Home  |  Forums  |  914 Info  |  Blogs
 
914World.com - The fastest growing online 914 community!
 
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG. This site is not affiliated with Porsche in any way.
Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners.
 

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
> #4 Cylinder intake valve stuck open
gnomefabtech
post Mar 19 2023, 09:20 PM
Post #1


Member
**

Group: Members
Posts: 80
Joined: 27-December 22
From: Los Angeles
Member No.: 27,063
Region Association: None



So I'm trying to resurrect this 76 (or is it a 75?) that I just bought and it doesn't have compression on the #4 (rear right) cylinder. After some tests with compressed air it's clear that the intake valve isn't closing. I pulled the valve cover and the rockers move OK but that valve does not close all the way. Everything else looks good.

I have a lift but was wondering if I could pull that head without dropping the engine. It looks like there is room but I'm not sure about the engine tin etc. Seems like either the valve is bent or somehow stuck and maybe I can just fix the one thing there.

Anyone pull heads while the engine is still in the car?

User is offlineProfile CardPM
Go to the top of the page
+Quote Post
VaccaRabite
post Mar 19 2023, 09:27 PM
Post #2


En Garde!
**********

Group: Admin
Posts: 13,407
Joined: 15-December 03
From: Dallastown, PA
Member No.: 1,435
Region Association: MidAtlantic Region



Valve seat is probably dropped. You need to pull the head off. You can do it with the engine in the car but it’s not any fun. Don’t run the engine!

Top end rebuild time.

Zach
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
gnomefabtech
post Mar 19 2023, 09:37 PM
Post #3


Member
**

Group: Members
Posts: 80
Joined: 27-December 22
From: Los Angeles
Member No.: 27,063
Region Association: None



Thanks for the reply. I'll pull off the intake and maybe be able to see if the seat is dropped. No idea if it ever ran in this condition. I never ran it.

Are dropped seats a common thing on these? The motor looks like it's never been opened and is totally stock.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
930cabman
post Mar 20 2023, 05:45 AM
Post #4


Advanced Member
****

Group: Members
Posts: 2,977
Joined: 12-November 20
From: Buffalo
Member No.: 24,877
Region Association: North East States



QUOTE(gnomefabtech @ Mar 19 2023, 09:37 PM) *

Thanks for the reply. I'll pull off the intake and maybe be able to see if the seat is dropped. No idea if it ever ran in this condition. I never ran it.

Are dropped seats a common thing on these? The motor looks like it's never been opened and is totally stock.


Yes, the valve seats do fall out of their recesses with these aluminum heads. Being 1/2 century old, chances are the motor has been opened at some point. Drop the engine and remove the heads as a start.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
VaccaRabite
post Mar 20 2023, 06:03 AM
Post #5


En Garde!
**********

Group: Admin
Posts: 13,407
Joined: 15-December 03
From: Dallastown, PA
Member No.: 1,435
Region Association: MidAtlantic Region



QUOTE(gnomefabtech @ Mar 19 2023, 11:37 PM) *

Thanks for the reply. I'll pull off the intake and maybe be able to see if the seat is dropped. No idea if it ever ran in this condition. I never ran it.

Are dropped seats a common thing on these? The motor looks like it's never been opened and is totally stock.


So, yes an no.
I re-read your first post this morning with a non-sleepy head and there are some things we should confirm.

You describe #4 as "Rear right." That would be Cylinder 3.
#4 is passenger side forward - the one that is deep in the cooling tins.
Cylinder 1 is Driver rear (shallow)
Cylinder 2 is Driver Front (deep)
Cylinder 3 is Passenger rear (shallow)
Cylinder 4 is Passenger front (deep)

For all the cylinders, the intake valve is the inside valve, and the exhaust valve is the outside valve (when viewing the cylinder bank as a paired set).

Cylinder 3 exhaust the most common valve to fail, followed by cylinder 3 intake. This is because Cylinder 3 is the hottest of all the cylinders due to the airflow under the tins, and the exhaust valves run hotter then the intake valves as the intakes are getting cooled by fuel.

I guess the first thing you should do is make sure the valve is not set super tight and the adjuster isn't holding the valve open. This may likely to be the problem, but it is easy to check, and you need to check valve clearance anyway. AND!!! A overly tight valve is often a sign of a failing valve seat. Or its possible whoever did the last valve check just really buggered up the job - but all things given I think that this is not likely.

I'm also assuming that the engine spins free by hand. If you tested compression and the engine did not lock up or make very bad sounds, that's promising. Another indication that the seat is failing but has not failed.

So the prognosis is better then it was last night when I was posting from bed, but still not great. But there is hope the last person to set valve clearance was just ham handed and got over tight.

Obviously if the valve pops, it will lock up the engine, or damage the piston, or damage the rod, or all three. This is something you want to be SURE about before starting the engine.

