HPR and GSpeed team up on a 468 cid road race setup
 

-Build Thread-


HPR and GSpeed have teamed up to showcase a number of new cool and exciting engine and power-train offerings for late model Corvette's, particularly for road racers. In this continuing build thread you will see maybe some things you haven't thought of before, but all are either currently available or so to be available products you can have for your own racer or street car.

There has been a common urban myth surrounding the world of road racing, and that has been to have a higher reving engine you need a shorter stroke. You can find this from the history pages of the Chevy 302 back in the early TransAm days of racing right up to the new destroked LS7 builds that have been growing in popularity. Some of these engines were due to rule limitations like the TransAm series but others were done just because that is what was thought to be the only way to do it. What did it really prove? It takes a lot more RPM to make the same amount of HP from a smaller engine, and low to mid range torque suffers because of it.

Since most of us on here are not racing in a class that has a displacement rule, why handicap yourself right out of the gate by using a smaller engine? I know the love affair with a 8500 RPM V8 is one that we all love to hear blasting down the straights but what if I told you you can make so much power across the board there is no point in doing so? What if I also said, if you need to spin it that high and can feed it....there is no reason a big stroke LS engine can't spin to 8000 RPM or more? :D (more on that later).


Goals: To build a reliable and cost effective LS performance engine package without using exotic or high maintenance components.

Highlights: New and innovative products

Outline:

• 468 cid LS standard deck aluminum engine
• lightweight accessory drive system
• using "shelf" components
• pump gas for fuel

Episode 1

Short block.



In our talks with Louis the goal on this first engine was to make a big powered engine obtainable to most weekend racers or street cars. No high dollar shaft mount rocker arms. No solid roller cams that would need constant adjustment. No limited production billet cranks or high dollar connecting rods. The best starting point, our signature 468 cid LS of course.



Ground zero is the engine block itself. We use a Darton dry sleeved Gen IV LS engine block as our starting point. In this case it is the typical 5.3L casting. Inside we do use a longer than stock sleeve to better support the increased stroke of the 468. Stock GM main caps are supported with ARP studs and hardware.



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Sleeved block



From here we clearance the block to clear our connecting rods for the increased stroke with minimal intrusion into the liners. New cam bearings are installed, main caps are torqued and line honed for proper clearance for the mains. Cylinders are honed to our finish requirements and the deck surface milled to spec. Once machine work is finished, the engine is washed and ready for assembly.



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Checking Mains



The forged crankshaft is measured for journal sizes and prepped for balancing after weighting all components used.



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Balancing the crankshaft



Pistons and rods are honed for proper pin clearance then deburred and washed.



The 468 uses a number of components of our own Erik Koenig's design like the pistons and ring package for not only a good seal but reduced drag and friction which again aids in horsepower! Here you can see the rings being sized for gap prior to going on the pistons.



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Checking rings



Once the rods are washed, bolts are lubed and bearings installed prior to hanging the pistons. Another one of Erik's designs was a strong, yet light rod that provided more clearance for the large stroke on our 468.



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Connecting rod detail



With the rotating assembly balanced, parts fitted and washed it is time to assemble.



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Caps going on



First step is installing bearings into the block and laying the crank in place. Here we can check final rotating drag and trust movement before installing the piston/rod combo.



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Pistons going in



Correctly sized ARP ring compressors are used to install each assembly into the engine block using Motul break in oil.



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assembled short block



Once the short block has been assembled we can go in and check our work for deck height at each corner and prepare to install the cam and timing sets coming up in the next installment!



Sneak Peak -


This is one of the brand new items that you will also see featured on this engine build. Louis and the team at GSpeed have developed a completely new front accessory drive for the Corvette. In short, this system has removed 30 lbs of weight off the nose of the car, which is always a big plus. What else is this going to do? It is going to give you a better water pump for increased cooling. A real road race power steering pump setup. Smaller and lighter pulley system, and narrowed belts for less frictional drag. In end not only will it remove weight but you are going to see increased RWHP and quicker acceleration.


I'll let GSpeed go into more details on this one.

https://cimg7.ibsrv.net/gimg/www.cor...cba0a63160.jpg
C5/6 Corvette accessory drive system from GSpeed





STAY TUNED!

Sub'd

Sub'd interested in this accessory drive setup.

