Pushrods vs DOHC

[Herr_Poopschitz]

In the purist sense, if you're slamming fuel and air into a cylinder and clearing its exhaust out, it's hard to argue that being able to manipulate more cams and valves are not more beneficial. And the more RPM you add to the equation, less material between valve actuation is always better.

If there was a mechanical advantage using pushrods, F1 engines would have them.

F1 regs don't favor the use of pushrods. That's why they're not used. The FIA says 1.6L displacement and 15000 rpm. Valvetrain stability goes wonky on pushrods far before that, even w/ pneumatic springs.

Sorry pro-pushrod guys, but the same goes for Top Fuel...only reason they use pushrods is due to rules that simply don't allow ohc. Although I'm not sure about tear down times on one between rounds, anyway...yikes.

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[Hack]

Seems there are a lot of definitions that need to be established.

A Venom is a hot rod, but a Veyron or Koenigsegg is considered a production car?

The addition of displacement is 'cheating', yet having multi-valved heads w/ variable valve events on both in and ex isn't?

I'm starting to get it...it seems the rules have been written in favor of DOHC from the start.

I'm not sure what is 'elegant' and 'highly engineered' about DOHC vs pushrod. The whole process is quite frankly an awful mess...that, or completely beautiful. Again, neither is better or worse, just different.

What is a 'real top sportscar'?:shrug:

As I pointed out, Corvette Racing seems to do quite well w/ their inferior pushrod engines and their cheap, underengineered Corvette chassis against the likes of 'real sports car manufacturers' Ferrari, Porsche, BMW, etc.

Ultima Evolution is pretty badass too...but clearly it's too boutique and excluded from contention to be a 'real sports car'.

Basically, nothing w/ pushrods seems to satisfy your narrow/limited definition of what a sports car seems to be...

I'm not saying a pushrod engine couldn't have independent variable cam timing with separate intake and exhaust timing events. I know Dodge had patented a cam in cam technology that allowed the two to be played with separately - and I think it was even in their production engines. Not sure whether it still is or not. But those are details like engine size and weight and the location of the weight that Chevy people like to get into and say - oh the engine weighs more so it's no good. Then the Ford people say the 302 Ford weighs 470 lbs and the Coyote weighs 444 lbs - so the weight argument is not necessarily valid. Then the Chevy guys say - oh the weight is up high which is bad. Blah blah blah..

I understand what you are doing in changing the subject and going to different arguments. Racing doesn't really count as showing you the best engine because racing is all about what the rules allow. There was a team that was going to run the Boss 429 in top fuel rather than the 426 Hemi. The rules were promptly changed, because the money behind drag racing is in bed with the manufacturers of the 426 Hemi components.

Yes it's a complex topic so my clarifying statements are the best thing to go back to, IMO. Rather than stating that I'm an expert and I know more, I trust that huge corporations that have teams of experts working over years of time in order to select the best engine designs - those people actually know what they are doing.

 

[Norm Peterson]

Precisely. For many here, there is only DOHC and nothing else.

Never mind that 4V pushrod engines exist.

Never mind that pushrod engines run well above 8K RPM.

Starting with that last item, yes they can. But there is significantly more maintenance involved. So, possible = sure, but practical in anything remotely useful for daily driving = not.

For the rpm range used in street driving, a 2-valve pushrod engine is entirely appropriate, and may even have some benefit based on intake port cross section (flow velocity). If nothing else, said port need not open up wide enough to feed a pair of intake valves with greater total width than a bigger single valve.

The ability to vary the valve timing might be the DOHC's biggest benefit in (regulated from at least two different directions) street driving.


I've had my hands dirty with pushrod and OHC engines both. And as long as whatever I'm working on works for my application I'm not too particular about how many valves or cams it might have. Including none of either if I ever end up with a Wankel in anything.


Norm

 

[Herr_Poopschitz]

I understand what you are doing in changing the subject and going to different arguments.

Interesting, that's what I just accused you of doing. You've poo-poo'd EVERY bit of evidence I've given, simply bc it doesn't meet your infinitely limited criteria. For being open minded as you claim previously, well, you aren't.

Racing doesn't really count as showing you the best engine because racing is all about what the rules allow.

Wow, not even racing counts now? You keep moving the target. No evidence can satisfy your very limited criteria at this point, except your own. That's great for an individual to conclude they are correct, but objectively shows the narrow mindedness of the individual...it's a shame you can't step out and see this for yourself.

There was a team that was going to run the Boss 429 in top fuel rather than the 426 Hemi. The rules were promptly changed, because the money behind drag racing is in bed with the manufacturers of the 426 Hemi components.

Yeah, pretty sure I mentioned rules previously.

Yes it's a complex topic so my clarifying statements are the best thing to go back to, IMO. Rather than stating that I'm an expert and I know more, I trust that huge corporations that have teams of experts working over years of time in order to select the best engine designs - those people actually know what they are doing.

As an engineer/scientist, you should be ashamed for submitting to such reasoning.

Follow this link, print off a few posters...hang one in your workplace, above your bed, and one on the wall opposite your toilet. Aristotle is disappointed in you.

https://yourlogicalfallacyis.com

Learn it, love it, live it.

Ciao

 

[Rickycardo]

I understand what you are doing in changing the subject and going to different arguments. Racing doesn't really count as showing you the best engine because racing is all about what the rules allow. There was a team that was going to run the Boss 429 in top fuel rather than the 426 Hemi. The rules were promptly changed, because the money behind drag racing is in bed with the manufacturers of the 426 Hemi components.

Sorry but the 429 Boss engine is push rod too.

 

[Herr_Poopschitz]

Sorry but the 429 Boss engine is push rod too.

I assumed he meant the 427 Cammer. That, or as another desperate method of dismissing overwhelming evidence contrary to his preconceived notions. Who knows.

