Cam replacement

[Tom2000]

The replacement engine has been rebuilt bottom and top end to moss performance specs and has a new standard cam (receipt in hand), I'd like to put a fast road cam in as my old engine had a Kent TH12, such as a TH5, do I need to replace the cam followers as well and should I go long or short profile - whats the difference?

preciate the advice as per usual :)

[mikew]

Tom2000 wrote:

The replacement engine has been rebuilt bottom and top end to moss performance specs and has a new standard cam (receipt in hand), I'd like to put a fast road cam in as my old engine had a Kent TH12, such as a TH5, do I need to replace the cam followers

New cam always new followers, or your cam will have a very short life.

Whats wrong with a TR5 grind ? COme highly recommended, and were designed by Triumph, and not for a Ford crossflow.

mike

[Tom2000]

mikew wrote:

New cam always new followers, or your cam will have a very short life.

Whats wrong with a TR5 grind ? COme highly recommended, and were designed by Triumph, and not for a Ford crossflow.

mike

This is exactly what I am looking at from Canleys a TR5 grind, thanks for the info, research seems to suggest the small journal with have a longer life, but I am not sure why, could someone explain?

[GT6 M]

Tom try  piper hr 270  [ 266 degs ],  its a really good cam,  the 280 [ 276 degs ] is even better,

if you going to go Kent cams, forget about the springs, way too hard.

[Tom2000]

796 wrote:

Tom try  piper hr 270   [ 266 degs ] ,  its a really good cam,  the 280 [ 276 degs ] is even better,

if you going to go Kent cams, forget about the springs, way too hard.

any online suppliers or info?

[GT6 M]

I think  its on james site, the minty lamb,

[Tom2000]

I don't want to start replacing inlet and exhaust valves, i'm pretty set on the TR5 grind, whats the difference between long and small journal TR5 cams?

[Nick Moore]

Small journal camshafts require cam bearings, while large journal camshafts run directly in the block. The cam grind is the same.

I think there was some confusion at the start of the thread between TH5 and TR5. TH is one of the Ford crossflow-inspired Kent camshafts, while TR5 was fitted to Triumph TR5s and early TR6s.

[Clive]

I heard that jag valve springs were very good. Leon posted something a while ago, here or the TSSC board. Cheap as chips too........................

BTW what do you mean by moss performance spec?? normally a performance cam will need matching to the head (ie head may need a bit more compression) so worth a think.

[Tom2000]

Thanks Nick, sorry this is my mistake, I was talking about the TR5 grind not the Kent TH range, although I am curious as to the piper HR range that Marcus has suggested, what I want to know is what level of work will be required to:

- Fit a TR5 grind (long or small) - which should I go for if this is my choice?
- Piper HR 270 - requires specific cam lobes and is about £50 more expensive all in for followers and cam bearing etc.. - but if i went this route would I need to change the inlet/exhaust valves or anything else?

I'm just trying to get the info to one narrow down my options and two work out the quantity of work that is required.

[Tom2000]

cliftyhanger wrote:

I heard that jag valve springs were very good. Leon posted something a while ago, here or the TSSC board. Cheap as chips too........................

BTW what do you mean by moss performance spec?? normally a performance cam will need matching to the head (ie head may need a bit more compression) so worth a think.

So I'd have to have the head skimmed or modified to suit? I was hoping to install a cam without doing this as this will set me back longer than I wanted to..

I'll dig out the paperwork and have alook, just built to the old moss performance tuning manual specs from what I can remember.

[James]

Tom2000 wrote:

Thanks Nick, sorry this is my mistake, I was talking about the TR5 grind not the Kent TH range, although I am curious as to the piper HR range that Marcus has suggested, what I want to know is what level of work will be required to:

- Fit a TR5 grind (long or small) - which should I go for if this is my choice?
- Piper HR 270 - requires specific cam lobes and is about �50 more expensive all in for followers and cam bearing etc.. - but if i went this route would I need to change the inlet/exhaust valves or anything else?

I'm just trying to get the info to one narrow down my options and two work out the quantity of work that is required.

Tom,

I don't think you understand all this so take a step back and slow down - performance doesn't come to those who rush and it'll end up costing you more money.

Small or large is just down to whatever fits in your block - if you have a IV/1500 then you'll need a large unless you want to fit cam bearings. As you have a 1500 it won't rev so I doubt you need the expense or hassle of cam bearings.

Piper cam is no more expensive apart from the cost of the cam. You will need new followers for your new cam anyway. You don't need to change valves.

