Im trying to figure out what it is that makes this 3 liter V6 so weak. Is it the intake? the cams? ECU? combustion chambers? Im hoping guys like EB will chime in with some areas that need work on this engine.

From my limited exp Im thinking the Exh valves are a bit too small or maybe the intake runners are too restrictive? I have done quiet a bit of work to mine and Im fairly happy with the results but Im looking for more.

It baffles me why no one has blank cam stocks or why more perf parts arent available. There is tons of these things running around but not many perf shops make anything for them? I have an extra 3.0 on the stand I was planning on rebuilding with one of EB's master kits (cost is very reasonable) but id like to know why the damn things make no power down low? Maybe Im just expecting too much from 3 liters but I dont think so.

There should be enough motor oriented guys here to come up with some good discussion.

I would also love to hear from EB and others over here about this, but just in case you haven't seen it, here is a post on Yotatech about this subject that is very interesting http://www.yotatech.com/showthread.php?t=37265
Warning the discussion has been going on for a long time now on 2 different threads with a total of about 11 pages of reading/skimming to do. <img src="/forums/images/graemlins/smile.gif" alt="" />

The 3.0 is slow for many reasons, one is that misengineered and very restrictive crossover, the other is the air intake. The biggest problem w/the 3.0 is that it can't breathe, it's congested! Let the engine breathe by getting rid of that restrictive x-over, put some headers on and modify your air intake and she runs pretty well! <img src="/forums/images/graemlins/kewl.gif" alt="" />

Read my sig I think I have done my part for bolt on stuff and even head porting and cams. Im looking for fundamental flaws,Exhaust is always a flaw on factory mild engines. The engine has more stroke than bore so in theory it should make for a torquey motor not a high revver like mine has become.

I'm with EB on this one. I believe it has to deal with the exhaust valves being so small and crap. There could be many reasons also why it is so hard to get good power out of. We need someone to start looking into the 3.0 and experimenting with it and stuff...EB maybe you ??

well, i'll tell you.

got the downey headers and custom made x-over.

i dont fell any diff.

granted i had mine installed, same time i had the 96/97 tranny installed so i can get a marlin dual x-case going...

i knew i shoulda dynoed before and after... GRRRRRRRRR

[/quote]
The 3.0 is slow for many reasons, one is that misengineered and very restrictive crossover, the other is the air intake. The biggest problem w/the 3.0 is that it can't breathe, it's congested! Let the engine breathe by getting rid of that restrictive x-over, put some headers on and modify your air intake and she runs pretty well! <img src="/forums/images/graemlins/kewl.gif" alt="" /> [/quote]

I do not agree here. The x-over pipe is a very common design on front drive V-6 engines (which was what this engine was designed for). It is still widely used wtih engines making a lot more power than the 3.0.

Personally I do not think that this engine was ever intended to go into this truck but Toyota needed more power to compete and this is what they had.

This was also Toyota's first V6. Typical 1 generation Japaneese stuff has its share of issues while they learn. In my opinion they did pretty well with only a minor head gasket problem and an engine that will easily run 200k plus miles. Shoot, GM and Ford can't do that today.

We like to complain about this engine but look at your other options for '89 - '95:
Ford Ranger: 160hp 4.0L
Chevy S-10: 175hp 4.3L
Nissan: 150hp 3.0L
Chevy 350: 205hp
Dodge 318: 180hp
and on and on and on.

We have come a long ways in the last 15 years as far as making power. Remember the '89 Mustang at 225hp, that thing was FAST at about 6.0 to 60. Today the Honda Accord makes more power and is faster.

How have we done this? Variable spark timing as a result of DIS is huge. This has allowed us to learn a lot about fuel maping, running richer and leaner while compensating spark to eliminate predetination. We have learned a lot about air flow and have improved heads significantly.

I think that EB may be on to something with the exhaust valve sizing. 2-valve engines are usually torque monsters but for some reason this engine is weak between 1,500 and 3,000 rpm. Then it dies out above 4,800.

If the exhaust was the limiting factor the header guys would be noticing huge power gains. They notice very little.
If the intake was the limiting factor the Camry V6 should be making a lot more power. It didn't. Or at least the guys who are porting the intakes should see it. They are not seeing huge gains.
Cams help but not like they should.
I think that I have seen every kind of intake box configuration imaginable with nobody noticing huge improvements either.
The cat? Plenty of you do not have cats. I took mine off and noticed nothing.
Exhaust? Nothing big here either.

What is left? The block, pistons, stoke, bore? Stroke and bore will have an effect on torqe or hp but they are not what will hold a 3.0 at less than 200 hp.
The fuel system? With the mileage that my truck gets I do not think that it is starving for fuel.
The heads are the answer. I have heard that someone is putting later model Camry 4 valve head on a truck motor. This may be it. Maybe EB could ship me a set of 3.0 heads with bigger valves? I am willing to pay. If there is room in there to get them in and still have a head that will be reliable.

Did you have a full exhaust put on as well? When I first installed my headers I had them hooked up to my factory exhaust and the results where less than exciting. A week or so after installation I decided to go down and buy a new cat and a flowmaster along with enough 2.5"pipe to make up a new exhaust. Once I finished the exhaust the performance improvment was very clear.

I didnt use the bolts that came with the downey headers I opted to use studs. I actually used the studs that came from my old exhaust parts. there are 9 longer studs that are used to hold the factory xover together and I bought 3 more from the dealer and use those. I also cut up a pair of factor manifold gaskets (the sheet metal ones) and use those instead of header gaskets and thay seem to work ok.

How much improvement is very clear?

well It was pulling slowly to 4000 then falling on its face with the factory 2" pipe/cat/muffler.

After updating I saw marginal improvments between idle and 2800 RPM but after that........ @2800-2900 RPM the exhaust clearly got louder and the truck pulled strong peaking at around 5000 but would pull to the redline with no problems.

In my case the exhaust was a real limiting factor with everything else I had done. I dont think you will see the kinda gains that I saw but I can say with out a doubt that the headers where a minimal gain with out the exhaust. It is actually more fun to drive when you can pull strong to 5k then shift and be right in the meat of the power again. With 32" tires and stock 4.10's I was able to run first second and third pretty hard creeping into the 60-70MPH range when I push the clutch in to hit 4th. It should be alot better when I get 4.88's installed

It seems to me that all the little things work hand in hand to add up.