Best way to proceed with improving up 427 Windsor street setup

[blykins]

X2....

Most performance applications in general respond very well to a quick timing curve. I would set the total timing to be all in by about 2600-2800.

[Pman1961]

You are welcome ACE!! Thanks for not telling all I crossed a pair of wires on the distributor cause a nice little pop at our first crank!! Brent I agree with the earlier full timing. Again, the Internet provides so much advice not all being the same which makes making decisions difficult. The tuner and an article I read recently recommended full timing at 3000 on this size stroker engine. We can swap some springs no problem to achieve the specs you are suggesting.

[Ace23]

Originally Posted by RET_COP

Sounds like you put a light silver in. Good move, go quicker and try two blue springs, light stick shift cars like the cobra respond well to this advance curve. Going in the right direction, good luck!

That is correct. The cap had 2 heavy silver springs and we changed one to the lighter silver spring. This resulted in full advance coming in at around 3000rpm compared to the previous 3500rpm. Thanks for the advice

Originally Posted by blykins

X2....

Most performance applications in general respond very well to a quick timing curve. I would set the total timing to be all in by about 2600-2800.

As Perry noted we can change to the 2 blue springs and see where that gets us. I do have a question as I do not completely understand timing and what effects it can have. If we changed the springs and full timing comes in 2600-2800 what happens when you are cruising on the interstate at 2500-3000rpm? Is it a bad thing to be at a cruising speed with full advance? I do not want this to be about gas mileage but will I see any improvement if I am running the lighter springs and my timing is more advanced at a lower RPM state?



I did find this write up and just thought it was interesting.

TIMING AND VACUUM ADVANCE 101

The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as idle mixture is affected by exhaust gas dilution. This requires that lean mixtures have "the fire lit" earlier in the compression cycle (spark timing advanced), allowing more burn time so that peak cylinder pressure is reached just after TDC for peak efficiency and reduced exhaust gas temperature (wasted combustion energy). Rich mixtures, on the other hand, burn faster than lean mixtures, so they need to have "the fire lit" later in the compression cycle (spark timing retarded slightly) so maximum cylinder pressure is still achieved at the same point after TDC as with the lean mixture, for maximum efficiency.

The centrifugal advance system in a distributor advances spark timing purely as a function of engine rpm (irrespective of engine load or operating conditions), with the amount of advance and the rate at which it comes in determined by the weights and springs on top of the autocam mechanism. The amount of advance added by the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it has no part in the "total timing" equation.

At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum - more on that aberration later) is activated by the high manifold vacuum, and adds about 15 degrees of spark advance, on top of the initial static timing setting (i.e., if your static timing is at 10 degrees, at idle it's actually around 25 degrees with the vacuum advance connected). The same thing occurs at steady-state highway cruise; the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed, and if you had a timing light set up so you could see the balancer as you were going down the highway, you'd see about 50 degrees advance (10 degrees initial, 20-25 degrees from the centrifugal advance, and 15 degrees from the vacuum advance) at steady-state cruise (it only takes about 40 horsepower to cruise at 50mph).

When you accelerate, the mixture is instantly enriched (by the accelerator pump, power valve, etc.), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off the gas and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean.

The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic.

Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.

If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.

What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.

For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts.

[blykins]

Not bad at all. In fact, it's better...

Think about guys running vac advance, which gives an additional amount of advance to the mechanical. At cruising rpm/speed, these guys are seeing WAY more than what you would see.

[Ace23]

Originally Posted by blykins

Not bad at all. In fact, it's better...

Think about guys running vac advance, which gives an additional amount of advance to the mechanical. At cruising rpm/speed, these guys are seeing WAY more than what you would see.

Well we changed the springs and ended up with full advance around 2800rpm. We were able to put about 20 miles on the car and I woud say everything we did was an improvement to the car. We pulled it to 7000rpm and in my opinion about 6000rpm you get the oh sh** feeling. I'm very happy with the improvement but thats alot of RPM to get to before you feel like your actually in a fast car. With my current gearing we were knocking on 130mph at 7000rpm in in 3rd. I'm all for fast stuff but thats hauling butt on the street and I don't think thats something I want to do in the car everytime I go for a drive. Feels good to know the motor must be pretty solid still so lets continue on with this saga.

