tapping noise

[Stingray74CC]

Wow it's been a while since I've posted on here, but I am in need and I know I can always depend on the good people here at CACC.

Here's the story...

I had leaky carbs and every now and then I'd find gasoline pooled on my intake manifold. Apparently it got really bad and began leaking into my intake. I went to start the car and it turned over but didn't start. I tried again and WHAM nothing...tried one more time and the same thing. The starter tried to turned over the engine but couldn't do it. Great, gas in the cylinders. So today I took the carbs off, tighten all the connections, replaced the gaskets, and replace the fuel lines and blocks. Put everything back together and she started right up. That was a good feeling.

But here's the problem, I am now having a little tapping noise from what sounds like the number seven rocker. It speeds up when the rpms go up and slows down at idle. It made some noise before but nothing this loud. Did I bend a rod a little or just push the rocker out of place? Any ideas?

Thanks for the help,
Anthony

 

[Stingray74CC]

update

I tightened #7 rocker arms 1/8th of a turn and the noise has stopped. Now here are a couple follow up questions:

I am having some backfire now during deacceleration if I leave the transmission in gear. This may be because of fumbling around with the carburators or can that happen from valves being too tight. The car idles fine, revs fine and comes back to idle. It does idle pretty high (1500-2000) when I first start it though. It returns to a normal idle (750-800) after I tap the gas once. There was no backfire issues before I began the initial work.

Thanks everybody,
Anthony

 

[MoeJr]

The tapping may be a lifter that got washed out with all the gas(presuming the lifter is hydraulic). The backfiring may be raw fuel getting into the exhaust. U may wanna readjust the idle mixture screws if you didn't after fixing the carbs. 1500-2000 rpm is a normal Hi Idle for warm up so that shouldn't be of concern. Did u change the oil at this time cause that could be thinned out from all the gas if ya didn't. Hope this helps.

 

[cruzer99]

Sounds like the carbs are too rich.......I adjusted them by closing each mixture screw until the engine started to die then open 3/4 turn. Do this on all of the mixture screws.

 

[92ghost]

Here's a thought. Are you running a Holley carb. Check your floats for leaks in the carb. I had a similar thing happen to my 72 Camaro (w/Holley) the float was getting water logged (with fuel) and not closing the needle valve to the bowl. It was intermittant at first but when the float lost all FLOAT it just poured gas into the engine.

I think you solved your tap problem. However, the suggestion to change the oil or atleast check to see if the oil level has risen in your pan indicating it has been diluted with fuel is a good suggestion. Good luck.

 

[Stingray74CC]

I did change the oil. I didn't notice the level any higher but I figured it couldn't hurt to change it. One issue I am having with my oil is the pressure. I looked around at other posts and saw that normal pressure at idle is between 25 and 40 psi. I used to get 40 while driving at 3500 rpm. I run 15 50 Mobile 1 Synthetic; with that high viscosity oil, there should be a decent pressure. Now I'm not getting a reading at all at idle and barely any reading while driving. The temperature is fine and the egine sounds normal.

92ghost:

I should check the floats in the carbs. I do have Holley carbs. There is still some fuel on the intake after driving a few miles but nothing like before. The thing is that I just had the center carb rebuild about 8 months ago by Recarbco.

 

[cntrhub]

The rebuild may have distorted the carb body and now you have a leak between the gasket near the top cover? You need to fine which carb it is before i assume it's the rebuild? This is where you might want to check the fuel leak? Float level is trying to close, but that leak (tweaked cover) keeps the float open just enough to seep out around the (warp) carb halves. Contact clean the carb from the top down. Now you have a dry and oil free carb assembly. Too bad you couldn't add some kind of blue color ink into the gas tank and then you could see where the fuel is leaking exactly. Hopefully it's not the center carb Recarbco had a hand on?
If you were having a tappet noise on #7, I would have reset the whole bank, since I had the cover off. Then gone to the other side and reset the rest. It may be ready for a valve adjust if you had the valve job recently.....just assuming again.

 

[Stingray74CC]

Valves were set this past spring when I had the valve stem seals replaced so I'm hoping they're ok. They could probably use a once over anyway.

On the carb gas leak, I'm sure it's the center carb that is leaking. I should contact Recarbo and see what they're policy is on that. Probaby 6 months...just missed that.

As far as the backfiring, I did try to adjust the idle some. The car didn't sound like its usually lumpy self when I got her back together...she sounded smooth. A little adjusting of the idle got the lump back but the backfiring is still there. I'm not great at adjusting this Holley. If anyone has any helpful hints, I'd appreciate it. Does it mean anything if I close the mixture screw all they way and the car does die? This happened on the drivers side...the passenger side didn't kill it but made the RPMs drop when it was all the way closed.

Thanks for all the suggestions. Hopefully I'll be back on the road again soon.

Anthony

 

[cntrhub]

Backfiring on deceleration is generally caused by a lean condition in the low speed circuit. What happens is that the mixture leans out enough to where is fails to ignite consistently. This, in turn allows some un-burnt fuel to get into the exhaust pipes. Then when the engine does fire, these un-burnt gasses are ignited in the exhaust pipe, causing the backfire. I would say check the idle and low speed circuits, and set them a bit richer. It is hard to do this right without some rpm sensitive equipment.

 

[JohnZ]

STOP running it until you find the cause of no oil pressure! You may have hydraulic'd one cylinder due to the fuel leak into the manifold - this usually bends a rod, or at a minimum, wipes out a rod bearing. If it started to crank and then suddenly stopped with the key still in the "start" position, that's what happened. If so, it's time to drop the pan and start pulling rod caps to check the bearings (look at #7 first). If the rod is bent or its journal on the crank is scored, it's teardown time.

Worry about the carb later - find the oil pressure problem first before you do more damage.

 

[Culprit]

Stingray74cc,

Listen to JohnZ.

When did you stop getting an oil pressure reading? Was it at the same time as the failed start attempt? Did you recently switch to synthetic oil or have you been using that all along?

I sent you an e-mail.

Semper Fidelis and Beat Army,
Culprit

 

[cntrhub]

There is a tap screw next to the oil filter housing. Remove that and install an oil pressure gauge to it. This will give you an accurate reading of oil pressure. You may have an oil sending unit going out, or a dash oil gauge at fault? The only way to tell is to get that oil pressure gauge hooked up and light off the car. Pressure would read within seconds.
You say there was no oil level change checking your oil. If you remember how the oil came out the drain hole, it should have emptied out like syrup. If it came out like flowing water, then yes, you did have fuel contamination. And the oil would have smelled very strong like fuel. You may want to take the old oil filter and dissect it to check the paper pleats? This could tell you if the crank babbits have scored and the crank is about to spin, or has spun a bearing.

 

[Stingray74CC]

I wish I hadn't already gotten rid of the oil filter or I could check that out. I looks like I'll be getting a oil pressure gauge and checking out the pressure situation. I don't have enough experience to trust myself to go into the oil pan and start looking for bad rod bearings. I have a feeling that that's what happened. It did start to turn over and stop while I still have the ignition on. The engine even sprung back a little due to the compressed air.

Anyone know a good mechanic in Charleston, SC area? I just moved here two months ago from Annapolis, MD. (Guess I should change the info under my name.) Or is this something that I can do. I have some mechanical ability.

Wow, I'm kind of scared now.

Thanks for the help. I'm going to get on this as soon as possible but I have no time to work except for the weekends so this is going to be a long process.

Anthony