Weber 38 DGES and Kit 490 Installation and Operation Review by Thomas Hardman

Thomas J. Hardman, Jr

thardman [at] thomashardman.com

VaraJet to Weber 38 DGES Swap Notes and Remarks

Here is a diagram of the vacuum and vapor/emissions system as originally sold by Jeep. Click for a huge copy of the same image:

Sealing the Air-Cleaner Housing to the Carb

View of "emergency gasket".

Needless to say, this obviously doesn't work. Now we will have to get that gunk off of the mounting bracket.

Below are some details of various angles, showing hoses attachments, various manifold vacuum ports, etc.

In the image directly below, the vacuum hose shown running from the bottom of the carburetor is attached to the wrong connection. In the middle of the picture is a rubber cap on the end of a metal tube, near where the carburetor fuel bowl vent hose joins other lines. That rubber cap had to be removed, and relocated to the place where the hose from the bottom of the carburetor was attached. The place where the hose from the bottom of the carburetor must attach to where the rubber cap was, that is a metal tube leading to the rear of the engine, where it fits the hose to the distributor vacuum advance.

Detail of mounting bracket (removed from carb, 4 small nuts with lock washers hold it to the carb top), Air Cleaner housing, and hand-made gaskets.

I had to go buy a roll of oil/gas-resistant gasket material and cut these gaskets by hand, in layers. Each layer is a tiny bit different, though all are based on tracing around the mounting bracket and then some eyeball estimations, and a bit of clever work with scissors.

Once cut out and made nicely to size, the layers are made into a laminate gasket by very lightly coating the surfaces in a continuous bead of that blue silicone forms-a-gasket stuff. Do NOT put this stuff on so that the gaskets are glued to the carb or to the air-cleaner housing! You'll be sorry if you do! Just make sure the layers of gasket stick to each other and to nothing else, and don't laminate until you are sure you have enough layers to make the seal. Now place the mounting bracket back on the carb but don't secure the hold-down nuts. Then laminate as you place each layer onto the mounting bracket, but do not stick the gaskets to the carb or mounting bracket, only to each other. In this way you get perfect fit and placement of the gasket layers. Then bolt on the air-cleaner housing and let the goop dry for maybe 10 or 20 minutes.

In my case, when tightening down the mounting bracket, I didn't replace the 4th nut, which was on the passenger-rear side of the carb assembly. It was most of the problem. With the combination of hand-made gaskets and omitting that nut, I could get a tight seal. Please see a close-up.

Measuring the offending oversized mounting bracket.

Bottom of the air-cleaner housing.

"Re-shaped" air-cleaner cover.

After sufficient poundings with a hammer, the central dimple of the stock cover has been "adjusted". This took about 40 whacks with the hammer.

Comanche with a Load!

Cold Idle Kick-Up Vacuum Switch.

This is a strange little electrically controlled vacuum switch. The coiled hose, attached, goes to a diaphragm on the VaraJet, where it is located just in front of the linkage. In extremely cold weather, this would raise the idle. This electrical circuit may (or may not) be what should be adapted to operate the electric-choke assembly on the Weber 38 DGES. I had wanted the 38 DGAS (water thermostat choke) carb but this is what they shipped. Having waited for months to get this carb, I figured I'd just work with what I had.

Fully installed and ready to tune!

Post-Installation and Semi-Post-Installation

FUEL FEED

First, I have to admit that I didn't do this "properly". I didn't have all of the tools on hand, and I didn't have all of the parts in place at the right time. I also made some other mistakes, and perhaps the worst of those mistakes was doing this with extremely limited cash on hand for incidental "wasn't expecting that at all" purchases.

