help
 

ok car slows down 3 tenths changed trans and converter no change leaked motor down no problems compression also good changed coil and plugs no change valve springs are fine checked power and ground at msd box no problem changed msd box no change. please send me down the right path. vehicle is 340 low compression engine thanks

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also checked fuel pump and pressure and changed fuel no change

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Brake dragging? Sucked intake gasket? Changed fuel? (I ran out of my Sunoco blue this weekend, bought VP 110 at the track and lost .15!) :eek: Secondaries opening?

Try replacing the diaphragm in the regulator. I've heard of them doing the 'gas can test' just fine, but still not working properly downtrack under a load.

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Throttle cable adjustment, opening all the way? Try swapping the whole carb as that could eliminate a few potential possiblities. Bolts tight?

Is it through the whole range, launch (60' & converter flash) to finish (mph)? How much is the weather different between the last good run and when the problem showed up? Anything different with the air filter, filter base, etc.? Same weight?

How old are the plug wires, cap & rotor?
Batteries & alternator putting out good voltage to everything?
Check battery terminals for corrosion.

Distributor leads tight? I had a wire start wiggling out of the plastic connector, shut the motor off and wouldn't restart. But it could cause an intermittant miss down track.

Sounds like it has to be something simple.

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thottle is opening all the way and so is door its slow all the way through down across the ticket doesent miss a beat just feels flat batterys test fine cap rotor brand new wires about a year old i checked dist leads clean and tight and they ohm good

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Checked oil for metal.Might be wearing cam lobes?

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By chance are you running a clutch fan for cooling?

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Check the balancer and ensure that the outer ring hasn't spun on the inner hub. If thats happened, it obviously would show incorrect ignition timing. I got burned on that one many years ago.

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Could it be a bad timing chain ?
Ours slowed down .15 in a week with no changes. Nothoing else seemed unusual until the timing chain broke. When the mess was cleaned up and timing chain replaced it was all back to normal.

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no clutch for cooling fan i just ripped the timing cover off looks fine as far as the cam lobes lash was fine cam looks like new also has shubecks checking dist leads now

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I would try another carb, Holley, AFB , Q-Jet, etc to see if it slows down or picks-up ??? Also, how about a Chassis Dyno ??? They can find lots of things and save you Time & Money, no to mention pulling
all your hair out ... Maybe a bad connection / ground or a wire over heating ? It's always tougher when it doesn't miss or backfire etc ...
* Keep us informed & good Luck....

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Rob check brake system real good sometimes a brake line (factory rubber coated ones) will not let brake fluid return causing the rotor(s) or drums to stick on after applying the brakes. Or make sure nothings bent somewhere.Does the car coast? See if after holding the brake pedal the car rolls. or see if they stink from heat. Sounds dumb but ive been there. Keep us posted and good luck. Mike

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If you lost the three tenths between the last week of June and the first or second week of July, consider the radical weather change. If you were jetted a little rich last month, you are way too rich in the oppressive gunk we've had for air this month.

Change your metering rods, and you might regain half of what you lost.

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Have you been logging your air/fuel with a wide band? You should do that, besides tuning it's a good reference when something like this happens.

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no its just been slow since may very consistant but slow

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I had a very similar problem many years ago with my 71 Duster stocker. Changed everything, ignition, fuel system, trans, convertor, etc. etc. Nothing I did made any difference so far as being faster or slower. Turns out the 8 3/4 rear end housing had bent after MANY years of use and abuse. I didn't have a brace welded on at that time. The way I found it was I was going to install my spare hogshead to see if that was the problem. It was near impossible to remove the axle shafts. It might be worth looking at.

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thanks i will tear it apart thursday after work i dont have a backbrace either and its old rear end

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I had a friend who ran A/SA with a hard-leaving car (G.M. 12-bolt) that suspected that his rear end housing was bent, and it was... pretty badly, BUT in just the opposite way you'd expect; his rear tires were toed OUT, not IN, as you'd think they'd be.

Go figure....

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i wanna thank everyone for the help and input i as we speak am ripping the rearend apart to inspect things thank you

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This is a good discussion! why a RacePack does wonders. hope you find your bug without to much exspense.

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Ran into the same thing a couple years ago with dads stocker...it just slowed down we did everything then the weekend before thanksgiving the car left the line & then shook like hell! Took the teeth off pinion!

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Don't know if you're running a crank trigger, but if the sensor goes bad, it will still crank and run, just won't run fast.

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no crank trigger but we think we found the issue and we believe it is in the carb hesitates on launch not sure what it could be maybe door spring?

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Yup. It's usually something really simple! So simple you don't even think about it! Jim