My understanding the Tuned part of the TPI is centered at around 3000RPMs, is there any way to lower the tune port power curve??

Rich

 

The overall length of the runner from the plenum to the backside of the intake valve is the biggest contributor to the powerband. The stock TPI system is tuned for the 4th wave about 2900rpm and the 3rd wave about 3800rpm. Camshaft intake duration affect this rpm a little bit, but it’s pretty close to that. There is a 5th wave around 2500 and higher waves at lower rpm but they are pretty weak after the 4th wave.

The only real way to lower the tuned rpm is to lengthen the runners. That’s not an easy thing to do.

The tuned rpm is already pretty low. Why do you want to go lower?

 

I would agree there really isnt a need to go lower. A tight lsa cam with more aggressive lobes than stock while keepig duration low may help.

Tpi is very good in the 3000-3500 range in torque. But even at 2500 its still pretty strong. Most cars shouldnt be wot below this rpm imo. 2800-3000 stall speeds on converters complement these systems well.

More lower end torque off idle may be found with swirl port style heads and tbi systems. I know they are low rpm deals but not sure if they do any better in peak numbers.

Much longer runners may do lower but it isnt ideal for packaging.

 

Next to a custom grind cam the best thing that one can do is run the GM 395 marine cam and TBI heads. Lots of low-end torque with that cam and TBI heads. Dual plane intake with TBI will make more off-idle torque than the TPI.

 

Well here is what I am trying to, and what I think I will get:

In Car Craft’s May 1989 issue in their article TPI Shown Down: they tested a 1998 Corvette L96 with its aluminum heads, stock but for Edelbrock’s 6873 IROC Tubular Exhaust system running through a stock 88 Cat for the testing. This made 253HP 4500RPMs and 328 lbs-ft at 3000 to 3500 RPMs.

The tested on Edelbrock’s Superflow 901 Dyno, which was able to pull numbers every 5 seconds and at each 500RPMs from 2000 to 5000.

So this base line engine did the following:

Torque:

RPMs torque
2000 296
2500 313
3000 328
3500 328
4000 316

That was only a gain of 32 Ft-Lbs from 2000 to 3000, the torque peek.

The stock specs for that car engine was:

Horsepower 245 net @ 4300 RPM
Torque 340 lb. – ft. @ 3200 RPM

My stock Van G20 350 made:

Power 188 hp @ 3800 rpm.
Torque 300.19 lb.-ft. @ 2400 rpm.

A stock 400 R4carb, 8.5:1 compression, 175HP @ 3600 rpm, 305 lbs ft torque @ 2000

Torque net: 295 ft-lb @ apox 1800/1900 holds until 2300

I will be running a 383, 193 swill port heads, and a roller cam rated for 2200 RPM torque peek, which I plan on advancing 4 degrees, which should shift the power curve to 2000 RPMc.

The cam specs of 1990–1992: Cadillac Brougham with 5.7 litres (350 cu in) L05/LLO FI V8,

Stock specs on a 1977-79 OLDS 403 are: 185hp@3600 RPM, 320ft/lbs torque @2200 RPM
Horsepower net: 175/185 hp (SAE net)

To that I am adding a 383 and a tuned port system which is said to add 30% more Torque, HP and MPG to a stock engine.

So I could see 354 Ft-lb for a 350, how much more I will get with the 383 is not known but I bet it will be a little more. I found this: all other stuff left the same the difference between a 350 to a 383 a rough guesstimate is 35hp, 40 lb/ft torque.

So based on that I might see from say 320 to 394 ft-lb @ 2000 RPMs.

But if I could lower the TPI torque peek I thought I would look into.

All of this is for:A low rpm 383. My plan is for this motor to spend most of its life running at 1700 RPMs and operate from 1500 to 4000. Everyone builds a Hot Rod version.

I am much more interested in LOW RPM Torque than house power.

I have read in a number of books that for best highway performance and mileage you want everything geared to be running at as near the torque peek and your cruising speed, + or – 10 to 20%. So if my engine’s peek is 2000 RPMS I want my cruse speed to be within 200 to 400 of that RPM which on the low end would be from 1600 to 1800 and on the high end be 2200 to 2400. Every V8 I have tested gets it best MPG running under 2000 RPMs.

