1970 GT6 MK2

[JohnD]

Yes, wheel width, between the rims.  But mixing wheel sizes on same axle - 5.5/4.5 - not a good idea.   Same tyres may fit both, but they will have different rolling diameters, so the diff will work hard, all the time.  And traction may differ, not good for stability in  braking or acceleration.

Or, have I misunderstood you, again?!!

John

[thebrookster]

If you plan to use the 4.5 solely as a spare, it will work.

Proviso to that is you need to treat it like a "space saver" spare if you use it: limit your speed and essentially only use it to get you somewhere to repair the main tyre.

For this reason, I would not bother fitting a decent tyre to it, simply find the cheapest available that fits and matches the others size wise.

Phil

[Nick Jones]

10 hours ago, Speedysix said:

4.5's fit the gt6 fine right

Yes! Didn’t we do this already?

About 6 FOC in my carport…. Bit rough though.

[Speedysix]

So we did! I apologise the cars clearly making me loose my mind! Thanks for all the advice its just one of those things on the list I'd like to get ticked off!

I'll be turning my attention to the head shortly too, getting the port work done and matching my new inlet manifold to the head and carbs. I emailed chris whitor about if he still offers his inlet manifold flowing service and I never had a reply, same story with Owen Lloyd at park Lane, just ignored me when I asked about doing my seats.

Anyway, I'd like to get the rockers done at some point too, just one of those smaller jobs left in the corner. The shafts..... are there any stories out there on differences in quality? Canley sell them for about 25 whereas Ebay sellers like mark field(jigsaw) sell them at 50+. I've yet to look at the rocker arms, some I can feel a dip where the valve meets it, others it's not as deep.

 

[egret]

Well I've just made steps to deal with my rockers, several of which are probably similar to yours and have dents in them. I've taken a grinder to a cheap eBay feeler gauge set to get the 10 thou one narrow enough to just interact with the valve stem.  I think this solution was about £4 including shipping and wear on the grinder!

Eventually I'll probably go through my various sets and think about properly building a decent set from the best bits, but for now a modified feeler gauge to work with the dents is my solution.

[Nick Jones]

Chris Witor sells a tuftrided rocker shaft. Have one in my GT6 with new rockers from Rimmers bought years ago. Not extensively tested but ok so far.

Others are reputed to be made of cheese, but no personal experience.

[Speedysix]

Thanks Guys, I'll be looking at it in the coming week. After a bit of looking and research, rimmer stock the correct tuftrided one with threaded plugs either end, canley don't specify. Springs on these shafts, reusable? Should be fairly easy to tell if they've gone soft but unlikely?

It would be nice to begin work on the head items soon, the quicker that's done the quicker it can go to the machine shop as it'll prohably sit there for a good few weeks. I just need to order some carbide milling bits and carbide grindstone things. It had occured to me that the cr will be affected slightly having unleaded seats cut with new valves but hopefully having it refaced too will even it out to pretty much where it needs to be. 

[Speedysix]

Progress has been slow lately, fell extremely unwell with glandular fever so unfortunately lost about 3 weeks worth of work on the gt6! But back to health now which is a plus! 

Prior to the plague kicking in, I ended up sticking with the lap belts and just refurbing them. It's amazing what a lick of paint can do! I also ordered the correct split rivets that hold the little plastic britax cover on the end of the belt.

Rear seal has also been fitted and cleareances checked with feelers 

Currently I'm moving onto the manifold and head, all my porting tools have arrived so I can begin. The manifold needs porting to accept my hs6's, I can't remember how I did it the last time so I essentially set the carbs up on the manifold, used a straight edge to make sure they're level on top of the machined piston face, got it in the correct position and tightened the nuts slightly. I then simply scribed around the inside with a long very thin screwdriver.

Scribe Is easy enough to see. I'll take it to the outside of the line to account for the thickness of the screwdriver. The gasket seemed slightly bigger so I'll port to the line, test fit again and enlarge any more if needed. This is the only downside to elongating the holes on the carbs, it's a little tedious to get the perfect fit.

