Performance cam Tick over

[Hogie]

Hi Folks,
             the standard cam fitted to the TR4A gives a very smooth tick over 600 rpm typical.  17/57  57/17 valve timing.

Would you think that a slightly tuned cam would give a more lumpy tick over giving a tick over in excess of 1000rpm
Moss (Kent) TT1104N  31/68 - 68/31.

When first installed last week I thought I had it all installed correctly. The engine started but needed a fair bit of fettling to calm down.  It appears to go quite well but the tick over is quite rough.

Today I took it all apart again. The reassembling appears exactly as I did it last week.

Tomorrow should be interesting.

Roger

[Andy Flexney]

Hi Roger,

I have the TT1004N Fast Road cam (37/63 73/37, 280 deg. duration) installed and I can get the tickover down to about 700 RPM but it is lumpy. I usually have it set between 750 and 800 RPM. That is with the standard flywheel. I used to have a lightened flywheel which made it worse

On the other hand how long is it on tick over compared to running great between 2500 and 5500 RPM 🙂

AndyF

[Hogie]

Hi Andy,
   thanks for that it gives me hope.
I have been told that I now need to get the carbs tuned for the cam, preferably on a rolling road.
I had the dizzy adjusted for the standard cam two years ago.  I'll have to send that away to be sorted for the new cam.

I'll get there but it is a lot of work. All I wanted was a good quality standard cam but nobody would guarantee the quality of of a cheap (£150) cam.

Roger

[Andy Flexney]

Roger,

I didn't bother with tuning the SUs more than the normal set up. I am using SM needles which are the standard needles and the mixture is fine all through the rev range. Perhaps a little rich on tick over but I live with that as I have not been able to find an alternative needle that is the same as the SM but a little weaker in the first couple of steps. This does mean that after 15 to 20 minute on tick over the engine chokes itself to death but again how often do you leave it for that amount of time on tick over?

The dizzy might need tuning but I would not send it away to be done. You will perhaps need a little more advance in general and that can be done on the veneer knob.

AndyF

[Guppy916]

how many degrees BTDC are you running on tick over 

[Dannyb]

When I rebuilt my engine Sp1t 1500 standard cam. I had the same problem with tickover. I had to run the carbs richer.

It turned out I had installed the cam 1/4 deg out. It may be a good idea to double check cam timing. 

[Hogie]

Hi Folks,

        many thanks for your replies but I think I have now sorted it.

Can't remember the BTDC degrees but whatever the book said (either 4 or 10 !!)

 

Hi Danny,  I would not have thought 1/4 degree would have such an effect. But you may well be spot on.

Quite often you can time them +/- 5' to place the torque where you want.

 

In the end I removed the TT cam and fitted a Newman PH-1.

It hasn't got the intense oomph of the TT cam but it is significantly better in both build quality and performance to the standard cam.

 

I also found that the valve springs fitted to the NEW Moss cylinder heads are of the uprated

variety and this may well have put too much pressure on a barely adequate standard cam that was fitted that required me to fit a new cam.

Anybody with a TR 4 pot wet liner and is thinking about cams. I would suggest the Newman as the quality is there with a little more oomph. The standard offering is very poor.

If you are considering a NEW head then think about the vale springs. The uprated ones are very stiff.

Roger