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Old 03-18-2021, 10:09 AM   #11 (permalink)
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Could you ever get a perfect gear ratio? Everything I've ever seen is a compromised compromise

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Old 03-18-2021, 10:32 AM   #12 (permalink)
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Originally Posted by oil pan 4 View Post
With the perfect, ideal gear ratio only expect about +2 maybe +3 mpg highway.
I am very aware of the fine line between the correct torque range and lugging an engine. These are my starting point for testing.

This is the best I can do and plan with the vans current stock 3.42 rear end gears. There is the possibility that my engine may make great torque at 1000RPMs, but I am not counting on it. The ideal is to gear everything at the engines torque peak, under or over by much and she will start drinking.

SO you cannot gear a stock engine with a torque peak of 2800/3000 to pull at 1500RPMs and get good MPG. So I am building an engine that peak at 2000 RPM and gear close to that.

Once it is built I will do as careful testing at all available speeds, RPMs with all the gears I have to test. THEN as I have a howling rear end will then rebuild it with what will seem to be the best gear ratio, with a range of 2.73 to 4.11 I can choose a gear that may be ideal.

So I start with a best build I can do, a 383, 9.5 compression, everything built for MPG, ceramic coated heads and pistons, telfon coated pistons skirts gapless rings, Rhoads Roller lifters giving me a variable cam, a cam selected to allow a torque peak at 2000 or less, but thanks to the lifters will then turn into a power engine at 2500 to its max RPMS of 5000RPMs, fed by a 1987 Chevy TPI intake system.

Then to add to all of that I have a chip for the PCM to engage Lean Burn Mode which in the 80s Camaros allow them to go from 20/25 TO 30/35MPG.

To that I will be adding water injection, and extra EGR.

Lastly my van is very great in wind.

This is what I have said concerning high profile vans with high roof and how they are blow around by wind and big rigs:

I bought my 93 Star Craft Custom Van after having stock Chevy vans for decades I was concerned that with the raised roof and side ground effects would make winds worst for driving.

I drove a 74 Chevy van full time during the 80s and crossed the US on many times, in the 90s and into the 2000s it was then a 78 van. Again we did a lot of road trips all over.

I was very used to fighting for control with cross winds and when passing or being passed by BIG RIGS. The bow wake of air would buffer and push my vans all over the road; I am sure near every Van owner knows what I am talking about.

My first road trip showed me that was NOT a problem. Cruising at 75 MPH I was over taking a Big Rig and I braced for the fight as I over took the cab…and..and WTH no fight, I breezed by this big truck….

Must have been a trick cross wind that stopped the bow wake of the big rig, BUT it happened again and again, almost no effects of passing trucks, and even when I was over took by even faster big rigs.

OMG The stream lining ground effects of the Star Craft panels which I loved for their LOOKS really works. I have had the van for 15 years and LOVE this effect.

I believe these ground effects keep air from under the van and I believe this nearly stops the effects of bow wakes and losers the effects of cross wind on my G20 van.

Here are a few suppliers of like ground effects systems. Note they need to be streamlining, running boards seem to do not work.

Starcraft is no longer in business parts can be found here:

Starcraft Conversions - Unique Concepts



My Van


The only thing that I cannot remember is was my first road trip made in the 93 was done on the Stock wheels and tires OR had I already swapped to the 18 inch wheels with load and speed rated low profile tires. The over height IS the same as the stock wheels and tires just more wheel and less tire.

I have proven over and over again and again running these types of wheels and tires improve handling greatly. At least with the softer wheels and TIREs on a G20, the one ton 8 bolt wheels and HEAVY duty tires run of those trucks feel as hard as does my 18s.

My latest proof is my 02 Ford Explorer which was so badly handling that even a land change felt like she might tip over, it had FAT stock balloon tires I was about to sell her off when I bought 20 Wheels with lower profile tires and again the over height IS the same as the stock wheels and tires just more wheel and less tire.

The floppy Explorer NOW handles like a good big car, not a race car but MUCH better.

And PLUS with the 18 inch wheels and tires on my 93 Van is I had a blowout at 80MPH with the front right side…and unlike a common blow out there was NO fight to maintain control, in fact I only knew I had a problem by how she started pulling to the right, once I crossed 4 lanes of highway slowing down was a little surprised to find a blowout….

I have not driven a new custom van with the same look like the newer Express vans, There seems to be only one company doing these conversions, Explorer, It looks like Explorer Conversions run with greater ground clearance and I think that defeats the ground effects.

