AJ's PI GT6 Mk2

[saleon]

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

[Gt6s]

The place to mount the pump (even Lucas) is under the boot floor behind the LH wheel.

Laurence

[JohnD]

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

[JR2]

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..

 

 

 

[Nick Jones]

Good info - thanks 

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!

[122344]

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.

 

 

[Nick Jones]

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.

[JohnD]

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

[122344]

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.

[saleon]

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

[saleon]

Hello Again Everyone,

The bottom ends I was looking at have an end float of 0.009", which is 0.001" over the suggested clearances i've found online. I think it's safe to assume the thrust washers for these blocks haven't dropped. Pending that final confirmation I'll be getting one (hopefully soon). Any more checks I should ask for before purchasing?

In terms of the PI fuel pumps, does anyone know where I could find the specs for its current draw? I'd like to size an alternator with that in mind, running the pump would be a new continuous load, and my Lucas alternator is both undersized and on its way out with its intermittent behaviour.

Kind Regards,
AJ

[JohnD]

A few seconds on Google finds the Revington data sheet on Lucas fuel pumps: https://www.revingtontr.com/productimages/docs/00001684/is6-2-protected.pdf

That says the pump draws 3.5A., so no need to get a high output alternator.     More important is to ensure no volts drop on the long journey to the back of the car.    The usual solution is a dedicated, 30A, live cable to the boot and a relay, switched by the ignition switch, or a separate toggle, your choice, to power the fuel pump.

John

[saleon]

Thank-you kindly. My search terms on duck-duck-go didn't bring up the revington site. 

[Nick Jones]

The importance of a decent size feed with good connections cannot be overstated. Volt drop caused the current to rise..... which causes more volt drop.....

Lucas number seems low. Real world maybe a bit higher - up to 5A maybe. Still not huge.  Bosch pumps take more, 8 - 10A dependent on model. 

[saleon]

Gentlemen,

Now that i've got the reconditioned PI parts to hand, I'd like to start planning out the plumbing.

I wanted to know what the sizes of the hardlines for the MU supply from the pump were, and for the return, as used on the PI TR6s, and whether or not they should be increased in size.

From SteveA's blog, I saw that he was using a fuel swirl pot with a low pressure pump to fill it, before it went on to the Lucas pump. My reading suggests the Lucas pump was capable of at least 16 gal/hr flow rate, is there a recommendation on size of swirl pot (1L say) and should I ensure that the lifter pump to flll it is at least as capable of the same flow rate?

Finally, does anyone know the fitting sizes and specifications for the fittings on the filter module, pump, PRV etc, and what kind of flare the fittings accept? I"ll try to go to the hardware store this week and see if I can figure out the thread specs at least.

 

Kind Regards,
AJ

[JohnD]

Prestige Injection (http://www.prestigeinjection.net/pricecarg.htm) used to do a kit of hard tubing and hoses to do all the connections.  I don't know if they still do so, under the new and excellent management of Carl Fitchett.  Ask him!

The pump to M/u pipe was 8mm, the return, 5mm, both OD in copper pipe.  It comes in a coil and I found that making the curves to get them around all the turns on their paths was impossible in one piece, and resorted to rubber hose connectors for the return, under low pressure.      For the high pressure side, compression connectors from my local B&Q  did the job nicely and have never failed (touch wood!)

A 1L swirl pot is perfectly large enough and what I have.    16gall/hr is well enough!     I probably use about 8 galls/hr when racing, WOT most of the time, and a Bosch pump will supply many times that.    My lifter pump is a Facet Gold top that wuill shift 36galls/hour, as it's importnat that the swirl is kept full.

Sizes and connectors - again Carl Fitchett will be your best bet.

John

 

[saleon]

Thanks for the lead John, I"ll send an email. I would have thought the lines were imperial rather than metric. I'll source some cunifer lines to use.

Would one of those SU fuel pumps work well as a lifter?

[JohnD]

SU pumps are desisgned to run intermittently, stopping as the flaot chamber stops off flow.

Facets in contrast are deisgned tom run continuously.

[saleon]

Mt. Fitchett said the Main fuel line is 5/16, and the return is 3/16, and to use only cupro nickel, so I'll get some lengths of those, which also invites the question, what kind of flare? I was thinking about using some AN bulkhead fittings at the ends of the lines, to make the connection between the hoses to the MU.

AJ