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04-09-2015, 01:49 PM
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What is everyone's engine design preference?
What type or design of engine do you prefer, and why?
Inline six because they are smooth and balanced?
Undersquare for n/a efficiency and torque, versus oversquare for boost and high rpm's?
V8 for that all American thumpy idle, or V6 for the packaging?
What engine type do you prefer, and why?
Also, is there a particular design that is better suited for road racing/pro touring? I know that transmission choice and gearing can be tailored to keep any design of motor in its optimum operating range, but is there a good reason to choose a high revving, oversquare, turbo motor over an undersquare stroker with a positive displacement blower?
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04-09-2015, 02:05 PM
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I would have to say that, on this site, you are going to find mostly V8's for sure. The LS series specifically... they are everywhere, engineered well, parts are available, etc etc etc...
I plan out what my goal is with the vehicle, what I want. I have a '50 Chevy 3600 that will have an inline 6 with fuel injection, well hidden. The idea is an old vehicle with (well hidden) new design. IRS, IFS, etc etc...
I have a '47 that will get an original inline 6, no custom anything. That vehicles a restoration.
I have an '84 Camaro that will be getting a 6.0 LS. It will be boosted (LS's have very strong rotating assembles) and a power house.
I have an '85 C10 that will be getting an inline 5 cylinder. It's more of a "look at me" vehicle, so the originality of a 5 cylinder will fit perfectly with the extreme lowering and custom interior.
So yeah... I'd say match the engine to the design of the project. However, on here, I'm going to go out on a limb and say the LS V8 will be the engine of choice on most builds.
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04-09-2015, 02:09 PM
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PS. It seems that a lot of people slap in an LS engine "because it works" and call it good. But I asking more of a preference towards one design theory over another, and for what reason.
Example:
I want to build a 359ci LC9 stroker with stock 3.78" bores and a 4" crank. This makes the motor undersquare. The tall, narrow cylinders are better air pumps for naturally aspirated applications, and the long rod design reduces piston speed towards top dead center, which reduces the likelihood of detonation. This should allow for higher compression and more timing.
There is more to that, but I don't want to bore you with a pipe dream engine that I haven't built yet. Those are the kinds of thoughts and explanations I am looking for with this question.
I get that a lot of people just use what works, without having a real preference towards how the results are achieved. But I want to build an engine with the theories I, personally, think makes sense to test whether or not the engine performs how I want it to using the theories I want it to incorporate. If that makes sense.
Building the engine as I want it built, just to see if I want the right things... if the theories that make sense to me actually give the performance I want. Otherwise, I have to re-evaluate my understanding of engines, and how they work, and figure out what it is that I am wrong about. Why what I think should work does (or does not) actually work. That sort of thing.
Anyone else building an engine or picking a particular engine using this approach?
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04-09-2015, 03:43 PM
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I know you can take inline 6 off the list for this site...
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04-09-2015, 05:05 PM
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David, I like the way you think. I'm an engine guy myself, and I'm constantly reading and researching whats out there. I feel that this conversation won't go far on this forum, due to the stupid LS platform being so efficient, and the engineers doing there homework so well, that honestly it's a no brainier for the average guy building a car to choose an LS3, or Ls7 for their project.
My Chevelle, when I bought it had a fresh .030 over 350 with a 350 trans, that worked well, but I wanted to drive this car a lot, so the fuel injection and reliability of the LS series engine was calling my name. Yeah it's mainstream today, but I wanted reliability that an old sbc couldn't give me. Been there done that.
In my younger days, I worked at a shop that built Cup engines, back when people actually outsourced objects in Nascar. Not only did we build engines there, but we raced on the weekends. I was able to learn engine formulas and machine work during the week, and then on the weekend apply what I'd learned. It was a great job for a gearhead like myself.
Later on in life, when funds started to get comfortable, I did my own racing venture, running asphalt late models. I built my own stuff, due to what I'd learned from life's experiences. Absolutely priceless. The engine program that I had to run was perfect for this thread. A lot of homework, trial and error, and money went in to making those engines run. But that was racing.
Not to bust your bubble, but the 4" crank you want to run in your LC9 will increase piston speed, and even with long rods, your piston speed will likely be greater than stock. That block will bore out safely over .100, however.
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04-09-2015, 05:26 PM
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I understand what you're saying (although I haven't studied engines enough to get very in-depth, I stick to short stroke=high rpm, long stroke=torque).
I would think you need to figure out the exact purpose of the car. Autocross or road track would be a big one. Then build around that. A high RPM screamer would probably be wonderful for a long road track, not as useful on a short turn to turn autocross track. You'd have to have it at high RPM which would make gearing incredibly important, similar to racing a 2-stroke motorcycle.
