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rogerguzzi

Duplex Cam Chain Alignment

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Hello You Clever lot(creeping over!)

                                                             I am back on Spitty,s new engine after holiday and Snow clearing

I am fitting the duplex cam chain and it is 0.045" out of line (Crank sprocket lower than cam sprocket!)

Does anybody have offset dimensions for both sprockets?

Mine are Crank sprocket +0.250" back face to chain face,  Cam - 0.275" to chain face.(binned old simplex ones)

Now I could fit a lot of shims? or machine a bit off the back of the Cam Sprocket?

I do not like lots of shims 0.004" or 0.006"?

I have fitted I think +0.005" rear thrust (I think) and the crank grinder took a skim off it, so should be the same position.

I have checked the old camshaft and it is the same for slot to front face?

So what do we think?

Roger

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The Vitesse/GT6 manual says that "Timing sprocket alignment is controlled by shims interposed between the rear face of the crankshaft sprocket and a shoulder on the crank shaft.

However as you have gone duplex, is the crank sprocket symetrical? will it mount the other way around and line up?

Alan

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24 minutes ago, oldtuckunder said:

The Vitesse/GT6 manual says that "Timing sprocket alignment is controlled by shims interposed between the rear face of the crankshaft sprocket and a shoulder on the crank shaft.

However as you have gone duplex, is the crank sprocket symetrical? will it mount the other way around and line up?

Alan

Hello Alan

                  Both only fit one way but I have heard reports of poor quality(now there is a surprise !!!!!)

Might have known a bargain would bite me in the bum!

I think Triumph would have got it closer than that or would have offered shims in thicker sizes? they  expected it to be within -0.010" so could be adjusted up to level!

Roger

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Are you sure it's the right cam sprocket.  I had one a while back that turned out to be a TR 4-pot one and offset was one of the issues.  Think it was more than you report though.

I may have a used OE 2.5 in my stash if that helps?

Nick

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21 hours ago, Nick Jones said:

Are you sure it's the right cam sprocket.  I had one a while back that turned out to be a TR 4-pot one and offset was one of the issues.  Think it was more than you report though.

I may have a used OE 2.5 in my stash if that helps?

Nick

Hello Nick

                     I checked the sprocket and it is the right one?(TR4 pot one has a bigger hole and fixing holes bigger PCD and it is even both sides) checked an old one.

Thank,s for the offer but I have machined it now and it is within 0.002" (I recon there is 0.010" to 0.015" clearance chain to sprocket)

Plus even if it made of mild steel it has a lot less work to do on my engine(no PI ,no Distributor and tachometer drive only 8 valves to open!)

Roger

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Hello All

               I thought I would do the valve timing today!

I thought I will do it John,s way (same as WSM with large tappet gaps)

I have 2 DTI,s and made 2 dummy push rods (fat ones)

I have managed to get it to within 2 degs advanced (which in my book is good as will retard slightly when chain and sprockets bed in)

I thought I would check it all the other ways (here I go again!)

So first thought I would do the opening of the inlet, is my thinking right I have to allow for the tapped clearance (0.014") then note the degs (30) and it is as near as I can tell still 2 degs advanced.

Then I went for the lift at TDC (0.060") and with a lot of messing recon it is still 2 degs advanced, the total lift on the Newman spec is 0.270" but I get 0.285 ish?

So I suppose that is correct if you take off the 0.014" clearance?

Am I correct?

Roger 

Ps was still shovelling snow to get Yet out this morning!!!!!!

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Well the cam lift should be the cam lift and shouldn't be affected by the tappet clearance.  I assume that you are measuring that lift off the top of your dowel?  Have you by chance measured the lift on all the inlet lobes?

Alan

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Hello Alan

                 I have had a quick check and they are 278", 282",283",284"

Newman say cam lift 0.270" and valve lift 0.405"

I may be wrong but I still think if you have say 0.015" clearance then you will not get 0.270" lift from a 0.270" lobe so you would need an extra 0.015"?

I will check all the valve timing tomorrow to see if I need to alter it for average across the range!

I hope this is all worth it? but it keeps the old grey matter exercised .

Roger

ps what is a standard rocker ratio? if I divide 0.405" by 0.270" I get 1.5 ratio!

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I see what you mean about not getting 0.270 lift from 0.270 if you factor in 0.015 clearance, however I have  haven't seen (or didn't realise) that a cam manufacturer might quote a cam lift figure minus an allowance for tappet clearance. Working on the theory that bigger is better would you quote your cam lift as 0.270 or 0.285?

I could be wrong and hopefully someone will step in to correct me.  I could just see someone quoting valve lift minus clearance....

