hotrodding the 4.3 V6 (tips & tricks)

drmmhmd said:

astro355 said:

You know, I appreciate your efforts here. There are two very important things that should be mention, first.

Most importantly, proper maintenance. Not enough can be said for staying on top of the maintenance. That includes all fluids, tune-ups, tires, and just keeping everything clean.

Second, the exhaust. The most restrictive part of these vans (and many other cars out there) is the exhaust. It doesn't matter how much air and/or fuel you shove down the intake, if the exhaust holds it up, its all for not. Its the hourglass effect, weakest link in the chain, etc. A lot of people don't like headers but they are the best bang for your buck, period. But there is something else that can be done, replacing that stock catalytic convertor with an aftermarket version. All catalytic converters do the same thing but aftermarket versions flow 3, 4 or 5 times as much as the cheap stock equivalents.

:2:

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headers do almost nothing for horsepower increase on stock motors.

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X2.Some stock set-ups do rely on back pressure for their performance.Headers should be the last thought AFTER all the other mods are in place.Quick fixes for performance are just that in results.Everyone thinks incorrectly that just by hanging on a cad or muffler they are now in the same place as a guy who knows how to smooth flow a induction system.(head work done,cam that matches,rear end ratio that capitalizes on peak torque/HP ranges,matched injection system,etc.)I just take moves like a exhaust cure alls as a lazy mans fix or one that is totally misinformed. :2:

I want to explain my self alittle better.The real question is does headers on a stock set-up work,at idle-nope.So where do headers really start to work??.What RPM??.How about at 2500 RPM??.Well truthfully not much there either.How about at 3500 RPM-just starting to have somewhat a effect,about 2% or less.My point is like any other engine these are air pumps.Air pumps that need a balanced in and out.Stock air ratios run out of fuel/air by the time headers have any effect.In fact header "could" create a lean condition which is not good for stock engines.The ECU feels it needs to put in more fuel and at best it is still within the limits of the stock injector system which is not enough.That headers also need to have a active 02 sensor.Also there are limits to the stock cam and kit in these engines.So by the time you have reaped any real benefit from headers and their scavenging effect,you have run out of RPM.Got to be mindful that headers are truly for HP and because of that their effect is in the upper RPM ranges.The concept is HP is a peak in the upper RPM ranges.Also small C.I. engines by the nature of their size have a HP peak in the upper RPM ranges.So if you want to get to use say 5 to 7 hp at best.............Well I think you can see what I am saying.No giant killers there.

The idea of a tune on a engine is now and forever will be big picture.Total concept and not just one pc of it.

What is so disheartening to me is a guy that just because it is louder thinks it has more output and walks round with his chest pumped out having done only one thing.It is his mind game that I really don't want to be apart of.Again just my :2:

Not everybody was born with a silver spoon in thier mouth and can afford these kind of complete motors.Kids today are hot rodding hondas because that all they got to work with.It a free country where you are(quote unquote) in the pursuit of happiness.If it makes that guy with the puffed up chest happy I say more power to him.The octane requirement and the computer were designed to defeat performance in these engines.That is part of the hot rodding spirit trial and error learning.Friend of mine had a 71 chevelle he had less than 150 bucks in it.It ran 12.70 in the quarter consistently for 8 years just headers.Stock motor.Computer is your biggest performance enemy on these vans.I posted my speedo and I got a 6 second better 0-65 times than factory. Not spending a dime just tuning the beast.A car/van dont have to be a 9 second machine to be enjoyable to drive.But at least get the performance out of it,it is capable of.Dont be defeated all or nothing.I dont understand that train of thought.If I cant compete in NHRA drags I will make it run as poorly as it was factory.Seems self defeating and sadistic.The purpose of this thread is how to better enjoy your van.Not how/why to hate its engine. :2:

Well, if the headers only work, as you say, in the higher rpms, they do still work and do provide an increase in HP.

My van was built by GM with a 5 speed.
Maybe you do not rev your van up, but I regularly shift it from 5th down into 3rd on the highway when I wanna pass.
It revs up to around 5000 RPMs before I shift to 4th. and then on to 5th.
Those are the RPMs I wanna bit more power at to get my speed up quicker.

I once had a jeep CJ7 with a 4.2 litre straight 6.
Bone stock it was sluggish and guttless as heck!
I figured a brand new Weber 32/36 2bbl Carb would fix that.
Well, that made it run a lot smoother, but really no more power.
Then I installed a set of Hedman tri-Y headers.
The torque & H-Power increase was mind blowing at all RPMs.

