Vortec heads- cold weather issues?

[DoubleDingo]

That is it, not a bad price considering it may be difficult to find someone to build one cheaper.

 

[77 K20]

So after more reading, talking to Edelbrock and a guy I know who builds engines it looks like the best thing to do is to buy the Edelbrock Performer RPM intake 7116. I shoudn't lose much of anything as far as low RPM torque and it is still a dual plane so throttle response will still be good.

The plenum heat passage under the carb/TBI can be used with either coolant or exhaust. I'm going to hook it up to exhaust. Unfortunately this will look pretty stupid running lines from the exhaust manifolds on both sides up to the manifold. Will need to make sure it doesn't melt fuel lines or spark plug wires. It might hurt performance a bit in August during the day here, but I work nights and nights are often very cool. Also if it is that hot during the day I probably won't be driving. The truck has no AC.

Now I just need to save up some $$ and get this done before next fall.

 

[Daveo91Burb]

I'll be following this one close - I'm in the planning and gathering parts stage for a 383 vortec head, TBI-injected build. I already have a '90 TBI 4-bolt block (has the provisions for roller cam), machine shop rebuilt 062 vortecs, the GMPP spread bore manifold, and a TBI adapter plate for that manifold. I also bought a vortec core motor from a '96 burb (w/ everything fan to flex plate and throttle body to oil pan) so I have the exhaust manifolds and all the external EGR plumbing. So is there general agreement that running EGR will solve this problem? I do plan on running EGR, mainly for cooling and hopefully a little more economy, but if it can help with the cold weather part too that would be great.

I have two anecdotal stories that hopefully will add to the discussion, but just ignore if not.

1. I've been running vortecs with the GMPP intake on my '76 Vette for the last 5 years or so with no problems. EGR plate is blocked off, no hot water to manifold. But big grain of salt since I don't drive it in the winter much and we don't get crazy cold weather in my corner of the country very often. But....I do start it in the winter occasionally and there is no hint of any idle problems. I run a q-jet and choke works just like it should and when it's ready to come off a small tap of the pedal will bring it down and it will idle at 600 just fine. (not a real big cam, though). Always starts on the first try, too.

2. I do know what it's like to drive a car with gas puddling issues. I grew up on the east side of the cascades where it is a little colder. In high school I drove my dad's '64 f-100 with a 292 V-8. Those motors have an air gap style of manifold with no real warming mechanism to speak of. That damn thing would idle like crap almost the whole way to school (5 miles) and just be warmed up by the time I got there. We tried multiple different carbs and choke systems but they were always holley 4 barrels. Finally ended up converting back to manual choke which at least allowed me to not have to keep my foot on the gas at lights (sometimes). It frustrated the hell out of me back then because I thought it was something not tuned right but I've come to believe later that it was just the design of the intake manifold that caused the problems.

 

[77 K20]

I seriously thought about running an EGR as I believe I have the same GMPP spread bore manifold that you do. My problem is I don't have a factory computer to control it. I started looking at how to control it without a computer and decided I didn't want to go that route. It doesn't work as well as an ECM controlled unit that will cycle it on and off with a duty cycle. That being said- I think running an EGR on that manifold would work. It would bring hot exhaust in the front corner and then across the manifold near the carb/TBI as the EGR valve itself mounts there. Then when the EGR is on it delivers hot exhaust to 2 ports directly under the carb/TBI. Although I believe the ECM keeps the EGR off if you are just idling and then starts adding it in only when driving.

I wonder if the manifold on your Vette has the little waffle pattern on the plenum right under the carb? This is supposed to help with gas puddling. The GMPP manifold I have right now is perfectly smooth there.

I really hope this works- and am pretty sure it will work. I've spent the last year and a half confused on why cold weather makes it run bad. The worst part of it running horrible when cold is I have to cross 4 lanes of traffic on a highway near my house to get to work. NOT the place you want a truck to bog down and sputter. And I work nights so I drive when it is cold more than most. Only in July, August and September is the average low temperature at night above 40* F here.

