zero bar on cylinder n.4...valve stuck??

[GinG15]

dear all,

please check the attached pictures which a 3.5L engine:

"the problem" started as follows:

the car was not running smooth anymore (and it wasnt used much for a long time)...checked with infrared thermometer the exhaust manifold temperatures: some did not warm up as quick as others or even at all.

new plugs...and besides 1 cylinder, they all fired up correctly.

compression check on cylinder 4: zero bar

rocker cover of--> exhaust valve is lower than the others...but only the valve...not competely with spring cap, collets and spring.

whats is wrong here and how could this be caused?

Edited by GinG15 on Tuesday 25th December 21:58

[The Hatter]

Wow that's an interesting one...

Collets sitting low in the spring retainer? I don't see how that can be wear, those components should be locked together when the engine is built and never move relative to one another... unless the valve spring breaks, or is unfeasably weak.

What's the history of the engine, has it been meddled with in it's lifetime or is it original? My guess is it was put together with mismatched components and it's always been like that; and that the 'misbuild' has gradually caused another problem to develop. Looks like head off, valve out and investigate...

Edited by The Hatter on Friday 7th December 18:29

[GinG15]

this is the engine featured in the book "How to Power Tune Rover V8 Engines for Road-track" from Des Hammill

it was used for racing in the 750s series from 2002 to 2005, than the car was used only for weekend blasts....and was driven approx. 500 miles in this 8 years

[Wedg1e]

Valve spring retainer fractured, allowing the collets to pull through? Even if the piston had struck the valve and bent the stem, you'd just expect the spring to stay compressed as the valve could't come up... interesting one.

[The Hatter]

Ah a race engine, different kettle of fish altogether. I'd guess a high lift cam, solid lifters, big valves, beefed up springs etc... ie a lot of stress on the valve gear. I'd guess a broken valve collet/stem/retainer; could do serious damage if it hasn't done so already. Got to be stripped down; but you could start by taking the rocker shaft off and see where the valve retainer sits relative to all the others; I'd guess it's sitting high or it may actually come off the valve head - in any case it'll give more information.

Edited by The Hatter on Friday 7th December 19:06

Edited by The Hatter on Friday 7th December 19:10

[GinG15]

from i was told, the tuning stage of this engine is not too high. but i have no prove nor any documents about anything on the engine.

inductionwse it runs on SU carbs. i wont have time do do anything on that engine this weekend, but next step is to take off the rocker-gear o ceck the level of the spring retainers.

but on first view it looks like the level of the retainer on cyl. 4 is equal with the other ones.

what i forgot in my first posting:

when the engine is running, on cylinder 4 it could be heard a clear tick...tick...tick noise...no idea if its comming when the rocker-arm is touching the valve or the piston touching the valve.

Edited by GinG15 on Friday 7th December 19:49

[Campbell]

Can you see if the inner spring is in one pice as a broken spring would hold the valve open and posibly damage the top coller and allow the colets to drop in.
If i were you i would remove the rockers set on that head and tune the engine to tdc on that cylinder before you that you can fill the cylinder with washing line so it will compress upto the valves, you can use a spring compresser to remove the springs and check the valves and springs...

Cambelt

[Jack Valiant]

Agree with Cambelt and Hatter had a similar issue on my old 400SE it was the inner valve spring had broken, ended up having to replace the valve as well...

Chris

[GinG15]

can anybody determine if the retainer caps look standard?

i checked at rimmer brothers webpage about the valve springs...they list individual inner springs only for engines upto 1976...for engines from 1976 only sets of springs are listed.

my next problem is: i dont know the age of the engine...also the V5c says under engine-no: "unknown"

how can i localize if a engine is the "older" type or not?

another pic from differnt angle:

Edited by GinG15 on Saturday 8th December 08:34

[pwd95]

Here is a pic of my old J.E. 4.5. No idea if the valve gear is standard or not but gives you a comparison.....




& here's the reason I had a tick tick tick & zero compression!!.........

[Wedg1e]

GinG15 said:

can anybody determine if the retainer caps look standard?

The look the same as on my engine (as does the rest of the rocker gear)...

http://www.wedgeneering.co.uk/TVR%20390SE%20p2.htm

(scroll down a bit, the pic isn't great but the retainers do seem to have the same outline and proportions).

[GinG15]

for me "my engine" looks rather standard than extremely tuned/uprated.

maybe this engine is a standard 3.9L fitted with SU Carbs? maybe a slightly tuned 3.5L? maybe a heavily tuned 3.5L which does not show its tuning on first view?

has anbody Des Hamills book or a link where i might get it downloaded?

Edited by GinG15 on Saturday 8th December 18:37

[adam quantrill]

There are two springs one inside the other. I think you'll find that the inner spring is broken, so the valve and collet are dropping in a bit, but when the rocker comes up the collet is pulled up by the cap. Also the collet is probably worn badly so it's loose in the hole.

As the valve isn't closing properly quickly enough that's why you've got no compression.

The head will have to come off to fix either the spring or collet unless there's a way to stop the valve dropping into the cylinder - anyone know any bodges to do this the easy way?

[carsy]

If you get that piston to the top the valve shouldnt drop and be lost in the cylinder. You can then compress the spring and renew springs, collets, and cap.

Neal1980 on the Chim forum recently changed a spring this way without removing the head. Cant remember how he compressed the spring though. Maybe a quick mail to him to confirm how he did it. I think he posted a picture at the time.

[Manicminer]

You can feed string in through the spark plug hole to make a string bed then turn the crank until the piston reaches the top. Valve won't drop into the cylinder that way.

Make sure you leave a decent tail of string sticking out of the plug hole though

[carsy]

Sorry cant find a pic but from the thread, neal1980 made a plate that fitted over the spring cap. Presume rockers off and then this plate was screwed down via a rocker bolt hole thereby compressing the spring. As i say maybe worth contacting him he may well still have the tool he made. Hope that helps.

[GinG15]

i´ve all the necessary tools for removing the springs to replace e.g. valve stem seals without removing the head....thats not a problem.

for example compressd air adaptor which fits in the park-plug hole, avoiding the valve dropping down.

lets hope that its "only" a broken spring or broken retainer...i would be more than happy not needing to take off the head.

[hallsie]

GinG15 said:

i´ve all the necessary tools for removing the springs to replace e.g. valve stem seals without removing the head....thats not a problem.

for example compressd air adaptor which fits in the park-plug hole, avoiding the valve dropping down.

lets hope that its "only" a broken spring or broken retainer...i would be more than happy not needing to take off the head.

An air compressor adaptor wont work if the valve is leaking by giving you the zero compression in the first place?!!?!

The washing line in the spark plug hole and getting the piston to the top is the best way before taking off the head!

Stu

[GinG15]

as long as the valve is free it will lift up against its seat when air will be supplied in the combustion chamber? thats what i hoped.

[adam quantrill]

It's worth a try although if the valve is chipped or badly seating it won't stay there with compressed air - but then it's head off time anyway, so nothing to lose.