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Discussion Starter #1
hey guys, I have a question concering a new rebuilt 400 sbc
I think it might be a vacuum leak and this is where my question lies. My truck Is hard to start with choke open or closed hot or cold. as stated this is a rebuilt mildly modiefied 400 SBC edelbrock performer dual plane intake(new) used edlebrock 1405 ( rebuilt with edelbrock kit). I can get the motor running but and runs good no misses no shaking buti have to keep my foot/hand on pedal/linkage to keep it running will not idle at all. I think it mught be either a internal problem in carb, or a vacuum leak in carb to manifold, I know the manifold and engine are sealed right heard the engine run before i got it and ran/idled perfect. previous carb was 1405 also. well now that this is a long post i will cut to the question. Couldmy rebild of carb screwed been screwed up or could a vacuum leak at the carb intake gasket cause this. Or better yet should i go to bigger carb anway I hink i might be correct i will get the best performance/mileage from a 750
Thanks in advance foran and all help

Chris
 

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Are you saying that it will not idle period, cold or hot?



Make sure your using the right vacuum source for your distributor if vacuum advance equiped.



If no one set the carb up for your engine then I would suggest a couple things.

Are you sure your timing is correct and not 180 degrees out? If so..

Turn the air screw one turn clockwise, facing the carb it is the flat head screw to the right of the carb on the throttle linkage, this will give it more-less throttle / adjust idle. Try it again

Nothing improved...
Turn the idle screws on the front of the carb, two big flat head screws, all the way in, clockwise until they bottom out, then turn the screws 1 1/2 turns out, counterclockwise.

While your there choke the engine and make sure there is roughly 3/8" gap between the butterfly and choke tower.

If this doesn't improve anything then go to edelbrocks website, they used to have a on-line carb manual I believe or you could always pick up the phone and call them.

Good luck
 

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Discussion Starter #3
thanks for the reply 357

Yes it will not idle hot or cold , will run with my foot on pedal keeping it about 1200 to 1500 Rpms.but after no no throttle no idle.

I will try these tonight.

Dont think the timing is 180 degrees out but it could be. The guy i bought it from could have had that way from the beginning. when I pulled the engine from his truck it went straight into mine.
I just added my carb.

I did have the carb set up on a 350 was working correctly, and all I expected I had to do would be to fine tune it to the 400.

Thanks Again
Chris
 

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357ford,
Is 1 1/2 turns counter clockwise factory adjustments?What I mean is that how they come setup?Thanks bm
 

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75400truck


If the carb came off a running vehicle and nothing was touched, and the engine wasn't touched either. I would focus on the throttle linkage, it may for some reason be slamming shut, another option bay be to install another carb to intake gasket, just to be sure. I had a problem with my edelbrock as far as the linkage, for some reason it wanted to close all the way and kill the engine, so I had to adjust the throttle screw in some (air screw). I am with you, if they both ran fine seperately then they should operate together. Just a thought, good luck



batman09


Sure is, believe it or not I found almost 2 turns out to be the best on my stock 351w and that was using rpms and a vacuum gauge to determine the best setting(s). Please change your avatar...looking at it makes me want one.... I think I told you before, thats a nice car.
 

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357,
Is the throtlle cable supposed to be taught?(tight???)I have a tiny little bit of play in the cable.If you press down on the cable there is alittle bit of play its not completely tight.Does this question make sense?Thanks for the compliments on my nova.I've put alot of work,blood,sweat(and money) into it.If you click on my avatar there are more pics...of my interior and motor. Thanks bm
 

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batman09

Yeah I checked out your gallery the last time...I won't put myself through that torture again. :D

Your cable should be pretty firm. When I put my edelborck intake and carb on my engine, I used the supplied bracket and it was way off, I had to modify the bracket to get the cable set correctly. You might wanna see if there is room for adjustment and see if you can slide the cable back until its tight, not overly tight but to the point there is no slack. There is a chance that your not reaching wide open throttle with the go pedal completely pressed down, if there is slack at idle, a slight chance.

Something thats a good idea, check the spring that holds your carb closed/ puts tension on the cable frequently. My brother had a newer spring on his engine (no more than 3-5 years old), 468 in a s-10, he went to pass someone, and when he did the spring broke, his foot went to the floor, obviously it was stuck wide open, he broke loose at 45 mph and spun all over the place, ran off the road and did some damage to his blazer. Just wasn't enough time to react. Funny what a 50 cent part can do to a project with thousands invested. good luck
 

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Why would a slack throttle linkage prevent the car from idling? Wide open issues I agree but...

I think you have either timing malfuction or a improperly adjusted carb. Set the idle mix screws per above and doule check the timing. If it's right then try adjusting the idle screw to get your 700-800 idle speed. If you still get problems then I'd say you need to look at getting the carb remaned or at least cleaned. The engine would run really rough if at all with the dist. 180 from it's sequence. Often causing backfiring through the carb and exhaust.
 

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johnsongrass,
you're reading two different replies from different people.
 

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Discussion Starter #10
johngrass/357

I called the guy i bought it from today and he mentioned that He had to put the the advance vacuum on the Manifold, not the carb..

