I am replacing my friend's engine after one of his VTC's blew up. I was wondering if it is possible to replace the VTC's with the exhaust cam gear to eliminate the problem altogether. Has anyone done this? Will it line up the same way as if the VTC's were grounded?

-- some history --

This car is my old car and I replaced the engine about 60K ago with a used engine. The VTC's were operational without ticking for a long time, and when they started to tick, we grounded them. This worked for a while, but we did something while working on the engine possibly shorting out the connectors. After this, the VTC grounding did not appear to be affective. It was driven in this condition for about 15K or so before the helical gear exploded, ruining the timing chain and busting the timing chain cover.

 

If I'm not mistaken I think its JWT or someone makes VTC disable kits for the VG30DE. Maybe it would work on the VE?

 

I asked this question not to long ago, Matt said he might look into it, hmmmmm

I'll just screw around with my spare motor tommarrow and see what I can do

 

Was this the post you were looking for MrGone?

http://forums.maxima.org/showthread.php?t=311181

Czar, if you read the thread you can see that we were hoping that you knew something about it. I guess not

 

I went back and read the post I made a few years ago about putting the exhaust gears on the intake cams. I probably was talking out of my *** back then, knowing what I know now, and what I've done with cars. It was an idealistic thought that did not have incredible consideration behind it. However, after pulling the valve cover, I am definitely going to look into it. I asked the question because I haven't been involved much on this board for two years, and thought maybe some one has tried it.

I need some refreshment in VE architecture. When the VTC's are grounded, no oil pressure flows to the VTC, and ideally the spring holds the helical gear towards the cylinder head right? I don't doubt that the engine can run with the exhaust gear, but I'd like to find the exact variation of the cam angle with the exhaust gear from grounded VTC angle.

If no one has done this before, I will get some exact angles and post them here for posterity, along with pics.

 

What about oil pressure. Since the VTC is a part of the oil gallies wouldn't removing them cause a adverse effect on the oil pressure. You will have to find a way to plug/block the oil supply orifice for the VTC's.

Looking at these pics and going from memory it does seem possible, but can someone explain to me why would you want to put the exh cam gear on the intake side, besides totally eliminating the VTC's. The time and hassle it would take to swap the cam gears you could have rebuild the VTC within the same time.





MIKE

 

Normally the exhaust lobes have different profiles to the intake lobes - the exhaust valves usually stay open longer than the intake valves and have different lift profiles.
And thinking of modern engine design & packaging, I suspect that both cams don't sit directly on top of the valve stems and use rockers instead (haven't pulled the cam covers off a VE as not too many in this country so could be wrong about the rockers), so you'd expect the cam gear line-up marks and keys will be completely different to each other.
Therefore, one would surmise the camshafts are not inter-changeable.
No harm in trying, though!

edit: okay so I've just seen those pix, so the cams do sit on top of the valve stems! I still think the exhaust cam timing & lift profile is gonna be different to the intake cam - esp as the intake "rotates" to change the lift & timing characteristics at a certain engine speed. The exhaust cam's gotta be designed to compensate for that so will have a more "generic" lift & timing profile.

 

I dont think they are refering to swaping the cams (intake on exhaust side and exhaust on intake side) they are refering to removing the VTC sprocket assy on the intake cam and installing a exhaust cam gear.

MIKE

 

Oh yeah, looks like completely missed the point!
Wouldn't the cam sprockets have completely different locating keyways so you can't swap them by mistake?

 

The cams do not touch the valve stems, their is actually a bunch of little "rockers" there. It's a roller in the middle, then one side pivots off a 'lifter' while the other side pushes on the valve.

 

how exactly do your VTC's "blow up"? is this possible?

 

Yes, it has happened a few times. AFAIK, they become cracked over time and pieces of them fly off the sprocket and wreak havoc to the engine.

 

Red92MaxSE isnt going to like this thread

 

It is making my wallet hurt just thinking about it...

