While being bored I came across this on HondaMod2 and it’s a pretty good post so I figured I’d steal it and post it here, it actually helped me understand some stuff. 
Q&A on the swap… the real low-down…
All this info was sourced from http://www.distributedworks.com/ind...ce/lsvtec.html, by a member of the Indiana branch of team Sol. Silverkorn had found it and passed it along… I’m just giving credit to the dude who wrote it, as he hits the nail RIGHT onthe head…
ENJOY!!!..
"Why I Dislike LS/VTEC
If it was all that great, Honda would have done it in the first place. Submitted for your approval, my thesis on why LS/VTEC is a bad idea.
What is LS/VTEC?
Why would Honda do that?
What is R/S?
Why a low R/S is bad for reliability
What is power, exactly, and how do Hondas make it?
B Series, by the numbers
How VTEC works, and why it lives at high RPMs
Why it doesn’t all fit together
What is LS/VTEC?
A quick tutorial for anyone who doesn’t already know.
LS/VTEC is using a B18A or B18B block (referred to as an LS block, even though it was found in the RS, LS, and GS) and mating it with any of the DOHC VTEC heads- the B16A, B17A, or B18C. The principle is to use the larger displacement of the LS block (READ: higher torque) and mate it with the high end power of VTEC. I’m also sure you’ve heard of CR-VTEC, which is a very similar idea. It uses the B20Z block of the CR-V (NOT the B20A of the Prelude Si, for reasons that will become obvious later) to achieve the same effect, only on a grander scale. What you end up with is an engine commonly referred to as a “Frankenstein” setup, and it’s all the rage these days.
Why would Honda do that?
So why in the world would Honda put us in such a situation- having to build these incredible motors all by ourselves? Why would they knowingly decrease displacement and torque in a car being manufactured to be faster than its lower-trimmed breathen?
Look at it, too, from a manufacturing standpoint- Honda is already making the higher displacement B18A and B blocks (blocks are identical, only difference was in the head), so why go to the extra time and expense of developing and manufacturing a separate block, especially if it will decrease output?
The answer is easy: R/S.
What is R/S?
R/S is the abbreviation for rod to stroke ratio. It is the ratio of the length of the connecting rod to the length of the piston stroke, or the distance the piston travels from the top to the bottom of its stroke. As the ratio gets lower, the amount of stress on engine internals increases exponentially, killing long-term reliability. The higher the number is, the slower the piston is traveling, killing power output.
The ideal R/S is 1.75:1 (Three cheers for the B16A, at a near-perfect 1.74:1!).
Why a low R/S is bad for reliability
A low R/S means the rod will be closer to a horizontal angle on its upstroke. This means that more of its force will be pushing the piston horizontally, rather than vertically. What does this mean for your engine? Two things.
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There will be more stress on the sides and in the center of the rod, rather than on its ends, leaving the rod more vulnerable to breaking. Picture a straw. This is no special straw, just an ordinary drinking straw. Is it going to be easier to bend this straw by applying pressure onto its ends, or at its center? Now think of your poor connecting rods.
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There will be more stress on your cylinder walls. Once again, the rod is pushing the piston at a more horizontal angle- right into your cylinder walls, rather than up and through them. The risk here is double: A. Putting that piston right through the cylinder wall. B. The cylinder wall will actually flex under the pressure, causing the shape to turn from a circle to an oval or oblong shape. This causes the loss of the seal created by the piston rings. What happens? A small amount of oil could slip past into the combustion chamber. Bad things happen from here: The oil gets combusted, leaving nasty carbon deposits in your combustion chamber and exhaust ports- not a good thing for flow or valve sealing.
It’s also important to note that as the RPMs increase, so does the amount of stress on your engine’s internals.
What is power, exactly, and how do Hondas make it?
Warning: Once you see this, you will never look at horsepower and torque readings the same again, especially after you think about it.
P= (TR)/5252
P= power, in horsepower
T= torque, measured in lb/ft
R= Engine speed, in RPMs
Therefore:
Horsepower= (torque x RPMs) / 5252
Try it- pull out a dyno and see what you get.
So from this, we can conclude that if we increase torque or engine speed, we will get more power, right?
Remember that, it’s important…
Now how do Hondas make power? Our tiny little 1.6-1.8L engines aren’t exactly oozing spare displacement and creating gobs of torque, are they? Hondas make power through revving, and revving high. So why does everyone place so much emphasis on creating torque? It’s because all these bolt-ons you see advertised won’t raise your redline, but they will increase torque. There’s nothing wrong with squeezing every last ounce of torque out of your engine- you should. But trying to get torque from more displacement in a Honda is like trying to fill a swimming pool using a squirt gun. You’ll never get enough for it to be useful.
