100+ Mph bog down

[Davea Lux]

Sheesh! I didn’t realize I was gonna have judgement passed on me from everyone for a simple question! Trust me, folks. I don’t regularly do over 100 in my Fury. I treasure my car too much to run it into the ground. Quite honestly, I’m usually right on the speed limit because I have no cruise control and have to watch my speeds manually. Nevertheless, I do want to know what my vehicle’s limitations are and the last time I drove at these speeds was about a year ago and I had it around 110 (if the speedometer can be relied upon) without the hesitation I recently encountered. I’m just looking for non-judgemental advice so I can ensure my ride continues to run tip-top.

I would not lose any sleep, a lot of folks wish they lived some place where they could still get away with those speeds. In Oregon, if you get caught above 100mph it is an automatic 6 month suspension and the car is subject to forfeit for a second offense. Times have changed since my mis-spent youth.

Dave

 

[Daniel Romero]

I would also check the pickup screen on the sending unit if the problem persists after changing the fuel filter. Could also have a fuel pump drive rod that is "short".

Dave

I appreciate the suggestion, Dave. I replaced the fuel filter about a year and a half ago but I’m going to again just to rule that out. Fuel lines haven’t been cleaned out yet.

 

[PontiacJim]

Assume a 360CI? Did not see any engine stats on your profile. Had my '73 360CI 2 Bbl carb pushing 100mph zipping along with some traffic and had no issues, but did not press my luck past 100.

As previously stated it sounds like a fuel issue. Could be as simple as a dirty air cleaner. I turned my air cleaner lid upside down to expose more outside area versus just the snorkel on the air cleaner housing.

If you still have the old/original rubber hoses, could have a small split somewhere and it could be sucking air as the fuel pump is really drawing some fuel at higher RPM's. ALL old/original hose should be replaced with ethanol friendly hose. Nothing worse than one of the old ones splitting and dumping out gas and setting your car on fire - it happens.

Check to make sure no metal lines may have been damaged/crimped preventing the needed fuel at higher RPM's to be starved.

Make sure the gas tank is vented properly. This comes up on GM cars where some of the early 60's cars had vented gas caps and then because gas sloshes out at hard throttle launches with a full tank, they install a non-vented cap so the gas doesn't spill and this creates enough vacuum in the gas tank as the fuel pump sucks on the tank and reaches a point where gas cannot be drawn from the tank. Twist the gas cap off and you hear a sucking or rushing-in-of-air sound and the car runs great until it once again creates that vacuum in the gas tank.

Fuel filter, good tune-up, and check the timing. I believe off the top of my head the '73 was 0 degrees @ TDC. I bumped mine up a little. I think 5-7 BTDC is a little better - as long as you get no engine rattle/pinging which is detonation and can destroy an engine.

Next, after all that, would be a fuel pump.

Don't know how many RPM's the engine is spinning at 105, but my 360 does indeed run out of breath with the stock cam as you get into the upper RPM's. It falls off flat as you described even though I have more pedal to go when I wind it out in 1st & 2nd gear. I don't have a tach either, but feels maybe in the 4800-5000 RPM range as the engine isn't really winding tight in my opinion.

Could also be a single exhaust system choking the engine. A restrictive exhaust won't allow the engine to breathe and will kill power. My car has had duals fitted so it is not an issue.

Keep in mind that the car has a large frontal area and as speeds get higher, you are plowing more air and that uses up a lot of HP to overcome.

 

[Daniel Romero]

Assume a 360CI? Did not see any engine stats on your profile. Had my '73 360CI 2 Bbl carb pushing 100mph zipping along with some traffic and had no issues, but did not press my luck past 100.

As previously stated it sounds like a fuel issue. Could be as simple as a dirty air cleaner. I turned my air cleaner lid upside down to expose more outside area versus just the snorkel on the air cleaner housing.

