94 Chimaera Intake Plenum R&R

[Guys94Chim]

Greetings all.

Last September I became the proud owner of a 94 pre-serpentine Chim 400. I managed to log around 400 mi on it before winter set in. All I can say is wow, what a ride.

Anyway, I've noticed a small but pesky and consistent oil leak from the valve cover gaskets. Leak is in the same spot on both sides (sort of in the middle), all the bolts are tight.

The plan is to replace the gaskets over the winter. I have new rubber gaskets with built-in spacers.

Couple of questions:
1) The bible doesn't have much to say about removing/replacing the intake plenum. About all I've seen on the optic is "disconnect the throttle stuff", and "remove the 6 bolts that hold it down".
Does anyone know of a writeup that outlines the procedure (hopefully with pix)?

2) Researching TVR this-n-that, I could not find any mention of what (if anything) needs to be done to seal the intake plenum to the intake manifold.
Is there such a thing as a plenum-to-manifold gasket? Or does one use some kind of sealant - if so, any suggestion on something suitable?

3) I found one mention of applying a thin/light bead of silicone sealant to the underside of the valve covers before re-installing with the new gaskets.
Is using a sealant for this recommended (and is there a suggestion on product to use)?

Thanks,
Guy

[Steve_D]

Guys94Chim said:

.....
Couple of questions:
1) The bible doesn't have much to say about removing/replacing the intake plenum. About all I've seen on the optic is "disconnect the throttle stuff", and "remove the 6 bolts that hold it down".
Does anyone know of a writeup that outlines the procedure (hopefully with pix)?

2) Researching TVR this-n-that, I could not find any mention of what (if anything) needs to be done to seal the intake plenum to the intake manifold.
Is there such a thing as a plenum-to-manifold gasket? Or does one use some kind of sealant - if so, any suggestion on something suitable?

3) I found one mention of applying a thin/light bead of silicone sealant to the underside of the valve covers before re-installing with the new gaskets.
Is using a sealant for this recommended (and is there a suggestion on product to use)?

Thanks,
Guy

Both surfaces of the plenum do not have gaskets. simply add a thin smear of sealant like Hylomar.

Rocker cover gaskets are fitted dry. The metal inserts determine the correct compressing of the rubber seal.

Plenum removal/fitting is as simple as it sounds.

Steve

[Sardonicus]

Like Steve said and dont buy white brand/nothing make rubber rocker cover gaskets they're ste and will leak shortly after Elring , Reinz , Unipart, Payen etc

[Belle427]

I seem to remember you can just tuck the plenum to one side and there is no need to disconnect the throttle cable.
From memory disconnect stepper motor wiring and the small rubber fuel regulator hose, intake hose, vacuum advance pipe and throttle potentiometer.
It should be self explanatory really when you look at it, you may have to bend up the mesh panel slightly to get it past.
I used to just put a thin coating of hylomar on it come re assembly time, id agree about just going for standard quality rocker gaskets and there is no need for any sealant on them, just dont over tighten the bolts.

Edited by Belle427 on Saturday 20th January 07:20

[s p a c e m a n]

I use dirka dirka for the plenum. Smear some on and then put the plenum on with the bolts in the holes but don't tighten it up for a couple hours, that way it doesn't all just squeeze out of the gap.

https://www.gsfcarparts.com/elr030-793

[NJ94Chim]

Very helpful, thanks to all.

Have ordered some of the blue hylomar to seal the plenum, should be good to go

[Belle427]

Maybe give the stepper motor a good clean when its off as its much easier to access.

[blaze_away]

The rocker gasket spacers collars are fiddly to deal with. Get yourself a few inches of threaded bar, same thread as the bolts, 1/4 UNF from memory. Cut into 1 inch lengths with a cut slot in the top. Use them in place of the bolts on removal and refit to keep everything in place.

[Sardonicus]

I would permanently stud the upper RC mountings anyway you won't have that worry if lifting the RC and having a spacer/collar then fall into the cam valley area on removal it can happen, the thread is 1/4 UNC

[PabloGee]

Would you threadlock (blue) the threaded bar, or would the engine temperature make that pointless?
Then use locking nuts?
Seems to make a lot of sense to do that rather than bolts. The idea of losing bits into the engine terrifies me!

[blaze_away]

GWIW here is what I do. I use original bolts no thread lock.

To change gasket.
1 remove a single bolt replace with a 1"stud
2. Do the next one, then 3rd and 4th all 1 at a time.
3. Waggle rocker cover loose and remove taking care to make sure the gasket and collars stay put.
4. Once cover is off remove collars then remove the gasket.

5. Clean all the faces and smear with blue hylomar
6. Fit the collars then fit the gasket.
7. Fit the cover making sure the gasket is in right place all round.
8. Remove 1 stud and Fit original bolt then next and so on.
9. Tighten the bolts and check it's all still in place.

Never lost a collar this way. Bot accept that there is merit in fitting studs and doing away with the bolts.

[PabloGee]

Equally, your method is one of a seasoned mechanic with a very neat trick. Love it.
Studs can be a faff if they come loose of course.

[Belle427]

Put a hacksaw slot in the end beforehand and you can get it out with a screwdriver.