1nz-fe Cam Swap

Thank You TMR-JWAP. i checked it out but i have a number 37. i dont see any odd numbers on the chart you mentioned. so i am unsure that thats what i need. any other suggestion?

 

Just to close out my question. i borrowed a micrometer and measured all my camshaft followers or valve shim buckets.
i learned that the stamped number indicates the approximate size of the "shim" of the bucket.
36=5.37mm 37=5.38mm 38=5.39mm 39=5.40mm 40 = approx 5.41mm

I zeroed out the micrometer before measuring but all the measurements is +1 from the number. not sure why.
I was expecting some wear and corresponding lower reading but amazed there isnt any. hope that helps someone.

also wanted to mention how badly carboned up the engine is inside and the exhaust valves @220kmi.
a good idea to do a refresh with piston ring update specially if its burning a qt every thousand miles if you want to keep the car.
i'm giving this to my son hence the work.

 

I finished the engine rebuild a few months ago and just now started on the engine swap, work and school kept me busy.

Got everything swapped over in about a day and a half. Upon startup of the rebuilt engine, a ticking noise started to develop. Initially i just assumed it was the valves being noisy, but after it warmed up a little bit the noise got VERY loud and I shut off the engine. This happened at about 9 pm so I gave up, decided to get back at it in the morning.

In the morning I managed to get the engine out in just under 3 hours. (It doesn't take as long the second time around) I drained the oil, it looked fine for the most part. No large chunks of metal and just a tad shiny from the fresh rebuild. Fearing the worst, rod knock and maybe a ruined piston, I tore off the lower crankcase and oil pan. To my surprise everything looked to be in perfect working condition. It wasn't until I took the head off that found the real issue, the valves were contacting the pistons.

It looks like the exhaust valves are touching very slightly and the intake are touching a bit more. It is very light, and as far as I can tell the valves are still fine. After a few hours of research I believe I have narrowed it down to a couple reasons:

1) I may have been using the VVT-i gear from a prius, instead of the matching VVT-i gear from the Scion X-b I pulled the donor camshaft from. I know they are different part numbers, but I'm not sure the precise difference between the two.

2) The valves are protruding too far from the head. I haven't been able to find a spec for how far they should be protruding, maybe someone here has access to that info.

As of right now, I installed the correct 1nz-fe intake camshaft timing gear and am debating whether or not I should take a dremel to the pistons where the valves seem to be contacting. This would fix the issue if the valves were the problem, and only be a little extra work if they aren't.

I know this isn't an active thread anymore, but anyones opinion as to what might be happening would be greatly appreciated.

 

Update:

I believe the issue is to do with the intake camshaft timing gear VVT-i assembly. When bolting down the gear to the camshaft, the manual specifies to take care not to torque down the gear in the locked position, as that may result in it getting stuck in that position. (I can't remember if i messed this process up during the initial rebuild.) I am still a little confused however. This should be the most retarded position for the intake cams, so theoretically if it were stuck, the pistons and valves should have never met? It could also still be an issue with using the Prius VVT-i cam gear instead of the Scion xb/yaris one.

The bottom half of the engine is reassembled, so while I wait for the gasket maker to cure I'll double check that I install the camshaft timing gear correctly. (I'm waiting on a new head gasket so full assembly probably won't be until tomorrow) I may also use a dremel to grind down the spots where the pistons were hit by the valves, maybe it will help prevent any bent valves.

I suppose the upside to all of this is I'm getting to know my engine and car very intimately.

 

Alright another day down, I'm lucky school doesn't start for another week.

I'm starting to think this isn't really possible.

To restate, the problem I'm having is that the valves are contacting the pistons. This seems to be due to the extra lift the 1nz-fe camshaft provides.

With the VVT-i in the fully retarded position, which is the standard position during startup and before oil pressure is applied to it, the valves clear the pistons without issue.

