Fine tuning setup on a SBC 350

[scottastew New Member Find all posts View Profile Close scottastew]

I installed the pro-flo 4 last year on my 1985 GMC K1500 but I could never get it dialed in right and it kept stalling during idle and shifting into gear. It got me pretty frustrated and I didn't really mess with it over the past several months. I'm now trying to get my truck back up and running. I made some fuel adjustments in the settings hoping and got my IAC down to a manageable level, but I'm still stalling when I shift and if I leave it idling. Can someone take a look at my gauge settings and see if anything stands out as a problem? Thanks. Truck guage.jpg Truck guage.jpg

[CMerchant Member Find all posts View Profile Close CMerchant]

Three things I'll note:

Your AFR seems super rich at idle. Would likely be better suited in the hight 13's.

Also your battery voltage seems pretty low. I understand both your fans were on but still. I don't know if you charging system would have an connection with your issue but just pointing it out.

Next your fuel pressure seems high considering you're pulling 21+" vacuum. Is your fuel pressure regulator vacuum referenced?

So I just want to clarify - you've NEVER been able to get it into gear without it stalling at any temperature?



Please give some more info on your setup:
Cam specs
Map loaded
injector size/color
Timing specs as entered into the tablet

[2700 Cast Super Moderator Find all posts View Profile Close 2700 Cast]

Idle spark is too low ....try 19 -20 degrees.

More data will help====>

What engine?
Vehicle make & model?
What MAP # is it on?
Fuel pressure ?
Hot engine idle vacuum?
Injector size ?
HP level ?
Spark control settings ?

[scottastew New Member Find all posts View Profile Close scottastew]

Thanks both for the quick response.

CM-I'll get more information when I get home tonight. But to clarify, I can get it into gear if I get on the throttle a bit. I've driven it around the neighborhood, but it has stalled when I slow down and get under 5-10mph. I wonder if my battery isn't sufficient?

2700-I'll try that and get the other info and later and post it.

[scottastew New Member Find all posts View Profile Close scottastew]

Three things I'll note:

Your AFR seems super rich at idle. Would likely be better suited in the hight 13's.

Also your battery voltage seems pretty low. I understand both your fans were on but still. I don't know if you charging system would have an connection with your issue but just pointing it out.

Next your fuel pressure seems high considering you're pulling 21+" vacuum. Is your fuel pressure regulator vacuum referenced?

So I just want to clarify - you've NEVER been able to get it into gear without it stalling at any temperature?



Please give some more info on your setup:
Cam specs
Map loaded
injector size/color
Timing specs as entered into the tablet

CM-I've got a basic GM 350 crate motor, so I've chosen the stock CAM setting. I the white fuel injectors. I tried to mess with the AFR at idle yesterday, but the higher I went with the number, the quicker it would die. If I dropped it to 12.0, it would stay idling longer but still not sound great.

I'm using the Edelbrock sump/fuel system setup so I'm not sure if that is considered to be vacuum referenced.

I'll admit I struggled at first with timing and I couldn't get it to start after the initial install. I was having a hard time finding TDC and ended up on the phone with Edelbrock a couple times to figure this out. I thought I figured it out with the hose and balloon method to figure out my first cylinder compression stroke and after fiddling with that the truck started up fairly easy, but has never been able to idle for a prolonged long time or go into gear without adding stepping on the gas pedal a little. I've driven it around the block a few times but always in fear that I was going to stall out. Again, It's been over a year since I messed with the timing. Do you think my symptoms could be related to the timing being off?

[CMerchant Member Find all posts View Profile Close CMerchant]

CM-I've got a basic GM 350 crate motor, so I've chosen the stock CAM setting. I the white fuel injectors. I tried to mess with the AFR at idle yesterday, but the higher I went with the number, the quicker it would die. If I dropped it to 12.0, it would stay idling longer but still not sound great.

I'm using the Edelbrock sump/fuel system setup so I'm not sure if that is considered to be vacuum referenced.

I'll admit I struggled at first with timing and I couldn't get it to start after the initial install. I was having a hard time finding TDC and ended up on the phone with Edelbrock a couple times to figure this out. I thought I figured it out with the hose and balloon method to figure out my first cylinder compression stroke and after fiddling with that the truck started up fairly easy, but has never been able to idle for a prolonged long time or go into gear without adding stepping on the gas pedal a little. I've driven it around the block a few times but always in fear that I was going to stall out. Again, It's been over a year since I messed with the timing. Do you think my symptoms could be related to the timing being off?

Possibly. If you have no way to verify you dropped the distributor in at 12*BTDC then you're whole set up is going to be off. That's The most critical step in the process. Find TDC. Then find 12 BTDC and then take the cap off the distributor. If it's not pointing directly at the #1 spark plug post you need to pull the dizzy and reset it. From there I'd reload a NEW calibration and start over.

Also just going back to my first reply - is your fuel pressure regulator vacuum referenced? And is your charging system up to snuff?

