L20b u67 head

[8m0untainman8]

Im going to ask them for more specific details and info in person, cam towers are in the correct positions. Also ive been thinking, if i knew someone with another l20b assembled, i could figure out the correct placement of the rocker arms potentially too because they have numbers engraved, im assuming they mean something... lol.

What risk am i running if the rocker arms dont go back in order, is that even okay at all? Is one new lash pad going to make things uneven?

Oohh the questions.

Datzenmike, then i can almost garuntee the old one is probably in the bag i took my head to the shop in, probably stuck to the bag, now smashed in a dump somehwere. None the less theyre working with me on the issue.

[8m0untainman8]

I am curious as to why the shop did not assemble the head they obviously took apart? Be sure you put the cam towers back in same position they came out of. How much was milled off? you might need to shim the cam towers.

 

Mike or Doc510 would be able to tell you at what amount of shaving requires cam towers to be shimmed. I do not remeber at this point.

I took it apart down to the rocker arms and assembly, they should have told me to finish pulling it apart myself.

[8m0untainman8]

I kept track of everything but what the shop did.

[datzenmike]

Nissan didn't number the rockers so who knows. Many an L series has been put back with the rockers mixed and there's no problem. It would be better if they were, but not the end of the world.

 

Before you install the rockers spin the cam by hand to be sure it does not bind. Lub the wear surfaces as you assemble it.

 

More important would be using an oil with a normal ZDDP level to prevent scuffing of the rubbing parts. All of today's gas engines use roller rockers so oil makers have been lowering the, now, not so important levels of ZDDP in them. Diesel engines still have 70s levels. Look up the controversy about ZDDP and older flat tappet engines and decide for yourself from an informed position. I won't be taking the oil companies assurances that todays oil is fine. I use 15w40 Shell Rotella T  (Chevron Delo 400 is also good, there may be others) and it runs just fine.If you  start using it, you may notice the oil gets dirty quicker for the first few changes. This is because diesel oil is higher detergent and will clean the crap off you internal engine parts. 

[kelowg]

By binding,he means. If it does at all the slightest. Cam likely to snap in two,also DONT OVERTIGHTEN TOWER BOLTS. Strip super ez. Tower shims should match amount shaved,correct everone??

[8m0untainman8]

By binding,he means. If it does at all the slightest. Cam likely to snap in two,also DONT OVERTIGHTEN TOWER BOLTS. Strip super ez. Tower shims should match amount shaved,correct everone??

Can someone verify this kind of info? Lol

[datzenmike]

I don't see why a shop needs to take the cam towers off to shave. If needed, do it yourself and keep track of all the parts and where they go and put it back exactly yourself. Same with rockers and valves if needed... do it yourself. Towers are notorious for stripping threads. One side is held on by the head bolts so they don't need over torqueing.

 

Unless the head is drastically cut or cut multiple times so that the bottom of the head ID number is trimmed off I wouldn't worry about tower shims. If 0.015" were shaved off, that would effectively lengthen the timing chain X2 or less than a spark plug gap. The tensioner will easily compensate for this. If you measure between the head surface and the valve cover surface, a stock uncut head is 4.249" thick.

 

If head was trimmed for warp, spinning the oiled cam without rockers in will say if it's also warped. Try loosening the center towers and see if it goes away. You could try shimming the middle or ends to try to effectively 'straighten' it. If very tight the cam is forced to flex as it turns. Fatigue will crack it. At what point will this cause a failure?? who knows.    

[8m0untainman8]

Thank you for your very real answers.

[banzai510(hainz)]

sometimes if head warped they will shave the top of head so everything has to be removed.(warped head thru and thru) Happen to me. But yeah I don't want to remove the towers if you don't have to and the tower bolts are only like 10-13 pounds and will strip ez

[8m0untainman8]

sometimes if head warped they will shave the top of head so everything has to be removed.(warped head thru and thru) Happen to me. But yeah I don't want to remove the towers if you don't have to and the tower bolts are only like 10-13 pounds and will strip ez

The cam towers, i just unbolted, and lifted off- on the cam still, kind of just how my friend lead me to do. When i discovered the piece was missing, and was being rushed to get as much done as possible still, i took the cam towers off the cam in order and bolted the head down, because i assumed i needed to assemble the rockers before putting cam in, was that wrong wrong wrong?

