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Kent Cams set up. Timing question

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70tbolt Geoff Ullmann
Morgan Hill, California, USA   USA
Starting to sort out my supposedly high performance motor built by Newark Engineering (no longer in business) in the UK. After digging through the pile of papers that came with the car was a booklet indicating it has a Sports Cam from Kent Cams in the UK. "TH5 Sports R" The valve clearance is .022-.024"
"This cam is a high lift/high torque cam with phenomenal mid-range and top end power" According to the booklet. The engine also has roller rockers. Not knowing much about this stuff, I was wondering how this set up might effect the timing? Any recommended setting for the timing? There are no emissions on the car. I have also been trying to contact Kent Cams.

Thanks!
Geoff

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grumpicus Steve Jackson
Leicester, Leicestershire, UK   GBR
From Paul Geithner's website:- http://auskellian.com/paul/links_files/spitfire_cam_specs.htm

These TH series cams are based on the asymmetric cams produced by Kent for the 4 cylinder Ford pushrod engines, and the timing is pretty much the same as the Ford cams. (The 'TH' stands for 'Terry Hurrell', who ran the Triumphtune business in the UK - it was previously known as SAH Accessories, founded by his father, Sid Hurrell.)

clshore Carter Shore
Beverly Hills, Florida, USA   USA
The roller rockers (as opposed to roller lifters) do not affect the cam timing or setup.
It may be worthwhile however to check that the contact sweep pattern between the rollers and the valvestem tips are centered.

You can compare various Spitfire cams using this site (thanks Paul!)
http://www.auskellian.com/paul/links_files/spitfire_cam_specs.htm

The TH5 is listed, and you can see that the intake lobe timing is different than exhaust lobe timing (int open/close = 37/63, exh open/close = 73/27).
So using the simple ELOO method will not work, you must instead depend on a dial indicator.

If you are unable to locate the Kent installation instructions, contact them for assistance:
http://www.kentcams.com/index.asp

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claytoncnc Avatar
claytoncnc Gold Member Marcus Clayton
Melbourne, Ivanhoe, Australia   AUS
The cam timing should be set carefully as outlined above with a dial indicator.

The base ignition timing with this cam will probably not be much different to a mk3 spec car, around 12deg BTDC initial, and around 34 deg at about 3000 rpm.

That may well be quite different from a stock 1500 distributor.

What do you have?

The ignition timing is critical to performance, so once you have it running at around the 10 -12 deg, it would be wise to get the car tuned on a chassis dyno, as I doubt anyone could guess as to the ignition and carb calibrations that are required, nor what you may have.

If the engine is a factory spec, then it is a straight forward out of the book solution, if it differs from factory, or is unknown, then it must be measured and set up correctly.
You can keep asking for opinions, any of which may be right, but most will be wrong.

70tbolt Geoff Ullmann
Morgan Hill, California, USA   USA
Thanks Marcus. I have a 75 1500 but the engine block (high compression) is from a 77 or 78 Spit. It has a True Spark Dizzy. It also has 4 Keihin motorcycle carburators.

I assume the builders (Newark Engineering) set up the cam properly as the engine was received fully assembled when delivered to the previous owner.
Based on your recommendation, I will start with a static timing (right?) of 10 or 12 degrees and then adjust as necessary. Once running I will also try and find someone locally that can do chassis dyno as you suggested.

Geoff

clshore Carter Shore
Beverly Hills, Florida, USA   USA
I suggest that you first off capture the centrifugal advance curve that's in the dizzy now.
This requires only a strobe timing light, some White-Out or white paint, a Sharpie, and a tape measure.

1) Use the tape measure to measure the circumference of the front pulley.
2) Divide the circumference by 360, to yield the distance for 1 degree.
3) Now clean the pulley rim to remove any grease or oil, and paint the surface with white.
4) Use the Sharpie to make marks along the rim from TDC mark at 1 degree or 5 degree intervals, for at least 20 degrees.
5) Disconnect and plug the vacuum advance line.
6) Now run the motor at constant RPM from idle up to about 3,000 RPM at intervals of 250 RPM, capturing the advance at each step.
(A trusted helper is useful here)
7) Mark up the graph of Advance, degrees vs RPM.

Now you will at least know what your distributor is doing, and you can make some intelligent decisions based on facts, rather than 'I guess so ...'

grumpicus Steve Jackson
Leicester, Leicestershire, UK   GBR
In reply to # 1501820 by 70tbolt
I assume the builders (Newark Engineering) set up the cam properly as the engine was received fully assembled when delivered to the previous owner.

