292 Questions

[Mike_The_Grad]

Wow, that video helps for sure. Something is definitely amiss with your setup. Steeveedee is on to something. I've not seen a steady rise in intake vacuum as the throttle is opened like yours does. Then immediately drop to zero like that. Read up some more on vacuum gauge reading. There's something to explain the sudden drop like that. Also sounds like you got a knock or something that is rpm related. I could be wrong and just hearing things. Either way, I'd start at the exhaust manifold and work your way back to the end of the tail pipe. But the heat riser valve is probably gonna be the culprit. Do you have it connected properly? I couldn't tell you what it's supposed to look like or how it functions. Never had one and I just put headers on my dads 292. My guess is that its malfunctioning or inoperable. Especially because you say that youve let the engine warm up and it still reacts the same regardless.

[May70]

Originally Posted by Mike_The_Grad

Wow, that video helps for sure. Something is definitely amiss with your setup. Steeveedee is on to something. I've not seen a steady rise in intake vacuum as the throttle is opened like yours does. Then immediately drop to zero like that. Read up some more on vacuum gauge reading. There's something to explain the sudden drop like that. Also sounds like you got a knock or something that is rpm related. I could be wrong and just hearing things. Either way, I'd start at the exhaust manifold and work your way back to the end of the tail pipe. But the heat riser valve is probably gonna be the culprit. Do you have it connected properly? I couldn't tell you what it's supposed to look like or how it functions. Never had one and I just put headers on my dads 292. My guess is that its malfunctioning or inoperable. Especially because you say that youve let the engine warm up and it still reacts the same regardless.

Are you talking about this? Its got one of the heat release springs on it and its not stuck. The exhaust manifold I just bought a few months ago. With the engine about warm its still in the same place though. I held it open all the way (i guess) and gave it gas, no change.

I dropped the exhaust and cut off the muffler, then I put the pipe back on it just so I wouldn't get smoked out. Muffler looks fine inside. Definitely not the problem. I made another video just to show its the same exact thing. No difference that i see.

https://youtu.be/mRvxsyky7pg

That sound that was mentioned is definitely there. Not sure if thats considered a knock or what but when I first brought it home didnt notice it.

[Steeveedee]

OK, so I'm not clear on the process. Did you run it at all with the pipe disconnected from the exhaust manifold?

[May70]

Yes its off at the exhaust manifold right now and just did the same thing. I even put a scope through the straight pipe with it off, its clear.

[RichardJ]

Your previous question about the condition of the points condenser can be best answered visually. If metal is being transferred from one point contact to the other, the condenser value is incorrect. Don't confuse normal pitting wear with metal transfer. Normal pitting can be cleaned up with a small point file.

[May70]

Originally Posted by RichardJ

Your previous question about the condition of the points condenser can be best answered visually. If metal is being transferred from one point contact to the other, the condenser value is incorrect. Don't confuse normal pitting wear with metal transfer. Normal pitting can be cleaned up with a small point file.

The points are brand new. I gaped n new points so they shouldn't be rough like in the picture. My dwell is dead on 31. My post about wanting to test the condenser was just to make sure it was operating as it should. I did not have a multimeter that had a setting for microfarads so I did not give a value for the condenser reading (the only values I gave were for the ignition coil?). Im confused

[RichardJ]

>> My post about wanting to test the condenser was just to make sure it was operating as it should.<<

The condition of the point contacts will tell you if it is operating properly.

>> I did not have a multimeter that had a setting for microfarads so I did not give a value for the condenser reading <<

The condition of the point contacts will tell you if the condenser value is correct.

If you post again that you don't have a capacitance meter, I'll repost the same information in English next time.

If you tossed the old points, take a look at the new ones to see if anything is beginning to look abnormal.

I'll try one more thing. In lieu of a Capacitance Meter, the condition of the point contacts will tell you everything you need to know about condenser. End of story, move on.

On your video, were you connected to a vacuum port that you are positive has full manifold vacuum at all times?

Reconnect the dwell meter and the vacuum gauge and repeat your video test. You need to look and verify that the dwell stays consistent and steady at or near the 31* you reported.

