Struggles after 4900 rpm

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trebor75

trebor75

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My Duster usually shifts from first to second gear at around 5500 rpm, and chirp the tires.
Now it shifts at around 4900-5100 and wont chirp the tires. It feels like it it struggles when it reaches 4900 rpm and don't want to rev more. There is no pinging or destructive sounds, it just feels like it hesitates. Before it would pull really hard on the higher revs.

My combo:
1965-273
727
340 Cam
Edelbrock D4B intake / Edelbrock 600 Performer Carb
Headers
2.5" Dual Exhaust
8 3/4 - 3.31 - SureGrip

The most recent things I have done before this problem started are:

- Changed the plug wires. Had a used set with better lengths lying around.
- Moved the coil a little further away from the dist on the firewall.
- Bumped up my initial to around 18-19 btdc, not having timing tape I’m not sure what the total was, but it did run very well with no pinging.
Set the idle mixture according to Edelbrocks manual

I will say that it did run excellent for a while after doing these things. So once again I ask the experienced people of this great forum for advice before I go spend money on plugs and wires etc....](*,)
 
Now that you have bumped up the initial to 19btdc you might be running more than the max 34-35 degrees with full mechanical advance, if you can I would invest in a timing tape to make sure you are not exceeding the 34-35btdc at 2500rpm (mechanical advance all-in).

If you have the vacuum canister hooked up then you shouldn't exceed 50btdc at cruise speed (part throttle, high vacuum with timing all in). Too much advance might result in detonation and you can't always hear it.

Did you set your initial timing with a timing gun and with a vacuum gauge hooked up? The engine will let you know where it wants to be. Set the initial timing to where you get the highest vacuum rating (vacuum gauge hooked up to manifold port not the ported on the carb). Make sure while doing this you keep the idle rpm low so the distributor doesn't add in any mechanical advance. Once you figured out where the initial timing want to be then you'll have to limit the mechanical (centrifugal) advance to 34-35 degrees.

Have you checked the spark plugs for any sign of detonation?

Since you changed a few things before this happened you can always change individual items back to how they originally where just to check if any of the items are bad. Old spark plug wires can look good but miss or spark-over at high rpm. Just a thought.

Good luck.
 
Sounds like it's running outta fuel.
 
Now that you have bumped up the initial to 19btdc you might be running more than the max 34-35 degrees with full mechanical advance, if you can I would invest in a timing tape to make sure you are not exceeding the 34-35btdc at 2500rpm (mechanical advance all-in).
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I intend to do this as soon as possible. I have also set my initial to around 13 now, but with the same result.

If you have the vacuum canister hooked up then you shouldn't exceed 50btdc at cruise speed (part throttle, high vacuum with timing all in). Too much advance might result in detonation and you can't always hear it.
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Is detonation the same as pinging? Sorry, but I dont know that word. I'm from Sweden :D

Have you checked the spark plugs for any sign of detonation?

Since you changed a few things before this happened you can always change individual items back to how they originally where just to check if any of the items are bad. Old spark plug wires can look good but miss or spark-over at high rpm. Just a thought.

Good luck.
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How will they look if there is detonation (that word again)?
Thanks for all the advice and suggestions, I will look into all of them!

Any chance this could also be related to the coil?
 
Is detonation the same as pinging?
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Yes.

You stated it ran excellent after your previous adjustments. Then you changed the filter and now have issues. Makes me wonder if some of the rubber line got up in the carb, did you use new line?
 
Badsport said:
Yes.

You stated it ran excellent after your previous adjustments. Then you changed the filter and now have issues. Makes me wonder if some of the rubber line got up in the carb, did you use new line?
Click to expand...

Yes for a while it did run very good and I had no pinging/detonation. Same thing after the filter change. The issues did not start directly after that and my my rubber lines a not even a year old.
 
I think it's those wires you put on there. If you have a digital ohmmeter, check the resistance in all the wires, the resistance should be close to each other. If you have one that's really out of whack from the others, then you probably found your culprit.

Or like the 67cuda360 said, change things back and see if the problems go away.
 
If you take the spark plugs out and have a good look at the white ceramic there shouldn't be any black or metallic speckles on it. If there are very tiny spots of metal looking dots on the ceramic then you've had detonation/pinging and the small specs you are seeing are molten bits of metal/aluminum from your combustion chamber.

Don't worry though I don't think this is your issue. Try changing things back one at a time and see if you find your culprit. Another problem might be the ignition box (module) breaking up at higher RPM.

Burntorange70 had a great point. I'm actually having an issue with my car now that its really hot here in Toronto. It could very well be a fuel delivery problem where the fuel is boiling in the fuel line and the pump can't deliver enough fuel to keep the bowls full on hard full-throttle runs. Have you tried driving it when it is cool out (evening) to see if the problem is the same?
 
Thanks you for all the replys. Very much apreciated.

First thing today is to get new plug wires and check that fuel filter again. The hose coming out of the pump is going into the filter on the side marked "In" right now. That should be correct right?

I also thought about it being hot outside, but yesterday it actually was nice and cool outside when I tried it.

So today with new cables, and trying to go back one step at the time I will see if I make any progress and get back to you.

Thanks again!
 
You really should learn some diagnostics. You might fix it throwin parts at it, but you won't learn anything.
 
StrokerScamp said:
You really should learn some diagnostics. You might fix it throwin parts at it, but you won't learn anything.
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A valid point. That is why I asked here first. The plug wires I've been meaning to swap for some time though.

I learn a lot all the time through this great place, books, friends and by doing. When I got this Duster I had never before done any work to any car actually. Now I have on my own swapped out the entire drive train and all that task includes :)

The rain is coming down hard, so I cant go for a test today. I will end up in the ditch If I try to floor it.
 
trebor75 said:
First thing today is to get new plug wires and check that fuel filter again. The hose coming out of the pump is going into the filter on the side marked "In" right now. That should be correct right?
Thanks again!
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Yup, just threw it out there you never know.
 
.............What happens in the higher gears, does it nose over sooner or same......if its fuel problem it will be sooner..kim........
 
Just want to say that all is well again. I put new plug wires on and now it's back to normal. Can also mention there was no signs of detonation on the plugs, they looked really good.

Thanks for the help!
 
trebor75 said:
Just want to say that all is well again. I put new plug wires on and now it's back to normal. Can also mention there was no signs of detonation on the plugs, they looked really good.

Thanks for the help!
Click to expand...

That's great to hear.
Always nice when a fresh set of wires fix all your problems LOL
Enjoy.
 
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