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Discussion Starter · #1 ·
I have had oil consumption issues for a while now with 2 different blocks and a few heads. I have torn it apart again and am going to bring it back for a re-hone and new rings. I checked leak-down with great numbers and comp is 190 across. I have been trying to track this problem down for a while when something just ocurred to me...Both times the engine has been rebuilt the machine shops(two different ones) made the mistake of setting the guides up too high so the stem seals got smashed. After the problems were resolved, I was sure I had the gotten rid of the consumption, but it would still happen. Both times I would wait a while before checking the seals thinking the motor was using a bit more oil due to break-in. I understand the break-in process takes place very early in the motors life...so my question is...If the motor was using oil in the beginning would this prevent the rings from fully seating? This engine was putting down 142 whp and 130 ish for torque so it was making ok power...any ideas?? also towards the end before I took it apart it would use a quart in 3-400 miles if driven hard.
 

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Re: question about break-in and a problem.. (Dubmekanik)

What oil are you running and what pistons and rings are you running?
 

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Re: question about break-in and a problem.. (EDV)

When the head was rebuild where the valve stems spec'ed to make sure they where thick enough and not worn? Are you still using the original pistons? What is the skirt to wall clearance? If the bores are too ovaled then the rings may not be sitting square in the block. It may be time to get new pistons and get everything back to round from an oval. Just to check everything, are you sure the oil is being burnt and not leaking?? Not trying to be a smart ass just making sure that everything is being looked at.
Here is a link to some break-in thoughts:
http://www.mototuneusa.com/break_in_secrets.htm
 

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Discussion Starter · #5 ·
Re: question about break-in and a problem.. (vwmann1)

Thanks for the replies all..use 20-50 all the time and not synthetic..oil is not leaking anywhere out side the block. Didnt use motomans break-in method, although I will when I get the block back. Stock pistons .50 overbore with whatever rings came with the pistons..builder isnt sure what kind
Just got back today to find out 2nd and oil control rings way out of spec when compared to top ring. Top ring .015 gap and 2nd ring .035...why would this be??. Engine builder says seems like cylinder walls got hot , but oil temps have never gone above 200 degrees at any time. Nor water temps. I used to have 16vs that would see 220-30 all the time, which is why I went the extra mile to assure the block would be a bit cooler( oil cooler, low temp thermostat and fan switch. Guides, stems were all put in new along with pistons, rings, and fresh robore/hone. Thanks again for any help from everybody....
 

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Discussion Starter · #7 ·
Re: question about break-in and a problem.. (ValveCoverGasket)

Sure I guess they could have..This shop mainly deals with race stuff so is it possible they may have bored a little over to gain some extra hp or to make room for forged pistons? Would there be a different bore size for cast or forged pistons of the same piston diameter? Also why would only the bottom 2 rings be out of spec, while the top ring was ok gap wise?....any thoughts even remotely related to this subject would be greatly appreciated...
 

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Re: question about break-in and a problem.. (Dubmekanik)

Yea man, I have had the same problems............ What I thought was piston rings turned out to be valve stem seals, and now I am still burning a little bit of oil under hard driving and I really dont know why
It is about 1 quart every 600 or so...
I should add that the gap was a little off for the piston rings with the exception of the top. The oil scraper ring and middle ring were at the end of the worn tolerances.. I think I could simply used poorly machined piston rings. Deves piston rings offers file to fit rings... I think I will go with them next time.

What is your piston to cylinder wall clearance? Mine is very tight, .001 The Bentley I believe specifies .001-.003 thousandths for the clearence on a new motor. Mine is .001, but I have often speculated if this wasnt "too" close. I am going to be building another motor here soon anyways, but I sure wish I new what was up.
I am pretty sure that the problem is only on one cylinder, and I have to do a leakdown test to confirm that. What did your leak down test look like???
Also, I here tha 20-50 is bad to break a motor in on.... tooo thick. A good mechanic friend of mine said to just run straight 30 weight valvoline for the first 300 miles or so, then switch to some 10w30. I would also try to follow the motoman break in method as closely as possible. When I was breaking mine in I sort of followed it.... I'll think about this some more and try to do a little research...
Can anyone list the exact specs they built their "no problem" motors with??? I never had problem one with the first motor I built..... too bad it got broken when the damn oil spout fell off the pre-assembled oil pump, I was just too inexperienced at the time to check those bolts.



Modified by CrackerX at 7:09 AM 5-24-2004
 

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Re: question about break-in and a problem.. (Dubmekanik)

wierd, this was a duplicate post


Modified by CrackerX at 3:52 AM 5-26-2004
 

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Discussion Starter · #12 ·
Re: question about break-in and a problem.. (CrackerX)

I dont know the piston to wall clearance...I didnt think to do it before I took it back to the machine shop. The piston did seem to rock when I put it in upside down into the bore. It seemed like way too much though. I wish I would have checked it..
I think 600 a quart is alot to be using..I had him change the seals recently when I found them smashed(intakes) but they were okay when I checked them this time. The leakdown numbers were really good 2-3 percent. I did notice a drop of oil at the base of the guides on the intake side of the intake set I was checking the guides on
I heard it is possible to leak around the guides too...but how could I check this? This is atleast the second set of guides put in this head since it was rebuilt. The machine shop had to recut the seats when installing the new set of guides that were lower.Thanks for the reply cracker..
 

