timing set for a 64-65 327 chevy small block?
08-01-2008, 04:59 PM
#1
Instructor
Thread Starter
timing set for a 64-65 327 chevy small block?
What's the timing set for a 327 small block......1964 or 65? I read one post on another site that said 10 degrees before for a 350 hp.
08-01-2008, 09:42 PM
#4
Safety Car
Member Since: Feb 1999
Location: Fountain Hills AZ
Posts: 3,626
Likes: 0
Received 10 Likes
on
10 Posts
Be sure to check the total. It's very possible that a 40+ year old distributor has been rebuilt/modified/replaced and the original specs are different. The only reason the factory provided an initial spec was they knew the curve of the particular distributor being used and what total would result. Once modified, those specs may no longer apply.
08-03-2008, 09:18 AM
#5
Drifting
yep..
unless you are blueprinting your distributor and are 100% sure of what your advance curve is.. then initial really wont tell you a thing.
in my cars... i have very fast advance curves... like 20 degrees max that come in at about 2500 rpm...
which means as soon as I roll off the line... (with 3.70 or 4.10 gears and a wide ratio trans) my timing is fully advanced.. and the cars love it provided you have good gas in it
that also means that my initial is somewhere around 18 degrees to get the 37-38 degrees full timing that I want.
IN FACT, i had my 69Z out friday and twice (when I got on it) i noticed that it seemed a little sluggish (compared to what I'm used to)
so when I got home, the first thing I did was check the timing...
initial was at 12... I immediatly knew what the probolem was... with only 20 degrees centrifugal advance, my WOT was only hitting about 32-33 degrees...
i advanced the distributor 6 degrees which gave me the 18 initial, and 38 WOT and voila, like I added 50 cubes. had to drop the curb idle back down- but that too solved a problem... with the timing at 12, my idle speed always fluctuated a couple hundred degrees and I was never sure what the problem was.
I must have set the timing last in a hurry and as the dizzy slipped over the past year and a 1/2 (which was the last time I checked it) I must have bumped the curb idle up to compensate.
Now that my timing is where I want it, backing off the curb idle to achieve the 900 idle rpm really smoothed out the inconsistancy problem I was having.
with my car... 17-18 initial is about as much timing as it will take to start smooth... if you go any more than that... then you'll feel it fighting you while you try to start it...
the other downside to having more initial... is that it does take longer to start... (but not much)
some cars fire instantly.. which is cool... and mine did that for a period of time... but when I recurved the distributor... it crankes over a couple times before firing, but is now much more responsive and is very easy to drive... considering the cantankerous nature of a DZ302.
Thanks
Aaron
unless you are blueprinting your distributor and are 100% sure of what your advance curve is.. then initial really wont tell you a thing.
in my cars... i have very fast advance curves... like 20 degrees max that come in at about 2500 rpm...
which means as soon as I roll off the line... (with 3.70 or 4.10 gears and a wide ratio trans) my timing is fully advanced.. and the cars love it provided you have good gas in it
that also means that my initial is somewhere around 18 degrees to get the 37-38 degrees full timing that I want.
IN FACT, i had my 69Z out friday and twice (when I got on it) i noticed that it seemed a little sluggish (compared to what I'm used to)
so when I got home, the first thing I did was check the timing...
initial was at 12... I immediatly knew what the probolem was... with only 20 degrees centrifugal advance, my WOT was only hitting about 32-33 degrees...
i advanced the distributor 6 degrees which gave me the 18 initial, and 38 WOT and voila, like I added 50 cubes.
had to drop the curb idle back down- but that too solved a problem... with the timing at 12, my idle speed always fluctuated a couple hundred degrees and I was never sure what the problem was.I must have set the timing last in a hurry and as the dizzy slipped over the past year and a 1/2 (which was the last time I checked it) I must have bumped the curb idle up to compensate.
Now that my timing is where I want it, backing off the curb idle to achieve the 900 idle rpm really smoothed out the inconsistancy problem I was having.
with my car... 17-18 initial is about as much timing as it will take to start smooth... if you go any more than that... then you'll feel it fighting you while you try to start it...
the other downside to having more initial... is that it does take longer to start... (but not much)
some cars fire instantly.. which is cool... and mine did that for a period of time... but when I recurved the distributor... it crankes over a couple times before firing, but is now much more responsive and is very easy to drive... considering the cantankerous nature of a DZ302.
Thanks
Aaron
Last edited by aaronz28; 08-03-2008 at 09:22 AM.
08-03-2008, 11:30 AM
#6
Le Mans Master
I don't mean to hijack the thread...but I have one question:
I just want to make sure I understand Lars paper on timing. He said to remove only one of the springs from the cent. weights. Plug and disconnect vac. line.Then set full advance timing with a dial back light. I have a NOM 350 that I don't have a clue what the initial should be. So, I have to default to setting full advance and letting initial fall where it may. I have it setup by Lars paper with 36 deg. all in around 3k-4k rpm. So by removing the spring. It will never go past 36.deg cent. right ? I am using the original springs, Pertronix Igniter II, and their matched coil. I have the B28 vac. can.
I just want to make sure I understand Lars paper on timing. He said to remove only one of the springs from the cent. weights. Plug and disconnect vac. line.Then set full advance timing with a dial back light. I have a NOM 350 that I don't have a clue what the initial should be. So, I have to default to setting full advance and letting initial fall where it may. I have it setup by Lars paper with 36 deg. all in around 3k-4k rpm. So by removing the spring. It will never go past 36.deg cent. right ? I am using the original springs, Pertronix Igniter II, and their matched coil. I have the B28 vac. can.
