I THINK I Found The Problem
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
I THINK I Found The Problem
I think I may have discovered why my motor was no longer firing. When I initially took the timing cover off with the motor at TDC, compression stroke the timing marks were close at 12 and 12 but not perfectly aligned. When I rotated the motor and aligned them perfectly at 6 and 12 the damper read 8 degrees BTDC. When I rotated them to the exact 12 and 12 positions the damper read 8 degrees BTDC.
When I reinstalled the cam/timing set I aligned the marks perfectly at 6 and 12 and the damper now reads 0 degrees, TDC exactly. Same when I rotate it to 12 and 12, 0 degrees TDC. It appears that somewhere along the line the timing jumped. At least thats what I'm hoping. I plan on putting everything back together this weekend and right now I'm confident it's going to start. I also put a second ground wire, 4 ga. copper stranded from the block to the frame.
When I reinstalled the cam/timing set I aligned the marks perfectly at 6 and 12 and the damper now reads 0 degrees, TDC exactly. Same when I rotate it to 12 and 12, 0 degrees TDC. It appears that somewhere along the line the timing jumped. At least thats what I'm hoping. I plan on putting everything back together this weekend and right now I'm confident it's going to start. I also put a second ground wire, 4 ga. copper stranded from the block to the frame.
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 nastee383
. It appears that somewhere along the line the timing jumped. At least thats what I'm hoping. .
Pro
Joined: Dec 2002
Posts: 560
Likes: 1
From: Mooresville NC
Wasn't the cam ground with 4deg advanced built in and then it was intalled with an additional 4deg advance?
BTW wasn't the car running fine before that screech you heard? I don't think you found your problem, but I hope for your sakes I'm wrong. You've put alot of time into this.
Good Luck.
BTW wasn't the car running fine before that screech you heard? I don't think you found your problem, but I hope for your sakes I'm wrong. You've put alot of time into this.
Good Luck.
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
Originally Posted by bobs77vet
are you using the same timing chain?
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 nastee383
Initially I am. Its a Cloyes double roller thats virtually brand new, no slack when installed.
Last edited by bobs77vet; Oct 20, 2005 at 01:38 PM.
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
Originally Posted by MILO
Wasn't the cam ground with 4deg advanced built in and then it was intalled with an additional 4deg advance?
BTW wasn't the car running fine before that screech you heard? I don't think you found your problem, but I hope for your sakes I'm wrong. You've put alot of time into this.
Good Luck.
BTW wasn't the car running fine before that screech you heard? I don't think you found your problem, but I hope for your sakes I'm wrong. You've put alot of time into this.
Good Luck.
I'm thinking the starter kickback caused the timing to jump somehow. I know it fragged the starter. As for the good luck, I'm gonna need it. I'm optimistic because I haven't found anything else out of the ordinary.
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
Originally Posted by bobs77vet
??? well if it shows no signs of being stretched how it did it Jump? and if you really thinked it did jump why are you using the same chain....i know you want a fix for this but you know something just doesn't sit right with me on this diagnois.
Racer
Joined: Nov 2000
Posts: 290
Likes: 0
From: Omaha, NE
On a new timing set there is no way it could jump without some visible damage somewhere so I would guess the timing "jump" occurred at the installation step. This is easy enough to do-ask me how I know! Now that you are certain everything is in proper alignment/timing that initial noise is the remaining question. Did you inspect the top oil gallery boss behind the cam gear?? Just maybe that initial noise was the chain grinding some of it off. On my Cloyes double roller install that boss had to be ground off a bit~.040 inch- to clear the chain. If there was interference you likely have some metal filings in your pan. Good luck.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
You will only see the 4 degrees ground into the cam with a degree wheel not on the balancer. If you have the crank sprocket exactly at the 12 oclock position the balancer has to point to 0 degrees unless if has slipped
Last edited by MotorHead; Oct 20, 2005 at 01:59 PM.
Race Director
Joined: Jan 2000
Posts: 13,018
Likes: 2,262
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Well, before you put it all back together..just drop in dist and fire it up for a second or two without front cover. Won't hurt anything other than sling a little oil if you run it too long. It's a lot easier than tearing it all apart again.
Still sounds a little wierd to me...not sure we have it yet either....
Didn't you do a compression test? If it jumped the compression will be affected.
JIM
Still sounds a little wierd to me...not sure we have it yet either....
Didn't you do a compression test? If it jumped the compression will be affected.
JIM
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
Originally Posted by Marv
On a new timing set there is no way it could jump without some visible damage somewhere so I would guess the timing "jump" occurred at the installation step. This is easy enough to do-ask me how I know! Now that you are certain everything is in proper alignment/timing that initial noise is the remaining question. Did you inspect the top oil gallery boss behind the cam gear?? Just maybe that initial noise was the chain grinding some of it off. On my Cloyes double roller install that boss had to be ground off a bit~.040 inch- to clear the chain. If there was interference you likely have some metal filings in your pan. Good luck.
Team Owner
Joined: Sep 2003
Posts: 88,393
Likes: 2
From: eville in
Originally Posted by Marv
On a new timing set there is no way it could jump without some visible damage somewhere so I would guess the timing "jump" occurred at the installation step. This is easy enough to do-ask me how I know! Now that you are certain everything is in proper alignment/timing that initial noise is the remaining question. Did you inspect the top oil gallery boss behind the cam gear?? Just maybe that initial noise was the chain grinding some of it off. On my Cloyes double roller install that boss had to be ground off a bit~.040 inch- to clear the chain. If there was interference you likely have some metal filings in your pan. Good luck.
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
Originally Posted by MotorHead
You will only see the 4 degrees ground into the cam with a degree wheel not on the balancer. If you have the crank sprocket exactly at the 12 oclock position the balancer has to point to 0 degrees unless if has slipped
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 2,145
Likes: 1
From: Ft. Walton Beach, Fl USA
Originally Posted by 427Hotrod
Well, before you put it all back together..just drop in dist and fire it up for a second or two without front cover. Won't hurt anything other than sling a little oil if you run it too long. It's a lot easier than tearing it all apart again.
Still sounds a little wierd to me...not sure we have it yet either....
Didn't you do a compression test? If it jumped the compression will be affected.
JIM
Still sounds a little wierd to me...not sure we have it yet either....
Didn't you do a compression test? If it jumped the compression will be affected.
JIM
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
Originally Posted by nastee383
When I initially took off the cover and the damper showed 8 degrees BTDC with the marks perfectly aligned I asked the question would 4 degrees fround in and 4 degrees advanced on the crank sprocket show 8 degrees on the damper. i never really got an answer to that question. but since I've been looking at it I don't believe it would. Even if you put the crank sprocket on in the advanced or retarded position the position of the keyway doesn't move, so the damper should not show a different reading. And the 4 degrees ground in isn't going to show on the damper. If I'm wrong, someone set me straight.
Its going to be interesting to see if it will fire up this time.
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
Originally Posted by TJ76
If the chain jumped a tooth, wouldn't the difference be more like 25 degrees? TJ
Le Mans Master
Joined: Oct 2004
Posts: 5,269
Likes: 54
From: Orlando Florida
St. Jude Donor '05
Originally Posted by 427Hotrod
Well, before you put it all back together..just drop in dist and fire it up for a second or two without front cover. Won't hurt anything other than sling a little oil if you run it too long. It's a lot easier than tearing it all apart again.
good idea
