Distributor change suggestions

[matman1972]

I am currently running a 1915 with a weber progressive 32-36, a scat c35 cam, 040 heads, and an .89 4th gear. I currently have an 009 distributor on it, and have the flat spot on takeoff that one would expect, but when accelerating on the highway, I also see a large drop in throttle response after shifting into 4th. Once I hit 60 or so and shift, engine feels weaker. I was figuring, since 4th takes rpm down under 3k, I may not be getting the advance I need. Was considering going over to a svda by petronix or similar ( Mallory if I get ambitious) to see if that would help.
Any suggestions?

[saab9k]

Do you have a fuel/air gauge.
A 13.2 cruising
Full throttle, 12.5 to 12.8.
should get you rolling.
Total advance should most likely be 28 or so. All depending on octane and compression.
I would have it run on a dyno if it was mine.

[matman1972]

I do not, I have adjusted the carb using redlines guide, plug color and feel which of course is going to be more inaccurate. I have looked before (when pulling my hair tuning the carb) at installing o2 sensors and a gauge but never did.
My full advance is set at 28 degrees.
Plugs look just a tad on the dark side, and WOT will cause a slight pause on highway. Could be that knowing more about what's going in the cylinders will help me more than just swapping the dist.

[DeathBySnuSnu]

The single progressive has been the most difficult to tune for me. But that was many years ago. Any tools or experience you can find will be what you need.
The 009 distributor advance curve don't seem to really match anything. I got away with one on a fast reving lower geared vehicle.
There are some vac advance distros that work better with a single carb. But I have only read about it never set one up.
I am working on going fully distributer less.
Full program ecu. Fuel injection and all.
You may want to look into a mega squirt or a mega jolt.

[matman1972]

The single progressive has been the most difficult to tune for me. But that was many years ago. Any tools or experience you can find will be what you need.
The 009 distributor advance curve don't seem to really match anything. I got away with one on a fast reving lower geared vehicle.
There are some vac advance distros that work better with a single carb. But I have only read about it never set one up.
I am working on going fully distributer less.
Full program ecu. Fuel injection and all.
You may want to look into a mega squirt or a mega jolt.

Well, that should let you program your entire curve pretty well. I have been researching the progressive/ svda setup but like I said, I do not know for 100% certain if I'm looking at a mixture issue, the 009 not advancing when rpm's drop in 4th, or what. Unfortunately the guy who built my engine (Ron Hunter) passed away a few years ago or I'd just go over for a visit and get his opinion on where to start.
The single progressive is, by far, the most challenging I have tuned.
Maybe I need to just plan to keep my highway cruising under 80.

[DeathBySnuSnu]

When my stroker motor was in a low geared car and also the first year in the trike with normal freeway flyer type 3.88 ring and pinion.......I had no idea that I had a flat spot. It just blew through the gears as fast as I could shift it. Actually in the trike it physically took longer to shift into the gear than the amount of time I was using the gear.
I went to a taller 3rd and 4th and changed to a 3.44 ring and pinion. Now that I have to pull a gear for more than a second or two I can tell I have a flat spot. I can back the timing down to around 20 and the low end and flat spot is all good but it won't scream out. Put the timing back up at 30 and it screams but flat spot is back.
I am not a fan of the 009 anymore....

[matman1972]

I may go ahead and get the svda, but also an air/fuel gauge. I would like to see what else is happening on the road while I'm doing my regular driving. I don't want to put one in the dash, because after I get it set up it would just be another light I ignore, but, a stand alone wideband unit like ngk powerdex seems like it would be useful.
I have read that the short exhaust on our vw's will mess up readings with these, anyone else running a similar gauge connected to O2 sensor?

Everything runs pretty well, but I am taking my daughter on a cross country ride for her graduation this summer and, with that much highway time, I'm predicting this getting on my nerves.

[matman1972]

Another thought. I do not have preheat hooked up to the intake. This could also be hurting my performance. The Weber centermount has a place to put heat tubes, but exhaust does not. Might think about fixing this as well.

[matman1972]

Ok. In the spirit of "one change at a time" so I can actually measure the results, I ordered some more 5/8 tubing. My zoom low four into two exhaust has no heat riser connection. I'm going to go ahead and weld on a set and make flanges to run heat to my carb manifold. Figure I'll go next to the head on the left and right before the muffler on the right to get actual airflow. While they are out, I'mgoing to weld in an O2 bung and order a self contained wide band ratio meter. THat way I can see more accurately what is going on. The heat riser needs to be done anyway because I am realizing a lot of my symptoms could be caused by condensation of fuel before the head. Once I see how this affects things and I know my mixtures are right I'll revisit the distributor issue.

[rbourne3]

Just out of curiosity, How tall are your tires? I had a type 4 2366cc motor that dogged in 4th when I put 29" tall tires on it. I went back to 26.5" and everything was fine again. I find about 26" tall is the sweet spot.

[DeathBySnuSnu]

My tires are 24-7/8 dia.
1.26 third
0.82 fourth
3.44 ring and pinion
2110 cc engine
No problem pulling high gear. Only limiting factor is my will of self preservation.
What amount of hp do you estimate your type 4 at?

- - - Updated - - -

Ok. In the spirit of "one change at a time" so I can actually measure the results, I ordered some more 5/8 tubing. My zoom low four into two exhaust has no heat riser connection. I'm going to go ahead and weld on a set and make flanges to run heat to my carb manifold. Figure I'll go next to the head on the left and right before the muffler on the right to get actual airflow. While they are out, I'mgoing to weld in an O2 bung and order a self contained wide band ratio meter. THat way I can see more accurately what is going on. The heat riser needs to be done anyway because I am realizing a lot of my symptoms could be caused by condensation of fuel before the head. Once I see how this affects things and I know my mixtures are right I'll revisit the distributor issue.

I think you are on the right track with the one change at a time. I am bad at not following that rule. The long intakes do need the heat on them. I have had them ice up bad.

[matman1972]

I'm running 27" tall tires

[matman1972]

I think you are on the right track with the one change at a time. I am bad at not following that rule. The long intakes do need the heat on them. I have had them ice up bad.

I usually have difficulty with it too. I get in a hurry and come up with 3 or 4 changes I want to make.

[matman1972]

Got some 5/8 inch steel tubing. I was looking online at a set of pipes similar to mine with heat riser ports already on them. I noticed on both ones I looked at, the heat riser connections were both near the head, not one on the head and one near the muffler to encourage airflow rather than pulsing. I figured, I'd just keep mine since they are still in good shape, just in need of a new paint job. Anybody else here running pipes with both connections for the heat risers near the heads? Do they warm up intake well?