Carb'ed vortec looking for info and opinions

[Frankenchevy]

A lot to read here. One tidbit I don’t believe anyone addressed was the flex plate. Your 2-piece RMS fp from your 84 won’t work on a 1-piece RMS vortec as far as I know.

 

[SquareRoot]

I had cold start issues. That was "one" of my complaints with it. Here is S. Arizona cold is 45-50 degrees. It wasn't just on the initial startup after sitting overnight. If it was parked and allowed to cool down, it was back to square one. It was very much like driving with a clogged fuel filter. To make it worse I was using the Edelbrock Vortec manifold that costs like $275. It was supposed to be better by having the waffle pattern in the plenum and keeping the fuel from puddling.

In hindsight, I would have bought an Edelbrock package. Aluminum heads that flow better, make more power, with a matched intake and carb. But....I can never go back to a carb. That ship has sailed along with drum brakes and manual steering.

 

[SquareRoot]

A lot to read here. One tidbit I don’t believe anyone addressed was the flex plate. Your 2-piece RMS fp from your 84 won’t work on a 1-piece RMS vortec as far as I know.

Correct. I had to pony up for a new flywheel for that reason as you know.

 

[SquareRoot]

And the infamous bypass hose.

 

[DoubleDingo]

@Frankenchevy True, I didn't think of that. Mine was swapping over the heads and intake. But buying a vortec engine, one would need the corresponding new flexplate for automatic or flywheel for a manual.

 

[SirRobyn0]

A lot to read here. One tidbit I don’t believe anyone addressed was the flex plate. Your 2-piece RMS fp from your 84 won’t work on a 1-piece RMS vortec as far as I know.

Thanks, I did read about that somewhere else so was vaguely aware of it, and was going to ask here about it, but got kind of distracted with the cold run thing, so I appreciate the mention of it. If I decide to do a vortec I'll add it to the parts list.

I had cold start issues. That was "one" of my complaints with it. Here is S. Arizona cold is 45-50 degrees. It wasn't just on the initial startup after sitting overnight. If it was parked and allowed to cool down, it was back to square one. It was very much like driving with a clogged fuel filter. To make it worse I was using the Edelbrock Vortec manifold that costs like $275. It was supposed to be better by having the waffle pattern in the plenum and keeping the fuel from puddling.

In hindsight, I would have bought an Edelbrock package. Aluminum heads that flow better, make more power, with a matched intake and carb. But....I can never go back to a carb. That ship has sailed along with drum brakes and manual steering.

So at this point I've done a ton of reading about the cold run issues with the carbed vortec, and one thing that is somewhat confusing to me, is some folks like you found major issues, at 45F while others say there are are only minor issues or no issues at all between when the choke goes off and fun warm and only when it's more like near freezing.

Something doesn't jive here for me and I'm quite sure what it is, I wish I knew someone with a carbed vortec nearby that would let me cruise their truck for like a week lol.

Of course there are plenty of various carb options and cams run all of which might effect performance, so perhaps the answer is it'll depend on specifics.

I do want to ask you. Edelbrock makes 2 manifolds for the carbed vortec, was that the one with the plumbing for coolant under the manifold that you were running, and were you running a factory style air cleaner with a thermac? Thanks.

 

[DoubleDingo]

I run a quadrajet, and it gets between the 40's and the 20's here during the winter. I have only seen it in the 20's in 2005, but it can happen. Usually in the 40's to high 30's, and the engine will spit and sputter until it gets warm. I cannot speak to what a holley or edelbrock or other fuel delivery system will do, but my particular quadrajet works fine once warm or when up to speed on the road.

Side story about that colder winter in 2005: I kept a hummingbird feeder out just in case there were any that didn't fly south for the winter, and sure enough I had a couple that came in for some nectar. I later learned they can survive subzero temps, tough little birds!

