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OHC vs. Pushrods: The Domestic V8 Myth Exposed


The popular automotive press has long had a bias toward overhead-cam powerplants. Much like the effect of the liberal media on mainstream America, the “informed” auto-buying public has generally accepted the supposed supremacy of OHC engines over their pushrod contemporaries.

This perception has transcended the old “import vs. domestic” quandary and morphed into a GM Gen III vs. Ford Mod motor argument. The battles are fought on message boards like this one and others, where members make compelling arguments for both sides. The basics of these debates are pretty simple:

Post #: The motor in the Mustang GT sucks because it doesn’t make as much power as an LS1-equipped f-body.

Reply: Well, your LS1 has over 60 cubic inches on it. It ought to make more power! We make more HP/liter!

Reply to reply: That may be true, but you have more cams and valves and need to put a blower on your valver to almost make the power of an LS6…


And the battle goes on.

After seeing this play out over and over in different places, I wanted to get beyond the rhetoric and into some hard facts. What I found was somewhat surprising, given this seemingly apples-to-oranges comparison.

Ford’s ubiquitous truck and pony car engine is the 2-valve 4.6 liter engine. In current tune, this motor makes a rated 260 HP @ 5250 RPM and 302 lb-ft @ 4000 RPM. This engine gives up approximately 65 cubic inches to an LS1, and anywhere from 45 to 90 HP, depending on the vehicle in which it’s installed. Doesn’t seem like a real fair comparison, does it? Well, the closest thing to a 4.6 LS1 would be a Gen III Vortec 4800 truck motor...4.8 liters, or roughly 292 cubic inches. Here's how it compares to the Ford Mod OHC offerings (Cobra not included for obvious reasons!):

GM Vortec 4800 (4.8L): 285 HP @ 5600 RPM 295 lb-ft @ 4000 RPM
Ford SOHC 4.6 (GT): 260 HP @ 5250 RPM 302 lb-ft @ 4000 RPM
Ford DOHC 4.6 (MACH 1) 305 HP @ 5800 RPM 320 lb-ft @ 4200 RPM

So, from a strictly power standpoint, the Gen III motor is every bit the equal, and in fact surpasses the 2V 4.6. Obviously, the extra 11 cubic inches the Gen III has can’t possibly account for the 25 HP advantage it maintains over the OHC Ford. As basis for further comparison, I included the DOHC 4V MACH 1 motor. The pushrod 4.8 engine is actually closer in HP to the 4V Ford MACH, than it is the 2V version.

Take a step up in displacement, and you get an even more interesting comparison:

Ford 5.4 liter 3V: 300 HP @ 5000 RPM 365 lb-ft @ 3750 RPM
GM Vortec 5300 (5.3L): 300 HP @ 5300 RPM 330 lb-ft @ 4000 RPM

The displacement and horsepower figures are nearly identical. What makes this so intriguing is the fact that the Ford has one extra intake valve per cylinder. The 9.5% torque advantage was most likely a tradeoff the Ford engineers made, since this is (until 2005) primarily a truck engine. Still, it’s quite interesting that an “old-tech” pushrod motor can match the HP output of a multi-valve OHC motor of the same displacement.

Instead of discussing all the remaining variations of these engines, lets go straight to the top:

2003-04 Cobra 4V 4.6, Supercharged: 390 HP @ 6,000 RPM and 390 lb.-ft. @ 3,500 RPM
2002-04 LS6 5.7 L: 405 HP @ 6000 RPM and 400 lb-ft. @ 4,800 RPM

At a glance, we’re back to that 65 cubic inch advantage discussed above. What throws a wrench (no pun intended) into this equation is the positive displacement supercharger sitting atop the Ford engine. Despite that distinct advantage AND 4 valve, DOHC cylinder heads, the Ford engine doesn’t quite make up the difference in HP or torque of the top-of-the line, normally aspirated Gen III GM offering.


Through this exercise, we’ve proven two points: First, at any given displacement, the GM Gen III V8s are the equal and, in some cases, superior to a 2V Ford V8. Second, adding valves and cams doesn’t always equate to distinct power advantage. While some of the mod motors offer a higher specific output than a similar Gen III motor, they don’t enjoy overwhelming superiority.

Of course, these facts apply to engines in stock trim. Anyone can argue that, by adding modifications, one engine will make more power than another, which is obvious. Ultimate power output of a given design is a debate for another time.

Of course, as technology moves on, and the figures above may be obsolete in small number of months, as both sides upgrade their arsenals. What I am attempting to demonstrate here, is the fact that the pushrod engine is and will be a viable configuration in both the performance and truck arenas. Their relative simplicity and low cost, when compared to OHC designs, will allow GM to compete, possibly at an advantage, in segments (Vette, GTO, trucks, etc) where performance per dollar is the key to market share.

No one will question the value and common sense of the small-displacement multi-cam, multi-valve 4 or 6 cylinder engine. In terms of power, economy and smoothness, the OHC configuration is superior. But when it comes to making gobs of cheap V8 power, the “old skool” pushrod V8 will always reign.
 

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That was kind of interesting but----GM pushrod engines almost always better their competitors fuel mileage, as well. You seem obsessed with comparing displacement to displacement. That is completely arbitrary and very flawed. Why not compare engines that weigh the same? Engines with the same exterior dimensions? Engines with the same fuel economy? Engines that cost the same amount? It makes much more sense to compare engines along those lines that simple displacement, and comparing things that way makes OHV look far and away superior.

Ugh, I just hate comparing displacements, it's so meaningless.
 

