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Discussion Starter · #1 ·
How to Build an LSVTEC

I've been asked by a few members about how to build the big B frankenstein engine. I think that a lot of people are looking to do these for the wrong reasons. I can't emphasize enough that it is NOT for a budget build, just because you got a cheap B18A1 or B18B1 block and a deal on a B16 head doesn't mean the best way to make power is to put them together. The real motivation for one of these should be to build something with a little more torque than the average B18C series engine, for about the same price as buying a "better" full OEM longblock. I'm not going to go into detail on how to assemble a bottom end, as that's been covered many times before.

Conversion

The two main challenges you have to deal with when mating a VTEC head to a non-VTEC block are the oiling and the dowel pin locations. The LS and B20 blocks have their dowel pins on the outer head bolt holes on the intake side of the block while the VTEC engines have the holes on the exhaust side. Naturally, the dowel pins won't line up if you just try to slap the head on. The high-pressure oil feed to the head is also different between the non-VTEC and VTEC blocks, meaning there needs to be a different way to feed oil to the head. These days building an LSVTEC or B20VTEC is a lot easier than it used to be, due to the many conversion kits out there for the build.

The oil situation has a couple of different solutions. The common thing with all of them is that you have to block the high-pressure feed into the VTEC head. All of the VTEC conversion kits include a tap and an allen plug for this purpose. The hole that needs to be blocked is on the transmission end of the head on the intake side. You need to tap it out, CLEAN it, and then install the allen plug TIGHTLY. I've seen many of these setups seep oil due to a plug that wasn't tightened correctly. Once you've done that, the head must be resurfaced. This is because the tap and plug can cause the mating surface (bottom) of the head to pull out ever so slightly, making a good seal with the head installed impossible.

Now we have to route oil to the head, since the high-pressure port is blocked. The head will always take the oil in at the same place. There's an allen plug at the back of the head, on the clutch/intake side, facing the same direction as the intake manifold. Remove this plug and install the fitting that comes with the LSVTEC kit, usually these are a -3 or -6 AN fitting. For the oil feed, there are two main options. The first is using a T-fitting (BSPT) on the back of the block where the factory oil pressure switch is, just like you would mount a turbo feed. The other popular option is to use an oil sandwich adapter like the Golden Eagle unit. Personally I prefer to use the sandwich adapter with a -6 line to the head. I feel that this setup provides adequate oil flow without sacrificing oil pressure to the head. I've personally seen a couple of B20VTEC setups that would not engage the high-cam consistently and smoothly simply due to oil pressure, switching to the sandwich worked the issues out.

With the oil situation taken care of, we can move on to the pins. The "old-school" way to make the pins work was to have the holes in the head bored out to accept the LS/B20 dowel pins in the other two holes. My roommate has a setup like this and it works perfect. Nowadays, you can get specific dowel pins for these setups. They are larger on one side so that they work with the factory holes in both the head and the block. I would recommend the LSVTEC special dowel pins to everyone.

Head Studs, Timing Belt, and Headgasket

The next thing you need to decide on is the headgasket. I've used both the VTEC/B16/B18C headgasket and the LS one (or B20 for the bigger bore engines). If you just want to slap it on, your dowel pin situation will determine which you use. If you have a unibit you can drill out the smaller holes and make whatever you want to work work. There is some debate about which gasket is actually better to use, based on the cooling passages. I've used both before with no issues, but I prefer to use the LS/B20 or a custom (Golden Eagle or Cometic) gasket for ease of installation.

The timing belt needs to come from a B18C (C, C1, C5 are all fine). This is because of the added cam gear height from the taller head combined with the taller 1.8 block, and use of the VTEC 22T water pump, which has a larger gear. If you were to use an LS 19T pump the LS belt would fit (more on the water pump below).

For head bolts/studs, you want to use GS-R (B18C1) studs. DO NOT re-use old head bolts. Unless someone gives you some new GS-R bolts, you'd be best to go ahead and buy the ARP studs for the setup. If you're making any decent power or you plan to take the head off again you're just doing yourself a favour.

The Block

Now on to the bottom end. There are a few upgrades you'll need to make at the minimum to make the LS/B20 bottom end work correctly with the VTEC head. Many people choose to go all out and bore over, run forged pistons and rods, and even add a crank girdle. I'll go over the main things that I see as minimum requirements to build a healthy, reliable bottom end. The LS bottom end has many disadvantages when compared to the VTEC blocks, especially the B18C blocks which are very robust. Remember that any reference to the LS also includes the B20, as they are identical except for the bore.

