0-60

[That Ol 720]

I have a 1983 720 2x2 that has a few power issues. I took it out on the highway a while back and tested its speed and all that and my 0-60 time was 23 seconds on flat level ground. I feel like that's pretty bad so I was just wondering what you guys typically get for a 0-60 time.

[captain720]

Which gear were you doing 60 in? 3rd or 4th. 

 

His truck has a really high geared rear diff it seems

[datzenmike]

Assuming 3.889 and 195/75R14s that's 4,000 @ 60 MPH in 3rd.

 

 

I know of no one that does a 0-60 time. 23 seems a bit slow but the Z24 is all about low RPM torque that high revving power.

 

A MPG number might indicate something not right. A 2wd would get 23 MPG give or take on the highway. If getting 15 then something is out of tune.

 

Have you checked things like valve lash, ignition timing, are the plug wires old? have you checked the both exhaust and intake side spark plugs are working? Pull a plug wire off, stick an old plug in the end, lay on a grounded surface, turn engine with starter, is there spark? It's common enough for the exhaust side to quit and engine runs terrible. Spark plugs should only be BPR6ES intake side and BPR5ES exhaust side.

 

Do a compression test. All over 150 wold be alright, under 130 would be getting tired.  All readings should be within 10% of each other. The Z24 is well known for blowing the head gaskets at 100K intervals.... do you have unexplained coolant loss and need to top up the radiator constantly? Are the spark plugs in one cylinder cleaner than the rest?

[captain720]

1 minute ago, datzenmike said:

Assuming 3.889 and 195/75R14s that's 4,000 @ 60 MPH in 3rd.

 

 

I know of no one that does a 0-60 time. 23 seems a bit slow but the Z24 is all about low RPM torque that high revving power.

 

A MPG number might indicate something not right. A 2wd would get 23 MPG give or take on the highway. If getting 15 then something is out of tune.

 

Have you checked things like valve lash, ignition timing, are the plug wires old? have you checked the both exhaust and intake side spark plugs are working? Pull a plug wire off, stick an old plug in the end, lay on a grounded surface, turn engine with starter, is there spark? It's common enough for the exhaust side to quit and engine runs terrible. Spark plugs should only be BPR6ES intake side and BPR5ES exhaust side.

 

Do a compression test. All over 150 wold be alright, under 130 would be getting tired.  All readings should be within 10% of each other. The Z24 is well known for blowing the head gaskets at 100K intervals.... do you have unexplained coolant loss and need to top up the radiator constantly? Are the spark plugs in one cylinder cleaner than the rest?

He has no fuel pressure regulator, his carbs detuned to run with no choke, plug wires mis match. Seems to be overflowing the float bowl sometimes

[Charlie69]

If what captain said above is true fix and tune the truck.  These are not sports cars.

Edited September 30, 2021 by Charlie69

[datzenmike]

I can't remember everything and hate having to go search through old posts to get my answers. 

[That Ol 720]

I did a compression test about a month ago and the cyl 1 was 175, cyl 2 was 163, cyl 3 was 159, cyl 4 was 168

[datzenmike]

A good start. So it's likely a very poor tune. Hows you mileage.

[That Ol 720]

I get like 17-18 in the city and 20 right on the dot on the highway

 

[Veraciousreasoning]

19 hours ago, That Ol 720 said:

I get like 17-18 in the city and 20 right on the dot on the highway

 

 

I got a 1980 720 and I am getting similar mpg. My truck does 0-60 in about 30 seconds. 

[That Ol 720]

19 minutes ago, Veraciousreasoning said:

 

I got a 1980 720 and I am getting similar mpg. My truck does 0-60 in about 30 seconds. 

Does yours ever backfire and stutter when its trying to get up hills? When Im on the highway and going up a hill, it looses 10-15mph and starts backfiring and stuttering like its not getting enough air to too much fuel or something.

[Veraciousreasoning]

1 hour ago, That Ol 720 said:

Does yours ever backfire and stutter when its trying to get up hills? When Im on the highway and going up a hill, it looses 10-15mph and starts backfiring and stuttering like its not getting enough air to too much fuel or something.

 

I def creep up hills with the 720 but I don't really get the stuttering or backfiring. When you drive uphill what gear are you in? I always have to downshift to third gear. 

 

When I see a hill coming usually I just increase my speed as much as possible to get as far up the hill before I have to downshift. 

[That Ol 720]

23 minutes ago, Veraciousreasoning said:

 

I def creep up hills with the 720 but I don't really get the stuttering or backfiring. When you drive uphill what gear are you in? I always have to downshift to third gear. 

