BDE cam gears - caution

Recently I've discovered a possible trap for the unwary when installing BDE cam gears.

When you install these make sure you run the car on the dyno with two lambda bungs, one per bank in the exh system, this will allow you to establish if both cams are fully advancing.

The BDE cam gears take twice as much oil pressure to operate and this can lead to a problem if the cam bearings are worn in the head - especially the front ones where the oil pressure is transferred to the inside of the cam.
(inlet cams only obviously).

I have found that the cams advanced perfectly when the engine was cool but once warm one bank only half advanced and the other fully, then when right up to temp after a long drive neither cams were advancing fully.

This can lead to a situation where the car may be tuned with a MAP sensor while at a higher temp with the cams partially working, but then when it is cool they will operate fully causing the engine to run lean = bye bye motor.

Just something to keep an eye out for & if you are building an engine to run the BDE gears run the cam clearances on the tight side to help with the oil pressure in the cam - remember you need twice as much pressure as the stock gears!

I tested them using compressed air and dry so not accurate but gives a general idea, the stock units operated at 12PSI whereas the BDE units required 22PSI. These figures will be lower with oil in the system due to far less leakage so as I said just an idea.
Based on the above it is very feasible that a "loose engine" could have trouble operating these gears - they certainly are not as forgiving as the stock ones.

 

Waiting until we have confirmed this is what was going on, it looks extremely likely based on the symptoms and evidence so far. I need to get the engine back together and up to temp again to confirm but I'm 99% certain this was the cause of the trouble.

I did note the BDE gears were very stiff to move and did not return to zero advance once the air pressure was released, the stock units are very smooth and return mostly with no help, BDE always required a twist back by hand. I would think that in the operating environment the oil and vibrations etc would see them return with no issues - I hope!

 

Right so the result so far is:

After pulling both inlet cams and adjusting bearing clearances to the lower limits no improvement on the operation of the gears.

Contacted BDE by email and then by phone, if we send the gears back he will have a look at them and replace at no cost if required.
Obviously we loose out on the time to remove, send back and refit.

What we have now is one gear working perfectly as far as we can tell but the other only partially advancing and sometimes sticking.
I'm seriously considering using some Promar in there to see if we can "unstick it" without another tear down and reassemble.

 

Its fair

but mungyz had to do the work, what a pita.

 

what did you do to adjust the cam bearing clearance?

 

Measured them all with bore gauges and found them to be elongated vertically (normal) so just used a plate of glass and wet&dry paper to remove material from the mating surface checking the amount removed with a micrometer. Then reassemble minus camshafts and check for size and out of round, make any corrections as required.
Then remove all cam followers and install the camshafts and check for freedom of rotation with all bearing caps installed and torqued down.
Take it all apart and put the cam followers in and check clearances between the cam and the followers as it will change from moving the centre line of the cam shaft.

All had to be done as part of the diagnoses but in the end does not appear to have been the root cause of the issue.

All in all we have lost three hours travel time to & from the dyno + gas + dyno time + my time for the day, eight hours to do the above tests and adjustments etc + any costs from this point IE: remove cam gears again and post them then fit new ones.
About $1500 down the drain & then it could be just a gamble that the next set is any better. I could pull the engine and replace the oil pump with a brand new one in the hope we get a touch more oil pressure (already is within spec) and hope this helps the gears. But that is a full engine pull and front + sump off = 12hrs at least so even more $$$ burned. And then one gear appears to stick half advanced from time to time...

Brett suggested that they could be just tight and need wearing in but they should not be tight and need to work straight off the bat otherwise we can't tune the car so then it can't be driven and they can't wear in.

What a fricken nightmare.

 

cheers mungy, a nitemare indeed

 

cant you shim the pressure relief valve on the oil pump and get more psi out of an older oil pump used to do this on 240Z car club car had 60 psi when oil hot good but got to be careful not over rev when cold

 

You can and I have on mine and Mikes had shims installed in the past by a previous builder, in theory if the valve is closed it's closed and so wont have any effect on oil pressure. Shimming it will help if the springs are getting old and are creeping open a little early.

With this engine we have 4 bar when cold and some revs and around 3bar at idle, when hot we have 2 bar at idle and 3 bar with some revs so within the range it should be.

When cold with some revs (so 4 bar oil pressure) if you power up the cam controller for the one causing trouble you still only get a partial advance so pretty much rules out a fault with the engine.
I put some Promar in there today to try my luck but no sign of improvement, at the end of the day it's looking more and more like the only fix is to try a new gear.

With the cam covers off and cranking the eng you can easily see there is good oil flow from both cams so rules out a blocked oil passage or jet.

 

Seven hours wasted on this today and the end result is I have fitted the stock gears and they are fine, working perfectly and with no noise even when up to temp (so far)

The BDE gears appeared to be in good condition but I suspect the components are not from the same units and so are out of spec causing clearance issues when hot.

I found the factor that caused them to stop working was actually temp rather than oil pressure, as soon as it hit 170 degrees F they started to fail, mix n matching components that are very close tolerance fit = not very smart.

I will NOT be fitting BDE gears to any future builds unless the owner accepts full liability for any issues arising for those parts, I'm out of pocket for literally thousands in down time because of these gears

How ironic the stock ones appear to be working fine at this point.

 

A correction to the above post: The internal components haven't been swapped, Brett suggested they may have been depending on condition etc.
I did check them today then completely forgot I had done it when I came home, I drove back in to work to check on this in case I was slinging shite around - turns out I was MY BAD.

