Roller rocker conversion

[Mikol]

Evening chaps,

Just crossed my mind today, if it would be possible to convert an engine with solid lifters to a roller rocker set-up.

To be specific, a large-journal Rallye head to the later VTR rockers. Obviously I wouldn't be able to use the VTR cam.

I'm sure the rockers would bolt on but am I missing anything in regards to difference in valve lift (if the roller rockers have a difference cam:valve lift ratio) or even if they are spaced differently in the silvertop heads (I've never cracked one open and had a look).

Thoughts and experience appreciated.

[blackie_2k5]

Don't think it's possible

Why would you want to convert to roller rocker may I ask?

[Mikol]

Usual benefits of roller rockers - reducing wear and internal resistance of turning the camshaft

Although a quick search throws up some results of saying the roller rocker assembly is no good past 7000rpm, which is a spanner in the works.

The problem is that the rockers them self fail. This is why you never see high spec cams for the rollers rockers even with uprated valve springs. I guess the only way to see is try if you fancy risking it. You could always see if you can sell the cam you have and get a new one profiled for solid rockers. Or if you have not used the one you have now they can probably just regrind it for solids.

It also seems the cam profile is directly affected by the rocker type. That's spanner #2.

[blackie_2k5]

Yeah mate

Most ppl go for the solid lifters, can be revved harder, and have better profiles available for that head

As well and supposedly being a lot lighter fro what I've read.. By this I can only assume it means rotational weight/mass is lighter

There are ppl who know a lot more about the n/a tuning of TU 8vs so I'll let them explain, I never looked massively into when I seen the cost vs gains

[Mikol]

And there it is dead in the water

http://www.newman-cams.com/pdf/citroen.pdf

Roller ratio is 1.4 for solid lifters and 1.75 for the rollers, so the solid cam profile will dump the valves almost all the way into the sump :D

Case closed tbh

[AXracing]

As blackie_2k5 corectly said, the norm is for people to upgrade roller rocker engine to solid lifters if there tuning the engine. The roller rockers are rather naff and tend to fall apart. This is why you tend to only see very mild performance cams available for them. You would be taking quite a big step backwards fitting them to a Rallye head.

[tweeqd]

i know lot of people say the roller rockers are shit but mine did over 10k miles with a rev limit of 7250 and 190bhp and have now done 4k with 262 bhp and a limit of 7600
i do have a custom made cat cam and piper valve springs

[dannygti]

Some of the best Honda engines use roller rockers :) in fact the civic type r engine with just uprated valve springs,retainer,keepers can rev to 9.5k all day long.

Sorry for my semi pointless post

[blackie_2k5]

My r dropped a valve with standard valve train on standard rev limit :(

Didn't like being revved haha

Broke the rocker arms the lot :oops:

[AXracing]

Some of the best Honda engines use roller rockers :) in fact the civic type r engine with just uprated valve springs,retainer,keepers can rev to 9.5k all day long.

Sorry for my semi pointless post

However again it is becoming more common practice to convert these engines to solid. But then engines such as the old A series its often to go the other way. It really depends on the application to what works best.

[Mikol]

In general rollers do seem to be the much better option in terms of mechanical sympathy and engine longevity but like you say, if the Saxo ones aren't capable of anything more than they were designed for, then that's that. I suppose you can't expect a budget manufacturer to do anything less.

I'm sure there are some very good, much stronger ones out there, just not for a Saxo.

Thanks for the input :)