Want to build a good horsepower, good fuel economy engine for a 1978 c20 with stock 350. I don't know much and need help.

[Ricko1966]

Would the timing have anything to do with the idle? i know when I add throttle just a bit it smooths out so that's why I thought it was the carb, but could it simply be timing?

Absolutely, timing first then carb adjustments. When dialing in performance it's ignition first then carbureation. Carbureator are so over blamed for incorrect timing or curve. Have messed with the timing shortly before your problem?

 

[Quinn_Hanifan]

haven't touched it yet, all ive done for ignition was new cables and plugs. I've double and triple-checked to make sure the firing order is correct.

but I do feel like the engine has always idled relatively rough and could definitely be running better.

 

[Ricko1966]

Does the vacuum advance work? Is it connected to ported vacuum or manifold vacuum? Do you know the difference between the two?

 

[Quinn_Hanifan]

Does the vacuum advance work? Is it connected to ported vacuum or manifold vacuum? Do you know the difference between the two?

i do not, but ill look it up

 

[Ricko1966]

i do not, but ill look it up

One has vacuum at all times,that's manifold vacuum. One has no vacuum at idle,that's ported. If you have your carbureator way out of adjustment though the ported vacuum still has vacuum because you have the throttle hung open a little. Anyway look up qjet vacuum ports drivers side front 5/32 is ported vacuum if your distributor is routed there pull it off and plug the carb port. Hook distributor to manifold vacuum and readjust the carb. Post back findings and results. Also this information is worthless if the vacuum advance is ruptured. The hose that goes to the vacuum advance, suck on it and stick your tongue to the open end if it sticks to your tongue you're good. I'm just assuming you don't have a syringe or mity vac at your disposal.

 

[Quinn_Hanifan]

Alright, i did some research and im pretty darn sure my vacuum lines all have vacuum, and are run to the correct places. i did however discover that the truck only stalls after high rpms. it runs just fine when i havent given any decent gas other than starting, but when i have a prolonged rev, or like a simulated driving experience and even when i let the throttle off nice and slow when doing so it still just dies. not sure if that helps anything but thats what ive discovered.

 

[Quinn_Hanifan]

do i simply just need to adjust fuel/air mix, or specifically idle mixture? kinda like a smaller carb on something like a chainsaw or ATV?

 

[Turbo4whl]

I'm saying the Edelbrock will work better than a worn out carbureator but not as well as the original carbureator. If I just had to stay carbureated, and didn't want a qjet,for whatever reason, I'd go Holley. Why because any monkey with a screw driver and a vacuum gauge can dial in a Holley. ( sorry monkeys )

Well Rick, you are rough on us old monkeys. At least you already apologized for it.

@Paladin Did you read what Rick said about us?

 

[Quinn_Hanifan]

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[82sbshortbed]

Everything looks good to me.

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I don't have any vacume hoses to my water outlet on the intake but, it's not wrong. I just prefer not to have it on my truck.

 

[Quinn_Hanifan]

So i ended up adjusting the idle, about a quarter turn for the choke idle and about a turn and a half for idle. Sounds better idling and doesn't die after revs. I took it around for a quick drive last night and she didn't stall once. it is a little faster when idling in gear but figures if you increase idle, you'll increase idle speed. lol

 

[Quinn_Hanifan]

I drove my truck to school this morning and noticed the brakes were quite spongy until about 75% pressure then they started to kick in. dangerous, I know and I want to get it fixed asap. Is it just air in the hydraulic lines? or is something else wrong?

 

[Rusty Nail]

. i did however discover that the truck only stalls after high rpms.

Be more specific??
Open loop or closed?

This quoted info seems key.
Lookin at you, float level.
So ..the quad leaks?
Internally?

It's 8 pages now Rick..you doin alright buddy?

Your timing isn't set at 0°??

Rick can fix it but I reckon he's gonna need moar coffee I guess.

Prolly gonna have to open it up, the Quad.
I can easily see that you need to change the intake manifold gaskets - they don't last 35 years.
As for the brakes? My money rides on a leaking wheel cylinder. Think real hard about removing the rear wheels for a brake inspection - A.S.A.P.

Safety first kids !

 

[Ricko1966]

You've adjusted the carbureator wrong,get a book. I recommend an old motors manual off ebay. Brakes start a new thread,sorry lots going on can't devote the time to this that you need. If you aren't using a vacuum gauge and mixture screws your doing it wrong,and set the timing first,vac advance disconnected and plugged reattach to manifold vacuum before you adjust the carbureator.

 

[Rusty Nail]

Alright alright!
That's enough horseplay, get back to work.