Carb'ed vortec looking for info and opinions

[SirRobyn0]

Dude. I've been down this path. I've learned some valuable lessons. These are my experiences.
1. FORGET putting 1 cent into a 305. You can build a 350 for the exact same price for a much better result.
2. If you don't have a 350 to begin with, just get an LS. Complete running engines are available for like $1200.
3. I put new Vortec heads on a crate Goodwrench 350. I wouldn't do it again. Get an LS.
4. You want a truck that's reliable, drives like a new vehicle and gets good gas milage? I spent $1200 for a Edelbrock pro Flo EFI. It's nice reliable and drives like a new truck.
5. Gas milage! Lol, it's a square body, ain't gonna happen. Would I do it again? Nope. Wished I'd spent that $1200 on an LS. Hopefully I made my point.

My take away on your point is you like the LS and that's fine. LS is not going to happen for this truck, when the time comes it'll need to get back to work quickly and I see an LS swap as time consuming, and probably expensive. If I decide there are to many potential issues with a carbed vortec (and the cold run thing is looking like a deal breaker right now) I'll be much more likely to do a 350 or possibly a 454 swap. What I don't like about the 454 is none of my peripherals will bolt to it.

As for the 305 I don't plan to rebuild it, but I think it gets a bad rap for what it is.

 

[AyWoSch Motors]

My take away on your point is you like the LS and that's fine. LS is not going to happen for this truck, when the time comes it'll need to get back to work quickly and I see an LS swap as time consuming, and probably expensive. If I decide there are to many potential issues with a carbed vortec (and the cold run thing is looking like a deal breaker right now) I'll be much more likely to do a 350 or possibly a 454 swap. What I don't like about the 454 is none of my peripherals will bolt to it.

As for the 305 I don't plan to rebuild it, but I think it gets a bad rap for what it is.

I agree the 305 does get a bad rap.
I had one in my 86 for a long time. Good engine, did its job well. Although it did kablooy itself a while back for no apparent reason, so I'd have to say not all the rumors are false.

I've never heard of this Vortec cold start issue. My 97 will start right away even in the coldest of weather here.

 

[SirRobyn0]

I agree the 305 does get a bad rap.
I had one in my 86 for a long time. Good engine, did its job well. Although it did kablooy itself a while back for no apparent reason, so I'd have to say not all the rumors are false.

I've never heard of this Vortec cold start issue. My 97 will start right away even in the coldest of weather here.

I'm just learning, but this is what I've read. The thought is it's the lack of an exhaust cross over in the intake manifold causing the fuel not to vaporize properly and fall out of the air and pool in the manifold therefore causing it run crappy at idle and low RPM. Seems like for most folks it'll run good when the choke is on, then after the choke is off crappy until fully warm, as in the metal in the intake gets warm.

I'm not saying that the lack of exhaust cross over isn't the cause, but there were lots of factory 4 cyl cars and trucks produced without any sort of intake warming devices and they did fine. Also I ran a 360 in MH with the cross over blocked do to percolation issues in the summer and it never gave me any trouble, but I've read that's not a fair comparison because the ports in the head will get the heat closer to the manifold plus was designed for carburetor. Vortec was not. There is one intake manifold that pipes coolant right under the plenum part of the manifold to help with this issue, seems like most that try it get at least some help, but in a search I found one of 77 K20's threads where he talks about getting two of those manifolds leaking cooling due to porosity. The final solution was alumaseal.

As I said before we don't get a lot of cold here so I might be ok, but on the flip side I don't wanna get into eastern Wa with the trailer one day in the winter to find temps in the teens and it running bad with a loaded trailer. I'm inclined to think that running a thermac and "hot water" intake would be enough where I'm at, but if I'm wrong I'll end up with a truck that won't be able to do what I need it to do when I need it to. I will continue to think on this and research.

 

[bucket]

I didn't know, he'd be just the guy I'd wanna hear from then on this then, though he sees much colder temps than I do.

Those much colder temps probably make a difference too. I personally haven't had troubles with cold starts on carb vortec combos, including cold weather. It's just not AS cold I'm sure... I'm also not exactly particular when it comes to cold starts. As long as it will start and run without dying within 30 seconds or so, that's good enough for me.

