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#21
11-19-2009, 12:16 PM
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The original post never asked "which is faster"...only what mods might he try while keeping his car streetable.
Nothing a good reading comprehension course couldn't clear up. Closet chevy guys are always trying to turn these discussions into "rpms win races" rants. |
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#22
11-19-2009, 12:33 PM
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__________________
 John J.  
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#23
11-19-2009, 12:54 PM
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I will tell you this from experience, then you take what you will from it.
My 1967 Coronet made an honest, dyno-verified 375 HP and about 450 lbs/ft of TQ. It was totally uncontrollable on the street when you got on it. You could not put the power to the ground, even with wider tires. The car felt absolutely great and had immense throttle response and horsepower, much more than I was ever able to harness, even with 28"x7" slicks. When I sold it in 1990, I warned the new owner that it was a wild car. He laughed and told me that he had a 455 in his GTO and I had no idea what 'torque' was. He lost control of the car a block from my house and jumped the curb with it, bnding a tie rod and a wheel. As far as I am concerned, I have no need or want of anything more than this HP/TQ value in a street car, even for Autocrossing or mild Road Racing on weekends at Willow Springs. Additionally, one should also be mindful of the TQ limitations of the 10 bolt/12 bolt differentials. To those that thing rpm doesn't win races, you are sadly mistaken. My 302 CID SBC put a lot of 455's/454's/440's on the trailer at the track. Now, it was less than ideal as a street car, but it was unreal quick. In a conversation with David Reher, he pointed out the same thing about his high-winding 302 he had in his younger days; the bigger inch cars could not compete with the rpm capability of his Camaro. David told me something that really stuck with me: "Times sure have changed, but the guys who can't tune are always better off with a big cubic inch engine. It's just easier to make power that way." I couldn't agree more. If you want to learn about tuning and longevity, hang out with the oval track guys. If you think that shifting at 5500 is an awesome display of knowledge, try tuning 6500 or 7500 all night long season after season. That's one thing that we have always done here is use road race tactics and experience on every engine we build, even the average street motor....longevity. I don't like how the long stroke Pontiac motors feel. I have built them, I have driven them and I have tuned them for others. You can talk toruqe and low rpm all you want and if you like how it feels, then that's great. The 3.75" stroke is ideal and the 400 CID Pontiac is a great and versatile engine. Personally, putting all your cubic dollar, aluminum head/SCAT crank bull**** and 'bigger is always better' theories to rest, my favorite 'feeling' Pontiac of all time is the 389 with a 4 speed. The throttle response is fantastic, just the right amount of torque and overall, a very balanced engine. Last edited by Z Code 400; 11-19-2009 at 01:02 PM. |
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#24
11-19-2009, 02:42 PM
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Let's try to get this back on track for the OP. So based on his comments, we know the OP wants to lift the hood and have it appear basically stock. No headers, so that will dictate how far he can he can take his combination. In that regards, I'd focus on the cylinderheads, and I'll explain why, after. If he was to get the heads redone by a professional Pontiac porter (SD Peformance is my choice) it's possible to improve the mid-range and upper range power with minimal to no impact to the lower range. They can CNC port the heads and shape the runners with minimal material removal to significantly increase flow without sacrificing velocity. They can also elongate the pushrod holes so that 1.65 ratio rockers can be used. And finally, they can fill the exhaust crossover to keep the heat out (you might need an adjustable electric choke to compensate for warmup). It would also be good at this time, to mill the head surface for trueness (slight increase in compression depending how much needs to be removed). You can also send SD Performance the intake at the same time, so they can gasket match to the cylinderhead port. Then I would measure the how far the highest piston edge of all 8 cylinders fits in the bore. Find a compressed gasket thickness which, in combination with how far the piston sits in the bore, keeps the head surface less than .05" from the piston. This would slightly increase compression, but the reduced quench distance will help detonation. Now install 1.65 ratio rockers with the camshaft you're using now. Why not focus on the camshaft? 1. Focus on the cylinderhead will allow for more potential later on. 2. Cam will move the peak torque and hp. The cylinderhead will mainly affect the mid and upper range. 3. Depending how far he wants to go, a roller cam might be a better future choice (but it's expensive). Why buy a larger camshaft and then decide on a different one later? So between the 3, spending the money on heads first would give him a better foundation to build on later, but still be compatible with his existing combination. Plus by going with an increased rocker ratio, he'll still see some benefit on the mid-upper range from this again without impacting torque. An he can reuse the rocker arms with the next cam. As far as exhaust, in addition to the RA manifolds, use mandrel-bent 2.5" system with an x-pipe for maximum scavaging. This will work well with the head changes and also with a future camshaft change if the OP desires. After this is said and done, the stock carburetor will need to be recalibrated. The timing can also be optimized, but it won't require as much recalibration as say you would when changing camshafts. You'll have fresh heads, much more power, and a very driveable combination with room to grow later on with the cam change. Once he does decide a cam change is necessary, then we'll need the trans type, torque convertor stall (if applicable), rear gearing.
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"The Mustang's front end is problematic... get yourself a Firebird." - Red Forman |
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#25
11-19-2009, 02:45 PM
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I would suggest a Cliff tuned Q-Jet and Distributor. The 2.50" RA manifolds would be a very good choice. An excellent choice when mated to a 2.50" mandrel-bent exhaust system...Internal modifications in your plans?????.....Robert |
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#26
11-19-2009, 02:52 PM
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I would also recommend he purchase Jim Hands "How to Build Max Performance Pontiac V8s" book, and Cliffs book on Qjets.
__________________
"The Mustang's front end is problematic... get yourself a Firebird." - Red Forman |
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#27
11-20-2009, 06:00 PM
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In a general true statement - MAKE THE MOST POWER WHERE YOUR ENGINE SPENDS MOST OF ITS TIME!
For example having a ton of power at 6000 RPM does NOT do you any good IF your engine NEVER hits 6000 RPM. i82much is totally correct in post 12. 500 ft.lbs at 3000 rpm? Your car will MPH and ET like one that had...about 285 Horsepower. (Torque * RPM) / 5252 = Horsepower comparing From the example in post 8, 350 lb/ft@6000 is almost exactly 400 Horsepower, IN A RACE an equal weight car will smoke the above car with 285 Horsepower PROVIDING you actually put the 400 Horsepower to the ground with the right gears and traction! ALL ET calculators ask how much HORSEPOWER (not torque).. WHY? http://www.wallaceracing.com/Calculators.htm The RIGHT answers from TOP Pros here: http://speedtalk.com/forum/viewtopic.php?p=51941 Particularly notice posts by maxracesoftware and Darin Morgan. quote from Darin's March 23, 2007 post on Tq VS HP~ ---snip--- Has any one here ever heard of "PLAN"? this the recipe for power, period, there is no other. P = pressure ( BMEP ) L = length of stroke A = Area of the top of the piston N = number of power pulses ( RPM ) Using this recipe you can define how your going to go about producing more power. (P) You could increase VE and increase BMEP (L) Increase stroke length (A) increase bore size (N) increase RPM ---snip--- ------------------------------------------------------------------------------ I do NOT see "Torque" mentioned in the above formula! While the "common man" formula is (TQ * RPM) / 5252 The PLAN concept is BETTER.. why? The other formula somehow suggests Torque comes first and is more important.. and confuses the hell out of some. Reality.. tq and hp are the same thing expressed differently. BOTH Torque AND Horsepower are derived from CYLINDER PRESSURE! Here is more specifics on the PLAN Formula: http://www.maintenanceresources.com/...inebalance.htm Mean Effective Pressure (Horsepower) One horsepower is the energy required to lift 33,000 lbs of weight one foot in one minute. It is numerically expressed using the formula: Horsepower = P L A N / 33,000 Where: P = Mean Effective Pressure (MEP) L = Piston stroke in feet A = Area of piston in square inches N = Number of power strokes per minute Once installed in an engine, the piston stroke and area are fixed. Leaving horsepower as a function of mean effective pressure (hereafter referred to as MEP) and engine speed only. --------------------------------------------------------------------------------------- QUESTION FOR THOUGHT? why in ALL forms of competitive (balls-to-the-wall) Racing does everyone REV their engine as high as the parts will allow?! maybe they like the sound?  Pee-Wee Herman also really peddled that bike like crazy...  Get your head out of the sand.. |
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#28
11-20-2009, 06:39 PM
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Indeed, the Chef makes some good points. In a street car, as I had previously posted, even 375 HP and 450 lbs/ft of TQ is a real handful. So, the intended use of the car and the strength of items like rear axle and transmission must also be considered.
I have found that keeping DCR right at 8.00:1 will afford good power and excellent octane tolerance. To arrive at this figure, you will need to know all of your critical component data, including camshaft valve events, rod length, bore, head gasket thickness and stroke. However, unless the original poster planned on tearing the engine down, most of these calculations would be utterly useless to him. With an assembled engine, first making subtle changes to exhaust, ignition and carburetion would be a wise choice...Robert |
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#29
11-20-2009, 07:17 PM
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What I meant by 500ft/lbs at 3000rpm versus 350ft/lbs at 6000rpm is that in the real world with those peak torque levels is that the 500ft/lbs at 3000rpm would be the better street car with better driveability.This is just talking Pontiac engines.
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#30
11-20-2009, 08:17 PM
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Performance fundamentals.. for a given displacement, usually making more power higher in the RPM band will also reduce idle quality, vacuum etc The worst of BOTH worlds would be building a "RACEY" engine with mismatched huge cam, intake, and heads NOT even making the Horsepower it should and installing it into a car with stock gears and torque converter. Drives like crap, makes alot of noise and doesn't go anywhere fast.. unfortunately a large number fall into this trap to some degree. Last edited by pastry_chef; 11-20-2009 at 08:27 PM. |
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#31
11-20-2009, 09:01 PM
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Like the common and indiscriminate installation of the '041' cam into a low SCR engine and widespread use of the '068' as a 'universal camshaft,' without any consideration to SCR, application and/or gearing...Robert |
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#32
11-20-2009, 11:02 PM
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__________________
John J.
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#33
11-21-2009, 01:38 AM
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I guess I will stick to my slow 500ftlbs at 3000rpm and 285 hp?Sure feels nice on the street good thing I don't take it to the track!
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#34
11-21-2009, 06:03 AM
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Does an engine have Horsepower at 1000 RPM.. yes Does an engine have Horsepower at 2000 RPM.. yes.. and everywhere else If you rev your engine to 6000 RPM, do you have torque there.. yes The original poster created the title "horsepower suggestions..." then a few said, don't worry about horsepower. Maybe his redline will be 4500 RPM.. if he desires to go as fast as that will allow him, he WILL desire to maximize HORSEPOWER where his engine spends its time! Whatever RPM that may be. Torque does NOT do work.. you cannot do work without RPM. As soon as you have RPM, any RPM.. you have HORSEPOWER. To get more horspower you can 1) Increase Engine size 2) Increase cylinder pressure .. usually by improving efficiency 3) Increase the RPM where the engine makes its best cylinder pressure To actually apply number 3 in a car, you will need to have proper gearing and torque converter (for automatics) to maximize time spent in the engines efficient RPM range. |
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#35
11-21-2009, 06:13 AM
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And I'll keep my (greater than) 350 foot pounds at 6000RPM. Seems to go down the road just fine, and if for some reason I need more REAR WHEEL TORQUE, I'll just downshift.
I just don't know why you need or desire so much torque down low. It's only making 500 foot pounds if the car is floored, and outside of the initial launch, are you ever going to see 3000RPM again? Nope... and if hes looking for more power, I doubt it's to just keep on cruising at the same speed he would have with a stock motor. Too ba dthe OP hasn't come back tog ive us details sow e could argue about cam selection.
__________________
'73 Formula 400 Cammed LS1/T56/3.73's 12.92@106.04 2.03 60 ft. <~~ Bone stock LS1 with 4L60E/3.08's Went 12's in pure daily driver trim! A/C, leather power seats, power steering, full stereo, sound deadening, power windows, full suspension, true street tires, power 4 wheel discs, and 25MPG! |
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#36
11-21-2009, 08:44 AM
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Nothing worse than an overcammed, rough idling engine that makes all it's power in the high RPM range.
My engine builder asked me "Do you do most of your driving in the 5-70 MPH range? Build your car to be a stop light terror!" That means the power is in the low to mid RPM range. You should use a Q-jet, optimized the ignition, good exhaust, and have the cam sized so you have vacuum in the 14-16" range. An efficient set up and low gears works great on the street. |
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#37
11-21-2009, 10:15 AM
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[QUOTE=FLYNLOW;3825354] I'd much rather have 350 lb/ft@6000 than 500@3000. This article is still a great way to read about "torque vs horsepower" as they are one and the same. http://www.vettenet.org/torquehp.html Alright... first and foremost. Whats your budget? Your mechanical ability? Performance goals?[QUOTE] DID YOU READ THE WHOLE POST IN THE LINK? Comment by Thomas Barber in the link: [QUOTE] Over the past decade, I have encountered any number of articles, on the Internet, that endeavor to explain torque and power. One of those articles, authored by a fellow named Bruce Augenstein, has appeared on dozens of independent Web sites, and seems to have had a strong influence on the popular understanding of this subject. Regardless of his intentions, his article has promoted several fallacious ideas, along with a dubious overall understanding of the subject. Before we look at what he wrote, it will be helpful for us to begin by identifying specific criteria that are useful in assessing the merit of his (or any other) effort to explain this subject: * Foremost, the explanation should articulate the essential fact that acceleration at any time is proportional to power, along with the essential fact that the acceleration associated with any specific amount of engine torque, depends on the engine speed. * Regardless of whether the explanation articulates those essential facts, it must not espouse any fallacious notions that are contrary to those facts. * If the explanation endeavors to explain any fundamental physical concepts such as torque, work, and power, those explanations should be fundamentally correct. [QUOTE] Posting up old early 1990s articles on Torque and HP will get you into a lot of trouble these days. There are a lot of sharp tuners like Cliff Ruggles, and others who make excellent power and et with more than 500 lbs/ft of torque and drive their cars on the street and strip. Cliff Ruggles posts on this site too. [QUOTE=FLYNLOW;3825354] "torque vs horsepower" as they are one and the same." [QUOTE] SORRY, I DISAGREE! THEY ARE NOT THE SAME. Tom Vaught
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. Last edited by Tom Vaught; 11-21-2009 at 10:24 AM. |
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#38
11-21-2009, 10:19 AM
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Well let's give the OP a real answer. I assume that's a stock bottom end with stock rods, maybe he's going to shift at what, 5500 RPM? A stock-appearing combo, but maybe it doesn't have to sound stock? I think he was on the right track w/the RA manifolds and 2.5 exhaust, stock intake, and Q-jet.
Here's my advice to the OP. IA2 block, Edelbrock or High port heads, 2" headers, a big holley and a solid roller. It will look plenty stock - just keep the hood closed
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#39
11-21-2009, 11:25 AM
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Here is a prime example between two different engines with completely different torque curves.
Engine A in second gear (1.98) with a 3.23 rear gear and 26.5" tire. 2000 464 lb-ft 176 hp 24 mph 2967 RWTQ 2500 482 lb-ft 229 hp 30 mph 3082 RWTQ 3000 496 lb-ft 283 hp 37 mph 3172 RWTQ 3500 511 lb-ft 340 hp 43 mph 3268 RWTQ 4000 506 lb-ft 385 hp 49 mph 3236 RWTQ 4500 481 lb-ft 412 hp 55 mph 3076 RWTQ 5000 427 lb-ft 406 hp 61 mph 2730 RWTQ 5500 363 lb-ft 380 hp 67 mph 2321 RWTQ Engine B in second gear (1.98) with a 3.73 rear gear and 26.5" tire. 2309 410 lb-ft 180 hp 24 mph 3028 RWTQ 2887 430 lb-ft 236 hp 30 mph 3175 RWTQ 3464 460 lb-ft 303 hp 37 mph 3397 RWTQ 4041 465 lb-ft 357 hp 43 mph 3434 RWTQ 4619 465 lb-ft 408 hp 49 mph 3434 RWTQ 5196 445 lb-ft 440 hp 55 mph 3286 RWTQ 5773 390 lb-ft 428 hp 61 mph 2880 RWTQ 6351 330 lb-ft 399 hp 67 mph 2437 RWTQ Two identical cars (except for engine and gears, same weight) are moving along at a steady 24 mph in second gear side by side. They both punch it at the same exact time. Which one will pull ahead immediately, and get to 67 mph the soonest, and cover the greatest distance in the same time period? The one with the greatest engine TORQUE, or the one with the greatest engine HP?? CASE CLOSED! |
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#40
11-21-2009, 11:38 AM
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