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Old 07-10-2018, 11:32 AM   #1
jopaul
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'70 K20 carb options

I bought a decent '70 K20 a few weeks back, and love it!
I think it's been lifted 4", but not really sure.
It starts and runs great when the temp outside is 60 or so, warmer and the truck runs like crap, sounds like it's going to stall.

I do not know anything about carbs except that they feed the engine the golden liquid and make it go vroom. Ok, I exaggerate....a bit.
The carb is a Holley 2 barrel, not sure of much more than that at the moment.

My question(s) are:

1) I want EFI but keep things simple. I have been looking at this https://www.holley.com/brands/holley...per_2300_2bbl/
Would that fit with the same intake manifold I have (Holley is all it says on it)?
2) Has anyone swapped out a carb for one of these and does it help with the weird running during warmer temps?
3) Is there another option for EFI and keeping it simple?

I do not know much about the engine either, like I said I just purchased it and want to use it as a daily. I came here to learn more about my truck, :-D . So first thing to fix is how it runs.

Thanks in advance for any and all helpful info.
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Old 07-10-2018, 10:44 PM   #2
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Re: '70 K20 carb options

I 'think' that system only bolts to a Ford intake pattern. The four barrel version is not that much more $$$. I would just call the Holley tech line and ask them what system would be best for your application.
FiTech is another option. Search this board. I've seen several threads on both the Holley and the fitech installs.
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Old 07-10-2018, 11:11 PM   #3
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Re: '70 K20 carb options

Quote:
Originally Posted by Acorn View Post
I 'think' that system only bolts to a Ford intake pattern. The four barrel version is not that much more $$$. I would just call the Holley tech line and ask them what system would be best for your application.
FiTech is another option. Search this board. I've seen several threads on both the Holley and the fitech installs.
Yes I saw the FiTech, it seems very similar. The Holley Sniper does come with different mounting plates so I think they're might be a fit for my truck.

I'll search the forum and take a peek, but still open to others opinions and expertise.
Thank you Acorn.
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Old 07-11-2018, 07:18 PM   #4
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Re: '70 K20 carb options

Well, jopaul, what is your budget?

You are looking for a DD. What do you know about your engine? Is it stock compression, stock cam and heads?

An easy slight HP gain for it would be an aftermarket 180 dual-plane intake manifold (we use a Weiand Street Warrior 8120 WND) and we chose a Holley 650 double-pump carb with mechanical secondaries (because we have a manual transmission) HLY-0-4777S. The carb is a bit large for a stock cam, so you could go to a 500 or 600 CFM carb if you choose.

These should all be bolt-on improvements. We bought through Summit Racing.
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Old 07-11-2018, 07:31 PM   #5
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Re: '70 K20 carb options

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Originally Posted by BILT4ME View Post
Well, jopaul, what is your budget?

You are looking for a DD. What do you know about your engine? Is it stock compression, stock cam and heads?

An easy slight HP gain for it would be an aftermarket 180 dual-plane intake manifold (we use a Weiand Street Warrior 8120 WND) and we chose a Holley 650 double-pump carb with mechanical secondaries (because we have a manual transmission) HLY-0-4777S. The carb is a bit large for a stock cam, so you could go to a 500 or 600 CFM carb if you choose.

These should all be bolt-on improvements. We bought through Summit Racing.
budget? ha! just kidding. just freed up some extra $$ a month, paid my last child support payment ;-)

and I think I have changed my mind about carbs. I mean I still needs something now and going to research my options with a rebuilt one that matches what is on there now.
I don't know much about the engine. It appears to be a 350, but it's definitely not the engine that truck rolled out of the factory with. There's no papers etc...so it's best guess. And to fix that I am looking at Jegs for the Vortec 350 5.7l or some other LSX (was thinking the 6.0, LQ9) but seeing how those cost more than I want to spend right now....the Jegs route is probably within my "budget".

What I want to do with the truck is make lots of horsepower mostly because I want to cruise up a mountain pass with a decent size camper on it (thinking 5th wheel).

Still learning about the engine types, internals, and of course the truck itself.
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Old 07-11-2018, 07:52 PM   #6
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Re: '70 K20 carb options

Look on the left rear of the block for a casting number. This is where the transmission bell housing bolt to the block.

That will tell you the basics of the engine.

If we were to do it again, we would buy the Sniper EFI and pony up the cash for it, as there are fewer issue to go wrong. Yes, there is a learning curve for it, but it works.
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Old 07-11-2018, 10:01 PM   #7
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Re: '70 K20 carb options

Well, since you don't know anything about the engine, the first thing you need to do is check your timing. Incorrect timing often disguises itself as carburetor problems. You'll want to set the intial timing at 12 to 14 degrees advanced. Do you know what type of distributor you have, original points or HEI?
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Old 07-12-2018, 07:30 AM   #8
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Re: '70 K20 carb options

I don't have EFI, I have a totally reliable runs like a raped ape factory Quadrajet carb that was rebuilt to original specs. The carb (or EFI) is the crown jewel to sit atop a healthy engine to give it optimum fuel delivery on demand. Get to know your engine before changing jewels.
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Old 07-12-2018, 10:12 AM   #9
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Re: '70 K20 carb options

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Originally Posted by 68 P.O.S. View Post
Well, since you don't know anything about the engine, the first thing you need to do is check your timing. Incorrect timing often disguises itself as carburetor problems. You'll want to set the intial timing at 12 to 14 degrees advanced. Do you know what type of distributor you have, original points or HEI?
I have HEI mod. The guy I bought it from explained that it is set weird for some reason, he didn't go into details. I'll have to ask him about it specifically.