The combo I am doing is: a 400 crank machined for a 350. Stock 400 rods so I can keep my KB “D” shaped pistons. I am aware of the side loading on the bore, so I am having the skirts Teflon coated and the crowns ceramic coated for lean cruse as I do not plan on running over 5000 max, this is not a major problem.
I am feeding this with a 88 Corvette TPI controlled by my vans TBI PCM converted to run TPI. I plan on having the stock Highway Mode turned on until I can get a special tuning.

Feed back?

Rich

 

My Express van has consistently done pretty much just as well on fuel at 2,400-3,000 rpm as it did at 1,700-2,000 rpm. 4L60E and 3.42s with 29.5" tall tires to a 4L85E and 5.13s with 32" tall tires. I lost a little MPG (18 mpg from 19 mpg) on the 1-ton rear end swap because I gained about 400 lbs overall, heavier LT tires, and 4" overall height from the 1-ton suspension and running gear swap. Going from a 350 to a 383 did not change the fuel consumption although many swore it would murder my MPG. MPG pulling my travel trailer is better with the 383.

I lost MPG going from TBI to TPI on my old G20 van for what it is worth.

 

A 383 with tpi will def make more torque, and still have alot at 2000-2500 rpm

 

A 383 with TPI, swirl port heads and the right cam will be a torque monster.

 

I believe if your engine is not geared for near your torque Peek, it will not get good MPG.

I have read in a number of books that for best highway performance and mileage you want everything geared to be running at as near the torque peek and your cruising speed, + or – 10 to 20%.

That is perhaps why no gain.

 

From your lips to the engine gods ears...

 

I really think so too...

Rich

 

Swirl ports and TPI will put a strangle hold on a 383 fairly early in the powerband. Piston speed is higher than a 305 or 350. Should work well in the 2,400-4,000 rpm range though.

 

What peak? LOL...With the dual plane intake, good heads, aggressive roller cam and rhoads vmax lifters....Its pretty much a table top flat torque curve from 2,000 rpm to about 5,000.

 

I know my machine shop and others all said it will run out of breath at 4500.

[/QUOTE]What peak? LOL...With the dual plane intake, good heads, aggressive roller cam and rhoads vmax lifters....Its pretty much a table top flat torque curve from 2,000 rpm to about 5,000.[/QUOTE]

OMG Roller rhoads vmax lifters....OK Now you have done it....

One: any noise??

Two, are you running fuel injection?

Three NOW I will have to give this a rethink.

Rich

 

Ok now I am considering a slightly hotter cam.

Here is a cam doctor reading of the cam I was going to use.

Can you suggest a couple of slightly stronger roller cams?

Thanks.

Rich


Cam Dr. reading of cad cam.

 

Have you thought about putting a Diesel engine in it? That'll get you a meaningful increase in fuel economy and all the tq and power will be right about where you claim you want it.

 

I thought about it. Diesels are heaver, nosier, smellier, VERY costly to repair, often diesel fuel costs more.
I also feel to convert a gasoline van TO run diesel is a little too much a problem. IF I wanted a diesel powered van I would have to buy a van with a diesel already in it.

Lastly there a few things I believe will give me better gas mileage I can do to a gasoline engine as I understand them.

I believe there are nothing I can do with a diesel, other than make MORE power and more power means more fuel usage.

Believe me I have heard this suggestion a lot.

Rich

 

A 305 and small turbo would do better here lol

A 383 will get you the torque but it will hurt mileage i think over smaller cubes. Bigger cams may make more peak and upper rpm powers but hurt bottom some if airflow isnt there. With a 383 i would think 216 deg and smaller on intake lobe. Tighter lsa. Maybe single pattern cam since you dont need high rpm exhaust evacuating. Interesting project

 

There are definitely things that you can do to a diesel to increase fuel mileage (especially on newer/electronic diesels), but the whole point is that you wouldn't need to; you'd already be getting mid to high 20's with smart driving, which you'll never get with a gas V8.

I don't foresee an ROI on your current goal.

 

well here is my latest plans, for what they are worth:

https://www.facebook.com/richardacoy...3627450&type=3

Rich

 

Nothing shows up for us non-FB participants. Can you copy/paste it?

 

It is fairly large, it took a good part of the day to put all of it together, there are some 66 pictures with pages of text and the there are pages of more text.

Here is a page:

Nearing the final build plans. The choice of a Cam has 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 each power shift.

To get better Miles per Gallon, the idea is to keep the low RPMs power 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 a 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-low-end-torque-7988109.…

I combined the notes to what I am doing.

A 383 is good for an instant 10 percent increase in horsepower and torque from idle to redline.

Use L31 GM Vortec cylinder heads. (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.

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

Original they suggested: Using a stock 1988 to 1989 Corvette L98 camshaft designed for the tuned-port injected (TPI) 350. 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.

They suggested two cams, this was the mild one. It gave me a base line.

Instead: I matched their specs to orcam@pacifier.com # 806 cam, nearly this same as called for with 1.7 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)

Then with a 4 degree cam advance to lower torque peak to 2800 RPMS

And with Rhoads Lifters running at 10% cam will be at:

180/192 114 .396/408 at low RPMs yet at 3000/ 3500 will be running the full cam.



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

An engine built to this spec (minus the Rhoads Lifters) should produce about 340 to 360 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 doing the porting work called for, I figure a small lost say 10% BUT I WILL be running a TPI system that is reported to add 20/30% more torque, HP and MPG…perhaps then 408HP and 510 Torque (20%)

This fairly mild engine's fat power-band, efficient combustion, glass-smooth idle and low coolant temperatures (due to the Vortec heads) make it a perfect fit for a daily-driven muscle-car or truck.

So there seems to only one big question, can they do the #806 with a 114 Lobe separation?? I believe so.

Any one see any problems??

 

Thanks for posting. I see two problems:
1. I don't believe anyone makes 1.7 rockers for a SBC.
2. I don't believe that Rhodes makes roller lifters. Maybe they do...I haven't paid attention to them in decades but last I knew, they were only flat tapped lifters.

Looking forward to the results.

.

 

No problem I will be using 1.6 rockers

And yes Rhoads has been very lacking in proper advertising their roller lifters, which the do indeed make.

Rich.

 

406 tpi super ram. Mild cam, probably 400 tq from idle to 4000 rpm, cubic inches, or more precisely a long stroke and decent compression are your friend when it comes to torque. Lingenfelter was building 383/406 super ram setups that made well over 400 tq off idle. By today's standards nothing exotic at all. And should be easily duplicated.

 

A bit like this one. It really wakes up at 2500rpm, I was off the chart on the VE table at 2500rpm... lol. It's very pleasant on the street, lots of low torque. Not a quarter mile car. Still good traction with drag radials and LCA brackets.

 

What books did you read this in? There is absolutely no way to get better economy spinning at 3000 RPM as opposed to 1500 if that is all that is needed. Higher RPMs increase your accessories load on the engine and consume more power... not to mention increased loss internally in the engine for moving the rotational mass more times per minute. This is why we have OD transmissions... it is a main component of why a 6-speed LT1 car gets better mileage than the same car with a 4L60E... or why the same car will get less economy going from a 2.73 rear gear to a 3.73 while keeping either transmission. You don't drive around under heavy load at WOT... if you were then yes, your statement would be correct, but not for cruise.

Where this gets confused is load. If you had an engine turning a generator. You will get the best return on output from fuel at or near torque peak. This is where the engine most efficiently moves air and fills the cylinders. What you will not get is the peak output from the generator - that would be a result of how fast you can spin it... or the HP your engine is putting into it. Over the course of time, you will get more output per unit of fuel at torque peak at the sacrifice of peak output from the generator. There is a conservation of energy in thermodynamics... you're not getting out more than you put in. If the generator was capable of producing 1KW of energy you would have to put about 1.5hp into it (not 100% efficient for all ratings so I am bumping them up a bit). So, your gas engine is rated at 1.5hp at 5000RPMs... if you need this to run everything plugged in, that is what you need (accelerating a car), if all you need is 0.5KW, you slow the engine down to about 3000RPMs as you only need about 0.7hp (car going up hill maintaining speed), but say your electrical needs are only about 5W (.010hp) max to charge your phone - that is only a minuscule amount of power (cruise)... you would slow the motor/generator down to produce only what you need. Why would you run it any higher? All you do is increase power consumed by parasitic loss and increased windage losses in relation to the power you actually need.

Just for some off the cuff numbers for demonstration we will say that the engine requires a 0.12hp to run itself at 5K, 0.10p at 3K, and 0.05hp at 1K. You need .010hp to produce the electrical flow you need so, you are just investing more fuel to move the engine faster, no additional output. The throttle at any given speed would only be open far enough to produce the combined power needed of the losses of the engine/generator plus the consumption of the phone to charge. Why invest in spinning the engine faster?

All that being said, I think you will be very happy with what you are building for the purpose you stated, but you would be fine with that torque monster to cruise down the highway at 1500RPMs.

 

It won't make enough power at 1,500 rpm to push his brick of a high top G20 van into the wind or push its 6,000 lbs of heft uphill. To run at that low of an RPM he needs a 496 big block or a 472/500 cubic inch cadillac preferably with a 4L80E behind it. A 500 cubic inch Cadillac was available with port fuel injection that can be controlled by a more modern ECM with a little rework. Factory 8.1 would also give him the grunt he wants. Small block is going to have to spin some though.

Turning more RPM with lower engine load you can spin the small block a little higher and run lean cruise giving you power when you need it and economy on flat road or downhill.

My 350 Vortec was happier running 2,500-3,000 rpm than it was at 1,800-2,200 rpm pulling around my low top Express van. From the factory with a 4L60E and 3.42 gears, Overdrive was worthless at 70 mph. Got the same MPG in 3rd as it did in 4th. ~3,000 rpm vs 2,000 rpm. My new 383 loves running 3,000 rpm, it cruises uphill over grades without ever dropping out of lean cruise. Last roadtrip running 75 mph netted 19 mpg.

 

...diesel. He needs a diesel. This entire conversation has "Diesel" all over it. A diesel will meet his goals.




I'm with Kyle. More RPM = more friction. A lot more, not a little. I can't believe your van gets better mpg at 3000 RPM than at 2000, given the same conditions.

 

Difference is it was always dropping into power enrichment, unlocking the converter and downshifting into 3rd with the stock gearing. Now it stays locked up in overdrive and in lean cruise. Air/fuel ratio stays at around 16.5-17:1 now. It was always dropping down to 12.0-12.5:1 before. It also cruises around 55° of timing now where it rarely ran more than 35° before. RPM does not dictate fuel efficiency. A lugged engine will always get worse MPG because the timing has to be retarded and the mixture richened up to keep you from detonating a piston or pounding the rod bearings flat.

My 8.1 99 Tahoe gets about 18 mpg highway turning 1,800 rpm @ 70. The 8.1 lives in lean cruise with all its low-end torque. Doesn't need a diesel, just needs a big block with a long arm and an intake with long runners. The longer the crank throw the better for making torque. Otherwise it has to be made up for with gear and rpm.

The best MPG he will ever see with the high top van would be with a naturally aspirated 6.2 or 6.5 diesel with the pencil injectors from a delivery van. Those had the high compression heads and got the best MPG. A 4BT might also do very well but the thing weighs what a big block weighs and his 4L60E wouldn't make it around the block behind one at stock power level.

My 06 Hemi Ram got better mileage with 4.56s than it did with 3.55s. You would think it would be the other way around but it wasn't. I once lost the OD clutches and the computer locked out 4th and 5th gear about 350 miles from home. I ran that truck in 3rd gear, OD off for the entire trip home at 75-80 mph. Around 3,500 rpm. The best that truck ever got was about 18 mpg. Running in 3rd it still managed 17. With modern synthetic oils friction is not nearly as killer as you are making it out to be.

Speaking from experience I had 3.08 gears in my 10 bolt and 3.07 gears in the 12 bolt I had in my old G20 van with a 700r4 and later 4L60E. I did not even let the thing shift into OD until 70+ mph. Fuel mileage was better delaying the upshift to that speed. ~4.10 gears would have delivered the best overall mileage in it as it would have had adequate power to cruise well without constantly unlocking the converter or downshifting or going out of lean cruise on every little hill. I could have shifted into OD alot earlier and had a little reserve power at the slower speed.

 

Cruise RPM now with the 5.13s, 4L85E and taller tires is actually about 2,700 rpm @ 70 and about 2,950 @ 75 mph. Just hums along.

 

BULL.

That is the most ludicrous of all your statements above. Synthetic oil is "so good" now, that we'get getting the same MPG at 3500 as 2000? Get real. THINK.

Since we're telling "vehicle stories", (and we're telling some tall tales, here!), I had a '96 Silverado x-cab/s-bed 4x4 Vortec 5.7, 5 speed for over 15 years. With the 5 speed, I can pick any gear and any throttle setting, any time, all the time. It got the best MPG in this highest gear (no surprise). I used to tow my boat from PC to Lake Powell for weekend trips....I've probably made 100's of trips down and back, towing my boat with that truck. I'd run it WOT in 5th gear for the BEST fuel economy (no surprise), and it would stay in 5th gear up hills, on flats, hours at a time. It even had synthetic oil in it. I wonder...do you think the synthetic's supposed resistance to friction would also help at 2000 RPM too? Hmmm....What ever meaningless difference there might be, I bet it would.

It's asinine to argue that an engine doesn't make substantially more friction at 3500 RPM than it does at 2000. Hook up your scan tool...look at your IPW at 2k in neutral. Bring it up to 3500....look again. The diff is 100% wasted energy, being converted into heat.

 

I lost 1 mpg increasing the cruise RPM of a modern Hemi engine from 2,200ish to 3,500 rpm. I would say that the friction difference was not as drastic as you state.

Will also tell you their is a huge difference between towing a little boat behind your little truck and towing a 6,000 lbs travel trailer that is 11' tall and 8' wide behind a fullsize Express van. Huge weight and frontal area difference. I would place a bet his high top G20 van has higher engine load because of the aerodynamics at highway speeds than your truck pulling your boat.

Best MPG will never be WOT in any gear. Power Entichment murders fuel economy. You will get much better fuel economy dropping down a gear and running around 3/4 throttle or less to maintain the same speed. I have done the same trip atleast 100x as well with my pontoon boat behind me. Up until I put gears in the van, it would only hold OD on the flats and running OD murdered the fuel mileage. Drop to 3rd and it would ALWAYS get better MPG. The only possible explination is that the stick shift tunes have a long PE delay at low rpm that prevents them from entering PE at near WOT. Never owned a stick shift Vortec truck to look at the tuning on. The Van, Tahoe, and Suburbans with automatics enter PE almost immediately over 80% throttle and dump fuel. Running 70 mph on the highway in OD with the stock tune it also loved to enter catalyst overheat protection mode and dump fuel. 10.5-11:1 on the wideband, downshift and it would cruise at 14.7:1 the whole trip. When I had a 60E I almost never used overdrive because frankly it sucked with the factory 3.42 gears.

 

Funny you say that bit with the scan tool. You are correct with an unloaded engine. However on the real world running 70 mph my MAP, MAF and IPW were all drastically lower running in 3rd gear than OD when I tested the results years ago of running in 3rd vs OD. Timing advance would sit much higher as well in 3rd. My stock Vortec did not have enough nuts to pull the Express van in Overdrive with 3.42 gears under about 80 mph.

The GM P30 and W chassis both use 5.38 gears with the 5.7 and 4L80E. Large frontal area and lots of weight to move. Even with that low of a gear they struggle in overdrive and rarely go into it.

 

When I went through Kentucky a few years ago I had the 4L85E and 3.73 rear. My 350 with the 395' cam, marine intake, thorley tri-ys, and a 91 octane tune making alot more torque than stock had a very hard time maintaining speed on hills locked up in OD. The 350 was giving it all it had to keep the empty van up to speed.

 

This endless debate is getting tiresome. Getting away from original question
Cheers
@racprops , 04-04-2020 10:22 PM
My understanding the Tuned part of the TPI is centered at around 3000RPMs, is there any way to lower the tune port power curve??

 

Its not even a debate it is simple fact. If you want good MPG out of a heavy vehicle with the aerodynamics of a brick it needs to be geared to to make adequate HP for the load it is pulling at highway speeds. 2,000 rpm @ 70 mph is too low for a small block to get good fuel mileage.

My Hemi Ram with a cam that had huge low-end torque gains got better MPG with 4.56s than it did with 3.55s.

This is climbing a similar grade in the 4.56 geared Ram. Ram did not even struggle to accelerate in high gear up the grade.

I am out anyway because some people need some physics lessons in this post. RPM alone does not dictate fuel mileage. Engine load plays a huge factor in it. Lugged engines get **** poor fuel mileage in my experience.

 

Isn't that roughly 4-5%... every 20 tanks you have burned an entire extra tank of fuel

Maybe not drastic, but significant. That would represent about 2.5 extra tanks for me a year at 17 gallons a tank, or 42.5 gallons per year. Using the base 20 I saw in my challenger with a Hemi that's 850 miles of loss per year.

Yup...
If you can get what you need at 1700 RPM and the engine is operating efficiently in the "Powerband" there is no need to step it up. Only if you are out of the efficient "Powerband" of the engine and will lug it around is this necessary. What you are arguing is an increased load... yes, gearing steps up the drive force at the tires in exchange for speed. Dropping out of OD into 3rd will help to get into the powerband, but once there and you have what you need, you want further increase efficiency by shifting into 2nd and going up to 4500RPMs. The big increase you are talking about here is vehicles that are as aerodynamic as a box. If you want the best economy, I wouldn't try to drive one of these at a speed where it can't operate in lean cruise at a low RPM.

