PW3 Cam timing

Status
Not open for further replies.
Joined
Dec 3, 2010
Messages
644
I have rebuilt my 1970 fastback and installed a PW3 cam The bike has been back on the road for about a month and I've covered about 250 miles. She starts and runs well and the exhaust note is crisp and raspy. Whilst I have only briefly taken the revs up to 5000 as part of my breaking in process, the acceleration is not that impressive. Lots of noise but not much go. I was expecting a marked improvement over the pre strip-down standard. (that was with a broken top ring on each piston and 0.012" wear on the bores and the original std cam) I was meticulous in setting the cam timing to achieve 0.145" lift at TDC as per the instruction sheet and that involved retarding the cam by 5 (crankshaft) degrees over the standard timing marks. With the std timing marks I had 0.165" lift at TDC i.e. cam is opening too early = advanced.

The $50,000 question is, should I advance the cam to standard timing mark settings to try and improve the performance? there is no kick in the pants as you open it up and that seems to echo what one of the UK NOC members says. There must be a good few members with PW3 cams fitted. I would appreciate any feedback on your experiences. The carbs are Jim Schmidt flatslides and are as fitted before the rebuild and were good then, Ignition is Boyer and set to 31degrees BTDC at 5000.
 
If you haven't run it in yet, its too early to judge ?

Don't be too gentle, they need some (short) strong bursts of acceleration to make and keep the rings seated.
 
PW3 is a pretty hot cam, close to stage 2.

I had some of the same symptoms as you with the JS stage 1 cam. My cam is slightly tamer than yours but still a spicy meatball.

I thought my timing was good also until I took some advice from Jim and took a look into the exhaust at TDC to witness the valve position. I am going to copy and paste what he sent me. Although the number are not quite the same, the part about looking into the exhaust should be.
I ended up with the cam advanced 15degrees and the characteristic of the cam came alive being very strong of the line and at 3750 rpm a beast is awaken all the way up redline. You should expect to have to do some adjusting but when it is right it's righteous


STAGE 1 CAM TIMING from Jim Schmidt

You must have at least .185” gap between the valves when they are on the seats for adequate valve clash clearance with a JS stage 1 cam. Use the butt end of a drill bit to measure. Trim the OD of the valves or sink them into the head to get adequate clearance.

WITH .005” TAPPET CLEARANCE AT TDC THE INTAKE VALVE LIFT SHOULD BE APPROX .165" AND THE EXHAUST VALVE LIFT SHOULD BE APPROX .145" ADJUST YOUR CAM TIMING ACCORDINGLY.

IF BOTH VALVES HAVE THE SAME LIFT AT TDC (APPROX .155”) THAT IS OK BUT YOU WILL LOSE SOME LOW/MIDRANGE PUNCH.

DO NOT ALLOW THE EXHAUST TO HAVE MORE LIFT THAN THE INTAKE AT TDC (see below).

WHATEVER YOU DO – ALWAYS VISUALLY CHECK THE VALVES AT TDC. Looking in through the port; with a tiny flashlight (magnification helps) – you should see that the intake has the same or a few thousands of an inch more lift than the exhaust. THIS IS ASSUMING THAT THE VALVE SEATS ARE LEVEL AS WITH NEW STOCK HEADS.
 
hi gripper,lots of noise but not much go indicates to me that you don't have enough compression,what cr you running, chris
 
chris plant said:
hi gripper,lots of noise but not much go indicates to me that you don't have enough compression,what cr you running, chris
Until that cam timing gets right, you might as well forget about compression. And remember, compression is very misleading when we are talking hot cams.

Compression may even seem a little weak when kicking over, but when that magic rpm number hits, It will be undeniable.

Gripper, I am no expert and the things I say are my experiences bases on help from experts.
Please do some research.
 
That means ; at TDC the valves are on the overlap ( how unusual *) therefor slightly more (lift ) on the intake than Ex (ditto *) means ' zero point ' slightly fwd ( of tdc ) ( ditto *) .

Thus . rotateing about tdc , observeing closeing poits . The ' neutral point ' , = Eqal Lift , is a nad fwd B.t.d.c. ( ditto )

if its late ( at tdc or later ) itll hold the power off till your at higher rpms .

