TR6 Moss advance kit maximum advance question

[steveg]

I just installed the Moss advance unit on my non-smog-inspected 74 TR6. The instructions, vaguely, say to time it like a TR250.

Looking through the Bentley manual, the maximum advance for any of the distributors is 28 degrees at 5600 rpm!

With the Healey the max is 35 degrees which kicks in at around 3000 rpm - shouldn't I be looking at something like this for the TR6?

Would like experience-based advice.

 

[poolboy]

I think what you're seeing in the Bentley is the centrifugal advance,,,add that to the initial (non retarded) setting at idle...You'll be closer to the 35
British Vacuum Unit is probably the supplier of the Vacuum Advance module that Moss and others are selling retail.
I bought mine direct and it's a 5-13-10 meaning the timing will advance up to 10 degrees when the ported
vacuum source is betweem 5 and 13 in-Hg.

 

[steveg]

I think what you're seeing in the Bentley is the centrifugal advance,,,add that to the initial (non retarded) setting at idle...You'll be closer to the 35
British Vacuum Unit is probably the supplier of the Vacuum Advance module that Moss and others are selling retail.
I bought mine direct and it's a 5-13-10 meaning the timing will advance up to 10 degrees when the ported
vacuum source is betweem 5 and 13 in-Hg.

Poolboy,
Thank you for the reply. Think I'll time it like the Healey and see if it pings. If no pinging, Bob's my uncle!

 

[sp53]

I have no experienced-based advice

 

[poolboy]

Here's 2 pictures showing the BVU vacuum ADVANCE module and where I tapped into the required ported vacuum source on my front carb...
These are ZS carbs of course, I don't know where you'd find a ported vacuum source on SU or Weber carbs though.

 

[steveg]

Poolboy - my rear carb happens to have the stock vacuum port - previously blanked off; I repurposed the hose previously connecting the thermal vacuum valve to the distributor retard unit:

Rear SU HD6 vacuum port - will be front carb on Triumph:

 

[poolboy]

If you feel vacuum when the engine is idling, it's the source for the retard.
The one in the picture on the topside of the ZS carb is a ported vacuum source and is OK for the vacuum Advance, but it won't do a thing for a retard module except cause it to retard the ignititon timing when the centifugal advance is trying to advance the timing, which is counter productive.
As far as the picture of the SU carb, I really don't know , but you don't feel vacuum when the engine is idling then it's ported.
If the opening for the port/nipple is on the manifold side of the throttle disc when the disc is in it's idle position then it's considered 'manifold vacuum'
If the opening is concealed behind the throttle disc or covered by the throttle disc when the disc is in idle position, it's considered 'ported vacuum'
Maybe this will explain it better than me, Steve.
https://www.britishvacuumunit.com/ported-vacuum.html

 

[sp53]

Thanks pool boy good stuff

 

[steveg]

Good link, Poolboy.

I wasn't clear. I replaced my retard unit with the British Vacuum advance unit - which was labelled as such even though I bought it at Moss.

The ported vacuum stud as shown above is undoubtedly factory and works fine. I set up the maximum advance with it to around 35 degrees at 4000 rpm.

The stock setup on the SU above is also correct and operates the distributor correctly.


Did you have your distributor reworked as BV advocates for $199? I'm wondering if they replace the weights or what? Maybe I'll give them a call next week and report back here.

 

[poolboy]

Ok, Now I understand, Steve.
Way before I sent my distributor off the Rob at BVU, I had Jeff at Advanced Distributors recurve and recondition the distributor.
Rob said he would check it over when he got it, mainly for the advance curve compatibility with the advance module.
Once he did he said he wouldn't change a thing....I owed him for the module and I believe 25 dollars for doing the module installation.
The module itself is fragile as an egg and when it cracked a few years ago,(probably my fault).. I sent the distributor back for a replacement module...He only charged for shipping as I recall.
Rob advised against turning the distributor by grasping the module in hand.

 

[steveg]

I'll discuss recurving with BV. Looking at my timing with the light, it felt weird - like it went from very retarded and kept on advancing to 40+ degrees above 4000 rpm. Am definitely interested in having it recurved. I've used Advanced several times in the past but think Jeff's got like a 10 week turnaround right now.

When I had the points plates off, the weights below seemed very complex-looking compared to those on the Jag 22D6 I'm running on my Healey.

FWIW, this is a 41558.

I added an extra ground wire made from Pertonix ultra-flex wire as the original ground was fraying.

 

[poolboy]

Steve did you put a roll pin in to keep the Advance module from moving when vacuum is applied ?

 

[steveg]

Steve did you put a roll pin in to keep the Advance module from moving when vacuum is applied ?

Yup. One was included with the module; the old one from the retard unit is also still usable. Took a pretty fine drift to get it out!

 

[poolboy]

Good deal...I just couldn't make out if there was one in the picture.