What did you use for a induction system??.From what I have seen so far,it has been hard to duplicate the fuel curve on EFI systems.The TBI's in stock form are very limited in the a/f ratio.That is especially true in the top end where injectors which are not large enough have no choice but to lean spray consistently.

We have strayed from the author of this thread where I read his posts.I give credit for understanding the how and why in his suggestions.I am saying a starting point is truly from the inside out.If it where a matter of a rebuild for a user of a 4.3,that would be a prime time to make a 4.3 more efficient with go fast parts.That could be pc meal together over time.Even a cam swap,change to a mass air flow over a map sensor(map's are a very limited output sensor),and larger injectors with a increase of fuel pressure with a external fuel regulator, some minor intake porting,chip burn and then maybe headers makes more sense.

These are still air pumps.Air/fuel in and air/spent fuel out. I have seen the results in what RPM ranges headers work from the header manufactures themselves.It is kind interesting that result is oddly missing in their ad's..................

chevymaher said:

Not everybody was born with a silver spoon in thier mouth and can afford these kind of complete motors.Kids today are hot rodding hondas because that all they got to work with.It a free country where you are(quote unquote) in the pursuit of happiness.If it makes that guy with the puffed up chest happy I say more power to him.The octane requirement and the computer were designed to defeat performance in these engines.That is part of the hot rodding spirit trial and error learning.Friend of mine had a 71 chevelle he had less than 150 bucks in it.It ran 12.70 in the quarter consistently for 8 years just headers.Stock motor.Computer is your biggest performance enemy on these vans.I posted my speedo and I got a 6 second better 0-65 times than factory. Not spending a dime just tuning the beast.A car/van dont have to be a 9 second machine to be enjoyable to drive.But at least get the performance out of it,it is capable of.Dont be defeated all or nothing.I dont understand that train of thought.If I cant compete in NHRA drags I will make it run as poorly as it was factory.Seems self defeating and sadistic.The purpose of this thread is how to better enjoy your van.Not how/why to hate its engine. :2:

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First, there is no factory 1971 chevelle that ever ran 12.70, this is the year that compression ratios were dropped to 9:1 or lower and the 454 only had 365 hp. if you plug the hp into the usual equations you will find that 12.70 is impossible in "factory trim". computer controlled systems were not created to defeat performance but to aid performance and improve fuel efficiency and emissions. that is why 3 litres engines of today routinely make more power and less emissions than a 454 in 1974. the computer on you van is not a performance enemy, it is designed and programmed to provide consistency, performance and reliability, far better than the average tuner can. the computer can be programmed for any modification.

the newest version of the 4.3 engine makes 200 hp and 260 ft pounds of torque., this is very respectable for 262 cubic inches. If you look at that 454 in a 1971 chevelle it made 365 hp or .804 hp per cubic inch. the 4.3 litre (262) makes .763 hp per cubic inch, that is, the 454 with its massive valves and huge ports makes 6% more hp per cubic inch. the worst 454 made 176 hp at the height of the air pump OPEC and emissions wars. the issue is weight, it is easy to make the 4.3 make more hp and torque but you are still trying to move a very heavy vehicle. buddy with his headers at 5000 rpm isn't going any faster and if he is driving at 5000 rpm in 3rd or 4th he should be put in jail. not sure which van came with a 5 speed.

The mazda 3 makes 167hp with a 2.5 liter almost as much as the 454 you mentioned and that would be 288 horse in our vans.Yes I have a tuning issues with that.I am sure the mazda passing emissions.Any monkey with a wrench could tune a 375 horse 396 and get 500hp with headers it been done a hundred times.Where that OBD1 tuning program you talking about.Oh it does not exist.Replace the computer buy a tuner and program.1000-2000 bucks and you have not even touched the engine yet.Yes I consider that a performance enemy when I can buy a faster car for the money it cost just to tune one.Or buy a carbed 450 hp 383 and stick it in for the same price.The 2 MPG and 8HP claimed computer over carb set up is not worth the money.I can drive a long way on that much money.The 71 chevelle had 135 bucks in it.Ran the number 8 years headers 4bbl 4 speed not that tough to do hang at the strip a day.No it was not in factory trim it had a highly restrictive single exhaust 2bbl 3 on the tree.Glad you brought that up it kinda was the point.Show me any computer car where you can increase performance that dramatically for 75 bucks 10 hours work and some junk most would have thrown away.Yes he paid 60 bucks for it.And for the crack about him needing to go to jail.Nobody ever said he was doing 165MPH late at night coming home from work.Beside you said it was impossible so I guess he safe.

