Lost power all of a sudden. 273 commando.

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trebor75

trebor75

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So let me explain. One week ago my car ran really really good. I have a souped up 273 commando. I'll give you the specs at the end of this. It still runs very good when I cruise around. No bogs, no nothing. But, when I stomp it it's like I have lost 30% of its power. It will hardly spin the tires. It is like it picks up slower then it did before. Still no bog or anything though. It just won't take of like it should. I have a 3000 stall converter and it won't flash that high now either. I don't know if it is because my engine lost torque. The converter is an b&m not even a year old. Maybe it's giving in? It shifts earlier then usually also. I can also now really feel when the secondary vacuum ports open, was not like that before if i stomped from a stop. When it's reved up it runs better but it still feels like i lost power through out the whole register. There is no miss firing, no bogs, just this lack of get up and go power.

Today I checked timing. What do you recommend for initial? I have about 12.
Checked if the throttle opens up completely. It does.
Adjusted valve lash. Perfect.
Tried different springs for the vacuum secondaries. I had the yellow spring in it before. I have now tried the stiffer black. I believe that made it better.
Checked the plugs, looked great.
Adjusted idle mixture screws for best vacuum. It idles perfect.

All I can think of is that it is way warmer outside now, way warmer and I have never had the brand new Holley in this heat before. Let me know what else info I can give you. I'm out of ideas as for today.

1970 duster
1965 - 273 commando
Cam: Comp Cams Magnum 282S - 282/282 Lift 495/495 (solid) Beehive Springs
Edelbrock D4B intake / Holley 670 Street Avenger
Pertronix Ignitor & Flame Thrower coil
Hooker Headers
2.5" Dual Exhaust / Super 44 Flowmaster
8 3/4 - 3.55 - SureGrip
727 auto / Shift Kit
10" 3000 stall converter
B&M Quicksilver Shifter
 
A guy on another site just had a similar issue. His car was running strong when it was cold but was a dog when it got up to operating temp. His issue ended up being an orange box that was failing. Do you have a points distributor to throw on it and see how it acts? I wonder if the Pertronix is going bad...
 
burdar said:
A guy on another site just had a similar issue. He car was strong when it was cold but was a dog when it got up to operating temp. His issue ended up being an orange box that was failing. Do you have a points distributor to throw on it and see how it acts? I wonder if the Pertronix is going bad...
Click to expand...

Thanks for that info. I wil defenetley try this out. Keep the ideas coming :)
 
...I have a 3000 stall converter and it won't flash that high now either. I don't know if it is because my engine lost torque. The converter is an b&m not even a year old. Maybe it's giving in? It shifts earlier then usually also...
Click to expand...

Stalls get their rating off a given torque at rpm, but if the torque drops, so will the "stall" but it shouldn't drop that much. You also mention the earlier shifting. Have you checked your throttle pressure linkage (kickdown) to make sure it's rigged correctly? If that's out of adjustment, early shifting can be one of the results...but it usually doesn't just suddenly lose adjustment unless it fell off the throttle linkage.
 
Shifting early and doesn't run as good as it did. Check the throttle cable and make sure it didn't slip in the bracket and now the carb is not opening all the way. I know you said it is opening all the way, but is that with the pedal and someone else looking or are you moving the carb lever under the hood with your hand?
 
txstang84 said:
Stalls get their rating off a given torque at rpm, but if the torque drops, so will the "stall" but it shouldn't drop that much. You also mention the earlier shifting. Have you checked your throttle pressure linkage (kickdown) to make sure it's rigged correctly? If that's out of adjustment, early shifting can be one of the results...but it usually doesn't just suddenly lose adjustment unless it fell off the throttle linkage.
Click to expand...

This is also what I was thinking, maybe the arm on the shaft coming out of the trans slipped?
 
txstang84 said:
Stalls get their rating off a given torque at rpm, but if the torque drops, so will the "stall" but it shouldn't drop that much. You also mention the earlier shifting. Have you checked your throttle pressure linkage (kickdown) to make sure it's rigged correctly? If that's out of adjustment, early shifting can be one of the results...but it usually doesn't just suddenly lose adjustment unless it fell off the throttle linkage.
Click to expand...

I checked it and it is just as before. I had the car set up and tuned really well. It's all very strange to me. I'm not that exprecienced but I'm not a beginner either. I've done everything myself on this car so far, but when it comes to diagnosing I lack experience.
 
B-onefan said:
Shifting early and doesn't run as good as it did. Check the throttle cable and make sure it didn't slip in the bracket and now the carb is not opening all the way. I know you said it is opening all the way, but is that with the pedal and someone else looking or are you moving the carb lever under the hood with your hand?
Click to expand...

This is what I was hoping, but no. I checked with a friend pressing the pedal and me chick the throttle shaft and linkage, it's completely open and wont travel more. Looked down the carb and it's completely open. Now, this Holley is new to me and I thought it might be the very, very hot temp out today, but I drove it tonight when it's cool and it's the same.
 
burdar said:
A guy on another site just had a similar issue. His car was running strong when it was cold but was a dog when it got up to operating temp. His issue ended up being an orange box that was failing. Do you have a points distributor to throw on it and see how it acts? I wonder if the Pertronix is going bad...
Click to expand...
Thats why I said about advance I feel the same it is probably a spark issue.
 
cletus said:
This is also what I was thinking, maybe the arm on the shaft coming out of the trans slipped?
Click to expand...

