Fixing my neighbors 1970 Chevelle SS - Need some advice.
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Fixing my neighbors 1970 Chevelle SS - Need some advice.
Hey guys this is my neighbors 1970 396 Chevelle SS and I am trying to get it running better. I've never worked on older american cars like this but they are really simple and I am learning quickly.
Symptoms/problems:
Very little power, runs very rich. Black smoke coming from exhaust when revved or accelerating. Left exhaust has very little exhaust flow and right side exhaust seems like a leaf-blower in comparison!
What I've done so far:
- Replaced spark plugs with new ones. Old spark plugs had so much carbon on them it was rediculous.
-Installed new edelbrock carburetor (the one in there was too big for it)
- Attempted to time the distributor better.
- Put lucas total tune-up cleaner in gas to hopefully clear carbon crap out.
I let my dad time the distributor since he's done it before and he noticed something wierd about it. He said that he had to turn it a lot farther than normal to see any effect on how the engine ran. Instead of moving it 2 or 3 degrees to see a difference it was more like 6-8 degrees. We used a light gun (not sure of the porper name) and the needle was way off to start with and he thinks the distributor was installed wrong in the first place. We were trying to adjust it to where it would start pining and then turn it down a few degrees but never got that far.
The distributor was replaced by the previous owner with a unilite electronic distributor.
After timing the distributor there definitely is more power but not anywhere near what it should be!
Can anybody give a suggestion on what is wrong? I wish somebody who knew these engines really well could help us!
Any help is greatly appreciated
Here's a pic!
Symptoms/problems:
Very little power, runs very rich. Black smoke coming from exhaust when revved or accelerating. Left exhaust has very little exhaust flow and right side exhaust seems like a leaf-blower in comparison!
What I've done so far:
- Replaced spark plugs with new ones. Old spark plugs had so much carbon on them it was rediculous.
-Installed new edelbrock carburetor (the one in there was too big for it)
- Attempted to time the distributor better.
- Put lucas total tune-up cleaner in gas to hopefully clear carbon crap out.
I let my dad time the distributor since he's done it before and he noticed something wierd about it. He said that he had to turn it a lot farther than normal to see any effect on how the engine ran. Instead of moving it 2 or 3 degrees to see a difference it was more like 6-8 degrees. We used a light gun (not sure of the porper name) and the needle was way off to start with and he thinks the distributor was installed wrong in the first place. We were trying to adjust it to where it would start pining and then turn it down a few degrees but never got that far.
The distributor was replaced by the previous owner with a unilite electronic distributor.
After timing the distributor there definitely is more power but not anywhere near what it should be!
Can anybody give a suggestion on what is wrong? I wish somebody who knew these engines really well could help us!
Any help is greatly appreciated
Here's a pic!
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Originally Posted by Silverstreak328
Hey guys this is my neighbors 1970 396 Chevelle SS and I am trying to get it running better. I've never worked on older american cars like this but they are really simple and I am learning quickly.
Symptoms/problems:
Very little power, runs very rich. Black smoke coming from exhaust when revved or accelerating. Left exhaust has very little exhaust flow and right side exhaust seems like a leaf-blower in comparison!
What I've done so far:
- Replaced spark plugs with new ones. Old spark plugs had so much carbon on them it was rediculous.
-Installed new edelbrock carburetor (the one in there was too big for it)
- Attempted to time the distributor better.
- Put lucas total tune-up cleaner in gas to hopefully clear carbon crap out.
I let my dad time the distributor since he's done it before and he noticed something wierd about it. He said that he had to turn it a lot farther than normal to see any effect on how the engine ran. Instead of moving it 2 or 3 degrees to see a difference it was more like 6-8 degrees. We used a light gun (not sure of the porper name) and the needle was way off to start with and he thinks the distributor was installed wrong in the first place. We were trying to adjust it to where it would start pining and then turn it down a few degrees but never got that far.
The distributor was replaced by the previous owner with a unilite electronic distributor.
After timing the distributor there definitely is more power but not anywhere near what it should be!
Can anybody give a suggestion on what is wrong? I wish somebody who knew these engines really well could help us!
Any help is greatly appreciated
Symptoms/problems:
Very little power, runs very rich. Black smoke coming from exhaust when revved or accelerating. Left exhaust has very little exhaust flow and right side exhaust seems like a leaf-blower in comparison!
What I've done so far:
- Replaced spark plugs with new ones. Old spark plugs had so much carbon on them it was rediculous.
-Installed new edelbrock carburetor (the one in there was too big for it)
- Attempted to time the distributor better.
- Put lucas total tune-up cleaner in gas to hopefully clear carbon crap out.
I let my dad time the distributor since he's done it before and he noticed something wierd about it. He said that he had to turn it a lot farther than normal to see any effect on how the engine ran. Instead of moving it 2 or 3 degrees to see a difference it was more like 6-8 degrees. We used a light gun (not sure of the porper name) and the needle was way off to start with and he thinks the distributor was installed wrong in the first place. We were trying to adjust it to where it would start pining and then turn it down a few degrees but never got that far.
The distributor was replaced by the previous owner with a unilite electronic distributor.
After timing the distributor there definitely is more power but not anywhere near what it should be!
Can anybody give a suggestion on what is wrong? I wish somebody who knew these engines really well could help us!
Any help is greatly appreciated
Wow, thats a beautiful car! My dad's old 69 was the same color.
You started w/ the same things I would have done as far as a tune up goes.
How long has it been sitting? It may need to be driven for a while too.
Does it run rough like it has a miss, or just has no power?
