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Cox GTM ('67-'68) 
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Joined: Mon Aug 04, 2008 8:22 pm
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Post Re: Cox GTM ('67-'68)
I have started my 12th engine rebuild attempt. This time with special pistons in new bores.

Please if You have some time, wisit the link and help me with Your ideas.

http://pistonheads.com/gassing/topic.as ... mid=201476


Fri Jul 02, 2010 11:52 am
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Location: In the workshop
GTM: Cox/Coupe
Post Re: Cox GTM ('67-'68)
As a side note

I have been running in my Rebuilt Honda this week in my Coupe,

No visable smoke at all, even on first start up with all the assembly lube coating the pistons/cylinders etc, I am running fairly large piston to wall clearance and ring gaps due to my intended use.

best of luck with it all

Neil

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IF wile e coyote had a GTM he would have one with Nitrous too! watch out road runner! The First GTM into the 11s then the 10s, PB 10.87 @ 125.5 Mph on A048 tyres, and fully road legal at Santa Pod


Fri Jul 02, 2010 12:42 pm
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Post Re: Cox GTM ('67-'68)
Soo, with my cured engine (and emptied pocket :D ), I am back in action on the Cox.

I plan to start the engine in the car by the ed of next week... nice daydream...

PS: I wanted to upload a couple of pics, but did not succeeded.


Fri Aug 06, 2010 5:45 pm
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Post Re: Cox GTM ('67-'68)
Still got issues with uploading files to the forum I cannot get it to work again hopefully Henry will have more luck

Neil

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IF wile e coyote had a GTM he would have one with Nitrous too! watch out road runner! The First GTM into the 11s then the 10s, PB 10.87 @ 125.5 Mph on A048 tyres, and fully road legal at Santa Pod


Sat Aug 07, 2010 10:42 am
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Post Re: Cox GTM ('67-'68)
No problem. I am pretty sure You have tried it hard.
My pics are by far not that important.


Sat Aug 07, 2010 11:59 am
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Post Re: Cox GTM ('67-'68)
I have started my engine in the car first time. It is running nice, all except that I dont have charging. Does any of You have any experience with Lucas 11ACs?


Fri Aug 13, 2010 4:33 pm
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Post Re: Cox GTM ('67-'68)
My Cox did the first meters on its own power. Wow! The orange clutch diaphragm and the shorter clutch pedal of the Cox makes the clutch feel quite hard... errrm... I mean race-car like :D .

Unfortunatly my 11AC alternator smoked away 1 min later :cry: ... does any of You have lucas-smoke to bring it alive again?


Wed Aug 18, 2010 10:45 pm
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Post Re: Cox GTM ('67-'68)
I have done my first kms in the GTM (yet without grp body), its like an Ariel Atom :D.


Fri Aug 20, 2010 7:22 pm
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Post Re: Cox GTM ('67-'68)
Soo I have done a few kms with the Cox.

I am generaly statisfied with it soo far. But have a few issues.

The suspension not 100%
I have a setup of:
Camber front: -1 degree
Castor front: 3.5 degree
Toe-in: 1.5mms

Camber rear: -1 degree
castor rear: used to make wheelbase equal
Toe-in: 1.5mms

The car holds the line firm, though it is not willing to get back to straight. It has no oversteer, no bumpsteer. But it fast corners, when I step on the accelerator, it becomes uneven. Not much, but I can feel. It is "nervous".

Shall I increace the toe-in on the rear?

The other problem is engine related. It is not willing to rev above 6K. I have set the mixture with WBO, it is spot-on. I have tinkered with the ignition, but did not affected the problem.

It strarts around 5.5, where the engine developes a noise.

Can it be valve gear problem? I use a Kent 276 with old GT double springs. Can they be weak?

The power curve is deffiniatly not at its end at 6k. I can fell that is should have some left above... :?