BUT this doesn't really help and actually raises a bigger question/problem: if these are all the original unworn parts inside the gear except for the spring and back plate why do they fail to work on this engine?
If it is the engine causing it then how & why? we have oil flow to the cams and good oil & pressure, we have cam bearings well within spec, solenoids and valves working perfectly.
Yet at 170 degrees F and at 2 bar oil pressure the system fails why?
Stock gears are working perfectly (until they possibly beat themselves to death).

 

The search for the answer continues, Brett has been very good about the issue and certainly hasn't just walked away from it.

I have one more test planed before I send the two gears back for Brett to check over, I will place the gear in a conventional oven and get them up to ~180'F then test them again on the rig I built, this may provide a clue as to the cause of the fault - or it might not.

At this stage we will endeavour to tune the car with the stock gears on there while we are sorting the problem the car has with the BDE units, it's clearly something that doesn't want to give away its cause easily and it's of no surprise to me that it is this car that decided to have the issue.

 

Heating them in the oven will confirm if a mechanical "bind" when they reach operating temp. is the problem.

 

End result was the gears were sent back to Z1 (where they were purchased), when they go back to Brett we might get an answer. One gear is pretty much rooted now as it has been apart and back together so many times and had this that and every other thing tweaked trying to find the fault.

I've recently had a PM:

"Hey Mungy...

I am a Z owner in the usa, and seem to be having some consistent issues with my BDE sprockets. I signed up here mostly cause I found your post in a search, and wanted to find out more.

I have a fully built motor, including forged pistons and rods, extensive head porting, JWT 500 cams, ferrea vavles, springs, and retainers, and all the other go fast stuff.

My problem is that these gears "clack" when the motor is cold. one just barely, the other sounds like a spun rod bearing. "Clack clack clack" once with every revolution of the gear. When I touch the snout of the gear when the motor is running when the motor is cold, it feels like someone is hammering on the gear from the inside. The noise goes away to a great degree when the motor heats up.

Brett has tried to explain this away because of the heavy valve springs, or that someone has modified the oiling system, or the oil is too heavy and the viscosity is unseating the VTC piston. But the oiling system is stock, and the ferrea springs are less seat pressure than the JWT springs, and when I swtiched from 50w20 to 10w30 it made no difference.

The reason I am telling you this is I wanted to find out what you came up with in the issue you were having with those gears, and if you got some resolution.

Everyone I know says that heavier springs and bigger cams will ruin the VTC's pretty fast, but what is really weird is that I ran a stock set of gears on this motor for a couple thousand miles while the gears were getting heavier springs,and not a peep, click, clack, knock, ratttle, grrr, or any other sound that shouldn't be there. I am frustrated to say the least, and would love to hear what you came up with"


Hi

I spoke with Brett on the phone and via email about the issues my customers car was having and he agreed it would be cost effective for me to take one of the gears apart & see if I could find an issue. I spent a LOT of time testing and trying various "repair" options for that gear & even built a rig to bench test the gears, I only ever managed to make the gear worse.

Both gears have been sent back to Z1 (original place of purchase) and from there they will be sent back to Brett for his diagnoses, he will have a look at the other gear that I have not tampered with & give us a verdict.

It's annoying that we have fitted stock gears to the customers motor and that too runs fine so far with no VTC noise. I have recently fitted stronger valve springs and more aggressive cams to my own car and now have VTC noise but only when the eng is cold.

I am very tempted to try a couple of other options before going BDE gears:

1: remove the inlet cams, remove the valves from the end of the cams & enlarge the holes that allow oil to flow from the end of the cam when the valve is open.
This will in theory eliminate any chance that it is pressure build up in the cam even though the valve is open.

2: possibly insert an oil control jet in to the oil gallery at the bearing gallery for each inlet cam. This would really need to be done with the heads off BUT a good engineer with plenty of skill will be able to make this work with eng in situ - pretty tricky stuff though.

Both of these options assume it's an oil pressure in the cam issue - it might not be.

There is also the thought that if we were to ensure the gear was kept full of oil at all times but restrict the rate of flow in and out of the gears this would stop the pistons ability to clatter as it would effectively be in a state of hydraulic lock.
To make this happen would require fitting a pill in the end of the bolt that holds the cams gears on & depending on the ECU you are running possibly tune the VTC control valves to make sure the gears are full but there is minimal pressure in the cam.

I hope this has been of some help!

Cheers
Glenn.

 

Interesting to see what Brett finds with your gears .

I had some real heavy duty single springs and jwt mild cams with mine .
They worked fine with no noise ..


The only thing that happened with mine is that adjustment timing screws came loose on one and caused a clack/rattle noise ..

I'll see how mine goes when my engine is running in Jan... with Jun cams and ferrea's. I'll be using a MSD RPM window switch to run them.

flip side-------Could a set of BDE gears that dont work properly and hitting rev limiter at high revs possibly case a cam to snap ?

 

I'm running these valve springs now with absolutely zero issues. I do have solid Jun gears though.

 

those springs are excellent (should of kept them ) and had no problems when I was running both the intake and exhaust jun gears .

guess I'll wait and see if I snap a jun cam

 

Mungy, I am interested to hear what methodology you used to measure that one of the gears was not advancing as expected. I have BDE gears and do get some clacking from them all the time. I would really like to check just to make sure they are working correctly.