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Building a VG34 and installing it in my '88 Pathy


Mr.510
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How much money are you into it for?

 

I haven't actually added it all up. This was a very cheap build starting with a better than free motor, used pistons, no bearings to buy, etc. The major expenses were: Machine work $500 (boring, valve grind, wrist pin bushing honing). Gaskets & seals $275 (Ishino/Stone which is the OEM supplier to Nissan). Rings are $400 and Nissan factory are the ONLY way to go - everything else sucks, or so I'm told. Other misc. parts, T-belt, some hardware, tune up parts, etc. probably another $200. So $1400-ish is pretty close.

 

I'm wondering if you plan on or why you didn't go with the Holley 2 Barrel set up? Have you or do you see any benefits to keeping the TBI set up?

 

Carbs are not good off road, and this truck is mostly a wheeler. I know I'm answering for him, but I can almost guarentee that this is the answer!

 

Ding! Ding! Ding! Winner. Carbs suck off road because they slosh fuel on bumps and run crappy when off angle, especially when side-hilling. I've driven the truck back onto all four from laying on it's side against banks twice and could never do that with any carburetor. There's also fire danger from fuel spilling on hot exhaust when tipped with carbs. As a general rule I love carbs and hate fuel injection but not for this application.

 

Are you still running it with a total static timing of 17 degrees?

 

I'm running it at 10 degrees BTDC right now.

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Awesome white up! You have skills and a lot of nissan knowledge, and parts. I have a VG33 to put in my pathy and would love to build it into a VG34 but I don't have the equipment to machine those pistons. Doesn't anyone make a .060 over piston for the VG33?

 

After seeing the problems people run into mixing and matching parts, my plan is to use a VG30 crank in the VG33 block then use a VG30 oil pump and other accessories. I should be able to remove the block plate, add the threaded fitting from a VG30 and put my oil filter on the side of the block like the VG30? I know most people don't like the oil filter next to the starter but it has worked for this long.

 

Thank you for all the pics, I knew the heads needed work but now I know exactly what to do.

 

I was planning on converting my fuel injection over to the VG30E setup before changing the motor, I'm surprised you used the TBI setup. That would be alot easier! Do you think you will need to reprogram the ECU to get the full extent of your motor, or are you not worried about it just as long as it runs good?

James

 

Thanks man! I don't know what's out there in aftermarket off-the-shelf pistons? I think I stated somewhere above that the increase in compression ratio is a bigger factor in power output than the increase in displacement. With the Q pistons being just about exactly what you want to end up with they are pretty hard to argue with. They are not terribly expensive new, I can get them wholesale, and machine valve reliefs into them. If you want me too I'll quote a price for a set of Infiniti pistons and rings ready to drop into your VG block. For that matter I can duplicate anything and/or everything that's in my motor for anybody that wants one.

 

Yeah, all the Z31 guys pretty much use a VG30 crank when they swap to VG33s... though I hope that changes after my pulley adapter goes into production! I prefer the VG33 oil pump as it's the only gerotor pump in the SOHC VG family. The VG33's larger diameter crank snout is a plus as it reduces the load on the woodruff key that has been known to kill VG30 cranks. Plus VG30 crank snouts do break off just forward of the T-belt cog once in a while. I've got a couple broken cranks here. Oh, and I also very much like my new oil filter location! You can definitely alter the VG33 block to put the oil filter above the starter if you want to. Many have done it. You can see in my write up exactly what every fitment issue is if you keep the VG33 crank. If I were doing it again I would mill .300 off the oil pump bosses as that would make the alty tensioner and lower hose issues disappear.

 

I'm running the TBI for now for a couple reasons, the most important being that I have it, it works, and I don't have to spend money on it! I also wanted to see how well it works with a bigger motor. I have no doubt it will be a bottle neck and limit the power output of this engine, but right now it's limiting factor is definitely the exhaust. There is so much back pressure it sounds like a vacuum cleaner whenever I'm on the throttle, and that's with no cat. I have no doubt the TBI will keep the mixture correct, the issue is going to become it's limited airflow capacity.

 

I will be swapping to MPFI at some point as this engine will get turbocharged. I know I'll run the Pathy upper but I don't know yet which ECU and other hardware I'm going with. I'm trying to get Nistune to support the MPFI Pathy ECU as I want to develop a bolt-in turbo kit specifically for WD21s using the stock Z31 turbo to achieve boost at low rpm. I have a new-in-box '89 turbocharger and expect it will be into boost before 2k rpm with my VG34. My intent is to run 7psi with no intercooler and put somewhere around 300hp to the wheels on 87 octane pump gas. 300+ ft. lbs. of torque at 2500rpm would be nice too. :wub:

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Doesn't anyone make a .060 over piston for the VG33?

