Ability to rev reduced after installing roller rockers

[adamnreeves]

Hi
They could well be SBC rockers "repurposed" for the rover engine, in which case they very well could be 1.5-1.55:1 ratio.
Best regards
Mike

Noooo, I don't want to be hearing that!

Yes I can adjust the push rod or rocker. I adjusted the rockers tonight. The thread pitch means one turn = 40 thou so one complete turn anti-clockwise is what I have done which makes it 20 thou. No time to go for a drive though. I shall report back tomorrow.

[kiwicar]

Hi
If you want to get a bit more lift out of them you can always put lash caps on top of the valve and run the adjusters further into the rockers, you will gan a little (2 or 3%) but be careful you can introduce too much side load on the cups of the adjusters and they shatter. I can let you have 16 rockers that have failed because of doing this in error!
If they are plane bearings on the shaft you can off set bush them and again gain a bit on the rocker ratio.
Best regards
Mike

[r2d2hp]

Hi Mike, you can let me have the failed ones to experiment with

[kiwicar]

Hi Reg
You are most welcome to them, take them away with you when you are next over, or I can take them along to the retro show.
Best regards
Mike

[adamnreeves]

Went out tonight to try after the adjusting preload to 20thou.
Cannot find my SD card for the data logging but the tacho is confirming I can only reach 5,700RPM now. A little upset to say the least. Spent hundreds of pounds on this conversion. I am seriously thinking of putting it back to standard.

[stevieturbo]

So I have installed my roller rockers and increased my RPM limit from 6000 to 6500. However I am a little disappointed.

Previously on the standard rockers I could accelerate right up the 6000 without any sign of let up. Now I accelerate and power seems to be down and starts backing off around 5600 and by 6000 power drops right off so much that I cannot hit my red shift light which I could do before!

Valve lash set at 60thou as per the insructions for rhoads. I know oem ones are more like 30thou.

I suspect pump up but I thought I'd initially try the setting I had before, i.e. keep everything else the same. I could try and reduce lash down to 40 thou maybe.

Also the engine does sound a little more grunty at mid range, where it feels slightly down on power.

My son drove the car back and he is as familar with the car as me and he made the same observations.

Rover 4.6V X-bolted
Piper 285i high lift cam, power upto 6500
Rhoads lifters
Cat when last dyno'd before made 291 BHP at 5,800 and 305 lbft.

I didnt take any data logs and may do this next week.

So exactly what valve springs do you have, and are they installed correctly ?

[adamnreeves]

Valve springs have 75lbs seat pressure and 200lbs at a lift of 12.7mm. They were sourced from real steel.

The springs have been in there since September 2009 and I have done a total of 6000 miles about 2000 miles on track, 4000 on road.

Picture from my build diary:

[stevieturbo]

And is that sufficient for the cam/lifter combo you are using ?

Are they just singles ?

[adamnreeves]

And is that sufficient for the cam/lifter combo you are using ?

Are they just singles ?

They are singles. I just checked the pipercam site and they recommend VSSV8 springs which say 246rate. I presume this means 246lbs at full lift.

[sidecar]

And is that sufficient for the cam/lifter combo you are using ?

Are they just singles ?

The thing is that this engine revved to 6k and more with the standard rockers, they were then changed for a set of rollers rockers and now it won't rev.

I considered buying the same set at Stoneleigh, glad that I gave them a miss now!

If it was my lump I'd put the standard rockers on just to confirm that the roller rockers are causing the issue.

Also with the rollers off the engine you could check out the ratio with the use of a DTI and a bit of fiddling about.

[stevieturbo]

I understand the problem. The springs may just have been borderline before, but now with different rockers have been pushed too far.

One change can have a knock on effect to other parts.

At the minute, it might do no harm to put the old rockers back on as they were and decide where you want to go from there. You could try with different pre-loads again, but Im not convinced it makes that much difference.

[adamnreeves]

Yes, I think you must be right steve. I think it ought to be possible to change springs it situ. Just get each piston in turn at TDC so valves do not drop. Then use an older rocker shaft and use a tool to prise the springs down.

[stevieturbo]

You can make up an air fitting to keep the valves shut during the change. ie pump air in via a compressor.

This does work, but TBH, I think the old tried and tested method of rope inside the chamber is the most foolproof.

It's a bit slower though. But changing springs in situ isnt difficult...just sore on the back.

[adamnreeves]

Rope method I had heard of actually. Even worse on the back in a Westfield the engine is even lower. Thanks for your help.

[adamnreeves]

And is that sufficient for the cam/lifter combo you are using ?

Are they just singles ?

The thing is that this engine revved to 6k and more with the standard rockers, they were then changed for a set of rollers rockers and now it won't rev.

I considered buying the same set at Stoneleigh, glad that I gave them a miss now!

If it was my lump I'd put the standard rockers on just to confirm that the roller rockers are causing the issue.

Also with the rollers off the engine you could check out the ratio with the use of a DTI and a bit of fiddling about.

I am convincing myself to change the springs. In too far to revert I think. Good idea with DTI. I will do this.