I tested something tonight by rotating the intake camshaft gear one tooth advanced compared to stock. This simulates the VVT-i advancing forward about 20 degrees, which is about half of its total capability. In this configuration, the pistons contact the valves, not allowing the engine to fully turn over.

I'm not sure what DivideByZer0 or Toyota Jesus did to make this work, but I just don't see how it's possible. Perhaps grinding down the pistons to increase the depth of the valve relief might help, but I think the amount I would have to remove might destroy the pistons.

I'll hold onto hope perhaps a day longer before I call it.

 

(Sorry for the duplicate posts, I reported them as copies but don't know how to delete them)

Last night I measured the total length of the camshaft lobes. When comparing the one from the Prius 1nz-fxe engine to the 1nz-fe, I found the lift is about 2.3mm higher on the 1nz-fe. This means that the 1nz-fe valves enter into the combustion chamber a little less than that 2.3mm further than the 1nz-fxe. (The valves enter at an angle, im not entirely sure what that angle is but it's fairly close to 80ish degrees)

I believe the reason for this happening is because of the differences in the pistons. When looking at pictures online comparing the 1nz-fe piston to the 1nz-fxe piston, there is far more material removed to make way for the valves on the 1nz-fe pistons.

I could try and remove that material myself on the 1nz-fxe pistons, but without the proper machining knowledge and some sort of flycut jig, I don't think that would turn out well. I'm also worried about needing to remove so much material I cut into the ring lands or severely weaken the pistons face by cutting too close to the other side.

Another option would be to somehow space the head further away from the block with a thicker gasket. This would lower the compression ratio a small amount, which could be a good thing. However I haven't been able to find a company that already sells thicker head gaskets for this engine, and having a custom one made is cost prohibitive. I would need to stack between 4-6 stock head gaskets to get the correct amount spacing and that is just a bad idea.

I ordered a set of 1nz-fe pistons from toyota and plan on running those instead. Obviously I lose the high compression, but what I get back is a guaranteed fit and the ability to use 87 gas. (as well as a possible longevity boost, I can't imagine running high compression in a prius block is very good for it)

IMG_0044 by Nick #1 posted Aug 14, 2021 at 10:32 AM

IMG_0045 by Nick #1 posted Aug 14, 2021 at 10:31 AM

 

Hi Nick #1. I admire you tackling this with so much attention to detail. Learning a lot from this!

 

WARNING, REALLY LONG POST AHEAD FULL OF DETAILS YOU PROBABLY DON'T NEED TO KNOW

TLDR: I was able to figure it out, swapping the intake camshaft does work.

Four engine swaps and one month later, I'm back. Mostly lots of head scratching and cursing at myself for being impatient and subsequently making mistakes because of that.

First off, the answer to my original problem of the valves contacting the pistons: I'm stupid. Turns out I installed the pistons backwards during the first engine rebuild. The intake valves were contacting the exhaust side of the pistons. I was pretty embarrassed and thought about not even mentioning it in this write up. But here we are! This is my first time rebuilding an engine soo I figure that's a good enough excuse.

I ended up rebuilding the engine and installing 1NZ-FE 10.5:1 pistons. Unfortunately this didn't work out either. Every parts store (Except toyota themselves, I should have listened to the manufacturer) lists the piston rings for the 1NZ-FXE and 1NZ-FE as the same part number. This is wrong, the 1NZ-FXE uses thinner piston rings. I installed prius piston rings onto a yaris piston and this resulted in exorbitant amounts of blowby and oil consumption. (As well as less power than even a stock prius engine)

I didn't discover my mistake until a few hundred miles later. I drove that iteration of the engine for over 1500 miles without any other issues. Another weekend later I swapped the old engine back just for fears of engine failure.

This past weekend I rebuilt the "new" engine... again. *sigh* This time I installed brand new OEM 1nz-fxe pistons with the proper rings, and took special care to follow every step in the repair manual.