I can't remember the purpose of the little step just past the carb opening inside the lower edge of the manifold(last picture), I've seen some people smooth this out, last time I left it alone and just blended the area. Is it needed?

 

 

[Speedysix]

Finished the inlet the other day, here's my diy setup, blocked off all the ports with old disposable gloves from the bin with bits of kitchen towel stuffed in them, the dyson end in the other carb hole. Worked a treat for dust extraction.

I left the hump in there and just blended the area, no sharp edges, everything's nice and smooth. I'm not overly happy with the finish, it's smooth, but just a little rough under the surface from the burr. It looks worse than it is. I might go back over it with some new bits I recently purchased to do the head.

Head work has no begun, much to my neighbours dismay, the sound of a constant compressor and what sounds like a sketchy dentists drill from my air die grinder.

again with the dyson for dust extraction. Top tip, an empty cling film tube is the perfect fit into the end of the tube on the dyson and the same diameter as an inlet port! The suction is excellent and hardly any dust gets away! I've begun just by doing a little chamber polishing, just to a dull but smooth finish. 

it uses a combination of these little sanding bits that start at 120 grit and go up to 240. The other is these little fluffy abrasive bits. Extremely good and go from 120 up to 400 in a pack. The material that's coming off Is next to nothing, however I will be buretting each chamber again after I'm done to ensure they're within 0.5cc of another. I'm also just smoothing out any rough edges in the chamber. Some may say why bother, but oh well!

Chambers are nearly done, 1 more to go as I'm writing this. Next I'll be moving onto the ports. I have Neil and nicks head thread ready to read before I start the work. I'll give the exhaust ports a very gentle smooth out and not remove any material before going on to do that small cut in the inlets. I am awaiting on a manifold gasket to port match the head to my manifold but I'd memory serves me right, it's pretty spot on anyway?

Had a quote from my machine shop for the head work after this is done, unleaded seats, new valves supplied, new guides fitted, 3 angle seats cut, reface, crack test and acid dipping... 550 f*****g quid. I hate this car.

Anyway, aside from the head I'm currently traipsing through the forums on here and on tssc for threads on carb needles and springs. A lot of people reference a old triumph tune manual that states with 2l engine, head work and hot cam on hs6's to use BAE needles and red springs. I'm trying to research a good starting point, a rolling road will be needed but if I can get it most of the way there myself I'll feel better! Springs appear to have red or yellow options, again I immagine it depends on engine spec. The 2 needles I keep reading with a similar setup are BDQ and BAE, I'll keep researching more as I don't particularly feel like buying both at 25 quid a needle.

Head work incoming

Jacob

[thebrookster]

Jacob,

Personally I would not recommend "polishing" the tracts any further, a rough (almost sandpapery) finish is perfect. The finish left by a carbide burr is ideal.

If you polish the tracts, the flow becomes laminer, and this allows the flow at the edges to slow right down, allowing fuel to "drop out". A rough surface causes turbulence, which helps prevent this from happening and is beneficial for the engine.

Phil

[Nick Jones]

What Phil says! 

[Speedysix]

38 minutes ago, thebrookster said:

Jacob,

Personally I would not recommend "polishing" the tracts any further, a rough (almost sandpapery) finish is perfect. The finish left by a carbide burr is ideal.

If you polish the tracts, the flow becomes laminer, and this allows the flow at the edges to slow right down, allowing fuel to "drop out". A rough surface causes turbulence, which helps prevent this from happening and is beneficial for the engine.

Phil

Thanks Phil, I'll hold off going overboard with the smoothing! No biggy, I'll rough the surface up. I assume this applies everywhere, even the chambers?

Jacob

[JohnD]

Plus one for Phil's advice!

The chambers don't need to be polished either, but avoid any 'points' that could provide an ignition source as they will get a lot hotter than in the inlet.

