Well i finally got them to finish the leak down test and the results were good. The cylinders ranged from 2.5-9%. The higher numbers don't bother me since the engine hasn't run hardly at all in along time and the rings probably need to build up pressure and get oiled up.

This kinda crazy that the leak down test showed up ok but i got compression test results that are f'd up. The front bank was 140-150 and the rear was 180-190. Anyone ever seen anything like this?

 

Stuck/bent vavles? Bad engine?

 

Improper cam timing.


A leakdown test is to determine whether or not there is good static compression, but a compression test determines if there's good dynamic compression. Your motor is fine, but the cam timing is off.

 

Nismo.... you didn't waste anytime changing the picture under your name....(LOL) Out of all people GP...... Back on topic.

So does this really point back to the timing which points back to the drilling of the cams? I hope not.

 

i don't know but i sure as hell hope not. I don't want to think that the cam drilling is off because if it was then both banks would be f'd up(i would assume). Stephenmax isn't your normal joe blow and i know he is a very maticulous(sp) person.

 

There's no way around it. The only way you can fail a compression test but pass a leak down test is if the valves aren't opening and closing at the proper times when the motor is in motion.

 

I understand that but i guess i am just wishful thinking it wasn't the cams.

 

Now get us some updates!

 

Hope you didn't crank the engine over with timing gears removed because you can bend valves pretty easily.

 

Jime,

Didn't Stephen drill your knock-off cams?

 

I thought he had the REAL Nismo cams??

 

Jime doesn't, Chris does.

 

New question.... if cams were supposedly drilled wrong but you had Tilley's new cam adpaters/cam spacers could you use the incorrectly drilled cams since adpaters will move the hole to where it should have been drilled for the dowel pins???

 

yes, the stock holes should be there.

by the way, the adapters tilley makes need modification to fit properly. I had to dremel some material off to make them work. Just an FYI for anyone doing the swap.

 

OK. I will keep the info in mind.

Mike

 

I decided to use JWT 3.0 cams for right now and i will dyno to see where i am at. They should commplement the setup pretty good since they have similar specs to that of the tomei cams. I guess we will wait and see.

Car should be back on the road no later than wednesday, but i have been saying that $hit for the past 4 months


All i want for my birthday is my car back!!

 

thanks buddy

 

Chris clear your PM box. I sent you an e-mail.

Mike

 

Almost positive your car will be working perfectly with 3.0 cams in it. Congrats in advance.

 

Good luck Chris.....

 

How much time did it take you?

 

i noticed something when aligning the jwt cams yesterday. First i lubed the cams up w/ lucas oil then tightened down the cam caps and torqued to spec. Well when i went to align the cams i found the REAR INTAKE cams to be very hard to get it turn as opposed to the others. I took out that cam and re-installed it according to spec and it was still hard to turn. Could this be a result of the valves sticking causing resistance on the cam? Note i made sure that crank was turned to where the valves wouldn't hit the pistons.

Also is there anyway that a stuck valve(or valves) cause a difference in compression like i was seeing.

BTW THIS WAS A CAM IN THE REAR BANK WHICH IS WHERE I WAS GETTING 190 COMPRESSION AS OPPOSSED TO THE 150 I SAW IN THE FRONT.

 

Stuck valves will cause you to have zero compression.

Since you're putting in different cams than originally came with the engine, it's possible that the wear pattern on it where the cam caps secure the cam is different and thus causing resistance. It could also be that they're not lubed up enough.

The only possible way that you can have low compression in a single bank like that is if you have 2 cams that are out of sync with each other. Basically what's going on is that the exhaust valves remain open too long for part of the compression stroke and the piston can't build up much compression on its own as a result. When you did the leakdown test where both the intake and exhaust valves were closed, the valves and rings were able to hold the pressure just fine.

Engine rebuild lube would be better than lucas oil for lubing up the cams and caps. It has a consistancy similiar to vaseline, but thinner.

Keep working on it. You'll really be happy when it's working. I was jumping up and down yesterday when I got my 3.5 running.

 

Welcome to posts 3 and 6.

 

I saw those. I was just explaining it again in a different way.

 

We also rigged up something so we could push on the valve to make sure it wasn't the cam causing the issue. When the mechanic pushed on all 6 valves he could barely get them to move.

 

I know you keep saying you checked clearances, but could it be bucket clearance?

 

The springs are fairly stiff and it's more difficult to apply pressure to the valves in the rear head than it would be in the front head. Did you compare the valves on one cylinder head to that of the other? They should all be equally difficult to open. You could also have a lack of lubricant between the buckets and the holes they go in.

 

I am pretty sure i saw him squirt oil down underneath the buckets.


Alex, yes i remeber him saying to me "man you got lucky, everything is within spec" just as he finished cheking the clearances.

 

Could he have mixed up the cam caps?

I thought I remember reading you should keep them in the same place...not sure why though.

 

No the cam caps were not mixed up.

The reason you have to keep them in the right spot is because the are machined for each location and the tolerances are very tight.

 

So in theory, if some were mixed up, the cam could bind or be loose, right?

 

to my knowledge yes.

 

Saw you were looking for a "left" side head on the 350Z board.

What's your plan?

 

well should the need arise, i would rather just swap on the complete head instead of tearing down what i have. But one thing i didn't think of was the fact that the 350z have stiffer valve springs than the max(according to sr20den thread). There could be other differences that i am not aware of but i am trying to educate myself on them.

I JUST WANT MY F%%%ING CAR BACK!!!!!!

sorry just having an emotional breakdown over here

 

I'd have taken a gun to that b1tch by now....

 

Nah thats to quick. I got a sledge hammer just waiting for that damn thing. If this $hit doesn't get fixed no one is going to see a SC'd 3.5(at least from me )

 

Any other opinions on this?

Is there any way that maybe that one or more of the intake valves on the rear bank are screwed up causing the higher compression in the rear bank?


I noticed that virgillo7 (has a altima w/ the jwt knock off cams) said he had a compression of 130 in both rear and front banks. So if cams drop dynamic compression by that much then maybe my rear bank #'s are the ones that are off and not the front?


Front bank compression= 150
Rear bank compression= 190