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Discussion Starter #5
Originally posted by banzai79@Apr 16 2004, 10:59 PM
That was kind of interesting but----GM pushrod engines almost always better their competitors fuel mileage, as well. You seem obsessed with comparing displacement to displacement. That is completely arbitrary and very flawed. Why not compare engines that weigh the same? Engines with the same exterior dimensions? Engines with the same fuel economy? Engines that cost the same amount? It makes much more sense to compare engines along those lines that simple displacement, and comparing things that way makes OHV look far and away superior.

Ugh, I just hate comparing displacements, it's so meaningless.
Displacement is meaningless? Wow. I'd really like to hear what yardstick you would use to compare relative output. I could've compared an Ecotec to an LS1, but that would not be a very compelling read, would it?

As far as mileage and emissions are concerned, I did intend to mention to compare the two designs, but the story would've been much longer. So I figured I would save that for another day.
 

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Originally posted by Canuck@Apr 16 2004, 10:57 PM
Nice read.
You never even mentioned pushrods are cheaper to fix
Thanks!

I didn't even need to get into the ease of repair due to simplicity! I was saving that as a backup in case a debate erupts.
 

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Car and Driver would complain pushrods are old and therefor not as good. What a great rational reason for DOHC to be better.
So where do we fit in Varible valves to this debate?
Emissions?
Fuel economy?
Grade of fuel? (Reg, Mid grade, Premium)?
 

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Originally posted by Canuck@Apr 16 2004, 11:36 PM
Car and Driver would complain pushrods are old and therefor not as good. What a great rational reason for DOHC to be better.
So where do we fit in Varible valves to this debate?
Emissions?
Fuel economy?
Grade of fuel? (Reg, Mid grade, Premium)?
Actually there is an article in C&D that praises the pushrod simplicity and is an interesting read.
See C&D May issue pg 34. "The Pushrod engine finally gets its due"
 

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I have read said C&D aritcle, and I had to check the cover several times to make sure that it was still C&D. On another note, does anyone else hate the new look of the aricles? They look like they are put together by a high school newspaper. Small pictures, titles is bold font, nothing more really.

On top of all this, is the cost and size. There is a OHV vs OHC thread up top in the news room. In there, they say that on average, there is a $800 cost savings from putting in a OHV engine, not to mention the added weight and size of the engine, which changes the way a truck or car is designed.

GM is doing fine making these old engines outperform modern ones. GM saves money, has better fuel economy, and saves weight and space to make a smaller, lighter, cheaper to run, cheaper to buy car, and be able to compare it to the best the world has to offer.

Just look at the GTO vs CLK55 in this months MT. The GTO is 1/2 the price and offers near the same performance against a AMG Performance model from MB.
 

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a 5.3 gm engine is roughly 327 cid the 5.4 ford 3v engine is roughly 351 cid so the 5.4 should produce more power due to its cid advantage
 

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a 5.3 gm engine is roughly 327 cid the 5.4 ford 3v engine is roughly 351 cid so the 5.4 should produce more power due to its cid advantage
the 351" Windsor" is a 5.8L pushrod engine and was replaced by the 5.4L "modular"


I believe a "LOT" of the OHC is better came from 4 cyl engines and OHC's LOVE of revving compared to torque tuned push rod engines +
as NEWER engines came out they were OHC and more powerful compared to their OLDER model

IE the VY COMMIE using the Supercharged 3.8L push rod and VZ using the "high feature" DOHC 3.6L NON supercharged and making MORE power

but even the SBC benefited from the generation change from GEN II to GEN III came with a LOT of power
 

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Nice article, but it drops the ball when it omits vtec,
the most powerful engine technology ever invented.
 

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Nice article, but it drops the ball when it omits vtec,
the most powerful engine technology ever invented.
The original article is from 2004. Variable valve timing is ubiquitous now. Even pushrod engines from GM and FCA (the last holdouts still using the OHV configuration for production car and light trucks engines) have this technology.
 
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12 years TO THE DAY!? (4/17/2004 TO 4/17/2016) - This might be a new record?
Where's Big Al been? He's been AWOL since Nov. 7.
 

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. Even pushrod engines from GM and FCA (the last holdouts still using the OHV configuration for production car and light trucks engines).
Yes but Why? Why are they the last hold outs? Packaging, Efficiency, Costs? Why when all of their other engines have switched to OHC design? I say cost over benefits. But even Ford's last hold on the Flat Head eventually had to be let go of for change.

The benefits of Direct Valve action will out way the Push Rod, once Chain Stretch is a thing of the past. ie. Valve Actuators.
 

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Where's Big Al been? He's been AWOL since Nov. 7.
Rumor has it, he got one of dem-dare real jobs; that you have to show up on time to, the good news they pay you.


Yes but Why? Why are they the last hold outs? Packaging, Efficiency, Costs? Why when all of their other engines have switched to OHC design? I say cost over benefits. But even Ford's last hold on the Flat Head eventually had to be let go of for change.

The benefits of Direct Valve action will out way the Push Rod, once Chain Stretch is a thing of the past. ie. Valve Actuators.
I'd take the Ford 5.0L over GM's 5.3L every chance I get, although FCA's 5.7L HEMI I could go either way and be OK.
 

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Yes but Why? Why are they the last hold outs? Packaging, Efficiency, Costs? Why when all of their other engines have switched to OHC design? I say cost over benefits. But even Ford's last hold on the Flat Head eventually had to be let go of for change.

The benefits of Direct Valve action will out way the Push Rod, once Chain Stretch is a thing of the past. ie. Valve Actuators.
I think it's almost impossible to make an optimum comparison between them because they're not in vehicles with the same weight, aerodynamics, and transmission. But it seems like the latest GM pushrod small block and FCA 5.7 and 6.4 liter pushrod V8s hold their own for power, efficiency, and weight with Toyota's (admittedly now relatively old) 5.7 liter OHC truck V8, Nissan's 5.6 liter OHC truck V8, and the Ford 5.0 OHC V8.
 

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