Modding uprating the Chrysler 392 Hemi engine!

Modifying and improving: "392 Hemi Modifications"

392 Hemi Modifications Guide

How to modify and upgrade the Chrysler 392 Hemi

"Comprehensive guide to performance tuning the Chrysler 392 Hemi engine!"

Our friends at TorqueCars are regularly seeing threads about how to improve the 392 Hemi from people inquiring about getting more power from the 392 Hemi and wanting to know what are the greatest 392 Hemi mods that work. So let us look into Chrysler 392 Hemi tuning mods and outline the best mods that work on this great engine and point out some common pitfalls along the way.

Now we shall detail the best approach to 392 Hemi tuning and summarise the best upgrades. Chrysler 392 Hemi really good project engines and with carefully picked tuning enhancements like ECU maps, turbo upgrades and camshafts you will dramatically improve your driving pleasure.

The top 392 Hemi upgrades on an engine are obviously the ones that give the best gains for your money.

We won't be swayed by popular 392 Hemi upgrades, they need to be cost effective.

392 Hemi induction kits

Improving air intake on the 392 Hemi

You need air matched to fuel for an engine to work. If there is little supply of fuel then it will run lean, if there is little flow of air it runs rich losing power and potentially damaging the engine. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Pushing fuel and air into your 392 Hemi is the aim to any engine modification job.

It is common that there's a limitation in the air flow sensor MAF/MAP on the 392 Hemi when considerably more air is being sucked into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped power at a much lower level.

Headers transmit the on the suck phase from the intake filter and allow it to be pulled into the engine and mixed with fuel.

The shape and flow characteristics of the Intake can make a noticeable improvement to fuel atomisation on the 392 Hemi.

On popular production engines headers are crying out for an upgrade, although some car makers provide well optimised headers.

Adding a 392 Hemi larger valve kit, carrying out port matching and head flowing will also lift performance, and more importantly will make space for a better performance increase on other modifications.

392 Hemi performance cam tips.

Some 392 Hemi engines respond better to more aggressive cam durations check your engine on a rolling road.

The ecu map and fuel pump and injectors also will make differences on the torque gains you'll get.

Longer valve durations can alter the torque band and on most engines the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.

The camshaft profile plays a big part in the engines power output so camshaft upgrades make quite a large difference. The intake & exhaust durations will alter depending on the chosen camshaft profile, so large torque gains are on offer for camshaft upgrades.

NB: Fast road cams commonly bump the bhp and torque throughout the rev range, you might lose a little low end torque but high end rpm power will be better.

Race cams, bump the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Competition cam won't do well if driving in heavy traffic.

You should ideally match your bhp range to your driving style so for a car used daily stick with a shorter duration 392 Hemi cam

Stage 1, 2 and 3 mods for the 392 Hemi

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 392 Hemi parts:

Drilled & smoothed airbox, Fast road camshaft, Intake headers, Panel air filters, Remaps/piggy back ECU, Sports exhaust manifold.

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 2 392 Hemi parts:

Sports catalyst & performance exhaust, fuel pump upgrades, induction kit, high flow fuel injectors, Fast road cam, Ported and polished head.

Stage 3 392 Hemi parts:

Internal engine upgrades (head flowing porting/bigger valves), Competition cam, Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Crank and Piston upgrades to alter compression, Twin charging conversions.

Review your options and then buy your upgrades and set yourself a power target to avoid disappointment.

ECU mapping will help to establish the full potential of all the mods you've done to your 392 Hemi.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but figures achieved may depend much on the mods you've applied and the condition of your engine.

Turbo modifications on the 392 Hemi

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the 392 Hemi.

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes impressive power gains.

If a car is turbo charged upgrades are relatively easy and you'll see that turbo charged engines are built using more solid components.

However engines have weakspots

We recommend you find these restrictions and install higher quality components to survive the power.

There are many drivers spending a lot of money on turbocharger upgrades on the 392 Hemi only to see the motor throw a rod just after it's used on the roads.

Large turbos will usually suffer no power at low rpm, and small turbos spool up really quickly but do not have the high rpm engines power gains.

In recent times the choice of turbos is always moving on and we commonly find variable vane turbos, allowing the vane profile is altered according to speed to lower lag and increase top end power.

Twin scroll turbos divert the exhaust flow into two channels and push these at differently angled vanes in the turbo. They also improve the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large performance gains, although more challenging to get working. We have this article on twincharging if you want to read more.

Tips about fuel supply on the 392 Hemi

When you lift the performance you will need to increase to the fuel system.

More performance needs more fuel. It makes sense to over specify your injector capacity.

The accepted safe increase is to add 15% to the flow rate when fitting an injector, this takes into account injector deterioration and affords a little spare capacity should the engine need more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended 392 Hemi performance exhaust upgrades

You may need to increase your exhaust system with an upgraded one is if the current exhaust is actually creating a flow problem.

On most factory exhausts you should find that the flow rate is still good even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Sports exhausts can help increase the flow of gases through the engine.

But if the exhaust pipe is too large, ie: over two and a half inches diameter, you will lose a great deal of your flow rate and end up losing power and torque.

Typically exhaust restrictions are traced to the catalyst installed, so adding a faster flowing race alternative will help avoid this restriction.

Decats (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the 392 Hemi

Like most engines an 392 Hemi, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the 392 Hemi, failure to do this will exacerbate engine wear, on a tuned 392 Hemi this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your 392 Hemi why not pop over to the forums at TorqueCars where you can chat about 392 Hemi tuning options and read about others projects who may be planning to do similar modifications on their 392 Hemi.

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