Lastly there are two Express vans documented to get 29/30MPG with stock bodies…so it is NOT the box causing crappy MPG.

And there are a bunch of changes and improvements I have made as well.

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Old 03-18-2021, 10:49 AM   #13 (permalink)
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Originally Posted by Piotrsko View Post
Could you ever get a perfect gear ratio? Everything I've ever seen is a compromised compromise
Yes, you choose which you want power OR MPG.

But I will now have 8 gears, with the second OD it can be engaged in all four gears, AND thanks to adding a .80 over drive TO a .75 4th gear is comes out to a .56 into my rear end gear, SO I can have a very great compromise.

A second over drive is the ONLY way to reach a .56 ratio.

And yes I will need to control it manually, which is a little more complex that a 8L80E full automatic.

But again there is NO .56 over drive:

4L60 4L80 6l80 8L80 Gears
1St 2nd 3rd 4th 5th 6th 7th 8th
4L60 3.06 1.63 1.00 .70
4L80 2.48 1.48 1.00 .75
6L80 4.03 2.36 1.53 1.15 .85 .67
8L80 4.56 2.97 2.08 1.69 1.27 1.00 .85 .65

Yes a .65 is very close, but to switch to a 8L80 will cost me at best $2000.00 to $3000.00, this set up is only costing $1000.00

Possible stock GM Gear ratios: 2.73 In aftermarket only

2:73 3.08 3.23 3.42 3.73 3.90 4.11

RPMS and MPH: calcuator;


So as in my 93 running a stock:

So a 4L60 at 70MPH with a 3.42 would be running 2100 RPMs

So a 4L80 at 70MPH with a 3.42 would be running 2065 RPMs

So a 6L60 at 70MPH with a 3.42 would be running 1690RPMs

So a 8L80 at 70MPH with a 3.42 would be running 1710RPMs

OMG I just figured out how great all this set up will be.

This combo of a 4L80E heavy duty transmission and the heavy duty US gear overdrive will mean I can TOW a trailer with this van with the front transmission in 3rd and the US Gear in overdrive.

So running in 3rd and US Gear OD I would be able to run at 70MPH and be pulling 2310 RPMs, not super MPG but still low and right at what should be near my torque peak. This is great.

My old layout of the weak 4L60e and an old Borg Warner OD was too weak to consider towing anything, I figured it was barely strong enough to handle the van.

If I was richer I would go with the 8L80...

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Old 03-18-2021, 10:51 AM   #14 (permalink)
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I had lean burn in my 5 speed, 3.42 rear end, 2.8L v6 camaro and the best it ever did was 30mpg on the highway.
Water injection on gasoline engines with a normal compression ratio doesn't seem to do anything.
1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost.
1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end.
2011 leaf SL, white, portable 240v CHAdeMO, trailer hitch, new batt as of 2014.
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Old 03-18-2021, 11:04 AM   #15 (permalink)
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Originally Posted by oil pan 4 View Post
I had lean burn in my 5 speed, 3.42 rear end, 2.8L v6 camaro and the best it ever did was 30mpg on the highway.
Water injection on gasoline engines with a normal compression ratio doesn't seem to do anything.
Yes some got 35MPG.

Problem is your stock engine has a torque peak at 2800RPMs, so if you drop much below it the MPGs will also drop.

I am building an engine that will peak at 2000 so should get great MPG at 1500+ RPMs.

So I needed a replacement engine, and had already started on it in 2005, so most of the costs were already done. but I replaced the van it was meant for...

And I want to test my ideas on how to make a van get20 to 30MPG...remember I started this project back in 2000.

IF I was rich I would just buy a 2017+ Express van with anew 29/30MPG setup, but I do not have 30K to spend, so on with my build.

So I will be happy with 20MPG.

Damn my 03 Crown Vic P71 (ex cop car) just made a run of 416 miles and got 18/22MPG on the highway...

My 2000 Mercury grans Marques was able to get 24/26 MPG highway.

So if I can match that in a full size van I am good.


PS water injection may add a little and EGR and water will lower its NOX output keeping it clean.
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Old 03-18-2021, 11:09 AM   #16 (permalink)
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How do you determine exactly what the peak engine performance is? Will you dyno it or is this simulator/data crunching?
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Old 03-18-2021, 11:53 AM   #17 (permalink)
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Data crunching: But will a lot of data.

There are very few dynos that will read below 2500, most are built for hot rodders.

I did find a dyno test of the TPI systems on a rare dyno that did indeed read at 2000, and they made a fuss over getting to use such a engine dyno.