I addition if you have a stock 350 with 29lb injectors you should probably be on map 5006 which is a 43 PSI map. You need to lower your fuel pressure and get on this map when you reset it.

And do what 2700 Cast suggested - needs more idle timing in the tablet.

[scottastew New Member Find all posts View Profile Close scottastew]

Ok, so I adjusted timing a bit and also drained old gas and put new gas in the tank with an additive. I thought it may have fixed my issue of running rough. I drove to my brothers house about 2 miles away, let it idle over there for a few minutes and then on my way home it started to run crappy again. I barely made it home because it was wanting to stall at stop signs. Here is a video of when it is running rough with some screenshots of the settings.

[scottastew New Member Find all posts View Profile Close scottastew]

I don’t know if my fuel system is vacuum referenced. I installed the Edelbrock fuel sump system. Also, I can’t see any option to limit fuel pressure to something other than 58. The MAP I have loaded is 43, but I can’t change the actual pressure once I’ve got it loaded. I think my charging system is adequate, although my battery is probably on the lower end of power necessary...

[ddsmith Member Find all posts View Profile Close ddsmith]

I don’t know if my fuel system is vacuum referenced. I installed the Edelbrock fuel sump system. Also, I can’t see any option to limit fuel pressure to something other than 58. The MAP I have loaded is 43, but I can’t change the actual pressure once I’ve got it loaded. I think my charging system is adequate, although my battery is probably on the lower end of power necessary...

If you are running the Edelbrock Fuel Sump then it has an adjustable regulator on it. That is also where the vacuum hose gets attached to provide vacuum reference. If you did not install a vacuum line from your manifold to that nipple, then it is not correctly setup. To adjust the regulator, loosen the lock nut and adjust the regulator to get 43 psi with the engine running. Then tighten the lock nut. Then get a vacuum hose and install it from the manifold to the nipple and you will be setup correctly.

[scottastew New Member Find all posts View Profile Close scottastew]

If you are running the Edelbrock Fuel Sump then it has an adjustable regulator on it. That is also where the vacuum hose gets attached to provide vacuum reference. If you did not install a vacuum line from your manifold to that nipple, then it is not correctly setup. To adjust the regulator, loosen the lock nut and adjust the regulator to get 43 psi with the engine running. Then tighten the lock nut. Then get a vacuum hose and install it from the manifold to the nipple and you will be setup correctly.

Oh, thanks for sharing this. Sorry, it’s been over a year since I installed it so I’m forgetting things. I did NOT install it with a vacuum hose. I’ll adjust the pressure and report back. Thanks again.

[ddsmith Member Find all posts View Profile Close ddsmith]

If you have the vacuum reference hose installed now. Disconnect it at the sump and plug the hose. Adjust the regulator and then reinstall the hose at the sump. If you are pulling a good vacuum it will lower your fuel pressure noticeably. Did you installed the vent hose from the sump back to the tank? I have seen this being the biggest problem with the install other than heat related fuel issues.

[scottastew New Member Find all posts View Profile Close scottastew]

If you have the vacuum reference hose installed now. Disconnect it at the sump and plug the hose. Adjust the regulator and then reinstall the hose at the sump. If you are pulling a good vacuum it will lower your fuel pressure noticeably. Did you installed the vent hose from the sump back to the tank? I have seen this being the biggest problem with the install other than heat related fuel issues.

DDsmith-I did not have the hose attached. I have adjusted the fuel pressure to 43 and will install the hose now. Would you look at this picture and see if this is the right spot for that fuel vacuum hose? Is is on the side of the IAC sensor. There is something installed there now so I will just T connect it if that is the right spot.

[scottastew New Member Find all posts View Profile Close scottastew]

When I first installed the vent hose, I used a 1 way check valve because I was worried about fuel traveling back up into the sump for some reason. Now that I think about it, I’m not sure why that would ever happen. I removed that valve tonight so it is just vented straight back to the fuel tank with no valve in the way. Maybe that was causing an issue...I also installed the fuel vacuum reference hose and adjusted the fuel pressure to the correct amount.

I tested it out with another test drive and I am cautiously optimistic that one or both of these things solved my problems. It ran very well (other than a slight hesitation when accelerating from a stop).

Thank you three who all helped me get this figured out. I’ve been ready to rip it all out and go back to a carb, but turns out it’s just my own dumb fault for not paying enough attention to the instructions. I plan on testing it more tomorrow and make sure we are good. Felling good tonight!

[Stryker New Member Find all posts View Profile Close Stryker]

Small block Chevys like more advance at idle which will help with your idle and stumble also. 2700Cast recommended you set your idle advance at 20. My experience with this system on 2 separate SBC's is that 20 to 22 is the optimal idle advance. Also idle speed on mine have been best at 850 to 900 rpm.

[scottastew New Member Find all posts View Profile Close scottastew]

Is it normal for the fuel pressure to be lower after installing the vacuum reference hose? It dropped to the mid 30s. Do I need to adjust the pressure again so it is 43 with the vacuum hose attached?