Well, all this in mind... i lean more toward the 3.4L swap. DIS ignition, OBDII computer system, Capable of a supercharger. Easy to work on.

In my opinion the 3.0 has enough faults on the outside to make me veer from it. it does NOT have DIS igition...still running a distributor in 1995? also, the air flow meter is that of a lawn mower. to make HP you need Air & fuel. I also think the computer programming is weak. I used to write software for GM performance cars like my 89 Corvette. Stock ran 15's.... swaped all bolt on stuff.. ran sub 13.5's. I think toyota could of done better, but they were thinking "reliability" with it too. so they stuck to the basics. i think before the OBDII computer systems emissions killed performance. so manufacturers had to go with crap performance and parts like wimpy AFM's etc. either way.. it's outdated. I could do a 3.4 swap in a weekend. that's what i'm going to do. I'll start running cheap oil & filters on the 3.0... start saving money there.. but still change it. i have 135K right now... runs like a dream. by 150K i want my 3.4L with 60K miles.

[quote]Dont you think 1mm is a bit small for a valve increase on these motors? Dont you use the stock seat at just 1mm oversized? When I got looking into the head I noticed that the exh valve seat was quiet a bit smaller than the bowl but that was not the case on the intake side. I was thinking that increasing the seat size to mach the bowl would be better but that would take 2-3mm over sized valve right?
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>>>*You are correct in that larger will add even more airflow. Increases in flow at the exhaust size work best at optimum, so one has to take into account all of the other variables such as swept area(volume) and expected normal RPM powerband.

It's always a guess for the most part.

One thing is sure, volume area on the exhaust side increases RPM potential. So if the valve and port gets too large, the engine will go lazy at slower speeds.

Taking 1mm out of the inside dimension of a valve seat adds a LOT of area. If the valve seat is already too restrictive, then the gains are huge. If the seat and port are not highly restrictive, the gains now become small.

The idea is to hit a balance that maintains throttle response and gets one closer to that perfect combination needed for nice throttle response and power.

Now we know that a 1mm oversize intake adds more area than a 1mm oversize exhaust. The balance stays pretty close.

When we tested valves on the little 22R engine way back, we found a full 1mm (.039") exhaust valve was too big. But only when we wanted to maintain low end torque and response.
So we hit on .024" as perfect.

Now I get laughed at from time to time by folks that tell me that .024" bigger won't do anything....Think of it like this: That is surface area, .024" wide times 1.471"(roughly) times 3.1416. Quick, somebody do the math, what's that in square inches compared to the entire valve head size stock in square inches, don't forget to subtract the 8mm stem surface area.

*Ran out of fingers...*LOL** (There will be a test at the end)


You could be right on the need for an even larger exhaust, it's just my feelings right now that this isn't correct for this engine design. I think one could lose low end power very easily by going too large, especially adding headers and a free flowing exhaust.

Note the "I think" part, still experimenting.

Now if there is a Turbo involved, or high RPM use is desired, that all went out the window, and we start over.

A quick example one can use is the common 350 Chev. We use 1.94-1.50" valves for stock, and 2.02"-1.60" for performance. 2.05" valves are available, nothing happens. 1.65" exhaust are available, nothing happens. Now when the rules say 2bbl carb and stock exhaust, we use 1.85" valves and 1.50" exhaust for a best choice, and I have even cut exhaust valves down to 1.460" and installed a seat to keep the velocity up on highly restricted engines..Everyone told me I was nuts, but we got the track record AND the Championship.....The key is balance, hit it and the engine is sweet....*EB

This is what exactly happened to me when I put the high flow Downey muffler on, after the headers and the highflow cat, and the exhaust valves are stock. I have plenty of power at 3200 and above, but the low end torque is gone. The loss of low end torque I experienced w/the highflow muffler may not be felt much in a stock weight truck, however with mine pushing 5000-5300 lbs it made a difference. I have noticed the hills I could climb in 5th at 2800 rpm's(with my stock muffler with rust holes), I now have to shift into 4th. I haven't gotten around to putting on a less performance muffler, so I cannot say for sure that the muffler is the cause, but I am pretty confident it is. Do any of you have an idea of a muffler that has more flow than stock, but not as much as an open one, with a nice mellow tone for out on the trail?

