7 L displacement, 12:1 comp, hp/tq Ratio ???

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Wild302

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#1

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I was wondering.

How its possible for an engine to have a such hp/tq ratio like 430 hp @ 460 tq when this engine have a 12:1 compression

its for a 7000 cc displacement

normaly at this compression, th hp is a LOT higher then torque no?

i need to know that for my personal knowledge =)

can someone explain me?

 

giddyup306

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#2

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Yes. Need to know more bout the engine tho....

 

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Wild302

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well its the 427 cid ZL1 that was on Yenko 69'

thx alot if u can explain me!

http://www.gearheadracing.com/Reference/Chevy/1969ZL1Camaro.htm

 

giddyup306

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It doesn't have a very long stroke (acts as leverage with a longer stroke). A 393W has .009" longer stroke than it. I also don't know what length the rods are. Also I have no idea what the rotating weight is of the engine (also a factor of torque).

 

90mustangGT

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Horsepower is just a measure of torque in relation to rpm. TQ and HP are equal at 5252RPM For example; Lets say it puts down a peak TQ number of 460TQ but can maintain 430TQ at 5252 before dropping off, then it will have 430HP. It's mathmatical, and I am not, so that's all I can confindently tell you, because it is hard for me to put it in type.

 

giddyup306

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90 is right. HP and TQ are inversly proportional. Other than using a formula you cannot measure horsepower. You can however measure rotating force on an axis (torque) then use the formula to get hp.

 

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Wild302

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ok thx i understand a lil bit better.

but Why the TQ is higher then HP with a high compression like that?

sry for my english

 

giddyup306

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I just noticed I missread your queston. I thought you were asking why it made so little torque. Big blocks typically make more torque than horsepower. Even lots of small blocks. Compression generally gives more tq than hp.

 

90mustangGT

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Honestly, forget PEAK numbers. I don't even look at them anymore. Look at the torque curve through the rpm range. You want the most average torque across the range in which you will be driving in .Horsepower sells cars, Torque wins races, and that is partially true.

Big block, small block, high compression, low compression, there is so much more to do with it.

 

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Wild302

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90mustangGT said:

Honestly, forget PEAK numbers. I don't even look at them anymore. Look at the torque curve through the rpm range. You want the most average torque across the range in which you will be driving in .Horsepower sells cars, Torque wins races, and that is partially true.

Big block, small block, high compression, low compression, there is so much more to do with it.

Click to expand...

I like your answer! your damn right!

 

Michael Yount

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First off - if you're gonna take a serious look at the physics of how a certain torque/hp curve came to be, I suggest that some 'real' data be obtained. Your numbers sound like the advertised data. In 1969, advertised HP/Torque figures were more a matter of 1) the advertising/marketing groups, or 2) trying to squeak past NHRA's hp-to-weight class groupings. Those numbers have little basis in reality. The ZL1 was an all aluminum big block -- and EXTREMELY rare - only a handful were sold. It likely made WAY more HP and torque than those numbers indicate.

As others have said - a lot of different physical factors involved - bore and stroke of the engine, rod to stroke ratio - but perhaps most importantly is how the intake/exhaust/camshaft work together and where the power is produced. The further up the rev range that peak power occurs in a naturally aspirated engine, the more likely that the peak HP number will be bigger than the peak torque number. The further down the rpm range - the opposite is true. It can vary more with boost - but in general, you often see the same dynamic at work. Those built to wail at high rpm usually have a higher HP peak number than torque. Diesels are a great example of the opposite -- the pickup diesels don't rev much beyond 3000 rpm, and have stock numbers with torque peaks almost twice that of the HP peak.

 

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proxses

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Were did those numbers come from?
It could have been as simple as not revving the engine very high.
The 430hp number could have been obtained when they stopped revving the engine.
Such as:
They tested the engine from 3000 to 6000 rpms, just as an example.
And in this example, the engine made, lets say, the 460lbs of torque at 4500 rpms, and the hp peak occured at the 6000rpm dyno cutoff.
There may have been more power, the dyno operator just stopped revving the engine.

Just an idea....

 

Funanin

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#13

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unless it had a cam that was so radical that it was like blob blob... blob when the motor ran, it would have ran out of power long before 6k. Big blocks usually make their power lower because they dont have variable valve timing or any of that crap that ricers have. The reason I was thinking that was because they dont sell brand new cars with super high duration cams or the rich idiots that buy them wouldnt be able to drive it off the lot.

 

hllon4whls

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Under rated for insurance reasons. Happened all the time!

 

Michael Yount

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Proxses/funanin - do you guys know what a ZL-1 all aluminum 427 from the late sixties was? Have you ever heard one run?

The ZL-1 was modeled after the infamous L-88 427 - it was cast iron block/aluminum heads, high compression with a wicked long duration, high lift solid lifter cam. While rated at 435 HP, most believed it actually put out 500+HP.

The ZL-1 had an aluminum block with extra material for extra head bolts, an even wilder solid lifter cam, 12.5:1 compression ratio, Holley 850 double pumper -- most folks believed it made anywhere from 25-50HP MORE than the L-88. It is EXTREMELY rare - only a handful remain today, and the numbers are sketchy over the years (GM back-door supplied some) but it's doubtful more than 50 ever hit the streets. A COPO ZL-1 in ANYTHING from back then fetches well into six figures. VERY expensive today. If you get the chance to hear an L88 or a ZL1 run today - give a listen. It sounds like the god of hellfire himself has come to life in the engine bay. And if you think it sounds good at idle - you ought to hear them at 6500-7000 rpm - it's music boys. And yes - they will rev and make power up there.

 

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Wild302

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#16

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These number come from the dealer ship in 1969, i got them in a AMerican muscle car episode on speed channel

Damn guy, i enjoying reading your answer! my 18 year old head learn a bunch! =)

 

giddyup306

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#17

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Michael brough up a good point about the cams. Even if the site had the cam specs it would more than likely be the advertised duration (@.012") when the vavle firsts starts to open. That dosen't mean squat. Not all 292 or 260 (or whatever) cams are the same. The only way to get a somewhat accurate guess as to how the cam is going to perform is @.050 duration. From there you can say "wow this cam is a radical bastard" or you can say "wow this cam is a turd".

 

Michael Yount

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#18

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Giddyup - the majority of advertised durations are at .006" or .004" lift - although Crane does show some funky stuff at .012". While the standard is .050", the other thing that makes a big difference is whether it's flat tappet, hydraulic roller or solid roller. The ramp rates (steeper lobe sides if you will) for each get steeper. So the gap between advertised durations and .050" durations grows depending on the type of lifter. Most of the old muscle car engines were solid or hydraulic flat tappets, so the ones with really hot cams had a lot of advertised duration. Since the ramp can't be as steep, if you want it open to a bigger lift, and you want it open longer at .050", you've got to start opening it (.006" events) MUCH earlier.