Have you read David Vizard on flowing heads?  His "Theory and Practice of Cylinder Head Modification" is the Bible for many, and includes specific advice for Triumphs.  The bo ok's out of print, but second hand copies are available, and his more specific "Tuning Standard Triumphs over 1300cc"  is online at http://auskellian.com/paul/links_files/David Vizard-Tuning Standard Triumph.pdf

Good luck!

John

Edited July 9 by JohnD

[Speedysix]

Thanks all for the advice. Yes John I have seen that before and given it a brief going over, clearly brief was not enough! I have done head work before but not to the extent I'm doing now. It was more increasing the CR on my mini and utilising the engineering facilities at my university. 

I do understand the reasoning behind the rough surface and the flow properties, not sure why it didn't click before, must be the fumes from my diesel heater in the garage and getting carried away!

I have since corrected the mistake, the area that was ported out in the inlet manifold has been keyed nicely with some 60 grit paper

camera doesn't really show because of the light but it's got a coarse finish, I will do similar in the chambers but not that coarse, it'll end up like the same finish in Neil's Head thread. So far after re checking the chamber volumes, all are within 0.5cc of eachother which is an improvement over last time, I still have 2 more chambers to do.

Am I also right in saying don't touch the exhaust ports? Just remove and smooth any lumps from casting etc?

[thebrookster]

Looking good.

Yeah, you're spot on re exhaust ports. It is possible to make improvements there, but I think Neil Collingwood reckoned it was beyond a DIY tuner, requiring flow benches etc. It is also scarily easy to make things worse here as well, so when I did a head a few years back I simply smoothed things out as you suggest, and no more.

Phil

[Gt64fun]

Speedysix

My head has had professional work when we rebuilt the engine and I did latterly find that the exhaust manifold did not match the exhaust ports in some areas, meaning that the exhaust gasses would see a step as they exited the head.

So I tidied it up using the grinder and vacuum cleaner technique that you used on your inlet manifold. Every little helps!

Ian

[JohnD]

Vizard includes some advice on exhaust ports, and as Ian says, I think it's important to match the outline of the ports at the head/manifold interface.    Offer them up and you're stumped as to how to mark out any differences, so use an old gasket, or even CAD (Yes, Cardboard Aided Design) to do so. See what I mean, with an inlet manifold, on an  episode of Project Binky, 33 minutes in: 

 

Watch it all if you like, it's all good stuff!

Some say that if there is a step in the exhaust port, then the manifold should be of greater size to help prevent reversion, but me, I'd prefer a smooth transfer.   

John

Edited July 10 by JohnD

[Speedysix]

20 hours ago, thebrookster said:

Looking good.

Yeah, you're spot on re exhaust ports. It is possible to make improvements there, but I think Neil Collingwood reckoned it was beyond a DIY tuner, requiring flow benches etc. It is also scarily easy to make things worse here as well, so when I did a head a few years back I simply smoothed things out as you suggest, and no more.

Phil

Thanks Phil, yeah after reading Neil's thread in depth I am doing just that! Not quite ready for that level of work yet

[Speedysix]

9 hours ago, Gt64fun said:

Speedysix

My head has had professional work when we rebuilt the engine and I did latterly find that the exhaust manifold did not match the exhaust ports in some areas, meaning that the exhaust gasses would see a step as they exited the head.

So I tidied it up using the grinder and vacuum cleaner technique that you used on your inlet manifold. Every little helps!

Ian

I have a feeling Ian that I will soon have the same problem! I recently managed to obtain a mild steel tubular manifold so I'll be supposed to see the match to the head! 

[Speedysix]

7 hours ago, JohnD said:

Vizard includes some advice on exhaust ports, and as Ian says, I think it's important to match the outline of the ports at the head/manifold interface.    Offer them up and you're stumped as to how to mark out any differences, so use an old gasket, or even CAD (Yes, Cardboard Aided Design) to do so. See what I mean, with an inlet manifold, on an  episode of Project Binky, 33 minutes in: 

 

Watch it all if you like, it's all good stuff!

