timing curve problem
Thread Starter
Instructor
Joined: Apr 2012
Posts: 135
Likes: 1
From: Kirbyville Texas
timing curve problem
I just got my rebuild installed and I'm trying to set my timing. I have a 350 bored.040, KB pistons 906 vortec heads, Lanati voodoo cam 60104 (276) about 10.2 cr.
When I set @ 32° it's all in around 2300 and bring back to idle the initial is @ 22° which made me nervous. I ran it up the road and @ wot was knocking. (Pinging?) So I dropped the initial to around 15° @ 900 rpm and that put it all in @ around 25°.
I've read that those heads like it around 28°-30°, but 25 just seemed low. ..... yes I'm new at this hahaha!
Could it be to light of springs?
When I set @ 32° it's all in around 2300 and bring back to idle the initial is @ 22° which made me nervous. I ran it up the road and @ wot was knocking. (Pinging?) So I dropped the initial to around 15° @ 900 rpm and that put it all in @ around 25°.
I've read that those heads like it around 28°-30°, but 25 just seemed low. ..... yes I'm new at this hahaha!
Could it be to light of springs?
Advanced
Joined: Jul 2012
Posts: 71
Likes: 3
From: grandfield ok
I just got my rebuild installed and I'm trying to set my timing. I have a 350 bored.040, KB pistons 906 vortec heads, Lanati voodoo cam 60104 (276) about 10.2 cr.
When I set @ 32° it's all in around 2300 and bring back to idle the initial is @ 22° which made me nervous. I ran it up the road and @ wot was knocking. (Pinging?) So I dropped the initial to around 15° @ 900 rpm and that put it all in @ around 25°.
I've read that those heads like it around 28°-30°, but 25 just seemed low. ..... yes I'm new at this hahaha!
Could it be to light of springs?
When I set @ 32° it's all in around 2300 and bring back to idle the initial is @ 22° which made me nervous. I ran it up the road and @ wot was knocking. (Pinging?) So I dropped the initial to around 15° @ 900 rpm and that put it all in @ around 25°.
I've read that those heads like it around 28°-30°, but 25 just seemed low. ..... yes I'm new at this hahaha!
Could it be to light of springs?
Thread Starter
Instructor
Joined: Apr 2012
Posts: 135
Likes: 1
From: Kirbyville Texas
It just seemed low @ 25°all in
Advanced
Joined: Jul 2012
Posts: 71
Likes: 3
From: grandfield ok
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
I just got my rebuild installed and I'm trying to set my timing. I have a 350 bored.040, KB pistons 906 vortec heads, Lanati voodoo cam 60104 (276) about 10.2 cr.
When I set @ 32° it's all in around 2300 and bring back to idle the initial is @ 22° which made me nervous. I ran it up the road and @ wot was knocking. (Pinging?) So I dropped the initial to around 15° @ 900 rpm and that put it all in @ around 25°.
I've read that those heads like it around 28°-30°, but 25 just seemed low. ..... yes I'm new at this hahaha!
Could it be to light of springs?
When I set @ 32° it's all in around 2300 and bring back to idle the initial is @ 22° which made me nervous. I ran it up the road and @ wot was knocking. (Pinging?) So I dropped the initial to around 15° @ 900 rpm and that put it all in @ around 25°.
I've read that those heads like it around 28°-30°, but 25 just seemed low. ..... yes I'm new at this hahaha!
Could it be to light of springs?
What kind of distributor are you using? A points type or an HEI? The HEI's have 20+ degrees of mechanical advance so with an initial of 12 degrees you'd end up with 32 degrees. And then with the addition of the vacuum advance you'd want around 50-52 degrees total for light throttle cruising.
Drifting
Joined: Mar 2011
Posts: 1,347
Likes: 121
From: Kernersville NC
Do you have a distributor with vacuum advance? Do you have it disconnected? Have you slowed your idle down to see if the mechanical advance is doing anything at 900rpm idle?
My mechanical advance starts about 750-800 rpm so I have to set the base timing about 650-700 rpm. You really need to get the idle down where the mechanical is not doing any thing to see what you really are doing.
Now see what your total timing is and what rpm it is all in. If you are in the mid 30s at 2500 rpm or so you will be ok. You can fine tune timing later to figure out what the engine likes.
Then advance carb to the desired idle, 850-900, and adjust carb per manufacturers instructions. Use a vacuum gauge.
