| Author | Message | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3663 Registered: 2-2001 |
Hans, The more I think about it it sounds like something on the head of the piston. Also sometimes if a piece of carbon breaks loose from the valve chamber it will roll around and give the same sound. Have you run any top engine cleaner through it yet? | ||
| Richard Stephens (Dino2400)
Junior Member Username: Dino2400 Post Number: 148 Registered: 10-2001 |
Another guess here - have you considered the possibility of an exhaust leak? They can sound decieving metallic. (though I would suspect it would leak more when cold than when hot, but...). 70s Lancias are famous for this problem - owners think their engines are falling apart big time but it's just an exhaust manifold leak. | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 802 Registered: 8-2002 |
Hans old buddy, your vision is going bad. I said, "there is a cover that protects the cats " it is between the muffler cover and diff cover. Magnum | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 666 Registered: 4-2002 |
My old '75 doesn't have cats. At least it doesn't run like a dog. And, yes, I need to set the idle. 16 damn little nuts, washers, spacers.......... | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 798 Registered: 8-2002 |
Hans, could be a vibration? there is a cover that protects the cats that when it vibrates, it's sounds a lot like a valve train issue. | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 797 Registered: 8-2002 |
"My car was making all sorts of weird noises idling at around 700 the proper idle is 900-1200 anything below that the and the engine does not run smoothly and surges" Ditto that Hans. | ||
| Robert W. Garven Jr. (Robertgarven)
Junior Member Username: Robertgarven Post Number: 87 Registered: 2-2002 |
Hans, I cannot hear the noise, and I do not want to speculate as i am not an expert but I do know this. My car was making all sorts of weird noises idling at around 700 the proper idle is 900-1200 anything below that the and the engine does not run smoothly and surges. I was having a noise in my step down gear and replaced all the bearings on that side of the engine just to find out it was the idle. I would definitely call your mechanic though just to see what he said. Rob | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3633 Registered: 2-2001 |
Hans, a nut or washer or whatever rolling around on top of that piston could cause some real damage to the walls and the piston. I wanted to remind you and see if you had the airbox off recently. If you could check it or have it checked with a scope it would be a relief to know it wasn't there. Just a thought. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 643 Registered: 4-2002 |
One of those scopes would be neat. If there is anything dropped down a carb, it probably would have been by me, and I kind of doubt it. I take carefull inventory of nuts, etc. when the air cleaner is off. And, yes, with my socks off I can count to 16. (Saw a small screw eaten and spit out of a Chevy once tho. Rattled for a few moments, then left, seemingly with no ill effects.) | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 2239 Registered: 12-2000 |
Hey Hans, better get that fibre-optic scope to see what's up in there!!! Speaking of dropping things into engines, I've had friends drop insects (sometimes beatles or crickets) down carb throats while the engine is running and they popped out the exhaust in one piece! Mind you, they didn't move much after that... | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3625 Registered: 2-2001 |
Hans, This thing goes on and on and of course is only speculation on everybodys part but here comes another one. Has anybody had the airbox off the car and maybe could have dropped a washer or nut into the carb. venturi by accident? I gotta tell ya it can be done easily. Now may be the time for the surgical scope to check the head of the pistons through the plug holes. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 630 Registered: 4-2002 |
Matt: You might have hit on something. Could it be a bottle cap? Actually, I didn't have an F-mechanic listen to it, but a 'regular' mechanic commented that he'd heard hydralic lifters clatter and stop, clatter and stop, etc. on a small block Chevy in a way that sounds just the same. But he said he didn't have a clue what would cause this on an OHC solid tappet car. Although I'd think that if it were a rod, it would be thru the side of the block by now, I still wonder if the very high oil pressure these cars run at would hide the symptoms of a slightly loose rod bearing. | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 764 Registered: 8-2002 |
Could it be in one of Hans' drunken binges he decided to change his oil and his glass eye fell out and into the oil fill hole? | ||
| Paul Newman (Newman)
Member Username: Newman Post Number: 748 Registered: 12-2001 |
Im also going by the fact that another mechanic has already listened to it and seemed to agree that it was valve train related. | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3623 Registered: 2-2001 |
Paul, No doubt what you say is true but I am going on the basis this thing, if it is a rod, knocking is very light at this point thus creating the effect I just mentioned. | ||
| Paul Newman (Newman)
Member Username: Newman Post Number: 742 Registered: 12-2001 |
