Help diagnosing engine issue

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

85roktoy

85roktoy

SILVER Star
10 Year 15 Year
Joined
Apr 28, 2007
Threads
143
Messages
842
Location
Inlet Beach, FL
77 2F engine with 78k miles. Ever since I purchased this rig a few years ago it’s always had a slight spark knock type noise during acceleration under a load, not while idling or revving sitting still.

I adjusted timing and started running premium. That helped a lot and pretty much made it nonexistent. Back in Feb while driving over a long stretch at 2800-3000 RPM’s I started to hear it pinging again. It became worse and by the time I made it home it would barely run. Sounded like a misfire.

Checked compression in all cylinders. All 160ish with one being 150. Pulled valve cover and found one push rod smashed on the top as well as the rocker arm bolt toast. Obvious that was the culprit.

Ordered parts and installed today. Fired right up running like a sewing machine. Got her out on the highway under a load and I can hear the same pinging again. Not bad but it’s still there. I need to check the timing but something seems off. What could be causing this?

The PO said that he replaced the head when he owned it. Unsure why.

IMG_1952.webp


IMG_1950.webp
 
Last edited:
Adjust your valves at base timing. See if it sorts itself out. I would try to find another push rod and adjusting nut before you adjust valves
 
Last edited:
Could there be an issue with the replacement head? I’ve only ever owned a couple of F’s and a ‘73 F.5, so I don’t know if there are issues in the heads and swapping them around. When I have rebuilt engines the original heads stayed with the motors.

Edit: and please tell me you aren’t using that tasty olive oil to assemble your engine ;)
 
Compression is within specs that I just looked up. If the timing is set to the proper initial timing spec and it has the proper timing curve in the advance, timing shouldn't be an issue. I'd verify the advance curve though.

If good, I would maybe take a look at what jets are in the carb. Especially since you said higher octane eliminated it. Maybe it's a bit lean for sea level??

Does it maintain a normal coolant temp?
 
Last edited:
You can plot your timing curve with a regular timing light if your balancer or pully have degree tape or something. Other wise a dial back type timing light will work. Disconnect and plug the hose going to an advance diaphragm if you have one and check the mechanical advance curve.

I really don't know these Toyota distributors so not sure about the vacuum side of it. Whether they are adjustable or not.

Good luck, I hope you figure it out.
 
wondering which distributor you have? Pics?
 
85roktoy said:
77 2F engine with 78k miles. Ever since I purchased this rig a few years ago it’s always had a slight spark knock type noise during acceleration under a load, not while idling or revving sitting still.

I adjusted timing and started running premium. That helped a lot and pretty much made it nonexistent. Back in Feb while driving over a long stretch at 2800-3000 RPM’s I started to hear it pinging again. It became worse and by the time I made it home it would barely run. Sounded like a misfire.

Checked compression in all cylinders. All 160ish with one being 150. Pulled valve cover and found one push rod smashed on the top as well as the rocker arm bolt toast. Obvious that was the culprit.

Ordered parts and installed today. Fired right up running like a sewing machine. Got her out on the highway under a load and I can hear the same pinging again. Not bad but it’s still there. I need to check the timing but something seems off. What could be causing this?

The PO said that he replaced the head when he owned it. Unsure why.

View attachment 4113542

View attachment 4113550
Click to expand...

Was the adjuster tight? What head is on it? What's the condition of the rocker arm and rocker shaft? Valve train geometry? Slop? Doesn't Sniper show AFR on a screen or something?

So the engine has been pinging for a while and you didn't check the timing, but instead decided to check compression? What was the timing set at and what is it now? Pinging is bad, you can trash an engine if not corrected.
 
Yes; What is the timing (w/ timing light) and what does Sniper screen indicate for air fuel ratio when pinging/spark knock. Can you get it to ping under load at low RPM starting out? If you can’t readily get it to ping at low RPM “bogging it” then it may be something else.
 
85roktoy said:
DUI electronic ignition with Holley sniper
Click to expand...

that would have been good information to put in the first post lol

Check for vac leaks on manifold? or crack at the base under the sniper.... the crack is usually really fine and hard to see at times

what do you have the timing set for? some setups like timing more advanced... I am running about 15* myself

does the pinning increase when advancing the timing? or retarding?
 
Thanks for the feedback everyone. I’m a novice for something of this nature but I’m reading and learning more.

I’m fairly confident the manifold is good as it was recently all apart for powder coating. Everything was checked out.

No clue where this head came from. Yes, the sniper shows AFR. Will check. Yes, it will ping when starting out (bogging) under a load.

A mechanic friend is going to help me look at the timing soon with his light. I will report back.
 
Because I often used to time “by ear” I would generally just retard the timing at the distributor until pinging stopped. (Colorado driving from 4,500’ to 10,000’ in a trip). In your case I would retard it until it stops pinging, then take a reading, it will give you more data. Hopefully friend w/ light has messed with timing a bunch and can help.
 
Mechanical wear on one part makes me think it is a mechanical issue. If you had a sticking lifter, the extra force would mushroom a rod and rocker tip. If the problem doesn’t appear cold, it seems like you have a decent chance of fishing that lifter out with a magnet while it’s cold and replacing it.

I had a problem at the other end, once. Sticking valve. That left a gap when the cam lobe dropped, and the pushrod just came out from underneath the rocker tip. Bent the rod…several times. I was almost 500 miles from home when it happened, and it required some creativity to get the truck home.
 
65swb45 said:
Mechanical wear on one part makes me think it is a mechanical issue. If you had a sticking lifter, the extra force would mushroom a rod and rocker tip. If the problem doesn’t appear cold, it seems like you have a decent chance of fishing that lifter out with a magnet while it’s cold and replacing it.

I had a problem at the other end, once. Sticking valve. That left a gap when the cam lobe dropped, and the pushrod just came out from underneath the rocker tip. Bent the rod…several times. I was almost 500 miles from home when it happened, and it required some creativity to get the truck home.
Click to expand...
Since I just replaced the push rod and rocker arm bolt how can I determine if there’s an issue with that one specific part? Routinely pull the valve cover and check it?
 
85roktoy said:
Since I just replaced the push rod and rocker arm bolt how can I determine if there’s an issue with that one specific part? Routinely pull the valve cover and check it?
Click to expand...
You will have to take the side cover off to fish the lifter out.
 
You must log in or register to reply here.

Share this page

Back
Top Bottom