When I advance to 800-900 rpm for a "happy idle" my timing comes up a couple degrees.
If you have a vac advance you can then try it on timed or manifold vac and see what the engine likes. Mine likes manifold vac.
My mechanical advance starts about 750-800 rpm so I have to set the base timing about 650-700 rpm. You really need to get the idle down where the mechanical is not doing any thing to see what you really are doing.
Now see what your total timing is and what rpm it is all in. If you are in the mid 30s at 2500 rpm or so you will be ok. You can fine tune timing later to figure out what the engine likes.
Then advance carb to the desired idle, 850-900, and adjust carb per manufacturers instructions. Use a vacuum gauge.
When I advance to 800-900 rpm for a "happy idle" my timing comes up a couple degrees.
If you have a vac advance you can then try it on timed or manifold vac and see what the engine likes. Mine likes manifold vac.
Last edited by flyeri; Dec 27, 2015 at 06:33 PM.
Thread Starter
Instructor
Joined: Apr 2012
Posts: 135
Likes: 1
From: Kirbyville Texas
What kind of distributor are you using? A points type or an HEI? The HEI's have 20+ degrees of mechanical advance so with an initial of 12 degrees you'd end up with 32 degrees. And then with the addition of the vacuum advance you'd want around 50-52 degrees total for light throttle cruising.
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Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
If you have an HEI it'll give you 20 degrees of advance so if its not giving you that much the springs would be way too heavy which would prevent the advance weights from flailing outward.
To check the amount of mechanical advance you're getting set your initial timing to 10 degrees then rev it to about 3000 rpm and see how far your timing is advancing then subtract the initial 10 degrees to get the total mechanical advance. The aftermarket HEI's come with heavier (thicker) flyweights to get a quicker advance.
Thread Starter
Instructor
Joined: Apr 2012
Posts: 135
Likes: 1
From: Kirbyville Texas
Do you have a distributor with vacuum advance? Do you have it disconnected? Have you slowed your idle down to see if the mechanical advance is doing anything at 900rpm idle?
My mechanical advance starts about 750-800 rpm so I have to set the base timing about 650-700 rpm. You really need to get the idle down where the mechanical is not doing any thing to see what you really are doing.
Now see what your total timing is and what rpm it is all in. If you are in the mid 30s at 2500 rpm or so you will be ok. You can fine tune timing later to figure out what the engine likes.
Then advance carb to the desired idle, 850-900, and adjust carb per manufacturers instructions. Use a vacuum gauge.
When I advance to 800-900 rpm for a "happy idle" my timing comes up a couple degrees.
If you have a vac advance you can then try it on timed or manifold vac and see what the engine likes. Mine likes manifold vac.
My mechanical advance starts about 750-800 rpm so I have to set the base timing about 650-700 rpm. You really need to get the idle down where the mechanical is not doing any thing to see what you really are doing.
Now see what your total timing is and what rpm it is all in. If you are in the mid 30s at 2500 rpm or so you will be ok. You can fine tune timing later to figure out what the engine likes.
Then advance carb to the desired idle, 850-900, and adjust carb per manufacturers instructions. Use a vacuum gauge.
When I advance to 800-900 rpm for a "happy idle" my timing comes up a couple degrees.
If you have a vac advance you can then try it on timed or manifold vac and see what the engine likes. Mine likes manifold vac.
I'll check it tomorrow @ a lower idle to see when the mechanical is beginning to come in. My vaccum is at the carb
Thread Starter
Instructor
Joined: Apr 2012
Posts: 135
Likes: 1
From: Kirbyville Texas
If you have an HEI it'll give you 20 degrees of advance so if its not giving you that much the springs would be way too heavy which would prevent the advance weights from flailing outward.
To check the amount of mechanical advance you're getting set your initial timing to 10 degrees then rev it to about 3000 rpm and see how far your timing is advancing then subtract the initial 10 degrees to get the total mechanical advance. The aftermarket HEI's come with heavier (thicker) flyweights to get a quicker advance.
To check the amount of mechanical advance you're getting set your initial timing to 10 degrees then rev it to about 3000 rpm and see how far your timing is advancing then subtract the initial 10 degrees to get the total mechanical advance. The aftermarket HEI's come with heavier (thicker) flyweights to get a quicker advance.
