Increased Rocker Ratio On A K Motor ?

[Doogs]

Hi,

 

In a few months I plan to build a mild 5k for my car. For a while I have been considering different options for my build, but

had not thought about rockers much.

 

I know of some people who build holden 6s and similar era engines, and one of the mods they do is to install roller-rockers and up the rocker ratio.

This aims to have the valve accelerating off the valve seat faster, and to produce reasonable power without having to run huge lift in a street

car engine (that would result in rapid wear and lack of driveability).

 

Has anyone tried/considered altering the rocker setup in a k motor, and are there any of these parts around for such a small engine?

[adke11]

Hi,

 

In a few months I plan to build a mild 5k for my car. For a while I have been considering different options for my build, but

had not thought about rockers much.

 

I know of some people who build holden 6s and similar era engines, and one of the mods they do is to install roller-rockers and up the rocker ratio.

This aims to have the valve accelerating off the valve seat faster, and to produce reasonable power without having to run huge lift in a street

car engine (that would result in rapid wear and lack of driveability).

 

Has anyone tried/considered altering the rocker setup in a k motor, and are there any of these parts around for such a small engine?

 

 

ay brother in Australia who built a site for Datsun A12-A15 when you get the information sent. I am also looking for ways to build

[Doogs]

Anyone considered it or heard of it being done ?

[Felix]

Considering you are building a "mild" 5k motor, why bother?

 

Roller rockers are more a top end mod, so unless you plan on spending extended periods of time over 8 grand, I don't really think the cost/performance factor is very favourable. From what I've seen you are looking at $600-1000+ for roller rockers to suit a Datsun A series motor. Then you have to modify them to suit your 5k, also you'll be needing a solid lifter conversion....

 

Seems like an awful lot of money to spend on a mild build of a 5k motor.

[philbey]

Yeh, the roller rocker thing is really aiming at the high end market where you need to try get that .5% power increase to get that competitive edge.

 

I wouldn't worry about it with the milleaux of other useful, significant and cheaper mods available out there. A Cam grind will give you the things you desire, like faster valve acceleration and greater lift anyway, and that will cost you 100 bucks!

[adke11]

Anyone considered it or heard of it being done ?

 

 

 

this is the place that produced the research for Datsun

 

Yella Terra Race Rocker Systems :yes:

[camerondownunder88]

I once saw a K motor with Mini roller rockers. BUT mini run a 1.2 ratio so look into it but they can be grafted onto the motor.

 

I briefly saw this car at a gathering in my town once he had spent a lot on it and for me I wouldn't bother with roller rockers. Even the TRD 3K/4K doesn't have roller rockers.

 

Cameron

[Doogs]

Thanks for the replies.

 

I didn't realy have roller rockers in mind (due to the cost amoung other things), and yes also thought it would be overkill for this motor and its

application.

I was instead musing about whether you could easliy change the ratio and still run a flat tappet cam. Sorry, I probably should have specified that.

I am aiming to build a mild motor, but a well thought out one (hence the questions).

 

Thanks again,

 

Dougal

[orangeLJ]

In terms of holden sixes (as an example) without going to roller rockers there are a few options, main one is 1.65 ratio from falcons.

 

Or you can bolt on 308 rockers (1.6 aswell)

 

standard is 1.5

 

 

So if you can find a set of rockers that will bolt in and not upset the angle of operation, then Id go for it.

 

Only thing to check is spring bind when fully compressed.

[snot35]

You're going to have to check a whole bunch of things to make sure it works properly, wipe pattern, spring binding etc. Why reinvent the wheel when you could just get a cam ground?

 

For such a small engine, the higher ramp speed may only make a barely noticeable difference. I'd go for a basic port job first, there is quite a few areas in there that need obvious tidying up. That will help a whole lot with mid range as well as high end without pushing the valves out further.

[Doogs]

Thanks orangeLJ,

Thats more along the lines of what I was thinking.

 

You're going to have to check a whole bunch of things to make sure it works properly, wipe pattern, spring binding etc. Why reinvent the wheel when you could just get a cam ground?

 

For such a small engine, the higher ramp speed may only make a barely noticeable difference. I'd go for a basic port job first, there is quite a few areas in there that need obvious tidying up. That will help a whole lot with mid range as well as high end without pushing the valves out further.

 

snot35, I am planning on doing a port job and cam as well as maybe bigger valves.

 

I wanted to see if this could be done, and if parts were easily available. Being a k motor I assumed they were'nt, but I thought I may as well check.

[tojo2]

I once saw a K motor with Mini roller rockers. BUT mini run a 1.2 ratio so look into it but they can be grafted onto the motor.

 

I briefly saw this car at a gathering in my town once he had spent a lot on it and for me I wouldn't bother with roller rockers. Even the TRD 3K/4K doesn't have roller rockers.

 

Cameron

 

 

Have heard of minis using K rockers for a budget hi lift mod.

Those 1.7-1 roller tipped rockers could be worth it if they fit... anyone ever looked into this?

 

 

:yes: forgot the link.. http://www.minisport.com/acatalog/Mini_Rol...ip_Rockers.html

Edited June 15, 2009 by tojo2

[Felix]

Why reinvent the wheel when you could just get a cam ground?

 

Exactly. You could get a cam reground to max out the available valve lift just short of coil bind. Cost $100-150.

[Doogs]

Exactly. You could get a cam reground to max out the available valve lift just short of coil bind. Cost $100-150.

 

Ok, point heard.

I thought I may as well have a look at what else I could do to make this build as good as I can.

[Felix]

Invest in some books by David Vizard and Graham Bell. :yes:

 

Those guys will set you in the right direction to get the best bang for your buck. :hmm: It amazes me how easily and cheaply you can get a K motor to go with a well balanced package.

Edited June 15, 2009 by Felix