In a previous post my car was running rough i installed new distributor, spark plugs and wires and had a friend of mine come and set it up right since it was not timed right and would not turn over. That was done but now when I go on the freeway I press on the gas and it seems as if the car doesn't have enough power to really speed up and when I let off the throttle it backfires didn't do this before and when I first start it up it sounds like the starter is grinding after that it starts up fine. My friend said he doesn't use a timming light he goes off just by ear and how the car revs and idles. Can this be what is causing this . I read its good to set it 10-12 degrees advanced for better performance. Car is a 1984 monte carlo ss stock 305 .
Car backfiring
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Sounds like the timing needs to be more advanced. I'd get a light and see where the base line timing is at. Make sure your advance on the distributor is hooked up.
I fully understand what your friend is saying, because it is possible to do that, but on a 30-plus year old engine that's actually not the best way to go about it.
It sounds like you have two issues. First is where did you get the distributor and did you get the distributor with the vacuum advance unit or are you still using the one hooked to the ECU?
Many of the new Distributors being sold today are sub standard as quality control is not where it used to be. You will find that most of the reluctor wheels are off center and they rotate inconsistent, and this gives you an inconsistent spark.
With the vacuum unhooked and for an engine of 1984, 12 to 14 degrees before top dead center is the proper setting for your Baseline timing. Then from there you go to your full advance by use of your vacuum advance and your mechanical advance.
If you're only backfiring when you let off the throttle especially after your deep into it, most likely that's your diverter valve coming from your air injection system and that's a common problem with GMs. Or you are running too rich.
Another question is when was the last time the timing chain was changed? Also..., depending on the year, 83 to 86 had soft cams. While at the same time, today's motor oil no longer has the ZDDP zinc in the oil. When you run a flat tappet cam today you need to add the ZDDP additive or you will wear down the lobes of the cam and this is going to cause all kinds of problems.
One of the other reasons you use a timing light is not just so you see the timing mark you want to look at bounce.
With the engine at idle you want to make sure the timing mark is consistent and not bouncing all over the place. Then with the timing light attached you want to increase engine speed to about 1500 and watch where the timing mark is landing and making sure it's consistent and not bouncing all over the place.
Then you want to stab the gas and again Watch where the timing mark is landing and again is it consistent and not bouncing around?
If you're not going to use a timing light, then the correct method is to use a vacuum gauge.
Once you get your Baseline vacuum, you move the distributor. You listen to where the engine is running the best and you listen for pitch.
On the GM 305 the rotor turns clockwise, so counterclockwise is advanced and clockwise is retard. After you set your baseline (curb) idle screw at roughly 800 RPM move the distributor clockwise and watch the vacuum gauge and note if the engine slows down or if it picks up speed. Then when you move the distributor counterclockwise and what you will notice is that the vacuum will pick up or drop.
You want to get your vacuum at your base idle setting to the highest value possible and then you back off the distributor about an eighth of an inch. Then tighten down (snug) the bolt, get the engine to operating temperature and then shut it down. Wait about 10 minutes so you know the engine's good and hot and hit it with a key do not give it any gas it should pop.
Basically what you are checking is to see if your timing and air fuel ratio is correct. On a properly tuned engine that is at operating temperature once you hit the key it should instantly start.
You will hear the pop and it will instantly start. Each car is different so you have to know your own car so you might have to stab the gas a couple pumps but when you hit the key it should start. If it drags and is hard to start, then you are too far advanced, and or too lean.
If you have to crank it like starting a cold engine then you have something wrong.
The typical 1984 305 (1980 - 1986) was a low compression engine, and it was also set up to run lean burn. The factory set it with a higher idle and some of these cars ran so bad that the factory had a switch that would turn the AC on when you shut off the engine. They did this so the engine wouldn't run on.
On the earlier engines before catalytic converters when we ran lead in the gas you could easily from the factory have 10 or 11 to 1 compression without any issues at all and as you look at the old books you'll find out that most of these engines started either at zero or two or four degrees before top dead center for base timing they also had lower idle speeds for the idle setting.
Once the engines went to unleaded fuel they had to drop compression because detonation was a problem the way they got around this was by kicking up the idle once it started which is why you had the electric solenoids and the vacuum dash pots to keep the idle up. The factory only wanted to sell cars. So running unleaded fuel basically meant they had cars that didn't run and that won't sell cars. So they dropped lift and duration on the cams so they idle smooth to get it off of the dealer showroom.
