Big Block TIMING Review ??
Thread Starter
Drifting
Joined: May 2005
Posts: 1,909
Likes: 6
From: Lake Arrowhead - Georgia > 72 Base Coupe & 74 BB Roadster
Big Block TIMING Review ??
Please Review.....lemme know any problems you read here !
74 - 454 - stock exhaust - carb (rebuilt bt Lars) - XE268H cam with correct springs - lifters and all new valves - pistons - bearings - pump - everything -
After a TOTAL rebuild, I installed the VC1765 / B20 vacuum advance unit. This got rid of the HUGE idle gap between Park and Drive. It now idles nicely at 700 in Park and nicely at 500 in Drive.
Here's the part I want to be sure of.
Original 74 specs call for timing at 10' BTDC. I have 16' set with the vacuum advance plugged. My centrifugal advance MAXES at 36' at 3000 RPM with the VACUUM advance disconnected and plugged. I thought about going with ONE lighter spring to get it all in by 2800 RPM. (?)
With the VACUUM hooked up - I show 24' at 700 idle in Park. At 3000 RPM - I show 50' total timing.
Does all these numbers "sound" right to you guys. It runs like a striped *** ape ... I just don't want to blow up all my hard work!
Thanks for any knowledge ...
74 - 454 - stock exhaust - carb (rebuilt bt Lars) - XE268H cam with correct springs - lifters and all new valves - pistons - bearings - pump - everything -
After a TOTAL rebuild, I installed the VC1765 / B20 vacuum advance unit. This got rid of the HUGE idle gap between Park and Drive. It now idles nicely at 700 in Park and nicely at 500 in Drive.
Here's the part I want to be sure of.
Original 74 specs call for timing at 10' BTDC. I have 16' set with the vacuum advance plugged. My centrifugal advance MAXES at 36' at 3000 RPM with the VACUUM advance disconnected and plugged. I thought about going with ONE lighter spring to get it all in by 2800 RPM. (?)With the VACUUM hooked up - I show 24' at 700 idle in Park. At 3000 RPM - I show 50' total timing.
Does all these numbers "sound" right to you guys. It runs like a striped *** ape ... I just don't want to blow up all my hard work!
Thanks for any knowledge ...
Le Mans Master
Joined: Apr 2004
Posts: 7,106
Likes: 38
From: Newark DE
the numbers are fine and if she runs good leave it alone and just drive it and enjoy!!
all in by 3000rpm is just fine. I personally don't think you are going to gain anything or enough of a change to warrant changing springs to bring timing all in by only 200rpm difference
all in by 3000rpm is just fine. I personally don't think you are going to gain anything or enough of a change to warrant changing springs to bring timing all in by only 200rpm difference
Burning Brakes
Joined: Nov 2001
Posts: 1,191
Likes: 1
Ignore the factory specs and go with the Lars timing method (which it kinda' sorta' sounds like you did), and listen carefully for detonation.
Then post some pics of the long black marks you leave on the road surface!
Then post some pics of the long black marks you leave on the road surface!
Drifting
Joined: May 2006
Posts: 1,425
Likes: 0
From: Seattle Wash.
the numbers are fine and if she runs good leave it alone and just drive it and enjoy!!
all in by 3000rpm is just fine. I personally don't think you are going to gain anything or enough of a change to warrant changing springs to bring timing all in by only 200rpm difference
all in by 3000rpm is just fine. I personally don't think you are going to gain anything or enough of a change to warrant changing springs to bring timing all in by only 200rpm difference
Your car is set up just right. My car has a BB too with timing specs that were set up by Lars and are very close to yours. My car runs like a scalded dog now after Lars made all the changes and adjustmants.
When Lars did our TFB last fall, he mentioned that the reason GM set up the cars was for emission purposes and so the cars would not see their greatest potential. If they were set up the way Lars' and others have done, GM probably would have replaced a lot of motors under warranty back in the day. Drive and ejoy!
Thread Starter
Drifting
Joined: May 2005
Posts: 1,909
Likes: 6
From: Lake Arrowhead - Georgia > 72 Base Coupe & 74 BB Roadster
Your car is set up just right. My car has a BB too with timing specs that were set up by Lars and are very close to yours. My car runs like a scalded dog now after Lars made all the changes and adjustmants.
When Lars did our TFB last fall, he mentioned that the reason GM set up the cars was for emission purposes and so the cars would not see their greatest potential. If they were set up the way Lars' and others have done, GM probably would have replaced a lot of motors under warranty back in the day. Drive and ejoy!
Thanks everyone. Lars has rebuilt both my Qjets "through the mail". Made a huge difference on both cars. I always hated Qjets but now I love em . Lar's papers on timing are great. I used his methods and now have a better understanding of "how chit works" on these old V8s. It's a lot of fun.
Thread Starter
Drifting
Joined: May 2005
Posts: 1,909
Likes: 6
From: Lake Arrowhead - Georgia > 72 Base Coupe & 74 BB Roadster
Guy....Just post your burn-out picture and we will say it's ME. 
We have a Sonic Drive in .... identical cars ... and the back of our heads look identical! I will go to town and make an identical pic as soon as I replace the bumpers. (I ordered front and rear from Toledo just a few days ago)
We have a Sonic Drive in .... identical cars ... and the back of our heads look identical!
I will go to town and make an identical pic as soon as I replace the bumpers. (I ordered front and rear from Toledo just a few days ago)