If you still have the old/original rubber hoses, could have a small split somewhere and it could be sucking air as the fuel pump is really drawing some fuel at higher RPM's. ALL old/original hose should be replaced with ethanol friendly hose. Nothing worse than one of the old ones splitting and dumping out gas and setting your car on fire - it happens.

Check to make sure no metal lines may have been damaged/crimped preventing the needed fuel at higher RPM's to be starved.

Make sure the gas tank is vented properly. This comes up on GM cars where some of the early 60's cars had vented gas caps and then because gas sloshes out at hard throttle launches with a full tank, they install a non-vented cap so the gas doesn't spill and this creates enough vacuum in the gas tank as the fuel pump sucks on the tank and reaches a point where gas cannot be drawn from the tank. Twist the gas cap off and you hear a sucking or rushing-in-of-air sound and the car runs great until it once again creates that vacuum in the gas tank.

Fuel filter, good tune-up, and check the timing. I believe off the top of my head the '73 was 0 degrees @ TDC. I bumped mine up a little. I think 5-7 BTDC is a little better - as long as you get no engine rattle/pinging which is detonation and can destroy an engine.

Next, after all that, would be a fuel pump.

Don't know how many RPM's the engine is spinning at 105, but my 360 does indeed run out of breath with the stock cam as you get into the upper RPM's. It falls off flat as you described even though I have more pedal to go when I wind it out in 1st & 2nd gear. I don't have a tach either, but feels maybe in the 4800-5000 RPM range as the engine isn't really winding tight in my opinion.

Could also be a single exhaust system choking the engine. A restrictive exhaust won't allow the engine to breathe and will kill power. My car has had duals fitted so it is not an issue.

Keep in mind that the car has a large frontal area and as speeds get higher, you are plowing more air and that uses up a lot of HP to overcome.

Thanks for your reply, Jim. I appreciate you taking the time. I have a 1973 Fury with a 400 and a factory two-barrel carburetor.

 

[Carmine]

Sheesh! I didn’t realize I was gonna have judgement passed on me from everyone for a simple question! Trust me, folks. I don’t regularly do over 100 in my Fury. I treasure my car too much to run it into the ground. Quite honestly, I’m usually right on the speed limit because I have no cruise control and have to watch my speeds manually. Nevertheless, I do want to know what my vehicle’s limitations are and the last time I drove at these speeds was about a year ago and I had it around 110 (if the speedometer can be relied upon) without the hesitation I recently encountered. I’m just looking for non-judgemental advice so I can ensure my ride continues to run tip-top.

You got a bunch of good, free advice and now you're boo-hoo'ing? Keep looking for the source of excess fuel.

 

[Davea Lux]

Thanks for your reply, Jim. I appreciate you taking the time. I have a 1973 Fury with a 400 and a factory two-barrel carburetor.

Since this is a 2BBL car, when you rebuild the carb, check the float adjustment, it could also be leaning out at higher rpms due to the floats being set too low. If it was smoking (black smoke) at high rpms, mixture is too rich. If it lost power and started popping and farting, you have a too lean mixture or a fuel supply issue.

Dave

 

[Davea Lux]

Some other high rpm issues, check you air filter to be sure you do not have a critter nest obstructing proper air flow. Next check your point setting. If they are set wide, as the engine increases rpms, the points may not make good contact and a high rpm misfire can happen.

Dave

 

[65Fury440]

This does beg the question, does the OP hold the land speed record for C Body forum members?

Check this guy out. He even has time to shoot some video.

 

[Turboomni]

Why go that fast in a car that doesn't handle worth beans?

 

[TomTom]

I'd check fuel tank screen, fuel filter, fuel pump. Filter first. With my 6-pack car it would also lose out when wide open throttle. I wound up adding an electric pump just as the fuel line left the tank, and used the largest fuel filter I could but before it. Plus I had already replaced the high volume fuel pump. I also ran a "curse word" Chevy 454 occasionally on propane instead of gasoline since propane was cheaper fuel. The fuel came out of the tank, using liquid, that it would shut the safety valves in the tank outlets, until the pressure had equalized. This was a safety feature in the case of a line rupture. Also be sure that your tank is venting properly, not operating under negative pressure.

