5K Cam Hep?

[snot35]

Actually, GJM makes a good point too, 5K push rods are ball both ends, your adjustable lifters will be expecting a cup. It just isn't going to work with Toyota stuff?

[altezzaclub]

google "hydraulic lifter preload"

 

Ah- feliix & camerondownunder

 

http://www.rollaclub.com/board/topic/11941-f-5krun-good/

[5ksev]

Before you worry about a fix, determine if you actually have a problem.

 

First step for you, google "hydraulic lifter preload" and read up. There may be some info on this on rollaclub, but limited. I think I wrote about it once before. Regardless, there is ample info on the net.

 

Once you understand it, you need to measure up to work out if you have a problem. Generally you should aim for 1.5mm preload. When you read up you wil learn how to measure it. Be advised this is a very finicky process, not difficult but you need to take care on a k motor to fleet accurate values.

 

It is possible that you won't have enough preload, the solution to this is to shorten your rocker posts commensurate with the difference in preload. For example if you only have 1mm preload, you would shorten the post .5mm to get the 1.5mm desired.

 

Any machine shop will easily be able to shorten the posts for you.

 

This is the simplest solution, you might have a lot of trouble finding the exact Length pushrod to suit.

 

Snot35 makes an interesting point about takeup of the lifter but it's not that straightforward. Lifter preload is the key. Read up you must young padawan.

 

A12 lifters are for solid conversions. Forget them, you have a hydro cam not a solid one.

 

thanks a heap!!! thats helped alot, and boosted my spirit again.. ill do that tomorrow and fingers crossed itl work out well :)

[5ksev]

quick question.. by shaving my rocker post's it will end up making my gear sit on an angle like this.. will that not be bad?

 

[altezzaclub]

No, it will be the other way around. Say, stock is horizontal rockers, then a ground cam will make them lean down towards the cam side as you've cut the base circle away. So you trim the rocker posts and that lowers them to horizontal again. I'll draw it in a moment.

 

OK, lets look at this. A cam is ground for more lift by cutting away the heel, as they can't add to the nose as easily. The lift is the ratio from the centre to the heel versus the center to the nose, so by cutting the heel distance smaller you have increased the lift.

 

So as soon as you fit it you will have giant tappet gaps, for if the pushrod sits on the ground-away cam heel the rocker will face up in the air. So you reset the tappets to get the rocker horizontal, which has effectively given you a longer pushrod. In actual fact the ideal rocker sits aiming upwards slightly in stock trim, its not horizontal.

 

Now when it opens the valve, the cam nose sits in the same spot, but your longer pushrod means the rocker will move down through a greater arc and open the valve more. The worst thing is that it will wipe off the inner top edge of the valve and wear badly. The other thing is that if you consider arcs and tangents, the horizontal pushrod move slowly per degree to start with, then speeds up as it moves further per degree in the middle of its arc, then slows down again towards the end. This is easy on the valve. You lose that geometry by cutting the cam heel out.

 

One solution is to trim the rocker posts lower, the other is to cut a hot cam from a billet, not from a cam already made.

 

This really only applys to pretty hot cams, rather than road/sports grinds.

Edited December 19, 2011 by altezzaclub

[SLO-030]

The Turbo 7K KE25 has adjustable rocker gear and hydro lifters to adjust preload.

[Evan G]

this is why you shave the head when you get a cam.

 

they remove the meat from your cam base circle (lets say 40thou)

 

now your rocker geometry is up the shit house. now you shave the head 40 thou and get some compression up her and retain good geometry

 

:y:

[5ksev]

this is why you shave the head when you get a cam.

 

they remove the meat from your cam base circle (lets say 40thou)

 

now your rocker geometry is up the shit house. now you shave the head 40 thou and get some compression up her and retain good geometry

 

:y:

i think this might actually work.. as iv shaved my head to 10:1 wich is apparently 40thou..

 

i just gotta ask tighe tomorrow when i get my cam, how much have they taken off.. but in theory, it should be almost back to normal?

[Evan G]

if you put a big cam in it and don't shave the head youll need longer push rods. (if there not enough adjustment in the rockers)

 

my machinist explained all of this when i was doing my cam/head work

[5ksev]

yeah well iv gone the 25/65 270dur .423 lift cam, by tighe.. and shaving my head from stock to 10:1 comression.. wich i hope will fix the problem its caused.. but if not, ill just shave my rocker post's a little more

[GJM85]

Shit if where drawing pictures. Here's one I made a while ago!

[GJM85]

i think this might actually work.. as iv shaved my head to 10:1 wich is apparently 40thou..

 

i just gotta ask tighe tomorrow when i get my cam, how much have they taken off.. but in theory, it should be almost back to normal?

 

If I had a vernier I would check the lobe height on the 104 i've got in the garage. Then you could check the lobe height of a stocker and get the difference. You could then take that off the head.

 

I only say that because nobody knows the original specs of a stock camshaft....

Edited December 19, 2011 by GJM85

[Evan G]

should be on the website? lift at lobe?

[GJM85]

should be on the website? lift at lobe?

 

Oh yeah. I'm just really special.... :yes:

 

Ok then someone just needs to get the original cam specs then your set. :wink: But good luck with that.

[5ksev]

thanks for all the help guys.. ill get all the measurments tomorrow and hopefully it works out perfectly :)