coil, spark plug wires, or plugs

[old cool]

If a 250 inline seems a little shaky at low rpms as you let off clutch, is that normal? I have been down this road in the past, but I think its helpful to get the experienced guys to share old-school techniques every so often. I really want to rule out coil, wires, and plugs as the problem. What I want to know, is how can I check each component without gauges and meters? I don't have equipment other than vacuum gauge and timing light. (I hope this doesn't need to be three questions. )
LOL: plug check for dummies, wire check for dummies, and coil check dummies

[TJ's Chevy]

Could be a bad clutch to...does the truck itself chatter when you let the clutch out? Alot of times those old single barrel carbs will develop vacuum leaks and make the engine perform somewhat poorly...could you describe shaky a little better?

[old cool]

Come to think of it TJ, I should plug off the after market Cardone power booster and see if that has a vacuum problem which causes the chatter. The brakes are grabby if depressed quickly. However, grabby brakes has been covered on this site a lot.

Clutch seems normal though rear main is leaky. Could it be getting oil? I can drive with minimum chatter cuz im used to it. It just doesnt seem smooth enough.

If an engine had a misfire at lower r's, it feels like that too would cause chatter. Thats why i want to check the simple stuff first.

[TJ's Chevy]

Well...if you had a misfire you'd probably here it when it idles. A super easy way to tell if your carb, or intake has a vacuum leak is to pull a steep hill in 2nd gear at just above idle rpms...like 1000...if it starts to really bog down then give it more gas...if it dies when you give it more gas you have a vacuum leak no doubt..I experienced this with my 292 when I had the original 1 barrel on it....at higher rpms...like 1500 or above...it would pull a steep hill in 2nd just fine...but if I didn't wanna create alot of dust going up the hill at 20 miles and hour...then I would drop the rpms to 1000 and as I was going up the hill I could hear the vacuum leak...it simply sounds like air being sucked like normal through the carb, just louder...then POP! Engine died. Here's a video of what a vacuum leak sounds like....notice when I rev the engine it hesitates majorly sometimes.....https://www.youtube.com/watch?v=PwwA...fzpcUXyK_5-uiw

[old cool]

I don't recall the truck bogging in second gear at any road angle but Im going to give it a run just as you described. I have changed grommets, hoses, and clamps. I have taken a rubber hose a checked for hissing sounds especially at intake and carb spaces. Pretty sure no leaks. I even swapped check valve on booster. The only air leak I could detect was behind booster from inside the cab.it doesnt seem to get louder as i brake so Im guessing the air movement is within the booster.
not to overwhelm, but there are a couple things that might add to your thinking. First, the chatter or shaky feeling is most noticable on uphill angle and its only on take off. No issues in second that I recall. Secondly the carb is remanufactured but is has a gas weep around the upper and lower part of carb (float seam). Either warped or cheap gasket. the truck pulls well after chattery start. Lastly, the heat riser is frozen or tack welded vertically. But that shouldnt matter as the chatter occurs when engine is cold or warm. Ive learned to get the shake to a minimum but it doesnt seem like it should be there. You know how the cabs are when it comes to vibes. Lol. Oh yea, no miss while idling.

[old cool]

Thanks a million for video! Very helpful for learners like me.

[TJ's Chevy]

Chattering on a uphill start is cause from a worn out clutch. I've ad my truck loaded to the hilt with dirt and my truck would majorly chatter when I started to let the clutch out, in other words..as the pressure plate and disc started to grab the truck would shake and rattle...and its because the disc was worn out..so that's cause it to grab and slip, grab and slip until the clutch it all the way out...I really think your clutch is worn out, but another way to tell vacuum leaks is to spray carb cleaner around the intake ports and around the carb base...any change in rpm will tell you vacuum leak.

[old cool]

back in the day, I heard you could test a worn clutch by taking off in 2nd or 3rd gear. If the vehicle stalled your clutch was good, if the engine revved up and truck begin to crawl your clutch was worn. I have never heard my clutch slip though i wont rule it out.

I still think you are on to something regarding vacuum. I'm also wondering if it would help to advance the timing with a vacuum gauge. The feeling I get is like someone pulled a spark plug wire and then as the rpms increased, the truck smooths out. Unfortuately, this could also be carb (too much or not enough fuel as I start going). The smell from exhast makes me think unburned fuel.

The mystery for me is that the truck idles smoothly and climbs smoothly as I accelerate.

Thanks TJ.