NOW , once shes all familiar with rpms , as in redlined and run a thousand plus , all the thermodymensional fits will be familiar , and shell go like snot . IF its got decent carbs & ignition .
and not stuffy blocked mufflers . Overly baffled ones may not suit the camshaft . Straight through ones would . Removeing them would ascertain if theyre a problem , and sound really cool .

You useually pull the rpms up in there , 6.000 / 6.5000 , at somewhat open throttle then cut back to find neutral throttle , leading & trail . To establish throttle / rpm characteristics .
So as to obtain fineese & control banked way over , apexing , holding drift / slip angle , and acceleration to maintain .

Haphazardly whacking it open dragging a peg could get exiteing otherwise , and might damadge the scenary .

As In , if yr not running it ' on the stop ' for undetermined periods , you not generateing masses of heat to cook things .
Useuall to whack it on , Hit kill switch & check plug readings to estabish if jetting reasonably satisfactory ( putting a drop of oil on threads reinstalling plugs )

Basically , the Throttle Resonse IN the Powerband , will tell you if youve got any grunt .
At this stage , with a tight motor , the thernodynamics running up into it from low revs arnt nessesarilly getting the pulse dynamics off humming .

mashing the throttle up around there will , and get it to catch / hook in , as it were . The Intake / Exhaust pulse waves determineing the chamber charge density & filling .

So keep a ear to it ( not a Ear Muffling full face , scarf , draft excuder & ear plugs . you need the Ear unobstructed .
The odd check to see the jettings not nasty makes a lot of sense . Negligant Not To , in fact .

If the mufflers are like a stifled plugged whistle . Un Plug Em .
 
Thanks gents, I'm running standard CR with a +0.020" rebore Hepolite (Taiwanese) pistons and pea-shooter exhaust
 
Hi

I have a lot of experience with PW 3 cam in a 500. I have also talked with Peter Williams about this cam and he explained what he was trying to do with it.

First off yes recomended timing is set at 145 thou on inlet at TDC. Peter said if you want to try anything more try to advance it a little - so your first stock set up might have actually been ok.

But now a few things I have learnt. First off a PW 3 has more lift than standard.

When installing a cam like this you must

- check for interference or hitting of the valves and pistions. Clearance should be a good 60 thou when measured with plasticine

- check for coil binding of the valve springs. You should have a least 100 thou clearance at full cam lift before the valve is coil bound

- did you install new cam lifeters or at least have the faces of the lifters reground before installing the new cam. This is a must or you risk tearing up your new cam

- did you put cam assembly paste on the lifters and cam. Again you risk tearing up the cam in the first few minutes of running

- did you pour about an egg cup of oil down the push rod tunnel before starting the engine for the first time. Again failure to do this will tear up the cam.

- did you check the lifter for full a free motion with the new cam. A higher lift cam may require you adjust or modifify the strip of metal that locates the lifters/followers in place. When i installed my cam I mesured the full lift rotaion on all cams before putting the head on. I found one of the lifters were binding

- did you check the cam for full and free rotation in the cases.

I trust you used the correct 11 thou tappet clearance.

This should be a start. If the cam is installed properly the PW 3 is a very good hot street production racing cam. It is Mike Hemmings' favourite
 
The cam has been fitted following all the directions from Mick Hemmings, The lifters are free and there is no issue with the installation. My question is about the valve timing. The ign timing is 31 degrees at 5000rpm and the carbs are as supplied for a 750 by Jim Schmidt. I'm leaning towards the standard settings being 5 degrees advanced, and most rebuilders just fitting it with the standard setting and not taking the time to check for 145 thou at TDC and being satisfied with the result.
 
gripper said:
The cam has been fitted following all the directions from Mick Hemmings, The lifters are free and there is no issue with the installation. My question is about the valve timing. The ign timing is 31 degrees at 5000rpm and the carbs are as supplied for a 750 by Jim Schmidt. I'm leaning towards the standard settings being 5 degrees advanced, and most rebuilders just fitting it with the standard setting and not taking the time to check for 145 thou at TDC and being satisfied with the result.

