Resonance

[mike@thenook]

Good news Andrew, a worthwhile purchase it seems - Happy days again!

[Andrew S]

Thanks Mike but I will be happier when if it is touching anywhere to explain the resonance on the ears I can feel at 2000-2200 revs. Will keep the boxes on though as they sounds so much better

[paul jorgensen]

I bought a Falcon S/S exhaust in about 1986-7 from Hart racing services. When I stripped my car for restoration 3 years and a bit ago, I found the exhaust had some pit holes in it. I had done roughly 9K miles in it in all that time. Most of that time it sat in a dry garage & barn not seeing the light & only being started once a year to bring it out of the garage to wash the dust off, drive it around the block before putting it back.. When I sent pictures to Falcon they never even had the decency to reply. So much for their lifetime guarantee!!!!

[Andrew S]

When I fitted the replacement boxes where the pipes go through the cross members, I had to really pull them outwards when it came to fixing them to the hangers (2 man job) and am now wondering if this is causing resonance as there would be a lot of tension. Rather than take the boxes off again, I am wondering if I could widen the joint on the balancing pipe closer to the front to see if that would reduce tension but not sure how much pipe there is at the moment to play with. The only thought I had was to open the boxes as much as I can at the back to widen the gap and try it with a block of wood first to see if that reduced the tension.

All good fun

[mike@thenook]

You shouldn't need to put/have any tension on the boxes at all - If you fit the whole system loose (don't tighten anything until its all fitted) and make certain where the boxes pass through the subframe there is equal space all around the pipes, tighten those clamps first and then work back to the front pipes. You should find that everything lines up and there is no pulling or pushing.
Also, make certain there is plenty of room around the rear cross pipe between it and the boot floor as if its too close you may get resonance through the boot from it.

I've never needed 2 people to fit an exhaust.....

[Andrew S]

Hi Mike

The pipes that go through the cross members in hindsight I should have pulled apart more as they would not go through the cross member holes enough for the me and Adam to fit the boxes to the down pipes. I agree there shouldn't be any tension and interesting as you comment on the intermediate pipe being too close to the floor as I didn't like the way mine hung down originally so had it cut and tucked up more

[mike@thenook]

If can be hit and miss with the cross over pipe particularly if you don't get the mid boxes far enough onto the downpipes. that will mean the cross pipe is too near the boot floor - stupid design Imo and would be far better with something like Steve's or Neil's twin pipe set up. I've thought about doing similar but time, patience.....

[Andrew S]

I think I am going to buy another intermediate pipe and remove boxes, bend pipes so the go through the cross members better and it should reduce the tension. I am searching for exhaust clamps Mike that have long legs so that I can get that washer on as well as a nut as I cant on mine as it is. Your hanger method is so much better than the original

[mike@thenook]

Don't buy one, I have one here which is fine plus I have some clamps.
Can bring down tomorrow night if you're at the Windmill?

Ive just sent you a gmail...

[Andrew S]

Hi Mike

That is fantastic and much appreciated, see you then

Regards
Andrew

[Andrew S]

Exhaust correctly fitted now and sounds amazing. Very pleased.
Last Sunday I let a couple of experts listen to resonance for their opinion ( Thank you Mike). It was so evident and confirmed I had an engine imbalance. Very obvious on idle at 1200 and 2000 and you could feel it through the and gearstick. After a few suggestions from Mike and others, I checked the crank pulley and TDC aligned to the cam groove and cap. That wasn't it. I then felt the viscous and there was play even though the car running in 1/4 on temp gauge. Fan blade weren't that even either so it was my excuse to buy something new along with a new viscous.
All fitted now and so much better.
My question being that I have still got some resonance but absolutely nothing from cold, it's only when warm so, what else can cause resonance?

Its can be flywheel or clutch as it should be there from cold
Could be plugs or plug
Could be exhaust down pipes changing harmonics as they warm up
Oil pressure is 50 PSI and no knocking or rumbling
Engine mounts were new
Exhaust is not touching bodywork

I haven't tested the car for too long or on the road yet

Is there anything else I can check?

Much appreciated
Andrew

[mike@thenook]

Andrew,

have you got tubular manifolds or standard - sorry I can't remember..

It could well be the heat effect on warmed up pipework and if you have tubular I'd be confident that will be the cause....
but a dodgy plug could also do it - I've had that in the past...

Cheers

M

[Andrew S]

Hi Mike, standard manifolds.

Going to look at plugs but may even consider wrapping the down pipes just to prove the case

Certainly much better and had a run back from toot hill this morning, boxes certainly sound better

Cheers
Andrew

[mike@thenook]

I wouldn't wrap the downpipes - from what I've heard it leads to corrosion of the pipes.

[Andrew S]

Yes, but they are cheap to replace