TrunkMatt
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Posts posted by TrunkMatt
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So, my old Qjet had the vacuum advance running to a manifold/full pressure port. This new Edelbrock recommends the timed vacuum port...
I tested it on the Timed Vacuum port, and the Manifold port... aside from idle speed - I haven't noticed much difference.
Which is recommended for our engines? What gives the best power curve? Some internet people are saying run the vacuum advance to the timed, others are saying leave it on the manifold/full....
Thoughts?
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I honestly can't believe how smooth this new carb runs compared to my Qjet. My car is a lot quieter at idle too... and idles smooth as can be. Runs about 20 degrees cooler.
Qjet must've been running real rich and having a lot of combustion in the headers before. Based on the bolt-ons that were on this car, I am betting the previous guy tried jetting the Qjet... we'll find out when I tear into it.
Until then, I am VERY pleased with the results of the Edelbrock... very pleased.
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Run a wire to the IGN or ACC terminal on your fuse block...
Yeah... the wire wasn't quite long enough to get there.
It was long enough to get to the wiper-motor assembly, however, which is ignition controlled. Tested it through with my volt-meter to double-check. All systems go... and got the proper connector to tie it into the Pink wire.
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Well, I went out and bought an Edelbrock 1406 (600 CFM with Electronic Choke)...
Where did you hookup your electronic choke?
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This stuff should work too.. and may be easier:
http://www.amazon.com/Heatshield-Thermaflect-Tape-10-Roll/dp/B002UPLBDS
Today I went all out to fix my problems once and for all. Bought a new Edelbrock carb with heat shield and bought braided heat shielded fuel line and reran the line from the pump to the new carb.
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Well, I went out and bought an Edelbrock 1406 (600 CFM with Electronic Choke)... it was only $250 at my local store that is located a few blocks away.
REASON WHY: I am just learning to do all this... I never changed a carb out before in my life... and I need to start easy. While I like the science behind the Holly and the Demon's... I am not skillfull at tuning yet.
I eventually want to rebuild my Quadrajet myself... and polish it and paint it. However, it will take me a while to do this. Until then --- I need something easy and reliable. Also the edelbrock functionality resembles that of the Quadrajet... so I want to stay in that mindset.
I actually was able to get it all installed today (everything but the electronic choke... need to wire that tomorrow when there is light)
Again, I never swapped a carb out before in my life. Followed all the directions and watched every video I could find. While I was at it I replaced my old vacuum lines and fuel line with some nice braided stuff.
Anyhow -- it fired right up... which is more than my Qjet would do.
Set the idle while manually disengaging the choke... and all seems well.
Tomorrow I need to buy the kickdown plate adapter, wire the elecronic choke, and attempt to tune it.
I am quite happy with the results thus far.
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Lets talk Carbs for 350's
I am at the point where the Qjet needs a rebuild. Despite all the West Coast monte people helping in person, a random mechanic, and Steven the engine guru's personal touch, we just can't get the idle set right. It sometimes runs rich, and sometimes lean... and she is a bit leaky on the throttle body. Not to mention a few Vapor Locks in hot weather.
Now, I love the Qjet feel... the "false wall" that your foot pushes through before the HUGE secondaries open and BAM!!! And my Qjet is numbers matching... so I will hold onto it, and try to rebuild it myself over the next year or so.
Until then, I think it is time to "release the genie" from the bottle and see what my engine can really do with a performance carb.
My engine already is Cam'd, has an Edelbrock intake, hooker headers, and I have a mean exhaust that makes my pants feel funny in all the right places... So, I think it is time to Carb Up.
What recommendations do ya'll have?
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Common Chevy problem, and carbureted engine problem in general. It actually happens to a few of us, especially if it is above 90 degrees, and you live in a dry climate. It is due to a form of Vapor Lock... and is made worse these days by the damn Ethanol blended fuels with a lower evap point... this new gas evaps about 5% lower than non-ethanol fuel.
Here is what is happening (as best explained to me when I had this issue).
The carb and fuel line is heated by the engine while driving. When you turn off your car, off the coolant stops cycling and the engine actually increases in temperature a bit, and the fuel line and float chamber heats up more to the point where the fuel begins boiling away / gassifying. This causes the fuel in the line or the carb to vaporize... and now you have vaporlock, as there is no liquid to pump.
For some of us it happens while idling at a stop light for more than a few minutes. Did to me in Boise. It gets worse as you get higher above sea-level.
FIXES:
Try getting some heat shielding on the carb and the fuel line to make sure it stays cool... For fuel lines int eh od day, the old-timers used to buy about 20 wooden clothespins and clip them to the fuel lines to shield & insulate it from engine heat. It actually works. Now you can buy the aluminum wrap.
If the fuel line runs near the block / headers etc - you'll want to move it at least 1/2 to 1 inch away and insulate it. Most gasoline can boil / gassify at 100°F... so it is important that the lines stay cool.
For the carb heat shields there are a variety - and you are probably missing yours. It should be installed standard these days - but most rebuilders don't know about it (mine was missing). http://www.jegs.com/i/Holley/510/108-70/10002/-1?parentProductId=743655
http://www.google.com/products/catalog?q...ved=0CEcQ8wIwAA
Also, some cars don't have a fuel vapor return line to the tank (I need to add one). This amplifies the issue as the vapor can't escape to the tank and draw up more fuel as it leaves.
The true fix seems to be doing all 3 things: Heat Shield / Spacer on the Carb, Insulating the fuel line, Installing a fuel vapor return line. People that have those three things done seem to never get v-lock.
In the meantime you can add some fuel stabilizer (drygas) or carb cleaner like SeaFoam to a tank, that lowers the evaporation point. Read up on ones that have a low RVP (Reid Vapor Pressure) taht means they have to be heated higher to evap.