The carburetor arrived first, before the pressure regulator. That pressure regulator was a Holley 12-803 Low Pressure Fuel Regulator ("LPFR"). The day after the carburetor arrived (a week after payment to Carbs Only) I was told that the Holley LPFR was in and that I could come get it. Unfortunately, it shipped without the fittings. The fittings I needed were obtained from Applied Technologies in Gaithersburg MD, where they had them there one day after order. These were NTP fittings, which were very hard to find in the proper sizes. They have to be 3/8ths on the threaded end, and "barbed" on the smooth end which must fit 5/16ths interior diameter fuel hose.

For my setup I already had a "recirculation splitter" to keep fuel flowing through the pump and filter at all times. This has two main effects: the first is that gasoline doesn't stay cooped up and stagnated in hot hoses in the hot engine compartment, which prevents vapor-lock; the second effect is that before long all gasoline in your tank has been circulated through the fuel-filter. This results in clean gas, dirty filter, and the filter will have to be changed regularly.

Because of this recirculation splitter, I needed a block-end NTP fitting, also known as a "plug". One of the "hose barb" NTP fittings takes gasoline into the LPFR and one takes it on to the carburetor. Be sure to be extremely careful to have no gasoline leaks at all, and test your fittings for leaks by turning on the fuel pump. Short across the oil-pressure safety switch if you have to do this, but be careful that your short across the safety switch cannot spark or you could go up in flames along with your vehicle. If the fittings remain non-leaking after a few minutes at a time of running the fuel pump, turn off the power and remove the safety-switch short-wire so that the fuel pump will operate only when the oil-pressure switch indicates a turning engine and operating oil-pump.

N.B.: USE a pressure regulator. The carb will not run properly until you have a LPFR in place, and will not be usefully tuned until the fuel pressure is properly controlled. Set for 2.5 PSI, as per Weber's advice.

Eventually the fuel distributor system -- the regulator and related fittings -- started to leak a little around the edges. Careful application of Type I gasket sealer (or type 1, same thing) sealed the leaks. You might want to get everything into the final configuration and then go ahead and seal it once you are satisfied.

TUNING THE CARB

Follow Weber's advice on getting the fuel mixture correctly set. Keep in mind that on my vehicle, this takes two pairs of screwdrivers, and a lot of patience and a lot of caution. The rear-side idle mixture adjustment screw requires a screwdriver that has a short handle and short blade, altogether measuring about 2 inches long. Any longer and you can't get to it because it's too close to the distributor cap. On the front side, you need to be really careful and also need a fairly long-shaft screwdriver, because you have to get past the hot-water outflow pipe and thermostat on the intake manifold. This screwdriver also has to be short enough so that you don't get caught in the radiator fan, which will of course be turning as you make these adjustements. I might add that you probably don't want this screwdriver to have too broad a blade when trying to adjust the idle-speed throttle screw.

I should add that probably you should tune the carb once, drive it for a few days or a week to let it "settle in", and then tune everything again.

DRIVING

These notes should be considered as applying only to the upgraded GM Performance Parts "crate" 3.4L engine. If you still have the original 2.8L stock engine, "your mileage may vary".

First, let me point out that if you have an A-904 TorqueFlite as I do, that you will definitely want to reconnect the kickdown cable. If you don't, and shift manually, probably you will burn out your transmission in short order.

With the old VaraJet, and the stock engine, the way you got speed or power out of the engine was to hold down the gas pedal and let the rather large secondary throttle open. This would occur when the flow through the main throat was so restricted that it opened a vacuum diaphragm which previously locked shut the secondary throttle. The kickdown and full-throttle upshift points were set so that you could drop down into first at up to 25MPH or so, and first gear would wind out up to around 40MPH. Mostly you would be just working the engine severely and probably this contributes to the classic failure modes of the 2.8L V6.

With the new Weber 38 DGES, if you are sitting at a line and apply full throttle, you simultaneously open both throats. I think that the Weber 38 DGES doesn't have the full flow capability of the wide-open VaraJet, but you can get the full flow of the 38 DGES from a dead stop. Of course, this means that you will instantly lower the vacuum at the heads until the engine RPMs catch up.