B Series, by the numbers
Let’s take a closer look at the B series engine blocks.
In the B18 blocks, Honda increases displacement by using a larger crank and increasing stroke (the B20Z also has a slightly larger bore, which is bad for reasons I won’t go into here). This, of course, lowers the R/S, since the rod length remains (almost) the same.
B16A:
Rod length: 134 mm
Stroke: 77 mm
R/S: 1.74:1
Displacement: 1587.12 cc
B17A:
rod length: 131.87 mm
Stroke: 81.4 mm
R/S: 1.62:1
Displacement: 1677.81 cc
B18A-B:
Rod length: 137mm
Stroke: 89mm
R/S: 1.54:1
Displacement: 1834.47 cc
B18C:
Rod length: 137.9 mm
Stroke: 87.2 mm
R/S: 1.58:1
Displacement: 1797.36 cc
B20A (Older Prelude Si)
Rod length: 141.7-142.75 mm
Stroke: 95 mm
R/S: 1.49-1.50:1
Displacement: 1958.14-2056.03 cc
Now you see two things: Why Honda decreased the displacement from the B18A-B to the B18C, and why the B20A is widely regarded as a not-so-great engine. Honda decreased the displacement in the B18C by decreasing the stroke, improving the R/S. This allows the B18C to rev higher, and (Hey!) increase output.
Making sense? I bet you can see where this is going. But wait, there’s plenty more…
How VTEC works, and why it lives at high RPMs
A quick crash course for anyone unfamiliar with VTEC:
VTEC stands for Variable Valve Timing and Electronic Lift Control. The premise is that at low RPMs and at idle, a less aggressive cam grind is necessary to prevent “loping.” Ever hear a pro drag car staging up at the gates? Sounds like it’s about to stall. It’s because he’s running aggressive camshafts, and since the cam is spinning more slowly at idle, the intake valve is still open after combustion has completed. That’s what causes loping. At higher RPMs, a more aggressive grind is desirable. The idea is that you want to cram as much air and fuel mixture (A/F) into that combustion chamber as possible, so that when it’s ignited you get as grandiose an explosion as possible. So what is good at low RPMs is bad for high RPMs. So what do you do?
If you’re Honda, you invent VTEC. What VTEC does is simply to employ different cam grinds at different RPMs. A less aggressive grind at low RPMs for a smooth idle and low to mid range power, and a more aggressive grind up high to produce that high end pop. At a strategically placed “VTEC crossover point,” the camshaft switches grind from the less aggressive to the more aggressive.
What determines this point? Hours and hours dyno testing and tuning. If it is set too low, the more aggressive grind will kick in early, bogging down the engine (think “loping” at 3500 RPM). Too high, and the engine is missing out on valuable time it could be spending with the VTEC engaged. So all those fools who spent on a VTEC timer running stock camshafts just so they could get their VTEC to kick in earlier- they’re idiots. They just cost themselves a ton of midrange power. The stock crossover point is optimized for stock camshafts.
So when is a VTEC timer necessary? Easy- when you’re no longer running stock camshafts.
If you want big power all motor, you go with one of the big players in the cam game- Toda Spec B and C, or Jun Stage 2 and 3, and you accept no substitutes. All (or at least 95%) of the 225+ all motor whp B18s are running these camshafts.
How does this relate to VTEC crossover point? Well, the VTEC grinds on these cams are so aggressive, that the VTEC point needs to be moved up- way up- usually to 6500-7000 RPM. These cams will also make power to 9500+ RPM (READ: Built motor). Run these in conjunction with high compression pistons (at least 10.5:1), and you’ll have yourself an all motor wonder. And this, friends, is where torque in Hondas comes from.
Why it doesn’t all fit together
So here’s what we’ve learned:
The LS/VTEC suffers from a bad R/S, due to the fact that it utilizes an LS block with a R/S of 1.54:1.
A bad R/S is bad for the engine, especially at high RPMs
Hondas make power through revving, and high power through revving higher, high compression, and aggressive camshafts
Because of its R/S ratio, it is not recommended that you rev an LS/VTEC past 6750 RPM on stock internals- the redline of a stock B18A-B. With a fairly built bottom end, it is still not recommended that you rev an LS/VTEC past 7800 RPM.
As we just discussed, in order to get any considerable power out of an engine, aggressive camshafts are a must. In order to get any benefit from aggressive camshafts, the ability to rev the engine high is a necessity. What good is VTEC if you can only use it for the top 1000 RPM of your powerband?
LS/VTEC is a fad, and I predict that it will be all but a pleasant memory in a few short years. As soon as kids start snapping rods and putting pistons through cylider walls, they’ll realize how important good engine geometry is. Add that to the fact that they’re running stock cams (because it’s all their engine can safely handle) and getting burned by kids running Todas, or Juns, and they’ll wish they had just stuck with their trusty B18C. Like I said, if it was all that great, Honda would have done it in the first place."
Now… some technical LS/VTEC info for those still dead set on doing it… the link is here: http://www.importtuner.com/archives...1_tech01.shtml, and it’s courtesy of Import Tuner’s technical staff…
"Frankenstein Hybrid Honda Power
VTEC Head Meets LS Block
Text & photos by Gary Castillo
In the world of boxing, the bout between Mike Tyson and Evander Holyfield brought two well-trained fighters with opposing styles into the ring.
Tyson, known as “The Knockout Artist” had the power to drop his opponent in less than two rounds, maybe two seconds, but often does not have the stamina to last 12 rounds.
In the world of Honda performance, this situation is paralleled with the DOHC non-VTEC Integra motor, assuming the role of Tyson and the DOHC VTEC engine portraying Holyfield. The non-VTEC 1.8-liter has brute Tyson-like torque, but lacks the ability to venture forth into the higher reaches of the power band, due to it’s unstable valvetrain. The 1.8- and 1.6-liter DOHC VTEC motors have the stamina of Holyfield, climbing long and deep to stratospheric engine speeds, but lacking the torque necessary to fire down the 1320 effectively. If we could apply our hybrid “Tyson-Holyfield” theory to our motor, we would have the best of both worlds–brute torque force and extended high-rev stamina. It exists and it’s called the Frankenstein engine.
Frankenstein Facts
The Integra B18A1 and B18B1 engines displace 1834cc and have an 81mm x 89mm bore and stroke configuration. In the case of the two B-series DOHC VTEC engines, the Integra B18C1 (GSR) moves 1797cc with an 81mm x 87.2mm bore and stroke combo and the Del Sol B16A1 combusts 1595cc with an 81mm x 77.4mm bore and stroke. Basically, this shows that the B18A1 in stock trim has 35cc more displacement than the B18C1 and 239cc more than the B16A1! This is the primary reason why the non-VTEC motor exhibits more of the bottom and mid-range torque than each of the VTEC models. Since none of the Honda engines have the sheer volume of V8 iron, the need to extract as many ccs as possible is necessary to create the low-end power needed to propel a vehicle down the quarter-mile effectively.
The Transformation
We happened to stop by Pann Auto Performance in San Diego and visited Carl Batac, the company’s resident auto surgeon who was about to perform this miracle surgery by putting a B16A1 head on a B18A1 block. Although our pictures show the transplant taking place off the car, this procedure can be done without removing the motor in cars that are motivated by the B18A powerplant since most of the modifications will be done to the head rather than the block. Naturally, this comes in handy if you ever have the urge to return to “blandness” and reinstall a non-VTEC head.
Since this particular transplant is going the all-motor route, Carl decided to replace the 9.2:1 pistons with the 10.0:1 compression GS-R factory slugs. One point that should be taken into consideration is that the VTEC piston will fit in the non-VTEC block and this will create more torque to get you down the 1320. The 10.0:1 GS-R piston is a great street replacement piston however for a race application we would suggest either trying the B16A 10.5:1, B16B 10.6:1 or B18C5 10.8:1 piston to increase the torque for a race motor.
The tools required for the modification are: 1/8-inch tap and driver, 9/16-inch drill bit, 10mm hex wrench, 24mm socket with ratchet and wrenches for AN fittings. The parts you will need to scrounge up include: 1/8-inch NPT T (two female sides and one male side), 1/8-inch brass plug, 1/8-inch male NPT to 4AN male, 3/8 NPT male to 4AN male, no less than 18 inches of four steel-braided hoses with 4AN female sides and the necessary electrical wire for activating VTEC (this depends on the year of the vehicle and your application.)
Conclusion
Horsepower, torque and rpm are the keys to molding our Frankenstein motor. We extracted our torque from the LS, pulled out the rpm from the VTEC and horsepower came from the combination of the two. People say, “You can talk the talk, but can you walk the walk.” so with the Dynojet as our referee the proof is now on paper. Frankenstein lives.
