Timing and idle RPM set up help! - Team Camaro Tech
Engine General Engine Discussion.

 
LinkBack Thread Tools Display Modes
post #1 of 7 (permalink) Old Aug 10th, 08, 11:10 PM Thread Starter
Senior Tech
Kurt
 
camsdad's Avatar
 
Join Date: Nov 2001
Location: Atwater, Ca,USA
Posts: 936
Question Timing and idle RPM set up help!

So I finally get my stroked SB fired up after several years of building up.
1st of all WOW! , and a couple of later.
All my patience seems to have paid off.

It's been about 2 weeks now since I last fired it up. Excessive work (6 days a week), couple of mini vacations, a few birthdays, list of honey do's... and yard work have kept me busy.
This idle issue has been on my mind almost every moment of the day.
I have read many other posts and still have no solution yet. Maybe I missed a post that may have helped. Been writing on this post for the last 3hrs now.
Just found one (https://www.camaros.net/forums/showth...acuum+readings) BUt I'm too tired to read anymore for now and I'm going to bed.
Mom and the kids are taking me to Monterey tomorrow for my birthday.
Oldest son wants to go on a boat to see the Whales and Dolphins.

Here's the story.
I sent my Rochester Spread Bore 750cfm Vac secondary carb off to Sean Murphy for restoration and calibration for its intended application. (Sure looks good) Throttle response is amazing. Tuning problem I am having is getting a steady idle vacuum reading. Highest vacuum reading I got was 17hg. Smoothest reading was around 15hg but the gauge bounced between (+ - 1 deg) at idle. Engine seems to like the initial timing at around 18deg. I can't get the (no load) idle RPM below 1000/1200RPM before it starts to run so rough like it is going to stall out. I have dabbled with the Air/fuel mix and timing till I had to walk away.
There does not seem to be any vacuum leak any where but I won't rule that out just yet.

What am I missing?

Should I set the carb for the best readings and then re-adjust the rockers to maybe 1/4 lash while she is running at operating temp?
Any help is very much appreciated.

Here is a basic run down of my engine setup.
385CID
10.3 compression
AFR 195 heads opened up, ported and polished a bit.
Edelbrock RPM intake
Pro Magnum 1.5 roller rockers (lash set at 1/2 turn)
Comp cams hydraulic XE274 Cam
(BTW, Valve train noise is next to non existent using Joe Gibbs BR Performance Break-in Oil)
PerTronix billet flame thrower magnetic Pickup distributor & Coil
PerTronix flame-thrower 8mm spark plug wires. Custom fit.
Bosch 7557 plugs
Holley Mechanical fuel pump 110 GPH 6.5 to 8 psi
Thorley headers ( Currently dumping into a 2" dual exhaust with Flowmaster muffs)
2.5" exhaust and Borla Mufflers on the horizon.

I did a cold compression test and here are the following psi readings.
1- 195 2- 190
3- 200 4- 190
5- 208 6- 200
7- 200 8- 200

Kurt
1969RS 14yrs into it.
383CID Lives
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
200R4 Trans, 3:42 Posi 12 Bolt Ready
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Cold ones in the fridge. Dam, there gone. BRB
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Getting closer to my goal.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
camsdad is offline  
Sponsored Links
Advertisement
 
post #2 of 7 (permalink) Old Aug 11th, 08, 12:04 AM
Senior Tech
 
Join Date: May 2001
Location: Ashby,MN, USA
Posts: 8,305
Re: Timing and idle RPM set up help!

it's possible that what you've got is thebest it's gonna get..
is the vacuum advance hooked up to manifold or ported vacuum?
if ported, try full manifold vacuum and re-set the idle speed screw and tune the mixture screws again. you have to do this little dance where you play with one mixture screw, then the other, then the idle speed screw, then back to the mixture screws- you do this until it doesn't get any better.
ideally, you want to do this with the car in drive- which means you need a helper that you can trust to not let off the brake pedal for a half hour while you are dangling over the front of the running engine with a screwdriver.
it might be a lot of time spent screwing around, but when it's right, you know it's right, and you feel like the god of all things automotive..