The Weber 38 DGES is probably at its best at fairly low engine RPMs, and because it doesn't seem to have the top-end high-RPM flow rating of the VaraJet, you are much better off, and are strongly advised, to not just give it wide-open throttle. Where the VaraJet-equipped V6 works most powerfully when you use a combination of kickdown to lower gear and winding out the engine, the Weber 38 DGES works best -- for me, anyway -- when you give it about half-throttle. The linkage connection to the kickdown cable seems to be different from that of the VaraJet, so that you have to depress the pedal a lot harder to get a kickdown to the next lower gear, and the limiting speeds that govern whether or not the kickdown is possible seem to be set lower; this means that you can't kick down to first unless you're going less than 15MPH or so, in my experience. Also, in normal driving, it upshifts at about the same, but slightly lower, speeds as it did when the VaraJet was still in place. Taken all together, this means that you'll be doing a lot less winding out, and a lot more high-torque low-RPM rapid acceleration.

Low-flow low-RPM operations is where the Weber 38 DGES is a major improvement over the VaraJet. It seems to me -- I haven't made a huge statistical study out of it -- that with the Weber 38 DGES you will go just about as fast up to freeway speeds at about 1/3rd-throttle to half-throttle as you would with the VaraJet at full throttle. Indeed, starting from the line with the Weber "floored", I wasn't that much impressed with any sensation of major improvement. But starting from the line with the Weber at about 1/3rd or half throttle, I was very much impressed. The improvement of power at lower RPMS was such that you just let the transmission do the work in higher gears, rather than with the engine screaming in a lower gear.

This may be the single "drawback" of the Weber 38 DGES, and it's probably more particular to my specific situation. Simply stated, I may now have too much low-RPM torque for my old A-904 TorqueFlite transmission to handle it. In first gear, if I'm not careful, I start burning off my drive-wheel tire, and then when it drops into second, the over-torque seems to be more than the trans can accomodate quickly. The shift from first into second under any conditions should be instant and unambiguously sharp, which isn't presently the case. A transmission overhaul is probably overdue (170,000 miles or so), and might solve this problem. But the shift up to third-gear under heavy throttle is pretty clunky when it occurs. Usually that's a sign that you've got too heavy a load or far too much power. I am going with the theory that it's far too much power. When the truck is at freeway speeds and with the torque-converter locking clutch engaged, opening up the throttle to about half-way results in very nice acceleration, considering that after all I am driving a truck.

[Note: As of November 2007 I did get the transmission rebuilt at BCC Transmission on Gude Drive in Rockville, MD. This cost me about $1500 but so far it is all good... other than the fact that the trans is probably underrated for the output of the engine.]

Recently, I took a job hauling which so loaded my pickup bed that the vehicle was audibly creaking, which is a first for me. Yet with the 3.4L "crate" engine and the new Weber 38 DGES carb, I had no problem moving that load down the road, and had to be fairly cautious about giving power to first gear after the vehicle accelerated rapidly enough to somewhat shift the load.

If you are looking for a new carburetor to replace your crappy old VaraJet, and you want something that will let your engine breathe in huge amounts of air-fuel mixture at screaming RPM revs, you might find the Weber 38 DGES to be a bit small and constrictive at the high end with the rated flow of 330 cfm (cubic feet per minute). The original VaraJets, remember, have flow ratings of 375-390 cfm or so. Consider one of the larger Webers, or perhaps something along the line of a Holley 500 2-bbl. But keep in mind that these are probably more trouble to install than is the Weber K490 Jeep "outlaw performance" kit.

If you are looking for a new carburetor to replace your crappy old VaraJet, and you want something that will give you considerable increase in low-RPM torque and will definitely improve a light truck's load hauling capability, the Weber K490 kit should be at the top of your short list.