[Steeveedee]

Thinking more about this, what do the wire running to the points and the breaker plate to ground wire look like? Check the ends especially to see if there are a bunch of broken filaments. It could be that there are enough for idle and a bit of speed, but not enough to carry current when the engine is under load. I don't think that this was mentioned before. The breaker plate ground wire flexes as the vacuum advance moves, so it can eventually wear out.

[May70]

Originally Posted by RichardJ

>> My post about wanting to test the condenser was just to make sure it was operating as it should.<<

The condition of the point contacts will tell you if it is operating properly.

>> I did not have a multimeter that had a setting for microfarads so I did not give a value for the condenser reading <<

The condition of the point contacts will tell you if the condenser value is correct.

If you post again that you don't have a capacitance meter, I'll repost the same information in English next time.

If you tossed the old points, take a look at the new ones to see if anything is beginning to look abnormal.

I'll try one more thing. In lieu of a Capacitance Meter, the condition of the point contacts will tell you everything you need to know about condenser. End of story, move on.

On your video, were you connected to a vacuum port that you are positive has full manifold vacuum at all times?

Reconnect the dwell meter and the vacuum gauge and repeat your video test. You need to look and verify that the dwell stays consistent and steady at or near the 31* you reported.

Thanks for clearing that up RichardJ, keep your patience with me!! I think ive mentioned, I have little to no experience in this stuff. Learning as I go. Unfortunately my family/friends who knew this stuff are dead, so I basically have this forum and google. I appreciate you spelling it out, I wasn't tracking that one.

I got the drift now of what you meant and will check those points you made out in the morning.

I am going to try and find a carb from a friend to swap on there and see if that changes anything. I am looking for something to change the symptoms and go from there.

Stevee Ill take a picture of my distributor internals in the AM. Thanks gents....

[Steeveedee]

Originally Posted by May70

Thanks for clearing that up RichardJ, keep your patience with me!! I think ive mentioned, I have little to no experience in this stuff. Learning as I go. Unfortunately my family/friends who knew this stuff are dead, so I basically have this forum and google. I appreciate you spelling it out, I wasn't tracking that one.

I got the drift now of what you meant and will check those points you made out in the morning.

I am going to try and find a carb from a friend to swap on there and see if that changes anything. I am looking for something to change the symptoms and go from there.

Stevee Ill take a picture of my distributor internals in the AM. Thanks gents....

I'm not sure that a picture will work, unless you have way better skills with a camera than I have (which wouldn't be all that much- my camera skills are pretty much non-existent). It's going to rely on you wiggling the wires to see if a lot of the strands are broken. This is just another check, and hopefully it's an answer. But not being in front of it, it's just hopeful that we finally guess a solution over the internet. By the time this is figured out, you'll be an ace on troubleshooting these old trucks. It's pretty much how we all learned it, back in the day. But we didn't have the internet then. Did you download the Factory Service Manual for your truck? Not that it would necessarily help, at this point. Those manuals discuss problems back when the vehicles were new, and didn't have corroded and/or worn wiring and serious age on them.

On the topic of checking the condenser, that takes a type of equipment called a "Decade Box", and isn't something that a mechanic would normally use in the repair business. In 25 years of working on vehicles, I never used one- it is for the electronics guys, and I'll bet if you went into a repair shop today, you'd never find one. The dwell-tachs don't have it for this reason.

"Fun" story about condensers- one of my friends put a bunch of Mallory tune-up parts in his '62 Corvette. A few days later, it rolled to a stop. He couldn't figure it out, did a valve job and all kinds of stuff. It still wouldn't start. In the process of pulling the distributor cap off and checking the points for about the 10th time (because there was no spark- the original problem, btw), he managed to pull the wire out of the condenser by accident! All that unnecessary expense and time for a failed condenser. We just looked at it like, WTH? a brand new part! He went on to be a really good mechanic, and did it for a living for 40+ years.

[May70]

The guy I talked to only has 4 barrels so that idea seems to be gone. Didnt get a chance to look at the truck today, bad weather here. Talked to another guy today and he was scratching his head on the subject and he did fleet maintenance back in the day on a lot of 292s.

[May70]

How about some inputs on this.... Maybe years of experience and what ive got here might light a bulb for someone.

