What is the 3.9 v6 the general is using now?

"scott" wrote in news:1170040081.521877.245610 @l53g2000cwa.googlegroups.com:

I don't think it's a bored version of the 3.8 because why would they go to the trouble of boring it out just for a measly extra 1/10 of a liter? Unless their intent is to deceive people into thinking it's a brand new engine perhaps. I wonder why GM still stubbornly embraces pushrod engines? Get with the program GM.

This is a common statement - as if OHC is some sort of sign of the times. It's almost as old as OHV designs, and it suffers its own set of issues. What is it that causes you - and others, to equate OHC with high-tech, advanced designs? Have you really compared OHC with OHV? Considered all of the factors that an engine designer has to consider as he dreams up a power plant that will eventually go under a hood?

I'm not against OHC designs, nor am I an absolute advocate of OHV. The two have their own set of benefits going for them. I just wonder sometimes, when I read a comment like yours, just exactly what people are really basing their comments on.

| > I don't think it's a bored version of the 3.8 because why would they go to | > the trouble of boring it out just for a measly extra 1/10 of a liter? | > Unless their intent is to deceive people into thinking it's a brand new | > engine perhaps. I wonder why GM still stubbornly embraces pushrod | engines? | > Get with the program GM. | >

| | This is a common statement - as if OHC is some sort of sign of the times. | It's almost as old as OHV designs, and it suffers its own set of issues. | What is it that causes you - and others, to equate OHC with high-tech, | advanced designs? Have you really compared OHC with OHV? Considered all of | the factors that an engine designer has to consider as he dreams up a power | plant that will eventually go under a hood? | | I'm not against OHC designs, nor am I an absolute advocate of OHV. The two | have their own set of benefits going for them. I just wonder sometimes, | when I read a comment like yours, just exactly what people are really basing | their comments on. | | -- | | -Mike- | snipped-for-privacy@alltel.net | I liked the old Ford flatheads for simplicity. One cam, cam followers and valves. I thought I went to heaven after I installed adjustable followers in my '37 Coupe. They were contoured to match the cam and were kept in alignment by a cotter key.

The 3.9 engine is a revised version of the 3.1-3.4 engines. The main differences are no wet intake manifold, all of the coolant is now carried externally with water crossover style manifolds (Northstar has been this way from day one), and it has a variable valve timing mechanism on the camshaft.

What's wrong with pushrod engines? As someone else mentioned, people seem to think that OHC engines are somehow "new". Go have a look at an aircraft museum and take a look at what was being used in WW 2 fighter aircraft! Overhead cams, superchargers, turbochargers, fuel injection, throttle body injection, compound turbochargers. Probably some of the greatest engines of the war were radial engines with pushrods. I believe that most of this technology originated in the 20's.

The OHC engines that GM has put out, without exception, have been far more costly to repair then pushrod engines. Consumers would be better off using the pushrod engines...lot less money when you have to fix something.

Ian

And this is by no means limited to GM OHC engines Ian. OHC by its very nature is more complex and more expensive to repair than a pushrod design. This transcends manufacturer's lines.

"scott" wrote in news:1170040081.521877.245610 @l53g2000cwa.googlegroups.com:

i wouldnt downgrade the pushrod engine so quickly if i were you. especially in domestics! thru my 30 years of watching and working on detroits better ideas i find every attempt at OHC a real experiment on their part. on my part i have found their experiments VERY costly to the consumer (quad 4 ring any bells?) and either underpowered or with the power band in the wrong dam place.......for my personnal vehicles i have always sought domestic pushrod engines and walked away from OHC. just my 2 cents......

I respect both your and Ian's opinions, but in this case I do not feel that OHC engines are inherently more expensive to make or repair. They are not particularly more complex, in my mind at any rate, do not necessarily have more parts, but also do not guarantee better performance than a pushrod OHV engine.