I really would not assume anything, especially where cam settings are concerned! Looking at the spec for the TH5 cam, the peak lift on the inlet lobe should be set to be 103 degrees ATDC, unlike the usual 110 degrees ATDC for symmetrical Triumph cams. Make sure the cam is timed correctly before even thinking about ignition setup.

I fitted an early Triumphtune/Kent 'Road' cam to my engine (about 30 years ago), similar to to the TH5, but with less inlet & exhaust durations. IIRC, the recommendation was for 103 degrees ATDC for that cam, but possibly up to 105 degrees. I spent many happy hours with dial gauge & timing disc to get that correct, swapping the cam sprocket around until I got it as close as I could. Maybe a good investment would be a vernier cam sprocket.....

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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, British Columbia, Canada   CAN
Printing a degree tape can save you a lot of work.

https://www.blocklayer.com/timing-tape.aspx

In reply to # 1501826 by clshore I suggest that you first off capture the centrifugal advance curve that's in the dizzy now.
This requires only a strobe timing light, some White-Out or white paint, a Sharpie, and a tape measure.

1) Use the tape measure to measure the circumference of the front pulley.
2) Divide the circumference by 360, to yield the distance for 1 degree.
3) Now clean the pulley rim to remove any grease or oil, and paint the surface with white.
4) Use the Sharpie to make marks along the rim from TDC mark at 1 degree or 5 degree intervals, for at least 20 degrees.
5) Disconnect and plug the vacuum advance line.
6) Now run the motor at constant RPM from idle up to about 3,000 RPM at intervals of 250 RPM, capturing the advance at each step.
(A trusted helper is useful here)
7) Mark up the graph of Advance, degrees vs RPM.

Now you will at least know what your distributor is doing, and you can make some intelligent decisions based on facts, rather than 'I guess so ...'

clshore Carter Shore
Beverly Hills, Florida, USA   USA
In reply to # 1501892 by Tonyfixit Printing a degree tape can save you a lot of work.

https://www.blocklayer.com/timing-tape.aspx
...

The Achilles heel is the fact that printers, whether laser or inkjet, are not calibrated, are not linear.
And precision depends on how accurately you can measure pulley diameter while installed on the car.
The method I described sidesteps those issues.

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70tbolt Geoff Ullmann
Morgan Hill, California, USA   USA
Thank you all for the replies. After digesting all the advice I have come to a decision. I'm heading to my local pub!

Fortunately I have the original motor with new internals but not assembled. If this one blows up or is problematic, that one will go in.

Geoff

claytoncnc Avatar
claytoncnc Gold Member Marcus Clayton
Melbourne, Ivanhoe, Australia   AUS
In reply to # 1501976 by 70tbolt Thank you all for the replies. After digesting all the advice I have come to a decision. I'm heading to my local pub!

Fortunately I have the original motor with new internals but not assembled. If this one blows up or is problematic, that one will go in.

Geoff

Probably a valuable, and strong motor Geoff.
The checking may take some time and effort and new skills, but will pay off in the long run with peace of mind and performance.

Checking cam timing is important, and if it is correct, that is all you have to do.

If it is wrong- thank goodness we caught it, and it can be corrected, with help from me and the rest of the peanut gallery.

Enjoy the pub, I am (6.30 local time) about to do the same

Marcus

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, British Columbia, Canada   CAN
In reply to # 1501986 by claytoncnc
In reply to # 1501976 by 70tbolt Thank you all for the replies. After digesting all the advice I have come to a decision. I'm heading to my local pub!

Fortunately I have the original motor with new internals but not assembled. If this one blows up or is problematic, that one will go in.

Geoff

Probably a valuable, and strong motor Geoff.
The checking may take some time and effort and new skills, but will pay off in the long run with peace of mind and performance.

Checking cam timing is important, and if it is correct, that is all you have to do.

If it is wrong- thank goodness we caught it, and it can be corrected, with help from me and the rest of the peanut gallery.

Enjoy the pub, I am (6.30 local time) about to do the same

Marcus

Totally agree!

As for the printed tapes. I have found mine to be pretty accurate (checking with dividers) within the scope of a small pully.
If an engine is out of a car, I use an 18" diameter, reverse calibrated protractor on the flywheel end.

clshore Carter Shore
Beverly Hills, Florida, USA   USA
Great!

Meanwhile, every other person may have a different printer, a different version of Windows, different Printer Driver Software ...
ALL of which affect the actual scaling of the printed 'tape' image on paper.

Unless you have a PRECISE measurement of the pulley diameter or circumference,
it is IMPOSSIBLE to determine whether the printed 'tape' is accurately scaled,
using a divider, a micrometer, a laser interferometer, or ANY instrument you may have.

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