|
|
 |
||
|
The Iron Duke Resource Site |
|||
| |||||||||||
|
Welcome to my newly
redesigned Fiero 2M4 resource site. The original site recorded over
12000 visits, hopefully this one will also prove as useful.
|
D.J.
Draper's Duke
D.J.
Draper outlines the steps he is taking to build a more efficient Iron Duke
rather than looking for raw power (which may not be there reliably).
Ira
Crummey
One
of the most important things you have to be aware of when trying to improve
the performance of the Iron Duke is the well-known fact that it has a weak
block. Remember that this engine was designed from the ground up to be as fuel
efficient as possible. High performance was never a major design goal of the
engine. Therefore, strength and the ability to accommodate higher performance
was sacrificed in the name of weight reduction. Low cost was another design
goal, so more aggressive steps to increase efficiency such as porting and
polishing were overlooked. It is in areas such as these that I believe the
performance can be gained; not by pulling more power out of the engine, but
rather removing obstructions or restrictions that are consuming the power that
the engine already has. I believe that if you are going to be successful, you
have to accept the concept of 'power through efficiency'. Any other approach
is going to result in a blown engine. I can almost personally guarantee it.
That
said, the next most important thought you should keep in mind is that of
properly matching all the parts during the rebuild. An engine with a
well-matched set of conservative parts will usually provide better results
than an engine full of high performance parts that are not matched. Take a
good long look at your driving habits and your expectations for this vehicle.
If the car has a manual transmission, what RPM ranges do you normally shift
at? What gear do you prefer to use when passing people? What speed are you
normally driving at when you decide it's time to 'get on it'? Is this a daily
commuter or a weekend sportster? Take these thoughts into account before,
during and after you start to rebuild the engine.
You
also need to be realistic about your expectations. The Iron Duke is a great
engine for efficiency and moderate to respectable performance. If you are
looking for a truly significant jump in performance, say more that a 25%
increase over factory rated HP; this is not your engine. By the time you pull
that much HP out of the engine, you will have spent a small fortune and in all
likelihood the engine will fail very quickly. This article is for those that
have more time and patience than money and just want to have a
reliable,
efficient, smooth running little 4-banger that gives them reasonable
performance when it is occasionally needed. If you are expecting more, go for
a V6 or V8 conversion. The bang to buck ratio will be much better with a
conversion approach and they are not as expensive as you might think.
If
you are an experienced mechanic and are comfortable with choosing your parts,
by all means do so. If you are a little foggy in this area, like myself, seek
out the advice of an expert in your area. Most of these people are more than
happy to share their knowledge with you, especially when they see that you
have already given some thought to how you want the engine to perform and
considered how your driving habits have played into your decision. If you
don't trust your mechanical skills at all, you can have a local outfit build
the engine for you. Just make sure you pick a quality shop to do the work. If
you have no fear of spinning wrenches, feel free to ask an expert for guidance
on how to best match and assemble the right parts for your needs. They usually
don't mind being used as a resource because they know that you will have to
have certain machine work (boring, milling, turning, etc.) done somewhere, and
if they are helpful, they just might get your business.
The
first step to building an engine is to select a camshaft that matches your
performance expectations. This one part more than any other will determine the
true nature of your new engine. Again, be realistic. If you try to put a full
race cam in, you will have to take extreme measures to take advantage of it,
by which time your will likely have exceeded the block's capabilities. Once
you have chosen the camshaft, you should build the rest of the engine around
that. This will affect what type and compression of pistons you use; how you
have the head milled and what type of valve springs you will use. It can
affect what kind of exhaust system you install and what type of ignition
products you buy. Based on the camshaft, you might choose to port and polish
the head and intake manifold. You may opt for a three or five angle valve job.
Of course, some of this may be a bit overboard, and if you choose a cam that
HAS to have all of this, you're probably being a bit aggressive. Again,
consider a conversion instead of going overboard.
