Why is my top speed 70 mph?

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:happy1:
RustyRatRod said:
Did you actually DO the test I outlined?
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do rusty's test as outlined.......report back.
someone else suggested replacing the fuel filter, great advice.....
magnum dart suggested an exhaust restriction and how to check it, another good idea.....

do these three and then tell us the results..........all these could cause a drivability problem as your saying......

once these are eliminated, then we could go on to something else.......one of these could easily solve the problem....
higgs
 
Over revving in 1st/2nd gear as mentioned by the OP....incorrect throttle pressure linkage (kickdown) adjustment, and may have already burnt up the trans from how many miles of driving it this way!! That would be my guess, trans slipping/toast!! May not even be hooked up!!

How about a pic of the carb area? That may shed some light on this! Geof
 
I could go well over 100 with my 318 / 904 and 4.10 gears. The engine sounding like it's going 120 and only doing 70 sounds to me like transmission slippage. Check the fluid, look for clean, red fluid with no burned smell. Pull the transmission pan if you have the inclination. Look for excessive metal on the magnet and a dark film / sludge on the bottom of the pan from worn material. If any of those are apparent, it is not good, but change the filter and fluid anyway and drive it again.
 
[ame="https://www.youtube.com/watch?v=RNgjS5mHI0E"]How to find your differential gear ratio without stamps, tags, or tear down - YouTube[/ame]

Easy way to determine gear ratio.
I also doubt that's the problem but its nice to know regardless.

He did say "the carb is open". That should be clarified, meaning, make sure the throttle is opening ALL the way. Likely need to disconnect the linkage to do this.

Not to make light of the OPs problem but its interesting watching people play this game.

To the OP - you will get great help here if and only if you read carefully and do what has been suggested, then report the findings.

Of course there are sometimes a lot of suggestions. Do the very simple easy things first. It only takes a few minutes to verify the carb is opening, check the air filter, check exhaust pressure.
 
Looks like there consensus that there's something wrong.
I would step back & first determine if it's low engine output or something downstream in the driveline.
So first I would check engine stuff like getting full throttle, fuel filter, ignition timing, exhaust back pressure, clean air filter & stuff.
If nothing seems really out of line with the engine start checking trans stuff, burnt fluid (indicates trans issue) & kick down linkage.
You also might want to check for brake drag.
A vacuum gauge on a full throttle fun might tell us a lot too.
But if I had to make a wide guess I'd say it was a trans/ torque converter issue.
 
ansonservice said:
Yes. I did that. It is open.
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Just to clarify, you had someone in the car holding the pedal to the floor correct?

And when they did that, did you physically try and move the throttle on the carb to see if it would go back further?
 
This is probably going to be one of the silliest things to ask (you should expect a few silly questions from me, FYI) but I had problems getting it started today (again, a wiring issue I am trying to find) and so I pushed it a couple of feet and found that the rear wheel was squeaking as I pushed it and it was difficult to push even with a slight decline. It made the same sound that it makes if the E-brake is on. I got underneath and there is no E-brake cable even, so I fiddled with the outside of the drum and there is something wonky going on with the E-brake cable coming out of the drum (it is very loose and makes a lot of noise inside the drum). It was getting dark, and it started raining, so I did not dissect the rear drum brakes to see if I had an E-brake rusted and stuck on. It does not push easily, and it does not roll as easily. I am wondering if this is the problem. I do not smell burnt brakes when I drive it, but I will check into it and see if there is just some pressure on the brakes. And yes, I did have it in neutral. I certainly appreciate all of your suggestions. Be patient with me as I do not have an inside place to work on this, and I live in WA state, where it will be raining from now until July. We are also expecting a cold snap, so I am not sure when I will be able to dig into this. Hopefully tomorrow, but maybe not. Oh yeah, and I have this thing called a job that keeps me from my cars. ;)
 
I mean no disrespect when I say following, so please don't take it as such. Now that I have said that, if you do take it that way, it's all on you.


First, from your original post and responses, it sounds like you have very limited knowledge of automobiles. That's cool. We all did at one point. That said, I highly recommend that you get a FACTORY Chrysler service manual for your car. We have them available somewhere on this site as a linked download for some models for free. If yours is not among them you can find one on Ebay. And I mean FACTORY CHRYSLER, not some Chiltons, Haynes or other craptastic garbage.

You said you did the test I outlined. I did not ask you if the carburetor was opening. We all already knew it had to be if the car was moving. I asked you to check to see if it was opening ALL THE WAY as far as it can. If you did not physically GRAB the carburetor linkage while someone had their foot to the floor on the gas pedal, you did not check it as outlined. Your answers there have been very vague and unclear at best. Much like a mud puddle.
 
magnumdart said:
If it has dual exhaust you can put a little back pressure to each pipe, I just use my hand for a second. Both sides should have enough to blow your hand off.
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Damn - that's gotta hurt! I guess you can only do this twice.... unless you use your wrist nubs that are left the next time......
 
