LS/VTEC Swap Article

[Kaiser]

Originally from c-speedracing by Del Emerson
Using a 92 GSR ECU P61, B18A 91 GS bottom end and a B16 VTEC head. There are many ways and combinations available and it is entirely up to you on which head and block that you decide to use.

The accuracy of performing the modifications in the following steps is vital to the outcome of the swap. If you are not entirely certain of the process or have the experience in using the required tools, please contact a machine shop to have to work done.
LS/VTEC parts list:
In this article we use a 1992 B17 VTEC head. However, you can use any VTEC head (B18C1, B18C5, B16, B17). You will also need about 3 feet of braided stainless steel line.

You will also need the following:

. LS headgasket
. B18C water pump
. B18C timing belt
. B18C head bolts

You may choose to use a non-VTEC water pump, however you must then use a B18A non-VTEC timing belt. You can also use to use a VTEC oil pump since it has higher flow as compared to the non-VTEC units. We chose to use P73 ITR pistons. We chose LS rods to use with the ITR pistons. With a stock deck height and stock headgasket it should put compression at around 10.9cr. 1991 LS B18a block. This block used because it is in very good condition and has an oil/water seperator in the back of the block just like the B17a.

Since the motor will seeing 7500-8000rpms its a good idea to upgrade the stock rod bolts to ARP units. If you are using stock LS rods, you will need 1.2-1.6 rod bolts x 8mm. Part # 208-6001. DO NOT use the VTEC 1.8 x 9mm units.

-4an braided stainless steel line fittings. You will need four of these. Part # FCM-1011

-4AN to 3/8NPT plug needed to plug the intake side of the head for the oil supply. This is an Aeroquip part # FCM-2519
Oil feed setup. There are several ways one can do this. This method is to run the SS lines to a Tee on the firewall rather than Tee'ing from the back of the block.

Oil supply hole, it is necessary to have it plugged. You may opt to have machine shop perform the task or if you are familiar with using a tap, you can do it yourself. Tap the hole with a 1/8NPT tap and plug the hole using a 1/8NPT plug. Be sure to use lock tite prior to screwing it in. If you damage the head, it will need to be resurfaced. Take your time.
Remove the plug in the back of the head and replace it with a 3/8NPT to -4AN fitting. You will run your SS oil line from this location. Be sure to use teflon tape on the threads.

There are two places you can relocate the dowel pins. This involves modifying the dowel pin holes on the LS headgasket to match. Keep in mind the holes on the gasket aren't the same size. We recommend using a machine shop to do the work however, if you have experience with a drill press then you can perform the task yourself. Remove the dowel pins from their stock location and reposition them to the space provided. In order for them to fit in their new location, you must mill out that hole to the size of the dowel pin. Repeat the process on the timing belt side.

The second method to relocate the dowel pins is simpler. On the intake side of the head there are two locations on the left and right that are good for putting the dowel pins. All that is required using this method is that you resize the holes to fit the dowel pins. The LS headgasket already has the correctly sized holes, therefore there is no need to modify the headgasket. In some applications, the two brass rings labeled 'REMOVE' on a headgasket need to be removed, otherwise the head will sit on top of those and will not seal. Be absolutely sure you remove the two on the intake side only.


There is no knock sensor in the back of a b18a block. The knock sensor came on the 92+ VTEC engines only. If your block doesn't have a knock sensor, you will need to located a hole for one. We chose the location of the knock sensor on the b17 block. On a B18a block we chose to remove one of the mounting bolts for the alternator bracket and use this as the new location for the Knock sensor. Using a 10.9 mm drill bit, opened up the hole on the bracket and the block. Then carefully tap the hole with a 12 mm x 1.25 thread pitch tap. Be sure to clean up the shavings and then screw the knock sensor. This will keep your ECU from throwing any codes.

Once the modifications to the head are complete, you can go ahead and assemble the head and block. Be sure you have the headgasket installed in the correct direction and right side up. Torque all the head bolts. Your last step is to run the new oil lines to feed the VTEC head.

First, you need a section of braided stainless line. In order to cut the SS line without it fraying or splintering, wrap the area where you want to cut with tape tightly. Place the SS line in a vise or something similar to ease the cutting process. Use a hacksaw or band saw to cut it.

Now place the red housing of the AN fitting snugly over the SS line. To aid the next step, be sure to lubricate the inside of the SS line. Place the silver insert of the AN fitting inside the red housing. It may be easier to place the red housing in a vise. Cram SS line into the red housing and screw them together with a wrench. Repeat the process until you have two lines with the fittings securely attached on each end.

Run one of your SS lines from the block to the one hole in your Tee mounted on the firewall. Run the other SS line from your second hole to the -4an to 3/8NPT fitting on the head pictured here. The third hole on the Tee will be plugged with you stock oil sending unit. Be sure to use teflon tape to seal the threads.

Securely fasten the entire unit to the firewall. Make sure you do not tighten the SS fittings on the head until your fuel rail is installed. *note - if you are using an additional oil sending unit for gauges, then you will need a 4-way Tee.

You will need to extend the stock oil sending wire to reach its new mounting location on the firewall.

edited by Kaiser
for the original article visit c-speedracing