I also had to go with factory ratings...

Reports like:

The 400 was never built as a performance engine. It was a work engine used in heavy trucks, bus, vans, dump trucks etc.

HP is low stock in the 150-185 HP but had a lot of torque.

1976 400 R4carb, 8.5:1 compression, 175HP @ 3600 rpm, 305 lbs ft torque @ 2000
The corvette 350 for that year
1976 350 R4carb, 9:1 compression, 210HP @ 5200 , 255 ft lbs @ 3600
'76 350 for like the camaro
1976 350 R4carb, 8.5:1 compression, 185HP @ 4000 , 270 ft lbs @ 2400

Also the OLDS 403 with a torque peak of 2000 as well.

I then got the specs as best i could of these cams..the best i found was a 2200 RPM Chevy cam:

The choice of a Cam was become a nightmare obsession. The cam is THE MOST IMPORTANT part of a engine. The cam controls what kind of an engine you building. Cam grinders and makers’ 90% of the time give more power by shifting the power band up. So a mild stock engine can run from 1500 to 5000. Move that to 2000 and 5500 more power, move it to 2500 and 6500 MUCH more power.

BUT to get that power costs fuel, more is needed with each power shift.

To get better Miles per Gallon, the idea is to keep the low RPMs power band by not shifting the power curve upward, and setting the whole car/truck up to cruse near your engines torque peak.

I have been working on getting an engine set up to run at a torque peek of 2000RPMs. Sadly it seems this will limit other factors as passing and mountain climbing.

Here is what I think will give me the best set up:

I found this article: How to build a budget 383:

From https://itstillruns.com/build-chevy-...rque-7988109.…

I combined the notes to what I am doing.

A 383 alone is good for an instant 10 percent increase in horsepower and torque from idle to redline over the same engine as a 350.

“It Still Runs” said to use L31 GM Vortec cylinder heads. (I believed these are known as 193 swirl port heads) These first-generation Vortec heads flow about 239/147 cubic feet per minute of air at 0.50 inch lift, (which is about their max lift) which will support about 490 horsepower in completely stock form, and are a direct bolt-on for any small-block.

You can find L31 heads in 1996-1999 GM full-sized trucks, 93 Vans etc.

I mistakenly thought this was talking about the first swirl port heads known as 193, L05 heads. Flow rate for 193 iron LO5 head: 178 intake; 146 exh (Dyno Don) VS the L31 heads 239/147 Close!!

With these 64CC heads and my pistons I will have 9.3/9.5 Compression.

“It Still Runs” originally suggested: Using a stock 1988 to 1989 Corvette L98 camshaft designed for the tuned-port injected (TPI) 350. They say that this cam is actually far too tame for a 383, but installing a set of 1.7-to-one roller-tipped rocker arms will open the valves about 6.5 percent further. This will almost compensate for the 9.5 percent increase in engine displacement.

It gave me a base line.

Instead: I matched their specs to orcam@pacifier.com # 806 cam, nearly this same profile as called for with 1.7 Rockers BUT now using milder 1.6 Rockers:

The L98 specs: 207/213 @.050 114 .442/458 with 1.7 rockers

#806 cam’s Specs; 207/214 @.050 117 440/454 lift with 1.6 Rockers (milder rockers)

That WAS my plan until my latest findings:

When I was forced to remove all head bolts and add a sealer I also had to remove the roller rocker as well. Doing so made me see that their adjustment nuts were not using very much stud thread, only a hair over ¼ an inch. I contacted the manufactory about this and was informed that with a 3/8 stud I really should be at least 3/8 an inch of thread to hold.

I then discovered NO ONE Makes a full roller rocker for stock heads, that every build for a hot rodder set of heads with longer screw in studs. My heads are stock.

So I was then facing buying a set of stamped 1.6 rockers to correct this problem…

At this point I was also in deep talks with a number of people about this engine, and decided to reevaluate the rockers.

I dug out the cam specs for the cams: Cams are listed duration and lift Intake then Exhaust.
I will be running Rhoads V-Max roller lifters, and with Rhoads Lifters running at 10% reduction the cam will be listed as well.

WAS My Power Cam: 231/206 424/452 With 1.6 Rockers
With Rhoads Lifers: Less 10% + 180/192 115 .396/408

Now Power cam: 206/ 213 143/428 With 1.5 Rockers
With Rhoads Lifers: Less 10% 185.4/191.7 .371.7/385.2

Low RPM 350 Cam: 179.5/192.2 .350/381
So NOW I am very close to the low RPM cam I modeled this from.

