10 replies to this topic

[redmini]

:wales: I'm lookinig at getting some roller tip rockers for my 1293, what is the best ratio to get. I'm torn between 1.3 and 1.5's, any suggestions?

[Bungle]

depends on how much lift is in your cam :smartass:

[DaveCoxon]

maybe go for 1.4? Somewhere in betwen?

LOL!

[redmini]

:wales: Anybody got a sensible answer? As far as I can remember (without digging out the spec sheet) I've got a phase 2 cam in it, is that enough lift or would I benefit from a little bit more? I'm also thinking of building a non turbo 1293 as I've got some +20 pistons, if it didn't work on the turbo I could just transfer them.

[Turbo Nick]

avonbar recommend the 1.3's with the phase 2 cam

[The Matt]

I guess it depends largely on a combination of two things

1. How much lift does your cam give you

2. How far do the valves in your particular head have to be open to achieve maximum flow

The second is as important as the first, there is no point opening the valves up further than they need to be opened to achieve maximum flow.

I have read on here that better BHP was achieved with 1.3s than with 1.5s on a turbo, but again, that depends on head and cam spec.

personally, I reckon the 1.3:1s don't really offer that much gain (other than less side load/wear on the valves). Maybe Avonbar or someone would be the best people to speak to?

[redmini]

:wales: Yes you're probably right, Jonspeed built the engine so for the cost of a phone call......

[The Matt]

Yeah, sorry I can't be of more use. I have looked into roller rocker specs. and valve lift etc. But I don't know enough about turbos to be honest!

[redmini]

:wales: I know what you mean, I've done quite a bit with n/a motors but turbo quite new to me at the mo. Thanks for your help anyway :wink:

[The Matt]

no probs! :wink:

[redmini]

:wales: ok after looking through my build spec I see I've got a 600 cam, doesn't say who it was made by or anything so limited info on that one. Tried phoning Jonspeed a few times now but it's either engaged or rings out, anyone got any idea what a 600 cam is then?