 

Well, you got one part right. Someone here certainly does need some basic training.

 

Wait...WHUT!!? Didn't you say above that you got better mileage at a higher RPM?? :bigears:

Will also tell you their is a huge difference between towing a little boat behind your little truck and towing a 6,000 lbs travel trailer that is 11' tall and 8' wide behind a fullsize Express van. Huge weight and frontal area difference. I would place a bet his high top G20 van has higher engine load because of the aerodynamics at highway speeds than your truck pulling your boat.[/QUOTE]
1. What do you know about my boat?
2. My "little truck" very likely weighs more than your "little van". ....although it doesn't matter for the purpose of the discussion; they're BOTH anecdotal, "tall tale", worthless stories and examples. :yesnod:

So...that's it then, right? THINK. Do you suppose the injector is firing more pulses per unit of time, at the higher RPM? Hmmmm.....

 

Here is my response to all the latest, and the latest update to my original plans.WOW this page sure LITE Up all of a sudden.

I believe I have done my homework One book I have read and own is Trailer Life’s RX for RV performance and Mileage by John Geraghty and Bill Estes Copyrighted 1983.

While lacking any detail of Fuel Injection, it covers every aspect of running a heavy truck, Van and trailer towing and Motor Home.

Add in my own personal driving for 58 years and the Lessons I have learned.

First I totally agree about cubic inches even centimeters. My first motorized transport was a Honda 50 at the age of 14. It could hardly hit 50MPH, an add a passenger and forget it. It was a 50CC engine rated at 5 HP. I then got a Lambretta scooter, with a sheet body, leg shield, wind shield, even a hand shield, plus a spare tire on back. It could carry all that, myself and a passenger all day at 50 MPH, it was a 125CC rated at 5HP.

Next I got a 56 Studebaker with a 286 and a 3 Speed with over drive. I normally beat the 65 289 Mustangs across the intersections where my 5000RPM red line forces me to shift and they would run away from me. I have a heavy car with a full frame they light unitbodys. My Studebaker was a stroking torque motor.

I had a 74 Chevy Van with a 350 which with a TH400 or TH350 could easily clime the hill outside Indio CA one of the longest climes I have hit and it could hold 70MPH all the way up. It was running at the torque peak of 2800/3000RPMs. Gas mileage was at best around 10/12MPG. I was driving during the gas shortages of the 70s.

Next came a 78 Chevy van with a 350 and TH350. Same as above. Engine was worn out so wanting one with a better life I swapped in a OLDs 350. Gained 1 to 2 MPG. Sadly as a used engine I lost a rocker arm on a run to Chicago, she limped back to Phoenix AZ, where my friend whom gave me the 350 only had a OLDs 305, so popped it in. WORST thing I ever did, even with a TH350, MPG dropped below 10MPG, and I was honked at by Big Rigs for being in the way claiming hills in 2ND.

It was this very site that really got me super interested MPG with an old thread from the 90s about a bragging contest with Camaros from Australian and when all other brags matched THEY said OK But we get 30 to 35MPG!!!

That was I believe the first time anyone heard of Lean Burning Cruse in the PCMs.

I bought three compete TPI setups, planning to use them for a high Mileage car/van.

Life got in the way for my plans.

But in 2008 when gas prices climes up to $4.00 in even Phoenix AZ, I got back into trying to get better MPG.

Out of all of that the thing I found was a 2000 Mercury Grand Marques ( a Crown Vic) that got on the highway on pure runs did 30MPG at 65MPH at 1700RPMs with stock tires and a 3:27 rear end.

Take her up to 85MPH and she got 24MPG at about 2400RPMs and drop to 75MPH at 2200 RPMs and she got 25/6MPG.

By hook and crock I got her to 16.5 A/F and she got 35MPG at 65MPH.

Everything I have read has said take a engine with a 2800 Torque peak and LUG it at 1800RPMs and it will not get good MPG.

All the above posts all say that. ALL say they got better MPG running in the power peak.

And with a STOCK or even worst a performance engine that is what only can happen.

So I am building an Chevy 383 engine specially for low rpm My plan is for this motor to spend most of its life running at 1700 RPMs and operate from 1500 to 4000. Everyone builds a Hot Rod version.

