IS GM capable of making a small block DOHC

[Truck Norris]

Originally Posted by fielderLS3

Yeah, but the Corba R was kinda a unique example, and you're unlikely to see anything like that in a high volume, mainstream engine. In my experience, with cars normal people can actually drive, I've never driven a DOHC with a truly strong low end, that made as much torque as horsepower (at least not in NA form). But pretty much all of the OHV engines I've driven, and the ones still in production today, make either the same or more torque than horsepower.

It doesn't get any more mainstream then Americas best selling vehicle of all time. The 5.0L in the F-150 makes more torque then hp. 360hp@5,500 380tq@4,250. Would you like more examples?

[big hammer]

Originally Posted by Truck Norris

Ok, the 5.0L in the F-150 makes more torque the hp. 360hp@5,500 380tq@4,250.

[fielderLS3]

Originally Posted by Truck Norris

It doesn't get any more mainstream then Americas best selling vehicle of all time. The 5.0L in the F-150 makes more torque the hp. 360hp@5,500 380tq@4,250. Would you like more examples?

Alright, I'll give you that one. And I guess with a little more thinking, I can probably come up with another example or two as well (all trucks).

I guess my line of thinking was in cars, not trucks, and more specifically, I was thinking of most of the 6 cylinders on the road today, which all seem to be in the 300 hp range, some above, but all weak on torque. You're right that they could tune them more for torque than power, but unless you are buying a pickup, that's getting hard to find.

Ultimately, where I am coming from is to say that it is refreshing that someone (GM in this case) still puts some focus on torque as well as horsepower in their performance cars, in a world where most do not. If GM wants to stick with the pushrod V8s in the Camaro and Corvette, instead of trading displacement for revs as much of the rest of the performance car world does, that's just fine with me. It gives them a unique selling point.

[DGthe3]

Originally Posted by fielderLS3

Alright, I'll give you that one. And I guess with a little more thinking, I can probably come up with another example or two as well (all trucks).

I guess my line of thinking was in cars, not trucks, and more specifically, I was thinking of most of the 6 cylinders on the road today, which all seem to be in the 300 hp range, some above, but all weak on torque. You're right that they could tune them more for torque than power, but unless you are buying a pickup, that's getting hard to find.

Ultimately, where I am coming from is to say that it is refreshing that someone (GM in this case) still puts some focus on torque as well as horsepower in their performance cars, in a world where most do not. If GM wants to stick with the pushrod V8s in the Camaro and Corvette, instead of trading displacement for revs as much of the rest of the performance car world does, that's just fine with me. It gives them a unique selling point.

Since when is 250-280 ft-lbs of torque 'weak'? 10-15 years ago, the mighty supercharged 3800 was in that range. Most small V8s 10 to 20 years ago were in that range. And 30 years ago? Camaros & Mustangs wished they had that much torque on tap.

And before you say that they are high reving & peaky ... look at the actual power/torque curve of the LFX:


Look at that, practically a straight line from 2.4k through 7k, with a minor bump at 4800. Its making about 250 ft-lbs at 1600 rpm. Again, for perspective a 1984 Camaro managed 240 @ 2400 rpm (or 3200 if you got the high-output engine with 190 hp).

By pretty much any objective measure, these modern V6s are not torque weak. Yes, they make less torque than power but that doesn't mean they're weak on torque ... it just means that they are power-strong. About the only way to get them to make more torque than power is to cut the revs back and drop the power down by about 50 horses, giving you a 250 hp car making 270 ft-lbs. I don't know about you, but I'd rather have the extra 50 hp.

[demonspeed]

Is it worth doing because it's truly a better design, or is it worth doing because people have the perception that it's better? There is a reason they stick with OHV -- and a reason why OHV works so well. More complexity just for the sake of complexity does not mean it's "better."

Further, people act so haughty regarding how "old" OHV is, yet they forget Ford's had OHC in the Mustang for just as long as Chevy's had OHV in the Camaro. To be honest, I think the only people who get bent out of shape with the issue are those that don't understand it.

At the end of the day, it's which car is easier to work on, gets the best mileage, and does it fastest, quickest, and most efficient. If that's a OHV engine then so be it.

edit: Keep in mind that the LT5 isn't necessarily an engine "program" so much as it was a unique product. IIRC, it was still a gen I small block with some tweaks to adapt DOHC. It obviously lasted for only one specific trim for one specific vehicle.

The Northstar program, on the other hand, was GM's venture toward OHC V8 in mass produced form. Granted, the technology mostly stayed with Cadillac (Olds received the 4.0; Buick/Pontiac would receive an occasional 4.6), but again, there is a reason why they have shelved that program after it existed for two decades.

