Is it really that time?

[Habbmeizter]

The Griff's been acting a bit strange lately. It started as a strange 'tic' sound at certain RPM's. Then it escalated to loud tics and bangs when I gave it some beans. My first thought was an exhaust leak, as I just recently fitted Clive F's Y-piece.
But today I noticed that the bangs are not from the exhaust, they're from the intake!

I've had many different thoughts of what it could be, and one is a worn cam.

I filmed the sound as well for you to see here: Griff making strange sounds

[paulathome]

That sounds odd.
Have you got a trumpet loose or something loose in the intake pipe.
Just a thought.
Paul.

[THREEFISHORANGE]

Not sure if this could be it, but have heard similar before. The ribbed intake pipe can sometimes tear, could this be leaking air in and making a flapping noise as the air gets sucked through the tear?
Just a thought.........

[Habbmeizter]

THREEFISHORANGE said:

Not sure if this could be it, but have heard similar before. The ribbed intake pipe can sometimes tear, could this be leaking air in and making a flapping noise as the air gets sucked through the tear?
Just a thought.........

I tried disconnecting the pipe from the AMM and it still made the sound, so it's not that. It sounds like it's backfiring through the intake?! Could it be as simple as a bad sparkplug or something similar?
I don't think it's a loose trumpet either.

[Wildfire]

Definitely not the cam. That'd more of a ticking sound. Sounds as if something is not right with the intake or not firing. Have you checked your plug leads and plugs?

[chris52]

Hard to tel from the video but sounds to me like a backfire through the intake. This could be caused by ingnition leads on the incorrect or possibly a crack in the dizzy or leads arcing out to each other.
Chris

[chris52]

Hard to tel from the video but sounds to me like a backfire through the intake. This could be caused by ingnition leads on the incorrect or possibly a crack in the dizzy or leads arcing out to each other.
Chris

[Habbmeizter]

I've been in contact with a mechanic here in sweden who has serviced and rebuilt a few RV8's and he said it definately was the cam.
I bought the car last year at 23k miles, has now done a bit over 30k. Never thought I'd have to change the cam on such short notice!
Recently bought Clive's Y-pipe and had Carl Baker over from UK to fix the alarm and fit a hotstart kit. Now the cam wants to play up. Not the cheapest season I tell you!
Expensive cars to maintain, these Tivvies.

[chris52]

Habbmeizter said:

I've been in contact with a mechanic here in sweden who has serviced and rebuilt a few RV8's and he said it definately was the cam.
I bought the car last year at 23k miles, has now done a bit over 30k. Never thought I'd have to change the cam on such short notice!
Recently bought Clive's Y-pipe and had Carl Baker over from UK to fix the alarm and fit a hotstart kit. Now the cam wants to play up. Not the cheapest season I tell you!
Expensive cars to maintain, these Tivvies.

Hard to see how a cam would make that sort of noise. A worn cam will only reduce the perfomance not make it pop back through the inlet. I would get a second opinion before spending on a new cam.
Chris

[Chilliman]

chris52 said:

Habbmeizter said:

I've been in contact with a mechanic here in sweden who has serviced and rebuilt a few RV8's and he said it definately was the cam.
I bought the car last year at 23k miles, has now done a bit over 30k. Never thought I'd have to change the cam on such short notice!
Recently bought Clive's Y-pipe and had Carl Baker over from UK to fix the alarm and fit a hotstart kit. Now the cam wants to play up. Not the cheapest season I tell you!
Expensive cars to maintain, these Tivvies.

Hard to see how a cam would make that sort of noise. A worn cam will only reduce the perfomance not make it pop back through the inlet. I would get a second opinion before spending on a new cam.
Chris

+1

[EGB]

Check ignition leads first. Bonnet up and check for electrical arcking in the dark. Rev engine on throttle plenum spindle. Should be dark in Sweden by 18.00!

[wuckfitracing]

Leads or timing. Take one lead off at a time to see if revs drop or idle changes. Be careful it will make you jump.

[Habbmeizter]

Will definately check the leads before going further on the cam-replacement path.. Thanks for the heads up!

[A500TVR]

+ 2 - Take a look at this for a 'Worn Cam', I had no noise at all, apparently this is due to the Hydraulic Lifters taking up the play...



Full thread here:

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Chilliman said:

chris52 said:

Habbmeizter said:

I've been in contact with a mechanic here in sweden who has serviced and rebuilt a few RV8's and he said it definately was the cam.
I bought the car last year at 23k miles, has now done a bit over 30k. Never thought I'd have to change the cam on such short notice!
Recently bought Clive's Y-pipe and had Carl Baker over from UK to fix the alarm and fit a hotstart kit. Now the cam wants to play up. Not the cheapest season I tell you!
Expensive cars to maintain, these Tivvies.

Hard to see how a cam would make that sort of noise. A worn cam will only reduce the perfomance not make it pop back through the inlet. I would get a second opinion before spending on a new cam.
Chris

+1

[737 FLF]

chris52 said:

Hard to see how a cam would make that sort of noise. A worn cam will only reduce the perfomance not make it pop back through the inlet. I would get a second opinion before spending on a new cam.
Chris

If it is the exhaust valve lobe which is worn right down, it WILL spit back through the inlet. Personal experience.

[chris52]

737 FLF said:

If it is the exhaust valve lobe which is worn right down, it WILL spit back through the inlet. Personal experience.

Yes I can see how that would happen if the lobe was worn nearly round giving no exit for the gasses to escape through the exhaust they would have to pop back through the inlet valve when that opened. But that would be an extreme case and other symptoms would have surely been apparent long before we got to this stage. The fact that this was only noticed after doing some other work lends more favourably to an ignition/electrical misfire in my opinion.
Chris