21 replies to this topic

[happydude2012]

could well be - ill be replaceing them all the same.

i think on the stage 2 head its 35/29mm for the valves

[ACDodd]

Unlikely it happens alot.

Ac

[imack]

Hi,
I ran a second hand Piper 285 cam for 10 years, sold the engine still turning out 110bhp...
I think you should complain if it's worn out after 4 years. 
I killed 2 engines before I got it right but that cam was in every one, never a spot of bother or signs of wear when inspected.
Cheers 

I also ran a piper 285/2 for years, engine built in the late 80's, it had minispares 1.5 non roller rockers, that cam was still unmarked even after an exhaust valve head fell off and destroyed the engine, head and box.
New engine was built with kents 286 using the same rockers, I wore 3 of those cams out in the same sort of mileage the Piper 285 did. Don't know how the spring weights compared though, the 285 was using an Avonbar st3 head with whatever springs they supplied, the 286 ran a Longman GT15 head with springs supplied.

[Bat]

Hi,

I ran standard rockers and Piper springs and followers the same as what would come in a new kit. If I remember correctly I ran valvoline racing 20/50 oil.

Cheers 

[mikal]

For a given road engine, how much hp gain is there to be had in going from 1:3 to say 1:5 ratio rockers? I'm guessing not a lot? Would it be a noticeable difference i.e. worth the expense? I decided not, and use the standard pressed steel rockers in my engine that were dirt cheap (it came with the sintered rockers that I don't like) and I understand are fairly bullet proof.

(mine is a high spec 1293 cc that has plenty of oomph anyway, especially for what is just a road car)

[happydude2012]

For a given road engine, how much hp gain is there to be had in going from 1:3 to say 1:5 ratio rockers? I'm guessing not a lot? Would it be a noticeable difference i.e. worth the expense? I decided not, and use the standard pressed steel rockers in my engine that were dirt cheap (it came with the sintered rockers that I don't like) and I understand are fairly bullet proof.

(mine is a high spec 1293 cc that has plenty of oomph anyway, especially for what is just a road car)

 

well what ive learned is that youve got to match the rockers to your general set up, so cam and compression ratio play a huge part -   Nick swift says he never builds a performance car without 1:5 rockers, but he only builds performance cars and like AC says, high spec engines arent built to last years.

its whats best for your general engine set up rather than bolting on bits to add bang.

[Ethel]

For a given road engine, how much hp gain is there to be had in going from 1:3 to say 1:5 ratio rockers? I'm guessing not a lot? Would it be a noticeable difference i.e. worth the expense? I decided not, and use the standard pressed steel rockers in my engine that were dirt cheap (it came with the sintered rockers that I don't like) and I understand are fairly bullet proof.

(mine is a high spec 1293 cc that has plenty of oomph anyway, especially for what is just a road car)

 

In  all honesty you can achieve enough with just a cam on a road engine.  1.5's still have advantages you can make use of, but it's a lot of money for the gain if you have usable rockers already.

 

We'd generally like the obstruction of the valve out of the way as quick as possible but, as all these tales of failed valve gear testify, there are mechanical limits, particularly where the cam meets its follower. Bigger rocker ratios  increase the lift at all points so can get the valve usefully open quicker without altering the cam to follower interface as much as grinding a cam more aggressively so the contact area is reduced and moved further off centre.

 

You also get the increased lift without increasing the valve opening period and hence valve overlap, which is particularly useful for a road engine with emissions and mpg to think about. Though the extra lift just off the seats can have a similar effect.

 

In short fancy rockers have most to offer at both ends of the tuning spectrum. On an all out engine they allow you to push things further and they can also be a (less potent) alternative to a cam swap that won't risk an emissions fail as much.