12R Tuning

[Laxpower]

Does anyone know if any companies did tuning parts, or ‘how to tune’ info for 12R engines in the seventies? If they did, has anyone got any parts or info? I know there were some custom 12R powered Hilux pickups around at the time, but how much was done to the engines, I don’t know.

I build tuned engines for rich folks who want to race mega buck old cars, and want to see if I can apply my know-how to my RH11 Hiace bus engine.

What I need most is a fast road or race cam, in any condition as long as some of the lobes are intact, or even a data chart listing lift, duration, overlap, disposition, ramp velocity, etc., so I can have one made.

I’m sure some improvements must have been made at some time, over the original ¼” lift cam.

I know the project will be limited by the 12R three bearing crank design, which tends to get whippy at high RPM – I’ve had similar cranks break in old Ford engines – but I’m not after an all-out racer (yet). Just something that pulls better up hills, and cruises at speed on the motorway.

I’ve searched the net, with no luck. If anyone can help with anything at all, I’ll be your friend for life.

Bad Bob

[Steve gee]

Does anyone know if any companies did tuning parts, or ‘how to tune’ info for 12R engines in the seventies? If they did, has anyone got any parts or info? I know there were some custom 12R powered Hilux pickups around at the time, but how much was done to the engines, I don’t know.

I build tuned engines for rich folks who want to race mega buck old cars, and want to see if I can apply my know-how to my RH11 Hiace bus engine.

What I need most is a fast road or race cam, in any condition as long as some of the lobes are intact, or even a data chart listing lift, duration, overlap, disposition, ramp velocity, etc., so I can have one made.

I’m sure some improvements must have been made at some time, over the original ¼” lift cam.

I know the project will be limited by the 12R three bearing crank design, which tends to get whippy at high RPM – I’ve had similar cranks break in old Ford engines – but I’m not after an all-out racer (yet). Just something that pulls better up hills, and cruises at speed on the motorway.

I’ve searched the net, with no luck. If anyone can help with anything at all, I’ll be your friend for life.

Bad Bob

Hi Bob.

I ran an RT40 with 2R then a 12R and used lots of parts from the 4R 1600S engine.

I used the 12R as it had full flow oil flitering whereas the early 4R's had partial metered oil filtering.

Wade, or Crowe 24/80 cams worked fine most heads had dual valve srpings, but the best thing you could do is find a 9R head Yamaha from the 1600GT and fit it. QED using blank dummy oil shaft and front timing cover. I ran a 48mm weber on a 12r with high dome 4R pistons and it won rallies.

[the71hiace]

haha, i actually own one of these as well, a 71 model panel van, mine's getting a holden red motor though. what colour is yours?

[rt26tiara]

haha, i actually own one of these as well, a 71 model panel van, mine's getting a holden red motor though. what colour is yours?

[rt26tiara]

haha, i actually own one of these as well, a 71 model panel van, mine's getting a holden red motor though. what colour is yours?

Hi,

I also have played around with 2R's,4R's and 12R's. I had a 12R engine that I put a 4R head on. The head had no rocker assembly so I put the 12R rocker assembly on it. Trouble is the 12R rocker assembly is not as tall as the 2R/4R rocker assembly (inlet and exhaust valves have shorter stems and inlet valves are larger on 4R's). I used Isusu valves for the inlets and shortened the valve stems to suit. I also installed a Crow cam (could dig up the specs if you are interested). Next problem I faced was because of the shorter 12R rocker assembly and valve stem length, and the extra travel required as a result of the performance cam, the valve collets were hitting the top of the valve guides when the valves were fully open. I had to get a couple of millimetres shaved of the tops of the valve guides to allow for the extra travel. Bottom line is 12R's can not accomodate as much valve travel as the earlier 2R's and 4R,s because of the shorter valves and valve assembly.

John