Valve Adjustment regarding BIG CAMS

[metalmonkey47]

I've just finished compression testing my LZ after installing my new Nismo big bore gasket to check my numbers, and I'm still seeing a lower then normal number. 100 PSI cylinder 1 with the motor HOT. I dropped some oil in the cylinder and the number didn't change a bit, so I know the issue is in the head.

 

I was looking into valve adjustments but I don't have a factory cam. It's a Racer Brown .475 (275 degrees at .025"lift, 250 degrees at .050" lift and .475" lift at zero lash) with the correct lash pads. It's a racer brown 'Race carm' (signified by the 'R' ground into the back of the cam)

 

The only info I've found on these camshafts is regarding the street grinds, posted by Datsun Wizard.
 

I just thought that I would add something additional to this cam thread. Racer Brown back in the day, recommended that the lash be set at the valves( between the lash pad and rocker tip), not at the cam as you would do with the stock factory method- cam and rocker arm. Of coarse you need a narrow feeler gage to do this. Racer Brown cams had bad rap for being noisy, but I think that it was because lash wasn't adjust to his way, people just adjusted them with the factory method. Using his method is really the best way, it assures that there is clearance where it really matters at the valve - not holding the valve off of the seat. Because of the lift ratio of the rocker arms, which varies between rockers, you really don't know what the clearance is at the valve using the factory method. When I was building lots of L series motors, we would by 60+ rockers and using a dummy head and cam we would match the rockers for lifts in sets, so that the lift at the valve was consistent, for all cylinders. It is surprising how much the lift varied between the rockers. On the Racer Brown street cams he wanted .006" lash on the intake and .008" exhaust lash at the valves. Which if you divide this lash by the rocker arm ratio of 1.5 you have very little clearance at the cam/ rocker arm. Of course you need to adjust the lash with the engine hot.

 

I little added info from a old Datsun guy.

 

Monte

 

With that said, I'm purely assuming that since we checked the head with a straight edge when it was off for the head gasket, and that the added oil doesn't affect my compression numbers that my issue has GOT to be in the valves. 

 

 

Now I've never adjusted the valves on any OHC motors, just pushrod, so I'm going to ask the stupid questions. I've seen the video's and read the threads and none answer my questions directly. I'd rather not guess and break something.

 

The lock nut below the rocker must be the adjustment nut, but how does that affect the upwards and downwards movement of the rocker?

 

 

[Eagle_Adam]

Green dot is you adjustment nut, the black dot is your lock nut

 

 

 

 

 

 

 

 

EDIT    -     that ^^^^ is wrong

 

 

 

 

this vvvvv is right

 

 

 

i need to get more sleep -.-

[Eagle_Adam]

loosen the lock nut, then spin the adjusting nut until the clearance between your lash pad and cam lobe are correct, then tighten your lock nut. after its tight check the spacing between the cam lobe and lash pad to insure you diddn't tweek anything when you were tightening stuff down 

[KlassicMotion]

You won't break anything.  The best way to figure it out is to just get in there an get the feel for it a little at a time.  But actually, the bottom nut is the lock nut.  The top nut is the adjuster nut.  You will find that when you go to tighten the nut back up, your adjustment will change, even if you think you held the adjuster nut perfectly still.  You will have to get the "feel" for it with a couple tries.  I think you will find that you will set the valves a smidge looser than what you think it needs, in order for it to be right when you get the nuts tightened back up.

 

**Looks like Adam snuck two posts in while I was typing!  :P

 

**Also, the Datsun service manual says, if your going to do the adjustment "hot", you only have 10 minutes to do it before it's too cold.  I just set them when it's cold (double check), and check them again when it's hot.  Usually it checks out just fine. 

[Eagle_Adam]

as for what your clearances should be i have no clue 

[Eagle_Adam]

You won't break anything.  The best way to figure it out is to just get in there an get the feel for it a little at a time.  But actually, the bottom nut is the lock nut.  The top nut is the adjuster nut.  You will find that when you go to tighten the nut back up, your adjustment will change, even if you think you held the adjuster nut perfectly still.  You will have to get the "feel" for it with a couple tries.  I think you will find that you will set the valves a smidge looser than what you think it needs, in order for it to be right when you get the nuts tightened back up.

