Don't worry JPS, I only do this about once a year. You guys can go back to installing heavier rods and flywheels in your "torque motors"...Sorry for all the bleeding sacred cows I left in my wake...
George, not directed at anyone, no worries. BA King, So many parts available for sbc's, simple build with good machine work and decent parts, good heads and right cam will get this tow rig running well and keep the budget reasonable. I've built this same engine at least 15 times, but with old school heads, the only reason I'm not recommending a cam is because the vortecs are so good you can cam it differently than old heads.
350 pistons, turn down the mains on a 400 crank to fit 350 block use short 400 rods SBC 305 heads or Corvette L98 heads Short duration cam [ crower Baja "Torquemaster" ]or RV towing cam HEI with an MSD module long primary Headers The idea is to have as much cylinder pressure as possible at low rpm
Well, there is ONE reason. The 5.7" rod 383 will cost you about the same as the 350, assuming you need to grind the crank and re-size the rods in the 350, the 5.85 rod all aluminum 427 may be slightly more expensive...
So you shift at 3000 rpm at WOT? I think the problem with that will arise when you expect the guy in the other lane to do the same... And BSFC numbers at WOT at a given rpm do not necessarily correlate to increased fuel efficiency at part throttle at that same rpm, so that assumption doesn't hold water either. BSFC numbers indicate pounds of fuel consumed per hp produced per hour, they indicate that the engine is making more hp per lb of fuel used at a given rpm at WOT. It IS a good indicator of combustion chamber efficiency, so that may not be surprising, since the mild motor is using vortecs, and the other motor is using an aftermarket head. Whether or not that corresponds to what happens at part throttle depends on many other variables, including manifold design, booster venturi design, and on and on. As a matter of fact, booster design, and in particular, how well any given booster works with the intake manifold design, will impact part throttle fuel economy more than factors that influence BSFC numbers at WOT. There no direct correlation between a low WOT BSFC number and improved part throttle fuel economy at the same rpm, and the reason is quite simple, you don't need ANYTHING close to the total amount of power your engine is capable of making at cruise rpm to keep it rolling down the road at any steady legal speed, even if you drive a Prius.
Still getting 33mpg with the 2.4, 51 with the 1.9, and 28.5 with the 5.0. Must be doing something right. And NONE of them have carburetors.
Always a concern- budget? What many have said 383, vortec heads, port match intake & exhaust, small port cleanup under the values, good headers & torque cam. Now add a blower with some boost at torque peak. Also need rear gear to get moving & overdrive trans for MPG on the highway. Torque peak will depend on rear gear ratio, all trans ratios, tire size and average speed, any hills, lots of stop & go? Lot to consider.
Anybody want to go back and actually look at the two dyno sheets I posted, and think about how it is that an engine that makes peak power at 6300 rpm just flat BURIES an engine with a 3400 rpm torque peak at every point from 3500 up? Theres something to be learned here, for those who want to learn something...
---I will need to call my machine shop / engine builder after reading so far. On my circle track race 400 he installed 6 inch rods . But on my 400 powered junk haul truck he said the 5.5 length rods would give me a lot better pull from idle to the way less than 4200 I drive . . Fill me in guys.. Thank You..
I will bite. I have been following along, and your post with manifold vacuum at peak torque left me puzzled, so I was gonna hold off on opening my mouth. But I want to learn, so here goes. I see the lower hp "torque" engine is using a 650cfm carb and has a much higher manifold vacuum reading than the all out hp engine with 750cfm carb. Is the manifold vacuum higher in the lower performing engine because it is lacking airflow? Something having to do with volumetric efficiency also?
Thanks for all the great information. You hear a lot about Hp and torque but I think few know what they really are or do for you. Myself included.
Well what you should do it buy a crate motor and send me all your small block parts. So you want to build a stump pulling small block. Hmmmmn I am not sure that can be done. A lot depends on what you have to work with but just a quick idea, large exhaust valves even if you can't swing larger intakes. Gentle cam shaft like a 300-350 HP cam if you go GM cam shaft. As much compression as your heads will allow. keep your quench relatively tight like in the .038-.040 range. That is just off the top without building your entire mill.
We may be getting ahead of ourselves here: 1) How much weight are we talking about both trailer weight and total GCW (truck and trailer)? 2) What type of trailer, open or enclosed? 3) What vehicle will the engine be going into?
86 Suburban, 18 ft open trailer.Its off topic so i didn't post what it was. but to keep it close to being ok,i'll need a motor in my 59 el camino. the el camino which i drive alot, cruises at 2600rpm at 70-75. elky has saginaw 4 speed and 3.08 rear gears. I think i know which way i'm going here.
Yeah, that's got me thinking too. High vacuum means some kind of restriction in the intake. Low vacuum means no restriction. Am I on the right track? Mild motor has smaller carb, Vortec heads, no mention of the manifold. Higher HP engine has single plane manifold, I'm going to guess this is showing how the smaller intake limites HP by restricting flow at higher rpm's.
Agreed, a flywheel is an energy storage device, though I kinda like the capacitor analogy, not bad at all. Flywheels do not add power or torque, ever, that is correct. But heavy flywheels are used in low rpm applications requiring a lot or torque, like that Cat 3406 posted earlier. How heavy do you think that flywheel is? You probably would not be picking it up by hand to install onto the crank, that's what cranes are for. In fact, because a flywheel's job is to temporarily store energy, that means that some energy that could be available to power the wheels is instead "diverted" to the flywheel, meaning it's robbing the engine of power; until it's needed and released again. That is the whole theory behind flywheel engines. Check out the video, think these engines have much torque?
Correct. I can check that companies website, those dyno sheets are for crate motors. If you look at the two engines, the big engine has a 750 and makes peak power at 6000, at which point it is pulling .9 hg. The smaller motor peaks at 5000 and is running a 650, yet is pulling 1.6 hg. My guess is the mild motor is running a divided plenum dual plane, in all likelihood, a Performer RPM, so it has a full plenum divider. Any given cylinder in the firing order is only able to use half the venturi area of the carb. The higher hp engine is running a single plane, so any given cylinder in the firing order is seeing all four venturis. If we apply the famous formula to these two engines, it tells us the milder engine is more over carbureted that the high hp engine, but we can see by the peak power vacuum numbers on the dyno that in fact. the OPPOSITE is true, and that in fact, the mild engine is substantially undercarburated. The "formula" says the mild engine needs a 554 cfm carb, so according to the formula, the mild engine has a carb that is 17% "too big". According to the formula, the high hp engine needs a carb of 664 cfm, and has a 750 cfm carb, so the formula says the high hp engine is overcarburated by 12%, yet, in actual fact, the mild engine shows almost twice the inlet restriction of the high HP engine. Theres a reason why when chevy used the Z-28/LT-1 intake, they ran a 780 on it. Its entirely possible that Detroit automotive engineers know a little more than automotive journalists...
Had over 100k on my OT Camaro when I gave it to little brother- .30over, 5.7 rods, hyper flat tops, reworked/ported GM heads, antique Edelbrock intake, customized quadrajet, 280H magnum comp cam, double roller chain, almost no vacuum, Th350, 3000 stall, 3.23 gears. Car was a terror when I built it in the late 80s, it liked to try to wheelie & throw the drive shaft out from under it and break things when I ran 50's on it. With 70s it was very streetable(big clouds of smoke). Made a lot of new, shiny, car guys really unhappy with it. Gobs of torque, decent gas milage. Motor/car is still running strong, a friend of ours stuck a little Wieand on it & turned it into a drag car after he bought it. Went aluminum heads & 305h magnum, roller 1.5/1.6 rockers on my current one, even stronger- a lot more motor than my coupe can hook up without slicks, which is good- I'm to old now to spend all my time repairing driveshafts & u joint, body damage. Dad always says that back in 58/60 when they were dumping their flatheads for the new small blocks they'd have killed to have had the parts/knowhow/ability to build one. Only version he prefers to the 327. Hard to beat a 383 that's built right for the bang for the buck
Ya think! As much as I have enjoyed (and learned a lot from) car rags over the years; the one thing that has always stuck in my memory bank is something that an older guy told me when I was in my mid teens. He said: don't believe everything you read in the magazines.
But lets be clear, they don't have a lot of torque because of the heavy flywheel. but yes, I can agree with everything you have said here. Theres an acronym that gets handed around by engine builders, its P L A N. P is for pressure, increasing the push on top of the piston, and ultimately transmitting that push to the crank pin L is for length of the stroke A is for area P is pushing on, in other words, the size of the piston N is for number of pulses, either more rpm, or build a two-stroke If you aren't doing one of these 4 basic fundamental things, you aren't increasing power, whether the units you use for measuring it are ft lbs or hp doesn't really matter. Anything relating to burning more fuel falls under P. Air flow is needed to support combustion of fuel. Rod length can have a VERY small effect on how force is transferred to the crank pin, and in certain cases (like an engine with a large piston dome)it will also affect the quality of the burn in the chamber. Rod length does not change average piston speed, but it DOES affect peak piston acceleration and WHERE in the stroke the pistons speed is higher or lower. In relative terms, a shorter rod will move the piston faster at the beginning of the stroke. The longer rod accelerates the piston faster in the middle of the stroke. Think of this in terms of how it will relate to choices you make regarding port volume and LSA. This is why Kasse builds short rod motors for the EMC. If you look closely at his combinations, especially prior to the artificial compression limits were put in place by Emap, they all use relatively large open chambers with relatively large piston domes, and R/S ratios that are on the short side. So what he is doing is using the short rod to get that big dome down out of the chamber and out of the way of the burn relatively quicker than a long rod combo would. There are major downsides to this, especially relating to bottom end stress and longevity, but for the narrow purposes of the EMC, they are non-issues. You will also see relatively short R/S ratios in modern NHRA Comp eliminator motors, for the same reason. Don't really want to get into a long argument about R/S ratios here, but had to mention it to explain how rod length can have a small effect under "P". L is self explanatory, as is A. N for number, airflow and the quality of the burn fall under here, if you cant get air/fuel into the motor, and ultimately burn it fast enough to support the increasing rpm, power will fall off, and there is no point in spinning it any tighter. Some are going to notice there is one thing missing here and that's friction, in whatever form. In the strictest sense, reducing friction doesn't "make" power, it conserves the power you have made, leaving more of it available at the end of the crank, rather than using it up making everything turn. The above applies to all engines, used in whatever capacity, whether its running at one steady rpm powering an irrigation pump, or accelerating your hot rod as you pull away from a light. When we start to talk about accelerating an engine rather than running it at a steady rpm, we also have to use some of that energy to accelerate the mass of the components of the reciprocating assembly(rods, pistons, end of the crank throw). That energy isn't available at the end of the crank to be applied to accelerating your vehicle, its being stored in the reciprocating assembly and flywheel. A heavy reciprocating assembly will not show a power loss in a "step" dyno test (where the engine is held at a steady rpm while a power reading is taken) but it WILL show as a power loss in a "sweep" test(where the dyno accelerates the engine through its power band, the same way you are going to actually use the engine in your car). This started when I read something on here that was just complete bullshit, and I just wasn't gonna let it stand, because I honestly don't want to see people misled. It kinda took off from there, because hell in for a penny, in for a pound. The real purpose of all this stuff I posted is to encourage guys to actually think about this stuff, and do some research. Rather than just accepting whatever gets passed around, think about it, and question it. Hell think about and question what I say. Its just there so much bs passed around, like the inherent "superiority" of torque vs hp, when they are actually just two different units of measurement for the same thing, or the carb formula, which, in reality has no scientific basis, and is based on the premise that taking the swept volume of the cylinder, multiplying it by rpm, and comparing it to a cfm number generated on a flow bench at an arbitrary pressure drop has some relevance to the airflow requirements of a running engine which may have any number if different intake manifold designs on it.When you consider that those m numbers are taken on a flow bench at 1.5" HG pressure drop, it becomes clear to any goddam fool that what the formula ACTUALLY calculates is how to select a carb that will generate a 1.5" HG intake manifold vacuum reading at peak power, ASSUMING YOU ARE RUNNING AN OPEN PLENUM INTAKE DESIGN, which 98 % of you are not. And a 1.5" HG vacuum number constitutes a major inlet restriction in the first place. I have gone on long enough, so I wont go into how they came up with 1.5"hg as a number in the first place, but it has nothing to do with engines, and a whole lot to do with the testing capabilities of Smokeys flow bench that he and Murray Jensen developed the original holley 4 bbl on in the mid-fifties. For those of you that are pissed off by what I've posted, well, hell you probably think I'm an idiot anyway, feel free to carry on the way you were before I started typing all this stuff, it wont hurt my feelings one bit. If I have made one or two guys think a little, and I think thats the case, well, I'm a happy camper. I have never had an original idea in my life, theres guys way smarter than me that do that. I just don't blindly accept whatever I'm told, I try to cross-check it with reality, and if it doesn't stand up to track times, dyno results, or observable repeatable real world results (like the carb formula) I sit down and try to figure out why. Climbing off the soapbox now.
Sorry, I have to go back and keep editing the spelling, My MORONIC new computer keeps thinking it knows what word I want to use better than I do, and changing words like "venturi" to "venture" and other idiotic crap. Sweet jesus, what it this world coming to??
These guys should read Tex Smiths new book, especially the chapter on Hot Rod magazine, and the part about the changes to the nature of the magazine industry in the last few years.
The Jalopy Journal