[8m0untainman8]

At this point i picked the missing piece up and am about to clean and out everything back together. Im going to slide the cam in and test to make sure it doesnt bind, can i put the rockers, etc in with the cam in?

[Crashtd420]

You really should look up the procedure.... the cam towers should have stayed in place and not removed

Rockers removed

Then the cam shaft.....

So when you put it back together line up the towers with the cam and then you install the rockers....

Therez a guy that has a bunch of you tube videos on how to assemble the lseries engine.... I forget his screen name but I'll get it in a second....

[Crashtd420]

This guy....

banzai510(hainz)

Watch his videos and stop listening to your friend....

[8m0untainman8]

Okay... so, either i need to take the towers off (which i really dont want to do) and put them back on the cam and re tighten, or figure out how to get the clearance to fit the cam in, even without the radiator it wont slide in because the front of the truck it there. Trust me i wish i could do more than listen to a friend and use my phone to look at a forum but sometimes this is how things go.

[datzenmike]

That's why Ratsun was invented.  Yes remove the rockers, or if they are off, remove the cam towers and slip them onto the cam. This means removing half the head bolts so loosen them all off. I assume you have a fresh head gasket.... this won't harm anything as the engine was never started. Install cam and towers together and bolt them down. Spin the cam to check. Put the head bolts back in and use the tightening sequence for the L head and do in 3 stages of 20 then 40 then a final 60 ft. lbs. Spin cam once more to check it.

 

R A D

7**....8

3......4

1*.....2

5......6

9**..10

 

* is the short bolt. Don't ever use head bolts without their washers.

**The head should have two alignment dowels in these positions

[Crashtd420]

Okay... so, either i need to take the towers off (which i really dont want to do) and put them back on the cam and re tighten, or figure out how to get the clearance to fit the cam in, even without the radiator it wont slide in because the front of the truck it there. Trust me i wish i could do more than listen to a friend and use my phone to look at a forum but sometimes this is how things go.

I believe this is all done with the head off the motor.... if you already had the cam towers off just do as mike said....

With no rockers in ...

install the cam.... in your case you should put it back on the way you took it off. Cam towers and cam all as one .. once the cam towers are installed and all the head bolts torqued and everything feels like it turns smooth then start installing your rockers.....

[8m0untainman8]

Thank you, i wasnt sure if that would be an issue to loosen the bolts again. That saves me some stress, ill look at the chiltons i got, and banzais videos when i go to time etc.

[Crashtd420]

The biggest thing that matters is that when its all tight and torqued that cam should slide in and out and rotate like butter....

[flatcat19]

Someone needs to go buy a feeler gauge set and a 1/4" torque wrench before assembly.

[hang_510]

can i put the rockers, etc in with the cam in?

They won't stay in if you don't.

[8m0untainman8]

This doesnt seem right to me, with cam in towers (in head) untightened theres no binding really, but the minute i try and tighten any tower bolts, cam wont even turn...

[8m0untainman8]

Doesnt matter where i start.

[Stoffregen Motorsports]

If the top of the head is flat, and you still can't get the cam to turn, then either there's a problem with the towers or they're a mismatched set, or you're doing it wrong. There is a certain amount of finesse involved with installing cam towers. Sometimes they need to be knocked around with light blows from a small hammer.

[8m0untainman8]

Okay, i just dont want to overstress anything. should the cam towers be tightened down with cam able to move before i retorque, or am i supposed to, torque head bolts before moving the cam towers...

[Stoffregen Motorsports]

They should be adjusted before the head bolts are torqued. If the cam still doesn't spin with the head bolts loose, likely tightening them up will not help the matter.

 

Install the towers with cam in place. Use a bit of anti-seize on the threads, snug them all and check to see if the cam turns. Proceed to torque them if cam turns. If not, knock them all gently back and forth and down until the cam turns, then torque the bolts.

 

You are using oil on the cam journals, right?

 

It is possible that you have a bent cam. Put the towers on the cam and set the assembly on the head, without bolts. Can you turn it then? Does it wobble?

 

There could also be burrs on the cam or in the tower bores, but I'm assuming you've inspected these beforehand. I'm also assuming that the mounting surfaces are clean and straight.