[Clive]

Tom, do you know exactly what the engine is? Or have you bought it already done? The TT specs doesn't mean a lot, they varied as to what level of tune you wanted. If it has just been reground/rebored, that is fine, but the TT manual goes on about lots of things.
You need to think carefully about what you want. A £30 skim will only take a couple of hours, during which time you can be fiiting the cam and timing it up ;)

[Paul Garvey]

Hi,

This may help:

http://auskellian.com/paul/links_files/spitfire_cam_specs.htm

[Tom2000]

Interesting site Paul, so I suppose it's a case of calculating what level of skim is required to gain the compression ratio that I'm after, I'm assuming 9.5:1 to 10:1. From what I can see about calculating this (once I have the head off) I don't have the tools to do so..

[sparky_spit]

Tom2000 wrote:

Interesting site Paul, so I suppose it's a case of calculating what level of skim is required to gain the compression ratio that I'm after, I'm assuming 9.5:1 to 10:1. From what I can see about calculating this (once I have the head off) I don't have the tools to do so..

All you need to calculate the combustion chamber volume (which will allow you to calculate static compression ratio, and then what amount of skim you need to get any compression ratio you want) is an old CD (or better still one of the clear blanking "CDs" that come on the top of a bulk pack of CDs); some vaseline; a 5cc syringe from your local chemists (don't go in there looking like a druggy...) a vernier gauge (or set of feeler gauges if you don't have one), and some parafin (or white spirit at a push). If the info you refer to above does not give you instructions on how to do it, I'll write some up for you.

However, if you are talking about dynamic compression ratio calculation, then I don't know how to do that - sorry.

[JohnD]

I don't want to offend you, Sparky, I'm sure you would give good advice, but as I've alreay done it, may I offer Tom my own article on "Skimming your head"?
See: http://www.totallytriumph.net/spitfire/skimming_your_head.shtml

The difference of static from dynamic is a factor of the flow efficiency of the ports and valving.   Get those as good as possible to minimise it.
John

[sparky_spit]

Absolutely no problem and no offence taken John. I'd love to say I was going to write something exactly the same.... ;)

My version uses the same method as yours but with quite a bit less finesse and the maths stolen from Jon Wolfe (I think).

One thing I would say is that, if the flat glass piece with 2 drilled holes is not easy to come by, the clear plastic bulk CD pack toppers work pretty well. Their large centre hole is big enough to gently rock the air bubble out, but small enough to make sure the resultant meniscus can be made the same for repeatable tests.

One odd thing... whenever I've done this (about 3 times now) the head has invariably needed about 90 thou off to get it to 10:1 (10.2:1 on one occasion) regardless of what engine 1300, 1500, A series 1275, etc.

Tom - if you go down this route of getting up to 80/90 thou skimmed of the head, make sure you check the new rocker height and resulting rocker tip to valve stem wipe pattern. You may need to shim the rocker pedestals to correct this. It is important to get this right so that you don't suffer premature valve guide wear due to a poor wipe pattern. If you need advice on this, it a whole new subject...

[Tom2000]

sparky_spit wrote:

Tom - if you go down this route of getting up to 80/90 thou skimmed of the head, make sure you check the new rocker height and resulting rocker tip to valve stem wipe pattern. You may need to shim the rocker pedestals to correct this. It is important to get this right so that you don't suffer premature valve guide wear due to a poor wipe pattern. If you need advice on this, it a whole new subject...

Thanks, GT6 Marcus has already given me a full run through guide on how to do exactly this :)

[Tom2000]

Some more photos after a degrease:


and



Tried going over some of the surface rust with very lightly with some 1200 and 1500, removed alittle but not alot.

[JohnD]

Don't want to rubbish the CD-ROM idea, but a flat glass sheet to measure chamber volumes?
A glazier will just have to reach into his scraps bin to find pieces of glass big enough for such a sheet, though he may not have much plate glass (c. 6mm thick, to make it strong).   He can bevel the edges and (To make it easy to handle)  and drill the holes with ease, for a few quid.
Is there a glazier near you?  There are ten in my Yellow pages, and I live in the sticks!

John

[Tom2000]

turns out the cylinder head isn't unleaded, but in extremely good condition. Having it converted to unleaded, new exhaust valves, seats being recut, gas flowed/ported and skimmed to 9.5:1

[rossybrown]

how much for the headwork (if you don't mind me asking)?

[Tom2000]

250 including parts