I am surprised at some of the posts I read here ,,, for generations one of the first things to do when trying to get more speed , hp and torque is to increase the amount of fuel/air into the engine to create more power , hence the reason engines began to be increased in engine displacement size , Not so good for mpg , but that was not the goal , the goal was more power.
Nowadays with the advent of the computer designed engines factory roller cams , better sequential fuel injection and various technologies we can now make good power with smaller size cubic inches . Carbs ruled in their day , but that was yesteryear , they can still be made to run strong , but it does not make for as an efficient running of an engine and equal the mpg of modern SEFI . Back in the days of carbed engines one of the very first things to do to increase power was to get the exhaust opened up and let the engine breathe freely .

Switching from single exhaust to duals was a 15 -20 hp increase and then adding a 4 bbl carb in place of the 2bbl carb was another 15-20 hp , and could be more depending on who built the carb as there was people like Barry Grant that could squeeze 50 additional ponies out of a carb just by the way he built it , But forcing more juice down the throat of an engine without opening the exhaust for better breathing was really quite useless because it would create a bottleneck .
Step up from plain duals to headers , now you can increase hp to at least 15 hp or more depending on the setup . But it will depend on the design of the headers as to what hp torque you get . On the street one needs long tube headers because of the use of low to mid range rpm band , the short tube headers will push the torque increase into the higher rpm range , so in order to see the benefit of short tube headers the engine needs to see the high prm ranges not usually found used on the street but mostly on the race track which is why most race cars will have short tube headers ,On the street you really need the torque/hp at the low rpm range in order to successfully launch at the start or tow a trailer .

Headers are a tuning luxury so to speak , they are not necessary for most applications on the street . The main reason if not the only reason tuned headers are not on all factory production cars is because of design/testing and warehousing costs because there are so many different
engine /body/chassis designs of so many different models of cars would mean that car makers would have to spend hundreds of thousands if not millions of dollars to design and test the best header design for every make model and chassis design there is . This cost would then be added to the cost of every car . The term "tuned headers" is specifically called that because each individual primary tube on the header is specifically "tuned" for a specific engine/chassis . The length , diameter and shape/bend of each primary tube is tuned and tested on a dyno to find the most torque and hp for a given engine and vehicle design . Even though having the very best tuning for a given engine does not mean it will fit every vehicle that engine come in . this is the reason that car makers only make 'factory headers' on very specific High Performance cars in their lineup , as they just want to show what can be done to increase performance in their cars .
The cost factor that a factory would have to implement to design ,test , for all their cars would be much higher than an aftermarket setup . If you examine the aftermarket offerings you can find headers priced from a hundred bucks up to 1500 bucks depending on what brand , material and how well tuned it is as some aftermarket companies only make some sort of knock-off ;something that they can sell to the average guy who wants headers for a hundred bucks .

Any time a person wants to make real power from their vehicle it is necessary to calculate out what exactly do they want and what is needed to get it . Just throwing a big monster carb on an engine just may drown it with too much fuel , just as when putting on headers , it needs to be calculated out on the specific vehicle , You can't just put a set of racing tires on a car and then call it a race car . :lol:
Originally when computers were put on cars it was to monitor fuel and emission output to make a cleaner burning engine system to reduce the hydrocarbon emissions in the air . The OBD system , On Board Diagnostics were to aid in measuring and adjusting of the fuel/air ratio , engine knock and timing on the lean burn engine design of modern cars and has evolved into a system that can allow a person to dial in specifics to get an exact tune that they want for their car . There is a default factory setting , just like there is a default setting on your home PC, and there are software tools that a person can use to make a custom tune setting to fir their desire.

If a person wants to make changes such as adding headers , changing fuel system components to something that is not a factory setup then it will be necessary to understand how to make these tuning adjustments to make the best use of their hardware changes . The OBD system is a great system as it gets more specific detailed info for the tech to better understand what exactly is happening in their engine . In the old days when a tech needed to do a tune-up they had to replace the points in the distributor and would use an analog dwell meter to dial in the correct dwell for best operation , since electronic ignition came in , setting the dwell is no longer needed as it is done automatically by the electronics in the system . OBD is just the next step in the electronic evolution in today's cars . If a person resists and chooses not to learn the use of today's modern tools it is to their own disadvantage .