Another note I find funny is this bowing to 'experts', but picking and choosing who the experts are. GM is the second largest auto manufacturer in the world...but their experts somehow aren't worthy of admiration/respect or something...because they aren't German. Silly logic.

In practice, pushrod engines are more friendly to the middle class garage-based enthusiast due to architectural layout as well as cost. That's ultimately why they're better to me.

 

[Hack]

I assumed he meant the 427 Cammer. That, or as another desperate method of dismissing overwhelming evidence contrary to his preconceived notions. Who knows.

Another note I find funny is this bowing to 'experts', but picking and choosing who the experts are. GM is the second largest auto manufacturer in the world...but their experts somehow aren't worthy of admiration/respect or something...because they aren't German. Silly logic.

In practice, pushrod engines are more friendly to the middle class garage-based enthusiast due to architectural layout as well as cost. That's ultimately why they're better to me.

No I was talking about the Boss 429 because some people think the 426 Hemi running and winning all the top fuel races means that it is the best engine for that purpose. I was trying to illustrate that winning races doesn't always mean an engine is great. It just means the rules made by the sanctioning body have allowed that engine to win.

But thanks for bringing up the Cammer. NASCAR immediately outlawed it for some reason. I wonder why? It didn't have more cubes than the competition.

Yes GM is huge, so them being one company that still uses pushrods means that pushrods aren't so horrible as to be uncompetitive. However, if you look even at passenger cars made by GM, I'd bet you the quantities of engines GM produces are dominated by DOHC. But just because the highest quantity of engines are DOHC, that doesn't necessarily mean it's better... or does it? DOHC engines are used both in the best stuff out there as well as many/most economy cars... huh. Interesting thing, isn't it?

As an engineer/scientist, you should be ashamed for submitting to such reasoning.

I've been working as an engineer for many years and I feel confident that going to subject matter experts to help with projects is a good strategy.

I do it all the time. It helps me get more done more quickly. I don't assume that I'm a genius and I know more than everyone else.

In practice, pushrod engines are more friendly to the middle class garage-based enthusiast due to architectural layout as well as cost. That's ultimately why they're better to me.

I agree with this statement 100%. I have no desire to work on my DOHC engine. If I want more power or something, I'll buy a different car with a different engine... or strap on a power adder!

 

[Herr_Poopschitz]

No I was talking about the Boss 429 because some people think the 426 Hemi running and winning all the top fuel races means that it is the best engine for that purpose. I was trying to illustrate that winning races doesn't always mean an engine is great. It just means the rules made by the sanctioning body have allowed that engine to win.

The 426 Hemi isn't used in TF.

But thanks for bringing up the Cammer. NASCAR immediately outlawed it for some reason. I wonder why? It didn't have more cubes than the competition.

Comparable displacement...do you know what the competition was using? The pushrod Hemi was outlawed as well...

Yes GM is huge, so them being one company that still uses pushrods means that pushrods aren't so horrible as to be uncompetitive. However, if you look even at passenger cars made by GM, I'd bet you the quantities of engines GM produces are dominated by DOHC. But just because the highest quantity of engines are DOHC, that doesn't necessarily mean it's better... or does it? DOHC engines are used both in the best stuff out there as well as many/most economy cars... huh. Interesting thing, isn't it?

You didn't look at the link I recommended, did you? It's not about quantity - you can't win technical arguments by quoting numbers.

You said it yourself, albeit in a very derogatory way, that pushrods are competitive. That's all I've been saying this whole time.

I also agree with your statement that pushrods are more friendly to the middle class garage mechanics out there. I have no desire to work on my DOHC engine. If I want more power or something, I'll buy a different car with a different engine.

I can't wait for the first LS powered '15...

 

[arghx7]

enjoy pushrod v8's for the next few years, because turbo DOHC engines are going to replace them, either 6 cylinders like the Ecoboost 2.8 and 3.5 or smaller turbo 8 cylinders with inboard turbos like what BMW, Audi, and Mercedes already sell. Mark my words.

2019 will be a big year for that, and by 2021 they'll be all but dead. You can thank emissions (LEV III, Tier III, Euro 6C) and fuel economy standards. The same thing happened to diesels decades ago. When was the last time you saw a nonturbo diesel for a passenger vehicle?

 

[Catfish]

I own a quite a few pushrod engines, but now a days when I think pushrods...I picture this....

 

[Todd15Fastback]

What forged rods are those?

:lol::lol::lol::lol:

 

[Catfish]

What forged rods are those?

:lol::lol::lol::lol:

I send those to my LS loving buddy all the time and he gets a little pissed. LOL:lol:

 

[Todd15Fastback]

I send those to my LS loving buddy all the time and he gets a little pissed. LOL:lol:

Bwhaaaaaaaaaaaaaaaa:lol::lol::lol:

 

[Grintch]

Thanks for all of the responses guys. Here's one more question for you. Hypothetically speaking:

The coyote is a pretty large engine in terms of it's size and weight.
Dimensions: 27" H X 26" D X 28" W
Engine Weight: 430 lbs.

If we were to build a pushrod motor with the same dimensions, would it be more powerful than the coyote?

Obviously Ford would not do this, because of the cost. Also, this is just a hypothetical situation. I am not trying to troll here, just genuinely curious.

Define, "same dimentions". Same displacement, no way. Same external W x H x L, probably.

 

[Daytona Coupe]

Sorry but the 429 Boss engine is push rod too.

That's not a Boss 429 - lol!

It's a 460-based wedge head motor FWIW...
But you're right, a 429 does have pushrods.

This thread has gone so far out of whack with red herrings being thrown everywhere, it's actually pretty entertaining.

I own both and like both... :cheers:

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