This is what exactly happened to me when I put the high flow Downey muffler on, after the headers and the highflow cat, and the exhaust valves are stock. I have plenty of power at 3200 and above, but the low end torque is gone.

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>>>*Yes, exactly the risk with a too free flowing system on any vehicle.
Likely the muffler complimented the header, and moved the powerband higher.
This is why I personally feel that some intake flow must be added, this does help some with that.
One could advance the camshafts a couple of degrees, perhaps. The computer might not like that much, though.
It would be easier to put manifolds back on and keep the pipe and muffler setup.
Restricting in the pipe and muffler is the wrong place to create backpressure....It does have that effect, but it also affects mid and top end...Tricky stuff with modern engines....*EB

I was going to mention adjustable cam sprokets and what you thought about them. I was also going to ask if you could go to a larger seat with just a 1mm OS valve? It seems to me that the seat is the odd part when looking at the exhaust port. Looks more like some sort of snap in restrictor the way it shrinks the entrance to the exhaust port. I was going to order a perfect power SMT-6 to fix any computer problems after I get all the hard parts bolted on and modified. Id also like to get a wide band o2 meter but thats not going to happen till Im done with hard parts and mods.

okay EB...

in 25 words or less. tell us, the many 3vz-e owners, what MUST be done to it to get that 30+ hp gain...

btw, it must be CARB legal... <img src="/forums/images/graemlins/wink.gif" alt="" />


one dude on yotatech is claiming he can change the top end using camry v6 parts and keeping the bottom end.

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>>>*...*Uhhhh...*LOL**...K....dang. (I can't drink a cup of coffee in 25 words or less...)

"*Red button on dash"...(That's just four words but it works...)

Seriously, my personal feelings are that this engine design came out to be a bit breathy for the Toyota folks. They simply backed it up 20-30 plus ponies when they tried to increase the low end power.
Ford did that back in the early 70's, there are other examples. Factories do take shortcut$$$ when dollars are involved..

I concede, it is what I think, for what that is worth. Over and over I hear the reports of freeing up the exhaust and losing low and midrange pulling power.
So bigger valves, some port work, free exhaust, yep, I see 30 ponies. Soften low end? Yep, that too.

Like I said, I am interested too. So this is all just an opinion of a 61 year old coot that has been doing engines for 40 years, with no real actual test history on the 3V to back up the best guess. To top it off I am sitting at my kitchen table in my underwear at 5:30 in the morning as I type this. So don't look at me to be no Expert, I just poke sticks at stuff to see what happens. It just looks like fun to me to try and make something a bit better..

On changing the heads to the 24V, yep. Need the Camry pistons, though..(*Valves kinda run into things otherwise) .But why bother? Just go get a Camry engine...same thing, even to the bearings and rings...*EB

That's great EB, heck I'd like to read 25 pages of your thoughts on this engine. <img src="/forums/images/graemlins/smile.gif" alt="" />

If someone swaped in a Camry engine would the stock ECU work or would you need the Camry ECU?

Since I don't use the powerband much above 3500, could I get away with running a more restrictive muffler than the hi-flow, without suffering adverse effects to the engine(longevity), in your opinion. I would rather not have to put back on the exhaust manifolds and x-over if I don't have too, it was PITA to take them off, and I already had the heads off at the time.



With the 3.0 I am not sure if this would be any better than what I have now. About a year and half ago I had the exhaust seperate prior to the cat while driving down the highway. I immediately noticed a loss in power, not a gain. I understand that the a free flowing cat/exhaust isn't the same thing as no exhaust at all, but it seems that some type of back pressure from the exhaust system is still needed.

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If someone swaped in a Camry engine would the stock ECU work or would you need the Camry ECU? [/quote]

>>>*Never have found where they hide the ignition points on those...*LOL**..
Way out of my line, but I think I would use the Camry system...Bet some of the other guys are way ahead of me on that stuff....*EB