[TJ's Chevy]

Originally Posted by old cool

back in the day, I heard you could test a worn clutch by taking off in 2nd or 3rd gear. If the vehicle stalled your clutch was good, if the engine revved up and truck begin to crawl your clutch was worn. I have never heard my clutch slip though i wont rule it out.

I still think you are on to something regarding vacuum. I'm also wondering if it would help to advance the timing with a vacuum gauge. The feeling I get is like someone pulled a spark plug wire and then as the rpms increased, the truck smooths out. Unfortuately, this could also be carb (too much or not enough fuel as I start going). The smell from exhast makes me think unburned fuel.

The mystery for me is that the truck idles smoothly and climbs smoothly as I accelerate.

Thanks TJ.

Pull a plug....if yer plug is black...yer running to rich...lean it out till the engine starts to stall then richen it till you reach maximum rpm..then richen it about a 1/4 turn after that and see how it runs....you may have to adjust yer idle again.

[old cool]

plugs have not been black since I had the distributor set correctly. when I bought the truck, I couldn't advance the timing at all. The vacuum advance was bumped against the block. I was also able to lean out the carburetor once the distributor was turned. I may be running too lean. Once the engine stumbles, I've been backing it out about one half rotation. That extra quarter turn may be what I need to do. I'll try that next chance I get. Thank you.

[old cool]

Hey TJ, while I think of it, have you found a good spark plug for these 250's? I currently have AC 45 XLS. With today's watered down gas, I thought about AC 46 XLS.
Also, do you have a Rochester Monojet Model B on your truck? That's what I have.

[geezer#99]

Interesting thoughts!!
Clutch chatter can be reduced by starting out in 2nd to initially get it rolling then back to first to minimize slippage.
Sounds like your plate is oil soaked from your rear main leak.
IMHO that's not a vacuum leak in the video. If it was it would be whistling and your rpm would be higher. Sounds more like lack of timing and poor accelerator pump.
If you can't advance your timing more because the vac pot is hanging up just lift the dizzy up and rotate the rotor back CW one tooth.
Is your vac pot working?
What's your initial timing?
Lack of timing makes you open the idle more and you idle on the power circuit. That's why it smells rich.

[TJ's Chevy]

Originally Posted by old cool

Hey TJ, while I think of it, have you found a good spark plug for these 250's? I currently have AC 45 XLS. With today's watered down gas, I thought about AC 46 XLS.
Also, do you have a Rochester Monojet Model B on your truck? That's what I have.

I'm using NGK plugs...working fine for me. I'll have to check the numbers again...I forgot to mention....What IS your timing at idle? That may have a small factor as well. I have 3 292's...one with an eledrock, on that had a model b, and one with a monojet.

[TJ's Chevy]

Originally Posted by geezer#99

Interesting thoughts!!
Clutch chatter can be reduced by starting out in 2nd to initially get it rolling then back to first to minimize slippage.
Sounds like your plate is oil soaked from your rear main leak.
IMHO that's not a vacuum leak in the video. If it was it would be whistling and your rpm would be higher. Sounds more like lack of timing and poor accelerator pump.
If you can't advance your timing more because the vac pot is hanging up just lift the dizzy up and rotate the rotor back CW one tooth.
Is your vac pot working?
What's your initial timing?
Lack of timing makes you open the idle more and you idle on the power circuit. That's why it smells rich.

That carb had a vacuum leak...It's been rebuilt 2 times...and it had a vacuum leak at the accelerator linkage.

[old cool]

TJ and Geezer. Thanks again.
1. My truck timing is about 8 btc, idle around 600 rpm. and yes, the vacuum line is plugged while checking. Geezer my distributor has been reset so now I am able to advance or retard timing.
2. I have not checked for vacuum leak where throttle enters carb. I will do that.
3. I don't know what initial timing means. probably something I can google but please feel free to send some tips.
4. I realize there are a lot of angles to go at this, but I want to repeat something before I take you guys all over the place. The shaky feeling seems to be less noticeable if Im spot-on with the accelerator and clutch release. UNLESS I'm on an incline. Then, I have to give it lots more gas. I even turned the tires so I wouldn't roll into the person behind me. lol It's like im running on 5 cylinders so I have to rev engine.
5. I have to address the spark, fuel, and timing issues, if any, for now. I do not know how to address clutch problems. Like I mentioned in one of my earlier threads, I sense a hesitation (fuel or spark) when I first take off. As if a spark plug wire were pulled off. Then is smooths out. HOPE this makes more sense.

