Just bought a Triumph GT6.... and I think I need a new head gasket :( (inc. pics!)

[Pete Lewis]

adding clamps the 3-1 collector is a  often used method to seal the blasted thing 

its a loose fit to allow the pipe expansion but they leak like a sieve, noisy and  most annoying awful bit of kit 

think Jigsaw sold pheonix  same as club shop and they made this leaky collector 

had this on the 1600 and it was what i called the Nick solution as he developed the idea  

as for the butterfly clamps just a long extension and finger fumbling works 

i got rid of the wheel barrow pipes  sounded more like a hair drier used a single semi sports 

and that was crisp and on song  for a great note 

Pete

 

[HeebieGeebie]

I have a question for you knowledgable people, what are the benefits of the 6-3-1 vs the 6-2-1?

I've ordered the Phoenix 6-3-1 from Rimmers, but i'm questioning that decision now. The 6-2-1 from the Club Shop is considerably cheaper, looks simpler/potentially easier to install and less points of potential failure. In my mind 6-2-1 seems like it would better for performance as well but i must be wrong otherwise why would they sell the 6-3-1.

Would love to hear your thoughts!

[Pete Lewis]

none of them do much until you pass 4500 rpm  and the 621 has always been said to be useless

Ive not used a 621  so cant say , many never rev it enough for any to work  certainly the 631 you can hear it 

come on song as the revs build  the exhaust has a song of its own 

Danny Hopkins of Practical classics drove my Vit6 back from Stafford like he stole it and 

when we got home he said  wow!  i was not expecting that 

Pete

[Clive]

I have seen rolling road figures. 6>2>1 dies nothing significant. The old "mike the pipe" 6>3>1 are excellent giving a nice torque increase, the phoenix versions are a poor copy, unequal length primaries etc and often a poor fit. 

A good "all round" option is a TR6 cast iron manifold, but requires a custom downpipe. Fits, simple, better than the std GT6 cast manifold. 

But you may be best off taking yours to an exhaust specialist to fettle. 

[Steve P]

I was lucky enough to find an original MTP 6-3-1 for my 2.5 Vitesse,that is a thing of beauty.I have a Saloon version knocking about somewhere too.

I bit the bullet and took mine to Matt Simpson,ex BTCC who builds race systems at his place near me.

He made and fitted a nice stainless system from the manifold back with a single box up under the rear outrigger.

Don`t know how much it contributed but the engine made 172Bhp on the dyno and is plenty quick on the road.

Moss used to do a fairly decent copy under the Triumphtune name. Not sure now ,only in mild steel though if i remember correctly.

Steve

[Colin Lindsay]

I'll agree, they don't fit first time.... this one (a Phoenix exhaust) was removed for fettling when my optimism about a 'fit and forget' proved foolhardy...

 

[JohnD]

HG,

The straight six engine has the best balance of any other layout, unless you get to exotics like V12s!     This because it consists of two, three-cylinder engines, running with ignition at 120 degrees, but with each 360 degrees out of phase.   Each three-cylinder unit is well balanced, but with a longitudinal moment, which together cancels out.    No.1 is at TDC on the firing stroke when No.6 is also at TDC, but 'on the overlap', at the end of the exhaust and beginning of the intake strokes.    Nos. 2 and 5, and 3 and 4, do the same.     So if you join their exhaust primaries in that way, then the junction  of each pair 'sees' the exhaust impulses exactly 360 degrees apart.   At a certain engine speed the pressure wave from the exhaust valve is  reflected back up the other primary, as a negative wave, arriving just as the other  exhaust valve opens.  This negative pressure assists extraction of the exhaust gases, so this style of manifold is called an 'extractor'.     

From the above explanation, you can see why a 6-2-1 cannot ever do the same!    That just joins together the three primaries from the basic three cylinder engine.   The pressure waves arrive at equal intervals, but in an order that prevents one affecting the next in a preferential manner,
It is essential that the primaries are equal in  length to act as an extractor.    This graph shows how to choose that length to get an extractor effect in any rev range.  Triumph 6-3-1s usually go for about 43mm (17"), and act in the 4-5K rev range.

John

[NonMember]

32 minutes ago, JohnD said:

From the above explanation, you can see why a 6-2-1 cannot ever do the same! 

Actually I think it needs a bit more of the physics before you can make that assertion.

The primaries of a 6-2-1 can give some benefit, from the same mechanism described for paired primaries, but only if the exhaust valve duration is short, and at a different speed. The reflected (inverted) pressure wave still travels up the other primaries, albeit at half the strength because it's split. The problem is one half of it then hits a closed valve, causing it to reflect back again (no inversion this time, so still a negative pulse). On arrival at the junction, if you're at the magic "tuned" speed, it then interferes with the positive pulse you want to reflect.

If the exhaust valve opening period is a full 240 degrees or more (which our engines are) then you also get the next pulse arriving just as the previous one ends, and hence very much less actual pulsing at the critical junction point. So all in all, very little help there.

[HeebieGeebie]

JohnD/NonMember, very interesting reading thanks! I'll stick with what i've ordered.

So project today was painting the intake manifold and I also wanted to test the fuel pump (Facet Universal Pump), it took 38 seconds to fill 100ml of fuel, and it wasn't a consistent flow. I think it might be down to the position of the pump, it is quite high up, in line with the top of the fuel tank. I think i should relocate the pump. This test was just running from battery power.