If you can't get it started, you can always also dump some cold water right on the fuel line and it'll chill it just enough degrees (about 10 or so) for the fuel to liquify again... I had to do that when i vapor-locked while idling at a stop light.
Keep your foot pressed to the floor (don't pump - just keep it full on) while starting in these situations.
ULTRA CHEAP SOLUTIONS:
The cheapest solution is to do what my dad called the "Chevy Hangout"... which is a bunch of guys that own Chevys sitting around talking for 30 minutes while their engines and fuel systems cool enough to start.
Sometimes it is nice to find a place to grab a beer or a soda... and think about how great our cars are, despite the issues. Should take 30 minutes :-)
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Well, I only got the vapor lock while in Boise, which is 4,900 ft higher in altitude than where I live in Oregon... and it was also about 95 degrees the day it happened.
Here in Oregon, it doesn't happen unless I am sitting idling in the sun for 30 minutes.
Runs fine on the open highway / any situation when it gets plenty of gas... V-Lock only seems to occur when idling at long red lights (some were 3 minutes) in hot weather, at altitude.
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I have a stock 4bbl Quadrajet sitting on top of a Edelbrock manifold.
I don't know where the lock is occuring, a the pump, the line near the engine, or the carb itself.
I honestly am suspecting my Vaporlock issues are occurring in the line itself leading to the carb... as it wasn't run past the waterpump like most metal lines (mine runs behind the alternator and touched the engine block at one point... I bent it away and am hoping it helps)
Really, I suppose I could just go with an electric pump in the tank - remove the mechanical, and run a positive pressure system thus eliminating the issues... I am okay not having a 100% stock engine bay.
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Thanks to a few repeat visits from uncle vapor-lock, I have decided that I probably should add in a Fuel Vapor return line back to the tank.
Most the montes I see have one... but mine does not. Crawled under, and there isn't even a return line in the frame.
Now for my question:
I see some montes that have the return line off the fuel pump... and others that have it off the filter near the carb (which makes more sense to prevent vapor lock).
I am imagining this lowers fuel pressure to the carb some... so what all should I be looking to install????
Is there a fuel pressure or vapor regulator that also sits inline on the return line that enables the return to only work over a certain PSI?
I know the vapor return lines are smaller, but I can't help think if it is all setup wrong that I'll be starving my engine.
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I just cleaned off the leftover remnants of the bird I hit on the way home from the western meet.
It was pretty gross... but I took a picture if anyone wants to see
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I'm in... even if I am living in Asia again for work, I will be flying back for this.
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I have a few amazing pics from the drive home today with the Canadians... the rest from the meetup will have to wait until we fire up the wife's computer and edit (she wants to go through them first... there are over 500!!!!)
Sleepy sleepy:
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Awesome!
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Honestly guys, the best part of owning this car has been meeting all of you and making new friends / family.
The Western group of individuals I met is quite obviously a tight-nit family with a lot of history... but you all remain very open, friendly, and welcoming to us new members.
You all just created memories that get filed with my best life experiences.
Cheers to you all,
Matt (TrunkMatt)
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My MCSS was delivered a day early
. I've had a chance to check it over and will be bringing it to Boise Saturday!!!!! Should be there early afternoon. Really fired up about the Motorfest now 
. See everyone tomorrow...... SWEEET!!!
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The did not bring the cat, in case someone wants to know.. ;-)
We both brought the cat and didn't bring the cat at the same time. You'll never know until you look in the room.
Love,
Schroedinger
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It was great meeting everyone this evening... was really nice sitting out in the parking lot looking at all the Monte's.
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I hit the road in 1 hour!!!! WOOOOOOOOOHOOOOOO!!!
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From what I found on the net - copied from a Chevelle forum"
"The trans spark selonoid is designed to not allow vacuum advance until you are in a top-end gear and the engine is up to temp. It is a very primative emission control device. I'll say that there is only a few left working and they are on NCRS cars. I had one on mine when I originally built the car and quickly took it off. It serves no performance at all so it is not on my car. "
So essentially it keeps your timing from advancing until warm.
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Speaking of internet access... as long as there is T-Mobile coverage, we'll be able to setup a wireless hotspot during the day at the meet for everyone in FGMCC (using our 4g tethering).
As long as people keep it porn free it should be ok for the basics :-)
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All systems go Doug!!!!
9:30am is perfect timing... we'll be ready. The wife is out getting some road snacks.
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It is amazing what new tires can do...
Now - before anyone says "NO NO NO!!! - CHINESE TIRE!!!" I know I know... itis intentional.
I decided to put on some cheaper tires that were the same size I want to move into to test feel and fit. I figure I'll run with these for a few months, and switch into the final more expensive tire later... or mess with spring and shocks and do something different. The proper tires are real investments, and these are a good "interim" tire to use before i make up my mind.
Besides, what's more American than something made in China?
Anyhow - the sizes are:
FRONT: 235/60 R15
REAR: 255/70 R15
I now have almost 4 inches to the headers - and I like the new more aggressive stance the bigger rears gave the car. Being a cheaper tire, these are a little more "bouncy" on the road -- but they are pretty quiet, and will give me a nice comfy ride to Boise.
Most importantly, the speed-o is not accurate.
Vacuum advance: Timed or Manifold pressure?
in Engine Tech
Posted
That's the manifold pressure side...
I heard a slight knock at idle when using that side, which I think is an indicator it is drawing my advance too far forward at low speed.
I suppose I should get a vacuum gauge, and see what the readings are at each port at about 2500 rpm... if the timed advance works as advertised, they should be about the same.