We do plan on offering it to completed engine here through our shop. GSpeed maybe selling it as a kit, but I would suggest contacting them for details on that.

Looks like a Jones racing products accessory setup? Have one on my Gen 1 (actually a RCR which is NLA through Chevy)
if it is hope you dont mind a positive plug..they are a true super lightweight underdrive system they weigh nothing seems like and bearings dont come apart at high rpm. If I have the brand wrong please disregard

Keep the build details coming.

Sub'd.

Very, very happy to see continued development/improvement/innovation on motors for our cars designed specifically for road course and road racing. It gets old after a while seeing build after build that goes for nothing but peak hp at some arbitrarily high RPM with little regard to a proper torque curve or power generated under the desired RPM band. I personally have no interest in racing dyno charts or blasting straight lines up the entrance to a freeway and proclaiming victory.

This is EXACTLY the kind of thing I am interested in and I almost wish my LS7 would blow itself up so I would have a reason to give my wife for buying this. The new front accessory drive system is fantastic. And the ability to improve the water pump, power steering system and a lighter pulley system is golden.

I will be down running with NASA at WGI for 3 days starting on Friday for their Thunder at the Glen and I almost hope I blow something up so I can start scheming on this. There are a ton of Vette guys that I know at the track that would be interested in this.

I'm in. :lurk:

I'll have Louis chime in for the details but I can tell you that no, none of those parts were shelf items other than the pullies themselves.

Now, there have been products like Jones racing, and CV product accessory drives for a long time now for the traditional SBC and the SB2, SB2.2...just due to the huge demand for systems like this in NASCAR and the supporting series. For an LS engine fitting within the confines of a Corvette...not so much.

The only part that is used from Jones is the alternator. Nothing else lines up, fits, or bolts on. Every part is modified in some form or fashion to fit on the car. Its a nice setup. We gained 35 rwhp on the last car, from the accessory drive in conjunction with a 5 stage drysump, from a Serpentine OEM drive, and a 3 stage drysump.

Apples to oranges? Nope. Good power for restrictor plate rule book racing? Yep!

We have a few more drives going together on cars here, and hope to do a back to back test.

Keep in mind, this isnt really geared towards street cars. Its mostly for race and track only cars. The small alternator can keep up with race car demands, but not that of low rpm, idling street cars.

Moving forward.


In sticking with our target of building a reliable big displacement road race engine while using currently available shelf parts without going to crazy on our budget. We are sticking with a hydraulic roller camshaft and OE rocker arms and using current on the market head.

A lot of thought and planning had to be done when it came to the camshaft design. Unlike a drag engine that sees only seconds at WOT, this engine is going to see up to 40 mins at a time on track. Louis at GSpeed, Mr. Godbold at Comp Cams, and ourselves spent a good amount of time working together on choosing the correct pieces to fit within our design and budget layout. More on this later.


First off the easy stuff.
Lifters. In keeping with a 'shelf' part and affordable hyd. roller build we are choosing to use the GM COPO spec lifters made by Johnson. These are the same ones you will find in the 8000RPM factory COPO drag cars and retain the OEM lifter buckets and stock lifter dimensions. Erik has used and tested these in the past, and when used with the proper supporting hardware, prove to be a very solid lifter design.
Some of the highlights of these lifters include:

• Heat treated forged steel body
• high flow disc style check valve for better reaction at high RPM
• improved internal oil metering to supply rocker arms and valve springs without loss in oil pressure
• needle roller bearing with high chrome steel axle
• controlled slow leak down piston

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COPO lifters oiled and ready for install












Cylinder heads
GSpeed and ourselves when over a number of head designs and options out there from LS3 to LS7 style versions. For the purpose of having a solid power band through as much of the RPM range as we could, we settled in on a set of Mamo Motorsports reworked Trick Flow 260 LS7 head.



Louis at GSpeed spec'd these out with a lightweight 73 gram Titanium intake valve and equally light 85 gram stainless exhaust valve. Tony Mamo did his thing on the ports and chambers for what should be a very well flowing cylinder head (flow numbers not available at time of this writing - updated when I have them).


