QuestionQUESTION: Hi, I am running SU H6 carbs on a TR6 eng,(presumimg a 125Bhp cam) with a Lucas 41202B dissy.(it has a Vacuum piece)
I am thinking of going for the 123ignition,but this dissy,for my type of british car,does not have a Vac'.
(1)Is it still OK to use this dissy,or are the H6 carbs reliant upon a Vac'? and (2) Does the use of the 123 dissy do away with the neccesity to know the camshaft type.ie,if I had one of these installed I could change the camshaft without having to change the dissy?
(3)I have a North American camshaft,presumably CC series which I might install,from a TR5/TR6. It has one ring on,does this ID its BHP? If so what is it?- Other poss ID numbers are GKN 1844, 05785, a number 9, and a 'written' number of 307621 on it. Can you help establish the BHP and car type,-year? And finally (4)Nort American Inlet manifolds CC series come in 3 groups,- to engine,-CC50000,
from eng'CC50001- CC75000,and CC75001,- CF12500. My question is,- What is the difference between the 3? ie, Is it,- unit size,port size,port position,stud position,or perhaps for different carbs? And is there any interchageability to other Triumph cylinder heads?Hope you can answer all these, Cheers Nick.
ANSWER: Nick,
I see listings for both vacuum advance equipped and not vacuum advanced equipped 123 distributors.
According to the manufacturers documention the 123 has 16 different advance curves loaded in. If you experience problems with one curve then you'll have to experiment until you find the one that better matches your car.
The Lucas41202B is from a later TR250. It should have both an advance unit and a retard unit.
The mechanical distributors were designed to get the best performance and economy by adjusting the timing based on throttle position. Under acceleration the timing would be retarded slightly to prevent pre-ignition (pinging/pinking). Under light throttle/coasting the timing is advanced to get better economy.
I've never seen camshafts referenced by hp ratings(typically it's a duration number, or a prep leven number) , but the 307621 (that's the factory part number) has the following specs:
Original Camshaft Application OE Cam Part no.
2000 TC 1975 'ML'
MM 20001 on MK3 GT6 and TR250 307621
Timing Degrees Duration Degrees Cam Lift
10/50 240 .215"
Valve Lift @1.42 Std Valve Lift @1.5
.305" .322"
Valve Lift @1.6 Valve Lift @1.7
.344" .365"
During the TR6 production run there were changes in the cylinder head and manifolds. I don't have a lot of information on what the cylinder head changes are, but there's a break point between 1971 and 1972 on manifold fitment. Post '72 the two manifolds will bolt up, the difference was related to emissions requirements.
Sorry I can't offer more detailed information. As my profile states, Spitfires are my specialty.
Cheers,
Jim
---------- FOLLOW-UP ----------
QUESTION: Many thanks Jim.
From the info you have given,it must be that this cam is of the 'milder' side,because the GT6 and the Tc Saloon cars were never fitted with a 150Bhp cam as in the later TR6.
Specs for a 150bhp cam,- I would be grateful,Cheers, Nick.
AnswerNick,
Here's a quick list I found online of TR6 cam specs.
Part # Application Timing Valve Lift Identification
? Carburettor 24-64/64-24 0.345"
311399 Carb (LATE) 18-58/58-18 0.360" 3 rings
307689 TR5/TR6(150BHP) 35-65/65-35 0.375" 2 Rings
311399 TR6 PI (124BHP) 18-58/58-18 0.360" 3 Rings
308778 PI Sedan132BHP 25-65/65-25 0.345" Groove
154C Wade Road Cam 31-70/70-31 0.398"
5569 ACE Road Cam 30-70/70-30 0.402"
It looks like the 307689 is the factory cam for the 150hp PI units.
Cheers,
Jim