Zach
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Superhawk996
post Mar 20 2023, 07:08 AM
Post #6


914 Guru
*****

Group: Members
Posts: 5,673
Joined: 25-August 18
From: Woods of N. Idaho
Member No.: 22,428
Region Association: Galt's Gulch



Drop the engine.

First - because that is the proper way to work on a 914 engine. Mid engine cars don’t lend themselves to doing work on the engine as installed. This is true of almost any mid-engine car.

Second - almost all of these cars have been used and abused over the last 50 years. Gaskets and seals have dried out. Oil and gunk has clogged the oil coolers. Mice and rodents have been inside the engine cooling tin and have set up house or have left debris inside the tin.

The reason that engines drop valves and valve seats is from being overheated. This can be due to build up of gunk on oil coolers and cooling blockages or engines that were run in a poor state of tune (lean and/or timing too advanced). The proper way to prevent this is to start by pulling the engine and making sure the cooling system is up to snuff.

2 of the 3 engines engines I’ve torn down had issues that would have led to serious overheating had they been run 1st before teardown & cleanup.

Are you sure this isn’t your engine?

Mouse house
Attached Image

Blocked oil cooler - gunk and oil
Attached Image

Blocked oil cooler on 911 engine
Attached Image

Another very common issue on these engines is the number of people that have pulled the cooling flaps. Urban legend of the 80s was that removing the flaps would help prevent overheating. In fact, flap removal creates overheating because you loose the airflow through the oil cooler. These engines are not only air cooled, they are oil cooled. A bypassed oil cooler greatly increases the chance of overheating the engine.

So drop the engine. It’ll be easier to work on and while it’s out you can properly inspect and clean it to ensure it cools properly.




User is offlineProfile CardPM
Go to the top of the page
+Quote Post
technicalninja
post Mar 20 2023, 09:23 AM
Post #7


Senior Member
***

Group: Members
Posts: 1,042
Joined: 31-January 23
From: Granbury Texas
Member No.: 27,135
Region Association: Southwest Region



SuperHawk- that is BEYOND nasty.
Do people really remove the air flaps for the oil cooler?
Drop dead stupid!
I'm going to remote mount my oil cooler, remove the flap, and make another by hand to replace what I removed to force all the air through the fins.

In the AC world the cleanliness of the heat exchangers is paramount.
A system that looks like those engine picks would not work very well at all.

I'm in agreement with everyone else- Check valve clearance first but if you don't know the history of the drive train removing it for inspection is a good idea.

If it looks like SH's pictures you will save it from destroying itself.

Those pictures are what I call a "time bomb"...
User is online!Profile CardPM
Go to the top of the page
+Quote Post
TrailerParkBoy
post Mar 20 2023, 09:56 AM
Post #8


Newbie
*

Group: Members
Posts: 8
Joined: 7-February 23
From: PNW
Member No.: 27,145
Region Association: Pacific Northwest



This is number four. A few weeks ago. Now doing full 2270 rebuild.
These were original 2.0 heads. Advice here was replacement, 50 years is past due!


Attached thumbnail(s)
Attached Image Attached Image Attached Image
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
brant
post Mar 20 2023, 10:11 AM
Post #9


914 Wizard
**********

Group: Members
Posts: 11,584
Joined: 30-December 02
From: Colorado
Member No.: 47
Region Association: Rocky Mountains



QUOTE(technicalninja @ Mar 20 2023, 09:23 AM) *

SuperHawk- that is BEYOND nasty.
Do people really remove the air flaps for the oil cooler?
Drop dead stupid!
I'm going to remote mount my oil cooler, remove the flap, and make another by hand to replace what I removed to force all the air through the fins.

In the AC world the cleanliness of the heat exchangers is paramount.
A system that looks like those engine picks would not work very well at all.

I'm in agreement with everyone else- Check valve clearance first but if you don't know the history of the drive train removing it for inspection is a good idea.

If it looks like SH's pictures you will save it from destroying itself.

Those pictures are what I call a "time bomb"...



You don’t have to make a new flap
For racing. We used to add two sheet metal screws to the stock flap to force full air through the cooler

Be cautious to always pre warm the car and oil since you loose the warm up of a thermostat

Not ideal for the street use
As the stock thermostat design does work well
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
gnomefabtech
post Mar 20 2023, 10:47 AM
Post #10


Member
**

Group: Members
Posts: 80
Joined: 27-December 22
From: Los Angeles
Member No.: 27,063
Region Association: None



Thanks for all the input. I guess I'll drop the engine and see what's what in there. I have a really great shop with a lift and trans jack so I'm guessing I can drop the engine in an hour or so. It looks like it could use a new engine wiring harness as well because all the wires are very dried out.

The stock thermostat is still there but it's disconnected (of course).

