1978 k30

[Terlingueno]

Another thing besides the timing check would be to check/verify that the carburetor has the correct jets and metering rods. Then tune the carb per the Edelbrock instructions.

https://edelbrock-instructions-v1.s3.amazonaws.com/edelbrock/carb-tuning-guide.pdf

 

[derekhisle]

Another thing besides the timing check would be to check/verify that the carburetor has the correct jets and metering rods. Then tune the carb per the Edelbrock instructions.

https://edelbrock-instructions-v1.s3.amazonaws.com/edelbrock/carb-tuning-guide.pdf

This is my first carbureted engine.So i'm still trying to learn how to tune and adjust carbs

 

[Terlingueno]

This is my first carbureted engine.So i'm still trying to learn how to tune and adjust carbs

The tuning guide I linked will be of help in that quest...

Making sure your ignition timing is correct is critical, as is checking the vacuum advance canister is functioning properly.

 

[derekhisle]

The tuning guide I linked will be of help in that quest...

Thank you

 

[bucket]

@derekhisle I moved this thread to a different section of the forum. Tagged you in it to make sure you still found it.

 

[DoubleDingo]

I don't have a tac turn on my rpm and to be honest, I'm not really sure what all they did to it.
But I do know when it comes to the kickdown. It has only worked twice since i've had it.And that was only during take off to the floor going up a hill

Kick down will not happen above 45 or 50 mph, keep that in mind. My C20 is 350/th400/4.10 and will not kick down at those speeds

 

[derekhisle]

Kick down will not happen above 45 or 50 mph, keep that in mind. My C20 is 350/th400/4.10 and will not kick down at those speeds

The only time the kickdown ever worked was around 20-25 and has only happened twice.

 

[DoubleDingo]

The only time the kickdown ever worked was around 20-25 and has only happened twice.

Sounds right, but you need to diagnose why it's not now

 

[derekhisle]

Sounds right, but you need to diagnose why it's not now

Do you think that since I don't have the electronic choke hooked up Currently that that could cause it?

 

[DoubleDingo]

Do you think that since I don't have the electronic choke hooked up Currently that that could cause it?

Choke doesn't kick down the transmission, but it can limit throttle travel, not allowing the kick down switch to be activated.

 

[Grit dog]

Do you think that since I don't have the electronic choke hooked up Currently that that could cause it?

Totally unrelated. Carb vs transmission.
It’s evident that you haven’t had much time to work on the truck and aren’t that knowledgeable, so let’s start with what we know and the easy stuff.
1. A 7x16 tandem enclosed presumably steel frame lined with (wtf?) 3/4” plywood is probably about 3500lbs empty and it has some wind resistance.
2. Your truck is around 6klbs especially with that big topper on it.
Even with 4.10s and running “fine” it ain’t gonna have much power you can feel.

Next is, is it actually running fine? Given your experience or lack thereof, someone with a bit of knowledge and an ear can help you with the basics. Don’t go fcking around with the carb right now. If it’s a small/mid size Edelbrock and newish, it is probably doing what it’s supposed to and you ain’t gonna unlock that extra 6.9hp today after “tuning” it. Firing on all 8. Timing and advance in line. Not pig rich or detonating.
Now even if it’s “fine” you have no idea what this engine is. Short of figuring that out (which may not be what the castings say anyways), you could easily have a 180hp (new) engine that is happily cranking out say 150hp because it’s old or ….whatever.
Neither one will be great or even good, imo. Although the 4.10s should help, the engine could just be wore out too and 150hp is what it dreams of at night.
Now put that thru 12 ft long of 2 gear boxes and a multi piece driveshaft, spinning or pushing who knows what for rolling resistance while having 2 more axles draggin behind you and a parachute…
As your description of the symptoms is lacking any measurable detail, can’t really help much more than this.
If you can’t describe any more detail at least give top speed empty and towing and how long to get to x speed. At least something measurable and greater detail than “no power over 30mph with a trailer”. That’s quite subjective.
I think my C10 has “no power over 30mph with a trailer” but it’s got 3.07s and about 200hp and my basis for comparison is a 500hp diesel.
Sweet truck though! Must be in pretty decent shape if you’re using it planning on using it for towing!