Advancing your cam 5 degrees is where I would start. Be very cautious and check for piston interference and valve position in the exhaust port.
Another handy item is a cam chain with a master link. Once set, the continuous chain can be put back on, but in the mean time, it make life a bit easier.
Here is some good stuff.
http://victorylibrary.com/brit/norton-c.htm
 
I believe that at one stage Peter Williams sent one of his guys t o buy a set of Triumph Race cams, so Norton could copy them. I've been involved in timing a few old race bikes and there are similarities between most of the fast ones. Even though the applications might be different, two valve Jawas, SFC laverdas both use timings similat t o the old E3134 Triumph cam. In 1978, I was involved in preparing a Z1R kawasaki for Bathurst. We had an Italian cam for it which was made by the suppliers to Ferrari, (reputed to be Termignoni, but I'm not sure that was the truth) , the timings were also similar to the E3134. Top end power was never a problem with the big Japanese fours , however most of our guys used Yoshimura stuff. The bike I timed gave the fastest speed down Conrod Straight in the superbike race that year.
There are a few things about cam timings worth knowing - the 1959 7R AJS was the fastest 350 single in the late fifties. BSA used better race cams in their 1958 350cc Gold Star BSA than their earlier models. If you look at these two bike's cam timings in Tuning for Speed and compare them with the racing commando cam timings, might be interesting.
 
From years of playing with cam timing in my 500cc Triumph, I found that advancing the exhaust cam beyond a certain point made the noise louder , and the motor slower. What is important are the opening and closing points for both inlet and exhaust, setting the lift at TDC is intended to set those so that the standing waves in the inlet and exhaust tracts are optimised to give best power over a certain rev range. I suggest you should fit a degree disc to the crank, and see where the timings are occurring at nil tappet clearance, after youve used the lift at TDC to set the cam. Tuning for Speed gives a list of timings for various old race bikes, and you can see whether yours make sense . My feeling is that in your bike, if it is intended for road use the inlet probably wouldn't open before 65 degrees BTDC.
 
I'm learning good stuff on dialing in a power maker. The lower the CR the more rpm before cam can pack it in. Even a degree can be felt once cam close to optimal, but each cam degree change messes with the header and muffler effects and the mixture and timing. Like a new sail boat or an old piano, twitch one thing then must counter skew another or performance falls flat. Advancing cam closes intake soon so help lower rpm while retarding cam delays intake closing to pack more in at hi rpm so the momentum in ports can flood in before exhaust pluse pushes it back out. It might be good to get a vernier cam sprocket to dial in easy then remove and make key to fix it and avoid the risk of the veneer 'lock' pin vibing loose for bad juju.
 
The spec sheet that Mick Hemmings supplies gives the following timings:
Inlet opens 50degrees before TDC
Inlet closes 82 degrees after BDC
Exhaust opens 84 degrees before BDC
Exhaust closes 48 degrees after BDC
These figures are taken at the valve but not sure if that is with zero valve clearance or the 0.011" normal clearance.
Looks like it's time to get the degree wheel out again and get back into the timing chest.
 
One of the things I learned from mmy Triumph was about the exhaust pipes. I started with 4 inch dia. megaphones, and ended with a two into one pipe which gave respectable lap timings with much less terror. I started with a relatively small diameter tail pipe, and ended with one which gave no flow restriction, and the pipe still took 1000 rpm off the top, but al least gave a modicum of torque. The cam timings were adjusted by trial and error, until I got sense from the system. On my Seeley 850, I advanced the standard cam 12 degrees to compensate for the two into one exhaust, and it seems to work very well. It comes on with a rush, and pulls like a train. The power characteristics give no anxiety whatsoever. I used to lose sleep when I was racing the Triumph.
 
hm, your note on adv. cam with a 2-1 exht may be invaluable for me to know. Predicting the power hits is vital for my style of fast on Peel, so double good news you delivered. The few 2 tokes i've tried were too touchy to nail while leaned very far but a blast straight ahead.
 
A two into one pipe is usually much gentler than separate pipes. It depends a bit on cam timing how high the 'cam spot' is, but if it is too high and you use megaphones, the kick can be savage. With my Triumph I used a CR gearbox with the first gear where normally second would be. When it dropped off the cam, you could be doing 60mph in a corner, and slipping the clutch was extremely hazardous. The two into one pipe introduced a bit of sanity. The bike was slower but faster, if that makes any sense.
 
gripper said:
The spec sheet that Mick Hemmings supplies gives the following timings:
Inlet opens 50degrees before TDC
Inlet closes 82 degrees after BDC
Exhaust opens 84 degrees before BDC
Exhaust closes 48 degrees after BDC
These figures are taken at the valve but not sure if that is with zero valve clearance or the 0.011" normal clearance.
Looks like it's time to get the degree wheel out again and get back into the timing chest.


