Vacuum question - Team Camaro Tech
Engine General Engine Discussion.

 
LinkBack Thread Tools Display Modes
post #1 of 7 (permalink) Old Sep 19th, 04, 10:28 AM Thread Starter
 
Join Date: May 2004
Posts: 9
Post

I know it's been recommended on here to run the vacuum off of the manifold versus a ported source. First of all, I tried to get a vacuum reading from my manifold source. When I hook the vacuum guage up, the car won't even idle. I have to keep the rpm's around 2,000 to keep it running. What does this mean if anything?

Thanks!
69CamaroDave is offline  
Sponsored Links
Advertisement
 
post #2 of 7 (permalink) Old Sep 19th, 04, 12:34 PM
Senior Tech
Bob
 
Join Date: Dec 2000
Location: Ct.
Posts: 1,145
Post

What are you disconnecting to hook up the vacuum gauge? There should be no difference in the way the car runs with the gauge hooked up to the manifold versus normal. It sounds like you are leaking through the gauge possibly.

Bob
Garnet Red 69/SS396/TH400/355 Posi Sold
'02 triple blk Vette Vert. now
94 HD Dyna Wideglide
phel69 is offline  
post #3 of 7 (permalink) Old Sep 19th, 04, 03:22 PM
Senior Tech
Jim
 
Join Date: Nov 2002
Location: Ontario & Oceanside CA.
Posts: 1,321
Post

Dave
you're probably unhooking the vacuum advance to hook it to your gauge, and the timing is too retarded to idle. Put a TEE in the line and hook up the gauge with the vacuum advance hooked up. Or if you have another manifold vacuum port, use that. You'll get a reading then. There are many opinions regarding vac/adv. Some engine combonations will not run well or won't perform the way you want them to using manifold vacuum. My car for example, will fall flat on it's face off idle with manifold vacuum hooked up. It idles smoother with the advanced timing but the total timing while cruising is too much for the engine combo i'm running. I set my total timing all in at 3000 rpm 32* and wind up with 12* initial which allows the engine to perform well from idle on up. I use ported vacuum (a maximum of 10*) a total of 42* to allow for better mileage and part throttle cruising response and it works well. I won't argue with anyone about the manifold versus ported vacuum opinions because it's pointless. your car may run well either way if the engine responds well to it. I have tried every combonation with my engine and have found that it runs best and responds best with ported vacuum. try it both ways and go with what works best.
Hope this helps
Jim
GMJim is offline  
 
post #4 of 7 (permalink) Old Sep 20th, 04, 04:58 AM
 
Join Date: Aug 2004
Posts: 41
Post

Guys, I posted the note from by bro-in-laws house. That's why it says 69CamaroDave. I hooked the guage directly to the manifold port. Although I still had the vacuum adv hooked up to the ported source. Was this my mistake? Should I unhook the vac adv from the ported source, then Tee that line into the manifold port?

Thanks!
Oldyeller69 is offline  
post #5 of 7 (permalink) Old Sep 20th, 04, 02:34 PM
Senior Tech
Jim
 
Join Date: Nov 2002
Location: Ontario & Oceanside CA.
Posts: 1,321
Post

Having your vac can hooked to a ported source won't do anything at idle. (your sure which is which?) If you put a TEE in line with the gauge at a manifold vacuum port, it will allow advance to keep the engine running while you read the gauge. Unplugging the vac/adv. while the engine is running will allow the timing to retard and depending on where you have base timing set can cause it to stall. This is tough to do (diagnosing this problem) on the computer. It might be a good idea to get somebody that can help you that understands this subject a little more? Timing can be a confusing subject even when you understand it, and much more confusing when you don't.
Jim
GMJim is offline  
post #6 of 7 (permalink) Old Sep 21st, 04, 05:34 AM
 
Join Date: Aug 2004
Posts: 41
Post

Thanks Jim. Just to make sure, the manifold source is on the manifold and the ported source is on the carb. Correct? I did unhook the line from the vacuum canister to the carb. I kept the hose connected to the canister, then Tee'd it to the manifold source and the vacuum guage. The engine still would not idle. Should I advance the timing any? Right now it's around 8 BTDC.

As you can tell, I'm trying to learn. So some of my questions might make you scratch your head. I appreciate your help and everyone elses help that I get on this board. I do recognize there are certain issues I should have a professional mechanic address.
Oldyeller69 is offline  
post #7 of 7 (permalink) Old Sep 22nd, 04, 06:06 PM
Senior Tech
Jim
 
Join Date: Nov 2002
Location: Ontario & Oceanside CA.
Posts: 1,321
Post

Sorry for not getting back sooner. Some carbs have many vacuum sources. Usually the manifold vacuum ports are low and on the throttle plate which is at the bottom of the carb. Ported vacuum ports are usually above the throttle plates. It sounds like the gauge is leaking like Bob suggested in the earlier post. Eight degrees initial timing using a vacuum advance shouldn't be too much. Your vacuum can may be advancing your timing quite a bit. Check the timing without the vac adv connected. It should idle at 8 degrees without a problem. You may have to turn up the idle a little. Then connect the vac adv and recheck to see how much you have. Try this and post your findings. It's late here and I gotta go. I'll check tomorrow to see what you've found and try to help further.
Jim
GMJim is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user 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.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



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
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome