help educate me! (engines)

[ndhaon91]

before getting my sport a few months ago, i knew zero about cars. i'm trying to learn as i go...

here is my question about engines... i understand the concept of the camshaft and the difference between a SOHC and DOHC engine. i also know that some engines have the cam in the block itself, which puts pressure on a pushrod, which in turn opens the valves. how are the other engines i've heard guys discuss on here set up? what is an overhead valve engine? also, what is the set up on the 5.0 V8? what category is it in? thanks!

(on a side note, my buddy just purchased an '03 crown vic. he said it was a 4.6 V8, but it looks just like the V8 in the explorers to me... is it actually a 5.0 in there?)

 

[double_take]

Someone please correct me if I'm wrong.

You know i've never really taken the time to check out my V8 i think it's an OHV like the base V6. The main difference in the OHV and SOHC is the location of the camshaft.

As for the 4.6L vs 5.0L the newer ford V8 are a different engine it's a 4.6L.

 

[bates]

www.howstuffworks.com

Check out this link to learn just about anything you want to know.

As for the direct questions, I'm pretty sure double_take is correct. The OHV(over head valve) is the same type you described using pushrods. The 5.0L is also an OHV, but if memory serves me right, there is a SOHC version.

And I believe the 4.6L is a DOHC, and is very different from the 5.0L. Good Luck!

 

[Ford_Racing_Guy]

some 4.6 liter's are DOHC and most are SOHC

 

[Billy177]

ya the 5.0 is pushrod

the reason why we odnt use the dohc is because with 4 valves per cyl the toqure (sp) peak is a lot higher rpm. this is good for cars but not truck/suv engines

 

[ndhaon91]

ok, so:

OHV = Pushrod

5.0 V8 in the Ex = OHV

'03 Crown Vic = 4.6 V8

4.6 V8 = either SOHC or DOHC



that makes sense about SOHC having more low end power than the DOHC... but what is the factor automakers use in deciding whether a given engine will use pushrods or overhead cams? what is the advantage/disadvantage of each?

 

[Billy177]

cost
size- ohc is much bigger
pushrod has proven itself
requires new tools to manufacture the new engines

 

[double_take]

Also even though it says Single Ovehead Cam. That means one cam shaft per cylinder bank. So on v6 or V8 engines it means 2 camshafts vs one. And DOHC have 4 Camshafts on V6 or V8 engines. This is one of the reasons most OHC engines are larger than a OHV.

 

[00XLS]

Originally posted by Billy177
ya the 5.0 is pushrod

the reason why we odnt use the dohc is because with 4 valves per cyl the toqure (sp) peak is a lot higher rpm. this is good for cars but not truck/suv engines

I thought the navigator used the 5.4 DOHC?

 

[Billy177]

i just checked it does the only thing that i can think of is fuel milage. if it were me i would use the 3valve heads from the f150

edit: it says 91 octane min. if you areadly have to run 91 why not bump the compression up from 9.5:1 to 10:1

 

[Billy177]

also the expidition uses the 2 valve heads and makes 350tq

a lot of people think the higher the horsepower the better they don't care about the torque. so the 4 valve heads will sell more cars plain and simple.

"horsepower sells cars, Torque wins races "