Ignition timing oddity on chassis dyno - Page 3 - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #31 (permalink)  
Old 04-09-2012, 05:14 PM
Registered User
 
Last photo:
Join Date: Jan 2012
Posts: 43
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
to 10

Hey 10

Check out these bowls out.of course you have look at them upside down



2x4`s
Attached Thumbnails
Click image for larger version

Name:	IM000093.JPG
Views:	135
Size:	783.0 KB
ID:	64683  

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #32 (permalink)  
Old 10-28-2012, 06:30 PM
Old Fool's Avatar
Registered User
 
Last photo:
Join Date: Jan 2008
Location: spokane,wa.
Posts: 1,347
Wiki Edits: 0

Thanks: 8
Thanked 40 Times in 34 Posts
back in the day a distributor was put on a distributor machine and had its advance curve set. no guessing, no oh ****s, you knew what you had. That was before they became dizzy's.
Reply With Quote Quick reply to this message
  #33 (permalink)  
Old 10-28-2012, 11:32 PM
Greg T's Avatar
www.krusinklassics.net
 
Last photo:
Join Date: Jul 2007
Location: Escanaba, MI.
Age: 61
Posts: 1,160
Wiki Edits: 0

Thanks: 21
Thanked 41 Times in 32 Posts
Today, I use the MSD E-Curve. Worth every penny.







.
Reply With Quote Quick reply to this message
  #34 (permalink)  
Old 07-09-2013, 11:41 PM
Registered User
 
Last photo:
Join Date: Mar 2009
Location: Burton, MI
Posts: 818
Wiki Edits: 0

Thanks: 39
Thanked 18 Times in 17 Posts
not to be a smart ***** or anything... but did he have the light on the right ignition wire??

I ask this because I went down this road once... when my ignition wires were a rats nest, I missed the #1 wire and got the #2 wire instead.. couldn't figure out why my timing was WAYYY off, and when it got it where i thought it should be, the engine wouldn't run....

spent better part of an hour banging my head against the wall on that one..
Reply With Quote Quick reply to this message
  #35 (permalink)  
Old 08-11-2014, 08:47 PM
Cars, Trucks, Boats
 
Last photo:
Join Date: Dec 2012
Location: Toledo, N.W.Ohio, USA
Posts: 1,796
Wiki Edits: 0

Thanks: 5
Thanked 199 Times in 192 Posts
.
. Sounds to me like the carburetor was too small and high RPMs vacuum was pulling up the vacuum advance a bit...
Reply With Quote Quick reply to this message
  #36 (permalink)  
Old 08-12-2014, 11:31 AM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 7,095
Wiki Edits: 0

Thanks: 4
Thanked 541 Times in 457 Posts
Quote:
Originally Posted by v8hed View Post
383 with GM HEI distributor (modded with aftermarket module, curve kit, coil and shimmed for end play). Before going to the chassis dyno, I'd set my timing up (with a good timing light) for 34* total. Checked it up to about 4,000rpm and I could see the advance curve adding more timing until around 3,000rpm then it remained static. As I said, I only went up to about 3,500-4,000rpm with the timing light... just enough to see that the advance curve had finished adding timing. On the chassis dyno, we were messing around with the timing (just adding/subtracting a couple of degrees to do some fine tuning). I asked the dyno operator to take it up to 6,000rpm and keep the timing light on the balancer. He said total timing went up to something like 50* by 5,500rpm! We checked with another light and same thing. Couldn't hear any pinging (although the car is v.loud). What I don't understand is how could this possibly be happening? I still don't believe everything is at it seems, since taking timing out resulted in less power. If is was really running up around 50* total timing, there's no way the motor would be making power. I've previously tried experimenting locking the mech advance out and didn't see over 36* (with about 14* initial). Since the holes in the base plate physically limit max advance, what's going on with this wacky timing reading? It had occurred to me that perhaps the ProStreet balancer I'm using could be slipping, but it's pretty new and looks perfectly fine to the naked eye.

Anyone got any other ideas or explanations? If not, my next step will be to try a brand new MSD HEI just to eliminate the distributor from the equation. What about spark scatter or some other kind of effect?
If you're running vacuum advance, which you are, you have to go further than just pulling the vacuum can hose and plugging the port the advance plate also needs to be screwed down so it cannot move, otherwise its position is simply dependent upon the return spring in the vacuum can which can be excited by all the vibrations going on when the engine is running at high RPMs.

Another common event is the natural looseness in the timing chain and how it reacts to high RPM excitement. Then there are a number of clearances such as the clearance between the cam's distributor gear and the distributor's gear. The thrust clearance of the cam, typically the flat tappet chevy is unrestrained in forward thrust except by the distributor gear and there is a clearance of the distributor shaft and the housing allowing it some freedom of movement. Even roller cams have a little thrust freedom that works on the distributor gear mesh. All cams have a lot of rotational shake from the slowing when valves are opened against their springs to accelerations on the closing side. Nothing in this system is truly stable. All these clearances can and do gang up to change the timing. This is the reason why competition engines use the crankshaft as the timing reference to trigger the spark rather than a distributor at the end of a group of gears, chains and shafts. There are also other gadgets sold that apply tension to the timing chain for a more consistent holding of set position by not allowing any slack in the chain. Not as good as a crank trigger for ignition timing but very helpful in keeping the camshaft to crankshaft alignment steady. A thrust button on a flat tappet cam is also helpful to limit its fore and aft travel so that doesn't disturb the distributor gear mesh with the cam. Gear drives can be useful in eliminating the gear chain issues but you buy something of the quality and design of the Shaver-Wesmar to really get the needed effects the popular inexpensive drives don't solve this problem and make a lot of noise not doing it.

Bogie

Last edited by oldbogie; 08-12-2014 at 11:37 AM.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last 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 for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Engine dyno to chassis dyno numbers dedub Engine 3 06-19-2011 08:56 PM
chassis dyno hp to engine hp zephyrc General Rodding Tech 1 06-16-2011 03:19 PM
Chassis Dyno vs Flywheel 428ho Hotrodders' Lounge 1 10-23-2006 07:55 AM
Chassis Dyno Question gt2betubbed Hotrodders' Lounge 5 05-16-2004 08:35 PM
How many of y'all have run on chassis dyno bentwings Engine 2 11-16-2002 04:24 AM


All times are GMT -6. The time now is 09:49 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.