Articles » Engine Swap Guide

Ok, So far we've covered the D16Z6, D16Y8, D15B7, B16A1, B16A2, B16A3, B16B, B17A, B18B1, B18C1, B18C5, H22A1 H23A1, H22A4 and the F20B. Talk about choices!!! But we're only half way through. Now we go to the second part of the swapping experience, which is cylinder head swapping. Sometimes called a Frankenstein, engine hybrid, mini-me or LS/VTEC swaps. Head swapping usually includes getting a Non-Vtec block (B18B, D15B) and taking the entire cylinder head assembly from a Vtec enabled block (B18C1, D16Z6) and swapping it onto the Non-Vtec block. Effectively giving the non-Vtec block Vtec capabilities just like his older brothers. Hence the name LS/VTEC. LS for Non-Vtec and Vtec for...Vtec . It isn't easy though. The Vtec assemblies use oil to activate the system so oil lines will need to be tapped, the block and head need small preparations to flawlessly mate the two and the ECU from the Vtec enabled block will also be needed. So the grocery list includes the ENTIRE cylinder head set and everything attached to it, The intake manifold, throttle body, throttle cable, distributor, Vtec solenoid, EVERYTHING. You will also need the ECU, Vtec oil pump and various other lines and fittings and someone who's done this before. Here’s a great site that gets to the nitty gritty of the procedure: http://www.diyracing.com/ls_vtechowto.html

Now this opens up a whole new world of possibilities. But first you need to know the rules before continuing. These are:

1. A SOHC block cannot accept or be modified to accept a DOHC head. It just does not work. Block surface and the bottom of the head are totally different.

2. Only engines with the same letter association have compatible part. IE B-series with B-series and D-series with D-Series.

3. Don't do go cheap with this. This needs to be done right or you're left with an engine that leaks oil, has Vtec engagement problems and possibly valves that smash into pistons.

Head Swapping Cons:

There are of course downsides to mating two engine parts that were not designed to be together and expecting to work together. One of the main problems is that Vtec enabled blocks were designed to rev allot higher than their non-Vtec counterparts. Of the things Honda designed into the Vtec blocks to help them survive high rpm use are oil squirters. Oil squirters serve dual functions both as piston coolers and piston lubricators. Both of which are very important when revving to 9000 rpm. The lack of which could result in damage from prolonged high-rpm usage. Another aspect is that non-Vtec blocks usually have worse R/S ratios making the situation that much worse. The stock oil pump will also need to be replaced as it might not have enough pressure to satisfy both the block lubricating needs and the oil-activated Vtec assemblies. Valve clearance is another issue that needs to be addressed before you not only mate the head and block but also play with cam timing. The valve relief’s in the stock pistons are usually deep enough to accommodate the new longer travel of the Vtec valves but if they aren’t, they need to professionally widened or aftermarket pistons need to be used. And when using camshaft gears to tune cam shaft timing, each setting both 2 and 4 degrees advance and retard need to be tested for valve clearance as well. Failure to do so may cause the valve to crash into the piston when it arrives at TDC (Top Dead Center) which could bend it or chip it which may cause even more damage. Either way the head needs to pulled and repaired.

Head Swapping Pros:

One of the points of swapping in a Vtec head is they usually flow allot better than their non Vtec counter parts. And this can even be improved further with a port and polish. So with that in mind, the best flowing DOHC heads can be rated in this order:

1. B16B
2. B18C5
3. B16A
4. B18C1

The B16B head is by far the best head but it's rather expensive and rare. It's basically a B16A head with a factory P&P and lighter valvetrain assemblies among other things. This goes as well for the Integra Type R head. It's basically a GSR head with a factory port and polish, slighter better and lighter cams, valves, springs, etc. The best compromise for price and availability is the B16 head and the last one the list would be the GSR head. Of course it needs to be said that simply swapping the head onto your engine won't give you all the HP from the engine the head came from. Like swapping an GSR head onto an LS block won’t automatically give you 170hp. There were more changes to the engines than just the head like displacement, compression and air flow tracts. But it's still better than your stock head.

In reality, the majority of your engines power capabilities come from head design. This goes especially for naturally aspirated engines. With each one of these head swaps, you could completely redo all the components in the head to make the HP jump even greater. The exact changes of course depend on if you want to stay naturally aspirated or decide to take the plunge into forced induction. The details of both will be covered on another article. Also between the generations, small changes were made in an effort to produce more power and better mileage. Example, the SOHC head changed from the 5th generation to the 6th gen. In particular the quench area, the area where the compressed air and fuel collect when the piston reaches TDC, was changed to a more squared area. Rather than the circular area on the 5th gens, this new square quench area forces more of the A/F mixture closer to the spark plug which results in a cleaner and more powerful burn. These subtleties can greatly affect the overall power production of your new engine design.

So now, what are your greatest bang for the buck options? Let’s break them down by what engine you have:

D15's: Say you have a Dx or Cx engine, then you could go ahead and swap out the head for a D16Z6 head. You could probably get the whole swap for $300. The 6th geners with Cx’s or Dx’s can swap for a D16Y8 and build that for greater NA or FI power.

B16: Swapping the head on this engine isn’t really necessary since the head is already a top-notch design. What could be done is a head redesign (P&P, Cams, valves) or you could swap it for a B18C5 head, which is better, but not by much. This swap would be more for the WOW affect. Although a turbocharger or supercharger can both easily be installed on this engine and its air flow characteristics let it achieve more than 200 wheel hp.

B18B's: The GSR or B16 head swap would be ideal in these situations. Can also be turbocharged by using the kit designed for the head you swap in. But as mentioned before, the R/S ratio would still be a limiting factor in maximum power output.

B20B, B20Z: Now HERE'S where the real deal is. Since the giraffe intake on the B20B doesn't clear the hood, the head has to be swapped anyways, so you could use any of the choices above as well for the B20Z. My personal favorite, you swap in a B20 with lots of usable torque, then you swap in a modded B16 head and make a few ECU changes, like rev limiter and now you have lots of torque with Vtec high end and an 8000 redline. Or the low compression rate allows for decent turbocharging and you can achieve great heights with the B16 head flow.

H23A1: Generally the swap here is an H23 block with an H22 head swap. It makes for great Vtec high end and the larger displacement block makes for the biggest torque of all the engines listed here.

I could go so many ways in explaining head modification, NA, FI, procedures, Etc. But I tried to stay on subject and this is the civic owner engine swapper’s guide. Please feel free to ask questions or make corrections.