Thing is, when it's cool outside (well, here in Washington, 50 degrees with sun is a nice day) like around 60 degrees, it turns over and runs like a champ. A little high RPM's (I dunno if 1k RPM's is good, to me it seems high) but drives just fine. When it's warmer....it takes a few clicks of the key to get it staying running and the RPM's go low to 800 and seems like it wants to stall when I'm at a stop.
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Old 07-12-2018, 10:15 AM   #10
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Re: '70 K20 carb options

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Originally Posted by special-K View Post
I don't have EFI, I have a totally reliable runs like a raped ape factory Quadrajet carb that was rebuilt to original specs. The carb (or EFI) is the crown jewel to sit atop a healthy engine to give it optimum fuel delivery on demand. Get to know your engine before changing jewels.
I get that, and that's why I think I am just gonna save my pennies for a new motor that was built and comes with EFI to drop in there. I do not know what has been done to the engine or if it's a true 350.
I mean almost a grand for the Sniper, which sounds like an awesome "jewel" to sit atop the engine, I can use that money to get a decent LSX and hopefully the extras.
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Old 07-12-2018, 10:18 AM   #11
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Re: '70 K20 carb options

Quote:
Originally Posted by BILT4ME View Post
Look on the left rear of the block for a casting number. This is where the transmission bell housing bolt to the block.

That will tell you the basics of the engine.

If we were to do it again, we would buy the Sniper EFI and pony up the cash for it, as there are fewer issue to go wrong. Yes, there is a learning curve for it, but it works.
I will have to wait to get this. It's leaking oil out the backside of the intake and I have the gasket, the thermostat gasket, and coolant to replace when I take it off and fix the leak. That's when I can get the number.

Any tips or things to look out for when replacing the intake manifold gasket?
I don't want to deal with a nightmare on the timing, which I've heard people getting themselves into when replacing anything with the intake mani.
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Old 07-12-2018, 11:39 AM   #12
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Re: '70 K20 carb options

Quote:
Originally Posted by jopaul View Post
I have HEI mod. The guy I bought it from explained that it is set weird for some reason, he didn't go into details. I'll have to ask him about it specifically.

Thing is, when it's cool outside (well, here in Washington, 50 degrees with sun is a nice day) like around 60 degrees, it turns over and runs like a champ. A little high RPM's (I dunno if 1k RPM's is good, to me it seems high) but drives just fine. When it's warmer....it takes a few clicks of the key to get it staying running and the RPM's go low to 800 and seems like it wants to stall when I'm at a stop.
Its good you have an HEI. Its a great upgrade. Let us know what's weird about your HEI when you find out and we can help you sort it out.

If your truck is an automatic, your idle speed should be 600 rpm while in gear with your foot on the brake. In park you're looking at 750 to 800 rpm, no more than that.

Regardless of if you stay with a carb or go efi, its a great idea to replace your intake with a better unit. I personally recommend the Edelbrock EPS or RPM. And you should not have any timing issues related to replacing the intake.
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Old 07-12-2018, 12:16 PM   #13
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Re: '70 K20 carb options

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Originally Posted by 68 P.O.S. View Post
Its good you have an HEI. Its a great upgrade. Let us know what's weird about your HEI when you find out and we can help you sort it out.

If your truck is an automatic, your idle speed should be 600 rpm while in gear with your foot on the brake. In park you're looking at 750 to 800 rpm, no more than that.

Regardless of if you stay with a carb or go efi, its a great idea to replace your intake with a better unit. I personally recommend the Edelbrock EPS or RPM. And you should not have any timing issues related to replacing the intake.
The transmission is standard, old school. L-1-2-3-R.
So on the warm days when it runs crappy, it feels like it chugs until steady pressure on the pedal, and when in neutral at a stop it drops to the 800 RPM range and feels like it's gonna die.

On the good cooler days, it sits at 1K RPM's, unless I am driving for a decent distance, then it jumps to 1500 RPM's or a bit higher closer to 2K and if I hit the pedal it drops but not quite back down to 1K RPM's.