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Re: question about break-in and a problem.. (Dubmekanik)

Yea I had the same problems with the guides... The first set sat too high and my 268 cam were smashing the seals. It turns out that the guides were actually machined wrong. They were a couple mm too long. After getting the correct guides I had them cut down somewhat just to be extra sure that the seals would not get hit.
The thing is, I know if I go pull off my intake right now I will have buildup on the backside of some of the valves. Probably the same thing on some of the exhaust. The buildup is noticeable and makes the valves look wet. Well....
Let me ask you this... I dont see any visible smoke in my exhaust unless it is night time and someone with bright headlights is behind me. I ONLY see the smoke after i open up the 2nd butterfly on the throttle body a little bit. There seems to be a direct corolation between how much the throttle is open and when it smokes. Do you notice this????? I would think that bad piston rings would be bad all the time, especially at low loads when the force from the explosion is less. This would have less force pushing past the piston rings causing them to press less against the cylinder wall.
On my motor I honestly dont think it is a pistong ring problem but something to do with oil getting by the guides or valve stem seals.... If I get 2-3% on a leakdown I will be very happy!
 

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Discussion Starter · #14 ·
Re: question about break-in and a problem.. (CrackerX)

I hear you on that....did you check the side play on the valves when they are in the guides? I also noticed that they seemed to move a lot more than I remember on the other heads I did for customers. They could be rocking just enough to spread out the stems up top..just a suggestion. I would only smoke when at wot also and yes it was only noticeable at night when looking through someones headlights. Do you use less if you never go wot? Would you be able to drive 500 miles not going wot??...lol...prolly not. I did this test before when the stem seals were bad and it used the same amount going fast or not. I didnt have the patience to do it again after the head was "fixed" finding out I still had oil consumption. I am going to the machine shop hopefully tomorrow to check a few more things out....Thanks
 

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Re: question about break-in and a problem.. (Dubmekanik)

You know... there might be a little play in the valves.... I bet that is what it is honestly.... or something along those lines, I wonder if the increased airflow might cause the valves to rattle in the guides if they are a little loose or something like that. The first motor with zero problems had all 16 guides replaced in the head, and new intake valves. I sold that rebuilt head to a friend and he has no problems with it either. My machine shop had me replace my exhaust guides because some were kind of loose in the head, but I wonder if some of intake guides are worn... or if the valves are a little worn or loose. I will pull my intake off to install some ITBS here soon and I will take a look and try to see if any oil is going around the valves again. It was really obvious to spot last time I had it apart.
And to answer your question I went 1000 miles driving it easy and only burned about 1/2 quart. Yes, it was extremely painful to not floor my car. I did do a few necessary times though
When my valve stem seals were smashed no matter how I drove it burned oil like crazy.
 

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Discussion Starter · #17 ·
Re: question about break-in and a problem.. (CrackerX)

Did you have the same block with that other head? And you werent using a lot of oil? Or how much were you using? What is the total amount of lift on your cams? Did you ever try to vent the valve cover with any improvements? Oh yeah...are you using a 1.8liter head?


Modified by Dubmekanik at 11:05 AM 5-26-2004
 

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Re: question about break-in and a problem.. (Dubmekanik)

Quote, originally posted by Dubmekanik »
Did you have the same block with that other head? And you werent using a lot of oil? Or how much were you using? What is the total amount of lift on your cams? Did you ever try to vent the valve cover with any improvements? Oh yeah...are you using a 1.8liter head?

Modified by Dubmekanik at 11:05 AM 5-26-2004

I wish I had the same block that I had the head with no problems on... It used 0 oil and ran awesome... Unfortunately both the block and head have changed so I dont know which is the current source of the problem.
I had schrick 268's when the valve stem seals were crushed, but due to a broken TT valve spring incident which resulted in a dent and then hole in a lifter.... a cam lobe on the 268 intake cam wore down and it got a nice flat on it so I am now back to running stock cams.
It is a 2.0L head right now, I will be putting together a 1.8L head soon. I have vented the valve cover, and I have virtually 0 blow by, which is another reason I think that its something in the head that is the problem.
 

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Discussion Starter · #19 ·
Re: question about break-in and a problem.. (Dubmekanik)

Hey Cracker...just wanted to thank you for all the replies...Did you break the current block in with smashed stem seals?
 

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Re: question about break-in and a problem.. (Dubmekanik)

Hey now problem, I am as interested in finding out whats going on as you are...
The bottom end should be well broken in by now... 6000 miles. It is the same one that had the smashed valve stem seals. I should be getting a leak down test kit soon, so hopefully I can find out if a little better whats going on.
For the break in I basically just did 10 or so hard pulls to 60 in 3rd gear (5000 or so RPM) from about 30mph and let the engine decelerate the car back down to 30. I then changed the oil and drove it around varying the RPMS while occasionally doing some hard pulls never exceeding 5500 RPM. After about 500 miles I just started driving it like I stole it again.
 
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