[Clive]

100ml in 38 seconds. That is a a gallon in just under 1/2 hour. At 70mph you need to be doing 35mpg, at 100 50mpg to keep up with demand, obviously not enough flow.

Check all filters etc as well as getting the pump below the tank. I am sure there is a filter built into a facet, that needs checking too. But a facet silvertop pump start at 18gallons/hr, yours is about 2. The last thing you need is the engine running lean at high rpm.

[HeebieGeebie]

I'm back with more updates. Still waiting for the exhuast from rimmers. In the meantime i did a couple of things; fitted T-Piece Fuel Unions for the Webers, did a Compression Test, Inspected cylinders with a borescope.

I did the compression test cold since i've removed the exhaust and intake. Based on my rough interpretation of the gauge the results were:

1. 185
2. 180
3. 179 (169 first try)
4. 180
5. 180
6. 171 (174 first try)

It was bit low in 3 and 6, so i re-tested them. The results seem acceptable to me.

Regarding the borescope inspection, I know there's supposed to be honing marks in the cylinders, but the scoring looks pretty deep, what do you guys think?

[Nick Jones]

Good compressions.

Borescope looks ok too - as far as quality allows.  IMO the light is picking up on the honing lines, highlighting them.

 

Nick

 

 

[Pete Lewis]

i was thinking its been   glaze busted with some overcoarse hand held process not the figure of 8 random 

makes of a honing kit  has this engine had a DIY  re ring at some time 

agree reflection upsets the image but none proves very much 

does this beast happen to have an external rocker oil  feed fitted ????

makes a good way of producing smoke and smells as the excess oil is burnt off 

Pete

 

[HeebieGeebie]

Hi all, another update after a busy month.

@Pete Lewis yes, it looks like it has had the external rocker feed done. See pics below.

My exhaust finally arrived from rimmers and I also completely disassembled and cleaned the carbs using an ultrasonic cleaner. I bought some weber service kits and refreshed all gaskets and seals.

The exhaust port openings on the new manifold are much smaller than my current one; 25x32mm vs 30x36mm on the old one. I hope this doesn't affect performance.

[Pete Lewis]

So either remove the feed (spawn of satan )   as this can vastly over oil the rocker zone 

 or remove the banjo bolt and plug it with a threaded bit of a bolt with a 0.5mm hole drilled in to restrict

the uncontrolled excessive oil flow to the head 

Pete

[Wagger]

Those manifolds do not look adequate. Have you tried the fitment? The cast one looks like a large port exhaust from a 2.5 litre. You need to get a load of gas out with triple carbs.

Individual branches can work better, but still should not impede the flow at the port. Those definitely will.

[Ian Foster]

I would be inclined to check that the manifold ports match the head, either by using the new gasket (may not be perfect) or making a rubbing with thin card.

My original cast manifold needed some fettling to match my reworked head.

Ian 

[Wagger]

I do find it odd that classic car owners want stainless steel exhaust manifolds at a time when many owners of 'Moderns' are replacing cracked stainless manifolds with cast iron ones.

Cast iron absorbs the under bonnet sounds so you hear the tailpipe(s) more.

[johny]

Dont think its wanting stainless so much (although maybe theres a bling factor) as wanting separate long branches which of course you cant get in cast iron...

[Pete Lewis]

agree very few will tell you that tubular is noisy  as the pipes ping like a bell 

you get all the detonation racket not heard with a cast unit 

Pete

[Iain T]

I bought my car with a Phoenix 631 and wheelbarrow pipes. Sounds very nice outside but 'ell of a racket inside up to 3000rpm when it then calms down. In preference I think I might have preferred a cast manifold with sports exhaust. 

Iain 

[HeebieGeebie]

Back again after another busy few weeks, was away from home visiting the missus' family in Bulgaria.

I'm having a nightmare with this blooming exhaust manifold. Whilst i was away i got a local metal worker to open up the exhaust ports on the new one. At the same time i asked him if he could try and weld up the crack in the old one so i have options.

I spent tuesday evening wrapping the new manifold in DEI exhaust wrap. Didn't do the best job but it'll do. Then i went to fit the new exhaust and put everything back together, and discovered that my intake runners clash with the flange on the new exhaust and i dont have a dremmel or the appropriate tools to modify it. No bother, i'll just fit the old repaired manifold back on instead, it looks a better design anyway. So i cleaned up the whole thing with a wire brush and painted it a nice silver with high temp paint, got it looking good. Went to fit it and it no longer fits. Where it has been welded, the pipes have pulled together a few milimeters and no longer fit on the studs. What a waste of time.

If anyone has any suggestions im all ears.

[Pete Lewis]

think you have just found the joys of tubular manifolds    there two things with them

they fit like a glove

or they dont fit at all

its cut weld grind  i fear  there's no easy way 

they can test your patience 

Pete

 

[Colin Lindsay]

Is that a Phoenix exhaust? Looks like the one I had.

You don't need a Dremel, an angle grinder will work just as well on that thickness of metal. 

[JohnD]

HG, 

Welding distorted the primaries?  'Distort' it back then!

Length threaded rod, couple of custom brackets, wind it back to the right spacing. Plus a bit so that it won't just spring back!

John