overhead cam GM engines.

[Turbo6Smackdown]

I thought there was an overhead cam V8 from GM. Isnt there? I always thought one of the differences between the LT1 and the LS1 was that the LT series was pushrod, and the LS's werent. I now see that the LS series is also a pushrod engine.

 

[ijames]

The LSx motors are pushrod but the Northstar V8's are overhead cam.

 

[UNGN]

I thought there was an overhead cam V8 from GM. Isnt there? I always thought one of the differences between the LT1 and the LS1 was that the LT series was pushrod, and the LS's werent. I now see that the LS series is also a pushrod engine.

Only the LT5 ZR-1 SBC Motor is overhead cam. Pushrods work too good to go the way of the dinosaur just yet.

 

[Turbo6Smackdown]

Ahh it was the LT5 motor thats right. And you dont think overhead cam engines are better than pushrod?

 

[a trail rider]

It depends on the goal. Todays OHC engines are very advanced, but they still need higher rpm to reach their strongest potential. The good news there is, most are very much capable of reaching high rpm. On the other end, they typically suffer in the fuel economy area. It's not horrible, but an OHV will often do better when you get to the V8's. That's just what I've picked up over the past 15yrs or so when comparing the pros and cons.

 

[UNGN]

Ahh it was the LT5 motor thats right. And you dont think overhead cam engines are better than pushrod?

For a given package size, The Pushrod motor will make more HP than a OHC motor because the OHC V-8 motor is significantly wider than the Pushrod motor.

So if you want a V8 and want to put the maximum HP in the smallest physical space, pushrod is the way to go.

 

[Turbo6Smackdown]

well, size isnt an issue, as im just looking to see what my options are, as far as boltin' a motor in an later model F body. so whatever gm already has made, is my choices.

Trailrider, you say they only reach their full potential, when they hit their higher rpm band. isnt that a function of their cam, rear end gear and fuel/timing curves, and not the fact that theres no pushrods? correct me if im wrong, as i have pretty much no clue what im talkin about lol. my only area of experience, is old carbed 350's and old N/A 231's. anything else and I am only mediochre at best.

same thing goes with you ungn. correct any of my malfunctions when you see them, but how does a pushrod motor make more horsepower, when theres more moving parts. more moving parts in ANY machine makes response time come down, due to more parts, and more flex as a result. OHC motors are more direct. the cam is mechanically much closer to the ballpark, than having to go thru lifters, rockers and pushrods to do its job. Am I wrong?

 

[dgoodhue]

\correct any of my malfunctions when you see them, but how does a pushrod motor make more horsepower, when theres more moving parts. more moving parts in ANY machine makes response time come down, due to more parts, and more flex as a result. OHC motors are more direct. the cam is mechanically much closer to the ballpark, than having to go thru lifters, rockers and pushrods to do its job. Am I wrong?

Their are actually more friction loses through a DOHC motor than a pushrod motor. Their are 4 cams vs one, twice as many valves springs, a much longer cam belt/chain and most likely more tensioners. DOHC ususally can suport a higher RPM range and fit a larger valve opening, therefore can make more HP due to its ability process more air.

 

[UNGN]

same thing goes with you ungn. correct any of my malfunctions when you see them, but how does a pushrod motor make more horsepower, when theres more moving parts. more moving parts in ANY machine makes response time come down, due to more parts, and more flex as a result. OHC motors are more direct. the cam is mechanically much closer to the ballpark, than having to go thru lifters, rockers and pushrods to do its job. Am I wrong?

It's easier for a Pushrod 427 to make 500+ HP NA than a DOHC 4.6L, Right?

Can you imagine how high you would have to wind a unsupercharged Cobra motor to make 500 HP? More than 7200 RPM, that is for sure.

A Chevy LS1 427 is physically smaller than a Ford DOHC 4.6L, because the heads are 1/2 the size.

The DOHC may make more HP on a per litre basis, but on a physical size basis, the Pushrod V-8 is unbeatable.