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
Your correct-the springs are too light. Change one (they don't both have to be the same tension) to a stronger tension. Check the RPM for max advance. It should be about 3000 RPM. Keep changing until you have the advance required.
Thread Starter
Instructor
Joined: Apr 2012
Posts: 135
Likes: 1
From: Kirbyville Texas
Le Mans Master
Joined: May 2002
Posts: 5,084
Likes: 786
From: Lebanon Township New Jersey
When you get the advance curve corrected, you want your total timing, that is initial plus mechanical all in to be 34 deg. That is with vacuum disconnected. I have Vortec heads on mine and that is my experience.
Race Director
Joined: May 2006
Posts: 18,626
Likes: 2,553
click on the instructions tab for the distributor in the link below. Unmodified it has 22 degrees of mechanical advance so combined with an initial setting of 14 would give you a total of the desired 36 degrees or whatever your desired total is. The total of 22 degrees comes in at 4000 rpm so you need to switch to the softer springs.
http://www.msdignition.com/Products/...stributor.aspx
http://www.msdignition.com/Products/...stributor.aspx
Last edited by MelWff; Dec 28, 2015 at 05:57 PM.
Former Vendor
Joined: Jun 2012
Posts: 145
Likes: 13
Hi Kcat Fan
Timing questions are something we hear every day at BluePrint Engines.
With your combination and the Lunati camshaft that has 231/245 duration @.050, you are going to want more initial timing at idle and reduce the mechanical timing in your distributor. You are also going to want to reduce the vacuum advance timing, or just disconnect and not use it all.
First, your MSD 8362 Street Fire HEI comes with 24* of mechanical advance, with springs that don't fully advance until 4000 rpm. They are great because they also come with a recurve kit. First, change the bushing to the black one, this will limit the mechanical timing to 18*, then follow the instructions so all the timing is in by 3000 rpms. This will allow you to run 14-16* of initial timing.
With your big, lumpy camshaft with low vacuum at idle, the more initial you have, the better your idle quality and off idle drivability will be.
On an engine combo like yours, the vacuum advance really isn't going to do much for you. But, if you think you have to run it, then reduce the amount of timing it adds. I believe the MSD has an adjustable vacuum advance on it, if not, get one. Using it with its stock settings and your 10.2:1 compression you will get a lot of part throttle knocking and pinging. That's bad. If you are going to use the adjustable vacuum advance, then setting it should be last and it you do it on the road. Start by setting it with the least amount of timing added, then go up until it starts pinging at part and full throttle; then back it off until it stops.
Remember to do all your timing settings with the vacuum advance disconnected and the port on the carb capped off. I just pull the vacuum line off the distributor side and cap the hose with a golf tee.
With your cam, your engine will need to idle at least 900-1000 rpm in park or neutral. Once you have all your initial, mechanical and finally your vacuum advance reconnected, readjust the idle speed at that point.
Have fun with your Vette's new engine.
Scott Liggett
BluePrint Engines
1(800)483-4263
info@blueprintengines.com
Timing questions are something we hear every day at BluePrint Engines.
With your combination and the Lunati camshaft that has 231/245 duration @.050, you are going to want more initial timing at idle and reduce the mechanical timing in your distributor. You are also going to want to reduce the vacuum advance timing, or just disconnect and not use it all.
First, your MSD 8362 Street Fire HEI comes with 24* of mechanical advance, with springs that don't fully advance until 4000 rpm. They are great because they also come with a recurve kit. First, change the bushing to the black one, this will limit the mechanical timing to 18*, then follow the instructions so all the timing is in by 3000 rpms. This will allow you to run 14-16* of initial timing.
With your big, lumpy camshaft with low vacuum at idle, the more initial you have, the better your idle quality and off idle drivability will be.
On an engine combo like yours, the vacuum advance really isn't going to do much for you. But, if you think you have to run it, then reduce the amount of timing it adds. I believe the MSD has an adjustable vacuum advance on it, if not, get one. Using it with its stock settings and your 10.2:1 compression you will get a lot of part throttle knocking and pinging. That's bad. If you are going to use the adjustable vacuum advance, then setting it should be last and it you do it on the road. Start by setting it with the least amount of timing added, then go up until it starts pinging at part and full throttle; then back it off until it stops.
Remember to do all your timing settings with the vacuum advance disconnected and the port on the carb capped off. I just pull the vacuum line off the distributor side and cap the hose with a golf tee.