No, checked all linkages. It's fine, I had my friend press the pedal and the kickdown is also adjusted and set up as it should and as it was before when it was running strong. I'm thinking it could be a timing issue and maybe the Pertronix is giving up, as mentioned earlier. Will continue to diagnose when my friend have time to help me so I can properly check at what rpm I have full advance.
 
Have you checked your ignition yet for a strong spark?
How much difference in temperature and humidity since you last drove it and it was running well?
Have you checked your float levels (maybe it's running a little lean?)
Is there any other difference in the way it runs? (operating temp)
Is your air cleaner dirty?
 
chryslerfat said:
Thats why I said about advance I feel the same it is probably a spark issue.
Click to expand...

I was writing while you posted. This will be the next thing to look over. Thanks for all the help so far, much appreciated. This site is the best!
 
If you think your timing isn't working correctly, but your vacuum is still working, check your advance weights/springs for proper freedom of movement. Vacuum advance is essentially inop during heavy acceleration and you said it runs fine when it's up to speed (when the load is down and vacuum is up)

EDIT: try disconnecting your vacuum advance and check your timing that way...it will isolate the mech advance for troubleshooting.
 
txstang84 said:
Have you checked your ignition yet for a strong spark?
How much difference in temperature and humidity since you last drove it and it was running well?
Have you checked your float levels (maybe it's running a little lean?)
Is there any other difference in the way it runs? (operating temp)
Is your air cleaner dirty?
Click to expand...

1. No, this I have not really checked actually.
2. Not really humid, but very hot, like 29 degrees celsius, more then twice as much as last week.
3. No, but is it likely that would be the cause all of a sudden when it ran well just one week ago? The carb ran great out of the box, brand new. I did a little fine tuning and it was a big improvement over the edelbrock I had before.
4. Besides the lack of power as described, no. It runs great. It did run hotter, but it was really hot outside, so it usually does.
5. Air cleaner brand new.
 
txstang84 said:
If you think your timing isn't working correctly, but your vacuum is still working, check your advance weights/springs for proper freedom of movement. Vacuum advance is essentially inop during heavy acceleration and you said it runs fine when it's up to speed (when the load is down and vacuum is up)

EDIT: try disconnecting your vacuum advance and check your timing that way...it will isolate the mech advance for troubleshooting.
Click to expand...

Thanks for the help. I will look into it. I actually run a plugged distributor vacuum advance though, it has always worked great. Will hook it up tomorrow to see, but it seems unlikely that would be a problem when it worked before dont you think?
 
Did you slip your timing chain? How many miles on it?
 
Let's hypothesize for a moment..........you've checked timing, advance, carb, reasonably sure of your ignition module, alot of stuff and nothing is jumping out..........let's say that the engine is still running just fine as it always had, could there be a problem with eather, or both, converter, tranny? Engine's making power, just not making it thru the drive line.
It's an idea......
 
mvh said:
Did you slip your timing chain? How many miles on it?
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Cam swap last summer. All new parts including timing gear and chain.

JBurch said:
Let's hypothesize for a moment..........you've checked timing, advance, carb, reasonably sure of your ignition module, alot of stuff and nothing is jumping out..........let's say that the engine is still running just fine as it always had, could there be a problem with eather, or both, converter, tranny? Engine's making power, just not making it thru the drive line.
It's an idea......
Click to expand...

It has crossed my mind. Tranny was gone through last summer, not by me but by a shop. Put in a brand new converter meanwhile. I'm not so sure about the pertronix module. That swap was done by a previous owner and could be old.
 
trebor75 said:
Thanks for the help. I will look into it. I actually run a plugged distributor vacuum advance though, it has always worked great. Will hook it up tomorrow to see, but it seems unlikely that would be a problem when it worked before dont you think?
Click to expand...

Oh ok, yet one more time where I shouldn't assume. Most folks I figure would use vacuum advance, but if you're not using it and you're still making max advance, I'd just make sure the weights and advance plate moves free and smooth.

This may be a bit of a dumb question, but it is taking off in first, right? I had a problem with my wife's Mustang once. It has a sticky accumulator piston in the housing and it wouldn't downshift to first when you come to a stop. The car would still take off, but it was actually starting in 3rd gear, so the car felt like a complete slug and somewhat resembled your description for the lack of stall and poor performance even though the engine ran fine.
 
I'm not totally sold on the pertronix being bad...most of the time those are a go/no-go type deal and unless your pickup loosened, it shouldn't start acting that way.
 
txstang84 said:
Oh ok, yet one more time where I shouldn't assume. Most folks I figure would use vacuum advance, but if you're not using it and you're still making max advance, I'd just make sure the weights and advance plate moves free and smooth.

This may be a bit of a dumb question, but it is taking off in first, right? I had a problem with my wife's Mustang once. It has a sticky accumulator piston in the housing and it wouldn't downshift to first when you come to a stop. The car would still take off, but it was actually starting in 3rd gear, so the car felt like a complete slug and somewhat resembled your description for the lack of stall and poor performance even though the engine ran fine.
Click to expand...

No question is dumb when you are trying to help. But yes, it takes of in first while in drive, and the tranny shifts great. I have a B&M Ratchet so I have shifted it manually also and I can still rev the engine to 6000 rpm before shifting.

ProStocker273 said:
Don't forget compression test
Click to expand...
Yes, compression and spark will be the next tests.

Now, the only part that is new to me is this 670 Holley Street Avenger, it's only a couple of months old but worked really well with my setup. Is there anybody on here that has had a problem like mine and ended up being the carb?
 
Was this the same carb you had on before when it ran as well as it did? If not, it may need some more tuning or the throttle pressure linkage may need adjusted.
 
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