I may have missed something about the statement about the tuner program that costs 1 -2 grand , as great ones can be had for 5-7 hundred , but that is because it is for OBD2 , OBD2 has at least 14 different protocols , which is way more than OBD1 and OBD2 requires a hardware interface between the car and the laptop , while OBD1 does not need anything but a cable between the car and laptop ,,and the tuner progs are low cost and some are free .

In earlier days people had no choice except to buy a high dollar pre-programed chip to get a performance increase and that was a standard default setting for that chip , if a person wanted to make changes to their car performance to a higher level they either had to send in their chip to get it programmed again , or buy yet another chip ;Going that route is far more expensive than using an OBD tuner prog where you can make changes anytime you want without paying any additional costs and not even remove anything from car , just simply hookup your laptop and tune . I do not mean any disrespect to anyone , but just trying to open up a field of understanding .

I love the old 70's muscle cars , but I rarely see any on the road these days , when I do there are either a classic restoration where they take it to car shows or only drive it in the summer time and park it in the winter,,,,,or it may be just an old beater rust bucket that still is running good , The reality is this is 2011 and computer cars have been around for more than 20 years and we will never ever go back to the days of leaded fuel and carb'd cars in production vehicles . The likelihood of being able to commonly find a performance carb'd car that is in really good condition that does not need restoration and is not needing repair for 1000 dollars is almost nil unless buying from someone who does not know what they own .
Most of the cars from the 70's are gone to the salvage yard , very few are running around today and notice what they are , mostly some sedan that grandma drives or a car that is in some serious need of paint and body work .

In regard to the HP ratings that came from factory ; well before 1972 the way the HP was measured was not in a car at all ; it was mounted on an engine stand with no A/C , no PS , no power accessories , no full length exhaust system , and no transmission attached . This is what is called Gross HP .
. After 1972 the way the HP is measured is with engine installed in a car with A/C air , Power steering , any and all power accessories attached , with exhaust system and with the transmission attached , installed and the power measured at the tailshaft . This is called NET HP , NET HP is a more realistic measure of the HP that is available to the driver . So when you see HP numbers comparing between the Gross & Net numbers , the reality is the engine that can produce 300 Net HP , is actually producing more HP than an engine that produces 300 Gross HP
If we take a close look at today's muscle cars , we can see that they can produce 350 Net Hp
and still get 25 mpg, no 70's muscle can do that .
I just read and article of the 2012 Camaro factory stock supercharged at 556 NET HP
and a V6 at 323 Net HP

I have not seen or heard of any V6 non-computer controlled car that can produce even close to that amount of power .

With these statistical facts..... to think that a carb'd factory car has anything superior over today's computer muscle machines is something to rethink and come to the realization that today's computer muscle is Far Superior too any factory carb'd car .

I am not even saying thier not better just expensive.To the average joe it cost prohibitive to do anything at all to them to increase performance.And as it has been said so many times on this forum it just cheaper and easier to stick in a V-8.Since we brought up superchargers.My brothers monza had 900 dynoed RWHP with a carbed 383 and a 6-Speed and 20lbs of boost.21 MPG and I garentee he had alot less in it than either factory supercharged car you mentioned.Theres an apples to apples comparison not an apples to oranges.I am more concerned with performance than mileage a few miles per gallon difference wont kill me.The van already gets the same milage as my chevelle.His charger in my album has a wicked 440 ready which will be also a carbed supercharged car.We will see soon what the milage is with the OD I am sure it not great.Even after restoration and motor it still alot cheaper than his next door niebors non supercharged camaro which has 400 hp I think the dealer said with the modifications they did.His 2004 GTO got 26MPG ran a 13.My chevelle when done will run same range high 12 low 13 get 20 MPG even with its rediculous cam.Cost 15 grand less to build and be worth the same thing when it done.All I am saying is for cheap performance gains you cant beat just cranking the timing and changing a cam and jet in the carb and headers.Seconds faster time for 300 bucks if you know what to buy.Those days are gone I know it as you pointed out.But that dont mean I have to like it.