 

 

 

Sealed Power makes 0.5mm over (.020) for the VG33, so I would expect they probably would make 1.0s and 1.5s, but that is pure conjecture :scratchhead:

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  • 5 months later...

Update time! The VG34i has about 5k miles on it right now. It has the headers I produce installed and they are Chromex polished ceramic coated inside and out. After the headers is a 2-1/2" mandrel bent Y-Pipe, Mid-Pipe and Test-Pipe replacing the cat. Next is a stainless Flowmaster 50 Delta with a 2-1/2" mandrel bent stainless tailpipe exiting straight through the bumper 'school bus' style. :aok:

 

I've been having major difficulties with the engine management system in the Pathy since a few months before I swapped in the new engine. It's been getting about 9.5mpg around town and pulling about like the stock VG30 while sounding a bit 'off' and having major flat spots and stumbles. With the stock engine the truck was undriveable when it really acted up and didn't have enough power to maintain speed. The VG34, even running like total crap, easily keeps up with (and passes) traffic.

 

I replaced the injectors, MAF, TPS, CHT and harness, and CAS with good used parts. Each made a difference and each tested bad. Even after all that it still did not run right and was throwing the CAS code again. I found an '88 auto ECU on eBay and bought it for $60 shipped with a 30 day warranty. After swapping that in the truck ran like a top. I also noticed that it downshifts much more quickly if I'm rolling along and punch it. I had not noticed the trans acting poorly, but it's definitely much better with the new ECU. I guess a messed up ECU can screw with the TCU as well. :shrug:

 

After having it finally run decent and not throw any codes even during a couple hard sessions beating on it on the street I decided it was finally time for a little tuning. I started by increasing the initial ignition timing. I had set it retarded to 5 degrees BTDC for break in and to be extra safe with 10.3:1 compression and 87 octane fuel since I had no idea how much advance I could run with that combination. There is no knock sensor in the TBI system. I set it to the stock 12 degrees and had to lower the idle by more than half a turn of the adjuster screw. I took the truck out for a few 0-60 runs against the stopwatch and it improved immensely with the increased timing. If some's good, more's better, right??? With the VG30 I'd run as much as 20 degrees advance and found that it pulled best around 17-18. I set the timing to 17.5 degrees BTDC and the motor woke the f__k up! :lol: This made me very happy indeed.

 

At one point early on in the battle to fix the injection I made an inlet restrictor for the air cleaner housing. Some time before I had cut off the stock inlet neck and welded on a piece of 3" stainless tubing that connects to a fitting in the firewall with a flex hose so the engine draws it's air from the cowl. I changed the air filter in the truck because it was absolutely gross and it immediately ran like crap. Swapping the dirty filter in made it run much better. This got me to thinking that maybe the TBI MAF relied on the pressure drop across the stock inlet horn's cone in order to properly measure air flow? I already knew they ran like absolute garbage with the air cleaner top off so this sort of made sense to me. I pulled the stock inlet horn out of the scrap barrel and measured it's oval shape then drew it in CAD and analyzed it's area. I made an airflow restrictor out of .010 thick aluminum sheet with the same restriction size and attached it to the end of the inlet tube with electrical tape. The clamp for the flex hose held it securely in place. The truck ran much better this way so I didn't mess with it again.

 

Next up I installed a vacuum line from a fitting in the intake to my center console. I ran it through a grommeted hole drilled in a cover plate on the firewall as a permanent addition for testing. I hooked up my vacuum testing gauge and drove it around with Dennis reading the gauge. I read some guidelines on the Barry Grant (Demon carburetors) website a while back on sizing carburetors. He said that if an all out racing engine's vacuum at WOT at redline exceeded 1 inch a larger carburetor should be fitted as it is a flow restriction and is costing horsepower. He also said that on a street/strip car or similar 2 inches was acceptable and going to a larger carburetor would gain very little while screwing up drive ability. I finally had a definitive benchmark to shoot for in reducing inlet restrictions on various motorized projects.

 

I decided that since the truck was running great it was time to see what happened without the inlet restrictor so I took it out. I do not remember how much vacuum there was at WOT at 5500rpm when the trans shifts with the flow restrictor in place :( but the truck got quicker without it! :jig: So as it stands right now at WOT at 5500rpm I'm seeing exactly 2" of manifold vacuum. This is not so bad and much better than I thought it would be. I'm curious to see what stock MPFI Pathies have though that won't be a fair comparison as my engine should be drawing significantly more air. I did check the vacuum at WOT/redline in Dennis' S12 with a stock VG30E and it is zero.

