29 replies to this topic

[Orange-Phantom]

 

 

 

 

Also interested since swift tune say over 1.4 is pointless 

Can you show me the documentation where Swiftune state over 1.4 is pointless?  Probably not as...

 

Swiftune recommend 1.5 ratio rockers for a lot of their cams for instance the SW10 which I run with 1.5 rockers and that is after I spoke with Nick Swift himself!

 

If you click on the link below and on the SW5, SW8, SW10 cams they all state that the example engines with the corresponding dyno graphs are using 1.5 ratio rockers!

 

https://swiftune.com.../camshafts.html

 

 

https://swiftune.com...r-assembly.html

 

 

"Years of dyno and track research, testing and development have established that for current camshaft profiles and cylinder head designs, there is no need to increase the rocker ratio beyond 1.4.

"

 

If you look, they also only see 1.4 ratio rockers. 

 

Fair enough.  I'm just going on what Nick Swift told me to run which was 1.5 ratio rockers with the SW10 Cam.  They also only sell non roller rockers, due to the historic racing regs.

Still curious as to why they would then use 1.5 rockers for their test engines that produced the cam graphs for their SW5, SW8 & SW10 cams and as documented on their website?

 

 

I did chuckle inside when you said i couldnt prove it, I was suprised when i read it too ( 1.4 being best). I noticed since im buying a SW5 and wanted to see recommended setups. 

 

Yes your response did also surprise me.   I  wasn't trying to be funny with you (it's never easy to get that across when typing) it just went against what Nick told me and what their website also shows on their cam pages so yeah, bit of an odd one!

I've got my own suspicions which is that they have made a product and thus want to sell it despite the contradictions on their cam pages.

Personally I think the difference between 1.4 and 1.5 would be marginal especially with the SW5 (which is a great cam by the way).  Personally I'd prefer a nice set of roller rockers myself and a good cylinder head too!  Pick which you want i.e. a tad more low down power (1.4 ratio) or a little less low down grunt and a bit more top end (1.5) bearing in mind the SW5 is a fairly tame cam.

Edited by Orange-Phantom, 10 July 2019 - 10:15 PM.

[hhhh]

Higher ratio rockers allow the cam grinder greater choice in lift acceleration without necessarily increasing maximum lift, but if you use 1.5s on a cam intended for 1.3s, it's going to gain high RPM torque at the expense of low. But it is a quick and dirty "hot cam" bolt-on solution.

[DeadSquare]

 

 

Also interested since swift tune say over 1.4 is pointless 

Can you show me the documentation where Swiftune state over 1.4 is pointless?  Probably not as...

 

Swiftune recommend 1.5 ratio rockers for a lot of their cams for instance the SW10 which I run with 1.5 rockers and that is after I spoke with Nick Swift himself!

 

If you click on the link below and on the SW5, SW8, SW10 cams they all state that the example engines with the corresponding dyno graphs are using 1.5 ratio rockers!

 

https://swiftune.com.../camshafts.html

 

 

There's little point opening the Valve beyond what the Port will flow.

 

 

Just fitting high lift rockers on an already supercharged, but otherwise standard 997, made a nice improvement in torque.

[luismx123]

just as we are on the topic of rockers, does it makes sense to get one for a 998? planning on going the evo001 or sw5 route in the future with a calverst head and a possible overbore/crankshaft swap to a 1098. would it make sense getting rockers in the mix too?

[cooperd70]

just as we are on the topic of rockers, does it makes sense to get one for a 998? planning on going the evo001 or sw5 route in the future with a calverst head and a possible overbore/crankshaft swap to a 1098. would it make sense getting rockers in the mix too?

It's recommended you keep the standard rockers on a 998 if going with the sw5

[DeadSquare]

just as we are on the topic of rockers, does it makes sense to get one for a 998? planning on going the evo001 or sw5 route in the future with a calverst head and a possible overbore/crankshaft swap to a 1098. would it make sense getting rockers in the mix too?

 

I believe that Mr. A.C, Dodd has had experience of pepping up 1098 engines, and I hope that he won't mind me suggesting to you that you talk to him about your proposed engine.

 

A 1098 engine's long stroke, with a matching cam, and a head and carb that breathe well, produces torque that is sweet to drive, but it needs to be a Pavlova, not a mouthful of pic-n-mix.

Edited by DeadSquare, 11 July 2019 - 08:39 AM.

[luismx123]

 

just as we are on the topic of rockers, does it makes sense to get one for a 998? planning on going the evo001 or sw5 route in the future with a calverst head and a possible overbore/crankshaft swap to a 1098. would it make sense getting rockers in the mix too?

 

I believe that Mr. A.C, Dodd has had experience of pepping up 1098 engines, and I hope that he won't mind me suggesting to you that you talk to him about your proposed engine.

 

A 1098 engine's long stroke, with a matching cam, and a head and carb that breathe well, produces torque that is sweet to drive, but it needs to be a Pavlova, not a mouthful of pic-n-mix.

 

oh yea definitely. Im planning on contacting either him/crafted classics or calver himself to get a good bundle of parts. Im aware that a 1098 rebuild isnt the same as a standard upgrade on a 998 or 1275. 
I just feel bad asking someone for advice, then not following through/moving onto someone else so once my plan is set id contact and follow through with the correct person.