 

[Daveo91Burb]

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Here's some pics of the manifold I will be using on the burb - same as yours and I'm 99% sure it's the exact same one I have on the vette (smooth runners, not baffled). In any case I hope the ebrock works for you. I totally get what you mean about EGR without computer controls to run it. Modern cars and even those from the tbi era like mine I think EGR works very well and actually has some positive effects besides reducing NOx. But they have computers to control it and it only comes on when appropriate. Not so for 70s cars - the "computer" was simply a ported vacuum signal from the carb. Just didn't provide enough control and it caused a lot of problems on cars from that era (including my vette before I rebuilt the motor!)

Thanks for the info and keep us posted.


Sent from my iPhone using Tapatalk

 

[bucket]

^^^Who makes that TBI adapter? Looks like it puts the TBI in the correct location for the stock throttle linkage?

 

[Daveo91Burb]

^^^Who makes that TBI adapter? Looks like it puts the TBI in the correct location for the stock throttle linkage?

I bought both the adapter and the TB itself on Ebay, different sellers. Here's the TB, it's been bored to 46 mm, a little bigger than stock.

http://www.ebay.com/itm/GM-TBI-91-9...m2c7849ef0b:m:mkexT4TSdUctuYrEjn8imcA&vxp=mtr

And here's the adapter that fits the 46mm:

http://www.ebay.com/itm/46mm-1-13-1...ash=item1eae474435:g:ItMAAOxyTMdTOZXX&vxp=mtr

I think (hope) you're right that it keeps the throttle linkage in the stock location.

Question related to this thread: does anyone know if outlets on the Vortec exhaust manifolds would be in the same location as TBI manifolds? I want to use the vortec ones (for EGR) but I don't want to have to have a custom y-pipe made. (I bought it with a 3" single exhaust after the y-pipe - no cat....)

 

[77 K20]

Sorry Dave- but don't know about the exhaust outlets.

I just bought a ton of stuff online. Ended up getting that 7116 intake manifold, intake manifold gaskets and new bolts, misc 1/2" NPT fittings, a new throttle bracket, some flexible silicone heater hose, and a taller thermostat housing (so it doesn't block a fitting underneath it). So there goes $500. Hope this is worth it.

I called an exhaust shop today and they didn't seemed to be too thrilled about my idea of hooking up the intake manifold to exhaust. So figured I might as well experiment with coolant first. It can be easily removed and swapped over to exhaust later if needed.

I used my infrared thermometer and did some measuring today (although it is now unseasonably warm). My "cold" start today had all components under hood at 61 degrees. In under 3 minutes the thermostat area and the heater hose were starting to heat up already. Under the throttlebody was the same temp. After 15 minutes the heater hose and the thermostat are were 165 degrees but the intake manifold near the TBI was only 85. So you can imagine what the manifold temps are like when you start at 20 degrees.

So based on that, I'll try running coolant under the TBI and see how it does. There will still be some 30 degree nights to test it out on.

If all goes well I'll have my old GMPP intake for sale. Should work fine for someone in a warm weather climate.

 

[MikeB]

You see that threaded hole on the left front of the GM intake? You actually circled it in green in another response. You need to have a bung hole welded into your driver's side exhaust and plumb a pipe to that hole to warm up the intake under the carb. I don't have a GM 383, but I did swap over vortec heads and used that same GM intake, and have the same cold running issues you mentioned. When warm it runs great, but stumbles and stalls until is gets warm in the winter months. I haven't added the exhaust tube to the hole mentioned, but I'm sure it would help heat the intake, since it was designed to do just that.

What is the path for the exhaust gas? Ideally it would go through the manifold, not just into a port and "dead head".

***77K20 -- I sure would try to determine why the coolant temp swings so much. Could be a sticky T-stat. 170 degrees is not a good thing. Also, you might want to try putting something in front of the radiator in the winter, like a piece of cardboard to start with, and something more durable like sheet metal if the cardboard works. Or how about an electric fan instead of your mechanical fan? It would be dead still until some preset temp, like 190.