 

So right now the Pathy on 33x10.5 KOs with a full tank of gas, most of my wheeling gear, and 160 pounds of ballast (Dennis) in the passenger's seat does 0-60 in 12.5 seconds at 12 feet above sea level and 60 degrees ambient. The rear diff is locked and if I'm rolling along in D at 25mph on dry tarmac and punch it the trans instantly drops to 1st gear and breaks the tires loose for about half a second before hooking them back up just before upshifting to 2nd. Next up I need to go on a highway trip to somewhere so I can see what the cruise mileage is....

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If it wasn't a wheeler my Pathy would have a Holley 350 on it right now! I like the fact that my truck can run on it's side, and I've idled it back onto it's wheels twice...

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  • 8 months later...
  • 6 months later...

My VG33 rebuild and swap is complete and has about 2500 trouble free miles on it now. This thread (and Mr. 510's adapter) were invaluable in getting it all done and together. I did run into one noteable difference that I thought I should add here for future readers.

 

The issues that Mr. 510 ran into with belt alignment on his alternator were not present in my 92 for some reason. With the new oil filter location I did end up using a different belt length (Napa part# 9390) and I had to fab up a new tensioner using C.O.T.S. hardware but otherwise it went together well. I used the standard swing arm and adjustment block but had to remove the tensioning bolt and replace it with the following setup.

4" all-thread
nut-washer-nut tightened about 1/2" from one end (to create a surface to push on the end of the original swing arm
nut-nut tightened in the middle (to create a sort of bolt head halfway down the all-thread)

in the end it looks like this ////NUTwasherNUT////////////////////////////////////NUTNUT////////////////////////////////////////////

that gets threaded all the way through the original tensioning block that is bolted to the alternator.

I should have taken pictures. Now it is WAY down where most cameras don't fit.

 

Set and tighten the original swing arm in its end position even though it is not long enough

The open end of the all-thread is run into the original tensioning block with the nut-washer-nut end stuck into the end of the original swing arm

Use the nut-nut setup in the middle to thread the new setup out of the original tensioning block and streach the belt.

Tighten up the pivot and tensioning block and its all set.

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  • 2 weeks later...
  • 1 month later...

FYI for all those going this route, you do not need to cut and weld the tab on the water pipe, Simply bolt it to the bottom hole on this bracket and everything fits just fine. This is how I did it and this is how Mr510 is now doing his future swaps.

 

2011-09-27_18-16-54_559.jpg

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  • 1 month later...

So, is Mr.510 doing these swaps for other people or just going forward on his pathy? :)

 

FYI for all those going this route, you do not need to cut and weld the tab on the water pipe, Simply bolt it to the bottom hole on this bracket and everything fits just fine. This is how I did it and this is how Mr510 is now doing his future swaps.

 

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To be more specific, he was with me when I discovered that little bolt hole and his words were something like "huh, I'll have to do it that way next time"

I know there was at least one 'next time' since then on a pathfinder but these don't just go into pathfinders and its hard to say how many more he will do and into what vehicles...

 

He will sell his available parts to any paying customer but beyond that, he picks and chooses who he works for and what he does.

Just buy his adapter hub and do the swap locally using this thread as a guide.

Edited by MY1PATH
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Ah -- thanks for the clarification. I'm looking at buying a 3.3 right now to at least do the swap. I'd like to add cams/bore/pistons like Mr.510 has.

 

I deal with software though -- the biggest thing I've done on a car is replace a starter and headers. :) If somebody was building these and I could just order one, it would give me an easier (though more expensive) option.

Edited by BikerJared
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  • 2 years later...
  • 1 year later...

I've been doing a VG33 swap into my 1994 D21 Hardbody Long bed. It came with the VG30E, which has 251k miles on it now.

 

My VG33E cams are currently at Schneider Racing getting their H256 regrind. The Z31 cams look to have better overall HP numbers, but I'd like to keep more low end pulling power. Stock VG33E cams might provide this, but my Hardbody is turning 3000 RPM at 60 MPH. The VG33E cams don't seem to be too good for this. Hopefully, the H256 grind will give me the best of both.

 

My reason for posting: I'm interested in getting a modified pickup-tube from Mr. 510. It does not seem like he posts here anymore, though. I'd like to keep the higher capacity 2x4 oil pan out of the VG30. I am OK with cutting and rewelding my existing pickup tube, but I don't know what to do to it.

 

Right now, all of the VG30E parts are still in the running D21 Hardbody. I am trying to do as much to the new VG33E JDM engine as possible before pulling the Hardbody engine to reduce downtime on the truck ...because I still use it!

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  • 2 years later...

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