10 replies to this topic

[steble]

Hi all,

Spent a couple of days searching the interweb trying to answer this but not really found a definitive answer/decent opinions.

I have some brand new 1.7:1 titan rockers, (I wanted 1.5 but these were a complete steal)

I am about to throw a different engine I have in the garage together and was going to change the cam while I was at it.

But is this a good idea when running 1.7 rockers.

I was thinking of a fast road cam like a md276 or bp270. But would this coupled with 1.7 rockers be too much?

Maybe a mild road cam instead, say a md256 or bp255 or ca2?

Or just leave what is in there, it is an spi Cooper engine, don't know what cam they run :s

Very interested in people's opinions on this, as nerdy as they may be :)

Many thanks
Steve

[nicklouse]

i would sell them on.

[steble]

i would sell them on.

Please elaborate

[dyshipfakta]

Minimal gains at the top for a loss in low end torque. I would sooner have the torque. Unless it's a racer I guess. My mini mainly does shopping and bnq runs

[Rorf]

Didn't think 1.7 rollers were available

[Northernpower]

Didn't think 1.7 rollers were available

https://www.minispor...er-rockers.html

[nicklouse]

 

Didn't think 1.7 rollers were available

https://www.minispor...er-rockers.html

 

love the way they do not mention the increased wear on the cam.

 

some reading for you if you don't move them on.

http://www.calverst....ral-compendium/

[Northernpower]

 

 

Didn't think 1.7 rollers were available

https://www.minispor...er-rockers.html

 

love the way they do not mention the increased wear on the cam.

 

some reading for you if you don't move them on.

http://www.calverst....ral-compendium/

 

I can't see the point in them. The money no matter how cheap would be better invested in a quality cam design.

[Dusky]

I've seen 1.7 rockers used once.
On a 300 OR 310° scatter cam with split webers, hillclimb car. It went very well, but couldnt take off under 3k rpm.

[carbon]

Steve,

 

Your 1.7 roller rockers should work well for a fast road 1275 with the Kent MD266 cam. I'm running the MD266 cam with a set of what are meant to be 1.5 ratio rockers, but based on the 10.5mm lift at the valve it is nearer 1.65 ratio in real life. Head is a 12G940 with 35.6mm inlets, mildly flowed, and about 9.75:1 compression (with twin HS2 and twin box RC40).

 

This MD266 with 10.5mm valve lift combination gives reasonable tickover, well behaved about town, but also gives much better torque above 3000 rpm than the previous rocker set-up, which gave 8.0mm valve lift with the same MD266 cam. No idea what power, has never been on RR.

 

I cannot comment about increased cam lobe wear,as it's not a daily driver and only doing a few thousand miles a year. Likely to be a while before the cam wear becomes an issue (I hope). The one point to watch is breaking the cam in gently - it might be better done with standard rockers, and then change to the 1.7 roller rockers after a 1000 miles or so.

 

Ignition timing advance curve will also need to be tweaked, I found this needs to be very different to standard rockers with more static advance (about 13 deg) and also the advance to come in much quicker (33 deg by 3000rpm) using Shell V-Power 99 octane fuel.

 

For road use I would suggest only using the 1.7 ratio rockers with a cam that has less than 265 thou lift at the lobe. Anything more and I think you will struggle to get enough clearance for fitting valve stem seals. You can leave them off, but if you do then be prepared for a smoky engine and high oil consumption.

[steble]

Steve,
 
Your 1.7 roller rockers should work well for a fast road 1275 with the Kent MD266 cam. I'm running the MD266 cam with a set of what are meant to be 1.5 ratio rockers, but based on the 10.5mm lift at the valve it is nearer 1.65 ratio in real life. Head is a 12G940 with 35.6mm inlets, mildly flowed, and about 9.75:1 compression (with twin HS2 and twin box RC40).
 
This MD266 with 10.5mm valve lift combination gives reasonable tickover, well behaved about town, but also gives much better torque above 3000 rpm than the previous rocker set-up, which gave 8.0mm valve lift with the same MD266 cam. No idea what power, has never been on RR.
 
I cannot comment about increased cam lobe wear,as it's not a daily driver and only doing a few thousand miles a year. Likely to be a while before the cam wear becomes an issue (I hope). The one point to watch is breaking the cam in gently - it might be better done with standard rockers, and then change to the 1.7 roller rockers after a 1000 miles or so.
 
Ignition timing advance curve will also need to be tweaked, I found this needs to be very different to standard rockers with more static advance (about 13 deg) and also the advance to come in much quicker (33 deg by 3000rpm) using Shell V-Power 99 octane fuel.
 
For road use I would suggest only using the 1.7 ratio rockers with a cam that has less than 265 thou lift at the lobe. Anything more and I think you will struggle to get enough clearance for fitting valve stem seals. You can leave them off, but if you do then be prepared for a smoky engine and high oil consumption.

Thanks carbon, this is the sort of information ℹ was looking for. Thank you.
266 was very much where I was thinking on this, the car will be used on the road. But at the same time is very much a toy and like yourself I do not do many miles in it. It will see the track a bit, and maybe once I have the new cage and chassis sorted It will see some sprint events :)