[Truck Norris]

Originally Posted by fielderLS3

And I guess with a little more thinking, I can probably come up with another example or two as well (all trucks).

A few seconds of thinking and a quick google search for verification netted me with a bunch of US spec DOHC BMW and MB V8's that produce just as much torque as horsepower. Then there's all those Ford Falcons in AU with high torque NA DOHC V8's, and the little 3.9L DOHC V8 in the Lincoln LS with 280hp@6,000 and 286tq@4,000. I can keep on going if you sill need more car examples?

This is all in good fun, right

[toesuf94]

This will blow your minds - do it yourself:

Exotic Heads
Pete Aardema specializes in what could be the ultimate dare to be different, street-driven head conversion: changing American domestic pushrod engines to overhead cam configurations. The two main approaches used by Aardema: for single overhead cam (SOHC) conversions, fabricating a custom cam box that bolts to the existing pushrod-type head; for dual overhead cam (DOHC) changeovers, bolting on a DOHC head from a foreign engine.

For a DOHC conversion, the idea is to adapt a head from an engine family that has similar cylinder bore spacing to the pushrod engine you're working on. A Nissan Infiniti V8 is close to a small-block Chevy; a six-cylinder Subaru, a 4.3L Chevy 90-degree V6; a V8 Porsche, a big-block Chevy. Scope out swap possibilities by comparing head gaskets from different engines. It helps if the head bolt patterns are similar, but don't be afraid to plug and redrill head bolt and coolant holes in the block. Aftermarket blocks (say, from Dart) can be ordered with an undrilled blank deck and the bore centers only roughed in. Cometic can make custom head gaskets to order.

How To Hot Rod Any Engine Paxton Airbox Assembly
Paxton offers a universal airbox assembly for carbs, as on this small-block Mopar kit. A n
Provisions must be made to supply oil to the new head and block off the old, now-unneeded passages. This may require lifter-bore plugs-either completely blank (fabricate external oil lines), drilled to supply necessary internal oil to the top end, or so modified to keep the bottom end alive.

Most modern DOHC mills are beltdriven. You can often adapt or modify the original drive pulleys with custom idlers and different-length belts, or use a Gilmore setup with cogged pulleys. ASP is one source for special pulleys. Custom cams are available for any application these days, although they may need to be made from billet steel. And yes, Aardema is willing to offer advice and assistance to those attempting similar conversions.



Read more: http://www.hotrod.com/techarticles/e...#ixzz2ZtXbW4DP

[SEVEN-OH JOE]

Originally Posted by Rapid Runner

We all know GM is kinda the king of pushrod small block V8 technology.. nuff said

But I would really love GM to do a performance OHC V8 while keeping the profile of a small block pushrod

GM did such a good job with it's Direct injected V6's, just imagine what a compact 5.7 DOHC would do.. though that might be heresy

thoughts

The two are mutually exclusive. Take the physical dimensions of the 6.2 OHV vs. the much shorter stroke 4.4 L Twin Turbo BMW V8 (as shown by GM when introducing the C7). Latching big W-I-D-E DOHC heads onto a V-configuration engine adds to its width.

It would be physically impossible, with matching stroke capabilities, to make a DOHC the same compact size as the LS/LT family of engines. As Ford has found out. That's why the 5.8 DOES NOT FIT the S550 engine bay.

How much wider is the GT 500 5.8 then the LSA/LS9? Considerable.

[Truck Norris]

Originally Posted by SEVEN-OH JOE

The two are mutually exclusive. Take the physical dimensions of the 6.2 OHV vs. the much shorter stroke 4.4 L Twin Turbo BMW V8 (as shown by GM when introducing the C7). Latching big W-I-D-E DOHC heads onto a V-configuration engine adds to its width.

It would be physically impossible, with matching stroke capabilities, to make a DOHC the same compact size as the LS/LT family of engines. As Ford has found out. That's why the 5.8 DOES NOT FIT the S550 engine bay.

How much wider is the GT 500 5.8 then the LSA/LS9? Considerable.

I do know that the DOHC LT-5 is the same with as a LSA and a lot shorter in length and height.



The PS reservoir sticks out more then the heads. No bluepints available but its 26" wide and 26-27" in height and length.

[Firefighter]

The LT-5 was a bad assed motor. It was down on TQ in comparison to it's HP though. IDK for some reason I like the numbers to be close.

