308 Loud noise...

Between 3000 - 4000 rpm is where you get all the ressonance occurring. I have seen this in a few cars and the following are the most common causes.

1) Loose cam belt cover bolt
2) Loose bolt in one of the heat shields
3) One of the 4 bolts holding on the aluminium sump protector to the rear of the engine, missing or loose

 

I will also add A/C lines rubbing against inside of inlet scoop. Solution: wrap the line in some foam pipe insulation.

 

Also a lose A/C compressor bolt will make the same sound.

 

I had same problem and was able to fix. Sounds like its only 5th gear? Do you have same sound at rest (3000RPM)?

 

my 78 euro 308 GTS has the same vibration at about 2800 - 3000 rpm,, no matter what gear. still cant figure it out...

 

I asked QV London about this once before. Harmonic frequency of crank. Happens again (more vicously) at 9,000 rpm (why they only recommend 8500 for the race motors).
Philip

 

my 77 308 had a droning noise around 2800 rpm and it was the camshaft drive bearings. If it is these it is not a good idea to go on long journeys.

A 'rubber pipe in the ear' helped to find the problem. The bearing failure also often causes oil leaks from the seals due to the increased shaft movement and this in turn can buggerup the alternator. How do I know??

 

Obviously there a number of faults that can cause noises and these need checking out (my 308 had a cracked cam belt cover that made an awful metallic noise at high revs)...

BUT if there is nothing apparently wrong with the car and the noise only gets to you on longer journeys... but some foam ear plugs!

I'm not taking the mickey, they cost a couple of pounds from Homebase and the other DIY outlets and I've used then for years, on my last car, for journeys over say 40mins.

NOTE: the ear plugs quieten the sound, but your ears adjust and you can still hear everything albeit muffed tone, so I never felt I was missing anything.

SAVES PULLING THE CAR TO BITS!

 

I had a very similar problem with my 328-extremely annoying resonance which started about 3000 rpm and was completely gone by 3500. It was almost non-existant when reving the car in neutral but very pronounced when the car was on the road and moving. It occurred in all gears. Turned out to be the A/C lines which run along the firewall. My mechanic gently bent them away from the firewall and I noted great improvement. I would suggest putting the car on a hoist or jack stands and going underneath and looking for ANYPLACE where metal is close to, or touching, metal and think about isolating the two components either by foam encapsulation or very gentle persuasion. While underneath, a general "tightening up" of any fasteners might help the situation as well.

 

It is funny but that is sound I live for. I think it is a harmonic vibration from the carbs and airbox. The heart of every ferrari is the engine, listen to it, feel it, live it!

 

Thanks Andy,

I have a set of QV wheels which were an option on the euro car in 78-79 they look greta fit perfectly and are the exact same design just 1" biiger all arounf. Mike at Superformanse in the UK has repo wheel which are a great deal and look essentially the same and they are aluminum which is good cause the mag wheels present a whole set of challenges painting.

I would suggest a tubi exhaust, I am the cheerleader for them here it seems but at my low wages it was still the best value I ever got for my money, makes the car come alive with increased throttle response and the sound is amazing in a tunnel it will send chills down your spine! But I am a engine nut and dream the v12 dream!!!

BTW it is all the other weird sounds you need to look out for

 

Robert
Spoken like a true enthusiast.
Philip

 

I have read all of the posts with interest, but none pointed to the solution my mechanic came up with on my 81 308. I had an irrating noise coming from the right rear that sounded like a bearing going out. Definately a squeal-type noise or squeak happened ONLY when the car was in motion except on the freeway or smooth roads. Around town, it was an embarrasment. I fought this noise for a long long time and, to make matters worse, my old mechanic could not hear it because he has limited hi-fequency hearing. I switched mechanics (a guy that can actually hear) and discovered the problem immediately once the car was on the lift. My motor mounts had failed and the engine dropped down 3/8 to 3/4" of an inch and the bottom of the engine was rubbing in (no less than) 8 places. The worst of the rubs was the front heat sheild covering the header was resting on a part of the chassis and was actually getting a dime sized hole punched thru the sheild from the chassis.

If you are going to put the car on a lift, I would suggest you check the condition of your motor mounts. I have almost 90K on the car and they were pounded down pretty good.

Bruce McKinney
81 308

 

Andy,

I am not much of a mechanic (that's why somebody else does the work for me).....but the mounts are certainly worth taking a look at while you have the car in the air. I beleive that some Ferrari motor mounts are actually oil-filled. Even if yours are not, 26 years of being exposed to the air does have an effect on rubber. Definately take a peak....if they appear to be compressed (as mine obviously were) it could solve some of your intermittent squeaks around town.

On my 308, they did not have to pull the engine to replace them - which saved a heck of alot on labor. I guess you can jack the engine up from below enuf to drop in the new mounts. I don't know about a gt4.

Good luck!

Bruce

 

A/C lines and also check the covers over the exhaust manifold. They are crimped and welded in place and have insulation. The can come loose and start the same type of resonance.