The choice of a Cam had become a nightmare obsession. The cam is THE MOST IMPORTANT part of an 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’s gearing up to cruse near your engine’s torque peak. I was facing a nightmare chose, runa small LOW power band cam and kiss any power over say 2500 RPMs or get a hoped for good mid range cam that MIGHT have good power below 2500RPMs....

This NOT as insane as many think, the Classic Chevy 400 had its torque peak at 2000RPMs as did the OLDs 403.

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.

THEN I found this: 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-...torque-7988109.…

I combined the notes to what I am doing. From “It Still Runs” articles:

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.

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

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.

This gave me a base line.

Instead: I matched their specs to orcam@pacifier.com # 806 cam, nearly this same profile that It Still Run 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)

THIS is the POWER part of my CAM setup.

I will be running Rhoads V-Max roller lifters, and with Rhoads Lifters running at 10% reduction the cam will be:

180/192 115 .396/408 at low RPMs THIS is the MPG part of the CAM. SO at 3000/ 3500 it will be running the full cam’s 207/214 @.050 117 440/454.

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 3000 RPMs which will give me a big power boost.

“It Still Runs” said an engine built to this spec (minus the Rhoads Lifters and heads) 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 also 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…

I am waiting the engine’s rotating assembly to be balanced with my special Teflon and ceramic coated KB pistons. The Teflon is because I am using a Chevy 400 crank with the 5.6 rods which is reported to add side loading to the pistons, and the ceramic coating as I plan on running Lean Cruse mode.

With ceramic coatings the idea is to keep the heat of combustion IN the chamber and stop it leaching into the metal of the pistons and the heads, thus both making a cooler running engine and making all the heat be used for power. As I plan on running lean burn cruse this will help protect my heads and pistons from the higher temps within the combustion chamber.

I decided that with Rhoads lifters I could seemly have my cake and eat it too, because these lifters lower the cams profile 10 to 20% at low RPMs so I can have a mild cam but at higher RPMS it become a power cam.

Read up on them here: https://duckduckgo.com/?t=ffnt&q=Rho...ifters+&ia=web

I found great reviews on many car and truck sites about how Rhoads Lifters gave a great flat power curve.

AND Thanks to Oregon Cam Grinding, Inc.

5913 NE 127th Avenue #200
Vancouver, WA 98682
Phone: 360-256-7985

And their large list of cam profiles I was able to choose a CAM that is what I wanted and costs was great. I wanted a cam strong enough to lose 10% for the low RPMs and powerful enough to make good torque and HP at the 3000 RPM to 5000 Top RPMs for this motor.

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

I am holding off on doing the TPI Intake and PCM until winter and after the complete braking in of the new engine with the vans stock TBI fuel system.

This will also allow my testing and recording how much changes I get from this special engine. It will also allow my seeing what MPG changes I get first with it and then with a special lean cruse chip for the Vans stock TBI PCM.

I plan of tuning the TBI for best MPGs and then adding the second OVER DRIVE, which will allow low RPM cruising at higher highway speeds: 80 MPH w/o second OD = 2660RPMs, in second OD = 1862. This will be a old Borg Warner OD from a 50s 3speed with OD Transmission.

I believe my special engine will be able to pull the Van easily at these speeds and RPMs gaining about 30% more MPG, or get 20MPG+ up from the Vans past 14MPG. And I know it will not do that on hills...just level ground with no hear winds.

I then plan on adding the TPI system which is also reported to give 20 to 30% more Torque, HP, and MPG ASAP.

This should be a great engine, and put back onto the road a great van.
I am building this engine as we write.

I will report my findings no matter what happens.

Rich

 

Some need Thermodynamics

 

That simply isn't true and believing that is going to get in the way of your goals. How do we know that isn't true?
1. There is no such thing as "lugging" anymore. "Lugging", is a psychological problem...not an actual one.
2. EVERY vehicle made today operates at a lower RPM than it's tq peak and also gets better mpg than it would at it's tq peak. Nearly all engine today make tq peaks at ~4000 RPM or so. Yet they run down the highway "lugging" at ~1500-3000 RPM or so, getting way better gas mileage than they would at ~4000 RPM.

How does that fact, align with the claim(s) above? It doesn't because the claims are bogus.

