Carb Sensitive

[Slick67]

Calling the carb experts on this one. I have a 600cfm Edelbrock and after timing the engine the carb is so sensitive that if you get a finger even close to it the truck dies!??!?! I have never seen this before and am stumped maybe electrical so I grounded the engine in another spot to eliminate that. Anyone run into this before and what was the cure?

[ETsC10]

Slick, it does seem your'e getting many guesses here so lets try you in the engine forum.

Good luck!

[Slick67]

Originally Posted by ETsC10

Slick, it does seem your'e getting many guesses here so lets try you in the engine forum.

Good luck!

Thanks.

[cableguy0]

Give us more info. Where is your timing set at. Are you saying that when you move the idle mixture screws the engine dies?

[Slick67]

I have the timing set at 10 BTDC with the vacuum lines plugged. The timing light is at 36. The electric choke is hooked up. When you get within an inch of the adjustment screws the rpms drop. When you actually touch the screws it will die.

[60ratrod]

sounds like there may be a vacuum leak. do you happen to know what the engine is idling at? try adjusting the idle speed screw on the throttle arm to kick up the idle a little bit and see if that helps. on my trucks, they usually don't like to have an idle below 700 rpms or so in park. try to see what your idle rpms are and go from there. sometimes after adjusting the timing you have to adjust the idle speed screw because adjusting the timing may increase or decrease your idle speed, depending on if you had to advance or retard the ignition. retarding usually drops the idle, advancing usually increases the idle

[Slick67]

I do not have the breather on and we idled it up to about 900.....still does it. Since we don't have to even touch it to make this happen....that sounds electrical. One other thing is that it will not keep a constant idle. It will go up and down intermittenly and will not keep it's timing when we turn it off and try to restart it. I got to get a video of this, it's crazy.

[Ticker]

Originally Posted by Slick67

I have the timing set at 10 BTDC with the vacuum lines plugged. The timing light is at 36. The electric choke is hooked up. When you get within an inch of the adjustment screws the rpms drop. When you actually touch the screws it will die.

What do you mean by the timing light is at 36?

[Slick67]

Originally Posted by Ticker

What do you mean by the timing light is at 36?

It is the timing advance knob on the timing light. A reliable source said to set it at 36, this is an older Snap-On timing light.

[Ticker]

Originally Posted by Slick67

It is the timing advance knob on the timing light. A reliable source said to set it at 36, this is an older Snap-On timing light.

An advance timing light is just that - it's for checking timing advance, not static timing. It's correct to set it to 36 when you're looking to check your mechanical advance...at 3000 RPM.

Set the knob to zero and reset your timing to 8-10 BTDC for now. We can look at other stuff once that's done. Right now your timing is way the heck off....

INCREDIBLE truck btw; checked out your build thread!

[Slick67]

Originally Posted by Ticker

An advance timing light is just that - it's for checking timing advance, not static timing. It's correct to set it to 36 when you're looking to check your mechanical advance...at 3000 RPM.

Set the knob to zero and reset your timing to 8-10 BTDC for now. We can look at other stuff once that's done. Right now your timing is way the heck off....

INCREDIBLE truck btw; checked out your build thread!

Thanks for the compliments Ticker! Cool, now we are gettin somewhere. I have it at 10 BTDC right now so I'll turn the timing light down to 0 and time it from there. I also will crank it in the dark to check for any arching electrical signs. Thanks for the new path to take on this. I'll update tomorrow and hope this helps someone else.

[dznucks]

What do you mean by the timing light is at 36?

I agree that this is part of your problem. If you set your timing light to 10 deg, then line up your 0 deg mark on your balancer with the 0deg mark on your timing tab.

Do you know what your max timing is? You should really set your timing to a max of 36 deg and let this tell you what your idle timing should be.

You said the timing is moving around. Are you still seeing that now that the timing has been fixed?

[Ticker]

Originally Posted by dznucks

If you set your timing light to 10 deg, then line up your 0 deg mark on your balancer with the 0deg mark on your timing tab.

Yep, but just to clarify:

Set the timing knob to 10 and time with the balancer mark at o (TDC)

- OR -

Set the timing knob to 0 and time with the balancer mark at 8-10 BTDC

Both work fine - but don't combine 'em

Originally Posted by dznucks

You said the timing is moving around. Are you still seeing that now that the timing has been fixed?

I'm looking forward to the answer on that one as well - including the note that the timing didn't "hold" between starts. I kinda wonder about a loose hold-down...

[Slick67]

Originally Posted by Ticker

Yep, but just to clarify:

Set the timing knob to 10 and time with the balancer mark at o (TDC)

- OR -

Set the timing knob to 0 and time with the balancer mark at 8-10 BTDC

Both work fine - but don't combine 'em



I'm looking forward to the answer on that one as well - including the note that the timing didn't "hold" between starts. I kinda wonder about a loose hold-down...

We rerouted the vacuum lines, set the timing light at 0 and proceded as before. Everything seems to be in order after a little carb adjustment. I grounded my alternator and that seems to have eliminated the carb from bogging down when a finger got close to it. On the down side, we had an oil leak and determined that the 327 block has a hairline crack in the front of it at the top of the timing chain cover. The shop that built it did not magnaflux the block so it was there when they built it. Being that the truck has not had any drive time on it I doubt that I could have been the culprit. Thanks for everything on this issue and finding a solution, unfortunately the motor has to come out and another block has to be found, bought, rebuilt and reinstalled. This is a major setback and I am talking with the shop who built it tomorrow to see what they are willing to do. If the new is bad, this maybe the end of Slick67.

[Ticker]

Originally Posted by Slick67

If the new is bad, this maybe the end of Slick67.

They didn't magnaflux and pressure-test the block? Yeah...bad, bad shop

If the news is bad, PM me - I've got a bunch of parts on the shelf...

I build about 10 engines/year - I'm willing to bet we can get a bunch of pieces together. I think there's a guy on here with a 327 block, too...

Iron blocks can be welded and/or repaired, depending on the crack.

[Slick67]

Originally Posted by Ticker

They didn't magnaflux and pressure-test the block? Yeah...bad, bad shop

If the news is bad, PM me - I've got a bunch of parts on the shelf...

I build about 10 engines/year - I'm willing to bet we can get a bunch of pieces together. I think there's a guy on here with a 327 block, too...

Iron blocks can be welded and/or repaired, depending on the crack.

That is good news! If worse comes to worse I may have to ask for help. I hope the shop has another 327. I think everything in my block is fine with the exception of gaskets and rings.

[Slick67]

I did find out that they magnafluxed it, but nothing showed. Maybe they overlooked it or like they said it could be a porous area in the cast iron. The two options that they offered were try to fix it with a plug which is supposed to be permanent or replace the block and build it. At any rate they were very quick to say that it would be taken care of. Very huge stress relief! He is coming to look at it tomorrow morning and will determine what the best way to go is. Chris the owner is a motorhead and loves muscle cars so I do trust his opinion.

[Ticker]

I'll be thinking good thoughts; good that they're willing to make it right.