I disagree Magoo, a rod knock will get louder with engine rpm when unloaded, say 2-3000rpm. It will also get worse in no time with use. By now, it should be toast. It will go from a light noise to a loud knock and sometimes a squeek along with it. | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3621 Registered: 2-2001 |
Hans, I agree it probably isn't a rod but as you say the noise goes away as you rev it a rod will do the same thing. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 621 Registered: 4-2002 |
Crossing my fingers that's not what's wrong, Magoo. Noise goes away as revs go up. Didn't notice the offending noise at all today, after a round trip of 200 miles. I definitely have some mild tappet noise, and, according to the official maintenance schedule, it's almost time to have my mechanic take the cam covers off. I'll sure miss that money. | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3619 Registered: 2-2001 |
Hans What I am talking about is the car in neutral sitting still and slowly accellerating to those rpms to see if the knock comes in. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 619 Registered: 4-2002 |
Magoo: Oh, yeah, almost forgot: If a rod bearing were a little "loose", wouldn't the F-car's rather huge oil pressure mask the problem? Therefore, maybe it would show up at lower rpm, where the pressure is less? Just wondering. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 618 Registered: 4-2002 |
Magoo: Had a rod go out in a 305 Chevy, as you describe. Trouble with the F-car is that everything back there is so stinking *noisy*, that I'm not sure I'd hear a rod knocking at 2-3K. Hans. (Still pulling cotton out of my ears after a 1 hour trip on the freeway.) | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3615 Registered: 2-2001 |
Rods will usually present themselves at a moderate rpm. 2-3000 rpms with no load,in neutral, on the engine. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 614 Registered: 4-2002 |
James: The thought had occurred to me. You say 'change with idle and load'. How? I have tried lugging it in gear at about 800 rpm or so, as I figure that would exaggerate such a problem. But the noise wasn't noticeable. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 261 Registered: 6-2002 |
Hans - sorry to ruin your day, but have you entertained big-end rod bearing "knocking"? Depending on the clearance, it might sound like top-end cam noise if early in the failure process. The sound will change with idle and load, and with oil pressure. One way to check would be to lift the car and listen from down below. While you assume it is coming from the top end because you hear it there, you might hear it better from below. Sorry for raising this issue. Jim S. | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3600 Registered: 2-2001 |
Sorry Hans, My error. I misread your post. There are tappets I had lifters in mind and typed the wrong word. | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3599 Registered: 2-2001 |
Hans, I know you are concernd. But there are no tappets and the cam lobe rides directly on the shims. Just drive it as has been suggested can give you bigger problems later on. Find out what the problem is because the wear factor could result in high dollar repairs. | ||
| Paul Newman (Newman)
Member Username: Newman Post Number: 697 Registered: 12-2001 |
I would say you can rule out the oil/cam bucket causing the noise. The buckets are a tight fit dry, if yours are flopping, you got bigger headaches coming. I would want to know myself before I took it for some 7000rpm blasts what exactly the noise is. Its an easy cover to remove. If you think its valve related, pull the cover. It would be a costly mistake if you drove it and dropped a valve. Also, if it is simply a shim issue, change it before it wipes out the cam lobe. The surface hardening could be gone and that will certianly toast a lobe. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 591 Registered: 4-2002 |
OK, another suggestion. Fast food and grease made me think of it. If it only occurs hot, maybe it's oil pressure related. When my car is quite hot, oil pressure at idle is considerably less than when cold. Cold > ~90psi. Hot > ~15psi. This is aggrevated by my idle being too low - about 700 rpm (I know, I know. I just got to get 'round to it.) Also, valve parts are steel, the head is aluminum. So..... If the aluminum 'hole' that the tappet slides in expands and isn't filled up with oil at high pressure, there could be a subtle knocking sound. If any of the parts were at all asymetrical, they could cause varying noises as they rotate. Hey, just grabbing at straws here. I don't know for certain if the noise is there at speeds much higher than idle. I don't hear it, but it could just be covered up with the general F-car symphony of sounds going on back there. JRV probably is right. What he said is similar to what my mechanic said: "Quit worrying about the damn thing and just drive it!!" | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3596 Registered: 2-2001 |
Hans, That's the problem. Ferraris don't like to wait in line at fast food retaurants. | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3595 Registered: 2-2001 |
Thanks Jeff. Happy Thanksgiving to you and yours. | ||
| Mark (Markg)
Member Username: Markg Post Number: 312 Registered: 2-2001 |
I have has similar 'tapping' noise come from small leaks in exhaust system, usually a minor gasket breach. However this noise would be consistant but not heat related I believe .... | ||
| jeff ryerson (Atheyg)
Junior Member Username: Atheyg Post Number: 104 Registered: 8-2002 |