Egad , its ordinary to use .020 in . for cam spec. settings , on our NORTON .

seems to be someone who speaks english , Here : http://www.tildentechnologies.com/Cams/CamBasics.html

PW3 Cam timing


Though the silly sausage hasnt drawn a line vertically , through the cam axis . if we did , we would see , with your ' Symetrical + 1 degree timing FIGURES , that throwing the thing Two Degrees Advaced gets woth your after .

So merely getting it at the centre of the overlap ( as pictured - both valves , I & E , ' about ( by Eye ) open ' = The Same Amount , and seeing if the swines just before ( 2 Deg. ) T.D.C. , is a adequate check .

up to 5 Deg. early would be fine for steet , ( bring cam in earler . or ' On ' the Cam ' thus power earlier )

Late timeing is for upper rpms . So you wouldnt run short stroke settings in a long stroke . Unless you were aiming for 8.000 rpm's .

A.C. , the old ' over tuned ' bit where it takes off like a cut cat , on the cam . but is , as they said , whoolie ' of it . Depends on Chassis , Circuit , opposition etc .
A Ex to suit one cam , might be ratshit on another . as in my 2 - 1 - mega was gutless on the SS but seemless zero rpm to past redline on the stock S cam .

Interstate ( long ) headers had got ' the stutter ' if there , at 3.200 . After that increases in increments , Hold on decidedly at 4000 , eyeballs back at 5.000 , softening past 6.000 .

which you did miss on occasion , but the 80 mph sweet spot wasnt really the thing for suberbia , and she just climbed from there , so 115 was nice n breezy .
I had considered adding a zero to the citys speed adviseory signs overnight . This wouldve sorted things out .
 
The bike was slower but faster, if that makes any sense.

Alrighty Racer Alan, you've now revealed enough to want you to have your way with my favorite ride to share the orgasms. I have to get going slow enough I can be on essentially full traction power before through and out of turns. [its not really a skilled turn if not requiring leaning more than 45'] I've had to develop habit on downshifts to speed up an instant or at least stay same tire thrust an instant before backing off throttle or rear can wash.

I guess I'll have to buy a cheap wire welder to try to construct by trial/error a 2-1 along the lines of insight on the power band behavior. Ms Peel was just a so so spunky 60 lb lighter Combat until one last mod by shot gun in pure frustration nothing to loose - then in still depressed trigger happy mood I snapped throttle 1/2 way in drive way in 2nd at 30 mph to end up on tail light shocked, so re set way firmer and pulled trigger further *** still ended up lifted over the racer seat back to snag on tail light mount!!!! A shit eating grin cracked ear to ear permanently and I became a sports bike hunter cooker and eater. Absolute power over others corrupts absolutely. My SV650 is rated 70hp/365 lb and was neck-neck puller up 3 gears to 70's but Peel and all other real sports bikes would leave SuVee so far behind in short opens no way to catch back up. Going by the many contests I had with myself as well as others Peel was in the mid 70 hp/ 55+ lb torque power. My P!! was more like 90 though and 100 lb lighter yet plus nose low so I'm not very impressed by sport bikes G force tolerance, just their ability to keep their meger pull going longer for top speeds.

PW3 is famous road racing cam designed to ease valve train stress so keep experimenting with this and that till the effects start to sink in or if nothing much improves, think CR or milder came for the CR.

Alan your Seeley behavior tells me its quite capable to break free some to ease turning loads sharper. I had to break through a fear threshold taking sport bikes to full stable lean at speed then nearing apex grit teeth and add a blip more power to step into a new orbit of extra sharp control. The break frees I'm into only last half a heat beat at most, when power on tap to be able at will. I abhor slides-drifts but handy to know to recover a failed turn by going wide, but got to be going too fast not to break loose one end or the other, so usually faster than others willing to take it.
 
Status
Not open for further replies.
Back
Top