 

[SirRobyn0]

Those much colder temps probably make a difference too. I personally haven't had troubles with cold starts on carb vortec combos, including cold weather. It's just not AS cold I'm sure... I'm also not exactly particular when it comes to cold starts. As long as it will start and run without dying within 30 seconds or so, that's good enough for me.

That makes sense. If you wouldn't mind, tell me a little about the carbed vortec combos you have had then. What have they been in? What did you or didn't you like about them? Thanks

 

[DoubleDingo]

Carbed Vortec 350. Works great! Yes, cold temps you need to feather the throttle to take off from a start, but once it is warm there is no issues. Runs strong, good torque, pulls hills and hauls with ease compared to the smogger heads. The only upgrades to this engine is an old school 327/300hp camshaft, vortec heads, gmperfromance spreadbore intake, and different jets in the carb. Used the heater core return to the radiator for the coolant bypass.

If you go this route, get the self-aligning rockers. I didn't know about this and used the stock non-self-aligning rockers. It worked fine for a while, but then number 7 exhaust rotated off the valve stem.

 

[SirRobyn0]

Carbed Vortec 350. Works great! Yes, cold temps you need to feather the throttle to take off from a start, but once it is warm there is no issues. Runs strong, good torque, pulls hills and hauls with ease compared to the smogger heads. The only upgrades to this engine is an old school 327/300hp camshaft, vortec heads, gmperfromance spreadbore intake, and different jets in the carb. Used the heater core return to the radiator for the coolant bypass.

If you go this route, get the self-aligning rockers. I didn't know about this and used the stock non-self-aligning rockers. It worked fine for a while, but then number 7 exhaust rotated off the valve stem.

Thanks! I for sure appreciate the pictures. It looks great! That's exactly what I would want, better power for towing and hauling. If you have ever checked I'm curious what your getting for mileage.

 

[DoubleDingo]

Thanks! I for sure appreciate the pictures. It looks great! That's exactly what I would want, better power for towing and hauling. If you have ever checked I'm curious what your getting for mileage.

Honestly I haven't checked it for mileage since I did the swap. I took it on a road trip in February '13 when it had the stock setup. I calculated the miles using google maps, every little turnout, side road, stop, etc and it got a solid 8 mpg. I know for a fact it gets better then that now, as a tank driving around town will last two weeks easily, whereas it was maybe a week before. Same amount of miles driven to and from work. With the vortec setup I can tell I am using less pedal to keep the truck moving. I need to add a vacuum gauge so I can visually see how good it does in various conditions.

The vortec has a nice crackle to the exhaust tone, it sounds cool. That cool sound makes one want to mash the throttle to create more of that sound, so when there is pedal mashing going on, the gauge drops quickly just like any other vehicle would...lol...

 

[DoubleDingo]

Another thing, this truck passes emissions with ease, too. The guy that runs the smog shop I go to says he likes the way the truck runs, and that is runs clean. I mentioned to him that is has vortec heads on it, asked if that would cause the visual to fail and he said "No". Basically, it looks factory, has all the smog equipment that came with it from the factory, and it runs well. I can even take it in cold and it will pass, and that is with zero shenanigans. He doesn't mess around, if there is a problem he will tell you, but he will also show you where the problem is, not make you figure it out.

 

[SirRobyn0]

@DoubleDingo thanks for the info. I do not have to worry about passing smog or visual inspection, but still I like what you are saying. I wondered how much it would change the exhaust tone. Currently I'm still running the factory style single exhaust, but with somewhat bigger pipe which I'm sure is more than enough for the current 305. At least initially that's probably what I'd use after the swap, but later on would switch to dual as I'm sure the vortec needs more exhaust flow.

 

[DoubleDingo]

@DoubleDingo thanks for the info. I do not have to worry about passing smog or visual inspection, but still I like what you are saying. I wondered how much it would change the exhaust tone. Currently I'm still running the factory style single exhaust, but with somewhat bigger pipe which I'm sure is more than enough for the current 305. At least initially that's probably what I'd use after the swap, but later on would switch to dual as I'm sure the vortec needs more exhaust flow.

