Engine hesitating at low cruising speeds - Team Camaro Tech
Engine General Engine Discussion.

 
LinkBack Thread Tools Display Modes
post #1 of 7 (permalink) Old May 2nd, 04, 10:57 PM Thread Starter
Senior Tech
Marc
 
Join Date: Jul 2001
Location: Belgium
Posts: 546
Post

Hi!

I just set the right timing on my mild 327 ci, @ 12 degree initial, +/- 36-37 degree @ 3500 RPM.
I didn't retuned the carb yet.

Since i set the timing, i notice the car is very hesitating under 2000 RPM, and impossible to cruise under 1500 RPM, like it is required in city traffic. In these situation i have to go out of gear and let it go on free wheel (idle).
when engine is cold, these hesitations are stronger. Like the first off idle cruise after starting is not regular at all!

Why is this?

In any other situation, the engine runs very nicely, with a strong response above 2000 RPM, and no hesitations under load.
The car starts very easely as well!

For info, i think about changing my vacuum source from ported to full manifold and see. (ported is the actual set up)
But i want you to advice first, so i don't try for nothing.

I don't think the carb may change something to that phenomenum.

Thank you

Camaro 1968, propane 327ci, Big Brake, Hotchkis, T56
Marc is offline  
Sponsored Links
Advertisement
 
post #2 of 7 (permalink) Old May 3rd, 04, 07:09 AM
Senior Tech
Matt Jones
 
Join Date: Jan 2002
Location: Renton, WA USA
Posts: 2,765
Post

What do you mean by "hesitates"?

Does your timing tab match up with your TDC mark on the balancer?

What carb are you running?

Matt Jones
Lead Mechanical Engineer
Art Morrison Ent. Inc.
Silver69Camaro is offline  
post #3 of 7 (permalink) Old May 3rd, 04, 10:10 AM
Senior Tech
Royce
 
Join Date: Apr 2001
Location: Vacaville, CA
Posts: 10,474
Post

Are you sure it is not a misfire? Try popping your hood at night and see if there are any sparks visable.

If not it sounds like it is running lean to me. You didn't really provide enough details though. Are you sure it's not pinging?

Royce (NO XQSSS) Bradley

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.

(brief sound/video clip, 3 1/2" exhaust through Borla Sportsman mufflers)
camaroman7d is offline  
 
post #4 of 7 (permalink) Old May 3rd, 04, 10:01 PM Thread Starter
Senior Tech
Marc
 
Join Date: Jul 2001
Location: Belgium
Posts: 546
Post

Hi,

I'll try to give more info.
The carb is a Holley 600cfm, the very classic type, i don't have the number in mind and don't see the car in the week. I think a 1850? with a single feed inlet.

The problem is not a misfire, i am sure.

By hesitating i mean either you have to accelalerate or decelarate but you hardly can keep the same revs.
A friend told me yesterday my gas cable might have play in the connecting rod, giving engine cough.
This is actually the word : cough.
Only under 2000 rpm. Cruising at 2500 is not a problem, there is then no coughs no more.

Now about pinging, if it does ping than it is very very small, and oddly it seems to come only at 2000 RPM at wot, in 4th gear . (because in 4th the RPM don't change so quickly and i can notice smth.)
and i can't be very sure because i have an exhaust leak (header to exhaust point) which may be the origin of the sound. the sound is very light though.

And it sound strange to me that pinging would come only at 2000RPM and not higher ?? I am sure at high revs it is OK.
Furthermore i have here only 95 octane gas and i don't think 12 initial is too much with that.

I hope this give you more informations.

Marc

Camaro 1968, propane 327ci, Big Brake, Hotchkis, T56
Marc is offline  
post #5 of 7 (permalink) Old May 4th, 04, 12:18 PM
Senior Tech
dan
 
sixd8rs's Avatar
 
Join Date: Jan 2002
Location: Westminster,Md,usa
Posts: 967
Post

Timing set at 36-37 total? Make sure it doesnt go any higher with more RPM's. If it does, that could be the problem. You will then need an ajustable vacuum advance that you can ajust to keep it from going any higher.

68 RS
sixd8rs is offline  
post #6 of 7 (permalink) Old May 4th, 04, 02:54 PM
Senior Tech
 
Join Date: Feb 2001
Location: Concord Cal. USA
Posts: 2,664
Post

Too much advance along with a little lean lowspeed circuit in the carb. Try pulling the vacuum advance off and see if it goes away. If it does you may need one of the adjustable units.
oger is offline  
post #7 of 7 (permalink) Old May 4th, 04, 11:49 PM Thread Starter
Senior Tech
Marc
 
Join Date: Jul 2001
Location: Belgium
Posts: 546
Post

OK I'll try with the vacuum advance hose out.
And i think i run a little lean too because the engine idles around 600 rpm when cold and 900 when hot.

For the advance, i am sure i have no pigging at high rpm (2500 to 5500) under load.
As i told you i have a very small noise around 2000, and it is not only at wot, but i can hear it under light accelaration.

What do you think about that? i have no experience with pinging and i don't know if it is possible it only comes at 2000 RPM?
And as i know i have an exhaust leak... i can't say. The noise only comes when riding, not at still stand.

Thanks for the inputs

Camaro 1968, propane 327ci, Big Brake, Hotchkis, T56
Marc 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