RustyRatRod said:
I mean no disrespect when I say following, so please don't take it as such. Now that I have said that, if you do take it that way, it's all on you.


First, from your original post and responses, it sounds like you have very limited knowledge of automobiles. That's cool. We all did at one point. That said, I highly recommend that you get a FACTORY Chrysler service manual for your car. We have them available somewhere on this site as a linked download for some models for free. If yours is not among them you can find one on Ebay. And I mean FACTORY CHRYSLER, not some Chiltons, Haynes or other craptastic garbage.

You said you did the test I outlined. I did not ask you if the carburetor was opening. We all already knew it had to be if the car was moving. I asked you to check to see if it was opening ALL THE WAY as far as it can. If you did not physically GRAB the carburetor linkage while someone had their foot to the floor on the gas pedal, you did not check it as outlined. Your answers there have been very vague and unclear at best. Much like a mud puddle.
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No offense taken. To be more clear, yes, I did what you suggested. That is all good. I had my father in law help me out and we went through several of the things suggested here in this forum. He is good with cars. We believe that it is not an engine or carb problem. Sorry if I seemed dismissive about your suggestion about the carb - we tested it quickly and went on to other things it might have been. I got 100 different suggestions from the excellent people here and have not tried them all so I hope nobody is thinking I am car ignorant or snobby for not trying every suggestion within 24 hours of it being suggested. I am new to cars in some ways, but very familiar with cars in other ways. I brought a 1964 Ford Galaxie back from the dead and restored it into a police car that is now in near mint condition. I have rebuilt aircooled engines and can do all of my own body work. I have NOT yet had the pleasure of rebuilding a water cooled engine or transmission yet, so in that regard, yes, I am not very familiar with cars in that specific area. However, I am growing in my knowledge of cars, which is not bad for a Ph.D. who spends so much time in an office. Anyway, for me, classic cars are an educational experience, and once I take on a project, I tend to become more knowledgeable than most in that area. So, give six months and I will be able to write my own manual on the 318 engine. :) Thanks again for all of your suggestions and I will continue to work through the suggestions you all provided as time allows.
 
Keep in mind when you are working on a forum such as this, we can't see and don't know exactly what you did or didn't do. It's important to relay the info as precisely as possible so everyone can see what you see, if that makes sense.

I know you mentioned brakes, but I can't see that being the main cause if you can run the car up to 70.

My guess would be fuel related (starvation), poor tuning, and it could very well be a trans or converter issue. The key is to work through each step, and respond back precisely with your findings, and then move to the next issue.

I didn't see if you answered the question about catalytic converter. If it has one and it's plugged, that would cause the symptoms you describe.


I'm also going to throw this out there as stupid as it sounds. Have you inflated the tires to proper air pressure?

I bought a mid 80's Grand Prix about 20 years ago, and got it real cheap, it was a really nice car. The guy I bought it from had taken it to a local dealer and they told him transmission troubles, this and that blah blah blah. So he sold it to me for a song because he was having the same problem, couldn't get it over 50 or 60 mph.

I handed him the cash, grabbed the title and took off for home, he was right, it wouldn't run. I stopped at one of those quarter air machines and inflated the tires, jumped in and took off up the road toward home, promptly hitting about 90. They didn't look low at all, but that was all that was wrong with that car, My wife drove it for 5 or 6 years.

True story!
 
a Holley 1920 on a 318 will wheeze like a trachiotomy on a distance runner. Although it would probably be able to bust them loose in first. Look into the timing and the advance of the distributor. 2 and 4bbls will still push that car past 70. it may all be ignition too if you say its hard starting. still have the ballast resistor? the rear end ratio on a one legger is a little deceiving when they are off the ground. you can do this with a buddy: paint a white dot on the driveshaft and mark a rear tire with chalk. lay next to car and use a flashlight to watch driveshaft. have buddy push car slowly while watching the tire and stop at one complete revolution (~ 6.5 feet) while you count the turns. Its going to be 2.76 or more. Thats your rear end ratio. Youll need timing light to check timing at rest (12-16 BTDC) and at 2400 RPM. It should be around 32 BTDC (vacuum removed and plugged) at 2400. plugged fuel filter will idle all day but as soon as you get into it itll start to sputter. Choked exhaust is similiar but I have never had an exhaust that was so choked it slowed the car. if the car shifts from first to second at ~30 the kickdown lever is hooked up. If it weren't you'd be in 3rd before you crossed the intersection.
 