Hans Maybe you have a partially plugged oil passage You might change your oil if its been awhile Everyone have a happy Thanksgiving | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 589 Registered: 4-2002 |
It started doing it again. Always happens after I sit and idle in the drive-up lane at Arby's. (Boy am I going to get flamed for that.) Stethoscoped the engine to death. You can kind of hear it everywhere, but it's definitely loudest over the exhaust cam. However, it's equally loud anywhere along the length of the cam. Left, right, center - all the same. I went back and forth, and all over the cam cover for 15 minutes. Same volume along the entire cam. Sounds like a tiny little hammer tapping, not like the 'clicking' of the tappets. Really can't isolate it to a cylinder. Tap-tap-tap-tap. Then gone for 4-5 seconds. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 588 Registered: 4-2002 |
First of all, thanks bunches to all of you, and if I don't hear back from any of you soon, have a happy Thanksgiving. Peter: Definitely only happens when hot. JRV: Tried to stethoscope it today, but it's cold out and I couldn't get any engine temp built up, even after 30 minutes of driving. The 'rhythmic' sound didn't show up. It appears that, at idle, there is slightly more tappet noise coming from #3 exhaust. Slightly, not really too different from the others. Again, thanks all. | ||
| JRV (Jrvall)
Junior Member Username: Jrvall Post Number: 189 Registered: 11-2002 |
Hans, Take a nice calm methotical approach. What's done is done and trying to overthink these deals is a waste of energy...(do you like girls? well use all that extra energy on girls ;^)....I could name a half dozen or more things that could make a noise if I thought you needed to be frieghtened. ;-) Get a mechanics stetoscope...isolate 'the exact location' right down to the reciprocating part making the noise and exact 'type' of noise. Then let's take it from there... Old 308 engines are somewhat prone to cup/shim noise. Anything is possible, but carefully isolate the noise first. | ||
| Dan B. (Dan_the_man)
Junior Member Username: Dan_the_man Post Number: 70 Registered: 9-2002 |
Hans, a weak valve spring will give a valve train tapping noise. It will do this while still idling fine and running good enough not to send up any major red flags (like a miss). Often times it is the exhaust valve spring that will get weak. This is due to the higher heat. If this is the case then this is an early sign of a spring that is fixing to break. I would not suggest to any one with a possible weak spring to drive the car. As for a broken spring, you would have a very rough running car with a very loud valve train noise. Also, it would not run very long before the valve keeper would be "hammered" loose and then you would drop a valve. If you have a weak valve spring, then you will need to replace all of them. It is not wise to go through this much trouble with an engine that you will rev this high and not change out all of the springs. Springs can be changed with the engine in the car and with out taking the head off. Compressed air is on way, but I would recommend the yarn method due to the fact that you won't take a chance of dropping the valve using yarn. This is where you remove the spark plug and with the piston down in the cylinder you fill the cylinder with yarn. then you rotate the crank so as to compress the yarn against the valves. This will keep them closed. remove the cams, shims and lifters, and remove the spirngs. Also, the only sure fire way that I know to check a spring is to take it off and have a machinist (any performance Machinist can do this with his eyes closed) check the valve spring rate and compare it with the factory rate. The only thing that throw's me is that you said it comes and goes with clock work. This could be a vibrating harmonic effect that you hear and still be a valve spring, or it could be the shim as you suggested. I hope you find your problem, but I would take it easy until you do. Dan | ||
| martin J weiner,M.D. (Mw360)
Member Username: Mw360 Post Number: 679 Registered: 5-2001 |
Hans, See what happens when you put your car on the dyno! Hope it's not serious. Martin | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 584 Registered: 4-2002 |
Jeff: The engine definitely isn't missing. I just looked, it's still there...... Actually, it runs real smooth. Slight miss on cold start, but quickly goes away. Probably due to 8000 mile old cold-range plugs. Mitchell/Peter: Didn't realize the distributor had to come out. I was hoping it was just a simple cover ala small block Chevy. I'll do the stethescope in more detail a little later today. This noise isn't real loud. It sounds about what a small block Chevy w/solid cam would sound like when properly adjusted. However, the F-car valvetrain normally seems quieter than that. I suppose that's because the clearances are tighter on the F-car than on most US muscle car stuff. And Matt...... Be carefull or you'll find the 'book from hell' in your Xmas stocking. | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 684 Registered: 8-2002 |
Jeff, That sounds more like Hans then his car.  | ||
| jeff ryerson (Atheyg)
Junior Member Username: Atheyg Post Number: 102 Registered: 8-2002 |
If you have a broken valve spring the engine would be popping/backfiring and missing | ||
| Mitchell Le (Yelcab1)
Member Username: Yelcab1 Post Number: 468 Registered: 11-2001 |
