Precats

[sheel]

Got the "Y" piece off at the mo ready to fit Clives masterpiece, my cats are all in and I want to remove the pre cats, however as its summer (ha ha) I would rather not take the manifolds off in case of broken bolts etc, I can see the precats, is it possible to beat them out insitu or would you leave them till the winter when its probably better to take the manifolds off

Thanks Guys
Rich

[debaron]

Some chaps have had an easy time of it removing the precats. I can only speak from experience and there's no way I'd have managed to get mine out with them still on the car. Took about an hour a side of bashing, smashing, swearing and sweating! Of course yours might be easier...

[Harrytsg]

I took mine out while they were still in the car, and had the same experience debaron had, except my back ached as well as I had to lean over to do them.
All went back together ok though.

[SILICONEKID350HP]

Wear a mask ,its poison .

[sheel]

Cheers guys, think they can wait till the winter, have a slight blow on a mani gasket, can do that at the same time, don't want it off the road at the moment cos I bet there will be other things if I start taking it apart!!!!!!!1

Rich

[QBee]

sheel said:

Cheers guys, think they can wait till the winter, have a slight blow on a mani gasket, can do that at the same time, don't want it off the road at the moment cos I bet there will be other things if I start taking it apart!!!!!!!1

Rich

It's fairly likely the manifolds will be blowing at the 4>1 union too. If it was me (and i have a Clive Y-front on order too), I would do one of two things:

1. Leave the pre-cats in and not worry about them, or
2. Wait until winter, get the manifolds off and give them to a tame welder, who will cut them open, weld up any defects in that union, take your pre-cats out, and weld them back up again. Neat job (mine have been done, so I can post up a pic if you want), and far less hassle. Only issue will be if you cannot get the head bolts undone.

I will also keep my old Y-piece, and so be able to be MOT legal in 45 minutes by swapping it back in.

PS, I had issues with 7 of the manifold bolts, one thing led to another, and I ended up with a different engine.........

[sheel]

Qbee, cheers for that, exactly what I was thinking!! its all good at the mo,but bet your bottom dollar something horrible will happen if I take it apart, Clive pipe only for now, and yes,I will do the same and keep the original down pipe!!

Regards
Rich

[fatboychim]

I removed mine in situ,
I just worked at them with an extra long masonry bit and a chisel. It was a bit of a sweat but not too bad.
Remove the lambda 's first though and hoover out afterwards.

[chris1972]

There's more than one way to skin a cat!

I removed my manifolds. The first pre-cat took me about 90mins to 2hrs to remove. The second about 45 mins. In hindsight, I definitely would't have wanted to remove them in situ. However, I think this all depends on the individual and the condition of the pre-cats. Reading through the forum, some have had the pre-cats come out with ease, whereas others have been hammering away for hours. If they're in good condition it is likely they will be well seated and harder to remove.

My thoughts are only based on my own experience of removal::

1. Try and remove the manifolds. If you don't try, you won't know. If you get completely stuck, simply bolt them up again. Nothing lost other than time.
2. If you get the manifolds removed, you can remove the pre-cats, slot the bottom bolt holes on the manifolds, fit new gaskets and replace with bolts/ studs
3. Hammering the pre-cats in situe can't be good for the bolts and gaskets. If they're flakey now, then smashing the cats out won't make them any better.
4. Or; leave the exhaust gasket replacement and pre-cat removal until you're ready to do a complete job.

The job is really a pain in the @rse. I can't say in the short time I've been out in it since the pre-cats have ben removed that I noticed a massive difference. A few more pops and growls, more when changing gear, which is nice. As for volume, not a massive difference. I think the biggest difference will come when I get the decatted Y-piece on.

Once you get a technique for putting the exhaust manifolds back on, you can actually do it much quicker. I had to take my manifolds of three times due to forgetting to do things before I put them back on . However, I got them back on in less than 30 mins a side by the time I got to this stage!

Here's what mine looked like. HTH:

Pre-cats in


Smashing re-cats out


Slots cut in manifold lower bolt holes

[fausTVR]

I'd say give those faces a good file-up as well for good sealage.

[Alun450]

I've still got pre cats in but main cat removed, even so there's a big power gain, much cooler and in my opinion better fuel economy, noisy but the engine seems much happier.
Less over fuelling at low and high revs it seems, after all my concern it's worked a treat on my car Sheel.

[Harrytsg]

Alun450 said:

I've still got pre cats in but main cat removed, even so there's a big power gain, much cooler and in my opinion better fuel economy, noisy but the engine seems much happier.
Less over fuelling at low and high revs it seems, after all my concern it's worked a treat on my car Sheel.

How does it fair at MOT time?

[Alun450]

Not good that's why I have my original intact! A hassle to swap but once you've done it a couple of times its easy enough.
The gains are so obvious its a must now I know! The noise is outrageous, I have to admit it's like a proper Tvr now and on the fosseway yesterday it was pure GT. I can easily get wheel spin in third at 80+ on bumpy roads again!
Is it the noise but it's like going from a road engine to a race engine, such a difference! I did 200 odd miles yesterday Tesco 99 fuel and the cars never been quicker, it sounds like there's an extra litre in there!

[chris1972]

Alun450 said:

Not good that's why I have my original intact! A hassle to swap but once you've done it a couple of times its easy enough.
The gains are so obvious its a must now I know! The noise is outrageous, I have to admit it's like a proper Tvr now and on the fosseway yesterday it was pure GT. I can easily get wheel spin in third at 80+ on bumpy roads again!
Is it the noise but it's like going from a road engine to a race engine, such a difference! I did 200 odd miles yesterday Tesco 99 fuel and the cars never been quicker, it sounds like there's an extra litre in there!

I can't wait to get mine back from the welders and that PAS hose sorted

[sheel]

Left the pre cats in till winter, Clive Y in now and run up, sounds awesome, not been out on the road yet but its certainly loud with a sleeved exhaust !!! Thanks for your replies
Rich

[Digger]

Alun450 said:

Not good that's why I have my original intact! A hassle to swap but once you've done it a couple of times its easy enough.
The gains are so obvious its a must now I know! The noise is outrageous, I have to admit it's like a proper Tvr now and on the fosseway yesterday it was pure GT. I can easily get wheel spin in third at 80+ on bumpy roads again!
Is it the noise but it's like going from a road engine to a race engine, such a difference! I did 200 odd miles yesterday Tesco 99 fuel and the cars never been quicker, it sounds like there's an extra litre in there!

Standard silencer alun?