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Stock 4A camshaft specs


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Hi All,

I am trying to find the TR4A stock cam spec to establish the correct reference/baseline for comparison to what is available "today" as a stock.

I have noted three versions so far, of what is stock namely a) 10/50 50/10, lift .260" Duration NA b)24/56 61/29, lift .265" Duration NA c)17/57 57/17 lift and Duration NA - I am assuming that all three would be timed at 110deg FL and guessing that duration is 270 deg.

 

By comparison the Moss "Road" spec (851-051) is 31/67 67/31, lift .260", timed at 108 deg, duration 278 deg; and the Piper BP270 is 22/66 66/22 Valve lift .411" duration 272 deg timed at 110. The Kent cam equivalent appears more aggressive than these two.

 

My cam is tired after 50 years and the option is to either give it a refresh grind or get the closest to stock, which may be the Moss cam.

Sorry about long post but search did not turn up anything numbers.

 

Thanks all

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Hi All,

 

By comparison the Moss "Road" spec (851-051) is 31/67 67/31, lift .260", timed at 108 deg, duration 278 deg;

 

Thanks all

Hi Alf,

the Moss road cam is a TRiumphTune TT1104N and is made by Kent.

This fits your spec above and your part number 851-051.

https://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/engine/engines-components/performance-camshafts-tr2-4a.html.

 

It doesn;t appear on the Tilden listing.

 

I'm just installing it now. It looks nicely made but the spigot on the front that holds the sprocket is 0.008" over size and the sprocket does not fit.

Measure this before buying. Standard is 0.810" diameter

 

Roger

 

 

Roger

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Thanks Iain, that is quite a tabular presentation of cams - so it would seem that the stock TR4A cam is the 17/57 5/17 (no lift provided.

 

Roger, you have me worried now - the 008" could be a pain, will the fix require lathe and emery work? The Cam does appear to be close to stock though,

Thanks and Cheers

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Hi Alf,

in my case, as there were no other similar cams that would fit and the oversize cam would not fit on my lathe I chose to open the hole in the sprocket..

This is a very simple task but does render the sprocket useless for other camshafts.

 

Very silly oversight by the cam manufacturer.

 

Roger

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Thx Roger,

Well sprockets cost a lot less than cams, so good solution. I note several on the forum use the Newman PH1 with 280 deg duration and almost stock lift of .270". Is this cam slightly more stock than the Moss Cam? I had overlooked checking the Revington site, and they have stock cams. If I read correctly the lift is .290" which seems high for stock, and, the price is huge, so at the moment it's looks like a refresh grind or consider the NewmanPH1

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Thx Roger,

I could not find the TT1104N cam on the Kent site - closest was "high torque" #TR4-4. I have already purchased uprated Followers and a Nitrided rocker shaft (and 86 mm piston/liner kit) from the TRShop), just in case I don't re-use the existing cam, so assume the Followers would be compatible whichever way I go.

Cheers

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Think you are correct Roger, made by Kent for Triumptune originally. Mine was supplied over 11 years ago by Cambridge Motorsport I believe.

Regards.

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Hi Roger,

Been doing a bit more research which leads to the query whether you or anyone might have the specs on the two TRShop listed cams.

 

Also out of curiosity, in the overall scheme of our cars, what is the role of Ivor M Davis, Classic Car Parts - just wondering?

Cheers

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Hi Alf,

the two cams your ask about - one is the standard cam as per the workshop manual.

This has failed in my car. It didn;t sound good from day one (two years ago) and has now been removed. Two lobes badly worn.

I have no info on the other cam.

 

 

Roger

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  • 2 months later...

Due to a failure of the figure 8 gasket on my rebuilt engine I am in the process of taking everything out save for the block itself. The Engine was rebuilt some 25 years ago by XRN in Bracknell and has racing liners etc into with an original stage 2 SAH head which I have also just had converted to unleaded. I have always been troubled by the lack of acceleration in the the low revs, sub 2500 and think that the standard cam is not enough to work with the webbers and straight through exhaust

 

Now I must confess to not fully understanding the various items of inlet angles (e.g. inlet timing 32°-58° and exhaust timing 67°-23° giving 270° overlap.)

but there does seem to be a fast road offering from a number of suppliers such as Moss, Rimmers, Racetorations and Revington, but they all have different specs. and prices.

 

So what should I think about and what is a good option

 

Mant thanks

 

Richard Jennings

TR4A

LPC 442D

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Hi Richard,

the standard cam on the 4A is 17-57 / 57-17 and works OK with the standard engine.

Fitting webbers and an extractor exhaust will not necessarily give much improvement as the valve lift and duration will only allow so much fuel in.

 

If you go up the various meaty cams then your carbs and pipes come into play.

 

I have just fitted a Newman PH-1 road cam ( 30-70 / 70-30 )to my 4A - extractor type pipes and SU carbs.

This gives a much more sparkling performance without ripping your eyebrows off.

In January I had fitted, for a few weeks, the Moss TT1104N - classed as a road cam 31-68 / 68-31 (I think). This was significantly more sporty.

From 2000rpm upwards it accelerated very well indeed.

 

You then have the 'fast Road' cams - Moss https://www.moss-europe.co.uk/camshaft-fast-road-new-tt1004n.html

and other meaty offerings.

 

A great deal of what you want is trial and error.

 

The TT1104N may be a good starting point.

 

Another point to consider - was your standard cam fitted correctly regarding its valve timing.

There is an optimum position but you can experiment and put the cam X degrees advanced or retarded - this will improve the torque either at the top end or bottom end.

Annoyingly to change the various setting or cams requires a fair amount of strip down each time.

 

If you simply want to improve the bottom end experience go for the Newman PH-1

If you want to benefit from the Webers and the pipes then get the TT1104N

 

Roger

Edited by RogerH
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Hi Richard

Roger has it well covered. I settled on the Piper BP270 for probably no other reason than quick service. I could just easily gone for the Newman PH1 (and may regret not doing so yet - we'll see). My rationale was to keep the motor close to stock as I haven't got any peripheral upgrades to justify a more "meaty" cam as Roger calls and really want nice 750 rpm idle.

Hope this all helps

 

Alf

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Dear Roger and Alf

 

Thank you for your quick response which i will work on the costings. I was hoping hat I could remove and fit the new cam without taking the engine out but I am not so sure I can. Any suggestions?

 

Thanks

 

Richard

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Hi Richard,

Roger and others probably better qualified to answer definitively, though with judicious use of strong magnets to hold the cam Followers up and out of the way, it might be doable. I did it years ago on a Kent X-Flow with the pan removed which provided access to the followers - not sure about the TR configuration unfortunately.

 

Cheers,

Alf

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Hi Richard,

you can remove the cam without taking the engine out but it usually requires a fair bit of top end strip down.

 

I was considering using magnets to hold the cam followers up so as not to remove the head etc.

In the end I took the head off as I needed to look at the follower faces.

 

I probably could have done this with a boroscope/camera down the cam bore hole.

 

Roger

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Hi Alf

 

Thanks for your advice, I will see what others have to say as i would like to avoid having to take the engine out.

 

Regards

 

Richard

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  • 2 weeks later...

Finally have removed the camshaft which has some lines on the rear end so have taken the decision to take the block out and replace bearings. This way I can have a rebuilt engine off the car rather than trying to do it in situ.

 

Hopefully there is now light at the end of the tunnel.

 

R

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