Mine has the stock 2 inch from the manifolds, into the single 2.5 inch, and then 2.25 inch over the axle and out the back of driver's side rear tire. It runs strong, revs high if I want it to, no issue with power at all. This is the first truck I've run with single exhaust, and honestly I will run any v8 vehicle with single exhaust from here on out. If I ever need to redo the exhaust on this truck it will get single exhaust installed back in it. I did change the stock muffler to a long glasspack and then a short glasspack upstream. It's a little too loud now, but flows very well.

 

[SirRobyn0]

Mine has the stock 2 inch from the manifolds, into the single 2.5 inch, and then 2.25 inch over the axle and out the back of driver's side rear tire. It runs strong, revs high if I want it to, no issue with power at all. This is the first truck I've run with single exhaust, and honestly I will run any v8 vehicle with single exhaust from here on out. If I ever need to redo the exhaust on this truck it will get single exhaust installed back in it. I did change the stock muffler to a long glasspack and then a short glasspack upstream. It's a little too loud now, but flows very well.

Ok cool, my setup is near identical, except I'm running a high flow cat, a Walker sound FX muffler, which is suppose to flow pretty good, and duel 2.5 inch exits which both come out on the drivers side. That's the factory setup for mine I'm just running a little bit larger pipes than stock. Like you I like the single setup I've got. Good to know I'd be able to keep that.

 

[DoubleDingo]

Ok cool, my setup is near identical, except I'm running a high flow cat, a Walker sound FX muffler, which is suppose to flow pretty good, and duel 2.5 inch exits which both come out on the drivers side. That's the factory setup for mine I'm just running a little bit larger pipes than stock. Like you I like the single setup I've got. Good to know I'd be able to keep that.

I think '81 may have been the last year with no cats, at least for CA C20's, but I may be wrong on that. My Pop said they had something like 8 different emissions variations during 1981. Mine is a January 1981 truck, no egr, no cat, just a pump and the plumbing to the manifolds.

 

[bucket]

That makes sense. If you wouldn't mind, tell me a little about the carbed vortec combos you have had then. What have they been in? What did you or didn't you like about them? Thanks

Well, I actually can only think of two right now. I have both. I swear I'm forgetting one though.

The first one actually hasn't ran yet since my ownership. But it was in my buddy's Camaro. Mild cam, air gap style dual plane intake, holley carb with electric choke. Nothing out of the ordinary with coolant plumbing. Just street driving, no towing of course, lol.

The second is my '77 K10. Same deal with mild cam and no abnormal plumbing, but with an Eddy carb. No towing, but you can fire it up and after a short warmup, you can give it hell in the mud and woods with no trouble at all.

 

[SirRobyn0]

I think '81 may have been the last year with no cats, at least for CA C20's, but I may be wrong on that. My Pop said they had something like 8 different emissions variations during 1981. Mine is a January 1981 truck, no egr, no cat, just a pump and the plumbing to the manifolds.

I'm not to good with cut off years for cats an emissions. What I do know is when my Dad bought his 78 GMC in 80 one of his prerequisites was that it did not have a cat. So He ended up with a 78 K20. Back in those days when cats were pellet cats I can understand wanting to avoid having one, now a days cats, even the universal type are so much better. I can't remember anymore if Dad's truck had an EGR valve or not.

Well, I actually can only think of two right now. I have both. I swear I'm forgetting one though.

The first one actually hasn't ran yet since my ownership. But it was in my buddy's Camaro. Mild cam, air gap style dual plane intake, holley carb with electric choke. Nothing out of the ordinary with coolant plumbing. Just street driving, no towing of course, lol.

The second is my '77 K10. Same deal with mild cam and no abnormal plumbing, but with an Eddy carb. No towing, but you can fire it up and after a short warmup, you can give it hell in the mud and woods with no trouble at all.

Cool thanks for the info. I thinking more and more that for my climate a carbed vortec might work out just fine, but that cold run issue is something to consider for sure.