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MMS 265 LS7 reworked TF260's
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Trick Flow 260 LS7 casting
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Tear down for measurements
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chamber with valves installed
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chamber with valves removed
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intake port




Now the camshaft. Mr. Billy Godbold, the mad scientist at Comp Cams, is probably the leading authority when it comes to actual cam designs and testing valve train systems. Because we are working with an engine designed for lengthy run times on track. A very soft and stable ramp profile of Billy's was chosen along with a new finish of his own working as well on the camshaft. Just shown for the first time at SEMA this year, you will be seeing this much more in the future from Comp Cams.

"We changed our grinding wheels and dress parameters to maximize the load distribution and then wanted a light treatment just to take the fuzz off the top of the topography (like running a finishing mower across a baseball or soccer field). Many of the treatments left a dull finish, but the best one we tested included the burnishing fluid and denser media that also resulted in that more mirror like look. I just don’t want anyone to think it was supposed to be so good looking, but the best finish we developed just had that as a side effect." - Billy Godbold


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COPO lifters, GM lifter trays, 4 pole cam gear, C5R timing chain, Comp Cam, and hardware

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Close up of the new finish on the cam

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Sliding the cam into the 468 lubed with plenty of Motul break in oil


NOTE: Like any doctor we do respect the privacy of our customers so the actual cam specs are not disclosed publicly or to other customers unless GSpeed would like to post them.


For valve springs and rocker arms. Using Billy's own data along with specs from the rest of the build we decided to use a new Comp single spring the 7230 conical. Billy has been using these in his own enduro LS running 8-12 hr races without issue. These will be finished off with a Tool Steel retainer for life, and since they are so small, there is no weight penalty compared to a larger dual spring Ti retainer.

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Comp 7230 spring and Tool Steel Retainer


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The master himself, our own Erik Koenig checking cam timing.








Stay tuned as we finish out assembly and completion of the long block coming up!!!

Are the roller lifters there the limited travel style lifters. I thought I read on the COPO motor they shim them up so very little plunger travel.

They are a slow leak down but std travel lifter, that being said always measure travel when you are setting them up and checking for pushrod length (in an upcoming thread update), and you can adjust how much pre-load you have in the lifter based on length of course too.

You can use OE Rockers with Mamo heads?

BTW...this all looks bada$$

Trick Flow does offer rails to use the OEM rockers. I know Tony has worked with YellaTerra to develop a roller rocker and of course there is Crower Steel shaft mounted arms as well. So you have a number of options. Again being this was designed to work as a more budget friendly option we agreed with GSpeed to use a OEM style rocker arm and hyd. roller cam vs going aftermarket arms or solid roller and a shaft mount system, which of course would be the better way to go but adds to the budget.

This does of course limit valve lift on the cam to approx 0.650" lift.


So yes....do keep the design idea in your head when looking at it. Since most of us can not do the big magazine style, budget be damned builds, this I think fits more in line to what most of your sunny day to work, weekend track builds will be like.

No issue using Ti on the standard seats that come with those heads? Or are the valved coated / treated?

Very interested in hearing more about the Conical springs. I've been a bit gun-shy to use them, due to lack of positive reports. I love the design and concept though.

What length rods are you using with this stroker?

Regarding those conical springs.
I have used them in my cam only ls6 346ci build and recommended them all the time.
We spun that SBE ls6 to 7700 rpms on several occasions and routinely shifted that setup @7200+.
On the logs from the track and the dyno we say no issues. I'm confident they perform well at high rpm within reason with frequent checks and preventative maintenance.
They make 2 or 3 different sizes.

OP: Nice stuff and to have Erik leading the charge is awesome.

Valves are coated, I don't know why anyone would want to run a Ti valve that isn't coated.

We were a bit shy on the conical springs as well, but having Billy endorse them as well knowing fully what the engine will do and see says a lot.


As for the rods, some details on the 468's we don't release publicly.

Thank you for the info. I really wanted to give them a try a few months ago for my personal car, but there was simply too many mixed reports.

There is more than one type of coating..... Not sure what I said to inspire the curt response.

My primary concern was the TF seat alloy and compatibility with Ti. I thought they were just ductile iron? Unless I'm mistaken, that isn't the best alloy for Ti, and why I have been hesitant to use a Ti valve with them (and why I do not have a set).

On the rods, I'm just curious what the rod angle is and how that might play into liner longevity.

My apologies for asking questions. Good luck with your future endeavors and the new business.

I didn't mean to come across as short, just hit a quick reply before grabbing lunch. If I came across that way, I sincerely did not mean to.