 

**Looks like Adam snuck two posts in while I was typing!  :P

 

lolz, someones done this before! :D 

[ggzilla]

Incorrect valve lash won't cause a consistent 100 psi reading on one cylinder.

[KlassicMotion]

I would suspect it's the rings still.

You should do a leak down test to see where the air is escaping too (crank case, or exhaust/Intake). 

I've heard bad things about the current owner of Racer Brown cams.  In fact I've read a few reports that he should be avoided at all costs.  I wonder if the cam was cut wrong.  Maybe your valves aren't closing when they should?

[Sealik]

Go 6 and 8

 

http://community.ratsun.net/topic/16539-l-series-valve-adjustment/

[Sealik]

Set engine at TDC....both rockers on cylinder 1 should have some clearance from the cam lobes

If not.....too tight

 

I always set lash with lobes straight up

[Sealik]

Another thing.....did you do a wipe pattern on the cam?

Also....I noticed your adjusting nuts are all over the place (height wise).....should be a little more consistent if everything is set properly and the head is in good shape

[zKars]

Green dot is you adjustment nut, the black dot is your lock nut

 

 

You may want to adjust your dot location. The Green dot is the lock nut, and the adjuster is the 14mm hex ABOVE the lock nut, just under the rocker arm tip.

[Eagle_Adam]

EDITED 

[Dime Dave]

I use .010" intake & .012" exhaust (cold) on my race engines. At 250 degrees at .050" lift you are pretty much a race cam. Comp Cams says .012" & .012" for their similar durations L series cams.

 

Sealik is right, check your wear pattern on the rockers. They look like the lash pads are all over the place on thickness. This could also be from a valve job where some valves were set deeper than other when they were reground.

 

High lift and/or high duration cams can quicker over run the rocker wear pad if the lash pads are not correct. And this will wipe out a cam in no time.

[Dime Dave]

Eagle Adam, you need to try again my friend,

 

The bottom, (black dot) is the adjuster base that screws into the head. The middle hex (green dot) is the jamb nut and the super thin hex right under the rocker is on the rocker stud to adjust it. When you get to the one on the far right its a bitch to get a full thickness wrench on it and one on the jamb nut at the same time. That puppy is wound to the bottom.

[Farmer Joe]

when i did the valve adjustment on eriks old race l20, with the big cam it had i set it at .010 intake and exhaust.. 

 

it has some that were always staying open just a tiny bit, and it ran like poop.. 

[Dime Dave]

#35 - Adjuster Base

#32 - Jamb/Lock Nut

#31 - Rocker Pivot Stud

 

[Eagle_Adam]

Eagle Adam, you need to try again my friend,

 

The bottom, (black dot) is the adjuster base that screws into the head. The middle hex (green dot) is the jamb nut and the super thin hex right under the rocker is on the rocker stud to adjust it. When you get to the one on the far right its a bitch to get a full thickness wrench on it and one on the jamb nut at the same time. That puppy is wound to the bottom.

 

yup, which is why i edited my last comment............

[metalmonkey47]

Incorrect valve lash won't cause a consistent 100 psi reading on one cylinder.

 

If the intake/exhaust is hanging over into the compression stroke, wouldn't that cause a compression issue? 

 

I would suspect it's the rings still.

You should do a leak down test to see where the air is escaping too (crank case, or exhaust/Intake). 

I've heard bad things about the current owner of Racer Brown cams.  In fact I've read a few reports that he should be avoided at all costs.  I wonder if the cam was cut wrong.  Maybe your valves aren't closing when they should?

 

My cam was ground in 1974 so no worries there :P This head has bounced around owners a bit, as an ex race head from the realm. L28 valves, 1 5/8th intake ports, nismo dual springs and retainers, etc. Not sure if it was machined from a reliable source or not. Leak down test will probably be a tomorrow thing. 

 

Another thing.....did you do a wipe pattern on the cam?

Also....I noticed your adjusting nuts are all over the place (height wise).....should be a little more consistent if everything is set properly and the head is in good shape

 

 

I use .010" intake & .012" exhaust (cold) on my race engines. At 250 degrees at .050" lift you are pretty much a race cam. Comp Cams says .012" & .012" for their similar durations L series cams.

 

Sealik is right, check your wear pattern on the rockers. They look like the lash pads are all over the place on thickness. This could also be from a valve job where some valves were set deeper than other when they were reground.

