Offset ET28 hole in ET25 for more valve lift

[davidd]

davidd, you mentioned a few posts ago about buying cams "off the shelf " and welding them to a shaft, i've never heard of this, any more info as I am considering building an OHC conversion for some HD barrels/heads I have laying about.
Chris.

Chris,

It was Steve Hamel that put me on to this. I think it was Zipper's that supplied the blanks, but I did not see them for sale separately there, but I know that they grind the old camshafts and press on their lobes, so they do that work. I know Enfield sells the blanks directly for KR's. This might get you started:

http://www.performanceindian.com/CamsPt1.html

http://www.enfieldracing.com/hd_cams_6.html

http://www.macleanfoggcs.com/products/cam-lobes/

http://www.zippersperformance.com/


You may have to email Steve to find out who his sources are. Just email me and I will put you in touch.

David

 

[Chris Launders]

Thanks for that David, I will give it some thought, I had considered using Manx cams as these are fitted seperately on to shafts and have vernier adjustment and I have a friend with a load.
I suppose I could slice an existing cam (say a HD performance cam)up and bore the lobes out for the shaft.
Chris.

 

[hrdsuper90]

For Info. I have a pair of works ET25/1 offset rockers from a Speedway engine, they increased lift to .410" (10%). Used them on the inlets of my race outfit.
Chris

 

[johnmead]

If this is for a racing Vincent.....How far do you think you need to go.? The NASCAR engines you talk of most likely rev to 9500 rpm or more.....Even the all out efforts that the Irving Vincent bikes are built to rev to about 7500 max And they put out about 145 HP from 1300 cc 2 valve engines. All the development work you talk of, perhaps you should talk to the Horner brothers who developed the Irving Vincent. The initial design work that was carried out on the heads that Terry sells was from John Trease....He is an out and out Harley man, and his period 3 59' sportster engine (featherbed frame) racer is in my mind the fastest road racing Harley in the world......It is his knowledge of racing and building high output Harley engines, and this is what went into The Vinton racer I mentioned earlier. Much of this work John told me he would likely never repeat, as it was just too time consuming. The bike was very competitive, although some weight changes would help, but the new generation of Manx's has changed the goal post a bit. The ratio you need to give 0.500" lift at the valve is 1:1.15 This from the 0.433 or 11 mm travel already. The other reason I need to make my own valves is because the inlets are 0.125" larger than standard. You generally need to remember the travel ratio of the rocker as well, this at the valve, which is one third up to two thirds down.....from the center line horizontally through the rocker and at right angles to the valve from the vertical.

NASCAR is more than the high $$$$ race cars you see on TV. They have several levels of "feeder" classes. A couple even limit the intake to a single 2-bbl carb. The local engine shops do work on mostly the feeder class engines, many of which redline at 7500 or less and last a full season of Friday and Saturday night racing.

The Horners are not very outgoing when it comes to details of what they do to to make the Irving-Vincent go. The engine looks like a VIncent, but almost everything is different and does not fit a stock set of cases. I know of one engine here in the US, but I don't think they even sell engines or parts anymore.

I have John Treases's phone number and will be giving him a call.

John Mead

 

[greg brillus]

Hi John, You will find John Trease very easy to talk to, and very helpful. I know he has built Harley engines right up to top fuel, A very clever man, so hopefully you may get some answers from him. I to am building a twin race engine, although not as highly tuned as yours, I to have bought some of Terry's MK 5 cams and radiused followers, he also supplied me with some Gold Star dual valve springs, alloy retainers and modified upper guides to suit. The issue I have is he did not supply any collets, which is a real pain. The alloy retainers will require collets that have the same ID as standard 0.310 but the OD is large and more like a collet to suit 0.372 valve size....meaning the collets are very thick walled. The beehive springs, Titanium retainers and collets you have, are they readily available, and roughly what sort of cost...? As it may be easier for me to try something along the lines of what you have......As I said earlier, I can't get valves made without supplying collets to go with them. Thanks in advance.......Greg.

 

[johnmead]

The ones I use are from R&D Spring Corp in California. They are Gold Star ones and two sets ran @ $200. This is the dealer price as I am a dealer. I had my machinist cut the groove in the valve stem. He used a toolpost grinder and a thin stone. He does this fairly often with automobile race motor valves that come without the keeper groove.

I went with Ti retainers, and keepers with a modern groove as the spring pressure is higher than the stock Vincent.

John Mead

 

[litnman]

John, Have you finished your engine? Would like to hear how it turned out.
I have one of Terry Prince's conversion kits with squish heads, including flywheels. Hope to build a hotrod with it some day.

 

[johnmead]

Not completely together yet. I still have to work out the squish band clearance since I am using one of Terry's 92mm stroker cranks. I found some new compression plates amongst my Vincent parts and will be playing with them and some rosin core solder to check the squish.

I also have an aluminum head bracket that is wider than the stock Vincent one to try to keep the mojnt to the 999S Ducati frame as rigid as possible. I am working on fitting that as well.

John Mead