I did some searching for more info on using vacuum to diagnose issues. Everything I have read only lists one reason for vac going to zero. But the vacuum shows some fluctuation before dropping toward zero which got me thinking.... I know the exhaust is not blocked so maybe that initial fluctuation means something...

Looking at the second video I posted ( Post #163) with the muffler off ( I got the same readings with exhaust off at the manifold); It holds a relatively steady 22 at idle. There is no fluctuation until accelerating, when it decreases to 20 then increases to 23 after that point it drops off to zero. I see two distinct patterns first a fluctuation off idle from 20-23, then with continued acceleration a drop off towards zero while noting the engine sounding like its dying off. With that in mind, I found this article out of a pop mechanic magazine which gives the best guide ive been able to find.

Looking at Case #5 in the picture from pop mechanics: Normal and steady reading at idle, but vibrating reading at high speed - weak valve springs. Does this explain the first pattern of fluctuation between 20-23?

I found another guide on another forum that indicated similar (second pic).

Could it be possible that an extreme case of the valve springs being weak cause essentially a complete loss of power/vac with acceleration? If the engine is dying out, wouldn't that cause the vac to go to zero as a result?

Also looking at #1 and #2 on the pop mechanic article, to me that is saying I do not have an issue with either my carb settings at idle or the wrong timing. Is that a leap too far?

[RichardJ]

"68gmsee" posted these two pictures years ago. I labeled them and I hope I didn't screw up. I've had tube headers on my truck for twenty years.

[Steeveedee]

Last straw to grasp. High vacuum like that could be from flat(ish) cam lobes because the valves aren't open for a long time. Maybe that's part of the lifter noise. This would be related to the cam going flat over the last few months, which you indicated that the performance got worse over time. What kind of measuring equipment do you have? Maybe take the valve cover off and measure the stroke of the push rods by cranking the engine by hand to see what the lift is for a few of them. Other than that, we've pretty much covered all the possibilities.

I have seen where cams with flat(ish) lobes really cut into a vehicle's performance.

Anyone out there know what the lift is for a stock cam in a 292? He'll need something to compare his lift against.

[VWNate1]

Fascinating read here .

Subscribed to find out the end cause .

[Steeveedee]

Originally Posted by VWNate1

Fascinating read here .

Subscribed to find out the end cause .

It's a stumper, for sure.

[VWNate1]

I've been an i6 engine lover since the early 1960's and I wish this one wasn't so far away .

I've been able to make clapped out InLine engines with 60# compression run very well .

This one clearly has some internal issues but, judging by the spark plugs it's running way too rich, apart from the oil wetted # 2 one .

There's a bit of art to tuning the InLine engine, I think perhaps he still has some sort of vacuum leak .

[May70]

Ok so going back to my post #174.... I did a few things but one issue I noted was after checking the mechanical advance by turning the shaft/rotor (engine off) the shaft did seem to spring back into place. However the timing was advanced more that what it was set to at idle when I started it back up afterwards. That should NOT happen correct? Me manipulating the mechanical advance to check it should not have changed the initial timing I set prior?

I can try doing that again to see if it changes the timing again. If so perhaps the distributor mechanicals are messed up or the springs are warn out (something like that)?

[geezer#99]

I had a points dizzy once that produced changing timing like that.
Found the points plate that the points and condenser are attached to could flex upwards which would change the dwell and timing.
Easy test is to lift upwards on the condenser. The points plate shouldn’t move upwards.
Mind you, this was back 40 years ago so my memory is a bit fuzzy!

[May70]

Originally Posted by geezer#99

I had a points dizzy once that produced changing timing like that.
Found the points plate that the points and condenser are attached to could flex upwards which would change the dwell and timing.
Easy test is to lift upwards on the condenser. The points plate shouldn’t move upwards.
Mind you, this was back 40 years ago so my memory is a bit fuzzy!

So I just went out and tried it. I could lift the plate straight up like a quarter inch. I made a crummy little video of a series of blabbling with what Ive done/whats going on so excuse the garbage quality I dont know how to do the youtube thing. Youll probably have to pause the video to read the text because for some reason it flips really fast. The first part of it shows me looking at dizzy.

https://youtu.be/Zf4fD4nMNiA

Lifting that plate changed my dwell because before it was 31 and afterwards it was 29. Tell me if this was what you meant.