 

High lift and/or high duration cams can quicker over run the rocker wear pad if the lash pads are not correct. And this will wipe out a cam in no time.

 

I have not nor do i know how to do a wipe pattern on a cam. It all seems to be pretty well assembled from a glance, but I'm not experienced enough to know what I'm looking for in fine details, as L's are still pretty new to me. Everything appears to be in tact with no odd signs or strange noises heard. 

 

I did a dry compression test cold that only had 60 PSI on cyl 1. Warmed it up and got 100 PSI. After finding a few valves that were WAY too tight and had no clearance whatsoever and loosening them up, I have 100 cold. But my adjustment wasn't really 'to spec' following the above adjustment information in the original post since my feeler gauge isn't narrow enough to fit between the lash pad and the rocker tip. I'll have to make one tomorrow. 

 

After loosening up intake valve on cyl 1 I'm at 100 PSI on an ice cold motor. not perfect...but maybe it's an improvement. 

[Sealik]

Don't worry about setting the lash from the rocker tip....just follow Mike's video for now

Wipe pattern...

Lobe straight up and remove oil from rocker and lobe.

Mark edges/face of rocker about 1/4" up both sides with a black felt marker.....obviously lash has to be set prior to this.

Maybe set lash at .008 (intake) and .010 (exhaust) cold

 

Rotate engine so lobe cycles past rocker....pattern should be centered.

Like this.....sort of

 

Pattern could move to the left a tad...but not too bad at all

[metalmonkey47]

Ahhhhhh easy, what we're looking for is an uneven or worn rocker by following the oil wipe pattern? I'll do this tomorrow. 

[Sealik]

It's not a oil wipe pattern per say....it's how the lobe is contacting the rocker

Basically tells if you have the right lash pads to match the cam...you don't want the lobe running off the rocker...or....the lobe making contact too soon.

Some people slather the whole rocker with a felt pen....not needed because the lobe removes most of it

 

Thicker pads move the pattern to the valve side. Thinner pads will make the pattern/lobe run off the edge..(passenger side of engine)

[metalmonkey47]

Hadn't gotten a chance to do a wipe test since I beat my knuckle wide open when I was adjusting the valves (nice sized gash that probably needs stitches whatever though.) 

 

I noticed something that might clue me in though, I'm starting to see oil seeping in places I only last saw leak after the head gasket started leaking last time. I also have a radiator that appeared to be leaking and 'steaming' with a motor that's not quite even up to temp. I know the radiator's been leaking for some time, so i ordered my replacement today. I have a safety release cap on it, so I can bleed the pressure out the side when it's hot (long story, don't ask) and lifted the 'lever' to see how much pressure I had in the radiator, and it was FAR too much. In fact I had only seen that much once before when it overheated a long time ago (PRE-these issues. Thermostat stuck...) 

 

Pulled the oil cap and inside was a TINY little bit of foam. I'm kinda concerned based off of this, the rad pressure, and the oil seeping that I might have a head gasket issue again which is beyond insane, considering the head and block were checked with a straight edge and I'm using a Nismo head gasket with ARP bolts torqued to about 70lb-ft (ARP's suggestion). I was going to do a leak down test today but lost track of time. 

 

---I know the thermostat is shit. I'm making a run to Nissan for a new one probably in the AM, so perhaps that would explain the pressure in the radiator? It's not overheating though..in fact the motor was cold enough I could hold the radiator core without an issue after 15 minutes of driving in 25 degree weather.

 

---Would the foam in the cap be explained by moisture in the air/condensation? It's be very cold lately and we've been seeing rain/snow flurries. I do have the valve cover vented to the intake, and I'm getting a little moisture spitting from the vent when the motors warm. 

 

I'd like to try and narrow this all down before even thinking about having a head gasket issue again. Everything was triple checked before I re-assembled and I was very careful about doing it all by the book. 

 

 

Any feedback? Should I re-torque the head a few lb-ft tighter?? 

[ggzilla]

Don't retorq tighter than spec, or the bolts may deform. Just retoq to spec.

 

Yes, condensation can cause foam n the cap especially since its not bern driven long enough.

[ggzilla]

Don't retorq tighter than spec, or the bolts may deform. Just retoq to spec.

 

Yes, condensation can cause foam n the cap especially since its not bern driven long enough.