The rest of the car is COMPLETELY rust free.Check out this pic of the hell hole. I've never seen one that still had the original metal.
Attached Image
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
930cabman
post Mar 20 2023, 11:14 AM
Post #11


Advanced Member
****

Group: Members
Posts: 2,977
Joined: 12-November 20
From: Buffalo
Member No.: 24,877
Region Association: North East States



Thanks for the great shot of an original hell hole, I have never seen this before. Good information for putting one back together where who knows how the factory intended the seams, ...

BTW: (IMG:style_emoticons/default/welcome.png)
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ClayPerrine
post Mar 20 2023, 11:21 AM
Post #12


Life's been good to me so far.....
***************

Group: Admin
Posts: 15,367
Joined: 11-September 03
From: Hurst, TX.
Member No.: 1,143
Region Association: NineFourteenerVille



I know the original poster found his problem, but I wanted to add something that I saw on a 2.0 head.

The head was old enough that the valve seat started to recess into the head. Every time the valve closed, it hammered the seat deeper into the head. Eventually the valve stayed open. I readjusted the valve, thinking it was just too tight. It ran fine for about a week before the valve was too tight again.

These are 50+ year old heads. At this point in time you are better off buying the new heads that are available rather than trying to use the ones you have.

Just my $ .02.

Clay
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
gnomefabtech
post Mar 20 2023, 11:30 AM
Post #13


Member
**

Group: Members
Posts: 80
Joined: 27-December 22
From: Los Angeles
Member No.: 27,063
Region Association: None



Thanks for the welcome. I'm a seasoned Porsche user, having owned a few tail draggers in the past, but am always ready to learn about the 914 stuff. This 75 just fell in my lap but I'll get it running at least and let someone else enjoy it's rust free glory.

My main project is a '73 that will have a "non Porsche" powerplant in it. I'll share that build once I have some more pieces in place.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
930cabman
post Mar 20 2023, 02:03 PM
Post #14


Advanced Member
****

Group: Members
Posts: 2,977
Joined: 12-November 20
From: Buffalo
Member No.: 24,877
Region Association: North East States



QUOTE(ClayPerrine @ Mar 20 2023, 11:21 AM) *

I know the original poster found his problem, but I wanted to add something that I saw on a 2.0 head.

The head was old enough that the valve seat started to recess into the head. Every time the valve closed, it hammered the seat deeper into the head. Eventually the valve stayed open. I readjusted the valve, thinking it was just too tight. It ran fine for about a week before the valve was too tight again.

These are 50+ year old heads. At this point in time you are better off buying the new heads that are available rather than trying to use the ones you have.

Just my $ .02.

Clay


Or a 1/2 century
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Shivers
post Mar 20 2023, 06:20 PM
Post #15


Senior Member
****

Group: Members
Posts: 2,292
Joined: 19-October 20
From: La Quinta, CA
Member No.: 24,781
Region Association: Southern California



QUOTE(gnomefabtech @ Mar 20 2023, 08:47 AM) *

Thanks for all the input. I guess I'll drop the engine and see what's what in there. I have a really great shop with a lift and trans jack so I'm guessing I can drop the engine in an hour or so. It looks like it could use a new engine wiring harness as well because all the wires are very dried out.

The stock thermostat is still there but it's disconnected (of course).

The rest of the car is COMPLETELY rust free.Check out this pic of the hell hole. I've never seen one that still had the original metal.
Attached Image


Nice. I was surprised too after seeing the battery tray, and cutting it and the metal behind it out. The HH looked really good, below it too.

Attached Image

Attached Image
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
gnomefabtech
post Mar 20 2023, 07:21 PM
Post #16


Member
**

Group: Members
Posts: 80
Joined: 27-December 22
From: Los Angeles
Member No.: 27,063
Region Association: None



I guess fortune smiles upon some of us! Did you cut out the battery tray to replace it?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Shivers
post Mar 20 2023, 11:22 PM
Post #17


Senior Member
****

Group: Members
Posts: 2,292
Joined: 19-October 20
From: La Quinta, CA
Member No.: 24,781
Region Association: Southern California



QUOTE(gnomefabtech @ Mar 20 2023, 05:21 PM) *

I guess fortune smiles upon some of us! Did you cut out the battery tray to replace it?


Yes I have one to go in. But I have tp weld in a patch first
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
robmac571
post May 10 2023, 12:42 PM
Post #18


Newbie
*

Group: Members
Posts: 1
Joined: 23-January 21
From: Seattle, WA
Member No.: 25,114
Region Association: Pacific Northwest



QUOTE(TrailerParkBoy @ Mar 20 2023, 07:56 AM) *

This is number four. A few weeks ago. Now doing full 2270 rebuild.
These were original 2.0 heads. Advice here was replacement, 50 years is past due!


@TrailerParkBoy who are you going to for your rebuild? I'm also in need of top end rebuild and am in the PNW.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post

Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



- Lo-Fi Version Time is now: 28th March 2024 - 04:44 PM