Blindsey
15+ Year Contributor
- 243
- 1
- Sep 17, 2007
-
Holladay,
Utah
There is usually clearancing required for running any aftermarket rod in a stroker application -- it isn't terrible, but you do need to take it into account. Groden's and other aluminum rods are much beefier in size and need additional clearancing and oil pan denting. That is part of the game we play.
As for my motor, I wouldn't say that it is the "norm", as I am one of few that has tried, and my motor has lasted for over 3 race seasons with continuous abuse.
Trust what you want, but you will need to man up and just try what you think is a good combination and either prove it to be good or bad based on your own experiences and tuning.
Either way, in my application, I have had very good luck with the Eagle/Ross combo for several reasons -- the first key reasons was alot of research, proper engine building, and a major amount of detail for every aspect of my setup.
The second key reasons for the Eagle rod in the 7-bolt motor is the fact that they are one of the lightest steel rods on the market for a 7-bolt, and the H-beam design is decent for the high amounts of side load and compression load while its weight reduces the inertial load that is seen with the 1.5 rod ratio of the 2.3L stroker (stock length rods with a stroker piston and a 4G64 2.4L 100mm-stroke crank). Using the strongest and lightest H-beam rod would be the key thing to look at when using a steel rod in a stroker.
Unfortunately a negative side affect of using a steel rod in the 1.5-rod ratio engine is that there is a much higher level of side load friction being put on the rod bearings, causing them to wear out quicker due to high boost and high rpms (it will literally flake off the bearing surface) when being compared to an aluminum rod stroker, and especially when being compared to different rod-ratios (2.0L, 2.1L, 2.2L, 2.4L). The positive alternative is to use an aluminum rod to "cushion" the rod bearing, and the end result is less bearing wear than the steel rod over the same amount of abuse. The key thing is to find a strong rod that is light to reduce rotational inertia and reduce side load friction while retaining its physical structure without deformation or failure under your power levels, load and rpms.
There are ways to help your bearings in this case though when you are using any type of rod -- using a cryo-treated and coated bearing will increase its longevity while reducing thermal friction that could cause accelerated bearing wear or failure. As well, using a set of rods that are perfectly balance matched will reduce harmonics on a 1.5-rod ratio motor, resulting in increased bearing life (main and rod). For example, a 5-gram imbalance in rod weight will result in a 50-pound harmonic imbalance at 8000rpms on a 1.5-rod ratio motor using a 7-bolt Eagle rod. Balance is key, and 2.3L strokers with a 1.5-rod ratio are very picky when it comes to balance. Your bearings will like you alot more if your assembly is perfectly balanced.
As for pistons, you want to use a material that can handle high piston acceleration (due to the longer stroke and the low rod ratio) and thermal loading due to side loading. A more forgiving material is going to be better than a "stronger", more brittle material. Either way, the lighter the piston is, the less rotational inertia and load it will produce. So you are looking for the strongest, lightest, and most forgiving piston -- sounds like a fun one -- good luck. Usually you need to find a compromise as most of us purchase off-the-shelf pistons. The key materials used in pistons these days are 4032 and 2618 aluminum. Forged pistons are a must for their strength and durability. Ross pistons (312g in 7-bolt stroker application) for example, are made from 2618 aluminum which has a low silica content, but has a higher density and is more elastic than the 4032 high-silica, low-elasticity aluminum that Mahle uses in their lighter-weight pistons (250g in a 7-bolt stroker application). The positive side to using 2618 aluminum is that it is much more forgiving due to its low silica content, and higher density causing it to handle more detonation or thermal shock much better than the high silica 4032 aluminum. The high silica, lower-density 4032 has a tendency to crack, shatter or in other words, fail under the same abuse that the 2618 aluminum may be able to handle it without damage or failure. The downfall of 2618 aluminum is its expansion, so it is more likely to have piston slap due to its change in size due to thermal expansion -- you need to have a more forgiving piston-to-wall clearance and ring gap size than its 4032 counterpart that can handle much tighter tolerances without significant thermal expansion. Piston slap is already a much more likely issue when running either piston due to the increased rod angle from the lower rod ratio, so that must be taken into consideration when putting together a street motor that needs to last, or a race motor that is going to be refreshed very regularly. When using a race motor, close piston-to-wall clearance is wanted to increase efficiency, a lighter piston is wanted for reduced inertia, and a stronger (but more brittle) piston is wanted for handling higher power levels -- 4032 is the way to go. When using a street motor, you want a piston that can handle more abuse, be more forgiving, and this comes only at the cost of thermal expansion and its weight. The 2618 aluminum piston will be a better application for street use and longevity while being able to handle a less-than-perfect tune.
Thermal and anti-friction coatings are also going to help in the performance and reliability of either piston. In the fact of the thermally more expansive, but more forgiving 2618 aluminum, it will help in reducing side load friction and temperatures, resulting in a piston that is likely going to be able handle more abuse, hotspots, friction and detonation than the same piston without coatings. These coatings are a way to cheat the system of having to compromise between two aluminum types by bringing the strength and increased thermal characteristics of the 4032 aluminum to the party with the durability of the 2618 aluminum. Cryo-treating is also another excellent resource as you can strengthen the piston through molecular refinement, resulting in better wear characteristics and longevity.
So....In conclusion...
***If I went with a steel rod/aluminum piston setup in a 2.3L stroker, I would reccomend a lightweight H-beam rod (Eagle and R & R) that can handle the power, and a 2618 aluminum piston (Ross for example) that has anti-friction and thermal coatings. I would reccomend cryotreating for both rods and pistons, and I would use a cryo-treated tri-metal bearing or a cryo-treated coated ACL bearing that is properly sized for your application.
***If I went with an aluminum rod/aluminum piston setup in a 2.3L stroker, I would reccomend a capable aluminum rod (R & R or Groden or MGP) that can handle the power, and a 2618 aluminum piston (Ross for example) with the same thermal coatings and cryotreating done to it.
***If I wanted to build the craziest RACE motor that has a sole purpose of crushing my competitors, and would require more regular tear-downs and maintenence, I would go with an aluminum rod and a set of the lightest weight high-silica pistons that are coated and cryotreated with a coated bearing, and a darn good professional tune. I would look at R & R and Groden rods, along with a set of Mahle pistons. Killer setup with the lightest components and the lowest inertia of the combinations currently available.
*I would also couple any of these applications with a 7.25" twin-disk clutch or a 5.5" triple disk clutch to reduce rotational inertia, and balance the entire assembly (including clutch and flywheel to PERFECTION).
*Other little ways to increase the longevity of a stroker motor is to keep the RPMS and powerband usable (4000-8500rpms), and keep it below 8400rpms on a steel rod setup. As well, using a high-cushioning oil will help -- 20W50 is a good way to do this.
Anything else???
For now, I will shut up and I will let you decide.
Fantastic post! I just started my stroker build and decided to go with Arias pistons and Eagle rods.