With your cam, your engine will need to idle at least 900-1000 rpm in park or neutral. Once you have all your initial, mechanical and finally your vacuum advance reconnected, readjust the idle speed at that point.
Have fun with your Vette's new engine.
Scott Liggett
BluePrint Engines
1(800)483-4263
info@blueprintengines.com
Last edited by BluePrint Engines; Dec 28, 2015 at 05:50 PM.
Thread Starter
Instructor
Joined: Apr 2012
Posts: 135
Likes: 1
From: Kirbyville Texas
Hi Kcat Fan
Timing questions are something we hear every day at BluePrint Engines.
With your combination and the Lunati camshaft that has 231/245 duration @.050, you are going to want more initial timing at idle and reduce the mechanical timing in your distributor. You are also going to want to reduce the vacuum advance timing, or just disconnect and not use it all.
First, your MSD 8362 Street Fire HEI comes with 24* of mechanical advance, with springs that don't fully advance until 4000 rpm. They are great because they also come with a recurve kit. First, change the bushing to the black one, this will limit the mechanical timing to 18*, then follow the instructions so all the timing is in by 3000 rpms. This will allow you to run 14-16* of initial timing.
With your big, lumpy camshaft with low vacuum at idle, the more initial you have, the better your idle quality and off idle drivability will be.
On an engine combo like yours, the vacuum advance really isn't going to do much for you. But, if you think you have to run it, then reduce the amount of timing it adds. I believe the MSD has an adjustable vacuum advance on it, if not, get one. Using it with its stock settings and your 10.2:1 compression you will get a lot of part throttle knocking and pinging. That's bad. If you are going to use the adjustable vacuum advance, then setting it should be last and it you do it on the road. Start by setting it with the least amount of timing added, then go up until it starts pinging at part and full throttle; then back it off until it stops.
Remember to do all your timing settings with the vacuum advance disconnected and the port on the carb capped off. I just pull the vacuum line off the distributor side and cap the hose with a golf tee.
With your cam, your engine will need to idle at least 900-1000 rpm in park or neutral. Once you have all your initial, mechanical and finally your vacuum advance reconnected, readjust the idle speed at that point.
Have fun with your Vette's new engine.
Scott Liggett
BluePrint Engines
1(800)483-4263
info@blueprintengines.com
Timing questions are something we hear every day at BluePrint Engines.
With your combination and the Lunati camshaft that has 231/245 duration @.050, you are going to want more initial timing at idle and reduce the mechanical timing in your distributor. You are also going to want to reduce the vacuum advance timing, or just disconnect and not use it all.
First, your MSD 8362 Street Fire HEI comes with 24* of mechanical advance, with springs that don't fully advance until 4000 rpm. They are great because they also come with a recurve kit. First, change the bushing to the black one, this will limit the mechanical timing to 18*, then follow the instructions so all the timing is in by 3000 rpms. This will allow you to run 14-16* of initial timing.
With your big, lumpy camshaft with low vacuum at idle, the more initial you have, the better your idle quality and off idle drivability will be.
On an engine combo like yours, the vacuum advance really isn't going to do much for you. But, if you think you have to run it, then reduce the amount of timing it adds. I believe the MSD has an adjustable vacuum advance on it, if not, get one. Using it with its stock settings and your 10.2:1 compression you will get a lot of part throttle knocking and pinging. That's bad. If you are going to use the adjustable vacuum advance, then setting it should be last and it you do it on the road. Start by setting it with the least amount of timing added, then go up until it starts pinging at part and full throttle; then back it off until it stops.
Remember to do all your timing settings with the vacuum advance disconnected and the port on the carb capped off. I just pull the vacuum line off the distributor side and cap the hose with a golf tee.
With your cam, your engine will need to idle at least 900-1000 rpm in park or neutral. Once you have all your initial, mechanical and finally your vacuum advance reconnected, readjust the idle speed at that point.
Have fun with your Vette's new engine.
Scott Liggett
BluePrint Engines
1(800)483-4263
info@blueprintengines.com
From my research it seems like these heads like 29°or so. It's just been tricky for me with the cam and cr and all coming into play. I'll try to do away with the vacuum advance and up my initial timing. I ran it today and it seems to be fluttery @ normal acceleration. Is that the knocking/pinging you were talking about?
Thanks for your help