Hot Rod Forum : Hotrodders Bulletin Board - Reply to Topic
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine> 350 small block vortec problems, stalls out
User Name
Password
lost password?   |   register now

Thread: 350 small block vortec problems, stalls out Reply to Thread
Title:
  
Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Additional Options
Miscellaneous Options

Topic Review (Newest First)
01-14-2013 06:49 AM
cobalt327 It's very possible the modulator just isn't hooked up. There's not many GM automatic transmissions w/o a modulator (overdrives like TH700R4/2004R). I would run a vacuum line to the modualtor after it's been checked for being bad/leaking vacuum. The detent (kickdown) cable can be left disconnected if you want to shift manually. If the whole cable's missing you'll definitely want to plug the hole in the case where it enters to keep dirt and water out.

Anyway, here's info on ID'ing your transmission.
01-14-2013 03:13 AM
cdminter59
350 small block vortec problems, stalls out

Look at the transmission pan on your car. A 350 turbo has a square pan with the right rear corner cut off. The turbo 400 has a odd looking oil pan with two or three dimples on the bottom of the pan. check yours to see which one it matches. Do you have the part# for your camshaft?
01-13-2013 09:55 PM
Camaro_Nut2001
Quote:
Originally Posted by Ltsulli1 View Post
There are no vacuum lines to the trans nor cables atached to the motor/carb from the 350 turbo trans. Thanks for any input!
If this is the case you must not have a turbo. I have saw alot of rubber vacuum lines at the modulator dry rot and cause a bad leak. I would check the tee or port coming out of the intake behind the carb. Should be a rubber line running from it to a small diameter metal line that runs right down between the firewall and right side head, probably close to your trans dip stick tube, and runs to your modulator valve. Also, you should have your passing gear cable coming up on the left side running to your carb. Now some people that are in a hurry dont even bother with the passing gear cable so it may be tied up out of the way. I assume you are not running a reverse valve body so the cable should be hooked up.
01-13-2013 08:26 AM
cobalt327
Quote:
Originally Posted by Ltsulli1 View Post
This truck is strictly an off road truck it will probably never come out of 1st and or 2nd gear... Fuel milagr doesn't bother me... So can I completely get rid of or plug off vacuum advance? Will this help the truck from dying going into gear? I'm sorry I'm kinda virgin to the tuning part of things. Thanks again
You need more initial timing first. I edited my original post to include the vacuum advance. Having it might make the engine run a little better during the times you are under light throttle. If these times are rare, you can run w/o it.

If you are using a vacuum advance connected to manifold (full time) vacuum, this can cause the engine to stall if you don't have enough initial timing. When it goes into gear, the vacuum drops off. This can cause the vacuum advance to drop off as well, and you lose the timing it was supplying.

That's why I said to add initial timing- as much as the engine needs- then to use ported vacuum for the vacuum advance.
01-13-2013 07:03 AM
Ltsulli1
Quote:
Originally Posted by cobalt327 View Post
The key to making the thumpr cam behave is more initial timing. I'd start w/about 22 degrees BTDC and work up or down as needed from there.

Vortec heads only need 32 degrees total timing, not counting vacuum advance. More on setting up the timing correctly is linked to below. Until you get the timing sorted out, you're going to have a hard time w/idle quality, nozzle drip, off idle response, etc.

Use a vacuum advance limited to 10 degrees, use ported vacuum for it.

If you find you're still having a problem getting a balance between idle quality and initial advance (advance isn't helping enough), you may need to add idle bypass air.

Not all Q-jets have a threaded rear port for a power brake booster. Use a manifold port if yours doesn't. The front large vacuum port is for the PCV valve.

Carb vacuum port ID

Advance curve

You most likely do need more stall, but sort the timing out first, then see what you need if anything.
This truck is strictly an off road truck it will probably never come out of 1st and or 2nd gear... Fuel milagr doesn't bother me... So can I completely get rid of or plug off vacuum advance? Will this help the truck from dying going into gear? I'm sorry I'm kinda virgin to the tuning part of things. Thanks again
01-12-2013 07:26 PM
cobalt327
Quote:
Originally Posted by Ltsulli1 View Post
Ok man, got the truck running and idling ok..... Now we have another issue that's kinda stopping us. I tuned the carb I set the timming good it will run and stay running fine but now when I put it in gear it dies out.... I can keep it running in gear with the idle turnt up or foot on gas and keeping it running! As soon as I let off it kills. I have a correction it is a comp thumper cam NOT a mother thumper. We were told we shouldn't have to have a stall with this cam. Are there any tricks am I missing something? There are no vacuum lines to the trans nor cables atached to the motor/carb from the 350 turbo trans. Thanks for any input!
The key to making the thumpr cam behave is more initial timing. I'd start w/about 22 degrees BTDC and work up or down as needed from there.

Vortec heads only need 32 degrees total timing, not counting vacuum advance. More on setting up the timing correctly is linked to below. Until you get the timing sorted out, you're going to have a hard time w/idle quality, nozzle drip, off idle response, etc.

Use a vacuum advance limited to 10 degrees, use ported vacuum for it.