 

[77 K20]

The t-stat I have is the expensive GM one the owners manual recommended. I ordered a Stand superstat last night and will install that at the same time. They claim their t-stat is good about not overshooting and having temp swings.

I've thought about electric fans, but my 63A alternator can't handle it. It would then lead to a serpentine belt swap and a lot more money and work. Maybe next year- as I just want to drive it now and enjoy it. Besides my money tree is pretty much dead.

 

[Daveo91Burb]

One thing that just hit me when I posted that would be the heat riser tube to the air filter can. It may be a funky thing to set up but I bet it would work. If you run headers though it may have to take something custom fabricated. The cold air being drawn into the intake would keep the intake ice-cold, possibly to the point of frosty cold. The heat riser tube would get "warmer" air into the mix quicker. Maybe have a valve hooked up on it you could control with a manual choke knob or something. Just an idea.

Mike, have you thought of trying this idea? The heat riser tube to the air cleaner was pretty much standard issue on everything in the 70s all the way thru the TBI era. It can be tough to go back to the stock set up though - so many rigs have been converted to open element and a stock air cleaner set up is hard to find and can be expensive if you do find one. My burb still has the original air cleaner with this tube that I still use. Maybe it will help, not sure. Headers would definitely add a challenge, too - can't remember if you're running them or manifolds. I also like the idea of a shutter for the radiator and playing around with different thermostats.

So a 100 amp alternator requires a conversion to serpentine? They don't have them for a v-belt set up? Electric fans are spendy, though. I want to convert someday, but it will be a while....

 

[77 K20]

I thought about it a bit, and it would be hard to do. My truck has an open element air cleaner and I don't have the stock exhaust manifolds on it anymore. It has the corvette ram horn manifolds now. I did think about taking something like a 5 gallon bucket and cutting it down to size and install that right over the open element making it draw air up from the intake manifold and the top of the engine.

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[77 K20]

***77K20 -- I sure would try to determine why the coolant temp swings so much. Could be a sticky T-stat. 170 degrees is not a good thing. Also, you might want to try putting something in front of the radiator in the winter, like a piece of cardboard to start with, and something more durable like sheet metal if the cardboard works. Or how about an electric fan instead of your mechanical fan? It would be dead still until some preset temp, like 190.

Also another thought on the coolant temperature swing... GM had this in the owner's manual for the engine:

"Any small block engine, regardless of year, that uses Vortec heads, will require an external coolant bypass line from the intake manifold to the 5/8" hose nipple on the water pump (passenger’s side). Suggested routing is from the 3/8 NPSF boss on intake manifold to the water pump."

I had also read about this for dozens of hours and seems people say 4 things on this.
1) They do nothing and it works great!
2) Coming from the intake manifold to a heater core works as a bypass
3) You have to come off of the front of the intake to the water pump.
4) Just drill out 3 holes in the thermostat to provide a bypass.

I'm doing #2 currently. I tried #3 but both fittings are very close together. What GM showed was a water pump that had a built in nipple sticking out of the pump. I just had a tapped hole and put in a straight fitting. I forced a section of heater hose on there and it leaked. I removed it.

For the new intake I'll run from the intake to the heater core and to the radiator. I'll also go out of another port near the thermostat on the driver's side thru the coolant passage under the TBI and then back to the water pump. If for some reason that doesn't work or somehow provides too much bypass (is such a thing possible?) then I'll run everything in series. Manifold to TBI coolant passage, to heater core, to radiator.

 

[68post]

I had to skip to the end on this because I see that nobody thought of the late '80's bbc OEM tbi adapter that is made for plumbing and very inexpensive used.

Sorry I can't post a pic , here's one but not necessarily cheap - I bought one for much less.

http://www.ebay.com/itm/OEM-Fuel-In...ash=item3abfc28562:g:0IkAAOSwBnVW9cSa&vxp=mtr

 

[DoubleDingo]

What is the path for the exhaust gas? Ideally it would go through the manifold, not just into a port and "dead head".

I thought of that after posting.

A block heater might be the easiest thing, just not for his return trip home after work.