Sat Aug 21, 2010 8:49 pm
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Post Re: Cox GTM ('67-'68)
Oh yes: I have some problem with my master cylinders. It looks that they leak fluid through their caps (I use Automec Silicone fluid). I think as the car has a very hard suspension, the caps leak the flid through their air vents.

I have found this. Can it be a solution?

http://www.spridgetmania.com/web/item/B ... Detail.cfm


Sat Aug 21, 2010 9:08 pm
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Post Re: Cox GTM ('67-'68)
Tyre size and pressures.

These have a huge effect, the rest of your settings are pretty good, personally I run

1.5 negative camber front and rear.

Castor near 5.5 degrees from memory.
1mm toe in on each wheel front and rear.

all my tie rods are set to the same length on a setting jig.

good to hear your starting to get some use.

Neil

_________________
IF wile e coyote had a GTM he would have one with Nitrous too! watch out road runner! The First GTM into the 11s then the 10s, PB 10.87 @ 125.5 Mph on A048 tyres, and fully road legal at Santa Pod


Sun Aug 22, 2010 9:43 am
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Post Re: Cox GTM ('67-'68)
CamelotR wrote:
The other problem is engine related. It is not willing to rev above 6K. I have set the mixture with WBO, it is spot-on. I have tinkered with the ignition, but did not affected the problem.

It strarts around 5.5, where the engine developes a noise.

Can it be valve gear problem? I use a Kent 276 with old GT double springs. Can they be weak?

The power curve is deffiniatly not at its end at 6k. I can fell that is should have some left above... :?


The 'noise' could be valve bounce due to weak springs.
This would certainly limit the ability of the engine to rev.

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1967 Cox GTM; 1970 GTM Coupe, GTM Spaceframe (Two is never enough!)


Sun Aug 22, 2010 10:12 am
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Post Re: Cox GTM ('67-'68)
Hi, could it just need to be run in before full throttle attempts are made? i had an mg metro new in 1987, after the initial run in it would not pull more than 75 mph, i then got on the motorway and left my foot flat out on the throttle and eventually the mph crept up one mile an hour at a time, when finished it was remarkably quick for a standard mg metro ? Maybe after the run in period it will free up a bit? 6000 rpm is close to max for a standard 1275 im not entirely sure what your cam should make it rev to?
Also after reading your thread , i used to have a fair bit of doings with the a-series engines and from memory (and it was a long time ago) the pistons are marked with the bore size and an arrow to be fiited the right way (or the writting goes one way)i will try to find a manual to double check this as i used to work on motorbikes too and they nearly always are ), also i did build an uprated engine and had to add a breather to cope, what i did at the time was use the redundant mechanical fuem pump port in the block and drilled a hole in the cover plate and welded a pipe to it with a canister at the end , it seemed to work fine, i can remember Andy collard (bridgewater, AC racing services ) stressing the importance of this , i was running a kent 296 (from memory useful power was available from about 3500 rpm to about 8000 rpm), metro comp pistons, chrome rings, uprated head, aldon dizzy, full maniflow. good luck with it , cheers


Sun Aug 22, 2010 12:55 pm
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Post Re: Cox GTM ('67-'68)
WEST wrote:
Tyre size and pressures.

good to hear your starting to get some use.

Neil


I have set the front 1.8 the rear 2 bars. It may be too much. The tires are 165/70 10 road Yoko's. The alloys are 6 inch wide.

The engine problem robbed me 5 months. Though it was a nice learning experience. I am back on it again. I hope I will be able to get it moted by the end of september. Nice daydream :roll: .


Sun Aug 22, 2010 1:01 pm
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Post Re: Cox GTM ('67-'68)
I will see if the engine lets up a bit after some miles on the clock, but it has now about 400kms, and reving quite free. And it realy hits a "wall" at that rpm. ignition or valve bounce is my bet now.

The pistons for th 1275 are not marked - thats for sure. The are simmethric items, with no pin offset. The 998 has indeed got offset pins, thus marked front-water pump.

My engine problem was verified to be the bad honing pattern.


Sun Aug 22, 2010 1:08 pm
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