ShopTalk Forums | Aircooled VW Tech & Restoration Help

Can anyone share the telltale signs of of a dropped valve seat in a stock 2 ltr. type 4 bus motor (1976).
Been working on mine major tune, timing, .006" valve clear. etc...starts and runs good, but still think valve clatter is too loud on a couple of cylinders (maybe it,s just me?)Doesn't seem quite as smooth.Revs fine,
Have not done a compression test yet.Have 87k showing on odo.

If the seat drop, you get zero valve clearance...check for worn rockers,valve adjusters and pushrod tips.

Jake if you read this again

Is a dropped seet often detectable by noticing that the spring is extended a little farther with adjuster backed off than the others or is it too suttle for this?

In 2 out of 3 cases in my car, the dropped seat moved the valve inward and not outward. I had about 1/4" of clearance on the one valve the first time... It was very obvious that the valve tip was closer to the head than the rest were.

The last one only showed up as zero compression on that cylinder. The seat kept popping in and out of the head. It was in there, but would not seal.

For the excess rattle, take a look at your adjusting lugs. When they get worn, it gets very difficult to set the adjustment correctly. Also take a look at the valve tips for wear.

--DD

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1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

Dave you mean the spring looked more compressed, I thought a dropped seeat was when the seat ressesed it self farther into the head.

They can move either way according to the events inside the engine....

a stem that sits a tad further out is an indication of a stretched valve also.....I would suggest a tear down before your engine ends up like my blown 914 engine that luv bug destroyed with a dropped valve....

Valves do not play!

Valves do not play!

Nor do they compress when forced between a piston and a head...

I had a 79 bus that dropped a seat. Most times it ran fine, other times it would miss at idle and loose power when the seat shited and the valve would not seat completely.

If you are loosing clearance it could be doing both recessing into the head Or stretching the head off the valve (Jake's 914 engine). I wouldn't take chances, if the valve head pops off, your whole engine is toast. If the seat gets slammed so much it cracks, at least your piston it toast. I usually have the 'holey piston Batman' syndrome with my cores...

Are you sure you don't have Hydro lifters(76 engine)? I noticed the .006 lash mentioned... After they pump up set them to 1/4-1/2 turn past 0 lash. Check out: http://www.bostonengine.com/articles/valvecov.htm
and the other articles at Boston Bob's site, they're really great.

[This message has been edited by Bobby74 (edited 11-16-2002).]

The thought of hydralic lifters being in this engine occured to me..
True or false, I can pull pushrod covers and rods ,and remove a lifter to confirm this while motor is still in bus?
Thanks for all the advise guys!!

True... Buy you don't even have to do that much! When the engine is cold remove the valve cover. Use a screwdriver between the valve retainer and rocker arm and pry gently. The lifter will give before the valve does if its a Hydro lifter. This question has been answered many times and a quick search will show it. Read the Hydrolic lifter article at the bostonengine website, it will explain it. Look under articles. Good Luck!

There are quite few VW busses around here, college town. The students can't move them across the street for alternate parking in the winter snow season so if they don't run you can get some hellish deals this time of year.

I piped in on this post because I was wondering if there is a fast and dirty visual way to spot a dropped seat. While helping those in my club, so far I have run into 2 Vans that this was all that was wrong--found this by removing the heads. Not to tough to fix with another used head --at least until it happens again.

No one around here to fix a T4, I'm surprised that the T1 shops won't touch the things they just aren't that different especially when stock. I think the FI scares the few with aircooled experience around here.

I just got another Vangon, 83 camper for $350 bucks even had a rebuilt tranny in it. I buit a stock T4 for it with the help of Jakes video. Man it's a nice bus especialy for town driving BA6 heater and all--warm in the winter what a joy. Took me a weekend to get it back up. Probably get at least 2.5 K for it now.

Ya know I have had the wrong idea all this time--the two seat problems I saw, two different T4's the seat was recessed back into the head.

From what you all say this is not a dropped seat. Neather of these came loose and scatered in the combustion chamber.

Alsehendro, I don't recall if the spring looked compressed or not. I was too busy staring at a valve tip that was somewhere between 1/8" and 1/4" closer to the cylinder head than the rest...

I had thought that a valve seat moving toward the outside of the car was called "recession". By that way of thinking, a "dropped" seat simply means one that has come out of the cylinder head into the combustion chamber.

--DD

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1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

In reference to a recessed valve seat; Is there a step machined into the head to "bottom" the seat against? or can the seat just keep going into the ports eventually?