Discussion
Demon Tweeks in Wrexham. Look in their on-line catalogue.
When I fitted stub-stacks to the K & N's on my twin H4's on my Cooper 'S' and then did a power run on the rollers, I don't think I gained anything at all. I thought I might get a couplke of bhp or even a bit more mid-range, but I can honestly say they didn't seem to make much difference. Perhaps ram pipes, which is what stub stacks are a shortened version of, only work when they are several inches long.
It was the same with the 1.5 roller rockers, which only gave an extra couple of bhp at above about 5500 rpm. I've left them on as the roller tips do reduce valve guide wear.
When I fitted stub-stacks to the K & N's on my twin H4's on my Cooper 'S' and then did a power run on the rollers, I don't think I gained anything at all. I thought I might get a couplke of bhp or even a bit more mid-range, but I can honestly say they didn't seem to make much difference. Perhaps ram pipes, which is what stub stacks are a shortened version of, only work when they are several inches long.
It was the same with the 1.5 roller rockers, which only gave an extra couple of bhp at above about 5500 rpm. I've left them on as the roller tips do reduce valve guide wear.
Interesting! One of the things mentioned in the book is that the distance between the carb mouth and the lid/opposing face of the filter should be greater than or equal to the size of the carb. I wonder if I was to change the filter for something a bit deeper while fitting the stub stack would that see a gain? I need to read over that chapter again I think.
Have you had experiences with the torque ram mentioned in the Vizard book? It has a plenum and a 17" pipe with a big round filter on the end. I wonder if it's worth going for one of these as I do plan to upgrade the head and cam in the future.
With regards to 1.5 rockers, I've read they increase cam wear by a fair degree! I also know someone who suffered a 10bhp loss when removing the rollers for standard ratio ones.
Have you had experiences with the torque ram mentioned in the Vizard book? It has a plenum and a 17" pipe with a big round filter on the end. I wonder if it's worth going for one of these as I do plan to upgrade the head and cam in the future.
With regards to 1.5 rockers, I've read they increase cam wear by a fair degree! I also know someone who suffered a 10bhp loss when removing the rollers for standard ratio ones.
That's really for competition use and not for the road. Is your car to be used in serious competition?
Higher ratio rockers will increase the wear on the rocker shaft and the wear on the cam and followers. For a competition engine this is not a problem as the complete engine is stripped often and the followers changed and the cam inspected closely. In fact, roller-tip rockers do reduce wear on the valve guides as they eliminate side loads on the valve stems.
I really can't believe that removing high-lift rockers and replacing with 1.3:1 standard ones would lost 10 bhp - 2 bhp is more likely and that would be at over 6000 rpm.
You do lose some botton end with higher lift rockers as well. They really are a competition extra.
Higher ratio rockers will increase the wear on the rocker shaft and the wear on the cam and followers. For a competition engine this is not a problem as the complete engine is stripped often and the followers changed and the cam inspected closely. In fact, roller-tip rockers do reduce wear on the valve guides as they eliminate side loads on the valve stems.
I really can't believe that removing high-lift rockers and replacing with 1.3:1 standard ones would lost 10 bhp - 2 bhp is more likely and that would be at over 6000 rpm.
You do lose some botton end with higher lift rockers as well. They really are a competition extra.
Hi, I got mine from Keith Calver:
http://www.calverst.com/shopopen.htm
He does a fully round one and also a flat bottomed one (ask when ordering)
Dont know if they make a massive difference as I fitted mine at the same time as the carb (went from twin 1.25" to HIF44)
Also available on Ebay from seperate sellers:
http://tinyurl.com/yd2wgq6
http://tinyurl.com/m3dc6r
Mark
http://www.calverst.com/shopopen.htm
He does a fully round one and also a flat bottomed one (ask when ordering)
Dont know if they make a massive difference as I fitted mine at the same time as the carb (went from twin 1.25" to HIF44)
Also available on Ebay from seperate sellers:
http://tinyurl.com/yd2wgq6
http://tinyurl.com/m3dc6r
Mark
Edited by MGwob on Friday 25th September 22:43
1.5 roller rockers gained me 3hp between 5500 and 6000rpm when I fitted them to my 1330 (rolling road at Aldon), but they also raised the start of the power band from about 2200 to 2700rpm.
I can't tell the difference between having my stub stack fitted or removed, but I do leave it on anyway. It's one of the rough looking aluminium castings, which I am going to change for the item that m.e.d advertise at some point to see if there's any improvement as it seems to be a far better design.
e.t.a the m.e.d one looks identical to Keith Calvers
I can't tell the difference between having my stub stack fitted or removed, but I do leave it on anyway. It's one of the rough looking aluminium castings, which I am going to change for the item that m.e.d advertise at some point to see if there's any improvement as it seems to be a far better design.
e.t.a the m.e.d one looks identical to Keith Calvers
Edited by JimexPL on Saturday 26th September 10:54
JimexPL said:
1.5 roller rockers gained me 3hp between 5500 and 6000rpm when I fitted them to my 1330 (rolling road at Aldon), but they also raised the start of the power band from about 2200 to 2700rpm.
I can't tell the difference between having my stub stack fitted or removed, but I do leave it on anyway. It's one of the rough looking aluminium castings, which I am going to change for the item that m.e.d advertise at some point to see if there's any improvement as it seems to be a far better design.
e.t.a the m.e.d one looks identical to Keith Calvers
It might depend on which cam you have. With softer cams the improvement may be more than with a longer duration/higher lift one. Mine has a 286 and relatively big inlet valves and my gain was 2 bhp at over 5500. I still have thenm fitted, but they don't seem to increase the overall performance and it's definately more lump low down. But then, my engine won't really pull below about 3200 anywayI can't tell the difference between having my stub stack fitted or removed, but I do leave it on anyway. It's one of the rough looking aluminium castings, which I am going to change for the item that m.e.d advertise at some point to see if there's any improvement as it seems to be a far better design.
e.t.a the m.e.d one looks identical to Keith Calvers
Edited by JimexPL on Saturday 26th September 10:54
Cooperman said:
It might depend on which cam you have. With softer cams the improvement may be more than with a longer duration/higher lift one. Mine has a 286 and relatively big inlet valves and my gain was 2 bhp at over 5500. I still have thenm fitted, but they don't seem to increase the overall performance and it's definately more lump low down. But then, my engine won't really pull below about 3200 anyway
276. And it is lumpy below 2500rpm (adds to the character...)I keep being drawn towards superchargers at the moment, but will try and keep the money in the bank to go towards my Corvette fund!
I've always thought that superchargers are better than turbo-chargers. The problem with superchargers used to be belt slippage when the belts got wet, but now that toothed belts are easily available that problem has gone away. With turbo-chargers you do have a high temperature issue and if any of the parts are a bit 'iffy' failure seems to occur quite quickly.
The Supermarine Spitfire and the P51 Mustang both had a supercharger on their Merlin engine.
The Supermarine Spitfire and the P51 Mustang both had a supercharger on their Merlin engine.
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