April 30, 2007, by Thomas Hardman

ADDENDA

2007 May 11 -- Emissions

A Maryland State Emissions check indicated that the fuel mixture was set somewhere around 1.5 times the setting that would allow me to pass the check. As the Comanche has been getting about 10 miles/gallon, this makes sense. A re-adjustment of the mixture went as follows:

Back the idle-speed screw out from the throttle plate cams. Turn the two idle-mixture screws in until lightly seated. Turn out one turn exactly. Turn inwards until the engine roughness starts to increase significantly, and then back out again until the roughness disappears. This turned out to be 7/8ths turns out from seated.

A check of vacuum hoses and vapor/emissions lines showed a lot of problems. For example, if you want the distributor vacuum advance to work, you need to give it a source of vacuum. This turned out to not be the extant situation. Fortunately for me, I had time, a flashlight, tools, and the original factory hose diagram.

The original VaraJet has many vacuum ports of various sizes. Most of these don't exist on the Weber 38 DGES carburetor. To be extremely simplistic about it, the Weber 38 DGES has a front port for vacuum which is suitable for attachment to the distributor vacuum advance. The Weber 38 DGES also has a port central to the intake throats, which is connected to the PCV system. It also has a carburetor fuel bowl vent fitting, but that is not a source of vacuum, it needs to be hooked to a source of vacuum.

The main source of vacuum has to be the main manifold vacuum port, in this case located just to the rear of the carburetor on the passenger side. Aside from the small front vacuum port on front of the carburetor which is to be attached to the distributor vacuum advance, this manifold vacuum port has to supply vacuum to the entire emissions/vapor and vacuum regulation system.

The idiots who originally installed the 3.4L engine (replacing the dead 2.8L stock engine) managed to incorrectly attach a lot of hoses, and also left a few hoses unattached. With enough spare vacuum hose, and a lot of "tee" fittings, it was possible to seal all vacuum leaks. A nice long drive showed much improvement in drivability, especially in terms of acceleration with wide open throttle. However, it seems that sealing the vacuum leaks has resulted in the mixture being too rich. I will have to tune that tomorrow.

2007 May 19 -- Re-Jetting

After considerable research on the InterNet, I found a most excellent page dealing with Weber Carburetor jets. I have shamelessly stolen a spec sheet mounted originally at "Carbs Unlimited" and here reproduce their table of "stock specs" for the Weber 38 DGAS / 38 DGES 2-bbl downdraft synchronous carburetors:

Original Specs 38 DGAS/ES
Main Jets	145	Emulsion Tubes	F50
Air Corrector Jets	185	Venturis	27mm
Idle Jets	045	Aux Venturis	4.00mm
Pump Jet	070	Needle Valve	2.50mm
Pump Exhaust Jet	030

I decided to place an order for replacement jets. As I was informed that the 38 DGES ships with idle jets with 0.045mm, or "45s", I ordered a pair of "40s" and a pair of "50s". These were ordered from europarts.com and arrived by US Priority Mail.

Removing the idle mixture jets isn't hard; they're located about halfway up the main body, more or less above the idle mixture adjusting screws. The one on the "front" was a large brass cover screw, which unscrews and is pulled out with a smallish brass or bronze fitting coming along with it. Getting to the "rear" one was a bit more difficult, as it was both in a hard-to-reach place as well as being set into a recess. Unscrewing it loosened it, but there was no easy way to get a grip on it without removing the carburetor to shake it loose. It turns out that if you use a rather small screwdriver with a short shaft but a wide standard blade, you can sort of wedge the tip of the screwdriver into the screw slot, pull the head of the screwdriver to the side a fair amount perpendicular to the width of the blade tip, and that will wedge the screwdriver blade into the slot and you can slide out the idle jet. Just be really careful and don't drop it or you may have to remove the carb (and maybe other things as well) anyway.

For some reason, the "front" idle jet turned out to be a lot larger than the "rear" idle jet. Looked at under a magnifying glass, the front one turned out to be stamped "55", and the rear one appears to be stamped "C". I have no idea what happened or how this was shipped this way, but it explains the rough running and the very rich mixture in the idle circuit.