Hans In order to do what Peter is suggesting, you have to do this: 1. Remove the engine stabilizer rod 2. Remove all acorn nuts 3. Best to remove the disti cap, 1-4 distributor, and plate 4. Remove the cross-over oil breather hose 5. Pry up the valve cover, But, you will not be able to see the valve springs, unless you remove the camshaft(s), and that means, 6. Removing the timing belt 7. Removing the camshaft caps 8. Removing the camshaft, and the shim, and the bucket. Now you can see the spring(s). And ofcourse, installation is reverse of removal but twice as hard. Wanna do that much????? | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 2221 Registered: 12-2000 |
Hans, there's the hoses for the oil-vapour system to remove (the one for the pipe that joins the two valve covers, plus the one going into the bellhousing sandwich plate), the distributor and its base plate and the engine brace. The cover may more than likely be silicone'd on, so it'll require careful separation with a spatula-like tool... I forgot, the valve springs are buried within the head and are not visible by just looking down into there. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 582 Registered: 4-2002 |
Matt: You were there. You had your chance. Hans - Keeper of the Hal Needham shrine. | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 677 Registered: 8-2002 |
Hans, Tell him to take a cruise if your bill is to high. Or offer your book in trade. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 580 Registered: 4-2002 |
JRV: Stethoscope - seems to be in the area that I mentioned. Problem, of course, is that noise travels so well thru aluminum. I'll try again tomorrow, a little more thoroughly. Matt: Oil? I think there is some, as when I filled up with gas this evening and pulled out the dipstick something dripped from said dipstick onto the rear (un-heat-shielded) header and caused a lot of smoke! Peter: Not sure about warm/hot, but I *think* it's worse warm. I get some valve clatter cold, but not this weird rhythmic thing. How difficult is the cam cover removal? Or perhaps I should say, the re-install? Is there a gasket there, or is it 'glued' on? Looks fairly straight-forward, but????? I see an oil vent hose, and of course the 'dog-bone' engine mount. I don't have smog pumps, but do have a pump pulley. Other than that, just a bunch of acorn nuts. Am I missing something? If it is a valve spring, can I detect this from inspection with the cam cover off? I'm doubting the valve spring theory, as the noise has been there for several weeks, and I've done 7K a number of times. The noise is just getting slightly louder. Any hints on diagnosing a valve spring? The car last had full service about 4 1/2 years and 11,000 miles ago. Most of those miles have been put on in the last 8 months. I'm planning on belts/valve adjust in the next couple of months. (My mechanic is already collecting travel brochures.) | ||
| jeff ryerson (Atheyg)
Junior Member Username: Atheyg Post Number: 101 Registered: 8-2002 |
My 328 was making a ticking mechanical type noise tested with a stethescope it turned out to be the water pump belt You may also have a pulley bering or a cam bering on the outside of early 308s making the noise | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 2218 Registered: 12-2000 |
It doesn't matter if the engine is cold or hot, it still happens? It's probably shim related, could be debris under the shim that lodges in place, closing the gap, then the shim spins and rocks and frees up the gap (wild theory...). If you're really concerned and if you think its #3 cylinder, at least the valve cover is easily removable and you can actually see ALL of the valvetrain, that is if you think you'd like to do this yourself (no reason why not)... | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3588 Registered: 2-2001 |
Hans, another thing which I am sure you know. Don't do any redlines at this point. As for driving 200 miles? I would flat bed it if it is internal and in the valve train area. | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3587 Registered: 2-2001 |
Not with the spring revolving being loose in the retainer. JMO | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 676 Registered: 8-2002 |
Magoo, Wouldn't a broken spring be more consistant then a shim? M | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3586 Registered: 2-2001 |
Hans, I hate to say it but I think you are right. I think the shim would be more consistent but if not the shim then maybe a broken valve spring. | ||
| Matt Lemus (Mlemus)
Member Username: Mlemus Post Number: 675 Registered: 8-2002 |
Hans, Checked yer oil level lately? M | ||
| JRV (Jrvall)
Junior Member Username: Jrvall Post Number: 185 Registered: 11-2002 |
Get a mechanics stetoscope and try to narrow down the location and type of noise. Then maybe more clues will be revealed. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 579 Registered: 4-2002 |
The 'ole 308GT4 has developed a weird noise that I'm reasonalby sure is from the top of the engine, specifically the valve train of #3 cyl. There is a 'tapping' noise that over a period of a second or two gets louder, then softer. It disappears for 4-5 seconds, then fades in and back out. It is in NO way random, it repeats with clock-like regularity. My wild-ass guess: Something is asymetrical in a valve shim, and it's rotating around with some degree of regularity. Ideas? Should I be scared, or will it wait a couple of months for my next service? I have to drive 200 miles to reach my mechanic. |