I, personally, love the planning stages of the build. It's only limited by your imagination and, of course, budget. The better planned out build will always make a guy happier in the end, when everything is perfect! Plan away!!!!
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04-09-2015, 08:18 PM
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Quote:
Originally Posted by mitch_04
I understand what you're saying (although I haven't studied engines enough to get very in-depth, I stick to short stroke=high rpm, long stroke=torque).
I would think you need to figure out the exact purpose of the car. Autocross or road track would be a big one. Then build around that. A high RPM screamer would probably be wonderful for a long road track, not as useful on a short turn to turn autocross track. You'd have to have it at high RPM which would make gearing incredibly important, similar to racing a 2-stroke motorcycle.
I, personally, love the planning stages of the build. It's only limited by your imagination and, of course, budget. The better planned out build will always make a guy happier in the end, when everything is perfect! Plan away!!!!
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That all depends on the course. The Goodguys layouts generally have 1 or 2 very slow corners so you need to be in first coming out. Unless you are a racing hero (or paddle shifters) you can't shift 4 times a lap, so RPMs are your friend for higher top speeds. I would love to build a high winding small block for my Falcon.
I am working on a model A which I have a DOHC 4.6 linclon motor for. I got some cams and valve springs for it so it should spin up to 7200. Even if it quits making power at 5900, the extra RPM will keep me off the limiter for a couple more seconds.
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04-09-2015, 10:13 PM
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Thanks for the replies. And keep them coming.
I hear you about the long stroke increasing piston speed overall, and I figured that it will still be at a higher speed at TDC, than that of the 5.3 piston. But it's no more than that of the other LS engines with a 4" throw, and people spin them plenty fast without detonation issues. So I think I will be ok there. And, I'm looking for torque, with absolutely not a single care of what the peak horsepower ends up being.
Horsepower sells cars, torque wins races.
-Carroll Shelby.
My focus on torque is what led me to the 359 stroker. I'm not all caught up on big cubes or high horsepower. I want a streetable, fun, torquey motor that meets some simple theory criteria I have put together, namely being undersquare.
I want to stay with the 3.78" bore, instead of the 3.9" bore, because the blocks use the same sleeves, so the 4.8/5.3 sleeves have more "meat" than that of the 5.7 sleeves. So the thicker sleeves will handle the extra side load on the pistons from the increased stroke. And the thicker sleeves will handle boost better (if I can ever afford a W180AX for it).
Or at least that's my thoughts on using the 3.78" bore. Wiseco makes forged slugs for the 5.3 with the correct pin height for use with a 4" crank and 6.125" rods, and all the other parts will be stock LS parts.
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04-10-2015, 12:07 PM
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Interesting thread. At least it doesn't talk about Camaros... yet.
I really became interested in the Nascar stuff after seeing the teams give away their stuff on the used market after their "life cycle" was used up.
But I also wanted/needed something that didn't have to be rebuilt every 500 miles (1 race).
As much as I would love to play with a 9000 rpm motor, I wanted to gain the needed low and mid range torque and bring the powerband down for durability and less maintenance. So a 4" stroke was used instead of the 3.25" that the Cup cars use.
4.170 x 4.0 = 437"
Of course with the small chamber size of the SB2.2 heads (mine are 51cc, many are in the 40 something range) this made piston design pretty much impossible to achieve 11:1 to 12:1 in order to get to pump gas range. So, to minimize the dish in the piston and keep it "acceptable" according to my engine builder we ended up around 13:1 compression. So, the other pump gas came into the picture... E85. Several stations not too far from me. I am good with that.
Even though a .800-.900 lift cam would be right at home with the heads, we decided to use a milder cam (.660ish net lift) with a lower rocker arm ratio (1.7 instead of 1.9 or 2.0). Again, all to keep things lower maintenance.
I really wanted a toned down Nascar motor with all the cool parts and look but not the rebuild cycle. Time will tell but I think we achieved that without giving up the BIG power. In fact the trade off to gain the torque is what I am really excited about.
640 ft #s out of a pump gas SBC. I'll take it.
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04-10-2015, 03:40 PM
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Thank you, Flash. That is exactly the sort of answer I was looking for. I have heard that it is better for the longevity of the valvetrain to let the cam do the work, instead of compensating with higher ratio rockers. That sounds like a nice engine you have put together. 600+ pounds of torque is no joke.
I was also thinking that using the 4" crank, would slide my power band to the left. I might even use a truck cam in it for the initial build. I'm looking for a relatively tame, yet torquey, motor that I don't need to rev the piss out of.
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