Advantages and disadvantages of valvetrain desing

[donniekak]

Sr's are synonomous with valvetrain problems. I agree shim under bucket is the way to go. The only problem is when you use spring pressures high enough for high rpm use the valves sink into the seats and the adjustment interval gets shorter. The system used in our cars with finger followers and hydraulic lash adjusters can work up to about 8300 rpm's. Which is ok, because how many people have turbo's and heads that make power that high anyway.

[Highboosted]

The 2JZ is shim under bucket as is the 7M and 1J, IIRC.

Since the 2JZ is in the Supra, and the Supra can neva lose, and I heard Jesus drives one, shim under bucket is the end-all to valvetrain. Until valve adjustment time. I'm sick and tired of adjusting valves.

but seriously, back OT. 2 valve motors will generally flow more at lower lifts than 4 valve motors because a 2-valve hear has less shrouded area around the valve. At higher lifts, a 4-valve head will out-flow a 2-valve head. Push rod motors are generally smaller, lighter, and cost considerably less. That last reason is the most important to manufacturers. Saying that one is better than the other really shows everyone else that you're incapable of seeing the big picture. You must balance your needs and wants just like manufacturers, and that will determine which system meets your requirements.

[3startuna]

2 valve sucks balls 4 and more valves FTW!!

5 valves per cylinder ohh mmmmm I love the 4age 20V alot

[JasonY]

Those 2 valve LS7's and LS9's FUCKING SUCK dont they Tuna? Puuhlease.

Each has their benefits as i bet the LSX engine isnt as tall as our 6g72. Look at the size difference the LS9 from the ZR1 even with the blower on top of it compared to the 3.8L in the new skyline.

Both are good designs, i like the simplicity of the pushrod engines. Saying a DOHC engine is easier to work on than a PR one is silly, and how many HG's have u ever had to change for some random reason?

Jason

[inperfectdarkness]

i'm a fan of SOHC, especially since the advent of SOHC with 4-valves, and direct injection. less reciprocating weight in the engine than pushrods. this has pretty much eliminated any advantages that DOHC might have over SOHC. and unless someone comes up with a radically different combustion chamber shape, > 4 valves is very difficult and increasingly complex.

i prefer the simplicity of a diesel engine myself. that's where i would definitely want a pushrod instead of an OHC. i would think that OHC also is infinately easier to design cylinder de-activation around.

imho, unless you're running an engine in a "W" configuration, you're probably going to get more out of an OHC.

i would bet that you could take any LSX engine, convert it to OHC configuration, and it will make better #'s.


of course, this is all crap. the best cylinder design has never been put into major production. so it's like an argument for who deserves 2nd place.

[3startuna]

Originally Posted by JasonY

Those 2 valve LS7's and LS9's FUCKING SUCK dont they Tuna? Puuhlease.

Each has their benefits as i bet the LSX engine isnt as tall as our 6g72. Look at the size difference the LS9 from the ZR1 even with the blower on top of it compared to the 3.8L in the new skyline.

Both are good designs, i like the simplicity of the pushrod engines. Saying a DOHC engine is easier to work on than a PR one is silly, and how many HG's have u ever had to change for some random reason?

Jason

apples and oranges man, an engine is more than one part and its the combination of the parts that make it good or epic suckage.
you cant say "it has a 2 valve valvetrain and makes more power so its better"

You cant compare a 3.0 to a 7.0L. Displacement alone is twice as large and that makes a significant difference. Plus it has two extra cylinders etc, etc.

[3startuna]

Originally Posted by inperfectdarkness

i'm a fan of SOHC, especially since the advent of SOHC with 4-valves, and direct injection. less reciprocating weight in the engine than pushrods. this has pretty much eliminated any advantages that DOHC might have over SOHC. and unless someone comes up with a radically different combustion chamber shape, > 4 valves is very difficult and increasingly complex.

i prefer the simplicity of a diesel engine myself. that's where i would definitely want a pushrod instead of an OHC. i would think that OHC also is infinately easier to design cylinder de-activation around.

imho, unless you're running an engine in a "W" configuration, you're probably going to get more out of an OHC.

i would bet that you could take any LSX engine, convert it to OHC configuration, and it will make better #'s.


of course, this is all crap. the best cylinder design has never been put into major production. so it's like an argument for who deserves 2nd place.

6G72 DOHC VS 6G72 SOHC of similar years. Which would you rather have?

B16 Vs D16?

I rest my case

[inperfectdarkness]

i wasn't aware that the 6g72 SOHC was available with a 4-valve configuration in the 3/s.

oh that's right. your reading comprehension FTL.


there's a reason mitsubishi is only making SOHC's these days. think they might have something?

[JasonY]

I stated nothng about specific poweroutput in direct comparison to the skylines engine. I was stating packaging is MUCH better on the PR engine compared to the immensely tall DOHC engines.

Jason

Originally Posted by 3startuna

apples and oranges man, an engine is more than one part and its the combination of the parts that make it good or epic suckage.
you cant say "it has a 2 valve valvetrain and makes more power so its better"

You cant compare a 3.0 to a 7.0L. Displacement alone is twice as large and that makes a significant difference. Plus it has two extra cylinders etc, etc.

[3startuna]

Originally Posted by inperfectdarkness

i wasn't aware that the 6g72 SOHC was available with a 4-valve configuration in the 3/s.

oh that's right. your reading comprehension FTL.


there's a reason mitsubishi is only making SOHC's these days. think they might have something?

you realise mitsubishi is broke right....

just saying