Loop320

Although new to the 2nd gen, I learned a couple things about this engine very quickly. First, it blows head gaskets early and often, second, the cross pipe design is “horrible” and results in cooked exhaust valves. This truck had the head gaskets changed under recall in 2000, I removed them undamaged. So, after 20 years, 150k miles and one overheat event (PO) the gaskets looked near perfect. Similarly, the valves at number 5 and 6 looked great, absolutely no issues, and as far as I know they have never been adjusted. Not sure about the practice of installing aftermarket headers in these, that’s a sure way to dump more heat into the engine bay. Anyway, just my opinion I guess. She’s running like a new truck now, ready for another 200k.

Jimkola

Before investing in headers I highly recommend consulting with a 3vze driver here on this site on what combination of changes will make any real performance gain, and the cost. From my experience with customers ages ago, simply installing headers isn’t likely to make that much improvement. But see what they say.

Co_94_PU

iTrader: (-1)

His whole post was very tongue in cheek..

"3vze, blow head gasket left and right"
"My head gaskets were fine!"

"3vze cross over pipes cook the rear valves"
"My valves are pristine!"

"Install new exhaust is a must"
"Take off my thick cast exhaust manifolds and replace them with paper thin tubes to cook my under hood components, no thank you!"

scope103

I don't know if I would call it tongue-in-cheek. I took it as refuting the common "complaints" that seem to get repeated without any basis. In a humorous manner.

Andrew Parker

As my story goes the 5 spd 91 4Runner I acquired in 2018 was bone stock and had 232K on it and it had some very tired 32x11.50 R15's BFG's on it but were replaced with 31x10.50R15 Cooper ATłs to get it home. I put a couple of thousand on the odometer and then the #1 cylinder let go on the Cajon pass out of LA on interstate 5 near Castaic, Yup 4th gear then 3rd gear at WOT and then a whistle from the radiator cap and crap the temp gauge is in the red and had to limp it back about 5 miles to get with in 100 mile of my house for AAA to tow it home. Cylinders #1 and #6 are at the opposite corners of the engine but share the same HG geometry were a blind water gallery gains access to the HG and has the shortest distance to the HG's compression ring and cylinder. This is were mine started to blow antifreeze into the cylinder and promptly started sending coolant into the EGR. The tailpipe looked more like I was running a steam engine during the limp back drive to the point where it basically quit running at mile 99 from my home.

My 4Runner had Feld Pro HG's in it so they were likely the recall HG's and not original. A few months later I tore into the engine and after the assessment I figure it is time to do a complete rebuild after I see that number 6 had a peppered head surface and the piston crown was peppered as well because the spark plugs insulator had cracked and fallen off the electrode and got pulverized to bits. Those insulator parts had basically plugged up the catalytic converter as well upon further inspection. So I tore down the engine and had the block bored and decked for MLS-HG's (ARP head studs too) and the crank reground with new pistons, rings and big end journal bearings on the hung conn rods. Three of the six original pistons had wrist pins that were stuck in the them which was probably attributed to the overheating when the HG let go. In addition there was cylinder wall scuffing and piston skirt galling on the three cylinders where the wrist pins had seized. On the heads I lapped the intake valves and seats which cleaned up. But I had to replace the exhaust valves and lapped those seats as well in order to get an acceptable valve job completed. I then went through and cleaned up the heads and lapped them flat to a mirror finish by hand. The intake manifold and plenum also were worked over with a die grinder and some sanding drums that work really well but don't last very long when spinning at 10K RPM. I port matched the heads with a set of Doug Thorley long tube Headers and later reworked the slip together joints with turbo flanges and compression rings to seal it up better. I installed a nice large well tapered Magnaflow CARB compliant CAT with 2-1/2" inlet and outlet. I later made a new CAT-Back exhaust with 2-1/2" tube and a FlowMaster FX muffler to replace the OEM muffler. The intake has a Summit version of the K&N FIPK with a custom made insulated aluminum air-box which draws cold are through the OEM baffle that is behind the PS headlight. The injectors are the four hole type but make a hell of a lot of racket. I have recently replaced the original distributor as the OEM had a signal coil fail and thus no spark no start at home in the garage, great place for this to happen! I noticed that it was struggling to start first thing in the mornings. Then once one of the signal coils had looked like it was cooked then the no start was the result. That has all gone away with the new distributor as it again snaps to running when I cold start it in the morning. It is a very satisfying start-up and rumble. I just eclipsed 247,500 miles this weekend and have had plenty of seat time with the timing set at 14° because the harmonic balancer has likely shifted its timing mark a bit and I haven't taken the time to see how bad the rubber sleeve is. But it runs a darn sight better at 14° than it does at 10°. The FlowMaster FX is quite noisy so I have been running a FlowMaster HP-2 in place of the CAT until it is smog check time again and this has provided some much needed back pressure and the ECM seems to have taken a good read on this set up. With the back pressure the off idle to acceleration is smoother and better when doing technical 4wheeling when a lot of starting and stopping is required. On slight uphill grades and on flat ground the 3,500 to 5,000 roll on is quite good and it is a very different feel from my Son's stock 1990 4runner who cannot catch me on the way up to Big Bear, CA.

I recently ran the 4Runner to Mammoth Lakes California from Orange County and it averaged 15+ MPG going and 16 MPG on the way home although I was not pushing quite as hard on the way home because one of the inner front CV boots had split. But I was pushing 70-80 MPH most of the way. The grade out of Bishop that heads to the Mammoth turn off is steep. This assent is a high altitude climb to 7000 feet and I had two MTB's on a bike rack along with a bunch stuff in the rig so it was fairly loaded but not maxed out. As I crested the pass I was doing 55 MPH in 3rd but not fully ringing her out. At that moment I was missing my prior 4.6 L HSE Range Rover and was wanting for more power. So for all the cost and handiwork the end result is not quite the same as the extra 1.6 liters that my Range Rover had and what is more we are talking about a 3.0 L V6 with 140-150 HP vs 4.6 L V8 with 220 HP both sharing about the same chassis weight. But the RR was lucky to get 11 MPG and only ran on Premium or it would not start if you put in regular grade gasoline. But that is another story!

The 3VZ-E is a quaint V6. The thing it is lacking is a supercharger option which would make up for the single set of valves this engine has for each cylinder and the lack of acceleration it has when in the driver's seat strumming through the first three gears. If the Pervia's SC could be easily adapted or perhaps an intercooled ProCharger worked into the mix then we might see a real screamer of a 3VZ-E? But I would get lower compression, forged pistons and maybe see about fully floating wrist pins to deal with the added thermal stress from a SC. That brings to mind a question, does anyone know if the the 3rd Gen's 3.4 L V6 have fully floating wrist pins in the pistons? All that aside with the headers, 2-1/2" exhaust, K&N FIPK and the massaged internals my 3VZ-E makes a great noise and when you rev it out it faily scoots along and will hold speed much better than it did when it was bone stock.

coopster

Good job on your rebuild Mr Parker. somehow missed this thread. At 2k posts / day thats easy tho.

The OP's pic sure looks new. Except I note the "racing stripe" on the side is missing, so was it painted? If not for the car in garage, I'd swear that was a much older photo.
Looks like a really good score.

Loop320

Hmmm, I bought this from the original owner, I don’t believe it’s ever been painted. Looks factory, also, original vin tags on all the panels and original glass all the way around. It’s an sr5, I don’t think they all came with the stripe.