Triumph rockers are quoted as 1.45  although real world figures seem to be between 1.42 and 1.46

Alan

Edited by oldtuckunder
haven't not have

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As the 0.270" is cam lift, not valve lift I don't see how the tappet clearance comes into it.........  Never seen it quoted for valve lift either for that matter - though there it's easier to see how it could apply.

Nick

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Hello All

              The Gravy thickens as they say

Here is the cam spec

Fast Road/Rally Camshaft (TRIS/280/405 PH2)

Triumph 1300cc to 1500cc Large Bearing 4 Cylinder Fast Road/Rally Camshaft (TRIS/280/405 PH2) - Newman Cams Online.

Good Mid Range Power.

Power Band: 2000 - 6500
Duration In: 280.0
Duration Ex: 280.0
Valve Lift In: 0.405
Valve Lift Ex: 0.405
Cam Lift In: 0.27
Cam Lift Ex: 0.27
Timing In: 30-70
Timing Ex: 70-30
Full Lift In: 110.0
Lift In: 0.060"
Valve In: 0.014
Valve Ex: 0.016
Material Type: Blank
Rocker Ratio: 1:1.5

0.270" x 1.5 = 405" valve lift!

0.282"(average) x 1.5 = 0.423" valve lift!

I still think if you have 0.014 clearance on the base circle you are only going to get 0.268" lift at the push rod top!

Roger

ps I sometimes wish I did not think so much and just stick it in and time it to No1

 

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Roger 

If the cam lift is 0.270 then the push rod will always lift 0.270, however the effective full valve lift with 15 thou clearance will be 0.270 * rocker ratio - 0.015

I though you had a PH2/PH3 hybrid?

PS.  If Newman have a supply of Triumph 1.5:1 standard rockers can I order some please? 

Their valve lift figure of 0.405 gives a cam lift of 0.270 with 1.5:1 rockers

However if you use my calculation above (0.270 x 1.45) - 0.014 (their quoted clearance) = 0.405 (their quoted valve lift)

so they are either quoting valve lift using a 1.45 rocker ratio minus a 0.014 tappet clearance, or they are incorrectly using 1.5:1 without an allowance for tappet clearance.  By chance in this instance they are the same, I'd hate to guess which they think they are using

Alan

Edited by oldtuckunder

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Hello All

               Now this may come as a shock to you all?

I have spent most of the morning measuring and checking!

What I have found is my rocker ratio is 1.55 to 1!

I checked this by fitting one rocker shaft pedestal(forked one) over No1 valve,then used packing blocks and the adjuster screw to get it level.

Then I measured the gap between the rocker arm and the valve guide (0.875") then I put 0.270" packing on the block and remeasured the gap(0.455) so that gives 0.420" lift.

So 0.420" divided by 0.270" = 1.55 (tried 2 rocker arms with the same result)

So then I thought why not ask the manufacture? so I spoke to Ken Newman and my thinking is correct! (He said perhaps it is the way they have worded it 0.270" is the lift you get but you have to add the clearance on to the lobe height)

If you was checking with the head on and valve gear set at correct clearances you would see 0.270" lift at the push rod end of the rocker arm.

Cam profile (lift) is 0.270" + 0.014" and + 0.016" = 0.284" and 0.286"

I did a quick check on lobes 1 & 2 and think there is 0.002" difference

Roger with the aching head!

ps other companies may tell a different  way?

DSC06688.JPG

Edited by rogerguzzi

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1 hour ago, rogerguzzi said:

 

What I have found is my rocker ratio is 1.55 to 1!

 

If you have standard triumph rocker arms (picture?) then I'm tempted to refer to John D's often advice of measure thrice!  as I detect a faint wiff of something on the wind from Denmark!

I do know you need to be careful when measuring rocker ratio as both end of the rocker move in an arcs around the central pivot and the ratio changes at different points during the lift cycle, it may be by altering all the heights you have affected the arc(s) and thus the apparent ratio.  If not can I buy your rockers please!

Alan

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3 hours ago, oldtuckunder said:

If you have standard triumph rocker arms (picture?) then I'm tempted to refer to John D's often advice of measure thrice!  as I detect a faint wiff of something on the wind from Denmark!

I do know you need to be careful when measuring rocker ratio as both end of the rocker move in an arcs around the central pivot and the ratio changes at different points during the lift cycle, it may be by altering all the heights you have affected the arc(s) and thus the apparent ratio.  If not can I buy your rockers please!

Alan

Hello Alan

                  I have done some more measuring and testing.

I fitted an exhaust valve with a light spring so I know the rocker arm is in the right position.

I then adjusted valve so it just touched the valve tip and on my packing, then I put 0.270" packing under the adjuster and set the DTI to zero.