Here's my thoughts
If it feels like it has a miss check/change the plug wires. They may be arcing on something if the insulation is thin, or if they are cut or melted anywhere. Also check the dist. cap and coil (Is the coil part of the cap on that dist?). I would pull the cap and take a look at what the inside looks like. I have the cowl hood also and my cap gets a lot of currosion because the moisture comes in from the cowl right above it. I have the msd dist. Take a look at what my dist. looked like when I changed it https://www.tamparacing.com/forums/s...d.php?t=230330.
I would also change the fuel filter, its cheap and easy to do. And can keep small particals from screwing w/ your new carb. What kind of fuel pump does it have, mech. or elec.? Guage? Maybe low fuel pressure?
You said it runs rich, is that w/ the new carb? I don't know much about the Edelbrock carbs, but I would jet it down a little and see how it runs.
The timing is a big deal though. If it is way off and too low it will feel very sluggish. Try timing it w/ a light that has a dial on it and see if you can get the marks to line up. (I have too since my dist. is locked and I don't have any advancement) If you change the timing alot you may have to adjust the idle to go w/ it. If the timing is way down you may have to turn the idle up, and vise versa.
If nothing works maybe do a compression check since you said the exhaust didn't seem right. I've never done one, but I'm sure someone here could tell you how.
I don't know how much help I was
, but it could be a combination of things. I'm sure theres some others here that could help ya out.
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Thanks for all the suggestions. My dad has an old compression tester so I'll hook that up later and give it a go. Hopefully that is not the problem! The new carb came with a inlile fuel filter also. I'm not sure where the stock one is but having the 2nd one on there can't hurt. The fuel pump on this car is mechanical.
It has always run rich with the old carb and the new carb. It's not as bad as before though. If it's running rich I don't think it would be a fuel prssure problem do you?
I don't think any cylinders are misfiring it idles and drives smoothly it's just got low power, it's getting much better than before I started though.
Where should the timing marks be set at? Theres like a gauge with 20 lines and before I touched anything and it ran bad it was on the first line!
It has always run rich with the old carb and the new carb. It's not as bad as before though. If it's running rich I don't think it would be a fuel prssure problem do you?
I don't think any cylinders are misfiring it idles and drives smoothly it's just got low power, it's getting much better than before I started though.
Where should the timing marks be set at? Theres like a gauge with 20 lines and before I touched anything and it ran bad it was on the first line!
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Last edited by Silverstreak328; 05-12-2005 at 08:59 AM.
The Happy Mrs.
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My fuel pump is mech also and when I bought the car, the filter was in line from the pump to the carb. I'm not sure if one would be anywhere else, unless there is one along the rails. Don't use the glass see through ones. I have had the worst luck w/ them. They don't catch everything.
Your probably right about not having low fuel pressure if it's running rich. It should be fine though since its mech. But I would mess w/ smaller jets and see if it helps. I usually change them in increments of 2 to find what seems better. The carb may need some adjusting too.
For the timing, I would get under the car and clean off the balancer real good. The marks on the balancer should be marked w/ numbers. Make sure you can see them clearly. One should be marked 0, skip a couple and another should be marked 10 I think. If you use a light w/ out a dial read the number that lines up w/ the timing marker on the block to see what the timing is. If you use one w/ a dial, turn the dial till the line on the balancer that reads 0 lines up w/ the marker. Then look at the dial on the light and it will tell you your timing. I think mines around 17 initial, but does it matter that his is a big block? Mines a 350.
Your probably right about not having low fuel pressure if it's running rich. It should be fine though since its mech. But I would mess w/ smaller jets and see if it helps. I usually change them in increments of 2 to find what seems better. The carb may need some adjusting too.
For the timing, I would get under the car and clean off the balancer real good. The marks on the balancer should be marked w/ numbers. Make sure you can see them clearly. One should be marked 0, skip a couple and another should be marked 10 I think. If you use a light w/ out a dial read the number that lines up w/ the timing marker on the block to see what the timing is. If you use one w/ a dial, turn the dial till the line on the balancer that reads 0 lines up w/ the marker. Then look at the dial on the light and it will tell you your timing. I think mines around 17 initial, but does it matter that his is a big block? Mines a 350.
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diagnosis over the internet is kinda like it is over the phone. Take a plug out now that you have run it a little and see what it looks like, and recheck the gap. I see what looks like a fairly new brake booster on it. I would make sure all vacuum lines are routed right, on top of changing the wires. Soooo many things it could be, has the car been sitting for a long time? What kind of miles on motor? Any mods done to it recently?
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after the car is warm does the exhaust air come out even on both sides? there is a flapper thing just under one of the exhaust manifolds and when the car is cold, it's shut and makes the exhaust go threw the intake to the other side. if it's stuck shut you'll lose power.
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No even when it is warm it all mostly goes out the right side. Can you please elaborate on this flapper valve more and how I can fix it.
Thanks!
Thanks!
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it is between the exhaust manifold and the exhaust pipe. if you look under the car you'll see what looks like a spacer. that's it.
it took me 25 minutes to find a pic of one but i found it on ebay. look at the bottom of the manifold and see the spacer with the coil spring on it. that's it.
http://cgi.ebay.com/ebaymotors/ws/eB...category=34203
you could pull the exhaust pipe off and the exhaust crossover valve off ( heat riser) and pry open the valve or replace it with a new one. but you don't need one in florida. it just helps the car warm up faster by heating the intake.
it took me 25 minutes to find a pic of one but i found it on ebay. look at the bottom of the manifold and see the spacer with the coil spring on it. that's it.
http://cgi.ebay.com/ebaymotors/ws/eB...category=34203
you could pull the exhaust pipe off and the exhaust crossover valve off ( heat riser) and pry open the valve or replace it with a new one. but you don't need one in florida. it just helps the car warm up faster by heating the intake.
Last edited by 74javelin; 05-12-2005 at 05:35 PM.
