got a real scare last night during clearance check

[theiceman]

So things were progressing smoothly and I had finished my canm timing and all looked great . next step was to install my exhaust rockers for cylinder one and four and do the interference check from Waynes book ( make sure there is 1.5mm at closest point for intake and 2mm for exhaust. )

Any how as I was doing the checks after installing the exhaust rockers and rocker shafts and was turning the crank and loud quite a loud "pop" like a spring or something and instantly smelled very strong of oil of all things.

I stopped immediately . but could find nothing wrong as it turns out I was fine on my clearances as I had no fly cuts on the head and I was using CIS cylinders.

I was mortified all night wondering if somehow I have broken a ring and if I had how would I know , and is this even possible ?

Then it occurred to me I have been doing the timing , sprockets etc for weeks and never heard this and this was the first time I was compressing the valve springs in my heads on the exhaust side of one and four , Could this have maybe been just valve spring popping into place or something ?

I am not sure what to do at this point and am considering pulling everything apart again to check rings etc.

( these were alusil so I did as the book recommends and took the pistons /cylinders out together and never re-ringed anything. )

any thoughts ?

[cgarr]

The valve springs should be seated when installed, cam gears on right? one side is flipped, was the chain held tight? you can get slack in the chain and it can pop if loose when the cam comes around past centers.

[theiceman]

Originally Posted by cgarr

The valve springs should be seated when installed, cam gears on right? one side is flipped, was the chain held tight? you can get slack in the chain and it can pop if loose when the cam comes around past centers.

yup all checks out , did sprocket alignment sprockets aligned correctly and installed properly, I cant remember if I was in the middle of putting my tensioners back in , that may be it . Not quite sure.

[Mark Henry]

I agree with Craig's guesses.
On the valve springs confirm that you have all the retainer keeper halves and they are all seated correctly.

Did you have the solid tensioner blocks in while setting the cam timing?
I have an extra set if you want to borrow them.

[theiceman]

yeah I think I did . I can quite remember now . I do have them and did use them ( stromski set ) I ust cant remember if I had the hydraulic tensioners back in when doing the clearance check when I heard the unnerving pop. ( actually sounded like a spring breaking or something.
Anyway I decided to move on and will check the retainers as I go . I did put all the rockers and shafts back in last night with no ore unnerving sounds . So the work continues.

[Sway Bar]

I had the exact same thing happen...it does scare you and you think you broke something...I can't quit remember specifics but it had to do with one of the intake rockers being too tight as I began valve timing/checks etc. Back off all your rockers and start the process again.

[Walt Fricke]

Valve springs can break.
Hard to imagine one breaking just turning the engine over manually, but they can. Porsche had a bad batch of springs on one or more years of SC, though I don't remember which. Doesn't explain the oil smell, but what possibly could? Friction from something slipping under high pressure, like a keeper seating or getting loose? But did you have the valves out?

Outers and inners both can break. The test is to push hard on the tip of the valve (or the rocker end (which you should be able to do with the engine on a stand so you can rotate it for good angles. If one feels noticeably weaker than the other or others, it's likely a spring.

You can make a tool like this (with thanks to Will Ferch, who provided the idea back when) to do the pushing.

[Alan L]

You can also do that test with the engine in with a suitably bent tool (steel bar). Handy if having to make a decision to pull the engine.
Alan

[prschmn]

I made this one that lets you use a torque wrench easily enough.

[Walt Fricke]

Mark - I am having trouble understanding how this works.

[prschmn]

Walt, It's the upsidedown picture----
The 90 at the end of the rod hooks under the rocker and the rocker shaft is the fulcrum point
and the 3/8 lets you use a small torque wrench to measure.

BTW--we met once at a Rennsport in Daytona--I'm Judy Hs go to guy

[Dr J]

Same thing happened to me on my rebuild (first and only one). I put the heads and was trying to turn the crank. Had some resistance but at some point had the pop like a spring when I wasnt touching anyhing. Caught me quite by surprise. No oil smell though as it only had assembly lube. I looked through it, checked the valve springs in the head and kept going. Never figured it out and all is running well.

[Mick_D]

Titl of this thread makes me wonder what items weren't on clearance that you thought were....

[boyt911sc]

These were the tools I used for valve and valve spring removal and inspection a couple months ago on a newly rebuilt engine.
These are Porsche special tools P7I and P7E.

Tony

[Steam Driver]

To keep the valve in place while you compress the spring, et al, you could also use the old aircraft mechanic's "rope trick." Fill the cylinder with rope through the plug hole, then rotate the engine to make the piston compress the rope into the combustion chamber to hold the valves in place. Then when you're done relax the pressure on it and pull out the rope. Sounds weird, works great.

[theiceman]

well I did have it buttoned .... up ... all this is making me think about popping the valve covers off while it is on the engine stand and do the spring test as mentioned.

Gotta be way easier now than in the car I would think.

The heads had been rebuilt but only required seals and cleaning as they were well within spec.

If a spring is broken does it all have to come apart again ?

['78 SC]

Broken spring can be replaced with motor in car, obviously easier if motor on stand. Just need to remove valve cover and use tools shown in Tony's post above to compress spring. Intake and exhaust use different tool.

[Mark Henry]

iceman where in Ontario are you?
I don't know if you can borrow those tools, last time I checked they were hard to find and a bit spendy.

I likely could make something using part of the factory VW valve spring compressor I have. Looked at it before, but never have had the need to do it.

[theiceman]

Thanks mark, I'm in Cambridge so not to far ...

I think I'm going to bend a piece of metal first and do the check Walt recommends. I think the broken spring is definitely a possibility . I am hoping something just popped into place but as always , hope for the best but plan for the worst.

[theiceman]

as a side note I can see how these tools fasten on to a stud and then you compress the spring while you remove the retainer . But what keeps the actual valve in place and stops it from " falling in " as it were or just holding steady while you replace your spring or pop your retainer back on ?