Replacing valve stem seals with the engine in car

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bhiggins2
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Joined: Wed Jun 24, 2020 5:54 pm
Dino: Fiat Dino 2.0 Coupe

Replacing valve stem seals with the engine in car

Post by bhiggins2 »

My 2000 Dino coupe is burning oil and smoking out the tailpipe. i suspect valve guide seals more than rings.
Has anyone ever successfully replaced valve stem seals without pulling the heads?
Thanks, Ben.
Gaelicguy
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Re: Replacing valve stem seals with the engine in car

Post by Gaelicguy »

I have rebuilt many engines, from single cylinder50’s motorcycles, complex 6 cylinder Twin overhead cam motorcycles and 4-8 cylinder car engines.
I would say it is vertically impossible to replace the valve stem seals without removing the heads. That can be done with the engine in the car.
The problem is the seals are under the spring caps that are under the cams. If you removed the cams, you still have the problem of compressing the springs and caps, it’s possible, maybe! But you will drop the valve into the cylinder and then you are truly scuppered.
Removing the heads is the quickest safest option in MHO.
Michael
Too many motos and cars, not enough life left! :D
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ThomasK
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Re: Replacing valve stem seals with the engine in car

Post by ThomasK »

There are tools available using compressed air via the spark plug threads to hold the valves in place. I personally haven’t done this until now but it seems far from being impossible. Anyhow you have to remove all cams and camfollowers.
bhiggins2
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Re: Replacing valve stem seals with the engine in car

Post by bhiggins2 »

I was wondering if anyone had tried the air pressure in the cylinders to keep the valves from dropping method and was wondering if anyone had the tool to compress the springs with the head on the block. You have to remove the cams to remove the heads anyway, but you wouldn't have to deal with breaking head gaskets that are functional or draining coolant, or removing exhaust. Making a tool to compress valves on head would not be a problem as there are lots of studs to use for leverage and on to which to bolt something. On American V8s it is done all the time , and there is even the rope in the spark plug hole and TDC'ing the piston to hold valves in place. I'm not sure I would try the rope method on the Dino. I know if I pull the heads I will then do a guide and valve replacement and the car will be off the road for a much, much longer time. If it doesn't work, then you pull the heads.
Ben.
Gaelicguy
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Re: Replacing valve stem seals with the engine in car

Post by Gaelicguy »

I “sit” corrected
😂😂😂
Too many motos and cars, not enough life left! :D
GaryS
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Re: Replacing valve stem seals with the engine in car

Post by GaryS »

If I were to go this route it would be with rope in the combustion chamber w piston at TDC or close. (must remove the spark plugs) The issue here is its quite the gamble to solving the smoke issue, where its most likely a combination of general wear among a few key players - bore, guides, rings. If smoking noticeably and consistently out of both tailpipes I would say its time for a refresh. Try using a high mileage oil, they contain additives that slightly swell rubber, if there is no appreciable improvement that would be an indicator the crux of the problem is elsewhere. Basic guidleines - smoke on acceleration = bottom end. Smoking on deacceleration = top end.
bhiggins2
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Re: Replacing valve stem seals with the engine in car

Post by bhiggins2 »

I actually added some oil additive to help with oil burning. It helped on my 1978 Jeep CJ with AMC360 V8, but on the Dino the smoking at idle got much worse. I hope it didn't swell the seals too much. It doesn't leak oil but a drop or two. I haven't done a leak down test, yet. As you state it could be one or more issues and is pretty consistent from both exhaust pipes. I ordered a kit for replacing valve stem seals without taking the head off. It may be garbage, but I expected to have to fabricate something from scratch for the Dino, so the kit will at least give me some ideas on how to proceed. I will probably test it on my spare engine which is just sitting on engine [heads just sitting on block] stand begging for someone to wrench on it. I will have to get some seals to try installing them and removing them with the valve in place. Does anyone have any advice on whether to go with Teflon or rubber seals? Is one supplier [Dinoparts vs Superformance] better than another for the seals?
Thanks, Ben.
GaryS
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Re: Replacing valve stem seals with the engine in car

Post by GaryS »

To simplify your life as much as possible I would pick the crustiest spark plug on the 4-5-6 (LH) cylinder head and make that the target cylinder. The LH head is much more streamlined to work on. You should certainly get a universal style compressor to make do, maybe a little modification enhancement required, but thats half the fun ... check the deterioration of the valve seal, and drop the piston a little bit (but not too much!) to see how much play there is between the guide and valve stem. That should give you a good overall picture.
Dario
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Re: Replacing valve stem seals with the engine in car

Post by Dario »

Just to add my 2 cents, I found that raising the back of the engine to tilt it forward a little makes a world of difference when removing that last blanking plate on the back of the right camshaft cover.
I would certainly give the in-place valve stem seal replacement a try if I was sure that that was all that was needed. If you still have the original valves, then a top-end rebuild will allow you to replace the sodium-filled ones and the valve seats with hardened ones for unleaded gas. All desirable upgrades that are not overly expensive. It's doable in your garage in about a week if the machine shop has time to do the heads.

good luck,

Dario
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