[geezer#99]

Initial timing is what you call your timing at 8 degrees.
Bump it up to 12 to 14 and you'll see a marked improvement. Your idle will increase and you'll get to turn the idle down on the carb getting you off the power circuit.
Have you checked the operation of your vac pot. Lung power with a vac hose works to check it.
Your clutch is worn out. The flywheel has heat check marks on it and/or your pressure plate has the same. It won't get better. You need to remove the oil leaks and change out your clutch.
Are you running an HEI?

[old cool]

I'll bump the timing; easy to do. I once used a vacuum gauge to set timing. It did bring up engine idle when I set it at max vacuum. Perhaps that will help with exhaust smell as well.

I have old school distributor with petronix interior.

Back to carburetor, do you like to set mixture screw to maximum vacuum? If I'm not mistaken, last time I did that I was running a bit lean.

No one seems to have discussed coil, wires, or plugs so I'm assuming I haven't described anything that would lead to my symptoms.

Thanks for feedback.

[old cool]

Forgot to ask Geezer. If I hook vacuum hose to vacuum canister and blow into it, what will I see or hear to make sure it's working?

[geezer#99]

Vac gauge not the best way to set timing!
Use a timing light.
Set timing first, then turn down the idle and set mix screw to highest vac with a vac gauge.

[geezer#99]

Originally Posted by old cool

Forgot to ask Geezer. If I hook vacuum hose to vacuum canister and blow into it, what will I see or hear to make sure it's working?

You're sadly mistaken I'm afraid!! LOL!!
You don't blow into it, you do just the opposite. Use your lungs to pull a strong vacuum on it.
Listen for the vac pot to release when you let the vacuum go or pull the cap off and see if the point plate moves when you draw on the hose.
An extra benefit of this method is the awesome taste you'll get from the hose and vac pot. LOL!!

[old cool]

maybe I can rig up my vacuum cleaner. haha

[old cool]

HEY guys. Truck now back on road with some updates like new motor mounts, new exhaust hangers (others were extremely taunt), and rear end work. I'm moving forward but still have vibration that can be felt in steering wheel during initial revs (with clutch in and in gear or in neutral). I know my clutch and thowout bearing are on there way out cuz they can now be heard.
All that being said, I still think my remanufactured Rochester mono has a problem. I have wet gasket at top of float bowl and carboned plugs. I am trying to eliminate the simple first so I'm going to go back to your comments on accelerator pump and vacuum leak at accelerator linkage. Could you please share how to test for vacuum leak at linkage without driving. I sprayed choke cleaner at back of carb yesterday and the engine idle did not change. FWIW, I have heard a whistle like sound when highway driving from engine compartment.
As you can see, we can go on and on with these issues but I thought you may be able to again be specific on accelerator pump or vacuum leak. FYI, I have changed pcv with correct delco and all new hoses. Can't find any leaks via spray around carb or manifold. LOL, i have never ruled out coil as I have petronix and not sure the PO used a flamethower coil (usually comes with Petronix). Ok. Ill stop or else I'll start getting into other threads.
Thanks for help

[61K10]

clutch chatter can be caused by other drive train problems not just the clutch itself. I have a brand new complete clutch kit and new flywheel, and it has some chatter at times when first letting the clutch out. Only thing not rebuilt on my tk is the rear springs bushings. Could be my cheap zoom clutch kit lol.

[old cool]

Many have reported chatter and vibration problems. And, there doesnt seem to be any immediate answers. I feel vibes in steering wheel when I rev. I know my clutch system is on its way out but I cant see where that would correct what im feeling just sitting there. A mechanic ive used suggested I eliminate the tranmission mounts at belhousing and fab a rear trans mount. Point that 2 motor mounts and 2 trans mounts might make too rigid if the whole drive line isnt perfect.
I kinda think the tremor im feeling at rev only is fuel system or poss poor firing.

[old cool]

Many have reported chatter and vibration problems. And, there doesnt seem to be any immediate answers. I feel vibes in steering wheel when I rev. I know my clutch system is on its way out but I cant see where that would correct what im feeling just sitting there. A mechanic ive used suggested I eliminate the tranmission mounts at belhousing and fab a rear trans mount. Point that 2 motor mounts and 2 trans mounts might make too rigid if the whole drive line isnt perfect.
I kinda think the tremor im feeling at rev only is fuel system or poss poor firing.