More exhaust advice required please - manifolds

[dern]

I posted a bit back regarding the buzzing from my exhaust. I thought it was the baffles but sticking my head under the bonnet and revving the engine when hot to about 4000rpm suggested that the problem was not the baffles. It sounds like there's a reverberating buzzy tappety noise from the passenger side at 4000rpm (ish). I know it's not the tappets as (a) I did them not 500 miles ago, (b) it can't be heard at any other rev range, (c) it's too loud and (d) it makes the exhaust buzz.

Edited to add: The point at which I noticed this extra noise from the already buzzing exhaust coincided with the car starting ever so slightly misfire when warm - is this a pointer?

This leads me to believe I've got a leak from the manifold on the passenger side and leads me to ask rather a lot of questions...

Can anyone who's had such a leak confirm that this is what they sound like?

How do I pin point where the leak is, it isn't obvious and I can't feel any gas escaping (I can't imagine it's much or it would sound a hell of a lot louder)?

If I attempt to take off the manifolds and replace them I'll need some really really good penetrating fluid - any suggestion?

I'll probably break at least one stud, if I do, what are my options?

I'm sure I'll think of some more questions but if anyone has any helpful advice I'll gladly receive it.

I don't want a dealer to do the job as I'd rather do it myself and I can't really afford to pay someone to do it. Currently the most complex thing I've done on the car is take the engine and gearbox out, get the gearbox recon'd by someone else, fit a new clutch and put it all back together.

Thanks,

Mark

>>> Edited by dern on Tuesday 28th January 18:53

[gbgaffer]

Best descrption I can think of the noise when I had a manifold gasket blow was that it sounded like the sound you got as a kid riding a bike with a bit of card hitting the spokes

Don't know if that helps

Cheers

Graham

[dern]

It does sound a bit like that.

Cheers,

Mark

[seb]

I had a crack in the manifold on my V8S last summer. The noise was only noticable, when the engine was hot and if accelerating in a high gear (engine under load), as a rapid clicking sound. Mine didn't misfire but popped and banged a lot on the over run caused by air being sucked into the manifold and causing ignition of the exhaust gasses. Mine was eventually pressure tested to prove a leak. On the V8S it was impossible to see the leak as the four manifold pipes run together in two pairs on top of each other in a '88' layout. The split was right in the centre.

[dern]

seb said: I had a crack in the manifold on my V8S last summer. The noise was only noticable, when the engine was hot and if accelerating in a high gear (engine under load), as a rapid clicking sound.

That's exactly what I'm getting.

B*gger.

Any advice from anyone on doing this job?

Thanks,

Mark

[roy_allen]

I had a bit of a rattle on my exhaust about six months ago and couldn`t find what it was at the time. Can`t remember if it was at certain revs or all of the time. What it was, when I eventually found it, was where the 3-to-1 manifold joins to the bend section to go under the car. It had started to come apart. Only found it once it had come totally apart and my exaust sounded like it had a loud-hailer stuck on it!

Roy.

[gbgaffer]

I had a cracked manifold as a result of an enthusiastic encounter with a speed bump, and got it fixed by welding in situ. If your problem is a crack this may work, but if a gasket then no option - plenty of plus gas or wd40 then careful removal of the manifold.

Good luck

Graham

[dern]

Hmm. The manifolds are extremely rusty and when I put new downpipes on in the summer the non-engine end of the manifolds was pretty ragged and also dented inwards by some over enthusiastic tightening of the exhaust clamps. I'm not sure that the manifolds are in a state where it would be worth repairing them either at the point where they are presumably leaking and at the exhaust end to ensure a decent fit. Currently the downpipes are not pushed into the manifolds very far because of the distortion of the manifolds so all in all I think I'll bin them.

Unfortunately the rest of the exhaust is a bit knackered too, it has been repaired a number of times and currently rattles/buzzes somewhere in the 'silencer'.

So, I've been looking at the ACT stainless system which comes in at nearly 800 quid incl vat but not fitting and fitting it myself on the basis that I will enjoy the sound and the looks of the new exhaust while I have the car (at least another year) and the fact that it has a full stainless system on it it will make it easier to sell when I want to sell it (I will have sorted the gearbox, clutch, door hinges and exhaust so will have addressed most of the weak points of the car that would put of potential buyers). It's still a lot of money though.

Has anyone bought an ACT (JP) system? I don't really want the sports system as I use the car every day but I'm concerned that the non-sports system will be substantially quieter than what I have already given that its silencing properties have long since gone south. ACT have offered me the opportunity to specify extra packing and/or smaller bore tubes in the silencer which he assures me will not affect power and will reduce the 'boominess' of the exhaust. He is doing this current to his griff. Any advice?

In terms of removing the manifold - if I run the engine until hot and then pour oil on the manifold bolts, will the oil be drawn into the threads as the engine cools thereby facilitating the removal of the bolts? I was thinking about doing this a few times over a week or so and then using some plusgas on it before attempting to remove the bolts... does this sounds reasonable?

Thanks once again,

Mark

[Podie]

I beleive that Wedge Automotive / RT Racing / whatever they are now called also do a SS system for the S - in both "sports" and a "non-sports" flavour...

[M@H]

AlisonS had a SS system for £450 and that sounded pretty nice...

Matt.

[GreenV8S]

dern said:In terms of removing the manifold - if I run the engine until hot and then pour oil on the manifold bolts, will the oil be drawn into the threads as the engine cools thereby facilitating the removal of the bolts? I was thinking about doing this a few times over a week or so and then using some plusgas on it before attempting to remove the bolts... does this sounds reasonable?

Thanks once again,

Mark

Brake fluid is also extremely good at this as long as you don't let it get anywhere else. Remember though that oil and brake fluid are both extremely dangerous on hot exhausts as they will ignite spontaneously if the exhaust is hot enough. (They are actually more dangerous than petrol, which will normally boil off without igniting.)

Cheers,
Peter Humphries (and a green V8S)

[dern]

Podie said: I beleive that Wedge Automotive / RT Racing / whatever they are now called also do a SS system for the S - in both "sports" and a "non-sports" flavour...

When I checked this morning in sprint it was more expensive than the ACT system but I'll check again as I was half asleep. I'll drop Alison a note to see where she got it from but that sounds like the price for just the system and not the manifolds.

Peter, presumably all I'm trying to do is get the manifolds/head/bolts warm enough to expell some air so it will suck the oil back in not red hot enough to ignite the oil. I'll experiment and have an extinguisher handy

Thanks,

Mark

[roy_allen]

dern said:In terms of removing the manifold - if I run the engine until hot and then pour oil on the manifold bolts, will the oil be drawn into the threads as the engine cools thereby facilitating the removal of the bolts? I was thinking about doing this a few times over a week or so and then using some plusgas on it before attempting to remove the bolts... does this sounds reasonable?

Wouldn`t running the engine until hot have a similar effect as warming the bolt area with a gas torch? If I remember rightly aren`t bolts easier to get out when they are hot?

Roy.

[dern]

Wouldn`t running the engine until hot have a similar effect as warming the bolt area with a gas torch? If I remember rightly aren`t bolts easier to get out when they are hot?

When you heat up metal it expands so in order to get the bolts out you'd need to heat up the head more than the bolt so that the head expands and frees off the bolt. If you heat the bolt and not the head the bolt would expand making the fit tighter and you'd almost certainly break the bolt. If you ran the engine I've no idea which would heat up more, the bolt of the head so I'm not sure if that would help. Also, if you try and undo the bolts while the manifold is still hot you'll probably burn yourself as badly as I did when trying to do exactly the same thing on an old kawasaki of mine .

I *think* the secret to undoing nuts like this is to provide enough lubrication in the thread to reduce the stiction in the bolt to the point where the amount of effort to break the stiction is less than the amount of effort needed to shear the head of the bolt off. Getting as much oil in the thread helps a lot as does applying a good hammer blow to the bolts which seems to have the effect (sometimes) of unloading some of the stiction.

My current plan is to run the engine, switch off and apply oil to the bolts and then bang the manifolds with a hammer to ensure that the bolts are not rusted to the manifolds. I'll repeat this each night until bored and then have a go at removing the manifold bolts.

I'm guessing that the chances of at least one bolt will break so if that does happen, what are my options?
I'm guessing that I'd remove the head and get it to some helpful engineers to get the stud out so is getting the head off easy to do?

Thanks,

Mark

[Paul V]

When I did mine I soaked the bolts in penetrating oil every day for a week but still managed to snap 4 of in the heads, although I managed to get 1 out, the 3 others had to be drilled out, I sent the heads to Ferriday engineering who got the bolts out and reconditioned them while they were off this included 3 angle valve seats, new core plugs and valve guides plus a skim for slightly increased compression for a all in price of about £240 for the pair.

After refitting the car made 180bhp a at san speeds rolling road.

[Justin S]

Mark,you could try heating the nuts with a carefully placed blowtorch ,til theyre red hot and carefully undo.I think there's a nut and bolt wholesaler in Newbury which should be able to supply the correct threaded bolts and fit them rather than studs and nuts with copious amounts of copaslip.

[dern]

It doesn't take much running of the engine before the manifolds get bloody hot (one finger minus finger prints as a result - luckily no burn - lesson learnt) and they cool down pretty quickly. So oil applied for tonight.

I've 'tapped' all 6 of the manifold tubes with a hammer and one rings/rattles loud and clear whereas all the other sound the same so presumably that's the knackered one, can't see the hole/split though.

Justin... I could see that the top bolts exit through the back of the mounting so could use nuts and bolts rather than just bolts but do the bottom ones?

Cheers,

Mark

>> Edited by dern on Wednesday 29th January 20:26

[HarryW]

Don't know if it'll work on exhaust manifold bolts or not, but another trick if all else fails, is to attempt to tighten the bolt to free it .
I know it sounds strange but it has worked on some *#@$ing difficult nuts and bolts for me in the past.

Harry

[dern]

HarryW said: Don't know if it'll work on exhaust manifold bolts or not, but another trick if all else fails, is to attempt to tighten the bolt to free it .
I know it sounds strange but it has worked on some *#@$ing difficult nuts and bolts for me in the past.

That's worked for me in the past to but you have to be a brave chaps to try it on manifold bolts

I managed to snap off one of the water pumps bolts but happily just the head came off so with the pump out of the way and some heat/oil etc I was able to get the rest of the bolt out with mole grips - hopefully I'll be as lucky this time around.

As usual I'll take plenty of pictures.

Regards,

Mark

[chingers]

I was regretfully here last year on a 2.8 (S1)which only has the four exit points. My experience was that the four blind studs at the bottom of each branch came out of the heads without any problem but the open ended studs at the top of each branch sheared no matter how much Plus-Gas or heat I applied. I then had to drill and tap these four holes. The only thing I didn't try was removing the heads first then applying serious heat with a gas torch (ie to red heat) then trying to get the studs out which I've seen used successfully on other applications but not on cylinder heads. On assembly I used studs inserted with copious amounts of copper grease and brass manifold nuts which which don't corrode and are available from most motor factors.
Chris Page