The average Joe these days has to get a loan to buy most cars even most used cars today unless they get a 1-3 thousand dollar car , computer controlled cars came out in the early 80's so as I said before there are not many non computer controlled on the road these days, very uncommon , There are auctions where cars can be had for a low price , a good friend bought a late 90's Lesabre with only 79,000 miles on it , garage kept with GM certified used car papers from previous owner for 500 bucks , all it needed was a steering column because the ign switch area of column was broken , engine looks and run new , and quite fast too.
In regard to superchargers , there are many styles and types and brands , I remember a friend who had the type that stood up through the hood that had massive HP , more than what a factory production one makes , they just like other parts are varied in what they can do . the only reason I brought it up was to illustrate that these are in fact computer controlled cars that make big power , even the low end 6 cylinders today make as much power as a V8, I just trying to show that thinking the computer is the enemy of performance of cars today is simply not true , In fact it is one of the very best things that could happen to cars . Example because of the computer we can have in real time diagnostics access to seeing real time voltages in ignition circuits to find specifically which plug is misfiring , we can see fuel/air ratios adjust more accurately than just guessing at turning a screw a looking at a vacuum gauge. Finding what voltage a coil is firing at , many types of resistance values , many types of info all contained in one laptop computer , Can run 0-60 times ,,1/4 mile strip times to the thousandth of a second ; again all in a laptop , No need to spend a lot of money buying 40 different tools for diagnostics when nearly all diag tools are in a laptop pc. All it takes is for a tech to be willing to learn and grow with the times of modern technology .
I do like the old muscle cars and big cubic motors , they always get my attention and glad they are still around , but I also like cars that have a new appeal , nice clean fresh interior , not some old worn out cracked interior . I have restored several cars in my time and enjoyed it , but in today's economy to do it right and make it new cost more than it does to just search for one that is already done , as the resale value of many muscle cars are not as high as they used to be , plus it can be driven right now instead of having to wait months to do the work or wait till the money comes in to finish it ,

I do advocate that people get familiar with the OBD progs if they want to work on their own or other peoples cars because most people buy as new as they can afford and if you not familiar with OBD then you limit yourself from some potential income not knowing how to use OBD, It is often recommended that when a person has problems with their vehicle to use OBD live scans to help determine what the problem is , To each his own way .

For OBD1 there are several good diagnostic programs available for free and spend 60 bucks for a single cable to hook to their laptop is as about as cheap as it can be to start using OBD to diagnose vehicle problems , time is money , so saving time with the use of computer programs in order to better ones self is always a great advantage.

The TBI MAP sensors do not like performance applications.Those need to be adapted to MAF sensors.There is a company the eliminates the use of chips in obd1 systems as a piggy back system and there for no more back and forth for a chip burns.In the link click on the different sections to see how it works.

http://www.dynamicefi.com/TBI_Fueling.php

The computer systems are sensitive to cam profiles in this way.Not much over 230 duration and really not much below 112 cam lobe centers-114 being better.

It is still to purchase a really good system like Edelbrock Pro flow very expensive.The Fast systems will nickel dime you to death once you have bought all the parts and Holley Commander 950's are still in the low $2,000 once you have all the parts.

The balancing act in tuning is to not have a over rich idle and still have enough flow for the top end.Remember these injectors have to be able to cycle fast enough to supply fuel at the top end.Some guys go for a enlarged injector with a increase fuel pressure knowing the injector doesn't have enough time to fully cycle and ends up almost consistently flowing fuel at higher RPM's.Of course they need to add a regulator to that.You can and should enlarge the bore size on a TBI to pick up more cfm.Much of that size is dependent on the selected cam,C.I., keeping in mind these EFI need a good vacuum signal to work.Still the above link requires a lap top for tuning.The weather conditions and the where you are with the vehicle does come into play in the tune.So you never get to cut the USB cord so to speak.

I am a fan of the SFI's because of the more exact fuel management and know the trade offs because of the design of the system.

As usual I know your right but I really old and hate to let go of the muscle cars.I grew up in it and I love it.Thats why I got the van I drive it right now while I do my car.So go ahead just kick an old guy when hes down I can take it.I am starting to play with the computers and I do need to break down and get me a laptop OBD1 and 2 cable since it obvious I stuck messing with them the rest of my life.I just hate seeing the dinosaurs dying out.I in a circle of muscle car people there are 8 like new cars in my family already and many more have passed through our hands.Then there are friends cars like the El Camino which was in the background of one of my chevelle shots in the album.We are doing our best to keep as many dinosaurs alive that we can.The garage my car sits in devoted to them.No new car ever sits in there unless it a major mechanical emergency.And there a 67 lemans in my house basement waiting its turn to be restored as a GTO clone.My car will have completely new interior by the way and it is not cheap.I am over it back to playing with the vans.And when they get old I will be fixing them forever saving them from the crusher.