*Headers- jus as many people and articles on how big headers are better as there are that small headers are better. Up is down and down is up.

*Gearing- I believe I have the .82 TKO-600 and the car has 3:31's in it. Gearing has really been mentioned in this thread but I think this is something that could be overlooked. The first thought I have is that 3:73's would be a good move but I've read some interesting threads on 4:10's. The fastest I would cruise is 70mph but the majority of my driving is under 70mph.

*Camshaft-From what you have said this is a big culprit if not the biggest. Current dyno shows the motor peaking at 6600rpm. I like winding the motor out but with these gears and 7000rpm its a pretty good stretch and nothing feels like its happeniing until you are 5500-7000rpm "which is exaclty what you said the cam should be like"

[Ace23]

Originally Posted by blykins

Not bad at all. In fact, it's better...

Think about guys running vac advance, which gives an additional amount of advance to the mechanical. At cruising rpm/speed, these guys are seeing WAY more than what you would see.

Originally Posted by blykins

Not bad at all. In fact, it's better...

Think about guys running vac advance, which gives an additional amount of advance to the mechanical. At cruising rpm/speed, these guys are seeing WAY more than what you would see.

Well we changed the springs and ended up with full advance around 2800rpm. We were able to put about 20 miles on the car and I woud say everything we did was an improvement to the car. We pulled it to 7000rpm and in my opinion about 6000rpm you get the oh sh** feeling. I'm very happy with the improvement but thats alot of RPM to get to before you feel like your actually in a fast car. With my current gearing we were knocking on 130mph at 7000rpm in in 3rd. I'm all for fast stuff but thats hauling butt on the street and I don't think thats something I want to do in the car everytime I go for a drive. Feels good to know the motor must be pretty solid still so lets continue on with this saga.

*Headers- jus as many people and articles on how big headers are better as there are that small headers are better. Up is down and down is up.

*Gearing- I believe I have the .82 TKO-600 and the car has 3:31's in it. Gearing has really been mentioned in this thread but I think this is something that could be overlooked. The first thought I have is that 3:73's would be a good move but I've read some interesting threads on 4:10's. The fastest I would cruise is 70mph but the majority of my driving is under 70mph.

*Camshaft-From what you have said this is a big culprit if not the biggest. Current dyno shows the motor peaking at 6600rpm. I like winding the motor out but with these gears and 7000rpm its a pretty good stretch and nothing feels like its happeniing until you are 5500-7000rpm "which is exaclty what you said the cam should be like"

[RET_COP]

I have the same trans and rear gear you have. It is nice cruising 73mph at 2500 in 5th with a useful 1st gear. Autocross in 2nd 25mph 2000rpms- 55mph 4500rpms so not too bad. I thought of 3.55 but the guys here talked me out of it (for now) and I'm glad they did. With the .82 5th and a light car with a big CI motor I'd say your in a good range. 4.10s forget it unless your drag racing.

[blykins]

Originally Posted by Ace23

Well we changed the springs and ended up with full advance around 2800rpm. We were able to put about 20 miles on the car and I woud say everything we did was an improvement to the car. We pulled it to 7000rpm and in my opinion about 6000rpm you get the oh sh** feeling. I'm very happy with the improvement but thats alot of RPM to get to before you feel like your actually in a fast car. With my current gearing we were knocking on 130mph at 7000rpm in in 3rd. I'm all for fast stuff but thats hauling butt on the street and I don't think thats something I want to do in the car everytime I go for a drive. Feels good to know the motor must be pretty solid still so lets continue on with this saga.

*Headers- jus as many people and articles on how big headers are better as there are that small headers are better. Up is down and down is up.

*Gearing- I believe I have the .82 TKO-600 and the car has 3:31's in it. Gearing has really been mentioned in this thread but I think this is something that could be overlooked. The first thought I have is that 3:73's would be a good move but I've read some interesting threads on 4:10's. The fastest I would cruise is 70mph but the majority of my driving is under 70mph.