I
was fortunate enough to have an engine designed for roller cams, which made
having a new profile ground onto the original cam a viable possibility. Roller
cams have far more success than standard tappet cams with longevity after
being reground. This was certainly a good thing because there were not many
aftermarket options for a new cam at the time. Kams, Inc. in Oklahoma City put
a mild RV profile on the cam that adequately matched my driving style. It was
certainly streetable; started easily even in winter; had a good mid-range
power curve and respectable fuel economy at highway speeds. From there, I
chose 9.5:1 compression pistons that would pull a little more power out of the
fuel without inducing too much stress on the weak cylinder walls.
I
had a great local outfit named Buddy Rice do all of the machine work on the
engine. They were the ones that helped me choose parts that would perform well
with the camshaft profile I had selected. The block and head were both
cleaned. Then, I had the centerline bore reestablished on both the camshaft
and crankshaft bores. They also trued up the bores on the connecting rods.
They milled the head and performed a 5-angle valve job, and then shimmed the
valve springs to match them with the camshaft. The crankshaft journals were
also turned, along with the mains that were 'recentered' to match the work
done on the block. They looked at the idea of balancing the crankshaft, but
ultimately decided against it because of its light weight and the fact that it
was already fairly well balanced. While the engine was still at the shop, we
carefully looked over all the parts for any signs of wear. Anything that
showed any significant wear was replaced. Better to catch the problem now that
to find it later after it fails.
With
the block and head prepped, I took all the parts home and started putting the
engine together. I didn't do anything special while assembling the engine. I
just made sure I was liberal with the engine assembly lube. I use this stuff
on everything, not just the camshaft. I also made sure that I followed the
torque specifications for everything; using several increments up to the final
torque for anything over 25 ft/lbs. When working on the engine or suspension,
I never tighten anything with an ordinary wrench. I always use a torque wrench
to make sure I am not overtorquing something. I also do this to make sure that
matching bolts on a part are torqued uniformly to prevent warping.
One
note of caution; whenever you are not working on the engine, make certain to
but a thick plastic trash bag over the engine and seal it airtight with tape.
When I first started the engine, I had no oil pressure at all. After taking it
back apart, I found that a wasp had built a mud nest in the oil pump that
completely blocked the passageway to the oil filter. Fortunately, the liberal
use of the assembly lube saved the engine from damage. The bag will also help
protect the engine from dust and humidity.
At
the time of this writing, this was the extent of the work done to the engine.
Notice that the only higher than stock performance parts are a mild camshaft
and slightly higher compression pistons. Everything else was just removing any
possible sources of resistance, and making sure that each part could do its
job in the best possible environment. The engine already performs extremely
well. As time permits, I will port and polish a spare head and intake manifold
from another engine. I will install them along with a new exhaust, headers,
Holley's Big Bore TBI and a good aftermarket coil.
Some
additional notes would be that I removed the restrictor plate underneath the
TBI in the intake manifold; I use a cooler thermostat and coolant fan switch;
and that I disconnected and capped the vacuum line to the EGR valve. If you
choose to do the same, make sure you reconnect the EGR for one day every month
and take the car for a long drive. That way, it will work when it is time to
get your inspection.
Something
else to keep in mind is that I personally would probably never go this far
with another Iron Duke. When I started, I did not know about the ease and tiny
cost of certain V6 conversions. Also, I was fortunate enough to have a rare
engine. This is a 2.5R engine, not the normal 2.5L. GM ran the numbers on it
and describes my engine as an '84 Fiero Second Design' engine. They swear it
is definitely for the '84 Fiero even though it has roller lifters, which the
'84s are not supposed to have. I'm certain this
plays
a part in the better performance, and in this case, makes the extra effort
worth it. I have a 4 banger that performs very close to many of the V6 Fieros,
yet retained the efficiency of the 4 cylinder and did not sacrifice
reliability or life in the process. I paid a whopping $200 for the car and
spent around $1,000 rebuilding the engine. As long as I take care of it, this
little baby will last forever.
D.
J. Draper
(2)
'84 2M4s
|