 

[a trail rider]

I can't really say why(not really my thing), but I'll try. I think this applies more to DOHC, like the Northstar, than to OHC and that may be due to more flow capability since it has more open space through which air can flow. Having no pushrods is helpful as you'd think. Fewer moving parts. Of course, with DOHC, there are still very many moving parts. They simply don't have to move as far to reach the same goal. The OHC benefits from higher rpm more than low and that may be because it is generally smaller in displacement, which would typically mean less airflow at lower rpm than a OHV engine.

Then you've got things like VVT, which allow an engine to essentially use less of it's own ability and it can create better velocity of air, which should, but may not translate into more efficiency. It also tends to run more smoothly.

All the above is just what comes to mind, btw. I have an OHC engine in my SUV, but I'm no expert in the matter. I do know that the fuel economy isn't necessarily great and mine doesn't have VVT or "extra" valves/cams.

 

[1dmbth]

I would say they are getting a pretty good handle on DOHC engines these days. The new direct injected 3.6 liter(217CI)engine in the cadillacs makes 304HP naturaly aspirated.

 

[a trail rider]

The DOHC may make more HP on a per litre basis, but on a physical size basis, the Pushrod V-8 is unbeatable.

I don't really agree with this unless it is pretensed(is that a word) with keeping both engines N/A as opposed to using a power adder. When forced induction is added, I'm fairly well convinced that a DOHC engine of the same C.I. will outpower an OHV every time in an "all out" sense.

Also, I remember the OHC 427 Ford being so capable it was banned from things like NASCAR. Yes, it was HUGE, but it was also convincing. It made what is guessed to be well over 600hp way back then, when OHV engines were struggling to compare. even the 426 Hemi couldn't match it at the time. Infact, it wasn't even close by pretty much all accounts. Others of matching C.I. were there and trying, but it put the hurt on basically all of them in short order.

 

[turbofish38]

For a given package size, The Pushrod motor will make more HP than a OHC motor because the OHC V-8 motor is significantly wider than the Pushrod motor.

That logic doesn't fly. Just look at the DOHC 3.4 60 degree V-6 for an excellent example as far as stock motors go. Usually the reason to go DOHC is more valve surface area. Why do you think there are 5 and 6 valve motors out there? Ever look at a Ferrari or other exotic? No problem packaging a motor in them.

If you really want to blow their minds drop in the 469HP SC 4.4 Northstar from the XLR-V and STS in your car.

 

[turbofish38]

I don't really agree with this unless it is pretensed(is that a word) with keeping both engines N/A as opposed to using a power adder. When forced induction is added, I'm fairly well convinced that a DOHC engine of the same C.I. will outpower an OHV every time in an "all out" sense.

Also, I remember the OHC 427 Ford being so capable it was banned from things like NASCAR. Yes, it was HUGE, but it was also convincing. It made what is guessed to be well over 600hp way back then, when OHV engines were struggling to compare. even the 426 Hemi couldn't match it at the time. Infact, it wasn't even close by pretty much all accounts. Others of matching C.I. were there and trying, but it put the hurt on basically all of them in short order.

I agree with you. The reason the SOHC 427 was banned from NASCAR was because Ford never used it in a production car. Just look back to drag racing for a better example. That old Sock motor pretty much put the hurt to the Hemis in TopFuel racing.

 

[machinegun]

The only itme I see an issue with the northsatr, isnt it a front wheel drive configuration? If so going to play heck with getting a tranny from RWD to work.

Recommendation from me.

Inexpensive bolt in

LT1 with LT4 topend and add some boost.

cheap reliable and can make real good HP.

Want to go radical:

GM LSX block stroker at 427 ci

Trickflow Heads

Mid range cam from comp

add some boost

Either one of these combos could be used with a stock ECM tuned with EFI live or Tuner Cat pro depending on what you use. All the parts are off the shelf items and there is plenty of info out there.

One more thing, they will make tons of power and torque.

 

[a trail rider]

The only itme I see an issue with the northsatr, isnt it a front wheel drive configuration? If so going to play heck with getting a tranny from RWD to work.

