B20A5 motor with a B16 vtec head - Honda Prelude Forum

3gturbo · 12-31-2003, 07:23 PM

It has been a while since I have updated you all on the progress of the Slug. I have completed engine wiring harness to control the Vtec motor. I took an old B20 harness that I had laying around and the cut harness that came with the B16 and just started changing pins and soldering wires. The new hybrid harness looks like a stock harness. I used all factory connectors and covered the finished product with wire loom and black tape (high temp). I removed the ignitor and ignition coil from the right strut tower, because the b16 head has it all built into the distributor. I only had to run two new wires to the head through the harness, for the Vtec spool and Vtec oil pressure. I also had to add a wire for the knock sensor. The new PR-3 ECU does not have an input for the power steering pressure switch, but has an input for the brake light switch. After removing the left fender I spliced and connected the brake switch output that normally goes to the cruise control actuator (which has been removed) into the power steering wire that goes to the ECU effectivly making a brake input to the new ECU without running any messy wires under the dash. The only new thing electrically that I will have to add to the b16 head is the fan control switch #2, that used to mount to the t-stat housing. I have to tap and drill a hole in the head to install the switch. Hopefully next week I will be able to start adding material to the head, this is the next big step. We are going to make the B20 head gasket match the B16 head. The only thing that I am debating about right now is to use turbo again or to make it an all motor engine with NOS. I currently have NOS in the car, so that would be very easy. Is there anybody else out there that is as crazy and/or stupid enough to do this please give me a shout and we can chat vtec. Until I get some more work done- Peace Out!!

reyke · 01-01-2004, 08:21 AM

I've heard of this swap and have only heard of it being done on a semi-finished basis, the most I've ever gone with doing work on my previous ludes, was I went from a 81 mm bore to oversized b21 pistons, or in other words a 83.5 mm bore and milled the head till the valves were .25 of a mm from the mill surface, I also have to take a dremel and open up the oil passages becuase I milled them flush, if you ever look at the mating surface of the b20 you'll know what I mean. Then I polished the rods, and had them balanced, unfortunately due to shotty machine shop work that motor only lasted for 3000 miles, it was a fun 3000 miles but it was short-lived. Right now I am trying to make an adapter plate so I can mount GSX-R Electronic throttle bodies to the head, they are the proper diameter, in fact they are a hair larger, and then I'm going to need a stand-alone but this is all in the works nothing set in stone, but I much prefer NA withj nitrous than turbo, I would muc rather get a car that already had turbo on it from the factory. Just my opinion and nice to see a 3rd gen owner taking thier car to the next level. By the way I know Tom Coleman said he had to modify the bolt holes in the vtec head becuase according to him the bolt holes on the b20 are spaced to close together front to back, they are the same length left to right. Well keep us posted, I know I would like to see some pictures.

3gturbo · 01-01-2004, 11:12 AM

Good luck with mounting the electronic throttle body to that motor. Yes it is true that I have to make the bolt holes in the head wider. I have a guy lined up who has an end mill who will do it for fifty bucks, that is really the least of my worries. I have taken some pictures of the wiring harness on the motor on the engine stand. I will attempt to attach them to this post. If I can't you can email me and I can send them to you. Later

RaM · 02-03-2004, 02:28 AM

Any updates on the conversion? How about the hybrid head gasket?