E30 Zone

Hi everyone,

Just getting my head around building a 2.8 M20 and looking at revving it quite a bit (a 7500 limit) with a 288 cam. Heard all sorts of horror stories about rockers breaking so wondering what to do about such things - Any recommendations? I have seen Ireland Engineering stuff, but not too happy about paying import duty... Any places where I can source all my uprated M20 parts from - A Tech for example??

Any ideas / suggestions welcome!

Cheers for now,
Mikey_Boy

Newman cams for rockers if they have any left

Jason

7500 limit will be well past peak HP dude, unless you go mega Compression and bump the cam spec up a bit.

By Mega I mean static CR of around 13:1 minimum.

Over rev is one thing for corners( ie hang on rather than unbalance and shift up ) but a higher limit is just that, don't let that "goal" drive the build sheet !

Thanks Ant - always helpful! Was aiming to get peak power around 6800, so hang onto the gear until about 7200 to drop the next gear nicely into the power band and have a few hundred rpm spare in case of having to hang on to a gear as you say, over enthusiasm on my part or operator error...!

As I remember from an email chat we had, we were talking about 12:1 static compression on a 288 cam? I think 288 is my limit seeing as the car needs to pass an MOT...?

What would you recommend with respect to rockers?? Just high revs isn't the only goal at all - just want to get the old girl as reliable as possible...!

Full set of steel rockers from Newman is £185, which I think is cheaper than the dealer isn't it?!

Don't get eccentrics or bolts for that though.

I bought a set in april last year and they were running out then apparently though.

what about roller rockers? i used a set of them in my old 2.1 pinto mk2 escort & they stood up to any/all abuse i could dish out.

does anybody know if they are available for the m2b25/27?

Don't think any are available for the M20 as adjusting the valve clearances makes the design fairly complex.

It's not friction that kills the M20 rockers, it's the fact that they operate in a high stress cyclical stress environment, and being aluminium means their failure is a given.

Looks like I got the last set of rockers from Newman cams...

Maybe scope for a group buy if needed in future by enough people??

Will keep you posted on the build when I get around to it! A 262CR gearbox to install first...

Thanks e21Jason for the top tip!

Cheers,
Mikey_Boy

When you get them, inspect them carefully for the brazed on pads being square.

Have a vague feeling someone had one which wasn't.

is there a place for a run of roller rockers with ball end threaded adjusters?

There's not room to get a roller on the cam (the diameter of the roller would be massive, or you'd need specially profiled cams to compensate for a smaller roller that end.

Usually, roller rockers have the rolling bit pressing on the valves to reduce side loading on the valve stem.

However, with the M20 rockers, the valve adjustment is done that end with the little eccentric.

To to make the M20 rockers a roller type, you'd need to have the normal arrangement for the cam end, some kind of adjustment in the middle, and the roller tip for the valve end. Have looked into it, and it's a pain to implement!

Thanks for all the top tips guys! Much appreciated...

Just for reference - in my experience roller rockers aren't always the holy grail. In NASCAR and F1, opinion was (is?) divided on what type of finger followers to use, with roller rockers being seen as a complex solution for all the reasons listed above and more...

Now if we could get hold of DLC (Diamond Like Coating) on the rockers, cam bearings and rocker shafts, then that would be something!

Cheers for now,
Mikey_Boy

go onto ireland engineering, e30 goldmine, under performance parts they sell bothe heavy duty cast rockers and billet roller rockers too

IE don't sell roller rockers, and if you have a quick search on E30Tech, you'll see how long their billet rockers last