I then removed the 0.270" packing and let the valve up slowly and read the DTI which was 0.405"

So If I multiply 0.270" by 1.5 it = 0.405"

So the rocker must be 1.5 to 1 ratio or am I missing something?

Roger

ps over to you!

I have checked all the valves openings and they are within 1 deg and the opening at TDC shows the same

The maximum advance is 2 deg with some at 1 deg!

So I am happy with that as I still think when chain and sprockets wear in it will drop back 1+ deg!

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DSC06698.JPG

DSC06700.JPG

Edited by rogerguzzi

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Three things IMHO 

1) Remember the ratio alters as the rocker goes through its swing, so you have to start with the rocker at the angle it would be when on a push rod that was on the heel of the cam.

2) You can't measure using the bottom of the  ball of the adjuster, as far as I'm aware all rocker ratio measurements are taken through the centre line  of the ball as that is where the cup on the push rod engages.

3) There was a three, but I have forgotten it typing 1 & two.

4) As you have your block assembled why don't you drop the head on and using a real push rod measure what you really have, not what it appears to be.

5) If you really have 1.5:1 rockers then someone has either done some serious engineering on them or spent some serious money in the past.

I think I may have just recreated a scene from Monty Python

Alan

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18 minutes ago, oldtuckunder said:

Three things IMHO 

1) Remember the ratio alters as the rocker goes through its swing, so you have to start with the rocker at the angle it would be when on a push rod that was on the heel of the cam.

2) You can't measure using the bottom of the  ball of the adjuster, as far as I'm aware all rocker ratio measurements are taken through the centre line  of the ball as that is where the cup on the push rod engages.

3) There was a three, but I have forgotten it typing 1 & two.

4) As you have your block assembled why don't you drop the head on and using a real push rod measure what you really have, not what it appears to be.

5) If you really have 1.5:1 rockers then someone has either done some serious engineering on them or spent some serious money in the past.

I think I may have just recreated a scene from Monty Python

Alan

Hello Alan

 Point 1) The rocker is at the correct angle as it is sitting on the valve tip!

Point 2)  I am lifting the rocker exactly as the push rod would! 0.270" I can not for the life of me see what difference were on the ball you push as it is a cup and it will push on slightly different parts as it rotates in the cup!

I may drop the head on tomorrow as this is intriguing me! if only to clear my mind!

Roger

ps no one expect the comfy cushion? 

 

 

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Alan,

Are you sure about point 5?   Or are you and Roger discussing smething else?

AFAICR, Triumph rockers are 1:1.5, and I look in my Moss/TriumphTune Performance Manual and catalogue for 1992, to see them advertisng their roller rockers that "increase the ratio from 1.5 to 1.65:1"

John

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1 hour ago, JohnD said:

Alan,

Are you sure about point 5?   Or are you and Roger discussing smething else?

AFAICR, Triumph rockers are 1:1.5, and I look in my Moss/TriumphTune Performance Manual and catalogue for 1992, to see them advertisng their roller rockers that "increase the ratio from 1.5 to 1.65:1"

John

Hello John

                   I have always believed that the ratio was 1.5 to 1 if not 1.55 to1?

Still it gets the (old)brains going

Did you manage to calibrate your micrometers?(not that I need the setting bars back any time soon)

Is there any luck with Edis6? why not take it off the car and jerry rig it on your lathe? were you can run it at steady speeds!(still think it points to a duff Edis or bad wiring?)

Roger

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39 minutes ago, rogerguzzi said:

 

Point 2)  I am lifting the rocker exactly as the push rod would! 0.270" I can not for the life of me see what difference were on the ball you push as it is a cup and it will push on slightly different parts as it rotates in the cup!

Ok, the push rod doesn't go straight up and down, as the rocker rotates the top of the push rod goes through a small arc, depending on the angle it starts at and the angle it ends at it may or may not go through vertical, if it ends up at the top of the lift not vertical then you have less lift than the full cam lift. We are only talking a few thou but a few thou makes all the difference between a rocker ratio of 1.46 and 1.5

Now it could be that you have a stock rocker assembly that at maximum lift is actually 1.5:1, if you do you are very lucky!

 

39 minutes ago, rogerguzzi said:
1 hour ago, JohnD said:

Alan,

Are you sure about point 5?   Or are you and Roger discussing smething else?