Installing the two "40s", which also is fairly easy, I was able to tune the carb according to Weber's "best lean idle" instructions. However, the best idle comes at almost 2-1/2 turns out from idle-mixture adjust screw seating. That's not good, it indicates that the jets are too small. I removed the "40s" and tried installing the "50s". That could not be made to work. Europarts.com shipped two different-length brass fittings labelled "50". The shorter of the two could have been installed, it fit, but the second was almost twice as long and could not be made to fit. I wound up re-installing the "40s".

I also have two "140" Main Jets on order from CarbsOnly (BFIC in California). The stock main jets are supposed to be "145s".

Another place with a good selection of jets for the 38 DGAS/DGES is online at Pierce Manifolds.

Probably I will have to go ahead and order the full Rejetting Kit, just in order to feel certain that I have replacement parts. I have a suspicion that I might have accidentally been shipped a heavily modified kit meant for some other customer. Otherwise, I have to worry about quality control and competence in assembly back at the Weber assembly plant. Either way, I will have to tear the thing down and make sure that all of the various jets, etc., are all matching and in appropriate sizes.

Also there's a problem which seems to be related to the fuel system. On sustained acceleration, it often seems that I have sucked all of the fuel out of the carb faster than the fuel pump could replace it. For example, I wind out first gear and right about the time I need to upshift, the shift happens but the engine nearly stalls, sort of coughs a few times and then catches again in the next gear. It's very disconcerting and could be dangerous in traffic. It also doesn't seem to be doing my transmission any good.

2007 May 23 -- Re-Jetting Part II

Remember that complaint about the over-large "50" idle jet? I inserted it into the return line to the gas tank from the fuel flow splitter I had installed to allow recirculation. It's a bit small for the hose so it sort of floats in the hose. But it's too large to fit entirely into the return-flow hard line back to the gas tank. At idle conditions, it seems to float and allow fuel flow to keep cool fuel flowing through the engine compartment, instead of restricting it and letting the fuel get heated up to vapor-lock temperatures. But when I put my foot on the gas, it flows back up to the hard line and then lodges there, restricting return flow to the gas tank to about 1/4th of what can be used by the carb. This means I have an end to my "overcapacity return flow" problem. My thanks for this tip to Rockville Speed and Custom, "your in-stock speed shop".

Here's a view from the front of the vehicle looking at the top of the Weber 38 DGES. Today we'll be taking off the top, in order to replace the main jets. The "140s" came in the mail today.

Below, a very small "C" clip holding the choke actuator linkage to the choke assembly. It's hard to get off, and you are about guaranteed to lose it. Have a replacement ready. It has to be removed to get the top assembly off of the main carb body. Well, you could possibly take off the whole choke assembly and remove that along with the top plate, but my setup precludes that, the radiator top output hose for the cooling system is in the way.

There are six screws to remove, and you have to remove the "C" clip retaining clip to get the top plate assembly off. You will also have to remove the fuel-bowl vent hose and the fuel input line.

Below, here's a view -- from the bottom -- of the top plate assembly. This shows the floats, etc.

Below, a view of the inside of the main carburetor body. Sorry about the bad focus. You can see the two venturis in the carb throats. I'm not sure about the central brass fitting right below them, but the next two lower brass fittings are the "air corrector" pieces, in this case they are "180s". Below them, floating in the fuel of the fuel bowl (siphon this out carefully and NO SMOKING, okay?), are the two main jet fittings. They are removed with a small blade straight screwdriver. Today they are being replaced with "140s". Screw the old ones out, screw the new ones in. Don't overtighten them, basically when the screwdriver stops turning, they're in place. Replace the top, tighten the six screws in rotating order (cross tighten, like you'd do for a five-lug wheel), and reconnect everything. Check for leaks, and then see how it runs.