I said in the video that my timing didnt change but now im confused because it should have changed more than what it did. It may have increased the timing 1 or 2 degrees. If every degree of dwell is three degrees of advance it should have been way higher. Keeping in mind the engine wasn't quiet warmed up all the way. Thoughts?

[geezer#99]

IIRC you shouldn’t be able to move the point plate much at all. But like I said it’s been many years since I had that problem.
Maybe someone else knows for sure.
Have you tried ignoring your tach and timing numbers and just advance your distributor to see how the motor runs.
Just loosen the dizzy enough that it will move with a bit of effort.
If the rpm increases be sure to control it with the idle screw.

Have you had the point plate out to inspect the weights and springs?

[May70]

Originally Posted by geezer#99

IIRC you shouldn’t be able to move the point plate much at all. But like I said it’s been many years since I had that problem.
Maybe someone else knows for sure.
Have you tried ignoring your tach and timing numbers and just advance your distributor to see how the motor runs.
Just loosen the dizzy enough that it will move with a bit of effort.
If the rpm increases be sure to control it with the idle screw.

Have you had the point plate out to inspect the weights and springs?

Ive adjusted it a few times just by hearing but I dont think ive put it much farther than 10-12. Yesterday when i messed with the distributor and it jacked the advance up to like 16* after it was almost sounding as if it were missing and the idle was super high. I can try it again though.

No I have not had the plate out.

[geezer#99]

Just plug the vac advance off when you test.

[VWNate1]

O.K., the deal is :

You set the points using the dwell meter then rev. the engine, the dwell *must*not* change more than a degree or two .

The breaker plate is allowed to move up and down a tiny bit and it's possible to not have it properly set in place .

Once you have the 31 ~ 33 degrees dwell, attach the vacuum gauge to the open manifold port on the leading outside edge of the carby, start the engine and allow it to idle 600 ~ 800RPM, slowly move the dizzy _NOT_ touching the vacuum can, watching the vacuum gauge ~ the needle will rise and eventually will begin to flicker like it did in one of your videos ~ what you want is the highest steady vacuum reading .

Once you have that, tighten the dizzy's pinch clamp (don't go crazy here, use a stubby box end wrench and DON'T FOOL WITH IT AGAIN .

Now, put a tight fitting cap over that vacuum port and connect the vacuum gauge to the dizzy's advance pie using a 'T' fitting, goose the throttle, the *instant* you open the throttle you *must* get a vacuum signal to the dizzy or you'l et stumbles & flat spots .

I assume you've replaced the leaky vacuum advance can ? .

If not, STOP until that's fixed then go back and laboriously do every step in the proper order :

Set dwell .

Set timing, either to 10* BTDC or using the vacuum gauge, the vacuum gauges more accurate because it compensates for your engine's wear, altitude, low quality gasoline and so on .

Once all this is done you can adjust the idle speed then the mixture then the final idle speed .

If the carby is still dripping fuel, there's a serious problem ,most o the time it's the float is too high because you touched the floats as you assembled the top of the carby to the bowl .

Use the printed cardboard float gauge supplied in the kit .

These Rochester MonoJet carbies are the last, final and very best iteration of the 'B' series that began in the 1940's .

That compensating valve do - hicky under the sheet metal plate ? don't worry about it, stick shft engines don't normally have it .

If you think the ignition coil is bad, try to afford the correct DELCO HEI one, there are two versions, one has a separate coil, AC / DELCO sells rebuilts or a junkyard one will do .

If you're strapped, buy an EPOXY FILLED coil from NAPA or other high end place, when I sold 'standard blue streak' ignition parts the coils were often bad right out of the box or failed in a week or two .

Accel coils are outstanding if $pendy and FUGLY because they're eye searing yellow .

[straight6chevyguy]

First off, good video! I was able to follow pretty easily and the picture quality was not bad at all (Some peoples videos you can hardly see what your looking at)

I think It's still a vacuum leak but I don't know for sure. I would consider getting a different carb.
Not to many more things that could be the problem since you have almost replaced all the common problems.

The only things left are maybe replace the carb and then start looking internally starting with the valves.

I do here the noise you are talking about. My 292 has something pretty similar but not as loud.