Because they had to add EGR and a catalytic converter and remove lead from fuel all of that stuff was still being worked out, and back then the engines were a mess because of it.
So basically you have a 1984 that is not set up correctly, check your timing, check your base timing, double check your firing order, take the timing light and put it on different spark plugs wires and make sure your ignition is consistent. And also use a vacuum gauge.
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I got a timing light and when I used at zero the timing was sett to zero on the timing tab. I lossened the distributor and set it to 10 degrees btdc and ran all better. I got a little back fire letting of the gas when smashing the gas. I sett it to 8 degrees and gonna see if that makes it better .
Whats the best area to set it to . Could advancing it cause this back firing im getting . I think I might need to mess with the idle screw she runs good though.
The good thing is ... You have an actual timing tab to work with. Some small blocks of that era only had the probe hookups.
Like said... Start 12 to 14 BTDC, distributor vac unhooked.
This is figured on idle 700 - 800.
You have 305 HO, 9.5:1 Compression Ratio, above 14 can start causing problems.
It's easier to explain when building an engine using a degree wheel and the heads off. This way you can actually see where the piston is at the point it gets a spark.
With the head off you clearly see the difference between 12 BTDC or At TDC. When you provide spark prior to TDC the flame front starts and the piston pushes it up to the head as the piston is moving up. While at the same time the flame front and it's expanding gasses wants to push the piston down. With a 9.5:1 Compression Ratio, 14 would be the highest you would want to go.
Other Q's... When/where is it backfiring? Intake or exhaust?
Have you checked and verified your firing order?
Where is number one wire on the cap?
Does your carb still have the factory caps, or are the fuel mixture screws available?
What is the lowest tachometer setting you can idle and not die?
What is your base vacuum at idle?
From idle and engine warm, in drive and foot on brake.... Stab the gas. Does it bog or backfire through carb or exhaust?
Like said... Start 12 to 14 BTDC, distributor vac unhooked.
This is figured on idle 700 - 800.
You have 305 HO, 9.5:1 Compression Ratio, above 14 can start causing problems.
It's easier to explain when building an engine using a degree wheel and the heads off. This way you can actually see where the piston is at the point it gets a spark.
With the head off you clearly see the difference between 12 BTDC or At TDC. When you provide spark prior to TDC the flame front starts and the piston pushes it up to the head as the piston is moving up. While at the same time the flame front and it's expanding gasses wants to push the piston down. With a 9.5:1 Compression Ratio, 14 would be the highest you would want to go.
Other Q's... When/where is it backfiring? Intake or exhaust?
Have you checked and verified your firing order?
Where is number one wire on the cap?
Does your carb still have the factory caps, or are the fuel mixture screws available?
What is the lowest tachometer setting you can idle and not die?
What is your base vacuum at idle?
From idle and engine warm, in drive and foot on brake.... Stab the gas. Does it bog or backfire through carb or exhaust?
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I just ran into another problem I was driving my car on the street and then it just turned off . I was able to turn into a street were I tried starting it back up it sounded like the battery was low so I asked for a jump from someone but it still didn't start it would just crank. Im not getting any spark when grounding a spark plug how will I know if the distributor is done I just got it like a week ago . I am getting power to the distributor when testing the pink wire going to it .
The attached is a good basic trouble shoot of the pickup coil.
Typically when HEI quits like you experienced, it's the pickup coil. I had to check memory as a good ohm value should be around 800. He has spec as being between 500 to 1500 ohms, but what he tests it's about 812.
If you have Oreilly or AutoZone close to you, you can have module tested.
If this was China made distributor, I 've had trouble with the connectors coming off the wires, which means no spark. I've also had trouble with the shaft not being centered and this causes the rotor to spin in the reluctor wheel elliptically instead of just rotating on axis as it should.
Basically pull the cap and inspect the pick up coil, it's wires and the connector. Put VOM probe across terminals and you should be around 800 ohms.
Typically when HEI quits like you experienced, it's the pickup coil. I had to check memory as a good ohm value should be around 800. He has spec as being between 500 to 1500 ohms, but what he tests it's about 812.
If you have Oreilly or AutoZone close to you, you can have module tested.
If this was China made distributor, I 've had trouble with the connectors coming off the wires, which means no spark. I've also had trouble with the shaft not being centered and this causes the rotor to spin in the reluctor wheel elliptically instead of just rotating on axis as it should.
Basically pull the cap and inspect the pick up coil, it's wires and the connector. Put VOM probe across terminals and you should be around 800 ohms.
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