After replacing the idle jets and main jets, respectively with "40s" and "140s", the truck runs much better. But so far, the mileage is not improved a lot, I will try to add more information about tuning the carb for acceptable emissions and better mileage. I will try to be scientific about it, where possible.

A note: I also recently added a tachometer. I have found that if you are pretty careful with the gas, you can get every speed from 0 to 55 without going much above 2200 RPM. With this Weber, that means that you can go almost any speed relying mostly on the idle jets. Somewhere in the vicinity of 2000 RPM is the "sweet spot". For this Comanche, with the 904 TorqueFlite transmission, you have to go to about 2000 or 2100 RPM to reach the speed where 3rd gear can lock the torque-converter. Other than that, you can watch the tach and go almost any speed by running the engine at no more than 1500-1800 RPM, and be pretty efficient in terms of MPG. With this particular trans and torque-converter setup, that means that you will be accelerating pretty slowly and possibly impeding the reasonable flow of traffic. But if you can get the flow of synchronized traffic signals to work with you, the increased fuel economy is probably worth it. Other than that, if you want fairly brisk acceleration, running through the gears at about 1800-2200 RPM will probably move you right along, if you want to set your shifts (or shift manually) to run as high as 2500 before shifting, you will probably move pretty quickly. Run up to 3000 RPM and you are starting to get into the main jet operating range. Run up to about 3500 and you are entirely in the main jet operating range. In this Comanche with this gearing, you are winding out 1st gear at about 25 or so, winding up 2nd gear at about 55 or so, and in 3rd gear with the torque-converter locked, you're doing about 70 or so. If you want to start off in 1st gear and just hold RPMs at 3000-3500, you will be moving right along and getting down the road. If you hold the RPMs at 1500-2200, you will probably be leading traffic, but not by much. If you hold the RPMs at 1500 or so, you will probably get up to 40 MPH in a nice efficient lowrider cruising mode.

My only complaint right now is that I am afraid to do a wide-open-throttle since I could break my cheap superglue repair job on the kickdown cable. I have a replacement highly adjustable cable from Lokar on order, and will document that as soon as it arrives in the mail.

2007 June (early)

The cables came in from Lokar, and they're very nice indeed. However, Jeep used a very un-MOPAR means of attaching the trans cable so the Lokar cable doesn't work. It's supposed to come around the back of the trans, be attached there, and extend forward to a little arm that gets pulled back when you press the accelerator. The Jeep doesn't have that. It's got a sort of C-shaped clip that pulls forward when you step on the gas. I wound up using the little clip from Lokar's cable set which attaches to the post on the Weber's hardware, and also used Lokar's very nicely adjustable clamp sets. It was also necessarry to umount the original adjusting system from its bracket and adjust it to the other extreme of the factory settings, in order to get enough spare cable to use the Lokar hardware. The end result is very adjustible and very durable.

2007 September 11 -- Proper Timing Fixes Much

Here's a diagram of the torque-horsepower-RPM curve:

I finally broke down and bought my first timing light. It's a simple induction rig that came with a fairly comprehensive set of instructions. It turns out that the timing was set for 6 degrees "before top dead center".

According to the specs for the original2.8L Chevy engine in this jeep, it's supposed to be set to 12 degrees before top dead center ("BDC" or "BTDC"), plus or minus 2 degrees. Setting it for 12 exactly, running warm but not as hot as it would be after fairly strong driving, it runs really quite well. After re-adjusting the idle jets, it's pretty peppy. It also vibrates a lot less and runs more smoothly, especially at lower RPMs.

However, after taking the truck out and running it up and down the highway for a half-hour, it's back to running a little rough in gear idling at stop lights. I'll have to take the timing light out with me the next time I go for a spin, and see if perhaps the timing somehow has drifted downwards, perhaps due to some sort of thermal flexing or warping.

It may very well be that 12 degrees BTDC is the least setting, and perhaps it will run better at something like 13 or 14 degrees BTDC.

