Timing Problem, Help
Thread Starter
Safety Car
Joined: Oct 2004
Posts: 3,725
Likes: 5
From: Minnesota
Timing Problem, Help
I just can't seem to get the timing right. Cleaned up the mechanical advance and put on a black and silver spring so I have all in by about 2000 rpm. I've made a mark at 36 degrees (about 2 inches over on my 6 1/4" damper) for the mechanical advance and tried to set it there but it idles rough and the power isn't there. Right now I've got it set at about 55 degrees mechanical plus initial (fixed timing light). Add about 12 degrees vacuum advance (AR 12 can) and it would mean about 67 degrees total. It seems to run better with no detectable pinging and starts with no kickback 
. I have side pipes so it's possible I don't hear everything :o . Is it possible the mark on my new damper (about 2,000 miles) is off? I would try even more advance but I'd rather not blow up my new engine 
. Any ideas?
I just checked again and the mechanical advance only changes about 10 degrees from the lowest idle to all in. Could this be part of the problem?
. I have side pipes so it's possible I don't hear everything :o . Is it possible the mark on my new damper (about 2,000 miles) is off? I would try even more advance but I'd rather not blow up my new engine . Any ideas? I just checked again and the mechanical advance only changes about 10 degrees from the lowest idle to all in. Could this be part of the problem?
Last edited by jdmick; Jun 16, 2005 at 06:16 PM.
Burning Brakes
Joined: Feb 2005
Posts: 977
Likes: 1
From: wash. dc
timing problem
if yougot 36* in by 2000 rpm thats coming in way too soon... it should be all in by 2500-2800. get yourself an adjustable timing light...its worth it... you also might wanna read lars tuning paper in corvettefaq.com
Thread Starter
Safety Car
Joined: Oct 2004
Posts: 3,725
Likes: 5
From: Minnesota
I'd like to verify that but is there any other way short of removing my sidepipe headers to shove the indicator in #1? The headers are Stage 8'd on and rusted onto the sidepipes so taking them off isn't sounding too good to me right now .
.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by jdmick
. Right now I've got it set at about 55 degrees mechanical plus initial (fixed timing light). Add about 12 degrees vacuum advance (AR 12 can) and it would mean about 67 degrees total. It seems to run better with no detectable pinging and starts with no kickback . I have side pipes so it's possible I don't hear everything :o . Is it possible the mark on my new damper (about 2,000 miles) is off? I would try even more advance but I'd rather not blow up my new engine . Any ideas?
I just checked again and the mechanical advance only changes about 10 degrees from the lowest idle to all in. Could this be part of the problem?
. I have side pipes so it's possible I don't hear everything :o . Is it possible the mark on my new damper (about 2,000 miles) is off? I would try even more advance but I'd rather not blow up my new engine . Any ideas? I just checked again and the mechanical advance only changes about 10 degrees from the lowest idle to all in. Could this be part of the problem?
i think you are double counting for starters....i did this also in the excitement..... your total 36* at 2000 rpm includes your initial timing + your mechanical advance.... you said the timing only changes 10* from lowest idle to all in.....so this is what i think you have.....36* at 2000 RPM ...less 10 degrees of mechanical advance = 26* of initial timing. so you have 26* initial +10 advance + 12 degrees vacuum
i think you have too much timing coming in too soon.... i think you need to try and set your timing so it is coming in a little bit later say getting the 36* at 2500-2800 rpm this may change your initial timing at idle down a bit , 26* initial seems kind of high to me, shoot for the 18* range for starters. Lars is really good at making this understandable have you read any of his posts on this stuff.
Last edited by bobs77vet; Jun 16, 2005 at 10:01 PM.
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
Originally Posted by jdmick
I'd like to verify that but is there any other way short of removing my sidepipe headers to shove the indicator in #1? The headers are Stage 8'd on and rusted onto the sidepipes so taking them off isn't sounding too good to me right now .
.If the timing mark is off on the balancer you will need to get it fixed or set the timing by ear.
BigBlockk
Later.....
Thread Starter
Safety Car
Joined: Oct 2004
Posts: 3,725
Likes: 5
From: Minnesota
Originally Posted by bobs77vet
i think you are double counting for starters
MsVetteman, yup, Vacuum adv. is disconnected.
BigBlockk, I'll find a helper to see how it comes out that way. 20 deg. off should be fairly obvious if that's the problem. If all else fails tell me more about your procedure for timing by ear. From what I know you just advance until you notice pinging under load or kickback when you try to start it and then back it off a little. Anything else?
I think I'll try some heavier springs since it advances too early but I thought the black springs, sometimes with a silver were almost always right. Is there ever much difference in the weights? This distributor is of unknown origin. My parts guy gave it to me and he wasn't sure what it came off of. Thanks. John
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Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by jdmick
. Right now I've got it set at about 55 degrees mechanical plus initial (fixed timing light). Add about 12 degrees vacuum advance (AR 12 can) and it would mean about 67 degrees total. ...I just checked again and the mechanical advance only changes about 10 degrees from the lowest idle to all in. Could this be part of the problem?
Originally Posted by jdmick
Not sure what you mean Bob but my understanding from Lars and others is you want the 36 deg. to be the initial advance plus the mechanical advance total. Add to that your Vacuum advance of say 14 deg. and the total advance would be 50 deg. Instead of 36 I would guess it's closer to 55 deg.
Melting Slicks
Joined: Dec 2004
Posts: 2,101
Likes: 3
From: Cruising somewhere in St. Louis, Missouri
jd -
This is Lars writing from Jim's computer in San Francisco...
Sounds like your balancer has slipped or that your timing marks are otherwise off. You are doing everything correctly: Getting 36 degrees all in at 2000 rpm is a good spec, and seeing just 10 degrees of centrifugal advance is about right for the light springs, since some of your advance will be in right at idle with the light springs. Nothing wrong with that. But if you're running best at 55 mechanical, indications are that your balancer is off, since a car will not run well (and will detonate) at 55 degrees mechanical advance. The fact that it's running best at this odd spec is a very good indication that you have other issues that need to be tracked down.
You don't have a problem with what you're doing and your timing technique. Your spec of 36 at 2000 is just fine and will run very well. But I do thik you have an issue with determining actual TDC of your engine - you need to positively establish this.
Lars
This is Lars writing from Jim's computer in San Francisco...
Sounds like your balancer has slipped or that your timing marks are otherwise off. You are doing everything correctly: Getting 36 degrees all in at 2000 rpm is a good spec, and seeing just 10 degrees of centrifugal advance is about right for the light springs, since some of your advance will be in right at idle with the light springs. Nothing wrong with that. But if you're running best at 55 mechanical, indications are that your balancer is off, since a car will not run well (and will detonate) at 55 degrees mechanical advance. The fact that it's running best at this odd spec is a very good indication that you have other issues that need to be tracked down.
You don't have a problem with what you're doing and your timing technique. Your spec of 36 at 2000 is just fine and will run very well. But I do thik you have an issue with determining actual TDC of your engine - you need to positively establish this.
Lars
Thread Starter
Safety Car
Joined: Oct 2004
Posts: 3,725
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From: Minnesota
Sounds like my damper must be bad. It was 60 or 70 bucks from Jegs so it's not the best one out there. With all the new parts I've put on my car this is the first defective one so overall I've done OK. I'll work on establishing the true TDC and try again. Thanks guys.
i bet