you don't plan sincerity.
you have to make it up on the spot.

wanna hear about 20 years ago when i was too smart to know any better?
novaderrik is offline  
post #3 of 7 (permalink) Old Aug 11th, 08, 08:10 AM
Senior Tech
Charlie
 
Join Date: May 2007
Location: Baltimore Maryland
Posts: 3,759
Re: Timing and idle RPM set up help!

Kurt, I purchased a stage 2 Q-Jet from Sean Murphy and I too am having some issues. I can get my idle to below 800rpm, but I set it to 800rpm in neutral and it drops to 650rpm in drive. Perfect, but it doesn't want to stay there. When I first start to drive off, the car runs good, but then the idle wants to drop to where I have to put the car in neutral and step on the pedal to keep it running. The car also doesn't seem to have any top end. I replaced a Thunder series 650 carb and RPM Air Gap with the SMI stage 2 and RPM Q-Jet(non Air Gap). The throttle response is good, but it has no power and the idle thing gets me. I can get 15hg of vacuum and the needle is steady as a rock. That's the highest I could get. Something caught me as funny when I turned the screw all the way in and the RPM's picked up instead of stalling the engine. I sprayed brake cleaner around the base of the carb and I didn't hear the RPM's increase so I don't think I have any leaks. I don't know. I emailed Sean and I am waiting to hear what he says. I put the Thunder back on and kept the RPM Q-Jet manifold and the engine is much much better.

Charlie Knudsen 67 Camaro RS/SS 350 TKO 600, 4.10's, AFR 195 Street Heads, Comp 270H, Rhoads Lifters, Crane Ignition, Pertronix Dizzy, Performer RPM Q-Jet, Heavily Modified Q-Jet, Hooker Comp Headers, MagnaFlow 2 1/2", 144 Decibles(Alpine CDA-7998 Head Unit, RF X7 and RF 750X Amps, MB Quart Mid's & High's, Kicker L7 12" Solo Barics)
67CamaroRS/SS is offline  
 
post #4 of 7 (permalink) Old Aug 11th, 08, 08:12 AM
Senior Tech
 
Join Date: Dec 2001
Location: Fairfield, CA
Posts: 6,246
Re: Timing and idle RPM set up help!

What happens to your timing while your engine is fading away?

Something caught me as funny when I turned the screw all the way in and the RPM's picked up instead of stalling the engine.

What screw are you turning?

"For those that will fight for it...FREEDOM ...has a flavor the protected shall never know."
Semper Fi! L/Cpl Edwin L. "Tim" Craft, B Co 3rd AT's, Khe Sanh Combat Base, February, 1968
onovakind67 is offline  
post #5 of 7 (permalink) Old Aug 11th, 08, 08:28 AM
Senior Tech
Charlie
 
Join Date: May 2007
Location: Baltimore Maryland
Posts: 3,759
Re: Timing and idle RPM set up help!

Quote:
Originally Posted by onovakind67 View Post
What happens to your timing while your engine is fading away?

Something caught me as funny when I turned the screw all the way in and the RPM's picked up instead of stalling the engine.

What screw are you turning?
The idle mixture screws.

Charlie Knudsen 67 Camaro RS/SS 350 TKO 600, 4.10's, AFR 195 Street Heads, Comp 270H, Rhoads Lifters, Crane Ignition, Pertronix Dizzy, Performer RPM Q-Jet, Heavily Modified Q-Jet, Hooker Comp Headers, MagnaFlow 2 1/2", 144 Decibles(Alpine CDA-7998 Head Unit, RF X7 and RF 750X Amps, MB Quart Mid's & High's, Kicker L7 12" Solo Barics)
67CamaroRS/SS is offline  
post #6 of 7 (permalink) Old Aug 11th, 08, 03:30 PM
Senior Tech
Steps
 
Join Date: Dec 2005
Location: New Zealand
Posts: 13,316
Re: Timing and idle RPM set up help!