The Honda factory parts that you need include the head gasket, LS timing belt, VTEC head bolts (most preferably the B18C bolts), the correct VTEC intake manifold for your head, and of course the VTEC head of your choice (B16, B17, B18C).
To bolt the head onto the block the dowel pin holes on the opposite aide of the head have to be widened so the dowels can be moved (see arrow). This makes it possible to line up on the LS block. Send the to a machine shop to have the head drilled for the dowel pins or use a 9/16-inch drill bit if downtime is a concern.
With the head off the vehicle, tap the VTEC oil supply hole located near the corner of the number four cylinder intake side (arrow). An 1/8-inch brass plug will fit firm to assure that no oil can squeeze between it. Once the plug is in place, it may be necessary to resurface the head if the plug protrudes out of the head’s deck surface. PIN LOCATOR
Year VTEC VTEC Pressure
1988-91 A-8 B-5
1992-95 A-4 D-6
1996-00 A-8 C-15
To wire up the VTEC pressure switch and solenoid to the ECU, you need to know the year of the ECU and apply this info to the chart above to determine the proper pin location.
Dyno (1)
This dyno graph charts the power of a conventional LS engine (blue) and a VTEC Frankenstein engine. The dramatic jump in performance is easy to spot at 5300 rpm where the VTEC effect kicks in. Both engines were outfitted with an intake, exhaust, header and cam, gears.
It is best for the oil fitting for the VTEC oil pressure line to be tapped off of the 3/8-inch plugon the distributor side of the head (arrow). The 1/8-inch plug will work as well; either one will access the main VTEC oil supply system.
With the head off the vehicle, tap the VTEC oil supply hole located near the corner of the number four cylinder intake side (arrow). An 1/8-inch brass plug will fit firmly to ensure that no oil will leak. Once the plug is in place, it may be necessary to resurface the head if the plug protrudes out of the head’s deck surface.
It is best for the oil fitting for the VTEC oil pressure line to be tapped off of the 3/8-inch plug on the distributor side of the head (arrow). The 1/8-inch plug will work as well; either one will access the main VTEC oil supply system. The 3/8-inch plug will make it easier to remove the head in the future. Use a 4AN male to 3/8 NPT (arrow) to replace the original factory plug. This will be your new VTEC oil supply into the head.
Dyno (2)
Here we see turbocharged variants of the same combination. At 10 psi of boost the VTEC-headed Integra LS engine generated 58 horsepower more than that the same block running a LS head.
With the new 4AN fitting in place run a steel-braided line (arrow) no shorter than 18-inches from the head to the back of the block.
With the original VTEC oil pressure source tapped and plugged, run the new VTEC oil feed off of the factory oil sending unit on the back of the engine block. This is located on the right hand side of the oil filter and has one wire connected to the oil pressure sensor. An 1/8inch brass T with one male side and two female sides will give access to the oil source. A 4AN male to 1/8inch NPT male fitting is used to transfer the oil from the head to the block. Use the steel braided line from the 4AN fitting off the head to connect the oil to the block.
On the top left corner of Gasket B you will notice an extra hole on the VTEC head gasket that was for the original VTEC oil supply from the block. The head gasket you will use is the LS model.
My personal take on LS/VTEC…
Quite frankly, I am both impressed and in awe of this motor set up. A high revving torquey B series motor? Easily capable of all motor 12s?! Sign me the hell up!
I’ve seen a turbo integra built LS/VTEC setup before… 18lbs of boost running mid 11s on Slicks and race gas…
But In all honesty… the idea of reliability comes into play. I’d rather have a relaible B16 that runs 13s, than a 12second LS/VTEC that threw more fits than a 3 year old kid…
And this quote right here does it…
“this guy nailed it on the head. i was going to write up something discouraging using an ls/vtec motor and post it on sho… but this guy’s said more than i ever could. the ls/vtec, in my mind, is a piece of shit. i’ve had one… and now i want a b16 because i’ve ridden in a car now with a b16 and a host of skunk 2 parts. believe me… if you do your b16 right and choose your parts correctly you’re better off… fuck the ls/vtec.”
-5gencivic
5gen had a 12sec. LS/VTEC setup himself, and even HE discourages it. That says ALOT coming from someone who pured their blood, sweat, and tears (not to mention alot of money) into their car… only to discourage others from doing the same.
Makes ya think don’t it?
:dead: :uhoh: :tsk: