Latest update, on my dream of building a high gas mileage custom 383 engine for my 93 Chevy G20 Custom Van.
Last week, June 5th. 2020 the Machine shop has finally delivered my balanced rotating assembly spun to .0 balance. This project was started back in Nov. 2019 OMG.
BUT Due to so many delays getting my machine work done I was unlucky to not even consider doing even a straight engine swap as the AZ Summer has put a stop to any engine swap work.
So this summer I will be doing the final assemble.
Here are the details of the engine and my findings and thinking behind it:
First back around 2004 I started to build a 350 as a low RPM engine with the idea of setting it and the drive line up to cruse at 1800/2000 RPMs at around 80MPH. I believed using a 85 to 90 Chevy TPI system with its special PCM with a hidden feature of a Lean Curse I could see 20+MPG with this van.
BUT the 350 in my 93 Van would not die. Until a couple of years ago when a oil line to a oil cooler let go sizing the engine.
So the project was back on. As 80% of the engine work and most of the parts and head work was already done, I decided to go for the full boat engine I really wanted, a 383.
ONE main problem was I had already spent a bunch on a special set of pistons and the block was all prepped for them and really want to keep them, building a modern 383 with a new complete rotating assembly of a crank, rods, pistons had two problems, cost and the complete restart to the build along with a ton of extra problems making all of that aftermarket stuff work.
The best way for me to was OLD SCHOOL, use a Chevy original 400 cranks and machine it to fit the 350 block (real old school) and to use Chevy original 400 rods. This set up was far more likely to have fewer clearance problems.
And as I was fully happy with an engine that would run strongest at 2000 RPMs and not run over 5000RPMs, all this should work grate.
Getting all of this fitted and machined, coated and balance is what cost me 6 months.
So I began deep new research, and 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. 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. 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.
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 originally had been working on getting an engine set up to run at a torque peek of 2000RPMs. But this seems to limit other factors as passing and mountain climbing.
The more I learned the more it seemed I was going to box my engine into only having power under 3000RPMs, this began to seem like a bad idea.
I had known of Rhoads Lifters for decades but until now they only did flat lifters, then I found they now do rollers and we were off to the races.
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 at say 1600RPMS but at higher RPMS around 3000 it become a power cam. I will be setting them for the 10% reduction.
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.
Instead: I matched their specs from the It Still Runs article 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)
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 yet at 3000/ 3500 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 1800RPMs 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 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%.
Talking with two engine builders I have been told that because I had the pistons both Teflon and Ceramic coated that they will run so much cooler that instead of running a .030 ring gap I should run .015…that impressed me so much I am also had the combustion chambers and valves ceramic coated as well.
The Teflon Coated Piston Skirts are because I am using an original Chevy 400 crank with the 5.6 rods which is reported to add side loading to the pistons, this coating is said to lower the wear to the block and pistons.
BUT I double checked with both the maker of the pistons and the ring maker about this and was told that I REALLY NEED a large gap as the heat will really hit the upper ring because of the coatings and ground them to .035 for the upper ring and .020 for the second ring. Otherwise I would be risking ripping the top of the piston off due to ring seizing.
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.
And as I plan on running lean burn cruse settings this will help protect my heads and pistons from the higher temps within the combustion chamber during such operation.
BUT I WAS still thinking of running a TPI system next year that is reported to add 20/30% more torque, HP and MPG…BUT that is now in major rethinking:
From around 1995 I was totally convinced that the Chevy Tuned Port Intake was the secret hidden answer for great low and mid-range power. I also felt that sadly the possibility it could make better MPG was dropped for higher RPMs and thus higher power, especially advertise HP on the sales ads. At this time I was reading about Camaros getting up to 35MPG thanks seemly thanks to the Tune Port Injection system and a feature hidden in the PCM called Lean Burn Cruse.
There were lots of reports of a TPI system giving 30% more torque, HP, and MPG. These reports were at that time I was lead to believe were compared to the other system being sold at the same time that being a crude system which was like fuel injection system stuck on top of a carburetor system, this was the Throttle Body Injection system with two fat injectors shooting into a seemly standard carb intake.
I also thought that after getting a 2000 Mercury Grand Marques and later a 2003 Ford Crown Vic both running the Ford 4.6 motors which is in fact is ONLY 281 Cubic inches (smaller that the many 289CI motors I owned as a Teenager) and making 200 and 250HP and running like bats out of hell, WITH Ford’s version of the Tune Port Intake and both limited to 5000RPMs and with the Mercury getting 30MPG at 65MPH and the 03 VIC with its 50 More HP and 25MPG was proof of concept.
I have lately found reports that this TPI comparison was in fact between an old Carb systems to the new TPI Injection system. And that the TBI can nearly match it.
My thinking has been as the automotive world kept seeking higher and higher Horse Power and more Wiz Bangs they did so at the cost of better MPG, it seems great to have 400 to 700 HP but the MPG has been basely unchanged from the 80s at best around 25 to 30 MPG (Still, after some 40 years).
BUT I have run into some arguments such as finding the above comparison and that the TPI system is in fact tuned to 2800RPMs. And although I found few Dyno tests of any stock TPIs systems the few I did find did favor the mid-range, it did appear to be fairly flat from 2000 to 3500RPMs.
BUT As my main goal is for a maximum torque at 1600RPMs I have been told by a number of friends, car nuts and seemly a couple of articles that claim an old fashion 4 barrel dual plane intake fed by a TBI intake system will in fact make better and more torque at 1600 RPMs that a TPI.
As the effort to convert the engine to a TPI system along with the near nightmare of fitting a second PCM and the entire wiring nightmare where I can no longer be sure it will even be an improvement over the dual plane intake and TBI system especially at my chosen cursing 1800 RPMs . This makes me question if it will work or not and can I afford the time and effort to install it.
MAN I wish I could find an engine dyno with the ability to test from 1500RPMs in the greater Phoenix AZ so we could test the TBI setup and then switch to a TPI system and thus compare JUST the differences each will make on my special 383 Van MPG engine. But I am told that could cost around a thousand or more to do.
As I cannot install the engine until late fall early winter around September, I am going to build an engine brake in light test stand so I can perform the early testing and brake in and it first oil and filter change and re-torque torque the heads etc.
This will kill the awful suspense of a three month plus wait for cooler weather and worrying all summer long to learn: will it run and not break something because I missed something or made a mistake. Hopefully if there is something wrong I can catch it right off the start and it can be something fixable.
And add to all of this in researching the use of the van original PCM to possibility run the TPI I learned that the Lean Burn Cruse special chip that had made about 10 years ago that had not worked was in fact plugged in incorrectly, so that I was running the stock program, so there is a fair change I will have a lean burn setting once the engine is broken in and I run it correctly this time.
It will also allow my seeing what MPG changes I get first with it and then with a special lean cruse chip I already have for the Vans stock 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.
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.
This should be a great engine, and put back onto the road a great van. And I will feel less guilty driving a better MPG Van than stock. Or taking my Wife's 2000 Toyota with its 30+MPG.
Today
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