I should note that because I didn't have the proper vacuum equipment, I wasn't able to test the vacuum advance. Since it's probably original equipment with 175,000 and more miles on it, it's probably overdue for replacement. While I am at it, I think I will also replace the ignition control module, which is also probably pretty elderly. A nice vacuum gauge is on my tools wish-list as well.

Here is a good reference on how works a vacuum advance and mechanical advance.

2008 September 15 -- One Year After

Okay, folks: A couple of oil changes later, combined with assorted hammer banging and general turning of wrenches, and "it's all good". Except it's not actually "all good".

This is mostly due to the fact that the Weber is a race/high-performance carb attached to an engine that is mostly the stock power supply for minivans and off-prime low-rent Camaros. It's not a bad engine but it redlines at about 5000 RPM. It's meant to yank serious load down the road at anything from about 1500 to 2200 RPM. At this, it excels... as an engine. The Weber carb, however, is a race and perfomance carburetor that really wants to play nice at an airflow that you will see from this engine only above about 3000 RPM. For this Jeep Comanche pickup with the A-904 transmission, that means that you don't start to see real -- by which I mean REAL -- performance until you are going right about 60 MPH.

After the transmission rebuild -- for which I paid quite a lot -- I get extreme performance from the transmission even with the stock shift package. If you kick down to second gear, you get second gear and you get it with the torque converter locked. It's the same if you kick down to first gear. The interesting part is when you run high RPM up to maybe 50 MPH (about 2300 RPM) and let the trans fall back to 3rd gear with the torque converter locking anyplace above about 45 MPH (2150 RPM). At this point, about 1/3rd throttle preserves manifold vacuum and spark advance, and you get right on down the road. But this is about where you start to realize what you are running. Getting up from 45 MPH to 60 MPH for a freeway on-ramp merge is not a problem. Blink and you are there. Just use as wide a throttle as will not kick down the trans to 2nd gear, and you will "get on up" in a way that will amaze. It's all about good gears and low-RPM torque.

Running 55 MPH means you are running about 2600 RPM. But the Weber carb as presently equipped really wants to run above 3000 RPM. Fortunately, the interstate highway from here to Annapolis lets me run 65 MPH, and that means I am right at the bottom of the extreme race and efficiency performance curve. What this means in practical terms is that if I open the Weber all of the way, I get nothing but raw power and jump thrust. The only way I can explain it is to say that the GM 3.4L "Crate" engine tuned for low-RPM launch will combine with the mid-level flow of the Weber race carb to put a fine polish right at the intersection of the torque and horsepower curves of the engine. And all of this is anywhere between 55 and 85 MPH. I haven't yet had the chance to run a legal redline test to discover where the torque and horsepower curve fall to earth around 5000-5500 RPM, but I expect it's somewhere around 100 MPH or so, definitely at the limits of the vehicle type in terms of staying on the road. This isn't a fast little truck, but in terms of punching it without dropping down a gear, and getting "jump up", oh yes. It can definitely do that, anywhere close to legal or sane freeway speeds. The fun part of this is that at speeds above 55 MPH or so, it's all throttle response from the carb, transmission kickdown is pointless, a waste, and something one just does not do. It's so much better if you just ease it down and watch the world move past lots faster, sooner than you expected.

Driving around town, I am lucky to get 13 MPG. Once running up at the legal 65 MPH limit at about 3000 RPM, I get about 20 MPG, and that's when I'm playing with the pure pleasure of hot throttle response and "jump factor" of the magnitude usually only enjoyed by the Highway Patrol running in this-year's unmarked pursuit hot-rods.

But, due to the high price of gasoline, I don't do highway trips, and don't play with the throttle much. Rather, I use the low-RPM/high-torque aspects of the engine and barely touch the gas. I'm trying to be a "hypermiler" in a heavy old light truck designed for hauling loads. As I develop statistics on how to do this -- mostly with re-jetting and vacuum-advance mods -- I will try to keep folks posted.