Valve Spring Compressor Q. for Tomguy and others

[rix116]

I'm getting ready to do the dreaded valve stem replacement w/ the heads on the car. I've got the seals. I got the compressor that Tomguy recommended
(Ampro from partsamerica.com for $20.)
Went to the jkyd today to practice on a car other than mine. I even took the camshaft off to make it easier (altho I'm definitely hoping not to do that on my car.) The compressor really seems too small- and when you can get it to connect, it merely raises up the bottom of the spring and doesn't push down the top. A retired import mechanic stopped by to chat and said that I needed to use the Mercedes tool which hooks onto the camshaft and pushes
the springs down. I have a mechanic friend who will loan that to me, but I would still love to be able to buy some aftermkt. compressor that would get the job done. The only ones I have found are types similar to the Ampro(too small) or a prybar type that says it is for Chevy's or a big (really big) C clamp
type I think is for removal with the heads off the car(?)
So any help with valve spring compressors would be helpful.
(And Tomguy- I don't mean to single you out and I don't care at all that I may have bought a compressor that doesn't seem to work- I'm just trying
to get some answers so I can do this myself on the cheap w/o making mistakes like dropping a valve down the hole)
Which brings me to my final question. I would love not to hook up an air compressor to keep the valves up. Some have suggested that if I make sure that the cylinder I'm working on is at TDC the valve will definitely not fall down. But another mechanic told me that you need the air to hold the valve up as high as it would go to get the keepers out. I'd love to use rope or something? What do you think?

[Tomguy]

I never thought about doing it with the cams on, to be honest. I don't think it can be done. I dont know how you could remove the rocker arms and then the retainers with the cams on.

The problem is that the retainers "Stick" inside of the top piece. You need to tap the top of the compressor with a hammer to get that out/loose. Then you can pull those off. I don't see how you can remove the rocker arm with the cam on (I've tried!) and then the retainers and springs to get at the old seals. MAYBE if you have hydraulic ball studs or turn the mechanical ones down?

Edit: Oh, and the valve being at TDC should be sufficient. The problem is that the exhaust valve's stem is thicker, so that you can only push the retainer down so far (it's tough to get the keepers out - I suggest a magnetic tool). Actually since I have one sitting on my desk I can show you - this is all the room you'll have to work with. First, exhaust. Second, intake.

[rix116]

Thanks Tomguy!
(For others reading, the car in question is a '74 450 SEL)
I assumed from talking to the two mechanics who did the stem seal jobs
that you do it with the cam on (and the special Mercedesvalve spring compressor that "hooks"to it.)
I certainly could have totally misunderstood.
When you took the cam off, did you unbolt it from the timing chain gear.
I guess you have to carefully mark the position of everything (are there factory marks on it?)
And, I want to totally understand about your TDC comment.
If I make sure each cylinder I am working on is at TDC, does that mean
there is no chance of the valve falling in and can I get the keepers etc. off
without using air?
Any other comments about the cam on or off?

[Tomguy]

I did it with the heads themselves off because I put them on new heads to go on my engine, not the ones on it. So I can't truly answer all the questions. Mercedes may have special tool, I'm just sayin I don't see how you could do it. But when I did take my cams off (twice now), I zip-tied the sprocket to the chain so that it would not lose its position. Of course, I didnt rotate the engine when I did this, so I can't talk much but you'd have to move the cable tie on the sprocket as you rotated the engine.

I'd like to know from someoen who did this job with the heads on if they did it with the cams on or not, too. I really don't see how one could get the clearance in there needed to take the rocker arm out!

[rgnprof]

I did the job on my 72 250 with the tool below - with the heads on. Wasn't really that difficult once I got going and figured it out. I used compressed air to keep the valves up and in place. I am including the link and the description of the tool - probably doesn't work as well as the Mercedes tool, but it's a lot cheaper.

http://www.mytoolstore.com/kd/kdengi13.html#912

Ryan



VALVE SPRING COMPRESSOR
KD 3087 $49.95

Tool compresses valve springs on most overhead valve engines, including GM, Ford, Chrysler, Nissan and Toyota. Tool can be used with cylinder head on or off the engine. Jaws adjust to fit over spring retaining washer, and an adjustable handle allows for easy clearance in tight areas. A GM adapter is included. Use 3269 Fulcrum Rail if overhead cam is not available. Use with 901 or 2992 Air Hold Fittings to keep valve in place. Caution: Vehicle must be placed in park/neutral before applying air pressure, otherwise vehicle may move. Keep hands clear of fan, belts and pulleys since slight crankshaft rotation will occur.

[rgnprof]

Sorry Rix116, I should have specificed that I did not remove the cam on my engine - the compressor 'hooks' on the cam and provides the leverage to compress the spring. I am not real familiar with your engine, but I can't see it being a much different job.

Ryan