If you find you're still having a problem getting a balance between idle quality and initial advance (advance isn't helping enough), you may need to add idle bypass air.

Not all Q-jets have a threaded rear port for a power brake booster. Use a manifold port if yours doesn't. The front large vacuum port is for the PCV valve.

Carb vacuum port ID

Advance curve

You most likely do need more stall, but sort the timing out first, then see what you need if anything.
01-12-2013 05:49 PM
Ltsulli1
Quote:
Originally Posted by cdminter59 View Post
I forgot about your vacuum lines. If I remember correctly, the Q-jet has a threaded fitting on the backside of the carburetor. This is where the vacuum line from the brake booster goes. The brake booster should have its own vacuum port, do not tee anything else to it. There should be a 3/8 port on the front of the carburetor for the PCV valve. You should have a vacuum port fitting that screws into the manifold behind the carburetor for your vacuum to modulator valve on the transmission. There will be other vacuum ports on the front for the distributor vacuum advance. Just remember the ports that have vacuum at idle are manifold vacuum and the ports that don't are ported vacuum. I have a picture from a website that might help you. Look at post #7. Good luck. PALEEZE help me hook up my QuadraJET and vaccuum stuff. - THE H.A.M.B.
Ok man, got the truck running and idling ok..... Now we have another issue that's kinda stopping us. I tuned the carb I set the timming good it will run and stay running fine but now when I put it in gear it dies out.... I can keep it running in gear with the idle turnt up or foot on gas and keeping it running! As soon as I let off it kills. I have a correction it is a comp thumper cam NOT a mother thumper. We were told we shouldn't have to have a stall with this cam. Are there any tricks am I missing something? There are no vacuum lines to the trans nor cables atached to the motor/carb from the 350 turbo trans. Thanks for any input!
01-05-2013 07:53 AM
Ltsulli1 Thank you for that info
01-04-2013 10:41 PM
cdminter59
350 small block vortec problems, stalls out

I forgot about your vacuum lines. If I remember correctly, the Q-jet has a threaded fitting on the backside of the carburetor. This is where the vacuum line from the brake booster goes. The brake booster should have its own vacuum port, do not tee anything else to it. There should be a 3/8 port on the front of the carburetor for the PCV valve. You should have a vacuum port fitting that screws into the manifold behind the carburetor for your vacuum to modulator valve on the transmission. There will be other vacuum ports on the front for the distributor vacuum advance. Just remember the ports that have vacuum at idle are manifold vacuum and the ports that don't are ported vacuum. I have a picture from a website that might help you. Look at post #7. Good luck. PALEEZE help me hook up my QuadraJET and vaccuum stuff. - THE H.A.M.B.
01-04-2013 10:14 PM
bygddy
Quote:
Originally Posted by Ltsulli1 View Post
When you say plug all the vacuum ports you do mean everything right? Vacuum advance and vacuum for brake booster? Everything on the carb? Just wanted to clarify thank you
Yessir.....
01-04-2013 08:39 PM
Ltsulli1 When you say plug all the vacuum ports you do mean everything right? Vacuum advance and vacuum for brake booster? Everything on the carb? Just wanted to clarify thank you
01-04-2013 08:30 PM
Ltsulli1 Ok I'll give that a shot within the next few days thanks for your help I'll let you know how things go!!!
01-04-2013 08:22 PM
bygddy
Quote:
Originally Posted by vinniekq2 View Post
Plug all the line(temporarily)set timing for 35 total at 3k.turn idle screw up to 1400 rpm( w/e it takes to keep running. adjust carb,turn down idle . check all tune up specs and continue down until it idles at 850 ish.
test for vacuum leaks with carb cleaner or other aerosol spray.
Didn't even see this Vinnie lol....oops.....
Yep....this will work....
01-04-2013 08:20 PM
bygddy
Quote:
Originally Posted by Ltsulli1 View Post
What about re tuning carb to have no choke I mean we can get it to stay running to warm it up. I can hold the pedal at let's say two grand and it will run there constant! But when you let off it will idle for about 5 seconds and it tries to stay idling but eventually dies out. So still leaning towards choke?
Its not going to be a choke issue, I rarely have a choke on any of my junk, get it started, get it to 1500ish for a minute or 2, should idle down and stay running...and that's in chilly Canada climate and with the heat risers blocked. The mother thmpr is a pain in the ***, ask me how I know....get all the vacuum ports plugged, get your base timing to 24, adjust idle down to 800, and see what it does....but yes, this is after you have plugged everything and confirmed no vacuum leaks....if it runs decent, and stays running, then we can worry about where all your vacuum should be routed. That cam is going to want alot alot of initial...
01-04-2013 08:02 PM
Ltsulli1 What about re tuning carb to have no choke I mean we can get it to stay running to warm it up. I can hold the pedal at let's say two grand and it will run there constant! But when you let off it will idle for about 5 seconds and it tries to stay idling but eventually dies out. So still leaning towards choke?
This thread has more than 15 replies. Click here to review the whole thread.

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


All times are GMT -6. The time now is 10:34 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.