200 miles on this engine, so far no oil burn. I'm still in the break in period and will report back my experience in a couple days.

 

It has been about 10 days since my last post, thought I'd write down my "final" thoughts on the matter.

1200 miles in, no oil burn. I was concerned that the extra compression would cause more blow-by. It may have slightly more than an otherwise stock engine that has been rebuilt, but it's not noticeable and I don't have the equipment to test it.

Some notes before I go into the experience of driving w/ the 1nz-fe camshaft.
- My prius is currently running 215/75r15 General Tire Grabber ATX tires. These weight 30 lbs each, 12 lbs more per tire than stock. This slows down the car significantly.
- The larger diameter tires means my speedometer is off by about 13%. ( 30mph indicated = 33.9 actual; 60 = 67.8; 90 = 101.8)
- The hybrid battery is on deaths door. It is the original that came with the car 14 years ago and logged over 270k miles with the original engine. It has very little capacity and (before the engine swap) when driving with the a/c on, it would routinely hit red and resort to using exclusively the ICE. Not sure how it has made it this far without throwing out the triangle of death.

Thoughts:
- The first noticeable difference is the kick back on startup. It is a lot more violent than stock and is a little worrying at first. I haven't noticed it causing any issues however, so I've been able to get used to it. The annoying part is in stop and go traffic where the ICE will shut off and the engine starts and stops 10 times a minute.
- Acceleration is improved. I regret not taking actual measurements before swapping the engine, but on the upper end when the battery would usually lose umph the ICE is able to fill in the gaps.
- Fuel efficiency is unchanged, if a little lower just because it's more fun to hit the gas now. Because of the dying hybrid battery, larger tires, and roof rack, I only get ~ 33mpg combined, even before with the stock ICE.
- The most noticeable difference is on the freeway at speeds between 55-80. Before, with the original ICE and larger tires, the engine would have to turn at about 4000 rpm to keep up anywhere above 70mph. As was stated by someone in a previous post, it seems like the engine is turning 1000rpm less in any given situation. I believe this has actually increased my fuel economy at highway speeds. On flat ground I can now cruise at 80mph while turning 2800-3000 rpm.
- After going through this forum one last time, I caught that DivideByZer0 actually used the exhaust cam from the 1nz-fe engine as well. I only swapped the intake cam. The exhaust camshaft from the 1nz-fe has about .5mm more lift than the 1nz-fxe. I'm not sure if I'm leaving any power on the table by running the stock exhaust cam. Maybe I'll try swapping it in at some point. Right now I just don't feel like redoing the valve clearance again.

I've been running exclusively premium (91 octane) gas without any apparent issue. Thank god for costco gas, I'm paying ~4.15 per gallon instead of chevrons 5. (Gotta love california -.-)

Thanks to toyotajesus for initially trying this out and posting. It has been a great learning process for me considering it's my first time rebuilding an engine. Also thanks to DivideByZer0 for doing so much research on the part numbers and logging every step of his journey. Super helpful.

 

Nice job, I'm glad you got it all sorted to your satisfaction.

Seeing as you feel the car is worth putting a new engine in, complete the powertrain upgrade with a new replacement set of HV battery modules from newpriusbatteries.com or a new OEM if you can get it for $1650-$1950. Without a new battery, there will be undue wear on that engine and you will be back to where you started.

With a new battery, see that car go.

 

I've done it in mine because I couldn't find a good condition fxe. The only things that need to be transferred engine wise is the valve cover from the Prius engine. The harness from the Prius I direct bolt on. The only thing I haven't done is take it to a tuner to increase the max rpm in the ECU to be able to squeeze all 120PS from the engine or even more with a custom map. fuel economy is almost the same. I had 4.7/100km with the old engine and 5.1 with the current setup.(all the accessories and manifolds also will need transfering)

 

I thought that you mixed up the pistons, but this doesn’t seem likely, why don’t you publish photos, it would be immediately clear what’s going on