Darwin's New Distributor

[Darwinskeeper]

I broke down a few weeks ago and ordered a new Performance Distributors' DUI distributor for my little red wagon. I haven't done enough driving to nail down the distributor's effect on fuel economy, but I can tell that the engine seems to be running a lot smoother, particularly at idle. One curious thing is that Performance Distributors' recommends attaching the DUI's vacuum cannister to manifold vacuum (as opposed to a vacuum port on the carb) I suspect that the smoother idle may be attributed to that. The throttle response also seems better.

 

[mhamilton]

More advance at idle is generally better. Though, asking opinions on ported vs. manifold vac is like opening pandora's box. I'm not sure what the ESC spark curve looked like with the 4.3, but I'd guess it had lots of advance at idle.

The 3.3 and 3.8 Chevs were the only ones to have a vacuum control valve for the dist advance. It took both ported and manifold vac. At idle, it gave the dist 5" of vacuum from manifold. Once ported got over 5", it switched over to that. Probably to help the idle on those rough engines.

I'm interested to know how your economy works out with the new dist. I just got back from a 1000 mile trip to NJ, with a fresh air filter and restored HEI, my 229 made 24 mpg with an average of ~73 mph.

 

[Darwinskeeper]

24mpg at an average of 73mph? I'm green with envy. :mrgreen: The best I've been able to get was 23.92mpg when I was cruising at 65mph during last Summer's road trip. Maybe I shoulda gone with a 229.

My first two tankfuls have been less than impressive, 16.36mpg and 16.44mpg respectively. I need to hit the road to really get an accurate test, but my present overtime situation is forcing me to keep close to home. Hopefully Memorial Day weekend will give me an excuse to do a little road testing.

 

[Darwinskeeper]

24mpg at an average of 73mph? I'm green with envy. :mrgreen: The best I've been able to get was 23.92mpg when I was cruising at 65mph during last Summer's road trip. Maybe I shoulda gone with a 229.

My first two tankfuls have been less than impressive, 16.36mpg and 16.44mpg respectively. I need to hit the road to really get an accurate test, but my present overtime situation is forcing me to keep close to home. Hopefully Memorial Day weekend will give me an excuse to do a little road testing.

 

[mhamilton]

Hmmm... maybe with the 2.7 gear you have you're at the same RPM I run at 70-75 mph with the 2.4 gear? I think I'm around 2400 rpm at 70.

This 24 mpg is the best I have ever seen with the 229. Probably could get the EPA 26 mpg if I was going 55 mph. I think it has to do with the rebuilt HEI. I fixed the advance and replaced the springs with good stock units, so the centrifugal curve is exactly what the GM manual calls for. It does not start advancing until around 1300 rpm.

 

[Darwinskeeper]

I've always had mixed feelings about ultra high gearing. I imagine that it would keep the revs down and the mileage up on the highway, but it would seem to drop the engine speed a little too much for around town driving. Even with the new cam and distributor (which seem to help) I notice Darwin get a little uncomfortable below 35mph in 3rd gear (1:1) with 2.73 gears, I don't think I want to know what that would be like if she was pulling 2.41 cogs.

My eventual plan is to split the difference and fit a production Ford Mustang 5.0 T-5 (3.35, 1.93, 1.29, 1.00, .675) with rear gears in the 3.23-3.42 range. That way I'll be in the 1320-1400rpm range at 30mph and still run about 400rpm lower on the highway, helping both around town and highway mpg. :twisted: At least in theory, now if only I could have a little luck making it work out in practice.

 

[mhamilton]

Right, I'm not even sure GM used the high 2.4 gearing with a manual trans. With the 2.41 and auto, the converter just lets it roll along in 3rd.

Are there adapters to make the Ford trans work on a sbc? Or is that the issue you are dealing with for the swap?

I guess in the worst case, you can always put in a TH 2004r or 700r4 with the ~3.5 axle.

 

[80ECLT]

Right, I'm not even sure GM used the high 2.4 gearing with a manual trans. With the 2.41 and auto, the converter just lets it roll along in 3rd.

Are there adapters to make the Ford trans work on a sbc? Or is that the issue you are dealing with for the swap?

I guess in the worst case, you can always put in a TH 2004r or 700r4 with the ~3.5 axle.

Thats your best bet, overdrive and a 3:42 gear combo. low enough gearing for the city, and overdrive for low rpm's on the hiway!

Im actually looking into an electronic overdrive modual to put behind my Saginaw 4 speed. Sort of like a Corvette 4+3 trans. You know me... always having to be different! LOL!
dancin_banana.gif

 

[Darwinskeeper]

Lakewood makes the 15032 Bellhousing that will allow me to attach the Mustang T-5 (which is more available than the Camaro V8 T-5) to a small block Chevy (or Chevy 90 degree V6).

The other trick is that I will need a custom welded stick to move the shift stick fwd and allow me to keep an unmodified bench with the aft location of the Mustang's internal shifter. I've already sketched out a rough idea that should work.

 

[freaktrucker]

http://wichita.craigslist.org/car/691691025.html just saw this would make a pretty good donation
for that 5 speed