BTW The CTS-V race car run HR cams to 7900 in the LS1. The LS1 engine could do that easily with the right cams.

At a point it makes more sense to go SR because the durations would warrant it. Most 220-240 duration cam doesn't need to be a SR, 240+ could use it though.

As everyone has said, oiling the lifters, running the right spring pressure and having GOOD lifters is going to go far.

Bret

 

In my current LT1, Headers, Comp Extream cam 230 x 236 x112, comp (self aligning) 1.6 RR's, I pushed it to 7000 rpms at the track one night and the RR's had to be adjusted, one to the point that the car just limped home (home is 5 miles from the track).

The new motor (sitting on the engine stand) has all "Comp": Non Self aligning RR's with guide plates, Cam, Lifters, 7/16" studs, etc. Yes I will have to make maintenance adjustments but it is a drag car only. Expensive, you bet!!

 

Bret,
Have you seen actual specs on that engine? From what I read it was ~500 hp @ 7200rpm. Dry sump engine and a very well blueprinted hydro-roller.... 7200 seems reasonable.

Hey, you know what they say.

If you want to make a hydraulic rev... you just need to make it act like a solid.

If you have more info on the CTS-V Race engine I'd love to see it. Doesn't seem to be a whole lot of information out there on it... other than the fact that it's an "LS6". Big whoopty doo.

-Mindgame

 

September Car & Driver did a thing on SCCA World Challenge Grand Touring Cars, 3R Viper, 3R Racing Corvette, Champon Racing Audi RS 6 and GM Racing Cadillac CTS-V. C&D's Techical Director, Larry Webster says:

"The (CTS-V) V-8 engine has a number of significant changes over the stocker. The stroke has been shortened by 9.0 mm (.354 inches) and the bore increased by 6.2 mm (.244 inches). Displacement is 5.8 liters with the shorter stroke permitting more revs. At Sebring, the engine redlined at 7900 rpm, 1400 higher than stock. But after the car's dominating first outing, where Andy Pilgrim stormed through the field, the allowed revs were cut to 7000 rpm. For it's horsepower, (GM Racing's Dave) Spitzer would only say that it makes more than 500."

That makes the 99 mm x 92 mm LS6 street engine a 105.2 x 83 or 4.14 x 3.27 engine. Hmmm... the stroke approaches a Nextel Cup engine, and the bore is .015 over a 400 CID SBC, and about .040 less than a Cup engine. If average piston speed is directly proportional to stroke, the 7900 of the race engine is about the same as 7100 on a stocker. The new 7000 limit makes piston speed at 7K about the same as a stocker at 6400. Shoot, my 97 C5 A4 is shifting at 6300 now with 80K on the clock.

I like the idea that the pushrod engine had an rpm limit imposed, but the DOHC Audi didn't. Yeah, pushrods are dead.

My $.02

 

Good stuff! Thanks for that info Jon. I'll have to check that C&D out.

Hey, it looks like the makings of a nice endurance motor doesn't it? Could use a rod ~6.4" no problems. That puts the max piston speeds right where you said. Then consider that the pistons, pins and rods are probably quite a bit lighter than stock and that motor's not even working hard.

Is Katech building these motors or did they say?

-Mindgame

 

Good call.

http://www.katechengines.com/index.htm

 

Thats because they use advandced beehive shaped springs, which cutdown on harmonics, which is what really limits rpm potential.

 

Sure... that and weight. Anywhere you can reduce mass on the valve side of the valvetrain is a big plus. I don't know the "rules" for that class but I'm sure that if they could, they'd use titanium valves, retainers and the beehive springs to get that weight way down. If no titanium valves, then definitely a lightweight SS valve... hollow-stem etc..

You're right though, it's a whole system of parts that contribute to the reduction in harmonics and mass. The camshaft core plays in that too.

-Mindgame

 

Hollow camshafts like LS engines: what are the advantages?

Larger diameter bearings, and therefore the lobes can help also.

Is this the time/place to discuss why?

 

Good question. Let's let this one marinade another month.

