For most automotive enthusiasts, upgrading their OE factory cylinder heads to be more free-flowing are plenty adequate for their performance needs. Take a potent motor, like the high-revving LT4 from GM. Given the right mods and a select few aftermarket upgrades, its top end comes alive with renewed fortitude.
But to do so, one must relinquish said cylinder heads to a professional for modification. This is why many performance enthusiasts turn to Late Model Engines (LME) for assistance.
Here, decades of combustion engine knowledge and countless hours of R&D time meet. All in the hopes of getting those OE heads to produce as much power as possible and get the most out of a factory casting.
Led by none other than engineering mastermind Casey Snyder, LME’s team of self-proclaimed “cylinder head airflow gurus” have turned the business of modifying OE heads into an art form.
We recently spoke with Collin Thomas from LME to learn how the Houston, Texas-based motor modifier turns the virile LT4 V8 into an even more efficient (and effective) piece of machinery. What we discovered was nothing short of impressive…
Steps in the LME OE Head Upgrade Process
While there are a plethora of sub-tasks encased within each stage of the OE head porting and rebuild process, there are eleven essential stages to LME’s program that every OE cylinder head passes through.
From the initial cleaning and disassembly of the heads once received at the LME facility to the final cleaning and reassembly. The experts at LME adhere to the processes outlined in this article to ensure that every OE cylinder head receives the same level of treatment as a race-spec cylinder head.
Making the Machining Magic Happen, LME Style…
As for LME’s factory head porting program, machining is one of the many ways the company modifies OE heads. After each head goes through a CNC process, each cylinder head is cut for the optimal valve job and the best valve back cut.
After that, the valve job continues with a hand-blending method. This tedious process remains a mandatory step in each OE head job LME completes. This hand-blending technique guarantees that each valve seats properly into the chamber produced by the CNC machine.
How LME Rebuilds OE Heads
Machine work and clearancing complete, LME begins the assembly process. This is when the engine builder will set the spring height on OE heads, so that specific cam specs can be safely and effectively utilized.
And while the stock intake valves in OE LT4 heads are more than adequate for most performance applications, the valvetrain’s exhaust side requires some modification. Depending upon the application, LME will upgrade OE LT4 heads with stainless or Inconel exhaust valves. These are accompanied by upgraded valve guides, with C.H.E. Precision bronze guides being the preferred product.
These valve guides’ blended bronze alloy materials allow for a more predictable and consistent expansion rate, thus allowing tighter stem-to-guide clearances. LME explains that you can eliminate unwanted lateral valve movement by having a tighter valve-stem-to-guide clearance. Over time, this significantly reduces the amount of wear on guides, valve seats, and the faces of the valves as well.
Lastly, LME measures the combustion chamber and calibrates it to the customer’s specific application. This helps solidify optimum performance perks and eliminates any unpleasant installation surprises down the line.
Like LME race-spec engines, the OE cylinder head program benefits from extensive testing on the in-house dyno combined with flow bench testing and computer modeling software. These inspection procedures help determine the possible performance figures within every OE head.
It is worth noting that LME remains widely recognized (and applauded) for having one of the fastest turnaround times in the industry. This is especially true when it comes to porting factory cylinder heads.
From the moment your OE heads arrive at their factory, you can rest assured knowing that they will be shipped back no more than two weeks later. This work is usually accomplished in as little as 3-5 business days. The only exception is if a particular part required for the rebuild is unavailable or compromised in some way.
Fortunately, LME keeps a large inventory of valvetrain components for all of the OE heads it rebuilds on hand. So extended turnaround times remain exceedingly rare. This is the dedication we like to see in an aftermarket automotive machining specialist.