AFAICR, Triumph rockers are 1:1.5, and I look in my Moss/TriumphTune Performance Manual and catalogue for 1992, to see them advertisng their roller rockers that "increase the ratio from 1.5 to 1.65:1"

John

OK the problem seems to be that "Triumph" claimed (somewhere although I can't find it) a 1.5:1, this urban myth has be replicated, copied, regurgitated ad nausium,  it appears in the real world that stock triumph rockers normally range in the 1.42-1.46 range for "total lift" (not the ratio at all points in the lift cycle). All late model triumphs Vitesse, GT6, TR6, Spitfire etc all use the same rocker.  By altering height of pedestals, length of push rods, this ratio can be affected  a bit, as can the actual ratio at different points during the lift cycle.

I attach a few google results that seem to confirm this.

 

 

Stock TR6 rockers are 1.46:1 ratio. Good Parts offers roller rockers in 1.55:1 or 1.65:1 ratio. 

 https://www.tapatalk.com/groups/spitfireinformationexchange/rocker-arms-for-1500-t4287.html It is said that the actual ratio of the rocker arms is only 1.4:1 and stepping up to the true 1.5:1 that Triumph claimed to have installed ...I've read and heard anything from 1.42:1 to 1.46:1 for factory Triumph rockers, and it's tough for me to measure rockers to that precision the way I've done it. The difference in ratio from 1.42 to 1.5:1 translates into around 0.020 of valve lift for a stock cam.

Various sources give different rocker arm ratios for the TR6, but they are all in the 1.45-1.50 range. http://www.britishcarforum.com/bcf/showthread.php?47069-TR6-Roller-Rockers

Final lift ratio i.e. the the point at the top of the cam lobe, is of far less significance than the ratio between 50-75% of lift when the quicker a valve is opening the more charge get pulled in, by 100% lift the intake speed has slowed enormously, so a rocker and cam lobe geometry that gives maximum acceleration between 50-75% with a low rocker ratio, should perform better that a higher ratio rocker which has maximum acceleration in the 75-100% lift range.  There are  a few references out there that show that some increased overall ratio rockers actually have worse ratio's at the critical points (due to bad geometry) than the lower ratio OEM rockers they are supposed to be an improvement on.

Alan

 

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16 minutes ago, oldtuckunder said:

Final lift ratio i.e. the the point at the top of the cam lobe, is of far less significance than the ratio between 50-75% of lift when the quicker a valve is opening the more charge get pulled in, by 100% lift the intake speed has slowed enormously, so a rocker and cam lobe geometry that gives maximum acceleration between 50-75% with a low rocker ratio, should perform better that a higher ratio rocker which has maximum acceleration in the 75-100% lift range.  There are  a few references out there that show that some increased overall ratio rockers actually have worse ratio's at the critical points (due to bad geometry) than the lower ratio OEM rockers they are supposed to be an improvement on.

Alan

Hello Alan

                 I agree with this statement I had a Norton International motor cycle and the cams that came with it (a box of bits) were what they called 5 figure racing cams and they were almost straight up flat on top and straight down(but racers drop the clutch and stays in the power band) and wear does not matter as long as it lasts a few races!

Roger

ps we want the best of both worlds! which I believe variable cam timing does? but not what we want on our old cars?

We are all MAD really!

Edited by rogerguzzi

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Hello Alan

                  I think you are right about the rocker ratio!

I  dropped the head on with just 2 valves in No1 cylinder and set the tappets at 0.014" and 0.016" and did some measuring and I do not get 0.405" lift on valve!

Its more like 0.385" lift  which would equate to 1.45 to 1 !

So the urban myth is right.

I am not to worried as the 0.405" lift gets the collar to close to top of guide so the extra 0.020" will be better.

I will measure a standard cam tomorrow to work out what the lift would have been!

I have acquired 2 NOS Stanpart head gaskets for non recessed block but which way up do they fit?

Instinct says part no etc up? but does it matter as the oil hole is re enforced both ends!

Roger

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Edited by rogerguzzi

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Doesn't matter which way up on the non-recessed ones.

Interesting work on the lift/rockers.  One of those things I've occasionally wondered about but been too lazy to check.  Usually restrict myself to just checking they all open the same amount to make sure the cam is ok.

Nick

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Pass on the head gasket, I've never used a composite.

Glad (but only in a way) that my comments on the rocker ratio were in the right ball park, was about to pull my rocker cover and do a real measurement. It also means I'm not wasting my time as a side project playing with building a set of 1.5:1 rockers

Alan

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8 minutes ago, oldtuckunder said:

Pass on the head gasket, I've never used a composite.

Glad (but only in a way) that my comments on the rocker ratio were in the right ball park, was about to pull my rocker cover and do a real measurement. It also means I'm not wasting my time as a side project playing with building a set of 1.5:1 rockers

Alan

Hello Alan

                   I  was going to try and bush my rockers(cocked up the first one!) but with a suitable jig I think you could re bore them a bit off center which would probably give 1.5 to 1?

Roger

Edited by rogerguzzi

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