For those whom I have offended with my tangency... I apologize. [exit stage left]

-Mindgame

 

tangency, as to go off the subject? IMO, discussing how valvetrain parts' mass, configuration, material, etc. relates well to the original question.

Perhaps folks skip right to a high spring pressure solid roller setup when they reach some target rpm where a HR "won't work". That's the brute force method; there's also the finesse method or elegant solution which involves lower mass, lower inertia, fewer harmonics valvetrain bits. I thought we might be going there in this thread.

So is NASCAR going to limit Cup engine rpm with a gear rule? Did/will they ban stuff like titanium pushrods, which are very costly to make. Imagine drilling a 2mm hole thru a solid 7-8 inch long ti bar to start making a pushrod. That's some expensive "tubing".

 

I've been told by pretty reliable sources that the gun-drilled LS series cams are to help kill harmonics.

The larger cam bearings allow huge area under the curve.

Would it be a bad idea to drill down the middle of a cam for a regular SBC? Both ends already have holes started. However, since those cams are a good bit smaller, I question the strength if drilled? And even then, what size hole would you use? Too many questions...

 

oh yeah, I noticed that Comp has hydraulic roller small journal SBC lobes with durations up to 262* These aren't full race ramps either. Obviously somebody must want these huge durations for them to make it.

lobe -- adv - .050 - .200 - lift - w1.5 - 1.52 - 1.6 - - 1.7
3152 - 329 - 262 - 172 - .360 - .540 - .547 - .576 - .612
3117 - 324 - 262 - 177 - .420 - .630 - .638 - .672 - .714

For large journal BBC lobes they go up to 278*

 

Keep it going...

 

Oh... well I misunderstood you when you said, "Is this the time or place for this discussion?".
Imagine that... a misunderstanding on a message board with a bunch of text flying around and no expressions to read! lol

I agree, I think the discussion has shifted in that direction. I wouldn't pin every theory in the world on the LSx examples though. Just one engine design in the big pot.

To a certain point I agree... but I don't think that's entirely the case. Guys have been building engines and trying stuff out for a long time now. Yep, people are always in awe when they hear of a hydraulic lifter going 7500rpm or better. What they don't understand, in terms of the 1st gen sbcs, is all the work that goes into making a lifter act-right at those revs. Guys aren't simply buying Comp's, Crane's, whoever's, anti-pump lifter and throwing it in the engine. They're modifying the things to get rid of the pump-up. Their modifying the lifters to act more like a solid. The funny thing about it is this.... these guys, in order to be competitive are shelling out big $$ for modified hydraulic lifters just because the class says it has to be "hydraulic". Drives the cost of building an engine up.... especially when you consider the fact that a solid lifter would do the job just fine and give the guys with a little less cash a better chance of winning races. As for spring pressures, they're limited to heavier valvetrain components, so it's not so uncommon to see one of these "hydraulic" lifters with 250# or better on the seat. Just the price of valvetrain control with heavy parts at high rpm.

The cams you listed (AdioSS), they fall into this category.

The LSx is just one engine though. It has better valvetrain geometry and less pushrod angularity than your typical sbc layout. And why not? GM obviously learned some things along the way.
So, what works on the LSx is not necessarily indicative of what's going to work on every other small block engine.
On other engines like BBC, you have the same problems. Pushrod angularity... and it's especially bad on the race type heads. I think guys gave up on trying to make a BBC rev with a hydraulic a looong time ago. Same goes for the sbc in regards to pushrod angularity. Not near as good as the LS1. WRT race heads... there's no way I could even consider using a hydraulic roller cam with my heads. They don't even make a lifter with the offset.... probably cause it wouldn't last.

If you can afford all the nice lightweight valves, springs, retainers and locks.... sure you can turn some revs with a hydraulic. You can even do it with less spring pressure. The weak link in the whole shabang is the lifter. Aint exactly a lightweight when compared to many solids, and there's still that pump-up problem you have to deal with.

Not sure solids are going away any time soon. More economical in the whole scheme of things.

-Mindgame