"My" next check would be to make sure none of the brakes are holding. Easy to do. Just jack up one wheel at a time and turn. I like doing things in a particular order, beginning with the simplest things first, because they are all easy and quick checks.
 
Just be concise with what you checked. Like
a. Jacked wheels up, turn freely.
b. No cat, pipes are damage free, exhaust flows freely.
c. No animal, vegetable, or mineral material wrapped around drive shaft.
d. Pulled trans dipstick, oil is full, clean, bright red, and free of burned smell.
(We can worry later if it is the right stick.)
e. Pulled fuel line at carb, full flow is satisfactory.
f. Right rear donut tire is properly inflated.
There are many good suggestions here. If you skip some because you may not understand, or say lack a specific tool, tell us that too. Once again, we are not there. I am hoping that you are able to resolve this, as I would like to know how it works out. So many times these threads die when the OP figures it out and the rest of us never know what happened. Have at it, don't let the car win.
 
Sounds like he has a good handle on working on cars, so I'm leaning towards the electrical side of his posts! If his car has had a number of things replaced or maybe upgraded to electronic ignition, maybe there is not enough fire in the hole to run it! Something in the wiring, or maybe running the stock coil with electronic ignition may be limiting the output of the ignition system??

Just thinking out loud here, and I still think the throttle pressure linkage could be the problem! Something about his post of over revving before shifting into the next gear gives me the feeling that it is/has not been adjusted properly, or not hooked up at all, and is or has burned up the trans!!
 
After Rustys first test, I would be checking the cam timing. 318s are known to jump any time after 90,000 miles. They lose power fast when that happens. And while the valve cover(s) is/are off you can check the valve spring pressures. And for goodness sakes put a tach on it.A restricted exhaust is a also a good diagnoses.One last idea is a faulty torque convertor, but thats a stretch.

I bought a 71 Demon once a long time ago, knowing it was hard to start. The only way it would run at all was to hold the gas pedal to the floor, and crank the dizzy until it started firing.If I did it just right it would fire up and run, just above idle with the 2bbl butterfly WOT. I forget how many teeth the chain had jumped. Might have been 7? IDK.Anyway, cheap fix. I made a little coin on it several times. It was a heap. I would sell it to one of my younger brothers friends for $350 or so with the agreement that I would buy it back at any time, for maybe $50 or so.I cant remember how many times that deal was made. Eventually I parted it out. The tranny in that car was the best shifting OEM 904 I ever came across. I took it apart and built 2 clones.I think I might still have one in my stash somewhere. Just reminiscing.
 
Make sure the mechanical advance in the distubuter is working . If it's sized you'll vave a real dog.
 
-Going back to post#46, re; restricted exhaust.
-Over the years Ive come across I think three restricted exhausts, so its not that common I suppose. I remember a mid 2000s truck that came in,with those symptoms. I drilled a hole in the exhaust pipe just ahead of the catalitic convertor and plugged a pressure guage in there. I found 4psi in there at idle, and climbing with load, on a road test. Not knowing what it should be, and wanting to be sure of my diagnoses,I checked it after the cat,where it was as good as zero.So I sent him off to the muffler shop, where the problem was cured. (Im not fond of exhaust work, and they were practically next door.) Afterwards I found less than 2psi under acceleration in 2nd gear, and then the wee holes were welded up
-I know you likely dont have cats, but you do have a muffler.Same story.
-I used to see that all the time on 2-stroke dirt bikes in the 70s and 80s. In fact I made it part of my tune-ups to burn out the carbon from those plugged baffles.
-Certain 4-strokes used to come in with loose baffles that would rotate and choke the exhaust too.
-When I was young,about 17or so, I was pulled over for a noisy exhaust and given a week to show up at the station house with it quieted down. So I rolled up some cardboard from a big box(the corregated kind), to make plugs, rammed them up the pipes, and locked them in there with nails.When I showed up for inspection I was pretty sure that lazy cop wouldnt bend over and look. Phew, was I relieved when he just asked me to rap it a couple of times. I passed, went around the block, and pulled the nails out. I hit the gas and those home made baffles shot out of there like from a cannon. Do you imagine I went and picked them up? NO, I was 17. The point Im getting to is this: while those cardboard plugs were in there, that 340 was a bit of a dog, too. Actually, very doggie.I hammered that plug in there with a wooden stick. Now Im not saying that your exhaust is plugged, just that its something to consider and very easy to check. Carb type fuel pressure testers, and/or old style vacuum guages are callibrated just right.
-Happy hunting
 
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