08-03-2008, 12:09 PM
#7
Safety Car
I don't mean to hijack the thread...but I have one question:
I just want to make sure I understand Lars paper on timing. He said to remove only one of the springs from the cent. weights. Plug and disconnect vac. line.Then set full advance timing with a dial back light. I have a NOM 350 that I don't have a clue what the initial should be. So, I have to default to setting full advance and letting initial fall where it may. I have it setup by Lars paper with 36 deg. all in around 3k-4k rpm. So by removing the spring. It will never go past 36.deg cent. right? I am using the original springs, Pertronix Igniter II, and their matched coil. I have the B28 vac. can.
I just want to make sure I understand Lars paper on timing. He said to remove only one of the springs from the cent. weights. Plug and disconnect vac. line.Then set full advance timing with a dial back light. I have a NOM 350 that I don't have a clue what the initial should be. So, I have to default to setting full advance and letting initial fall where it may. I have it setup by Lars paper with 36 deg. all in around 3k-4k rpm. So by removing the spring. It will never go past 36.deg cent. right? I am using the original springs, Pertronix Igniter II, and their matched coil. I have the B28 vac. can.
I'm not certain what you mean by this, unless you have no understanding of what the springs are designed to accomplish.. The purpose in removing one spring temporarily, is to get it "all-in" as fast as possible, just to determine where "all-in" is.
I disagree in one respect, and that is, that total should be 38, not 36 degrees.
If your engine tolerates it, then it should be "all in" @ 2200-2500 RPM.
You may have to bend the heels on the weights, or shorten the centrifugal advance slot to limit total to 38 degrees. There should be a limit bushing installed on the pin.
Lighten your advance springs to have it "all-in" by 2200-2500. Yours is too high, at 3000-4000, unless you have a mild cam, along with relatively low static compression.
Your advance map should be such, that your initial is about 14 degrees.
Joe
Last edited by 65tripleblack; 08-03-2008 at 12:12 PM.
08-06-2008, 02:42 PM
#8
Tech Contributor
Member Since: Aug 1999
Location: At my Bar drinking and wrenching in Lafayette Colorado
Posts: 13,659
Received 4,927 Likes
on
1,933 Posts
As Joe states, the purpose in removing one spring on a stock distributor is to get the total advance to come in at a somewhat safe rpm: If you rev an engine up to peg out the stock centrifugal advance you'll be at over 4000 rpm with your face right next to the fan, and that bothers me... By removing one of the stock springs, the "peg-out" rpm drops to about 2000-3000 rpm so you can set up and adjust your total timing with less risk of having a fan explode in your face. On a modified distributor with a quick performance curve there is no need to pull a spring off. Pulling the spring does not limit the curve - it only lowers the rpm at which the total timing occurs for the purpose of setting the timing.
Joe -
I've done quite a few dyno runs on various engines and I've done a lot of playing with total timing. Pretty consistently we see peak torque on a small block Chevy occur with timing at 34-36 degrees (34 on higher compression engines, and 36 on modest-compression engines). Fast-burn heads need less timing (28-32). But over 36 degrees the torque curve starts dropping off pretty quickly, and I've never seen better torque at 38 on a small block. Large-bore engines (454s and 455s) with lower compression and at high altitude are the only exception I've seen - these engines will easily take 38 degrees total timing for a measurable improvement in power and torque.
Lars
Joe -
I've done quite a few dyno runs on various engines and I've done a lot of playing with total timing. Pretty consistently we see peak torque on a small block Chevy occur with timing at 34-36 degrees (34 on higher compression engines, and 36 on modest-compression engines). Fast-burn heads need less timing (28-32). But over 36 degrees the torque curve starts dropping off pretty quickly, and I've never seen better torque at 38 on a small block. Large-bore engines (454s and 455s) with lower compression and at high altitude are the only exception I've seen - these engines will easily take 38 degrees total timing for a measurable improvement in power and torque.
Lars
08-06-2008, 05:16 PM
#9
Safety Car
Joe -
I've done quite a few dyno runs on various engines and I've done a lot of playing with total timing. Pretty consistently we see peak torque on a small block Chevy occur with timing at 34-36 degrees (34 on higher compression engines, and 36 on modest-compression engines). Fast-burn heads need less timing (28-32). But over 36 degrees the torque curve starts dropping off pretty quickly, and I've never seen better torque at 38 on a small block. Large-bore engines (454s and 455s) with lower compression and at high altitude are the only exception I've seen - these engines will easily take 38 degrees total timing for a measurable improvement in power and torque.
Lars
Agree that fast burn heads need less total spark advance, and larger bore (wedge head) engines need more.
As you know, piston crown config makes a difference, too, because a flattop piston allows faster flame propagation than a domed crown. Do you take this into account? "Squish" also helps, because more "squish" (less piston to head clearance) adds turbulence. Do you factor this in?
Here's my build:
4.030 x 3.25 (331 SBC)
"30-30" cam: 254/254 .485/.485 110/118/114
11.0:1 measured C/R static using Speed Pro forged pistons w/6cc domes
900 cfm racing exhaust with ported ramshorns
ported LT1 intake
750 cfm dual pumper Holley, no choke
Piston to head clearance: .028
461 Double hump heads, ported, 2.02/1.60, chambers(??)cc'd equalized, polished, port matched, valves unshrouded, 3 angle, Manley SS racing valves, backcut
You're saying that 38 degrees is too much?
Have you tested anything similar to this?
Are you suggesting 34, or 36 for WOT full load torque peak? Why?
Joe
Last edited by 65tripleblack; 08-06-2008 at 05:21 PM.
