Initial Timing Help (Repost from C3 forum)
Thread Starter
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
Initial Timing Help (Repost from C3 forum)
Okay, I am thoroughly confused at this point.
I have a new 400 in there with a Holley 670 carb (for now). It runs but not very well. When I shot the initial timing with the vac adv plugged it read 40 BTDC! When I adjusted it down to 15 BTDC it started chattering and running much hotter. I felt the heat off the engine go WAY UP.
I have an MSD distributor currently set for 25 mechanical all in at 3000rpms. Now, I'm using a flaming river timing light and I read that these MSD units can be hard to get an accurate read on, could that be a problem? The cam is a hyd roller with .50 lift and like 220 duration, plus 1.6 rockers.
The car runs great at idle but has no power and with lots of hesitation when the rpms go up.
I posted this in the c3 forum, like to see if you folks have any additional thoughts on the matter.
http://forums.corvetteforum.com/zerothread?id=760130
Thanks in advance...
I have a new 400 in there with a Holley 670 carb (for now). It runs but not very well. When I shot the initial timing with the vac adv plugged it read 40 BTDC! When I adjusted it down to 15 BTDC it started chattering and running much hotter. I felt the heat off the engine go WAY UP.
I have an MSD distributor currently set for 25 mechanical all in at 3000rpms. Now, I'm using a flaming river timing light and I read that these MSD units can be hard to get an accurate read on, could that be a problem? The cam is a hyd roller with .50 lift and like 220 duration, plus 1.6 rockers.
The car runs great at idle but has no power and with lots of hesitation when the rpms go up.
I posted this in the c3 forum, like to see if you folks have any additional thoughts on the matter.
http://forums.corvetteforum.com/zerothread?id=760130
Thanks in advance...
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: Initial Timing Help (Jack71)
At what rpms are you taking the 40* and 15* readings? At a normal idle, before the centrigual advance starts to kick in, I would shoot for 10*-12* initial. If your distributer is set up as advertised, that would give you 35*-37* total, all in at 3000 rpms. I have a couple more ideas, depending on your answers. Good luck, and...
RACE ON!!!
RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: Initial Timing Help (Jack71)
Not being there, and not knowing the full history, or origin of all the components you're using, the first thing I would do, is verify the timing marks. You could have a mismatch between the damper marking and the timing cover or pointer. From your discription of the idle, and the vacuum you have, I don't think anything is seriously screwed up.
RACE ON!!!
[Modified by CFI-EFI, 4:53 PM 2/26/2004]
RACE ON!!!
[Modified by CFI-EFI, 4:53 PM 2/26/2004]
Thread Starter
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
Re: Initial Timing Help (CFI-EFI)
Well, I just threw in the towel and brought it to EastCoast Supercharging down the street. I know my limits (skill and frustration).
Talk about cars at their shop. whoa... Lots of vettes & other exotics. I hope they'll diagnose the problem & get it dialed in.
Talk about cars at their shop. whoa... Lots of vettes & other exotics. I hope they'll diagnose the problem & get it dialed in.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: Initial Timing Help (Jack71)
Sorry you had to give up on it. We would have licked it if you had more time. The name of the company makes it sound like it's in good hands. Good luck, and...
RACE ON!!!
[Modified by CFI-EFI, 4:36 PM 2/27/2004]
RACE ON!!!
[Modified by CFI-EFI, 4:36 PM 2/27/2004]
Thread Starter
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
Re: Initial Timing Help (mike 1985)
Well things are looking better. I reset the distributor in the block, it must have been off a tooth :jester makes you feel like an idiot after you find these problems.
It was still running rough at that point. So then I dropped it off at ECS and they had quick look over it and found a vacuum leak (damn again!), tuned up the carb. Of course during a road test the heater core blew & the trans started acting up. Doesn't it ever end? The heater core project gets deferred until next winter.
So on the positive side, they said its running strong now and are going to dyno tune it tomorrow.
It was still running rough at that point. So then I dropped it off at ECS and they had quick look over it and found a vacuum leak (damn again!), tuned up the carb. Of course during a road test the heater core blew & the trans started acting up. Doesn't it ever end? The heater core project gets deferred until next winter.
So on the positive side, they said its running strong now and are going to dyno tune it tomorrow.
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