Cam Instalation And Tappet Addjustment

[tas_ae71]

hi,

 

just replaced another 4ac, it has a rattle in the head which i belive most probaly is just tappets.

 

i have a reground cam that I'm planning to put in at the same time as i replace the old timing belt (kill 3 birds with one stone).

 

the cam has 290 degrees of duration and extra lift on the exhaust valves and about the same on the intake. i fitted it to an old head to look at the difference in lift.

 

questions:

-how do i know if the valve springs bind or what can i do to prevent them from doing so? will the std springs be fine? how likely is it for them to bind without wild amounts of lift although there is noticeably more on the exhaust side than std.

 

-how nessesary is toquing the bolts for the cam bucket correctly as i don't have a torque wrench?

 

-after some searching i found that the std (hot) clearance for a std cam is .008" inlet and .012" exhaust. would this be the same for the bigger cam and are these figures correct?

 

-is it possible to get a cold clearance? as by time i have swapped the timing belt over and get everything reassembled it will be cold? also i would rather not be working on a hot motor.

 

 

thanks

Edited January 29, 2008 by tas_ae71

[camerondownunder88]

The cam re grinder will tell you what specs to set tappets at. when I had mine reground he said to use the same he ground it to those hot clearance spces. Also if in doubt also ask the cam gringder all those questions he will answer them for you to.

 

Also on the torque I would torque them borrow a torque wrench if possible. alloy heads can get thread damage easy if you over torque stuff.

 

 

Cameron

[oh what a nissan feeling!]

1. They bind if all the coils are touching each other, once a spring has experienced this, it looses alot of strength.

You can check the bind on the springs by turning the motor over by hand and looking.

Probably need to know a bit more about the cam for anyone to give specific advice.

They are unlikely to bind without large amounts of lift, but you also have to consider valve bounce as a possibility as well.

 

2. very important that you use a torque wrench, you can break your cam.

 

 

3. the factory clearances should be fine, although the cam would have come with its own specs.

 

4. do them slightly loose of the settings given, warm the motor up, and then reset them.

[love ke70]

2. very important that you use a torque wrench, you can break your cam.

 

can't we tell you have an sr20 :hmm:

 

i would swap the valve springs just for the sake of doing it, so you don't have to come back again, but then again, u havnt done alot with the rest of the motor so your probably not expecting too much? so maybe don't bother.

binding is when all the coils "bind" together as the cam goes round.

 

torque the bolts correctly, stripping threads suck the nuts

 

get clearance from cam grinder.

i think it will be nearly the same.

set them around that point when cold, get it hot then reset them. as has been said.

[oh what a nissan feeling!]

can't we tell you have an sr20 07-nyahnyah.gif

 

Yeh, but ive never done it :hmm: Yet........

[tas_ae71]

thanks for the replys.

 

no I'm not planning on revving it too much as its my daily so i keep it under 6k so valve bouncing shouldnt be too much of an issue. with a std cam i have had them at 7500 without them bouncing with a pre flogged motor. also wanting a little more lift out of this motor, its my 3rd 4ac. when I'm a little more financial i may rebuild one with more comp that will rev a little higher, higher tention springs will drfinately be going in then.

 

i didnt get the cam ground myself and i don't even know who did so asking him is out of the question. it was an impulse buy about 6months ago. there where other people intrested in it and i got in quick and get it fairly cheap. i don't even have anything to measure the lobes with to get an acurate indication to the amount of lift it has compared to std.

 

i don't really know any person who would have one. i could drive it to the machanics and they could do it there its only a 5min drive. without much income spending is very limited so buying tools is out of the question at the moment.