So at 1500 to 2500 My new cam’s intake valve will be opened a just little longer from 179 to 185 and open slightly more from .350 to .371 and the Exhaust Valve will be 192.2 to 191.7 and opened a little more at .381 to .385.2.

This should give me the MAX Torque at 1500 to 2500 RPMs which should product enough power to easily pull the van at 75MPH.

Whereas at 2500 RPMs the Rhoads Lifters will start to pump up and cut in my hotter part of the cams profile so instead of a drop in power my engine should just keep on making more torque and HP all the way to 4500 RPMs.

This will give me a variable cam, mild at low RPMS and HOT at higher RPMs.

I think such a set up should lower the torque peak near 2000RPMs at low RPMs and open up the cam around 2500 RPMs which will give me a big power boost.

“It Still Runs” said an engine built to this spec (minus the Rhoads Lifters) should produce about 300 to 340 horsepower at a usable 4,800 rpm and an Earth-moving 425 to 450 ft-lb of torque at around 3,000 rpm. As I am NOT running the modified heads they called for I figure to get a little less.

As I am not doing the porting work called for, because everything I read about ports has said for MPG leave the intake stock, porting is needed only for MAX HP, so I figure a small lost say 10% BUT I WILL be running a TPI system next year that is reported to add 20/30% more torque, HP and MPG…

Due to so many delays getting my machine work done I will be lucky to do a straight engine swap before the AZ Summer puts a stop to any work.

Now I am thinking I really lucked out with these SLP runners and now will be feeding and replacing that lost power right at the point the cam comes alive…

They say that this fairly mild engine's fat power-band, efficient combustion, glass-smooth idle make it a perfect fit for a daily-driven car or truck.

So this is my calculations.


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Old 03-18-2021, 12:29 PM   #18 (permalink)
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The question has come up: WHY?? Why not just buy a new van??

So here is my bottom line.

I could buy a new Express van that can get 30MPG at say 50 to 70K. How many miles will I need to drive it to cover the major cost VS my old van’s 14 to 20MPG?? I kand think the new van will never last long enough to even get close.

AND I can expect very costly repair costs as well. My front wheel bearings cost $50.00 VS 150.00 for hubs, my 4l80 can be rebuilt for $200.00 to 1000.00 VS $3k for the newer transmissions, my cast iron engine with cast iron heads are able to hand an overheating problem far better that most aluminum new engines, a Northstar over heats and it is junk…Worst comes to worst I can swap in a good used 350 FAR cheaper than a2.8 Turbo diesel of small V6.

AND from a lot of reports these custom vans have crappy workmanship. LOTS of complaints.

And I would be wasting a lot of value tearing out much of the interior to fix it how I want it.

So I paid $3200.00 about 15 years ago for my custom Van. During that time I have only needed a few repairs that I was able to do almost all myself.

PLUS parts are a LOT cheaper for these old cars and vans.

And I took my time building my new engine..and drive line, all rebuilt as best as I can get it done, so I figure I will be adding about $7000.00 to this van, a van I have driven about 50K already.

So at the end I will have invested $12200.00 plus say another $1 to 2K over the years with other improvements and my labor.

So again I will have a great van, made the way I want it, handles great, is not blow off the road by wind and big rigs, getting good MPG with a completely rebuilt drive line which I can repair at greatly lower cost of any newer van.

I call it a WIN-WIN-WIN-WIN!!!
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Old 03-18-2021, 05:42 PM   #19 (permalink)
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My question is why not post a picture here, instead of linking some other website?

I appreciate the aerodynamics part (I just skimmed the engine details).

And I want to test my ideas on how to make a van get20 to 30MPG...remember I started this project back in 2000.
In the 1990s I was driving a 1961 VW panel van. You might not consider it full-sized but it was uprated from 1/2 ton to 3/4 tons axles with sway bar and gas pressurized shocks in front and air shocks in back (decambered), big 'n littles, etc. With a fresh engine rebuild I drove exactly sixty miles and refilled exactly 2 gallons. It never went 55 again.

Here's the aero kit I designed (never built). A plywood front bumper and side skirts.

The front bumper would shield a front mounted spare and the side skirts splay out from inside the front tires to outside on the rears.

I went into a restoration and got in over my head.
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Face the danger and row away from it.
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Old 03-18-2021, 06:34 PM   #20 (permalink)
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So what engine did it have??

And by it never went 55 again I take it you drove faster...if my memory is right those VW Bus could hardly get up to 75MPH...


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