Valve clatter under acceleration

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tkelley72

Well-known member
Joined
Feb 1, 2013
Messages
78
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Location
United States
My Car
72 mustang convertible
After having carb, issues for months, I finally got it rebuilt and installed. It's a Holley 600 . I have both float bowls set to the bottom of the threads at the sight screw, set the air and fuel mixture with a vacuum gage to the highest vacuum. (about 19.) If I try to lean it out the idle quality goes away and it stumbles and tries to die. It may be a little on the rich side based on the smell. The drivability is good but now I have valve clatter when accelerating. What adjustments can I make to resolve this issue. Never had this problem prior to the carb. rebuild. There are a few items of note I need to put out there for your consideration. First, the car sat for several months and had about 5 gal. of gas in the tank from last year. It did have Sta-Bil in it and I added about 5 gal. of fresh fuel to it. I haven't checked the plugs yet but I suspect they need to be replaced since the carb. had been in such bad shape and sort of dumping fuel. I can smell gas in the oil so I know it needs to be changed. I probably have the worst of all situations going on here but is there a step by step process I should take? Is it a timing issue, air/fuel mixture issue, plug issue, bad gas issue or all of the above? I didn't want to move forward with oil and plugs only to foul them up before resolving the prime issue/issues. Thanks for your help guys!
 
I'm not really sure how to answer that question. The noise is faint, not a loud clatter if that helps?
 
If I adjust the timing do I advance or retard it? The engine is a later model 302 HO based on the firing order. Which direction is advance and retard? I don't have a timing light so I'll be doing it by ear. Obviously I'm a novice at this. Thanks
 
Ruh roh. No good can come from this.
You need to be able to quantify things before you go tweeking and adjusting.
 
Lean condition, too much ignition advance, or both. Back your timing off to 17" vacuum and see if that helps reduce the pinging. Do a Google search on using a vacuum gauge to adjusting ignition timing for plenty of how-to's.
 
Tool purchase time! Get a timing light, I don’t know which ones to suggest these days. I have an old Ferret timing light, which I think are now sold under the MSD name. A timing light with a degree display and advance / retard capability will make it easier as you can use the TDC mark on your balancer.

Might check thrift stores first.
 
If the oil is diluted, change it. Inspect your spark plugs, replace if needed. Get a timing light or rent one from your local parts store.
I would guess you have too much ignition advance. If you have vacuum advance, disconnect it and see if the noise goes away. If you have too much initial advance, it may be hard to start when engine is hot. Without knowing anything about your engine, I would start with 10 degrees initial advance.
 
All I know about the engine is that it is a rebuilt later model 302 based on firing order so I'm assuming it's been bored out .030? ( was done prior to my ownership) Other than that it is stock with Pertronix 1 ignition module.
 
What concerns me most is you smelling fuel in the oil.

cjstaci is right, change oil and filter. be surre to use an oil with Zinc aas it is needed for the cam lobes and lifters. Modern engines use roller lifter and no longer use Zinc, which is no longer blended into most engine oils as the Zinc foul catalytic converters. I use AmsOil Z-Rod synthetic 10/30. They offer higher weight Z-Rod also, like 10/40, 20/50, if you need higher viscosity oil.​


As for the fuel smell, the way gasoline gets into oil is a short list. The way I usually see it happening is when the fuel pump diaphragm begins to leak. Sometimes a leaking fuel pump dump liquid gasoline on the ground and is easy to see and diagnose. Other timess the liquid gasoline ends up running into the crankcase, leading to oil contamination that is too thin to properly lubricate internal parts. Other times a fuel pump leaks to both areas. If you smelled gasoline in the oil I would not take chances on inadequate lubrication and protection for the engine.

While doing the fuel pump R&R you may as well replace all fuel lines at the tank and pump, as well as at the carb along with the fuel filter. I have some YouTube videos showing how to replace the fuel pump and fuel lines.


https://youtu.be/frYaO_u0OZc

https://youtu.be/BmQpNEHPgaw

https://youtu.be/Xp8vLVlxtVk

https://youtu.be/lkKVcliOd2w
 
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What concerns me most is you smelling fuel in the oil.

cjstaci is right, change oil and filter. be surre to use an oil with Zinc aas it is needed for the cam lobes and lifters. Modern engines use roller lifter and no longer use Zinc, which is no longer blended into most engine oils as the Zinc foul catalytic converters. I use AmsOil Z-Rod synthetic 10/30. They offer higher weight Z-Rod also, like 10/40, 20/50, if you need higher viscosity oil.​

He said its a late model 302, and it has the 351 firing order. It could already be a roller motor. I wanna say they changed around 88-89 in the broncos and F150s.

If OP isn't sure, there are a few different thinks to check that may help answer that.
 
An old mechanic's trick, ( and I fall into that category of "old mechanic"), is to pour a quart of automatic trans fluid into the engine oil. This works to clean away varnish that may be causing your lifters to stick. Sometimes, along with ATF in the engine oil, you can take the air cleaner assembly off, rev up the engine, and trickle some ATF into the carb to coat the valve stems to loosen varnish there. In all fairness, a product like Marvel Mystery Oil will work as well. Times two, along with Mrgmhale, is replacing your fuel pump, if you smell gasoline in the oil. You'd think this event would help to remove any varnish as well, and it may be doing so, still, I am in total accord in replacing the fuel pump. Years back, when I was a mechanic at a Mustang shop , I was checking out a customer's 351C car that had a tune-up issue, just idled funny. Of the things checked, was valve lash and rockers. The car seemed to run fine, but the minute I plugged the PCV valve and hose back into the rocker cover, it ran funny. I took a whiff of the oil vapors coming from the breather and there it was.....gas smell in the oil. So much so, that it was getting sucked into the engine making the car run as if it were too rich I changed out the fuel pump and problem solved. It happens. Obviously, should this be happening with your engine, you WILL need to change the oil and filter out afterwards . If I remember correctly, installation is easier when you roll the engine over to #1 TDC on the harmonic balancer, as the pump eccentric is rotated furthest away from pump arm engagement.
 
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