Cadillac probably needs the DOHC engines.

Chevrolet should stick with what they got going good for them now. Lightweight, Effecient, Powerful OHV engines. I would like to see Direct Injection on the V8's before OHC. I think that would net a NICE power increase....

 

How do you figure? 505HP LS7 Corvettes get 26mpg hwy, no other 500HP car can do that. If fact Honda's 2.2L S2000 gets the same hwy mileage with about a 3rd the torque.

Impala SS = 28mpg, not bad for a full size sedan

 

Caddillac does need DOHC for two reasons. 1) It is more refined and smooth. This is great in a Lux car. I have a STS and when my gearhead friends drive it, they all agree that it makes scense.
2) In that higher end market, Technology makes a differance. Consumers care about valve numbers. We may not but, we care about power.

 

I think you're confusing technology with complication. There's nothing inherently technological about 4 valves or 2? Both sorts of heads are decades old. Note that Audi and Yamaha were using 5 valve heads, but have gone back to 4. Their new 4 valve engines are more techologically advanced than the old 5 valve heads.

I think the main advantage of the 4 valve DOHC is that you can more easily have a central sparkplug, and you can more easily have separate valve timing with VVT. They may be smoother too -- I don't know about that one.

 

What?? No way.. where did you get that number from?

 

Agree 100%.

If Cadillac are ever going to be considered BMW, Merc competition then they need to offer similar.

 

www.fueleconomy.gov

 

I am not confusing anything. I love my LS1 and building it has been easy. My N* is a much smoother engine drive one and you will understand. In Caddy’s market consumers care about the OHC. Like it or not it’s true.

 

Ya, many of the (rice/ euro buying) neighbors tell me, "it has pushrods." Ok, it does, and it is simple proven lower cost design. Oh, and 800 hp @ the flywheel.

Also, NHRA pro stock drag IC engines are @ 2.8hp/ ci. And thats with spring over valve design! Not pneumatic like F1. I love 2 valve design. (Blown 383ci Z28 2-valve design on a road suspension).

 

My point is that the LS1 is just as high tech as the Northstar.

 

Agreed. To consumers in Caddy's market, OHC is more high tech. Like I said, I own both. I like both.

 

IU guess the Vtec motor uses a certain cam timing for low RPM power and another set of timing for higher RPM power... VVT baby. But then if you design a OHV engine right w/ long skinny ports you will increase the velocity of the air at LOW RPM's.. =LSx

YEah, my LS1 gets on average 18-22mpg and it only has 34k miles on it. I've been clocking my gas mileage for months. I only see high MPG #'s on LONG sustained cruises in 6th gear turning about 1500-1700RPM... Best I got was 360 miles on 12 gallons. (once I hit OK, TX and NM, I didn't let my tank get below 1/2... Stations were few and FAR between)


I would like to see #'s for parisitic losses on OHV vs OHC... Not trying to argue, just for research purposes. We can have a civil debate about this if people keep their heads on right.

I think that the LSx platform IS a nicely effiecient engine as far as power production. I mean really. Look at the old iron L98 TPI 350 blocks that made maybe 300hp stock. THat was good for the day, but TODAY it's a brick unless we give it some lovin... ie: heads cam, tune, injectors, P+P intake and heads .... etc...Cripes, a stock 2002 LS1 Dyno'd 400hp in a recent issue of GMHTP that has LESS displacement than the L98...

The all aluminum LSx Platform IS hugely efficient. I think a lot has to do w/ the roller cam + lifters, roller fulcrum rockers, head and intake runner design... -Granted the LT1 has roller cam and lifters too, that engine is also ahead of the older TPI 350, 1992 special.... The DOHC has a lot more moving parts, and a major PITA to do a timing chain/belt, also a lot more can go wrong or break.

w/ all the above said..... then why did Ford engineer the 4.6L OHC to make as much power as the OHV 5.0 it replaced? ... I would be curious to see how a 346ci LS1 would act w/ just a DOHC setup. Nothing different except the modification of cam mounts, and plug relocation to the stock heads... ... or even the LS2 for that matter.

Anyone have #'s for the Northstar DOHC Vette engine? What year was that? 95? 96?

 

Cheap asshats, methinks IIRC a big part of the early mod motors anemic rating was in part due to a particularly crappy manifold. PI heads also helped in the all important low and mid-lift air flow areas. I dunno about the cams. However, the basic PI engine architecture if used with a better intake is good for 100 hp/liter (that is to say using ported heads, bumped compression, bigger cams, ect).

 

I think the HP rating on the L98's was around ~215 HP . Nowhere NEAR 300!! The LT1's were close to 300 HP, but that was with a MUCH IMPROVED intake over the L98's TPI.
Are you thinking of the LT5 that went into the ZR1 'Vettes? I believe they were "rated" at ~385 HP, but I'm not sure if it was over/under-rated, or by how much? Also, I'm pretty sure it was Lotus who designed/built the 32V heads for that motor.

I have a mag at home that did a head-to-head comparo of the ZR1 against an '01 (385 HP) Z06 ... the Z06 just squeaked past the ZR1, but not by much ... I don't know if that confirms the ~385 HP LT5 rating or what?

IMO, nobody has "proven" that DOHC is any better/more efficient than OHV, other than it may "appeal" more, because of the fancy title . I like that GM has stuck to their roots (more specifically, Chevrolet) and continues on building the SBC the way it's "meant to be" . I also like that they keep pumping more and more power out of it right from the factory!!

 

Lotus did help design the LT5. It is in no way, shape, or form ralated to the Northstar.