E3134 cam timing

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
12,137
Country flag
Right then chaps, I'd like to open said can of worms as I'm currently teetering on the brink of delving into the cam timing on my '68 T120 (I wasn't gonna, I was gonna do what most of us do and think "it ran OK before, so it must be fine" but the reality is that with 50 years of PO intervention, the cams could be bloody anywhere! And now I've started thinking about it, well, you know how it is...

An initial look at factory opening / closing methods caused much vagueness. When I look at lobe centre figures, my exhaust cam looks remarkably cock on. My inlet cam looks quite a way out, almost one full tooth. So I am pondering my options as to the best course of action to take...

Opening and closing timing figures are notoriously useless due to Triumphs manufacturing tolerances and the 'stack up of tolerances' of the many different components all interacting.

So, either lobe centre timing or lift at TDC seem more reliable / favourable.

Triumph opening / closing figures translate into 100.5 degree lobe centre timing (I think).

What's the opinion of our learned members on this, any strongly upheld views on ideal settings, alternatives, pros and cons of such?

Hit me...
 
Joined
Mar 12, 2013
Messages
300
Country flag
Your previous connections with Dave Degens should place you in an ideal position to get answers to every aspect of Triumph valve timings in general, and 3134 cams in particular.
I'm sure Dave has forgotten more on this subject than most other folks will ever know, and this includes anyone from the Southern hemisphere!
 

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
12,137
Country flag
Ha!

That's a fair point, and I will.

Trouble is, Dave's worse than me and I fear that after 10 minutes discussing this with him I'll have the whole motor stripped and an 8 valve kit on order... again...
 
Joined
Feb 10, 2009
Messages
1,966
Country flag
I can tell you what I did and I won't be offended if you ignore it.

I timed the exhaust to the opening point at 20 thou clearance as in the manual.

I set the inlet cam as advanced as possible, still maintaining sufficient piston to valve clearance at the start of the inlet stroke.
 
Joined
Feb 10, 2009
Messages
1,966
Country flag
I was going to say I don't know, but you jogged my memory and I may have noted the timing in an old manual somewhere.

Not all that relevant to a normal bike anyway, as it's an iron-headed T110 with twin Amal 928s and T140 size inlet valves.

The E3134 cams were ok until the big valves went in. Advancing the inlet timing didn't much tame the resulting low speed tantrums, but opening up the inlet valve clearances to 8 thou has helped.
 

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
12,137
Country flag
Low speed tantrums are easy to solve... open the throttle!

If you do find any notes, please share the figures. I think my inlet is at around 113 degrees. Advancing it by one tooth would make it 98 and a bit. The exhaust is 100.5. So I reckon I'll advance the inlet one tooth (check all clearances) and see what it's like.

If I've got my head around this properly, it should give it quite a bit more 'punch'.
 

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
12,137
Country flag
I had an iron engine not dissimilar to yours once, but it had twin 30mm carbs and 9:1 pistons. It was a nice motor, the only thing letting it down was the fact it was in a hard tail chop !!

In my defence, it was quite a few years ago now.
 
Joined
Feb 10, 2009
Messages
1,966
Country flag
I tried 30 mm Amals, but they didn't make my bike faster (my bike ain't your bike though) and they complicated low speed tuning, because of things like pilot mixture and slide cutaway controlling mixture at higher speeds than they do with smaller carbs.

9:1 pistons meant for alloy headed 650s give you an actual 7.5:1 ratio with the iron head. Did on mine anyway.
 
Joined
Jun 30, 2012
Messages
9,660
Country flag
From memory, the recommended timings for the E3134 s were 55, 72, 72, 55. I would try to set them at that with nil tappet clearance and if you cannot achieve the timings, work out the errors and add half to each end. I think the cams are intended to be used with straight pipes of 38 inch length. If you are using mufflers or megaphones, the timings will probably different from the recommended when optimised. Typically in a 650 motor those cams give a strong surge of power at 4000 RPM and a bit more go even below that.
 
Joined
Jun 30, 2012
Messages
9,660
Country flag
I tried 30 mm Amals, but they didn't make my bike faster (my bike ain't your bike though) and they complicated low speed tuning, because of things like pilot mixture and slide cutaway controlling mixture at higher speeds than they do with smaller carbs.

9:1 pistons meant for alloy headed 650s give you an actual 7.5:1 ratio with the iron head. Did on mine anyway.
Depends which iron head you have. The iron head on the 1954 Tiger 110 was high comp.
 
Joined
Feb 10, 2009
Messages
1,966
Country flag
Depends which iron head you have. The iron head on the 1954 Tiger 110 was high comp.

Anyone have a reference for that statement?

The 54/55 iron headed T110s sold in the UK had flat topped 8.5/1 pistons. The ones I've seen anyway.
 

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
12,137
Country flag
If flat topped pistons gave 8.5:1 then why wouldn't domed (9:1) pistons give more?
 
Joined
Feb 10, 2009
Messages
1,966
Country flag
The iron head had a different combustion chamber shape from that of the aluminium head.

The iron head T110 piston tops were raised, although flat.
 
Joined
Jun 30, 2012
Messages
9,660
Country flag
If the iron head 1954 iron-head Tiger 110 is fitted with E3134 cams, it can be faster than expected. The lower comp. is more than compensated for by the lighter pistons. If you compare the 1954 T110 iron head with the 1955 aluminium, you will see that where the valves are in the iron head is much deeper than in the aluminium head. We used one of thoseT110 iron heads on a speedway bike with the 12 to 1 comp. pistons - methanol fuel of course. The combustion chamber shape in the 650 Triumph is wrong. A much better way to go is use BSA 350 Goldie pistons and machine the crowns to fit the head. That way you end up with a squish-band and an unrestricted flame front, as well as lighter pistons. Every used 650 Triumph head or piston has got coke on the crown on the side away from the spark plug.
 
Joined
Feb 11, 2015
Messages
245
Country flag
Eddie does your unit cam wheel have the three keyways like the pre unit , using the three key camwheels will allow more accurate timing as you can creep the timing either way by a half tooth if needed
 

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
12,137
Country flag
Yes, they have the 3 keyways.

As I understand it, you can get within 2.5 degrees of any figure with this set up.

Mine also have two separate marks to align the inlet cam wheel. One is for T120 and TR6 and the other is for 6T.

Mine had been set to the 6T marks. So, for a T120, was basically one tooth out.

I've now set it to the T120 mark.

According to my calculations, stock timing is 100.5 lobe centres. My exhaust comes out at 100.5! The inlet, now I've changed it, is 99.5.

So, if my scribblings are correct, my inlet timing is now within one degree of perfect.

Which is plenty good enough for me!
 
Top