 

[77 K20]

I just saw this thread. From all my reading and experience is:

-vortec engines were a dry manifold from the factory. No air/fuel mixture is flowing thru the manifold. It is delivered right at the valves (multi-port injection). This provides the most power and eliminates cold weather issues.
-With a carb or with TBI having a waffle pattern or "speed bump" pattern is a good thing to have on the manifold plenum floor. This isn't as good for performance, but will help get the fuel that drops out of suspension and puddles back up into the air and delivered to a cylinder.
-Different engines will run different when it is cold due to vacuum. As pressure goes down temperature goes down.
-even after adding alumniseal it still used coolant (on the porous edelbrock manifold with coolant bypass). Not as much... but still. I dropped the radiator cap pressure down to 8? psi? Now doesn't use a drop. Not correct, but it was all I could do.
-I have a 1 minute drive and then it is all highway. When it was cold (lets say 20 and below) the intake manifold would not warm up on the highway. At almost 3,000 RPM it is sucking in a lot of cold air. This kept the manifold from getting warm (this was on the stock GM performance manifold with no coolant crossover). I could drive for 30 minutes and at the first stop it would run like crap.

Now if you could somehow get the exhaust crossover to work when it was cold, then shut it off once it warms up or in the summer that would be great...

I'm still saving up for a multi port injection.

 

[DoubleDingo]

I just saw this thread. From all my reading and experience is:

-vortec engines were a dry manifold from the factory. No air/fuel mixture is flowing thru the manifold. It is delivered right at the valves (multi-port injection). This provides the most power and eliminates cold weather issues.
-With a carb or with TBI having a waffle pattern or "speed bump" pattern is a good thing to have on the manifold plenum floor. This isn't as good for performance, but will help get the fuel that drops out of suspension and puddles back up into the air and delivered to a cylinder.
-Different engines will run different when it is cold due to vacuum. As pressure goes down temperature goes down.
-even after adding alumniseal it still used coolant (on the porous edelbrock manifold with coolant bypass). Not as much... but still. I dropped the radiator cap pressure down to 8? psi? Now doesn't use a drop. Not correct, but it was all I could do.
-I have a 1 minute drive and then it is all highway. When it was cold (lets say 20 and below) the intake manifold would not warm up on the highway. At almost 3,000 RPM it is sucking in a lot of cold air. This kept the manifold from getting warm (this was on the stock GM performance manifold with no coolant crossover). I could drive for 30 minutes and at the first stop it would run like crap.

Now if you could somehow get the exhaust crossover to work when it was cold, then shut it off once it warms up or in the summer that would be great...

I'm still saving up for a multi port injection.

Thanks for chiming in, I knew you had issues, but couldn't remember your screen name to tag you.

 

[SquareRoot]

Thanks, I did read about that somewhere else so was vaguely aware of it, and was going to ask here about it, but got kind of distracted with the cold run thing, so I appreciate the mention of it. If I decide to do a vortec I'll add it to the parts list.

So at this point I've done a ton of reading about the cold run issues with the carbed vortec, and one thing that is somewhat confusing to me, is some folks like you found major issues, at 45F while others say there are are only minor issues or no issues at all between when the choke goes off and fun warm and only when it's more like near freezing.

Something doesn't jive here for me and I'm quite sure what it is, I wish I knew someone with a carbed vortec nearby that would let me cruise their truck for like a week lol.

Of course there are plenty of various carb options and cams run all of which might effect performance, so perhaps the answer is it'll depend on specifics.

I do want to ask you. Edelbrock makes 2 manifolds for the carbed vortec, was that the one with the plumbing for coolant under the manifold that you were running, and were you running a factory style air cleaner with a thermac? Thanks.

The manifold did not have plumbing under the carb. That kind of defeats the whole purpose of a dry manifold. Yes, it may be hit or miss but why on earth would you go down the path of "hit or miss" with all these issues if your starting from scratch? There are better options and you don't have to deal with it. I was using a 1406 Edelbrock carb fwiw.

 

[SirRobyn0]

I just saw this thread. From all my reading and experience is:

-vortec engines were a dry manifold from the factory. No air/fuel mixture is flowing thru the manifold. It is delivered right at the valves (multi-port injection). This provides the most power and eliminates cold weather issues.
-With a carb or with TBI having a waffle pattern or "speed bump" pattern is a good thing to have on the manifold plenum floor. This isn't as good for performance, but will help get the fuel that drops out of suspension and puddles back up into the air and delivered to a cylinder.
-Different engines will run different when it is cold due to vacuum. As pressure goes down temperature goes down.
-even after adding alumniseal it still used coolant (on the porous edelbrock manifold with coolant bypass). Not as much... but still. I dropped the radiator cap pressure down to 8? psi? Now doesn't use a drop. Not correct, but it was all I could do.
-I have a 1 minute drive and then it is all highway. When it was cold (lets say 20 and below) the intake manifold would not warm up on the highway. At almost 3,000 RPM it is sucking in a lot of cold air. This kept the manifold from getting warm (this was on the stock GM performance manifold with no coolant crossover). I could drive for 30 minutes and at the first stop it would run like crap.

