Noisy #4 exhaust tappet

manoa matt · Post by **manoa matt** » Mon Nov 12, 2007 2:14 pm

After installing a performance tube type 4-2-1 header system I noticed an audible ticking sound, like a noisy tappet. I remembered running across this article and figured that was the problem: http://mirafiori.com/faq/content/exhgasket.htm.

My machinist, who has worked on many fiat heads checked the valve springs, valve guides and valves themselves, also checked for leaks in the head. Everything tested good. I think I was trying to save money by assembilying the cam towers and adjusting the tappet clearances myself, hindsight is 20/20.

The machinist let me borrow several Fiat valve adjusting tools to adjust the tappets. I borrowed the standard double hooked tool like this: http://cgi.ebay.com/BNIP-Genuine-Fiat-t ... dZViewItem. He also let me borrow two individual shim tools like this: http://cgi.ebay.com/FIAT-SOHC-VALVE-SHI ... dZViewItem. And a pry bar that looks like a bent slotted screwdriver.

I got the hang of it, and managed to get all the valves adjusted pretty well. I had a hard time adjusting the #4 exhaust tappet. The cam tower casting and distributor prevent the double hooked tool from being used. The only way of adjusting it that I could see was to use two individual tools on each side of the tappet bucket.

The edges of the individual tools were rounded over from use and they would pop off the sides of the tappet bucket. The valve snapped back several times. I didn't like the snapping valve and figured I would do damage if I continued to let it do that. The clearance for the #4 exhasust is currently at .017 inches. The spec calls for a clearance of .020, and a preference for looser rather than tighter valves.

Here are the clearances of all the tappet to cam lobes as measured.

Intake 1) .019 2) .018 3) .017 4) .019
Exhaust 1) .019 2) .018 3) .019 4) .017

Specs for a 78 are: Intake: .018 Exhaust: .020

Also, when turning the crank pully over by hand all the timing marks line up with their reference points. Holes in the cam pullys line up with marks on cam towers.

When its started up and idling. I point the timing light at the main crank, mark is right on. Point the light at the intake pully, the hole lines up with the mark on the cam tower. When I point the light at the exhaust pully the hole appears about 1 notch off (Advanced). However, it may be my viewing position when pointing the light.

The ticking noise is most noticeable at 2000 and around 2850 rpm.

Should I try to adjust the #4 exhaust again? Is .017 that far off of .020? I figured the #2 exhaust would wear down to .019 eventually.

I imagine the exhaust side is more prone to noise and issues because of the heat and gasses comming up between the sides of the tappet bucket and the cam tower tappet hole when the valve opens.

Matt

So Cal Mark · Post by **So Cal Mark** » Mon Nov 12, 2007 2:47 pm

an exhaust leak from a single cyl can sound exactly like valve noise. If the noise started after installing a header, I'd look at the flange/gasket. Those valve clearances are acceptable as is, though personally I set them up with less clearance than what you've got

manoa matt · Post by **manoa matt** » Mon Nov 12, 2007 3:03 pm

I figured that .003 in wasn't that much. I think the ticking was there before but not as loud as it is now.

When I put the header on I had a choice of two exhaust gaskets. One was brand new and of a lesser quality, The other was an exhaust gasket that only had 300 miles on it, but it had the metal fire rings, so I used that one. I haven't felt any air leaks around the flange and cannot see any carbon buildup around the flange that would indicate an exhaust leak.

I went out and bought some high temp permetex copper sealant gasket after I read the mirafiori article. It should be good to 700 deg. I have yet to take the header back off and apply the gasket compound.

The thing is, when I lean in real close and listen to the cam tower it sounds like the noise is comming from the tappets.

I'll apply the gasket compound tonight to rull out that possibility.

What are your feelings on Marvel Mystery Oil? I added about 3 oz to the oil and that made it a little more quiet.

So Cal Mark · Post by **So Cal Mark** » Mon Nov 12, 2007 3:18 pm

have you looked at the cam lobes to make sure you don't have one going flat?

manoa matt · Post by **manoa matt** » Mon Nov 12, 2007 3:31 pm

Could you draw a quick sketch of what I would be looking for? Would it go flat on the pointed end or the rounded end?

mdrburchette · Post by **mdrburchette** » Mon Nov 12, 2007 9:15 pm

Should you be running a gasket with the header? Usually you can see a black area where the gasket is leaking.

So Cal Mark · Post by **So Cal Mark** » Mon Nov 12, 2007 11:03 pm

only the lobe goes flat

ventura ace · Post by **ventura ace** » Mon Nov 12, 2007 11:54 pm

You can get a cheap stethoscope at your local autoparts store that will help you pinpoint the origin of the sound. I find mine to be quite handy.

Alvon

So Cal Mark · Post by **So Cal Mark** » Mon Nov 12, 2007 11:56 pm

also good for playing dr!
Stethoscopes are under $5 at most tool supply stores, and about $3 at Harbor Freight. Invaluable for determining origins of noises

fiater · Post by **fiater** » Tue Nov 13, 2007 7:57 pm

As Mark said, Your clearances are acceptable, but I like to use .017in. .019exh. A loose valve will tick, but I'm not sure that any of yours are that loose. I'd re adj. your #4 exh. to .019 and while your at it, I'd tighten your in. to .017. When I got my double hook tool I filed the notches a little and it fit the tappets better. It's a tight fit, but I've always been able to use the tool on #4exh. Also I've had great luck with copper rtv. Just use it sparingly. A little goes a long way. I cut the tip to its smallest opening and still go easy.