Some say that if there is a step in the exhaust port, then the manifold should be of greater size to help prevent reversion, but me, I'd prefer a smooth transfer.   

John

Thanks John, I am currently waiting for canley classics to return from their holliday so I can order a mani gasket and some head dowels and studs to check the port matching. I do have some proper engineers blue so I'm sure that'll come in handy! Yes an old cereal box usually does the job nicely. I used to follow Binky a while ago, so much work gone into one car! I'll have to give it a watch again

[Speedysix]

Started this eve, I know now why this area gets cut, I can feel the step that is getting taken out. Made a depth gauge very similar to Nick and Neil, commenced the cut with the carbide and blended the area, then hit it with the ball grind stone just like Nick did, worked perfectly for blending the shape and radius.

Hard to get decent focus with the lighting in here, looks a bit shabby but I didn't want to remove too much material or undercut the seat. I finished with 80 grit on the little sanding wheels to smooth the bumps out and give the surface that rough finish.

The inlet tracts i simply ran the ball stone down them to remove any lumps and key the surface. Not the best finish again but it sounds like this is what I'd needed?

Also in every inlet, just after the opening of the inlet port, there is a hump, about 5mm in on the top and the bottom, is this a maching/casting thing or is it there for a reason,this is the best photo I could get

it almost looks like when the heads are cast, the port opening is machined but only by about 5mm deep, is this a step i want to be smoothing out?

Jacob 

[Nick Jones]

1 hour ago, Speedysix said:

it almost looks like when the heads are cast, the port opening is machined but only by about 5mm deep, is this a step i want to be smoothing out?

I think that’s actually what it is. Yes, I smooth it out.

Decent head torch can help a lot with visibility while grinding.

[JohnD]

 Agree with Nick, and with the headlight idea.

I have an electric screwdriver by Bosch, that has a little LED under the chuck that illuminates the work rather well.     Could an LED and battery be taped to your die grinder?     Never tried that!

John

[Speedysix]

Yes I thought so! Back on the head today so I'll smooth out those ridges!

Do you all think I work in the dark? my head torch is so bright it reflects off the head surface and blinds me almost on the mid setting

I end up with my full face 3m mask and the head torch on top, it runs on a pack at the back with a couple of those 18650 cells inside so lasts a very long time between charges. Sometimes I'll have either my ear defenders on or headphones in whilst grinding

Brilliant bit of kit, think it was about 15 quid which is brilliant! It also has a red light function if youre planning any night ops. 

[Speedysix]

Thats the ports done! The only thing left is the port matching which won't get done until next week when my canley order arrives. Then that'll be the head done and ready to go to the machine shop. 

Re checked the head properly this time and came back with an average of 34.08, this yields a CR of 9.38, I will work out how much needs to be shaved off to get to the desired figure.

Whilst I'm waiting, I will be turning my attention to the air filter/box and carb damper spring. The needles from tt manual lists with a flowed head, k&n, and hot cam to run BAE on hs6's, I feel this sounds about right for me as a very good starting point? Damper springs are a choice of 2, I've seen some people complain about yellow ones causing hesitation on engines with similar setups and some running red, this is one of those questions that can't really be answered but a nudge of info would be greatly appreciated.

Lastly is the air filters. Before I ran crappy pancake air filters. Useless. This time I am purchasing Stub stacks for the hs6 from MED, their ones seem to be the best designed at the moment. Then we come to filters. I think I'm right in saying a cold air feed will surpass the performance of a k&n, which is why I'm tempted to use a standard air box with the pipes that run to the front of the rad. Only trouble is hs6's. Can anyone verify if one I'm right in this chain of thought, and two if it's easier to modify a gt6 box or see if a tr6 one fits?