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Author Topic: T vent  (Read 2633 times)

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rpont

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T vent
« on: 11 October 2006, 19:13:02 »
Does anyone know what size hole is in the new T vents?

I'm having great difficulty getting any and I'm tempted to drill out the old ones and use them.
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The Barge Captain

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Re: T vent
« Reply #1 on: 11 October 2006, 19:32:01 »
Is this some kind of new mod from Tetley?
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rpont

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Re: T vent
« Reply #2 on: 11 October 2006, 20:21:01 »
Quote
Is this some kind of new mod from Tetley?
:)
No. I'm having to change my lifters and the new type need more oil so you need new T vents in the oil gallery.
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Marks DTM Calib

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Re: T vent
« Reply #3 on: 11 October 2006, 20:24:19 »
The lifters are the same.....ist the oil pump and T vents that changed.....the oil pump had more flow and the T vents allowed more flow to the followers. It was the saab taht had the uprated followers.

Plus, why not simply clean and check your current followers.

I suspect if you were to put T vents with the larger hole on an earlier engine with the smaller oil pump you might end up starving the mains/big ends
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rpont

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Re: T vent
« Reply #4 on: 11 October 2006, 20:57:23 »
The lifters have definately changed and Geffd posted a lot about needing to change the T vents with the lifters.

Three lifters don't pressurise when I put them in oil and pump. I've tried cleaning them but they still don't hold pressure and they were ticking all the time before I stripped the engine down.
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Marks DTM Calib

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Re: T vent
« Reply #5 on: 11 October 2006, 22:06:37 »
Tis states that a new flat based tappet (follower) was adopted, a new oil pump added with 20%+ greater pressure and enlarged oil ways (T vents).

Even with the latest tappets and T vents....you still do not have the oil pump to cope with the changes......these cahneg by the way are liste as model year 97.5
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omegaV6CD

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Re: T vent
« Reply #6 on: 11 October 2006, 22:33:15 »
I think you might have to get the old type of lifters. Where did you get these ones from? why did you not get the correct ones at first place?
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rpont

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Re: T vent
« Reply #7 on: 12 October 2006, 08:44:24 »
I was chatting a long while with Geffd about this trying to decide what to do. He said the oil pump would be ok with just a change of lifters and T vents. The 20% greater pressure doesn't necessarily mean greater volume. The three lifters that failed were next to each other and the reason I took the head off was because I suspected a blockage in that oil gallery but there wasn't one. Maybe the increased pressure and the larger T vent hole was to fix this problem. Geffd did stress that I MUST change the T vents but AutoVaux are having difficulty in getting me them.

omegav6cd: The part number for my lifters is 90542783 (NLS) and I'm told to use 9117904 and those are what I have bought. It would be nice to be able to buy obsolete parts but I really want to have my engine together and running sometime this year.
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Marks DTM Calib

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Re: T vent
« Reply #8 on: 12 October 2006, 08:58:15 »
Well thats contrary to what is stated elsewhere......and I dont agree with his oil pump statement.

But then I also dont agree with the 'just replace the valves and dont worry about the guides' when fixing an engine with a broken cam belt philosophy. Reality is, the guides remain cracked and when they fail the engine eats bits of them!

Having spent many years in engineering deisgn, there are only 3 reasons why you change things

1) You cocked it up
2) You need to add features to maintain/improve market position
3) To cost reduce.

They wont have fitted a bigger oil pump just for the sake of it!

Its your risk......but I wouldn't do it.
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The Barge Captain

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Re: T vent
« Reply #9 on: 12 October 2006, 09:18:52 »
Is there not more to it than an increesed pressure oil pump? should we also not be looking for an increesed flow rate to cope with the larger vents?
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omegaV6CD

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Re: T vent
« Reply #10 on: 12 October 2006, 10:34:35 »
Quote
Well thats contrary to what is stated elsewhere......and I dont agree with his oil pump statement.

But then I also dont agree with the 'just replace the valves and dont worry about the guides' when fixing an engine with a broken cam belt philosophy. Reality is, the guides remain cracked and when they fail the engine eats bits of them!

Having spent many years in engineering deisgn, there are only 3 reasons why you change things

1) You cocked it up
2) You need to add features to maintain/improve market position
3) To cost reduce.

They wont have fitted a bigger oil pump just for the sake of it!

Its your risk......but I wouldn't do it.

I agree with Mark 1million%,  GEffD is a great bloke but i wouldn't take his words for granted, at the end of the day he is a technician not an engineer, there is a big difference between the 2.
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rpont

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Re: T vent
« Reply #11 on: 12 October 2006, 10:58:11 »
 :)
It sounds like I won't have to find another use for 150 quid or so...

To be honest I'd rather change it if theres any doubt at all. Luckily I know someone who can deal with that crankshaft bolt torque for me :)
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Marks DTM Calib

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Re: T vent
« Reply #12 on: 12 October 2006, 11:37:47 »
Not sure that you can fit the later oil pump to the early block....in fact I suspect you cant as the back plate and cambelt idler position is different.

Its a pity GeffD is not about as it would interesting to hear his opinions. Plus he can advise if its possible to simply fit new guides by pressing them in or if they need to be reemed/machined etc for alignment.

I would be fitting the correct followers to your unit by cleaning the ones you have, checking thier condition and replacing the suspect ones.
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rpont

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Re: T vent
« Reply #13 on: 13 October 2006, 20:12:52 »
It seems there is a later oil pump for my engine, part number 90571901 (engine no 08147804) and there are others for even later engines. Presumably that's the one shown in the Haynes book. The only difference I can see is that there is an extra fixing bolt and I won't have the hole for it. Autovaux say about £169.

I'm not sure what you mean about new guides. I've had a look at a couple of good lifters and I can't squeeze them in with a vice though the pistons do seem to be out and not stuck in. I presume I'm correct in thinking that the ones that do go in and out should pressurise with oil in them and that since they don't they are faulty???

Haynes is confusing about getting the oil pump out, well putting it back in really. It says about gaskets but also shows using sealant all around one of the sump bits. Would Omnifit be suitable for that?

I haven't made my mind up about what to do at this stage. I can't see any alternative to replacing my duff lifters with the newer style and that means I have to replace all in a bank since it needs the later T vents but to use them I need a new oil pump. I'm certainly not going to do all of this work and put it back together with an oil pump that I know will cause future problems with lifters. To think all of this started back in February with me wanting just to replace my duff stem seals and expecting to have it finished by June  :)
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