Not sure if the electric choke is borked which might be part of the problem.
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Old 07-12-2018, 12:25 PM   #14
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Re: '70 K20 carb options

Does the choke open fully when the truck is at operating temp?
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Old 07-12-2018, 12:47 PM   #15
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Re: '70 K20 carb options

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Does the choke open fully when the truck is at operating temp?
Not sure as I haven't really taken it for long rides. It spits oil out the back of the intake like a stuck oil pig currently and the dipstick is too short when supposedly it's full of oil....
This weekend I plan on re-using the current intake mani (EdelBrock, in another post somewhere's I mistook it for a Holley intake), however I do have an EdelBrock Performer (or Performance) intake that I thought about using, but when buying the gasket the guy mentioned ports and matching them etc...
So will stick with what's already there and "working".
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Old 07-12-2018, 01:07 PM   #16
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Re: '70 K20 carb options

Check the source of the oil leak at the back of the intake manifold. I had a 1970 350 4 bolt main that had a leak that came from one of the casting holes for the intake manifold gasket. When running, the oil would pump out of the second hole from the left on the rear intake manifold gasket where the intake meets the block by the distributor.

I had to drill and tap the hole and insert an Allen head plug with pipe sealant on it to stop the oil leak. It was essentially a casting problem with the block. I still ran that block 100K miles, so it was not a problem.

First, use a mirror and flashlight to locate the leak while running. If you see it at the seam of the intake, pull the distributor and intake manifold.

Then use an oil pump driver and a drill to pump the oil to see where the leak is coming from. it may take a minute or two of "priming" to locate the source of the leak.
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Old 07-12-2018, 01:16 PM   #17
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Re: '70 K20 carb options

Use ultra grey permatex sealant or similar on the front and back of the intake
Do not use the front and back gaskets. They very often leak
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Old 07-12-2018, 01:43 PM   #18
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Re: '70 K20 carb options

Quote:
Originally Posted by BILT4ME View Post
Check the source of the oil leak at the back of the intake manifold. I had a 1970 350 4 bolt main that had a leak that came from one of the casting holes for the intake manifold gasket. When running, the oil would pump out of the second hole from the left on the rear intake manifold gasket where the intake meets the block by the distributor.

I had to drill and tap the hole and insert an Allen head plug with pipe sealant on it to stop the oil leak. It was essentially a casting problem with the block. I still ran that block 100K miles, so it was not a problem.

First, use a mirror and flashlight to locate the leak while running. If you see it at the seam of the intake, pull the distributor and intake manifold.

Then use an oil pump driver and a drill to pump the oil to see where the leak is coming from. it may take a minute or two of "priming" to locate the source of the leak.
The guy i bought it from said he screwed up the sealant dam for the back part of the intake and just never got around to fixing it, so I am taking him at his word on this. We will see what it looks like when I get in there this weekend.
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Old 07-12-2018, 01:44 PM   #19
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Re: '70 K20 carb options

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Use ultra grey permatex sealant or similar on the front and back of the intake
Do not use the front and back gaskets. They very often leak
Very good point, the gasket set came with the front/back gaskets and I was tempted to try using them with Black Permatex gasket sealant.
Is there a difference in the Black vs Grey?
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Old 07-12-2018, 01:51 PM   #20
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Re: '70 K20 carb options

If you want a reliable and imho affordable efi system look at affordable-fuel-injection.com. You can get a complete system, including the distributor. Very user friendly and easy to install. I have installed 2 and I am very pleased.
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Old 07-12-2018, 02:17 PM   #21
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Re: '70 K20 carb options

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If you want a reliable and imho affordable efi system look at affordable-fuel-injection.com. You can get a complete system, including the distributor. Very user friendly and easy to install. I have installed 2 and I am very pleased.
The options I found there are around the same price as the FiTech or Holley options...

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Old 07-13-2018, 03:14 PM   #22
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Re: '70 K20 carb options

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Very good point, the gasket set came with the front/back gaskets and I was tempted to try using them with Black Permatex gasket sealant.
Is there a difference in the Black vs Grey?
Very similar I think. Either should work.
Don't use the gasket!
Just 1/4" bead of sealant front and back.
Google it. A lot of info on what you shouldnt used the gaskets front and back
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Old 07-14-2018, 03:49 PM   #23
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Re: '70 K20 carb options

OK, got the carb off. It's a Carter AFB Competition series 9635SA. From what I'm reading these are either really good or really bad.
Also, it seems to be leaking in the back from the riser plate. Which is plastic and one of the back bolt holes is broken. Probably why the gasket under that is soaked and looks like it's gonna fall apart.

So, where can I get a new riser this weekend? O'Reilly's? Same with gaskets?

Should I get a different carb?

About to take off the intake after making some labels for the distributer and plug wires.
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Old 07-14-2018, 03:55 PM   #24
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Re: '70 K20 carb options

Pictures, if they can be uploaded from my phone
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Old 07-14-2018, 06:36 PM   #25
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Re: '70 K20 carb options

OK intake manifold off. Tried not to turn the distributer, even taped it in position.
However, the oil pressure gauge line broke. It also looks like that might have been part of the leak back there.

Unfortunately I can not get a good look at the back of the block to get numbers. It's too cramped and caked with oil sludge.
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