 

[derekhisle]

Totally unrelated. Carb vs transmission.
It’s evident that you haven’t had much time to work on the truck and aren’t that knowledgeable, so let’s start with what we know and the easy stuff.
1. A 7x16 tandem enclosed presumably steel frame lined with (wtf?) 3/4” plywood is probably about 3500lbs empty and it has some wind resistance.
2. Your truck is around 6klbs especially with that big topper on it.
Even with 4.10s and running “fine” it ain’t gonna have much power you can feel.

Next is, is it actually running fine? Given your experience or lack thereof, someone with a bit of knowledge and an ear can help you with the basics. Don’t go fcking around with the carb right now. If it’s a small/mid size Edelbrock and newish, it is probably doing what it’s supposed to and you ain’t gonna unlock that extra 6.9hp today after “tuning” it. Firing on all 8. Timing and advance in line. Not pig rich or detonating.
Now even if it’s “fine” you have no idea what this engine is. Short of figuring that out (which may not be what the castings say anyways), you could easily have a 180hp (new) engine that is happily cranking out say 150hp because it’s old or ….whatever.
Neither one will be great or even good, imo. Although the 4.10s should help, the engine could just be wore out too and 150hp is what it dreams of at night.
Now put that thru 12 ft long of 2 gear boxes and a multi piece driveshaft, spinning or pushing who knows what for rolling resistance while having 2 more axles draggin behind you and a parachute…
As your description of the symptoms is lacking any measurable detail, can’t really help much more than this.
If you can’t describe any more detail at least give top speed empty and towing and how long to get to x speed. At least something measurable and greater detail than “no power over 30mph with a trailer”. That’s quite subjective.
I think my C10 has “no power over 30mph with a trailer” but it’s got 3.07s and about 200hp and my basis for comparison is a 500hp diesel.
Sweet truck though! Must be in pretty decent shape if you’re using it planning on using it for towing!

I've had the truck up to about 70 before I felt like it was unsafe for the motor check out but once again that is subjective and I do not have a tac and very loud exhaust, so it's hard to truly listen and generally, I would say it takes approximately an eighth of a mile to get up to 60.. Also I looked up the trailer and it weighs approximately 2200 pounds and while hauling the trailer, I could not get above about 35 mph unless going downhill

 

[K20SM465]

First pull the spark plugs and see what they look like, oily(hopefully not), black, gray or brown electrode damage and such. Before you start tinkering with the carb, check for vacuum leaks with a can of carb cleaner. Also buy a vacuum gauge and check the reading off the base plate port of the carb. This will tell you a lot of stuff. Maybe check the modulator valve with the vacuum gauge too. Check the transmission fluid color and level. Just do the basic stuff first. Get a Haynes or chiltons shop manual that covers your truck out will be helpful if you’re not sure on it.

 

[bucket]

...while hauling the trailer, I could not get above about 35 mph unless going downhill

Yeah, there's an issue with something. With that trailer, you will definitely know it's back there, especially with a head wind. But there's no reason it shouldn't be capable of legal road speeds on flat ground.

 

[derekhisle]

First pull the spark plugs and see what they look like, oily(hopefully not), black, gray or brown electrode damage and such. Before you start tinkering with the carb, check for vacuum leaks with a can of carb cleaner. Also buy a vacuum gauge and check the reading off the base plate port of the carb. This will tell you a lot of stuff. Maybe check the modulator valve with the vacuum gauge too. Check the transmission fluid color and level. Just do the basic stuff first. Get a Haynes or chiltons shop manual that covers your truck out will be helpful if you’re not sure on it.

Transmission is good as I thought that might be an issue as well. I ended up changing the fluid and filters on it. Spark plugs are brand new
And I put new vacuum plugs on thinking that might be an issue as well, but I have not checked the base plate with carb cleaner