bamxbam

iTrader: (2)

For my Public Speaking class I have an informative speech to do by next week, and the topic I chose to do is comparing OHC and pushrod motors by giving basic info, and pros and cons of BOTH. However, this is not a persuasive speech, and as much as I am slightly biased towards pushrod motors, I have to remain as neutral as possible, although my professor does understand there may naturally be a bit of bias present. I think I have my intro and conclusion covered, but I have to cover 3 main points. So something probably like...

1. OHV/pushrod
a. arguments for
b. arguments against

2. OHC
a. arguments for
b. arguments against

3. Myths
a. displacement =/= engine size and weight
b. something else... whatever

Now I have read some articles, whatever I found on google, and quite a bit of threads on other forums debating between the two designs, but just in case I missed anything, anything you guys can add or contribute will help. Thanks!

Wesmanw02

iTrader: (4)

Heres a few:

People often assume that the OHV design is an "older" design than OHC. Fact is, both were used from the start of internal combustion engines.

OHV engines tend to have wider torque curves than OHC motors. In general, they also produce better low end power.

GM considered both OHV as well as OHC designs for the 1997 Corvette engine, which later became known as the now famous LS1. Prototypes of both head designs were made, and after GM employees were asked to test each version, the votes were far in favor of the OHV version, mainly for its excellent driveability and instant power.

OHC motors tend to be better at higher RPM's. They have less valve train components and therefore less valve train mass. A stock 03-04 Mustang Mach 1 with the DOHC 4.6 Modular has a redline of 7,000RPM, as compared to a stock LS1, which hits the fuel cutoff at 6200RPM.

OHC tend to be much more expensive to upgrade the valvetrain with aftermarket components, since you have anywhere from twice to 4 times as many cams as an OHV motor.

Disturbed Bird

iTrader: (9)

ohc are also much bigger at the same displacement then the ohv motor. look at the stang mod motor and the ls1( i know the mod motor is a 4.6. ford dosnt make a 5.7 mod motor). ls1 is smaller then the 4.6, chevy had a ohc v8 it was called the LT5. the reason they went a way from it was it cost to much to maunfactor 4 cams vs 1, 32 valves and springs vs 16. more metal to cast for the bigger heads and more metal for the block. the LSx ohv motor gets better MPG then the ohc 4.6 ford mod motor.

and just to let you know the LS7 revs to 7,000rpm. 427ci ohv motor still gets better mpg's then a 4.6L ohc motor

Bullitt347

Some of the mileage gain is due in part to the LS7(corvette) is quite a bit lighter than the Mustang. Not to mention the heavier Mustang is making a smaller engine do more work than the bigger engine in the lighter Corvette. Although the LS7 is slightly better in the H.P. per CID than the Mustangs 4.6, (GT only). And lets not forget aerodynamics also play a role. So the better MPG is not just a "better" engine issue at all.

Suaveat69

I believe that the OHC was invented in 1912 and the OHV came 7 to 8 years later.

OHV motors are very efficient. A Cup motor is about 99% as efficient as an F1 motor and Pro stock is more efficient.

If I can find the link I will post, it extensively compares the OHC vs. OHV.

TT632

iTrader: (3)

Please post. 1917 or 1919 for the OHC.

gyrene2003

i had heard, actually on this website, when a member had posted that ohv motors were old news and ohc motors were the way of the future, that someone else posted that in WW1 or 2, cant remeber which, that thier were planes using ohc motors.

Suaveat69

I looked and could not find anything. I believe it was called "Pushrods vs. Extinction". I copied most of the inof but it is on my other hard drive that I have to send to a clearoom. Sorry I could not help.

twelver12

iTrader: (3)

yeah yeah alot of people also say that the v8 is on its way out also but who is gonna give theirs up? not me. oh and the LT5 was actually made by lotus its the only engine ever to go in a corvette that was and ohc and also the only engine not made by chevy to go into it

99bowtieZ

http://www.autoblog.com/2005/12/08/a...finitive-rant/

chuntington101

the P51 ran the RR Merlin engine. that was a 27ltr SOHC 4 valve per cylinder. later the RR Spitfires moved onto the Griffith engine that was 36ltr.

its not where the cam is that makes the difference, its the number of valves you run and thus the 'curtain area' of the valves

Chris.

bamxbam

iTrader: (2)

Aw man that's too bad. Thanks anyway though.

Actually Lotus just had a part in designing the engine, but Mercury Marine actually manufactered it.

Good article, ready this already a couple of months ago.

twelver12

iTrader: (3)

so its a boat motor? lol i never have heard anything about mercury marine building it, not sayin i dont believe you just sayin i always heard all about lotus

99bowtieZ

Haha nah man he is right. GM contracted Lotus to design it. Then the plant they had going at the time was not able to produce it, so they got Mercury to manufacture them...

bearcatt

iTrader: (41)

.

http://www.museumofamericanspeed.com...nes/E011.shtml

http://www.museumofamericanspeed.com...LLThumbs.shtml


.

elias_799

iTrader: (8)

did you guys forget that a pushrod motor can have 4 valves per cylinder ?

look at most of the diesels out there.