.... i have the carb hooked this way for vacuu hoses..... front of carb looking straight at the carb the left vacuum going to advance on distributor, the big vacuum going to hose to valve cover, hte right one plugged. on back the vacuum hose is going to the brake booster .... intake vacuum port going to trans(th400) modulator...

To my understanding that would advance the timing extremely, which might suggest he doenst have a stock cam, he said it was but i am not an expert by far, but if all is stock the timing should be 8-10 degrees Btdc with vacuum hose off advance at the distributor, then once the hose is on the will advance more not sure how much but from reading at most posts i see around 24 to 30 range. If I hook the advance hose to the manifold wouldn't the advance be around that at idle. Which i have seen with big cams in the motors. again seen not worked on. Anyway I know the motor is good had it checked out before i bought the motor, carb I rebuilt with edelbrock rebuild kit ( i am sure it was done right) but that would be a question mark..lol....everything else is good so I am going to concentrate from the intake carb gasket up. never even thought about the linkage may have completely shutting off, but that would explain it too.

Chris
 

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johnsongrass1 said:
Why would a slack throttle linkage prevent the car from idling? Wide open issues I agree but...

"There is a chance that your not reaching wide open throttle with the go pedal completely pressed down, if there is slack at idle"

I think you misinterpreted my post, if there is slack at idle then your gonna have to press the pedal farther to get it to engage, then the travel of the cable has been shortened, and won't allow the throttle to be completely open when you have the pedal to the floor. Make any sense? It was early when I wrote it. :)



75400truck


I think I caught the problem. You mentioned the previous owner ran manifold vacuum to the distributor advance canister. You ran the vacuum hose to the port farthest to the left. This is timed port no vacuum at idle, whats happening is your timing is way too low, if you connect the vacuum hose to the farthest right port you will have full manifold vacuum which will bring your timing back up to something more normal. It doesn't matter which cam is in it. I have mine set up for full manifold vacuum and its a stock camshaft. If the previous owner set the distributor up to run full manifold vacuum thats fine, they used to set cars up that from the factory, pre emissions. Plug the left port and connect it to the right, Try that and see if there isn't an improvement. Good luck...let us know how it goes
 

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That is correct.That is how I have my 1405 set up.Full manifold vacuum.it runs alot better setup that way.bm
 

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Discussion Starter #14
357 batman

I Apparently dondt know my left from my right ....lol
looking straight at the carb the advance hose is hooked to the left (Passenger side), and the right(driver side) is plugged.
Sorry for the confusion.

I didnt get a chance to work on it yet but i would bet that that the throttle linkage is the problem, no leaks at the base of carb(was able to do at least that much) so intake gasket is sealed good. one thing i didnt think about is the fuel pressure. I went from a known good working pressure for the carb, I bought a new Mech. pump for it might be to much pressure, Reading other posts other posts edelbrock is sensitive to higher pressures, looks like i going to the store to get a regulator now to rule that out too.

Thanks
Chris
 

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75400truck said:
hey guys, I have a question concering a new rebuilt 400 sbc
I think it might be a vacuum leak and this is where my question lies. My truck Is hard to start with choke open or closed hot or cold. as stated this is a rebuilt mildly modiefied 400 SBC edelbrock performer dual plane intake(new) used edlebrock 1405 ( rebuilt with edelbrock kit). I can get the motor running but and runs good no misses no shaking buti have to keep my foot/hand on pedal/linkage to keep it running will not idle at all. I think it mught be either a internal problem in carb, or a vacuum leak in carb to manifold, I know the manifold and engine are sealed right heard the engine run before i got it and ran/idled perfect. previous carb was 1405 also. well now that this is a long post i will cut to the question. Couldmy rebild of carb screwed been screwed up or could a vacuum leak at the carb intake gasket cause this. Or better yet should i go to bigger carb anway I hink i might be correct i will get the best performance/mileage from a 750
Thanks in advance foran and all help

Chris
your idle bleeds aren't working, iff all your vac hoses are correct then you have a blockage in the lower part of the carb ,

or your float level is low that it wont feed the exellerator pump chamber ,, etc etc..

Simo from aus 3 parts cut..
 

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Re: 357 batman

75400truck said:
I Apparently dondt know my left from my right ....lol
looking straight at the carb the advance hose is hooked to the left (Passenger side), and the right(driver side) is plugged.
Sorry for the confusion.


I understood you correctly. You made the comment that the previous owner ran direct manifold vacuum to the distributor. YOu made the comment that nothing has been touched. You made the comment that you connected the vacuum advance hose to the left port. IF the distributor is set up for full manifold vacuum, which you stated it was, you need to connect the vac advance hose to the vacuum port on the right side and plug the left port. Move the vac advance hose from the left port to the port on the right side of the carb and see if there is an improvement. Good luck
 

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Discussion Starter #17
thanks to all for you help

I tried all repomnses, getting good vacuum pressure, with no leaks, at all lines. Lines hooked up correct. with full vacuum to the dist. vacuum can. Adjusted length of cable throttle to tighten line, adjusted air screw, and idle screws with no avail.

My final conclusion is that there is/was more wrong to the Carb than a rebuild Kit,( gaskets and springs) could do. I have contecated edelbrock , and they think it might be what simo says, and suggest a full cleaning and rebuild.

I have decided to fo go rebuild and get new 750 edlebrock.

Again to all that help Thanks

Chris
 
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