That will be caused by a sudden lean ot as it runs out of fuel...same as your lawn mow, when just before it runs out of gas it speeds up the dies...
Quote:
Tuning problem I am having is getting a steady idle vacuum reading. Highest vacuum reading I got was 17hg. Smoothest reading was around 15hg but the gauge bounced between (+ - 1 deg) at idle. Engine seems to
Quote:
like the initial timing at around 18deg
. I can't get the (no load) idle RPM below 1000/1200RPM before it starts to run so rough like it is going to stall out. I have dabbled with the Air/fuel mix and timing till I had to walk away.
A stock factory engine with will have a hi vaccuum at idle, because of low overlap and duration...increase this and the idle vac will drop
(I have 13" at idle in neutral and 10" in gear)
Quote:
Do not
set timing to highest vac or rpm at idle
Set advance to max power when all in, (this is what is important) then what ever is at idle is what u have for that dizzy spec...here u are stuck with as best idle as the engine design will give.
So start at about 36 degs all in (no vac advance connected)
What is your idle timing now? and yes with a mechanical dizzy u will get a couple degs variation.
Depending what advance u have at idle will depend if u use ported or manifold vac
Early engines used manifold with the vac advance working in a different range to later engines that used ported..they also have diff centif specs.

Once u have established the idle advance, and if using manifold or ported vac, and have these connected, then use the vac gauge to establish an idle as best the engine will give at the lowest rpms it will allow.

My Spelling is not incorrect...it is creative

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Steptoe is offline  
post #7 of 7 (permalink) Old Aug 25th, 08, 12:57 AM Thread Starter
Senior Tech
Kurt
 
camsdad's Avatar
 
Join Date: Nov 2001
Location: Atwater, Ca,USA
Posts: 936
Re: Timing and idle RPM set up help!

Alrightie now.

Well the trip to Monterey for my birthday was a blast. Went out about 14 miles to see the Whales. A bit of advice.(Don't eat sea food just before you head out on the boat) My youngest son, wife, and myself ended up chumming the ocean.
I did not see the Whales but the rest of my family did. I mainly saw the back of the boat and the back of my youngest son's head as he hung over the back of the boat. LOL!

Ok, so its been 2 weeks since I last worked on my ride.
Back to my carburetor problem.
As I stated, the problem i was having was driving me nuts.(See initial post) I did not have any guidance, and if I did, I must have misplaced it somewhere.

Problem solved.

I temporary removed the TV made EZ system for now http://www.bowtieoverdrives.com/cata...php?ITEMID=221 and replaced it with a http://info.rockauto.com/Fel-Pro/Det...?60255_TOP.jpg gasket.
Idle smoothed out and vacuum reading was steady and solid. Guess I will have to get better gaskets than those that were provided with the TV made EZ kit.

Best readings I got so far is 1000 rpm Idle with 14hg vacuum @ 18 deg initial timing.
I would like to get some more vacuum but it looks like that is all I'm gonna get.
That removed any question of the quality rebuild and restoration performed by Sean Murphy http://smicarburetor.com/.

I also worked on my Bowtie Overdrives 2004R transmission http://www.bowtieoverdrives.com/cata....php?ITEMID=13 I installed a Art Carr performance TH 2004R Deep aluminum pan with a 700R4 filter as encouraged by various transmission builders such as, http://www.drwtransmission.com/thm_200-4r.htm.
That turned out AOk!

Today was a good day.

Kurt
1969RS 14yrs into it.
383CID Lives
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
200R4 Trans, 3:42 Posi 12 Bolt Ready
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Cold ones in the fridge. Dam, there gone. BRB
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Getting closer to my goal.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
camsdad 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