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Slowness Thoughts

R

RoadRunning

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Recently just finished up my 1970 Road Runner project. It has a 383 engine, eddlebrock manifold, Holly 4 barrel Carburetor, purple cam upgrade, headers, turbo walker exhaust, new plugs, wires, starter etc..new fuel system as well. We also put in a rebuilt torqueflight 727 transmission with a torque converter. To finish the build we took it to a reputable shop to get everything dialed in and finish up what we could not as well as tune the ride as best as possible. Took it for a test drive the other day and the car runs very well. Smooth. Idles nice, cruises great, starts right up etc. The problem is that it has no power, I do not think it would be able to do a burnout even with the posi traction. I can floor the gas pedal and the exhaust will roar a bit but the car will only slowly increase speed. It did not used to be this way 20 years ago before the new carburetor and transmission. Perhaps it is not downshifting to the passing gears? Perhaps the transmission was not rebuilt correctly? Perhaps the secondaries on the carb are not activating (although I would have thought the shop who tuned it all would have caught that). Anyone have any thoughts on what could be going on? The car runs great except it just doesnt have that muscle car pickup speed anymore. Just gradually increases speed and does not throw you back in the seat even a little bit.
 
What cam did you install in it? It’s very easy to over cam a 383.
 
Red63440 said:
What cam did you install in it? It’s very easy to over cam a 383.
Click to expand...
It is the popular purple cam upgrade for the 383. It was installed when I bought the car 20 years ago and the car had good power at that time so probably not the cam I think..
 
Transmission starting out in 2nd gear ? Trans pressure rod/cable adjustment out ?
 
65wgn440 said:
Transmission starting out in 2nd gear ? Trans pressure rod/cable adjustment out ?
Click to expand...
I do not know much about the ins and outs of transmissions but this sounds highly plausible.
 
Run it manually through the gears. Shift to 1st from a standing stop, and then do your upshifts manually by ear/tach. Then do it again starting in drive and count the shifts. If it's starting in 2nd (when placed in drive), I believe that would be governor, main trans pressure, or maybe something with the front band ? If it won't "Kick down" from 3rd to 2nd when driving (at, say 45MPH) and you stomp on it, that would probably be the kick down linkage or related?
 
MarkLevi said:
Run it manually through the gears. Shift to 1st from a standing stop, and then do your upshifts manually by ear/tach. Then do it again starting in drive and count the shifts. If it's starting in 2nd (when placed in drive), I believe that would be governor, main trans pressure, or maybe something with the front band ? If it won't "Kick down" from 3rd to 2nd when driving (at, say 45MPH) and you stomp on it, that would probably be the kick down linkage or related?
Click to expand...
I am not feeling a kick down for sure when stomping on it at 45mph. I should have noted this is an automatic transmission so I cannot manually shift it. I thought I could feel it go into all 3 gears as I drive however. Will need to check that again to make sure it is not starting in 2nd gear I suppose.
 
You can manually upshift and downshift - just use your gear selector lever.

From "Park": Put it all the way down in "1"; then 'take off' from a standing stop. Then carefully upshift to "2" and "3" as you accelerate. You should feel each shift occur.

Similarly, drive at ~45MPH; floor it, if it doesn't down shift (Just kind of "bogs"), do it manually by moving the lever from "3" to "2" and see if it makes a difference?
 
Check out this video and follow along with him. Skip the part about the internal spring.
 
MarkLevi said:
You can manually upshift and downshift - just use your gear selector lever.

From "Park": Put it all the way down in "1"; then 'take off' from a standing stop. Then carefully upshift to "2" and "3" as you accelerate. You should feel each shift occur.

Similarly, drive at ~45MPH; floor it, if it doesn't down shift (Just kind of "bogs"), do it manually by moving the lever from "3" to "2" and see if it makes a difference?
Click to expand...
Verified, I am getting all three gears when we manually put them in each one..
 
Good replies on kickdown adjustment if you're not familiar with this; but would think the shop doing your dial-in would easily catch this. I only have a built poly about 325 HP and higher gearing; but the rubber burning I could get and the chirping btw gears (I put in a shift kit) largely diminished when I went to larger diameter radial tires...they don't break free as do the old poly tires. Just sayin in case your tires are different now...
 
It should shift into 2nd gear somewhere between 45-55MPH when it is floored then into 3rd somewhere after 80MPH. Give or take.
 
If it starts to pull harder as the rpm gets higher then you may have a retarded camshaft timing set. Just installing with the dots lined up doesn't mean the valve time is correct.
The ignition timing could be retarded as well. I'd check that first since it's pretty easy.
 
Just putting this out there...but have you driven any muscle cars in the last 20 years, or is this the first one?

Could it be 20 years of driving modern cars has changed your perception of speed?

I don't know your circumstances but sometimes these cars don't seem as fast today as our memories recall...
 
66 Sat said:
Just putting this out there...but have you driven any muscle cars in the last 20 years, or is this the first one?

Could it be 20 years of driving modern cars has changed your perception of speed?

I don't know your circumstances but sometimes these cars don't seem as fast today as our memories recall...
Click to expand...

A 1970 roadrunner 383 should be able to burn the tires pretty easily.
Something is wrong: no compression, mixture, ignition timing, cam timing...could be a little of everything.
 
RoadRunning said:
Smooth. Idles nice,
Click to expand...
A Purple Shaft 383 really shouldn't be described as "Smooth" or "Idles nice" unless, by "idles nice", you mean sounds like an old fighter plane getting ready to do battle :thumbsup: !
Does your car sound about like these?


If not, you might have some kind of tuning/timing/carb issue going on?

When you did manual gear control, how did it compare to when you let the trans decide for itself? If it's not "kicking down" when you stomp it to the floor at ~45, it almost has to be kickdown linkage (hopefully) or something deeper in the trans (hopefully NOT).

What Holley carb do you have it paired with and is the fuel level correct in the bowl(s) - I assume some manner of double-pumper?
 
Don Frelier said:
A 1970 roadrunner 383 should be able to burn the tires pretty easily.
Something is wrong: no compression, mixture, ignition timing, cam timing...could be a little of everything.
Click to expand...
I agree something does sound off, but we don't know the full build details either. If it's got 265 rear tires and a 2.76 rear end and a big cam, you know, a total mismatch of parts type of thing. Maybe the kickdown isn't adjusted properly so at 30 mph it's doing all the work in top gear and it's not on the cam yet? Maybe the OP drives around in a 911 Turbo everyday so thinks everything else is slow?
What's it like in a stoplight drag? Just hold it on the brake and load up the converter and let 'er rip.
More info. is required I reckon.
 
After checking tranny shift intervals, check the timing and advance too.
 
You need to go to a race track and find the oldest mopar guy there to test drive it.:praying:
 
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