Pushrods vs Overhead Cams

[GLD-086]

Hopefully this will create a interesting topic.

Anyway I've never understood why people compare these two together. Does it really matter what configuration the cams are in?

I LMAO at the wankers that bag on Pushrods for being old, even though Overhead Cams have been around for almost 100 years.

Also do you think Holden should keep with the recipe they know, and continue working with Pushrod V8s, or jump to a OHC? Personally I think they should stay with OHVs. It's worked for them for well over 40 odd years.

Discuss people.

[VSO.38]

OHC and DOHC engines are good for higher revving engines but for a V8 I would rather a low revving engine with plenty of torque which is what you get from OHV engines... but thats just my opinion

[VT-565]

Originally Posted by GLD-086

Personally I think they should stay with OHVs.

I will add my bit on this, but just to clear it up, OHC and pushrod engines use OverHead Valves man.
I am a firm believer in if you want to crystal ball holdens future powerplants, look to the states. And to throw some sand in the eyes of the pushrod-baggers, the LS7 PUSHROD engine won powerplant of the year at a convention in europe. The judging board was made up of engine experts from all major countries including japan, so i say "get that up ya!"
OHC might be easier to work on or breath better or whatever, but if it aint broke, dont fix it. pushrods for a long time to come.

[SICK SS]

Originally Posted by VSO.38

OHC and DOHC engines are good for higher revving engines but for a V8 I would rather a low revving engine with plenty of torque which is what you get from OHV engines... but thats just my opinion

thats not totaly true y dose a stock 6 lt out rev a och 5.4lt ford motor?

[LowVp]

OHC is the best way to go simply because there is less parts to move and less drag as there are no lifters, pushrods and rockers to lift, cam sits straight on top and does the work directly

[VT-565]

Originally Posted by SICK SS

thats not totaly true y dose a stock 6 lt out rev a och 5.4lt ford motor?

How true that is.
The ford engine is quite weird as the top end is suited to a shorter stroke engine. The ford bottom end is a truck engine.

As for less moving parts with OHC, look at the lengths of the timing chains or belts versus that on a pushrod engine. Also, on direct acting overhead cams, valve lift is 1:1 with lobe lift on the cam, so you have to physically have a much bigger cam to get more valve lift, whereas on a pushrod engine, you can simply change the rocker ratio to get more effective valve lift. If you really want to get picky, OHC engines have more weight above the centre of gravity of the vehicle, too.

[grigor]

The main reason pushrod engines are doomed is VVT.
You can't separate inlet and exhaust valve timing easily, when both lobes are on the same bump stick.
Fit twin cams and away you go. You don't see too many twin cam pushrod engines do you, just makes so much more sense to go twin OHC with variable cam timing on both cams.
Simplicity wins.

[VT-565]

Originally Posted by grigor

The main reason pushrod engines are doomed is VVT.
You can't separate inlet and exhaust valve timing easily, when both lobes are on the same bump stick.
Fit twin cams and away you go. You don't see too many twin cam pushrod engines do you, just makes so much more sense to go twin OHC with variable cam timing on both cams.
Simplicity wins.

Simplicity? Ha ha ha ha
VVTi...VTEC....**** me dead....how much **** can these guys come up with?
I dont know where the simplicity bit comes in.....four cams (twin OHC V8), 4 advance-retard motors, two timing belts/chains and not to mention, the management of the cams.
Versus 1 cam, one chain, lifters and pushrods. I was going to put rockers in there too, but some OHC engines use them still.
I think this will be as endless as the "turbo vs. supercharger" debate, but I've made my statement.......for now

[MasterOfReality]

Umm, isnt the current most powerful naturally aspirated V8 in the world the new AMG 6.3 litre V8 (they are actually 6.2l, but badged 6.3l due to German classifications)?

375kW @6800rpm and 630Nm @5200rpm, redline 7200rpm.

There is also a turbo charged version on its way as well, with a specified power output of 525kW and over 1000Nm of torque.

So there goes the argument about pushrod donks being better for torque, turbo charged or not.

[1991_Vn2nV]

Originally Posted by MasterOfReality

Umm, isnt the current most powerful naturally aspirated V8 in the world the new AMG 6.3 litre V8 (they are actually 6.2l, but badged 6.3l due to German classifications)?

375kW @6800rpm and 630Nm @5200rpm, redline 7200rpm.

There is also a turbo charged version on its way as well, with a specified power output of 525kW and over 1000Nm of torque.

So there goes the argument about pushrod donks being better for torque, turbo charged or not.

Ummm not if those stats you gave are correct, because...

LS7 is 377kw @ 6300rpm and 637NM of torque @ 4700rpm with a 7000rpm redline. Whack a charger on that and use the LSX block and you're laughing

[MasterOfReality]

Originally Posted by 1991_Vn2nV

Ummm not if those stats you gave are correct, because...

LS7 is 377kw @ 6300rpm and 637NM of torque @ 4700rpm with a 7000rpm redline. Whack a charger on that and use the LSX block and you're laughing

ahah, ok, what if it was based on engine size?

I believe the LS7 is a 7 litre and only produces 2kW and 7Nm more?

Therefore the AMG produces more hp per cubic inch.

[vn6pwr]

Originally Posted by MasterOfReality

ahah, ok, what if it was based on engine size?

I believe the LS7 is a 7 litre and only produces 2kW and 7Nm more?

Therefore the AMG produces more hp per cubic inch.

well if were talking hp per ci, then bmw takes that one... new v8 4.0L, 309kw 400nm.

[HaMmErD]

Originally Posted by vn6pwr

well if were talking hp per ci, then bmw takes that one... new v8 4.0L, 309kw 400nm.

those torque figures are a bit lame for a v8 .... although considering its only a 4.0l .... id be dissapointed IMO