 

1. What do you know about my boat?
2. My "little truck" very likely weighs more than your "little van". ....although it doesn't matter for the purpose of the discussion; they're BOTH anecdotal, "tall tale", worthless stories and examples. :yesnod:

So...that's it then, right? THINK. Do you suppose the injector is firing more pulses per unit of time, at the higher RPM? Hmmmm..... [/QUOTE]

My Express van has gone over the scales at 6,400 lbs with a full tank and me in it. The full conversion package with rear a/c, power sofa bed, lots of wood and electronic gizmos as well as that 10.5" rear, 1 ton suspension, class 5 trailer hitch, larger front sway bars, added rear sway bar, heavier 1 ton rotors and drums and 2 house batteries have all weighed it down a bit.

That being said RPMxInjector pulse was still lower at 3,000 rpm than it was at 2,000 under load.

 

I never said that running at extreme RPM was the answer. What I suggested was a little more gear would often help when the vehicle is undergeared. My target is usually 2,500 rpm @ 70 for an unloaded small block truck. I have a deeper gear in the Express because I tow and run in the 13,000-14,000 lbs range often.

 

Not sure why you're explaining the details of how you've added 1500 lbs to your van.

I believe you that the Pulse width was lower at 3000 than it was at 2000. Who knows if it was "same conditions" (you don't), but even assuming that it was, do you think it's possible that the injector is firing more times per unit of time at 3000 RPM than it is at 2000 RPM?? :bigears: THINK, now.... So if it's firing 33% more pulses in a given period of time....is the pulse width greater than 33% shorter?

I can't believe that this needs to be explained, but here goes: the reason why I said to compare pulse width at 2000 and 3500 (or what ever numbers you pull out of your *** for "better fuel economy"), no load/in neutral, is because that is a somewhat controlled situations; The only load on the engine is it's own friction. Therefore, 100% of the fuel being burned is being converted into heat -no work is being done. Therefore, you can compare the diff in engine friction/waste at one RPM and any other RPM....and you know that 100% of the difference, is wasted fuel; it's added fuel that did no work, other than to create more heat. You came back with some cockamamie story of climbing some hill....we don't know that the conditions are the same while you're doing your comparison and you likely don't either, because you've introduced a barrage of variables. But if you KISS and just look at an engine at idle, 2000 RPM, 3000 RPM, 4000 RPM and so on, you can literally SEE with your eyeballs, the increase fuel used to get to those RPM's. And you can see that 100% of that additional fuel is doing nothing but making heat.

A corresponding amount of additional fuel is required to drive down the road at 4000 RPM vs. 2000 RPM (or whatever RPM's you want to pick)....and that is why OEM's have OD ratios in the transmissions. Because the OEM's all know, that at a lower RPM, the vehicle will consume less fuel. Someone (the people who build these vehicles) have already figured this out for us. :yesnod:

 

There is a difference between cruising at the lower end of the powerband and lugging. My V6 makes peak torque around 5,200 rpm. It cruises at 3,000 rpm. It gets good highway mileage even spinning 3K @ 70 and 3,800 @ 85.

 

Tell us about this. What IS...the "difference"?

Because there is no such thing as lugging, anymore.

:BIGEARS:

Anyway, racprops said:
^THAT^ is what I was responding to where you quoted me above...and it simply ain't true. You're V6 gets better mileage at 3000 RPM than it does at 5200 tq peak for a given condition...right? RIGHT. And so do all other engines.

 

That does seem true, as was it seemly true for the 2000 Mercury.

BUT A 281 Ford will not fit into my van. Nor do I think it would be able to pull it.

Yet even with all of that it is rare to have a snappy performance car get much over 30MPG with ALL the improvements.

I am dealing with a 1993 Chevy Van. A much fixed up and loved 93 CHEVY Van.

I am building the best engine I can that will FIT into the engine compartment, use the vans transmission and all the other Chevy stuff.

I am very aware of the power curve, torque curve, the wind restrictions, rolling restrictions, weight, and hope all with come together and work.

ONLY torque will pull all of that down the highway. I believe my engine will make enough torque to do the job. Evry van, car and SUV that I own gets 30MPH at 1700RPMs, only thing is their gearing makes that 1700RPMs to be around 60MPH.

I am all in, as soon as my machine shop complete the Balancing I will start the final assemble.

Then it is swapping time.

Rich

 

Lugging is defined as where the engine does not respond to additional throttle at lower rpm because it cannot overcome the load of the gear it is pulling against.

Lugging absolutely is a thing. Just because I can put my 6 speed in high gear at 15 mph doesn't mean it has the power to move the car.

I could program my 4L85E to shift into the next gear at 1000 rpm but it would probably stall going into the next gear.