They CAN be stompers. But, OHC as such, and particularly as articulated by GM, means little.

particularly

The reason that I make that statement is the cost of any valve related work which is typically more expensive than with a pushrod engine. If the engine is built with a timing chain as opposed to a belt, the reliability is pretty much equal to a pushrod timing system, but there are still belts out there and in that there is more expense, if for no other reason than the routine change required. With interference designs this becomes a pretty big issue for those who keep cars a long time.

From a design standpoint, it is much harder to design and build a lower profile engine with OHC design, thus fitting today's more aerodynamic body styles, and still keep a decent torque. With pushrod engines it's easier to keep a lower head profile and build an engine with a bigger lower end and more torque. No need to run it up to such high rpm's in order to stay in the torque band.

As an aside - I find it nothing short of amazing that NASCAR teams are consistently and reliably (if that term can ever be applied to a stock car engine...) building pushrod engines that are approaching 10,000 rpm's. We used to think that was impossible.

I agree with you on the latter point, Mike. There is a lot of really trick gear out there, if you can afford it, that will live under very inhospitable conditions.

I am a Formula 1 fan, and find it hard to believe at times that they can push some of these engines as far as they do. Race rules with F1 still push two races per engine (with no repairs allowed), and there are exceptions and penalties, of course.

These engines routinely turn up to nearly 19,000 rpm throughout the race, which lasts for something over two hours usually. (For those who are not into F1)

They switched the formula from V10 engines to V8s a year or two ago. I believe they are still 3 litre engines, very special valving systems, and put out in the range of 700-800 horsepower...maybe more this season.

Try this link:

I can agree with you for Vee engines. But for inline engines, the difference is trivial, and the OHC engine might actually be easier to work on - just depends on the cam drive. My 1972 Pinto with the 2L OHC engine was the easiest engine I've ever dealt with. It was even easier than the 1.6L Kent 4 in my Fiesta (although the Fiesta was easy too).

Ed

Here's a good article for everyone to read:

Steve

Hey, me too! I'm just glad to finally see Shumacher out of the F1 arena. I'm hoping that it will be more interesting and less of his bs (apologies if you happen to be a Shumi fan).

Yeah....these are very exotic engines. I still remember when the Turbo 1.5 liters were around, they approached 1000 hp in qualifying trim. Can you imagine?

Ian

You can be sure I was NOT a Shumi fan, Ian. He was undoubtedly one of the worlds greatest drivers, but very unsportsmanlike and underhanded. His tactics could not be respected.

I am amazed that Renault was able to field a team as strong as the one last year. Absolutely phenomenal.

Ferrari proved their durability, but I like to see a strong competition.

Poor old sour faced Frank Williams has been relegated to Ford Cosworth, which is like, IMO, sleeping with the town tramp.

We'll keep in contact as the season nears.

Absolutely....oh goodie...I get to "get up" at

5 am in the morning just to see a race! My wife always thinks I'm crazy to get up that early. It was difficult over the last two years to do it as the excitement wasn't there as much, but I'm hoping that we'll see better racing this year.

Ian

Fully agree on that. It is not much fun when one team dominates the way Ferrari had done.

My wife doesnt complain too much when I turn on the Japanese or Australian Grand Prix in the middle of the night ;>)

I don't care for the hp and torque curves on OHC engines. So far I've avoided owning a OHC engine.

I had a Maxima SE 5 speed with the 3.0 VQ engine (DOHC, 24 valve) and it had nearly zero torque anywhere near idle. It would scream if you drove it over 3000 rpm, but it was so easy to kill the motor just driving it around. Sold that and got the '00 intrigue with the 3.5 GM premium v6, with also OHC and 24 valves. Totally different motor dynamics, it has a great torque curve but unlike the OHV cars I've owned it doesn't go flat as it revs, it pulls (and smoothly) right up to the redline. So don't put all the engines in the same bucket.

S

The fact that an engine has overhead cams doesnt determine the torque curve nor the horsepower development. It is what you do with the camming that makes a massive difference.