffoonery!

The pushrod did NOT seat all the way down in the lifter bore! I was all... i've gone 5 turns out on this screw and it's STILL IN CONTACT!

Soooo, i removed the rocker assembly off that cyl and checked the pushrod not bent!

i then seated it properly and replaced the rocker assembly when i was treated to the pushrod popping back out and needing to be 'coaxed' back into its home.

anyway, put 2 turns past first contact on TDC of those two cyls, and closed it back up.

I didnt do the other two yet as I wanted to see if what i'd done had any affect. It turns out that yes! yes it did! fired right up! it kinda coughed at first and then got running real, real nice

it's still making its 'booda booda' noises, but i'm going to adjust the valves on the other side and re-check the offending side on sunday.

funny thing....the valve adjuster screws were tightened only 1.2 to 1.5 turns after first contact. Since the lifters were not pumped up fully and the valvetrain was cold, webcam recommends 2 turns in. So I did two turns in. It may be my imagination, but the center of the engine sounds quite a bit quieter now. now to do the other side, which i'm sure is quite loose, hopefully I can quiet it down all the way and then get to synching these carbs! actually, timing first, then syncing.

Thanks to all you guys! you're the best!

OHH, and the long saga of this overheating engine should be over, as far as overheating is concerned....at idle it's 100 degrees cooler than before i put the FIVE pieces of missing underside tin back on....including both lower fan guides(behind the alternator and over the oil cooler) the under-cylinder tin on the drivers side, the rear tins on both sides. yeah....and it still ran. what a hearty engine! Props to you jake for picking a good one!

Posted by: rhodyguy Feb 14 2008, 09:30 AM

you're still not out of the woods on the carb items. great success on the pushrod discovery. HIGH 5!

k