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recurve Duraspark distributor

tarafied1

tarafied1

Well-Known Member
I have been playing with the timing on the 429. It's 10.5:1 CR with a mild cam: Dur. @.050” 218/228, gross valve lift .509”. I run 93 octane pump gas. When the engine is warm and under a slight load it pings. So I was going to take out some of the vacuum advance. But first I wanted to check my base line.
I have a stock Ford Duraspark distributor. It was set at initial 14 degrees, and had the stock heavy springs that kept the mechanical advance from coming in quick. My damper only goes to 30 degrees BTC so I am guessing when I say total was upper 30's. The reluctor was the 15L/21L and was in the 15L side. That should mean 15x2=30 so at 14 initial and 30 degrees mechanical, I should have been at 44 total. It seamed to run okay but top end was noisy so I thought I would address that too.
So I took a reluctor from a 5.0 I had which was a 10L/13L. I put it in at 10L (10x2=20). I put in the silver springs which were supposed to be all in by 2800rpm. So I played with it and it liked as much as 18 degrees initial (with the reluctor set at 10L it should be 20+18 or 38 total). It's all in at 2000 rpm and looks like low 30's total. Not much past the 30 degree mark. Might need to flip it to the 13L side for more total.
I also turned the vacuum advance out two turns. Took it out for a spin and after it warmed up It felt just as strong as before on the bottom and now I can rev until I float the valve springs.
I think I will leave it this way for a while. Some day I might take to a test and tune night. With the old converter and the timing the way it was, I could only get it into the 13's. 60 foot times were bad. With the higher stall and recurved dizzy I would like to see where it's at. After the Bobcat is running I am pulling the C6 and putting in the TKO.
 
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Craig, you may be interested in the following. I've seen the following several times on another site by barnett468 who is a full time car restorer and engine builder of many years. In his description you will see that he says to disconnect the vacuum advance and plug the line. In other posts he explains that vacuum advance is only used to improve fuel economy and does not improve performance. I've seen other of his posts explaining how to tune carbs. I like his method because he gives very specific step by step instructions.

SETTING TIMING CURVE
Before you start driving it normally, I would set the timing curve so it is optimum for your particular setup . Below is just one way to do that.

1. Disconnect and plug the vacuum hoses to the dist if you have any and leave them plugged permanently or until further notice.

2. Start your timing at 10 degrees BTDC.

3. With the engine idling, advance the timing 4 degrees . Listen for an increase in rpm and irregular/rough running.

4. If the rpm increases and it still runs smoothly, reset the idle speed then increase the timing 2 more degrees and check for the same things.

5. Retard timing to 10 degrees.

6. Reset the idle speed.

7. Increase the rpm to around 2000 then advance the timing 4 degrees . Listen for an increase in rpm and irregular/rough running.

8. If the rpm increases and it still runs smoothly, reset the engine speed to 2000 rpm then increase the timing 2 more degrees and check for the same things.

POST RESULTS


TEST DRIVING

After setting the curve you can do the following test to see if you have too much advance.

Get the engine up to operating temp.

Drive at around 20 mph in second gear for a few seconds then floor the gas pedal as fast as you can until you reach around 30 mph and listen for even the faintest pinging sound coming from the engine . If it pings, you have too much timing for the octane gas you are using . You can either reduce the timing some or use a higher octane . The highest timing level you can run without it pinging and/or running erratic will SAFELY provide the most power.

It may ping in hot weather even if it does not in cold weather . If you find this to be the case, the easiest thing to do is reduce the timing until it stops or try higher octane gas . If it still pings with the highest octane gas, you can reduce the timing then.


JETTING

It may be rich or lean . If you installed new spark plugs, I would remove the front plug from each bank and post photos of them.

Black porcelain is rich.

Nearly white is lean.

Very light tan is typically very good and suggests the jetting is very close if not ideal.
 
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thanks. I sort of did some of that. I of course disconnected the vacuum during the timing checks. I did play with timing at various rpms. I do need to check the plugs.
 
drove it to Nashville today in almost 100 degree heat with very humid air. It never pinged once on hills, part throttle, anything! I think it's better, top end feels stronger. That is only seat of the pants feel, however, I'm happy with the changes.
 
The Duraspark was used on emission controlled motors the had EGR. To offset some of the side effects of the EGR, Ford pulled in a lot of vacuum advance, up to 60 degrees. What vacuum source did or do you have it connected to? Typically it would be connected to manifold vacuum. Again to improve driveability and fuel economy. With full manifold vacuum under light load you will have a lot of vacuum advance and heavy load such as going up a hill, the manifold vacuum drops as well as the amount of timing. You need to be careful with ported timing. In some cases it comes off the venturi. The more air going through the venturi the more vacuum advance you pull in regardless of engine load. Most of the time ported just stops valve advance at idle. Ported vacuum advance was only an emission era set up for late timing to keep the exhaust gases burning while going into the exhaust manifolds.

I use to work in a Chevy dealer in the mid 70's. It was a night and day difference in emission controls when catalytic converters came out. The 74 cars went from all sorts of vacuum advance controls, such as ported, temperature and high gear only to full manifold advance and no controls in 75 with the cat.

My dad had a 77 Grand a with a 302. Same as the Chevy of the day. Full manifold vacuum advance all the time. The only emission controls was a vacuum controlled EGR. With the EGR hooked up it did not ping. If you disconnect the EGR, it would ping uncontrollably as soon as you stepped on the gas.
 
I have the vacuum hooked up to my Holley above the throttle plate (in the side of metering plate) so I guess you would call that ported or timed. It's not full manifold vacuum. I don't know how to measure how much vacuum advance is coming on unless I get someone to ride under the hood with the timing light! But seriously, I do know now I had too much advance under light load. It's currently a C6 auto but I am switching to a TKO. Do you recommend full manifold vacuum?
I never really played with the timing curve before either. I think I had too much total but also it was coming on late. The engine always had plenty of low end torque but top end wasn't as strong as I thought it should be. The changes have really helped. I did order a timing tape for the balancer so I can get better reading above the 30 degree mark (that's where it ends).
I drive it anywhere and in any weather so it always bothered me when it would ping under light load. I always figured it was the high CR and poor gas. I honestly didn't know I could adjust the vacuum canister. I probably should have just converted to a MSD or something but I like a challenge. The box is supposed to retard timing -6 degrees when cranking and it must because I would think at 18 initial it wouldn't crank over but it does. I suspect I have limited the total too much and maybe it's coming on too quick (just by the numbers I logged) but it runs better. Once I have the timing tape installed I will change one of the spring to a little heaver and maybe flip the relucter arm to the 13L side. It's a pain to get that littl clip out of there! But then I want to take it to the track and see if it is just my butt that likes it or if the numbers have improved. It's no race car but I want to perform at its best!
 
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What heads do you have? 429/460 Fords don't like a lot of total timing even with iron heads. Most of the time anything over
38 total is too much. Some of the aluminum heads like the SCJ's and Kaase's need even less. Scotty J (Mad Porter) ground my cam and he recommended 18 initial and 18 advance for a total of 36 and have it all in by 3000 rpm. I have Blue Thunder aluminum CJ's. I am at 10.6 cr and cam is a bit larger than yours (your dynamic cr is probably higher than mine). His recommend was dead on. I use manifold vacuum for my vacuum advance, with the vacuum can limited to 10 degrees. It really helps clean up the idle and light cruise, but as soon as you crack open the throttle at all, it goes away. I know you mentioned Scotty on another thread, get his recommend on your timing. That guy really knows his big blocks, I couldn't be happier with my cam. I didn't think mine would start at 18 initial either, but it does fine and with no retard box.
 
that's a great article. It confirmed pretty much everything I just did!
I am going to play with full manifold vacuum vs. timed or port vacuum. I'm curious which will feel better or if I can even notice a change. I have had this car 26 years and I have always had it in the timed or port location on my Holley.
 
angrywombat said:
What heads do you have? ... I know you mentioned Scotty on another thread, get his recommend on your timing. That guy really knows his big blocks, I couldn't be happier with my cam. I didn't think mine would start at 18 initial either, but it does fine and with no retard box.
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I have D0VE C iron heads right now. I am talking to him about a cam as well. He does know his stuff. He is the one that got me thinking I was leaving power on the table!
 
he recommended backing off the vacuum advance and 36 total. He also told me to get total by 2800rpm. I need a timing tape to validate total. I might have it coming in too quick but it seams to like it. He recommended more cam since I have a lot of static CR
 
angrywombat said:
429/460 Fords don't like a lot of total timing even with iron heads. Most of the time anything over 38 total is too much. Some of the aluminum heads like the SCJ's and Kaase's need even less. I have Blue Thunder aluminum CJ's.
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what do you think about the Edelbrock heads? Scotty said they aren't too bad. I want to shave off some weight on the nose but I am not looking for a high RPM screamer. I think the SCJ style ports and valves are way too big for my application. The Eddy's will work with my Performer intake and headers.
 
Yeah, 10.5 with a small torque cam, your dynamic cr is probably REALLY high for iron heads. He will probably give you a lot more duration on the cam to get that down to pump gas levels. Today's 93 octane does not perform as well as older pre ethanol 93 either.

You will not be disappointed with a cam from Scotty. I was amazed at how much better mine is over the off the shelf cams I have used for years. I had him do a similar grind to the one he runs in his LTD. It's a hydraulic roller lobe type profile but I run solid rollers with a very tight lash. That avoids the angularity problems of trying to run the taller hydraulic roller lifters in a 429/460.
 
Don't have any experience with the Eddy's. The blue thunders are my first foray into alloys. All my previous builds have used DOVE, C8VE and DOOE's. I got a killer used price on the blue thunders, that's why I ended up with them. I was going to use the SCJ's from Scotty with the intake valve backcuts. I wouldn't worry about the valve and port sizes on the SCJ's, these engines like to breath. The more the better.

Carl of Cars by Carl seems to really like the Edelbrocks and honestly I have always been very happy with anything I have gotten from Edelbrock.
 
angrywombat said:
Yeah, 10.5 with a small torque cam, your dynamic cr is probably REALLY high for iron heads. He will probably give you a lot more duration on the cam to get that down to pump gas levels. Today's 93 octane does not perform as well as older pre ethanol 93 either.
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yeah, that's kind of what he told me too
 
angrywombat said:
Don't have any experience with the Eddy's. The blue thunders are my first foray into alloys. All my previous builds have used DOVE, C8VE and DOOE's. I got a killer used price on the blue thunders, that's why I ended up with them. I was going to use the SCJ's from Scotty with the intake valve backcuts. I wouldn't worry about the valve and port sizes on the SCJ's, these engines like to breath. The more the better.

Carl of Cars by Carl seems to really like the Edelbrocks and honestly I have always been very happy with anything I have gotten from Edelbrock.
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I just don't want to have so much flow that it looses it's bottom end. I rarely rev it so I love the grunt!
 
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