 

[LeBaron1973]

Because he can I guess. Just wants to know his top speed. Police will get him as they just have to wait for the next fuel stop.

Not a criticism, just recall police tailing a Ferrari I think. "He'll have to stop for gas soon" said the sheriff and sure enough, so it happened.

Best wishes to Daniel for happy motoring.

 

[Factorial]

Check this guy out. He even has time to shoot some video.

Until I see otherwise, we have a winner.

 

[commando1]

Why go that fast in a car that doesn't handle worth beans?

BINGO.
I'm a 65-80 mph guy in my 76 NYB.
Engine runs like a sewing machine and suspension 100% new.
I had to pass a truck on a 2 lane road. I needed to put my foot into it to the max.
As I got up to 100 sailing by him in the oncoming lane, the car was almost uncontrollable.
That's all Im gonna say, now.

 

[73 T&C]

I think about tires blowing at above rated speeds. Especially at steady state speeds that are way over the rated speed rating.

Suspension, and flex is also a big issue.

These old “C” bodies can cruise all day with pretty good manners at up to 90mph in my experience. And they typically top out at somewhere around 105-110moh in good tune and repair. ( this I know). Anything more than 90mph, on a stock set up and tires, requires very careful driver attention and is just not at all comfortable. Driving these barges much over 100 is also really asking for it. IMO.

If you want to go really fast, buy or build a car that will handle it (as the guy in video obviously did) and is rated or limited to a specific max. Life and the scenery can both moves real fast at 150mph.

 

[SPF Required]

... I’m just looking for non-judgemental advice...

 

[Turboomni]

Get something more modern to go fast. I had a 1997 Lexus LS400. A 4.7 32 valve dual overhead cam v8. Computer governed to a top speed of 150 mph. It was made to compete with the top of the line S class Mercedes . It had the lowest drag CF of any production car that year except for the same year new Corvette. 100 mph was easy,,it was cruising. It even had shock absorbers under the front seats.
Most comfortable car I have ever had. Everything worked. The quality of this car was overall the best I have ever known. An old Chrysler,,,good grief,,,stay safe.

 

[commando1]

Best driven locally on warm nights. Nothing modern can compare.

 

[Carmine]

A lot of old fartitude is showing here and/or east coastiness. On clogged up, falling apart expressways, 100 per is crazy in just about anything.

Out west, where the roads are like pool tables, visibility is measured in miles and populations are sparse, 100 is not at all uncommon. I spent much of a trip from LV to PHX at that speed in a '73 Imperial (on new 17", 60 series Michelins).

I bet this post will make Dave want to move.

 

[70bigblockdodge]

As I got up to 100 sailing by him in the oncoming lane, the car was almost uncontrollable

You need a proper alignment not stock specs, in a range.

Get something more modern to go fast. I had a 1997 Lexus LS400. A 4.7 32 valve dual overhead cam v8

Nonsense, yes new cars are more efficient. Make yours more efficient and it will easily do the same, not just it runs good enough for me.

It even had shock absorbers under the front seats

Now your getting sucked in by gimmicks. Do you have a old lady ***? Why would that be appealing to be more detached from driving. BTW my Peterbilt has a shock on its seat but the bag.is deflated and shock does nothing, rides about the same except for being in sync with the truck not out of sync.
You guys need to fix your old rides to work properly, not tell others to slow down. After all you have one of the best designed front suspension and steering systems in the world. If your car is not stable at 100 mph you've got something wrong, go fix it.

 

[commando1]

. I spent much of a trip from LV to PHX at that speed

I no doubt you did.
But let's talk in %ages.
How mamy people get to do that.
How many times.
How often.
Blah, blah blah.
If you bought a Hellcat today, out of the total hours behind the wheel you would rack over the next year, how many minutes total would you be around the 100mph zone.
Two C6 Vettes later, I learned extremely costly truth.