carb tunage

[roadrage41]

so i finally had a free couple of bucks and went and got a vacuum gauge and a small enough screw driver to tune my carb (youtube videos rock) as part of the ongoing saga about learning something about carbotators.

when in D the most i can get out of it is 15g, that normal? (i plumbed it into the T that runs my distributor, the tranny connection and part of my vintage air system, i left the vintage air part unhooked figuring it would be the closest to the amount of pull the gauge would do.) itll bump up to 18g in park. its a 650 cfm holley, vacuum secondaries with no choke. on what im 80 percent sure is a 305, i just cant reach to see the casting numbers because theres a firewall in the way...

all in all though that was the largest part of the truck running like poo, now i just need to fix the dang exhaust leak from the passenger manifold, get a performer intake manifold and prob throw a new distributor at it just because.

also i installed one of the el cheapo mr. gasket fuel filters because the truck didnt have one at all. is it normal for all of the fuel to drain out of the line, as soon as i shut the truck off? its pretty instantaneous. id assume gravity would take over eventually, but youd think itd take a little bit atleast.

[VileZambonie]

What exactly are you trying to do? I'm confused  Are you trying to make your truck run better or are you trying to get a high vacuum reading? A lot of people tend to think a high vacuum reading means your carb is properly tuned and this is not the case.

#1 Set your timing to it's optimal advance.

#2 Adjust your idle mixture screws to where the truck has the best idle quality

What cam are you running?

What drivability symptoms are you having?

[roadrage41]

[youtube=425,350]http://www.youtube.com/watch?v=y8obZBs6DJw[/youtube]

truck ran like bad, had to do 6-7 starting attempts before it would actually idle, then let it run 10 mins or so before i could put it in gear without dying. then it would proceed to bog everytime i looked at the gas pedal for about 5 minutes after that.

cams unknown, heck motors unknown

[VileZambonie]

then it would proceed to bog everytime i looked at the gas pedal for about 5 minutes after that.
 

This sentence makes no sense.

So you have a hard start and it bogs when? Is that choke set up properly? Is it opening? When does it bog? Give more info on your truck too.

[HAULIN IT]

 This sounds like a choke problem for sure & maybe a combination choke/leaky (in operational) accelerator pump. Once it warms up (10-15min. run time) can you give it the gas & accelerate without the bog? Lorne

[roadrage41]

i dont have a choke.

when i bought the truck (82 gmc 2wd lwb), it had a 750 cfm holley, and some sort of weiand single plane manifold on it, which was installed by the guy who owned it - before the guy i bought it from.

a buddy of mine had a 650 cfm holley on a brand spanking new rebuild, that he offered to trade me for the 750, or flat out sell me for the price of the rebuild kit, i just traded him, because i have no use for that 750. its just too big all around, and you could tell when it was on the truck. the 650 had #70 jets, which i changed to # 64's.

what we know about the truck so far - it was originally an AOD truck, that someone swapped a th350 into, and was also smart enough to do a pre-e.s.c. distributor swap on. (it may be a pre-78 motor altogether) i cant get to where the casting numbers are on the back of the block by where it meets the transmission because its too close to the firewall. my only thought at the moment about that is to eventually change the valve cover gaskets, and get the casting numbers off the heads, and try to identify the motor that way. i assume its a 305, because like 88 percent of them came with 305's. i read theres supposed to be a plate near one of the exhaust manifolds on the block that has the casting number on it as well, but i cant find it.

the guy i bought it froms dad bought it for him as a commuter (HAHA i know right?) and decided he would learn how to repair a truck while his son was still in iraq, thus i have brand spanking new floorpans and interior cab corners, and a fricking vintage air heater/defroster combo..... the hoses are run horribly, but it works like a dream.

that pretty much all i know so far.

vile - it was bogging at throttle tip in.

lorne - prior to following the instructions in that video, that was pretty much the case, it had to warm up 15 minutes or so, or it would bog horribly, if not just die.

it now runs MUCH smoother, i havent tried flooring it from a dead stop yet, but highway acceleration is much more instantaneous now, where as it was more of a slow build up before.

i also had a problem before where it would lose momentum going up hills, theres one in particular when i leave work thats about an 8 percent up grade, and halfway up id have to drop the tranny into 2 to even make it up. id start the hill about 40-45 and by the time i topped it, id be pushing 15-20. the hills maybe a 1/4 mile in length. it isnt as bad now - i had to slow to almost 10 mph yesterday at the start because of a guy pulling out in front of me, and it accelerated to 25ish before i hit the top. would the single plane be causing fuel starvation maybe?

the passenger side exhaust manifold gasket is trashed, im putting off replacing it til i can get the chevelle headers and just doing the whole exhaust, im thinking that would also be part of the reason it still runs a little sloppy?

[Lt.Del]

Are you sure your exhaust system is not clogged, either the cat or the valve on right side exhaust manifold stuck closed?
Does the engine temp increase when going up hill? that would be a sign of clogged exhaust.   

[roadrage41]

that valve on the passenger side is the only part of the emission system still intact.

my temp gauge doesnt seem to work, it moves a little when the truck warms up, but i think it might be just because it's seeing some sort of voltage..

[HAULIN IT]

It sound to me that a carb with a properly working choke system will fix most of your issues. Lorne

[Lt.Del]

that valve on the passenger side is the only part of the emission system still intact

make sure it can freely move...it should be attached to a rod that attaches to a plunger type devise that opens when the air warms in the intake.   My dad had  a 76 chevy that we couldnt figure out why the thing wouldn't run right and finally when taking the engine apart, found the exhaust manifold valve had frozen shut.   She dont run too good that way.

[Captkaos]

... i assume its a 305, because like 88 percent of them came with 305's.

If you are talking about a 81-86 2WD you can move that percentage up to 100%.

[roadrage41]

even better, im not getting my hopes up. autozone just has a little thing in the computer system that suggests what motor you probably have, and the 305 was 88 percent.

im trying to get those chevelle headers ordered before christmas stupid expenses just keep popping up.... 

[Lt.Del]

autozone just has a little thing in the computer system that suggests what motor you probably have, and the 305 was 88 percent

I've seen those figures on the website of AutoZone, but, what that reflects is what people "choose" when they plug their info in....many simply don't know and guess their engines---88% think they have a 305.  They aren't plugged in to the General Motors data base at all.

[Captkaos]

But, ALL 81-86 C10's had 305's, the 350 wasn't an option during that time on them.

[roadrage41]

del, the thing in the exhaust doesnt move at all so its either stuck open or closed.

i gotta get that exhaust leak fixed asap anyway and id prefer to be installing the headers while doing it...... where they removed the factory heater system was cleverly patched with duct tape and its just a tiny bit leaky...... i drive with the windows down for now...