73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Redneckchevy on January 26, 2008, 02:19:14 pm
-
Just replaced throttle return spring...Every time i turn truck on its as if im flooring it...Wont kick down....Spring works...Throttle plates are closing....I dont get it
Cant see any cracks or nothing...Secondarys are closing....Idle is set so the engine plates are 100% closed...
-
did you knock the vacuum hose off of your brake booster?
-
nope every thing is on right...Just replaced the spring and she went crazy on me....Every thing looks to be fine...Its crazy...Put my hands over carb..Started Running slower but chugged and stayed at about 4000rpm
-
Take the air cleaner off and take the spring back off, now with the engine off make sure the throttle is working correctly. Sounds like you have a vacuum leak or your spring is opening the throttle not closing it.
-
Redneck, What kind of carb is it? It is running @ about 4000 RPM with the throttle blades closed? Did you remove/change the bracket for the return spring? Possibly sucking air through a open hole? Will try to help, Lorne
-
Yea every thing is working..spring is closing plates...its a Holley 80457
I dont have any emission stuff...Just 1 vacuum port for my advanced and another for brake booster..every line is new...I dont get it.
-
You're positive no vacuum lines fell off? plug your brake booster hose. If you look straight down inside the carb (engine off) you can physically see the throttle plate is closed?
-
yep its closed..no lines are off..i even took all pressure of the pump acuater and it still revs high...And its a stumbling high...Not a smooth rev...Flaps are closed..No pressure on the fuel acuater...But yet its reving ...WTH im about to junk it...or buy the truck down the road for 2000 with a 454 c30
-
Well i give up...i can get a 5.0L 4BBL out of a 85...Any one know if thats a 350 or 305?
-
Redneck, A 5.0L is a 305. I know Vile asked, but are you looking down in the carb or looking at the linkage on the side? Something is goofy here, do you have a tach & see it at 4000 or are you just implying "it's really revving"? That is way to high for even a large vacuum leak, there has to be fuel going in with it. Please explain : "You say every line is new" Have you run this engine since you put on the hoses? Did you try pulling off the hose going to the distributor & plugging it? Why did you change the return spring? There are only a few things that could do this (if it is really @ 4000, just the carb, I would guess) Don't give up, this has to be simple. The motor itself is not at fault, it is just reacting. You need air & fuel to increase the RPM's. Just trying to help ya out, Lorne
-
Well i replaced all vacuum lines a week ago..Replaced pcv valve..And valve cover filter...I replaced the throttle spring cause the old one was week I have a Actron digital timing light that has rpm reader...Um yea i did as ville said...I climbed up on the truck and looked down plates open and close..Back plates open and close when i open the secondaries...Every thing was running great...I installed the spring and went to start it and its just revving out of control i give it gas and no difference....But the peddle does open it and the spring does close it...Only other thing i did to the truck is remove the header block off..the thing at the end that will close it in cold weather...I made sure it was free flowing...Im lost...Iv been out there all day searching ...Put my hands over the carb and made it air tight ..best that i could..and it still ran high and rough
-
Redneck,
Unless the throttle plate is open you have a vacuum leak. The only thing that can make your gas engine rpm increase is more air being let inside the intake. Pull the throttle cable off and return spring off. Manually work the throttle and make sure it closes. Try running it for a second with the throttle manually closed with them off and see what it does. Is the carburetor loose? If all else fails pull the carb off and see if the base gasket is in tact.
-
yea i did what you said...The plates are closing im going to take the carb off tomorrow and replace mounting gaskit ...i just dont understand..Every thing was fine till today i think tomorrow ill make a video of it and post it...
-
what line is your PCV valve hooked up at? Did you have a backfire? Maybe your powervalve got fried? But it still sounds like there is a vacuum leak.
-
No i just rebuilt carb...It was running fine..Went out to start it then this had to happien....No back fire..pcv is hooked up to front of carb...I cant find the leak...I wounder if a blocked header could do this?
cause i had that thing on there that will close of the header to help warm up the engine fall of the other day..it wasnt hooked up to nothing but the valve might of stuff..blocking the right side header
-
Do you have an EGR valve on your intake manifold? You could spray some carb cleaner or starting fluid around the carb mounting areas and perhaps the intake? Do you have a choke?
-
Nope egr was removed...Blocked with a plate of 1/4 inch steel and High temp Gaskit...That i cut myself...And the choke is electric and it opens up fine..I almost think that its just pouring fuel in....cause when i start it its wide open ..and when i floor it it just smooths out...cause more air is getting in
-
Red, The heat riser valve stuck/blocked header could not cause this, if anything it would make the motor run poorly ( ie.. a bad catalytic converter plugged, the motor wont rev up). That thing has to be taking on a fair amount of air/fuel. How much have you drove it since you rebuilt the carb? I wonder if the carb is leaking fuel under the throttle plate & it is just a coincidence it started when you changed the spring. 4000 RPM seem like allot without some good amount of airflow. I see what your saying about the motor smoothing out when you open the butterflies, like your fixing it from "loading up" some. Do you know someone you can borrow a carb from to test? It likely is the problem. Keep us posted & Good Luck, Lorne
-
I drove it maybe a cpl times since i replaced it...But i got another rebuild kit..ill install that tomorrow ..if i have to..I just do not get it...It was running top notch...Im going to make a video of it tomorrow tho...So every one can see and here what my problem was
-
Well im still lost..Rebuilt carb..Nothing...Replaced the spacer gaskit..Nothing...Checked to see if carb or spacer was warped...nothing...Checked for any signs of a cracked head or intake manifold...Nothing...Went to start truck...Running wide open....
Im just not getting this....Its nothing like a vacuum leak..I should no Before it started running like this i i took the Egr off and let it run...And it wasn't running this fast..I mean this is running wide open...Plates are all closed...And i mean the Rpms are up ...or i would say it was a cracked header or something just making it loud...Im at my wits end...I dont no if i should junk that engine and buy a new one or anything...Iv never seen nothing like this before..
-
Just a long shot....have you checked to see what kind of fuel pressure you have?
-
You took the EGR off? Is the gasket in place? Do you have the idle screw turned all the way off?
-
yeap...Egr is blocked with a 1/4inch steel plate...With a new gaskit...And the idle is backed off...Holly tech said its not my carb...That for it to gain that much rmp...Its probably a cracked manifold...I dont see a crack anyware...
-
You've plugged off all of your vacuum hoses, EGR is bypassed, are sure the carb is set correctly and have no visual air leaks but it idles at 4,000RPM. Unless it sucked an intake gasket I'm a little curious. Can you take a video?
-
Yea lill post a video in about an hour or so...Gotta get my kids on the bus.
-
Whats the latest on your problem? Just to be clear are we talking a square bore or spread bore carb? What is this spacer that your using? Are you 100% sure your gaskets and this spacer is all matching up properly? Are you mixing gaskets or spread bore to square bore adapters, anything like that? Your prob is big enough, it seems like it should be right in front of you but you cant see it. Look at everything with a fine tooth comb, chances are your just missing something. ;)
-
Two things to check, the header block off you are referring to, did that originally have a vacuum line attached? The second thing to check it to make sure the rpm signal that you are getting is accurate. I know that some timing lights have to be set up for a V-8 or V-6, whichever you happen to be working on.
-
check intake gasket at back of engine, for that engine to run at 4000 rpm it must be getting air from somwere.spacer under your carb isnt a nos plate is it ? this sounds just like a keaking nos soliniod to me
-
I dont no ....I keep looking every day...I still have to take a video of it..But i think im just going to replace the engine :/ Its a V6 and im trying to find a 454
-
STOP,TAKE A BREATH. 1st---If the throttle plates, NOT the choke plate, are closing then it IS sucking air from somewhere else. No ifs ands or butts. No air=no rpm cut and dry. An engine has to inhale then exhale. The throttle plates are what controls the amount of inhale. Air IS bypassing the plates. Plug off all vacuum ports on the carb at the carb, and at any intake ports, start the engine and see if that isolated the leak. Plug EVERYTHING, distr. advance, brake booster, heater control, EVERYTHING right at the vacuum source. If it's still happening you have all the seals between the carb to intake valve as a possible leak. A Holley carb did not come on a chevy truck from the factory so how is it attached to the engine? An aftermarket intake that accommodates a Holley directly? What gasket for this intake? Looking up 1 for the truck yr,model and engine by the book will get 1 for a Q-jet. Are you using an adapter plate between the stock Quadrajet intake manifold and the Holley carb? An adapter plate needs a square bore Holley gasket between the carb and the plate, then a Q-jet gasket between the plate and the stock intake. The next source for a leak are the intake gaskets. Put a wide strip of Saran wrap along both sides of the intake where it meets the head when you start the engine see if the wrap pulls into the gap.
2ND--- You have to have fuel for the engine to run. No fuel no rpm period. The engine gets fuel from a carb by sucking air thru the carb venturis. This creates a vacuum drawing fuel in. If air is being sucked in thru some where other than thru the carb bores then it is not sucking fuel thru the venturis. A carbed engine with a vacuum leak = to much air and not enough fuel, that is way they won't idle well and stall. A fuel injected engine sees the leak and compensates for it automatically by adding pressurized fuel thru the injectors. Injected engines with more air gets more fuel electronically and=high uncontrollable rpm. Something is wrong inside the carb. The fuel pump is forcing fuel thru the carb and into the engine. The float is not set right or the needle fell out of the seat.
Remember the exhaust only exhales what the engine inhales. If it's restricted it won't exhale anything. If it's wide open it exhales everything loud as heck.
You likely have 2 problems working your last nerve!
1 other possability is the throttle lever is somehow hitting the air cleaner and being held open when you pump it to start the engine. When you take it off to see what's happening it lets go of it and closes the plates.
I know this reply is long but hopefully it helps!
-
Well thank u for that...Im starting to think its the spacer/adapter I never torqued it down ...I only torqued the carb on....And in ohio it gets hot then cold in the matter of a few hours....Could the fact that its aluminum on steel have anything to do with my problome?
-
Could. Get that thing sealed tight.
I'm hip to our Ohio weather. I'm in Dayton, where are you?
-
Sorry guys if ya don,t like ohio weather wait til tomarrow it'll be different. Never the same two days in a row it seems like.
-
Akron....Ill replace them tomorrow and see what it does
-
did you find the problem yet?
-
OK so i let the truck sit for a while..While i got the dash done...No I'm back to the engine...OK the Coolent is a Lil low...Oil smells like gas...The front of the engine under the intake manifold is a Lil wet looks like coolent........And engine still runs wide open...SO...Bad heads and bad gaskits?
-
If the throttle plates are closed and you have the correct carb base gasket on there, then you have a vacuum leak from another source for it to be running at such high rpm.
-
Redneck, The heads/gaskets are not going to be the problem to your running at full throttle, there may be a leak or something, but it is not the source of this problem. Go back & read what everyone has posted & think through it carefully. As autorepr,86 Silverado, Vile, Me & others have mentioned, This is a simple problem that your looking at & not seeing, Period! Do you know anyone you can borrow a Q-jet from? Trying to eliminate your spacer rig from the mix. As already said, check the gaskets (between the intake-spacer & spacer-carb for an area that isn't sealing). One thing I would like you to do, unhook the Red "hot" wire on the distributor,unbolt the carb, find a couple sockets to use as spacers over the carb bolts/studs (so you can see the bottom of the carb between the intake) have someone crank the engine. Is there fuel coming out? If you were in the next town I'd come over & help you sort this thing out. Where is Barberton? Lorne
-
Barberton is next to akron...So if the intake manifold is leaking it wouldnt make it idle that high? So it would have to be above that as in the Spacer or carb gaskit?
-
Redneck, What I'm saying is the coolant leak can not make your engine run at high RPM. Now a crack into the air passages in the intake (air leak/vac. leak) can contribute to this RPM problem, however to the extreme you are talking about, I feel there has to be additional fuel involved here also. Lorne
-
Ill check it out better.....The coolent is leaking from the front...Under the goose neck...But not from it.
-
Redneck take some pix of your carb sitting on your engine for us. Both sides, front and back.
-
Ok...Side to side front to back..Let me no if u see somthing
(http://i261.photobucket.com/albums/ii69/chevroletcustomdeluxe/DSC00004-1.jpg)
(http://i261.photobucket.com/albums/ii69/chevroletcustomdeluxe/DSC00003.jpg)
(http://i261.photobucket.com/albums/ii69/chevroletcustomdeluxe/DSC00002-1.jpg)
(http://i261.photobucket.com/albums/ii69/chevroletcustomdeluxe/DSC00001-1.jpg)
-
(http://i6.photobucket.com/albums/y228/Sabaka454/redneck.jpg)
-
nevermind, Vile posted that before I got to it...
B)Is there a gasket under that adapter?
-
That my good man is a Vacuum port .. i think its just a shallow hole with some threads..For the option of drilling it...But im going to check that right now!
-
Redneck, One thing that caught my attention. Back on reply #10, you said "the back plates open & close when I open the secondaries". That being a vacuum secondary carb, the rear plates should not move with the vehicle sitting still. Please explain in more detail. I can see a gasket under the spacer to manifold, but how about between the carb & spacer? How about some pictures now from a little farther away? Lorne
-
Ok..So i went back out...Took carb and adapter off....both gaskits looked good...But i replaced them...And it idles now!!!...But it runs like a horse with a broken leg...Rough idle...Going put put put....Idle is a lil higher then it should be...And the screw is backed out...Now it was running fine before the gaskit failed...Any idea on why its running so bad now?
About the Secondaries...I manual open them by pushing the actuator up while turning the linkage
-
Good! It sounds like your making headway now. Lorne
-
Is there suction at that threaded hole in the back of your adapter when it's running? Did you put your finger over the hole?
-
no suction...Its a dummy hole..wish it wasn't i could use it...Later on im going to set my vacuum again...Then try to time her some and see if that will help some....Then im going to let it run and re check the torque on the carb bolts....