Not anymore. As far as I know, most Cadillacs built today are RWD platforms. I think it's helped sales considerably too.

Northstar is the V8 in the STS and it's definitely rear drive... I think AWD is an option though.:smile:

 

[Turbo6Smackdown]

Yea, the soc 427 from back then was one of the engines that inspired me to ask this. I just got confused as to the reasoning why there arent many overhead cam motors out there. I seen how the old 427 and the early 90's ZR1 dominated everything in their era, and couldnt figure out why they arent using more OHC designs in popular high hp engines today. is it the cost of manufacturing? My other question was, why do the little engines you see in typical daily driver cars have sohc/dohc but not the 'go-fast' models?

 

[UNGN]

That logic doesn't fly. Just look at the DOHC 3.4 60 degree V-6 for an excellent example as far as stock motors go. Usually the reason to go DOHC is more valve surface area. Why do you think there are 5 and 6 valve motors out there? Ever look at a Ferrari or other exotic? No problem packaging a motor in them.

Its a 3.4L 60 degree V-6 in the same engine bay that will fit a 5.7L 90 degree pushrod V-8.


How many FWD 4.6L DOHC fords are there? Zero?

A DOHC 4.6L is the same width as a Boss 429.

The Ferrari example is a bad one. Take out the engine and there is much more room width wise in Ferrari engine bay then there is in a new Z06 engine bay, and yet, the ZO6 engine has a larger displacement. The largest Ferraris divide 6 litres among 12 cylinders, so an equivalent width V-8 would be 33% smaller displacement. Ferraris are also wider than a normal car and there is no steering shaft snaking past a mid engined Ferrari.

Apples and oranges.

 

[a trail rider]

I think the cost is more for the typical V6 or V8 OHC engine because it has much more into the cyl. heads and front of the engine.

The two major manufacturers which still use OHV for high performance are GM and Dodge. Others like Ferrari, BMW, MB, even Ford have all used OHC instead for awhile now. Most Jap manufacturers have too.

The smaller engines used in economy cars are less expensive than V8's of course, but they're used for longevity as well as efficiency. The 4cyl OHC still only uses a single cam and even the two in a DOHC version is going to use to rather tiny cams. Keep in mind, the small engine is better on fuel and not so highly expected to perform well. That is to say, when you think of V8 performance on a high end and you generally DON'T think of a 4cyl. in it's place.

 

[a trail rider]

Its a 3.4L 60 degree V-6 in the same engine bay that will fit a 5.7L 90 degree pushrod V-8.

Yes, but the 3.6L needed less than 5yrs to see the power it took 15yrs to get from the tried and true SBC from the factory.

How many FWD 4.6L DOHC fords are there? Zero?

Zero today, but they have used it in a FWD platform(Continental)... Then they remembered RWD is superior and stopped all that. Ford also used a DOHC in the SHO Taurus.

A DOHC 4.6L is the same width as a Boss 429.

Well... The 429 worked!:biggrin: The 4.6L is more efficient and cleaner though!

The Ferrari example is a bad one. Take out the engine and there is much more room width wise in Ferrari engine bay then there is in a new Z06 engine bay, and yet, the ZO6 engine has a larger displacement. The largest Ferraris divide 6 litres among 12 cylinders, so an equivalent width V-8 would be 33% smaller displacement. Ferraris are also wider than a normal car and there is no steering shaft snaking past a mid engined Ferrari.

Apples and oranges.

You're right, it's apples and oranges. That's what this is about though, eh?:wink: There are benefits to each engine and he's looking for input to make a decision. Sounds like a plan from here.

Considering what he wants to put it into, I think his best overall choice for performance would likely be an LSx because it will fit directly and transmissions are available on a whim. Plus, an OHC engine will have fewer performance options readily available and won't be at all cheaper. But then, the oddity factor of an OHC in an F-body is definitely something.

I remember seeing a Cadillac, a DeVille I think, with TWO engines in it... One where you'd expect it and the other in the trunk... It ran 12's! The eye catcher though, was TWO engines!!