 

if the cam gears were able to be swaped they would have to be the exact same size and have the same amount of teeth or the intake cam would spin faster or slower the normal but i am guessing that they are the same size

 

they should be the same size otherwise you'd have a really goofy running engine.
The cams MUST rotate exactly the same speed so the amount of teeth will be the same. The question lies in mounting depth (gears must be exactly aligned with one another) and where the alignment pin is for timing.

 

I'm sure the mounting depth is the same also, but the thing to look for is the angle of the keyway as compared to the original sprocket. they would have to line up exactly in order for the engine to be in proper time- but 1-2 degrees may not really hurt much--- look at the adjustable cam gears on the honda and 'yota crowd.. they'll move a few degrees to alter the powerband of the engine, as well as our VTCs moving 15 degrees already.. Sooo, if you lined up everything properly and the keyways matched, there's no reason why it wouldn't work--- you'd just completely lose the VTC functionality that's designed in the engine. that means a huge power loss (about 15hp/tq) at either the top or bottom end of the rpm range.

 

The main thing we are trying to prevent is ANY future problems. After dealing with the VTC problem several times, I just don't trust them. The performance is secondary at this point. I was happy enough with the performance with the VTCs grounded, and if I could get similar performance with an exhaust cam gear, I would happily replace the VTCs and forget about it forever. This car isn't raced anymore, no need for those 14.8 sec. passes at near stock.

After some thought about the VTC grounding, the control solenoid should remain open all the time. This would allow the oil pressure to consistently push against the helical gear and compress the weak spring. So if I want the cam to be aligned to the grounding method, I would want to match the angle when the helical gear is moved as far as the spring will allow it away from the cyl. head, right?

Anyways, I plan on pulling the engine tomorrow, and taking pics of the blown up VTC.

 

If the VTC actually broke apart, I'd worry about some bent valves etc.. So make sure they aren't messed up before spending too much time on this engine.

 

We are getting a used Japanese motor, but I think the old engine should be useful to someone. The VTC didn't explode, per se, but rather the helical gear sliding around eventually hammered a section of the front of the VTC off. This piece found its way into the timing chain, knocking a hole in the TC cover. The timing chain got trashed but is still intact, i.e. its still in one piece. The long block is(or should be) fine. The metal broke off in big chunks, and if I can trust the filtration the internals are probably fine. Replace the timing chain, VTCs, and one of the covers, and its a running engine.

 

May I ask what problems have you had in the past with VTC's? Just wanting to understand your quest in disabling a valve timing mechanism. How many VTC problems could one man have?

MIKE

 

Would anyone happen to have the link to the VTC TSB thing that shows how to rebuild them?

 

MattFAQ You!
http://mattblehm.com/faq/VTC_tsb.pdf

 

thanks Matt

 

the keyhole/keyway on both intake and exhaust sprockets have a gear tooth directly above them. i just went to look at a set i have out of a motor and the do line up. the problem i found was that the the threaded bolts that secure the sprockets to the camshafts are not the right length for a exhaust cam sprocket to intkake camshaft combo. the other problem is that the the centerbore/hole on the exhaust cam is larger than the intake cam, so you will need a way to keep the exhast cam gear/sprocket centered on the intake camshaft. (ie a hubcentric ring of sorts)

shopping through the nissan parts bin would probably find a bolt that wil make it work. you also stack a few washers to keep the cam gear centered.








email - KLLRSPD@YAHOO.COM

 

I've had the VTC's fail 3 times now. First time I had the dealer replace them, they lasted about 3 months before starting to tick again. They were replaced again under warrantee. I didn't have trouble that time, rather my rod bearing wasn't able to hold up to 150 mph at 150K. After installing a used engine, the VTC's appeared to be cooperating. 40K later, the VTC's blew up after grounding them. This worked for a while, but eventually they started ticking again.

While I probably would rather leave things stock, my friend for whom I am replacing the engine for would like to eliminate the VTC's if possible.