[Bobbins]

 

 

 

 

 

Also interested since swift tune say over 1.4 is pointless 

Can you show me the documentation where Swiftune state over 1.4 is pointless?  Probably not as...

 

Swiftune recommend 1.5 ratio rockers for a lot of their cams for instance the SW10 which I run with 1.5 rockers and that is after I spoke with Nick Swift himself!

 

If you click on the link below and on the SW5, SW8, SW10 cams they all state that the example engines with the corresponding dyno graphs are using 1.5 ratio rockers!

 

https://swiftune.com.../camshafts.html

 

 

https://swiftune.com...r-assembly.html

 

 

"Years of dyno and track research, testing and development have established that for current camshaft profiles and cylinder head designs, there is no need to increase the rocker ratio beyond 1.4.

"

 

If you look, they also only see 1.4 ratio rockers. 

 

Fair enough.  I'm just going on what Nick Swift told me to run which was 1.5 ratio rockers with the SW10 Cam.  They also only sell non roller rockers, due to the historic racing regs.

Still curious as to why they would then use 1.5 rockers for their test engines that produced the cam graphs for their SW5, SW8 & SW10 cams and as documented on their website?

 

 

I did chuckle inside when you said i couldnt prove it, I was suprised when i read it too ( 1.4 being best). I noticed since im buying a SW5 and wanted to see recommended setups. 

 

Yes your response did also surprise me.   I  wasn't trying to be funny with you (it's never easy to get that across when typing) it just went against what Nick told me and what their website also shows on their cam pages so yeah, bit of an odd one!

I've got my own suspicions which is that they have made a product and thus want to sell it despite the contradictions on their cam pages.

Personally I think the difference between 1.4 and 1.5 would be marginal especially with the SW5 (which is a great cam by the way).  Personally I'd prefer a nice set of roller rockers myself and a good cylinder head too!  Pick which you want i.e. a tad more low down power (1.4 ratio) or a little less low down grunt and a bit more top end (1.5) bearing in mind the SW5 is a fairly tame cam.

 

 

Wow didn't quite expect so many responses to my post!

 

Am I correct in thinking from what's been said that for ultimate power the 1.5 is obviously going to work best but this will push power and torque further up the rev range which isn't necessarily desirable. Keeping to a 1.4 or 1.3, the available torque will come in lower down ... good for a road car but less power. I notice Swift don't appear to do a roller version of the 1.4, rollers must be preferable to reduce rocker and valve guide wear ... therefore for what reason would someone invest in 1.3 roller rockers other than reduced wear?

[ACDodd]

I had been fitting roller tipped 1.3 rockers to my road engines for years. The problem was that of wear on high mileages experienced by road cars. The rollers would wear out, or the pin holding the roller would fall out or break depending on the type used. That's why I decided to make my own using a non roller type design.
I find that the biggest area under the torque curve between 2 and 5krpm, consistent with the least load in the cam and followrs is given by 1.3:1 ratio rockers.

Ac

Edited by ACDodd, 11 July 2019 - 11:17 AM.

[Wiggy]

From personal experience my MPi with the JCW gear (including 1.5:1 rockers) was gutless until 3k. Then it went pretty well.

Adding a Kent 274i with said rockers made a massive difference to the drivability.

Changing the final drive helped a bit, but the new cam really pepped her up.

[hhhh]

...I find that the biggest area under the torque curve between 2 and 5krpm, consistent with the least load in the cam and followrs is given by 1.3:1 ratio rockers.

Ac

I agree with Vizard on his claim that the springs can be de-rated to completely counter what would otherwise be the increased load on the follower side of the valve train. E.g., if the ratio is increased to give 25% greater lift, the spring force at full open can be reduced by 20% with the same peak RPM possible before valve float begins.

[Bobbins]

...I find that the biggest area under the torque curve between 2 and 5krpm, consistent with the least load in the cam and followrs is given by 1.3:1 ratio rockers.

Ac

I agree with Vizard on his claim that the springs can be de-rated to completely counter what would otherwise be the increased load on the follower side of the valve train. E.g., if the ratio is increased to give 25% greater lift, the spring force at full open can be reduced by 20% with the same peak RPM possible before valve float begins.

I haven't read Vizard's comments that you refer to, but don't you mean that the spring rate can be reduced by 20% which will give the same force at full open if lift is increased by 25%?

[hhhh]

Spring rate brings a complication into the calculation because maximum spring compression changes with rocker ratio. If you consider spring force at full open, it's more direct. Spring rate would also affect the seat pressure when closed which is not a concern here. The two parameters can be adjusted almost independently with beehive springs for example.

Edited by hhhh, 12 July 2019 - 01:12 PM.

[carbon]

Interesting point about spring rates and valve lift.

 

So if I have a set-up with 1.25 ratio rockers and valve crash speed of 6,500rpm and I then fit 1.65 ratio rockers with no change to the springs, what is the expected new valve crash speed?

[hhhh]

No idea, LOL, but likely higher. The follower side of the valve train "sees" a stiffer spring.