my guess is the adjustors were taken out whenever these heads were installed...whoever put the heads on must have known they are 100% useless and serve no purpose haha.

I looked in the Hollander interchange application information, but didn't find a reference to any jet valve heads on a 1990 Montero.

Frank

Is it JDM Frank ...?? You know the motors they cut out of cars in japan and ship us with 50.000 miles ..There laws make them .. But was thinking that they never used jet-valves on the home islands of Japan on there cars or EGR valves.. ...I'm sure I'm wrong..

David

Hazardous Toys inc

OldColt I'm sure is right ..Sigma were strange.. Frank you find any jet-valve V6 heads..?

its a mca jet valve search the net you can get an eleminator kit for it i have been running them for years in my van

You can do that ... But whats going on here "I" would not..Some are saying the jet-valve is one of the reasons Mitsu heads crack .. I'm not to say ether way ..But if I can stay away from a jet-valve head in my builds I do .. Have used them and do use the jet-valve plugs .. But like to stay away from them if I can...

Okay so using this head is obviously out the window. In terms of getting a pair of heads rather than just one, that's where my dilemma begins. I've been working on this Montero for the past year and had the heads cleaned and rebuilt several months ago. About 2 weeks ago I got the bugger running and drove it around for about 2 hours total. Then the cam seized. So trying to find another pair, when I know one of the heads is in optimal shape, is the kicker. If I can get just one head, rebuild it, and have the piece of mind that it'll run just as good as having a pair from the same vehicle, then I'll probably just do that.

We understand .. I've been there too.. Can be hard to get a car to run God knows I know that ... I don't think some knew the full story here on the forum...Good move to keep looking on a head .. Good luck...

I haven't found any reference to a jet valve in any of the 3.0L engines, but obviously from this example, they do exist.

The reason I'm cautious about using heads mixed from separate engines without checking head thickness and combustion chamber volume is the possibility of ending up with a different compression ratio on each side of the engine, which may produce a better burn and changed gas composition on one side as compared to the other.

The ECU trims the fuel mixture by (among other inputs) reading from the single o2 sensor, which is behind the Y-pipe collector where the gases from both sides merge. The sensor will read an average of the combined gas and will fuel both sides of the engine equally. There is a possibility that the resulting injector pulse width could be too short for one side of the engine or the other, resulting in a rich mixture on one side of the engine and a lean burn and pre-ignition or even detonation on the other side.

OTOH, that worry is really a maybe and might not be a concern in practice, particularly with the conservative ignition curve built into the Gen1 Montero ECU.

It's worth a try to save some money..... just be sure the correct cam is installed.

Frank

Yeah, I am trying to save money-wise, so sticking with one head replacement seems most logical in that sense. But Frank, your insight as to "potential" problems does give me the sense to at least consider picking up a pair.