*Camshaft-From what you have said this is a big culprit if not the biggest. Current dyno shows the motor peaking at 6600rpm. I like winding the motor out but with these gears and 7000rpm its a pretty good stretch and nothing feels like its happeniing until you are 5500-7000rpm "which is exaclty what you said the cam should be like"

The characteristics of your engine are what I look for with my own personal stuff. I like the higher revving pieces....

If I owned your car, I would stick a 4.10 gear in it and reap the benefits.

Otherwise, you'll have to make a decision on where you want the power to be and how you want to drive the car, then make it do what you want.

[Ace23]

Originally Posted by blykins

The characteristics of your engine are what I look for with my own personal stuff. I like the higher revving pieces....

If I owned your car, I would stick a 4.10 gear in it and reap the benefits.

Otherwise, you'll have to make a decision on where you want the power to be and how you want to drive the car, then make it do what you want.

If you went with 4:10's would that eliminate the need to swap the cam? I bet a T56 would be needed if you intended to have a hwy gear of if you wanted to be able to cruise at 70mph at a rational rpm. In a nutshell I do like the higher rpms and everything that comes with that I just don't want to have to be breaking mach 1 to feel like the car is moving. I want more acceleration not top speed. If my car topped out at 140mph I wouldn't care. We are going to have to do a little bit of carb adjustment as well as it was doing some lean backfires coming down from 7000K but we kinda expected that

[SPF1061]

Originally Posted by blykins

X2....

Most performance applications in general respond very well to a quick timing curve. I would set the total timing to be all in by about 2600-2800.

I have a question about the MSD mechanical advance adjustments. I have been running the heavy silver springs in my 427R and am going to switch to the blue springs to see how the engine likes it. No one has mentioned the bushings. I have the black bushings in mine. Is it ok to leave those with the blue springs or is it best to use a different bushing. If I understand correctly the bushing sets the amount of advance the spring weights add, so in effect, if I set my timing all in (32/34 degrees) the bushings set the amount of initial advance. Black bushing would be 14/16 degree initial timing with 32/34 all in. Different bushings would give me less initial timing for the same all in timing. Thoughts?

[blykins]

Look at MSD's charts. You may have to manipulate both bushing and springs.

[jhv48]

The bushings limit how many degrees the timing advances. I believe the black bushing is 18 degrees. The springs limit how fast or slow the timing advances as you rev the engine (lighter springs, faster advance). The initial timing is set by you at idle. So, 16 degrees initial timing plus 18 degrees added from the black bushing nets you 34 degrees total. The springs control at what rpm that total advance is reached.

Clear as mud, right?

[Ace23]

Hope everyone had a nice Thanksgiving. Pman and I took out the car for a 75 mile cruise last Wednesday night as this was my first time in the drivers seat since getting the car back on the road. The car ran great and the most interesting thing of the night was that the car appeared to be getting about 15-16mpg and previously it was getting about 9-10. I am going to test it again but that was really a big improvement. I made some pretty good pulls in the car and was shifting around 6900rpm.....the high rpm's are really growing on me and I think I can learn to enjoy the car for awhile the way it is. I will just have to teach myself how to drive something that requires higher RPMs. I came from a car that was making 530rwtq at 2500rpm so it is ust a completely different feel. I'm going to put a bit more seat time in it but I'm kicking the idea around of trying out a new gear ratio. With the .84 5th gear I have I think 3.73 may be a good start for me. I have printed out a few different rear ratio options and I'm going to review. I really don't want to get into any major changes right now I just want to have fun with the car. I figure the 3.73 gear would be inexpensive and something relatively simple and quick to change. If it turns out I don't like it I can go back to the 3.31's. We are also still tossing around the header change and what is involved......I don't think I have ever been so on the fence about what the results would be on a part swap. I've watched about every header test on youtube and searched every 1-3/4 vs 2" header test on forum that I can find. My heads are Brodix Track 1's and that may pose a challenge in requiring custom headers