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Thanks for the information and website Nick. I've asked the gentleman with the blocks to check the end float for me, and where possible to check for the damage you've shown in the pictures.

 

7 hours ago, TimBancroft said:

One thing never mentioned when discussing GT6 with Lucas Pi., is the positioning of the fuel pump and all its paraphernalia. Most Pi TRs seem to have smelly boots/trunks, whilst not so bad in a convertible, in a GT6 the smell of fuel would be annoying to say the least. I presume that the fuel pump will be mounted where the spare wheel would sit?

For the ease and simple maintenance, a pair of HS6 SUs is not a bad option.....appreciate that I may sound conservative her. But my GT6 mk2 2000cc with a TR5 cam, modded head and smooth bottom end is a powerful enough and I get to enjoy 30mpg...how much is fuel in the USA?

Pi of course offers great initial acceleration and in a light car such as a GT6, will be fun...but don't dismiss carbs...what about bike carbs?

Apols for the conservatism!

My GT6 already smells like fuel . I've seen Steve's implementation from his blog, I was considering doing it that way, or putting it underneath the car somehow.  Speaking of the fuel system in general, what is the system pressure, and would a fuel filter like the glass bowl ones fitted to E types work before the pumps, or is the pressure to high? Does anyone filter just before the MU?

I'm not interested in the HS6 option. I've already got 2 sets of PI gear being refurbished and calibrated, so I'll be sticking to this course of action. I want to build a car that Triumph could have made. Besides, as Nick points out, if for some reason I should abandon my Luddite ways I can go to EFI.

Kind Regards,
AJ

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AJ,

Filters.    I use a Bosch pump, that comes (With Malcolm-at-Prestige's recommendation) with a pre-pump filter whose cartridge can be changed, and a post-pump filter that cannot and must be replaced if necessary (only ever once, in a contamination incident).      I use a Facet as a lifter pump to a swirl pot, and that has it's own, coarse, cleanable filter.   Of course, as a Luddite you may not approve!

John

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On 10/14/2019 at 7:59 PM, saleon said:

Gentlemen, 

 

I got a measurement of the port spacing for the GT6 head I was interested in. Please see below:

I had thought the correct port spacing was 0.95", according to this image from BPNW 

https://www.bpnorthwest.com/catalog/product/gallery/id/1908/image/6392/

But checking my TR6 head, it's 0.90", which matches the photograph

Is the BPNW figure incorrect, can anyone confirm that the port spacing on a wideport head is supposed to be 0.90" ?

US market production engines up to the end of model year 1971, Engine number CC750000, have narrow port cylinder heads - Intake port spacing 1-7/8″ center to center.

This cylinder head was fitted with an shallow intake manifold.

US market 1972 onwards (LATE) engines had the same port spacing as the PI head - Intake port spacing 2-3/16″ center to center.

This cylinder head was fitted with the long branch intake manifold.

My personal observation has been that the early narrow spacing head does NOT have the dowel or dowel hole drilled cylinder 3/4.

i don't know if it an 100% accurate description.. just an observation

.625" spacing for an early head..

ja511.jpg

 

 

 

early.jpg

late.jpg

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Good info - thanks :smile:

Quite a subtle difference visually - can see how people buy them by mistake at autojumbles.  Of course they get into the UK second hand market after being taken off re-imported US cars so PI can be fitted!

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If you are building a 2.0L engine you need a head that is .100' thinner than a 2.5L. I had a 2.0l head on a 2.5 with very bad results. I then changed to a US spec. 2.5 crank and head (so 2.5 displacement) and then needed to remove .100" from the late 2.5 US head to get to 9.2:1 per Richard Good research. https://www.goodparts.com/tech_docs/TR6_Compression_Ratio.html.

The narrow port head was an early TR6 head and only TR6 intake manifolds exist which don't accommodate the gt6 low hood. there are GT6 wide port manifolds which can be used on 2.0 and 2.5.

I would think a MK3 gt6 head would be easy to find as rebuilding an engine to 2.5L is about the same money

good luck and there is no substitute for proper planning. ( I am a happy 30 year customer of BPNW)

Per Chris Witnor 3.30" head thickness is ideal for a 2.0L and don't for get proper push rod length.

 

 

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Also don’t forget that a lot of the later 2L engines, including the GT6 Mk3, have domed pistons and use the same head thickness as the 2.5.

Starting with a 3.30 thickness head and using flat pistons is the way to go.

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According to John Thomason's book, domed pistons were fitted to 2L GT6s from KC10001 ('72).  At the same time CR was reduced to 9.0, which tallies with 122344's report.

But fitting a previous 2L head to a 2.5L crank will get you a CR of about 14!  Fine, if you want to run on pure ethanol!

John

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the domed pistons was a cost consideration to allow the same head on engines in export markets with low and normal compression ratios  saving the head milling expense.

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Gentlemen, thanks for all the information. I've been busy with my OD transmission swap, I'd say it's about 90% complete now.

On 10/19/2019 at 8:58 AM, JR2 said:

US market production engines up to the end of model year 1971, Engine number CC750000, have narrow port cylinder heads - Intake port spacing 1-7/8″ center to center.

This cylinder head was fitted with an shallow intake manifold.

US market 1972 onwards (LATE) engines had the same port spacing as the PI head - Intake port spacing 2-3/16″ center to center.

This cylinder head was fitted with the long branch intake manifold.

My personal observation has been that the early narrow spacing head does NOT have the dowel or dowel hole drilled cylinder 3/4.

i don't know if it an 100% accurate description.. just an observation

.625" spacing for an early head..

 

 

 

 

 

 

JR2, thanks for the reply. I've seen the corresponding 0.65" figure from BPNW, It's just that when I take the same measurement for my cylinder head, it's about 0.9" not 0.95" as in the picture, likewise for the GT6 Mk2 head I was trying to purchase. 


Yep, sticking with a 2L engine, 9.5CR so was looking at the head thicknesses per Christ Witor's site. I'm trying to determine if it's safe to shave my thick head down to 3.3" -the opinion seems to be that it's too risky- vs getting a GT6 Mk2 head which I've been informed should be a wideport head. 

Planning is important, I like doing it, you should see the research and planning I did for this little transmission swap. I'd definitely like this to go as smoothly as possible considering I really don't have a clue what I'm doing, and am acquiring parts as I go. So I'm certainly open to ideas as to a suggested order of operations.

The initial plan was to get the head sorted out while I wait on the PI stuff to be refurbed. Still in the process of that.
After that I'd start acquiring the bits for a 2L block and determine the work that needs to be done and quotes for it and have whatever machining necessary done.
The next step for me was to figure out the fueling situation, I was going to buy another gas tank and determine the plumbing.

I've got most of the parts to convert the GT6 to a cable throttle, so that would be the first change I make to the car in preparation to fit the PI. After my move I'd assmble the engine and get ready for the swap.

Kind Regards,
AJ

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