I remember driving the early ZR1's they were bad but they did need to spin up a bit for the fun to really begin. It was hard to discern the difference between it and a LT1 car because the ZR1 had more TQ than the LT1.

The nice thing about the ZR1 was the way it just kept pulling in the top end.

[demonspeed]

As an FYI, I took a little look-see to compare GM's DOHC vs. Ford's DOHC (strictly power output, that is). I'm comparing only equivalence (not comparing a 4.6 to a 5.8). I cheated, though, and simply wiki'd it:

Naturally Aspirated:
GM 4.6 - 320hp/315tq (05-10 STS)
Ford 4.6 - 320hp/317tq (99/01 Cobra)
or 310hp/335tq ('04 Mach1 if you care more about torque)

Supercharged:
GM 4.4 - 469hp/439tq ('06-'09 STS-V)
Ford 4.6 - "390hp/390tq" (03/04 Cobra; parens because they are underrated).

What's my point? GM is (was?) certainly capable of competing head-to-head

[fielderLS3]

Originally Posted by DGthe3

By pretty much any objective measure, these modern V6s are not torque weak. Yes, they make less torque than power but that doesn't mean they're weak on torque ... it just means that they are power-strong. About the only way to get them to make more torque than power is to cut the revs back and drop the power down by about 50 horses, giving you a 250 hp car making 270 ft-lbs. I don't know about you, but I'd rather have the extra 50 hp.

You make plenty of very good points. But the point still remains that in the last several decades, engines have indeed gained a lot of power, they have not gained that much torque. The net result is any horsepower number that is advertised has to be taken with a grain of salt, because something similar with what happens to currency through inflation is happening to horsepower ratings.

Basically, today's 300 hp engines aren't as strong as a 300 hp engine from 10 years ago was. I'm not saying today's DOHC engines are necessarily weak in absolute terms, but 300hp and 325tq is simply not the same as 300hp and 275tq. Run a 5th gen V6 against a "less powerful" 05-10 4.6L Mustang and see what happens. Or, alternatively, ask yourself what you would rather have, the 5th gen's V6, or the 4th gen's LS1?

[Truck Norris]

Originally Posted by fielderLS3

You make plenty of very good points. But the point still remains that in the last several decades, engines have indeed gained a lot of power, they have not gained that much torque. The net result is any horsepower number that is advertised has to be taken with a grain of salt, because something similar with what happens to currency through inflation is happening to horsepower ratings.

Basically, today's 300 hp engines aren't as strong as a 300 hp engine from 10 years ago was. I'm not saying today's DOHC engines are necessarily weak in absolute terms, but 300hp and 325tq is simply not the same as 300hp and 275tq. Run a 5th gen V6 against a "less powerful" 05-10 4.6L Mustang and see what happens. Or, alternatively, ask yourself what you would rather have, the 5th gen's V6, or the 4th gen's LS1?

I see what you are getting at but you shouldn't generalize all engines.

Diesel engines in pick up trucks haven't gained near as much horsepower in relation to the massive torque gains they have received in the past decade (500tq in '03 to 850tq '13 with only about 50hp gain). Also import engines tend to feel just as strong as they did in years past. My buddies 2009 265hp WRX (not sti) feels like it has every bit of 265hp same goes for Nissan's V6's.

Modern day torque management is also to blame as the engineers want to protect the drivetrain from massive and instant toque applications which would inevitably lead to pre mature failures and warranty claims. Added weight and larger modern wheel and tire packages are also to blame.

[demonspeed]

Originally Posted by fielderLS3

Or, alternatively, ask yourself what you would rather have, the 5th gen's V6, or the 4th gen's LS1?

*disclaimer* I'm sure you're stating this in the context of power. I'm sure there are plenty of reasons -- drivetrain aside -- that V6 Camaro owners would choose the 5th over the 4th.

With that said, I like that there are some fools who think their "more powerful" 5th gen V6 can whoop on those "crappy" LS1 Camaros

Originally Posted by Truck Norris

I see what you are getting at but you shouldn't generalize all engines.

Diesel engines in pick up trucks haven't gained near as much horsepower in relation to the massive torque gains they have received in the past decade. Also import engines tend to feel just as strong as they did in years past. My buddies 2009 265hp WRX (not sti) feels like it has more then 265hp same goes for Nissan's V6's.

Modern day torque management is also to blame as the engineers want to protect the drivetrain from massive and instant toque applications which would inevitably lead to pre mature failures and warranty claims.

Another aspect that gets overlooked is gearing. One could build a weak engine but put it in front of an optimally built (ratio-wise) transmission/axle.