Now if you could somehow get the exhaust crossover to work when it was cold, then shut it off once it warms up or in the summer that would be great...

I'm still saving up for a multi port injection.

I did some searches last night and read up on some of your threads. Are you running a thermac? Not sure that would be enough heat at 3K but just wondering.

The manifold did not have plumbing under the carb. That kind of defeats the whole purpose of a dry manifold. Yes, it may be hit or miss but why on earth would you go down the path of "hit or miss" with all these issues if your starting from scratch? There are better options and you don't have to deal with it. I was using a 1406 Edelbrock carb fwiw.

Thanks for the info. Part of it is I'm genuinely curious even if I decide not to go this route.

 

[Turbo4whl]

Something to consider, when the stock exhaust manifolds are removed to install headers, the heat riser valve goes away too. This decreases the exhaust heat that normally is forced through the manifold. The stock intake manifold saving grace is the fact it is cast iron.

As you know steel and aluminum transfer heat differently. The aluminum takes on the heat quickly, but it also transfers the heat quickly. This was was proven by @77 K20 's highway running in the cold weather.

I also know as you stated, an air cleaner with the hot air stove makes a big difference in cold weather running. Using the heated air cleaner with a cast iron intake manifold you will have a better cold weather running engine.

Someone talked about modifying an older cast manifold to use on the vortec heads....?

 

[SirRobyn0]

Something to consider, when the stock exhaust manifolds are removed to install headers, the heat riser valve goes away too. This decreases the exhaust heat that normally is forced through the manifold. The stock intake manifold saving grace is the fact it is cast iron.

As you know steel and aluminum transfer heat differently. The aluminum takes on the heat quickly, but it also transfers the heat quickly. This was was proven by @77 K20 's highway running in the cold weather.

I also know as you stated, an air cleaner with the hot air stove makes a big difference in cold weather running. Using the heated air cleaner with a cast iron intake manifold you will have a better cold weather running engine.

Someone talked about modifying an older cast manifold to use on the vortec heads....?

Also my understanding is there is no provisions on the vortec heads for an exhaust cross over, so a working heat riser won't help.

If it is possible to run an EGR valve on a carbed vortec I could see that helping as well. Looks like GM makes a carbed vortec manifold with plumbing for an externally plumbed EGR valve like the factory FI systems have. The one site I saw it on wants $422 for it though. Wow. I bet that would help with manifold temps, assuming the EGR is setup to come on with ported vac, so it would be running most of the time off idle. something else to think about, but boy that's a chunk of change for just a manifold.....

However I can see the point that a cast manifold might be better since it'll hold heat better.

 

[48hd]

I run a 350 vortec w/edelbrock performer dual plane intake, 750cfm edelbrock carb, ported the heads, and run headers. Got a 350 automatic with a lockup converter and a 2.73 rear end. I've checked the mileage twice on a freeway run to texas. Running 95 mph for 4 hours mine gets 13.6 mpg.
I never have used the choke. it's undone. Mine starts and runs in 20-30 weather fine.

 

[77 K20]

I did some searches last night and read up on some of your threads. Are you running a thermac? Not sure that would be enough heat at 3K but just wondering.

Thanks for the info. Part of it is I'm genuinely curious even if I decide not to go this route.

No thermac. I have the corvette ram horn manifolds so didn't see how I could make a heat riser easily fit around those. Was running an open air filter which a lot of people hate as "it draws in hot air from around the engine!" For winter time I did experiment with completely blocking off the grille of the truck. It made no difference for engine warm up times. By blocking the grill it just sucks air in from around the headlights, the little oval ports below the grille and from behind the bumper.