Still trying to imagine this.

 

I haven’t seen a pic of the engine bay of the C8.R yet but: https://www.motor1.com/news/375287/c...-engine-sound/
if there aren’t any legit pics of the DOHC flat plane out yet, there will be after this weekend.
P.S. IMSA Radio is broadcasting from Daytona now (its 12:30 pm 1/3/20 currently). Google IMSA radio and you’re in. I believe it is live.

 

I just a pic of the engine bay w what looked like an LT-2 valve cover, not one housing DOHC. I suppose they could do a FPC OHV motor.

 

They have been deliberately “blacking out” the window over engine bay of the C8.R.. if it was a pushrod engine, why would they need to do that? We will know for sure soon. I’m hoping tomorrow(1/4/20) with the running of the Roar.

 

I just found this pic. As you said it is definitely an OHV (not DOHC) engine. So why the erroneous articles claiming they were using a DOHC flat plane? No sense to using a flat plane in a pushrod engine. If they are using OHV, its almost certainly a cross plane.

 

This is 100% speculation on my part: it’s more logical for TC to sort out the car with the old proven push rod 5.5, then in a couple years (2022 model)when the Z06 comes out to swap the old mill for the new DOHC engine. Maybe even changing the name of the race car to Z06.R

 

race motors often go to a larger cam size to stiffen up the shaft when going to really high rpms with stiff spring pressures and high rpms
nascar and drag race motors starting doing this as the push rod motors hit 9k and up and needed really stout valve springs and stiff rockers and push rods to do it.
that's a big advantage of the dohc engines. Much smaller and lighter valves with lower spring pressures and 4 X the cam shafts to distribute that load
the lifter buckets on direct acting cams can be much larger than a conventional lifter
with more frequent over revs at the track, the valves can float and kiss the pistons. Cam twisting, pushrod flex and the springs losing pressure when they float the valves can lead to a bad day at the office.

Another "side benefit" is that DOHC heads are both wider and stiffer which can reduce head flex under high cyl pressures like high compression or turbo charging this leads to a much stiffer and more stable valve train with much less chance of failure

GM has used truck engines in the vette long enough and need to step up to the benefits of full variable cam timing. They had the tech long ago "on the drawing board" with the MY 95 LT5 that would have been great.

Cost, complexity, and the low C5 hood line put the lt5 out of biz long before it's time. I think we'll see a new race motor that has all the reliability of the former race engines, with a bit more power band for faster times.

But as you say, even the best can struggle when everything is new and unproven.

I'm amazed that the race cars wheezing through those tiny restrictor inlets can still make the power. Same thing with the NASCAR retrictor plate engines. When you see how small the holes are, it quite incredible they can make power.

 

https://www.thedrive.com/accelerator...lane-crank-v-8


That is not a GM article. I have gone to the official websites and neither Chevy, GM, or Corvette Racing says it is a flat plane crank. It merely states it is a 5.5 liter V8 that produces 500 hp and 480 lb/ft of torque. Does that sound like the specs of a high revving flat plane crank?

 

. The picture of the engine bay above clearly show its not DOHC heads. The horsepower and torque numbers are never a tell under IMSA BoP rules because any type engine can be intake constricted down to the mandated max hp. Years back the Viper ran the full 8 liter displacement but the engine was breathing through a straw. At that time I wondered why Dodge wouldn't have rather destroke or sleeved the engine down to under ~6 L instead but for whatever reason they preferred to nearly suffocate their full displacement mill. I never thought the engines ran very efficiently that way.

 

looks like a DOHC size valve cover to me. Green yellow arrow and yellow outline indicate the red valve cover. Look in the back thru the chassis holes can see the back lower portion of the wide red valve cover and see where the exhaust headers come from.

 

Look how big the dohc red valve cover is. yellow arrow and outline

 

Every DOHC I’ve ever seen have the spark plugs in the center of the cams (covers) and visible from the top. Not here.

 

There are only small areas of the red cam cover exposed, plugs or wires would be totally hidden in this picture.

 

Thx. I was confusing the CF intake for the cam covers. And of course there are no “plug wires”, just wiring harness for the coils.
I was looking at pics of the Blackwing to see if the cam covers are the same.

 

I finally see the DOHC VALVE cover. I guess I need new glasses. What I was looking at was part of the intake. Da.. reassessing the scale to the guys arm, it would have been a 2.0 L V8 max if that carbon cover was a valve cover. Haha.
We are back to TC having to sort out everything INCLUDING a new power plant. Oh boy... long season.

 

the new c8 is a racing fledgling and will take a while to get sorted. The team has put priority on durability which corvette has shown time again is what it take to go the distance
they will have their hands full with the new pooches and euro sleds out there that have many more laps of refinement. GM has some catching up to do.

The c8 made an encouraging debut testing out and although not the fastest, it's working well so far. Anyone have details?

 

The flat plane crank the way GM is doing it should be just fine it is also why the GM engine is a screamer sound like a Ferrari, Ford on the other hand in there Mustang changed the firing order to get more of a rumble sound and it is what causes problems in durability and ultimate horsepower. You cannot have both ways in a flat plane crank and if you are going to go flat plane do it like GM and Ferrari are not like what Ford attempted.

 

G8,

Would u please illustrate how u believe GM is doing the FPC vs the Ford FPC config?

 

In a traditional FPC engine, both banks fire like a traditional I4 cylinder. On either bank, if you take a snapshot of it running, you'd see the 2 outer pistons up when the 2 center pistons are down. The Ford 5.2L FPC engine has the pistons differently. If you look at either bank, take a snapshot and you'll see the pistons: up, down, up, down. This positioning will still lend it to breath on even pulses from bank to bank, but I believe Ford also used non-equal length headers which added to the rumbling. This piston layout was used because it changed the counter weights needed and resulting harmonics being better for them. When you have the engine in front of the driver, it transmits NVH differently than a mid engine design do to the chassis.

 

While I have no data on the GM FPC,
A Ferrari FPC is the same as a 4-banger:: up--down--down--up
The Ford FPC is like the Ferrari but cut at the center and one side flipped end to end:: up-down-up-down. This causes a "different" vibration pattern that apparently the Ford block was vulnerable to.