The weakest point of these bottom ends is the rod bolts. They use the very same 8mm bolts used in the D series engines, and are not designed to hold up to high-RPM use. Some people may argue that they don't need to be replaced, because they aren't going to rev the engine any higher than stock. If you put a VTEC head on, even a first-gen B16A head, you're going to need to rev beyond the stock LS's capabilities. The rod bolts are relatively cheap, and since you have to remove them you need to replace them with a new or aftermarket set. You need to replace them in order to modify or change the pistons, as detailed below. When you install the ARP bolts they need to be pressed in, and have the rods re-sized if the big ends are warped from the install.

The reason for removing the rods and rod bolts is to change or modify the pistons. The stock non-VTEC pistons do not have the correct valve reliefs for VTEC heads, this will become especially dangerous when you run a more aggressive set of cams. You can either install a set of VTEC pistons, aftermarket pistons, or get your non-VTEC pistons fly cut to accommodate the head. The most cost effective thing to do here is use a set of VTEC pistons, usually P30/PR3 B16A pistons. Someone is going to ask about PCT (CTR B16B) pistons. If you have to ask, don't use them. Many of the online compression calculators are incorrect, and will calculate the compression wrong since they don't take into account how the PCTs stick up 0.007" out of the block. Even with a PR3 head, this puts the compression prohibitively high for street use on pump fuel.

If you are using a newer block that doesn't have a PCV box on the back, you MUST install the fittings on the back and run a catch can. If you don't do this, you'll get excessive crank case pressure which will make its way into the head and can only exit by squeezing out the small vent tube or blowing seals out. I've seen this mistake made a couple of times and it will destroy your seals.

Lubrication and Cooling

The LS water pump has to go. You want to use a GS-R or any VTEC water pump aside from some early B17A1 and B16A pumps. The one you want says "22T" on the drive gear, and coincidentally it has 22 teeth. The other pump says 19T on it, and has 19 teeth. Now, if you actually thought about that and how the belt/pump works, you'd notice that the LS/non-VTEC pump actually spins faster at a given RPM than the 22T pump. The reason this is bad for your new VTEC engine is because it spins a lot faster, and the increased speed causes a condition called cavitation. This is when bubbles are introduced into the coolant inside the blades of the pump and actually decreases coolant flow because the pump is creating bubbles, not pushing water. If you look at the two pumps you can see that the blade spacing is different on them for the same purpose of fighting cavitation at high RPM.

For the oil pump, you'll want to go with a new ITR/VTEC pump or a rebuilt and modified one as I outlined in my article about the ITR oil pump myth. You need the increased flow for protection, and you should replace it anyway since you're taking the bottom end apart. Rebuild cost is around 30 bucks for the two rotors and the spring. Remember that your LS bottom end is already at a deficit without the oil squirters of the VTEC blocks, you need every little bit you can get.
 

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Discussion Starter · #4 ·
Matt is going to write up a little about the engine management for a setup like this, I just wanted to cover the actual engine part, but the management is just as important.

It would be cool too if those of you who actually have LS and B20VTECs already built in your CRXs could post up if there's anything I missed.
 

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Discussion Starter · #5 ·
I also forgot to mention the importance of balancing the bottom end before you put it together. My roommate just brought this up. As with ANY build, you should always balance the bottom end before assembly, this is definitely not an exception since you're taking it apart anyway.
 

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Discussion Starter · #8 ·
crxgator said:
i think the best and easiest way to do ls/vtec is to get a b16b/b18c block and use the ls crank, that way you dont have to worry about extra oil lines, dowl pins and you have a girdle stock...
That's not really an LSVTEC though, it's a stroked B18C. You also have to bend or remove the oil squirters to clear the LS crank's counterweights.
 

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which doesnt matter because the ls doesnt have the squirters to begin with.

all in all an ls/vtec conversion would be about the same price as a stroked b18c. however a stroked b18c or if you get your hands on a b16b block would be even more sleeperish... :lol:
 

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Discussion Starter · #12 ·
crxgator said:
i understand that. it's the same principles for the most part, except the ease of putting one together goes with the vtec blocks...
I agree with that, and personally I'd rather start with a VTEC block as well, unless I had a B20.
 

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