Help with engine

[TexasRed]

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?

[Redneckchevy]

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

[HAULIN IT]

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

[Redneckchevy]

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

[Redneckchevy]

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..

[81Cheyenne]

Just a long shot....have you checked to see what kind of fuel pressure you have?

[VileZambonie]

You took the EGR off? Is the gasket in place? Do you have the idle screw turned all the way off?

[Redneckchevy]

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...

[VileZambonie]

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?

[Redneckchevy]

Yea lill post a video in about an hour or so...Gotta get my kids on the bus.

[86 chevy silverado]

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.

[kawliga1978]

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.

[hogwild]

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

[Redneckchevy]

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

[autorepr]

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!