 

When I see a hill coming usually I just increase my speed as much as possible to get as far up the hill before I have to downshift. 

When I'm on the highway im typically going 60-65 so i downshift from 5th into 4th to go up hills. But then I just lose my speed

[Veraciousreasoning]

1 hour ago, That Ol 720 said:

When I'm on the highway im typically going 60-65 so i downshift from 5th into 4th to go up hills. But then I just lose my speed

Damn you can get up to 60-65? My truck barely hits 55 miles an hour without it sounding likes its screaming like a banshee. 

[That Ol 720]

23 minutes ago, Veraciousreasoning said:

Damn you can get up to 60-65? My truck barely hits 55 miles an hour without it sounding likes its screaming like a banshee. 

My truck is really wierd. Sometimes I can hit 80 and I don't lose power going up hills at all, and then the next day I won't be able to pass 55mph on level ground and then itll stay like that for a week. Then it will be fine again. I don't know man my truck is weird but it definitely has a power issue, no doubt about that.

[Veraciousreasoning]

1 hour ago, That Ol 720 said:

My truck is really wierd. Sometimes I can hit 80 and I don't lose power going up hills at all, and then the next day I won't be able to pass 55mph on level ground and then itll stay like that for a week. Then it will be fine again. I don't know man my truck is weird but it definitely has a power issue, no doubt about that.

 

Could be a timing issue? or a valve issue? I am stilling learning about cars and got my truck to basically rebuild it so I can learn these things. Have you changed the fuel filter? cleaned your carb?

[That Ol 720]

2 hours ago, Veraciousreasoning said:

 

Could be a timing issue? or a valve issue? I am stilling learning about cars and got my truck to basically rebuild it so I can learn these things. Have you changed the fuel filter? cleaned your carb?

My timing is factory spec 3 BTDC and u replaced the fuel filter about 2 weeks ago. My carb is brand new and was put on when my engine was rebuilt about a year ago. Haven't checked the valves tho. 

[datzenmike]

 Timing is 5 degrees +- 2 degrees so you are on the low side.

 

6 hours ago, That Ol 720 said:

Does yours ever backfire and stutter when its trying to get up hills? When Im on the highway and going up a hill, it looses 10-15mph and starts backfiring and stuttering like its not getting enough air to too much fuel or something.

 

Backfire out the exhaust or the carburetor?  Spark plug wires have no real expiry date. If they look old then they are and need to be replaced. Check the distributor cap insides and the rotor. Under load the spark has a much harder time jumping the plug gap and will look for an easier path to ground. Like a crack in the cap or insulation on the boots or wires. 

 

 

 

5 hours ago, Veraciousreasoning said:

Damn you can get up to 60-65? My truck barely hits 55 miles an hour without it sounding likes its screaming like a banshee. 

 

The 720 is perfectly capable of above highway speeds. It sounds way worse than it is. It's not really revving that much

[That Ol 720]

37 minutes ago, datzenmike said:

 Timing is 5 degrees +- 2 degrees so you are on the low side.

 

 

Backfire out the exhaust or the carburetor?  Spark plug wires have no real expiry date. If they look old then they are and need to be replaced. Check the distributor cap insides and the rotor. Under load the spark has a much harder time jumping the plug gap and will look for an easier path to ground. Like a crack in the cap or insulation on the boots or wires. 

 

 

 

 

The 720 is perfectly capable of above highway speeds. It sounds way worse than it is. It's not really revving that much

I think it might be backfiring put of the carb. I may be wrong tho

[bottomwatcher]

Backfiring is usually a vacuum leak or someone may have a vacuum hose running to the wrong place on the manifold or carb. Is your idle lopey at all?

[captain720]

Yes it is carb backfires like no tomorrow. I think because there's no fuel pressure regulator it may be overflowing the float bowl and dumping too much in on hills

[Lockleaf]

So does it not have the stock fuel Y at the carb?  That is the only regulator these ever had.

 

Also the stutter and loss of power sounds exactly like what happens on mine when my fuel filter needs to be replaced.  Even if you've done that recently it a good cheap place to start.

[captain720]

Yes it has the stock Y, I have found that on some that is good enough but some Weber's on 720s really seem to need a regulator to get down to 2-3 PSI

[datzenmike]

The Y is for the return line not a fuel pressure regulator. The fuel pressure regulator is built into the electric pump

[captain720]

6 minutes ago, datzenmike said:

The Y is for the return line not a fuel pressure regulator. The fuel pressure regulator is built into the electric pump

What about aftermarket or replaced pump?