Alloy inlet studs?

[samir]

Hi there Iv ordered a alloy inlet manifold which I will be fitting on the weekend, however I forgot to order the blanking nut, could I use anything else to blank the hole off like a nut from a hardware store? Also the studs that stick out from the carb side Arnt present. Where do I get the screws so that the carb can be bolted onto it? Sorry if the answers are obvious, I'm still a learner. Any help will be appreciated

Regards

Sam

[bmcecosse]

I don't understand the 'blanking nut' idea......do you mean the alloy inlet has a port for a vacuum servo? If so - no - you won't find anything (and certainly not a 'nut' ) in a hardware store...... I think it is 5/8" UNF.... You will remove the studs from the old cast manifold - and fit them to the new manifold. What will you do for an exhaust??

[samir]

Hi it's a nut that's supposed to blank off the hole on the manifold, I think, it's designed if your car has a brake servo something like that, I think it's a 22mm nut. In fact it's a bolt not a nut lol. I will
Be angle grinding the original inlet off the exhaust manifold, it's because iv got a stainless steel exhaust system so I want to keep that. Will I need the optimising timing and air/fuel ratio with the new inlet?

[bmcecosse]

Of course you will! But what carb are you using with the new inlet manifold? It won't take the standard HS2 carb...... The blanking plug is certainly NOT 22mm........

[samir]

Iv already installed a hs4 carb. I did that with your help before about 2 months ago. I want to cut the inlet manifold from the exhaust manifold and use my stainless steel exhaust system. The hole is on the left hand side of the manifold I attached. Could any bolt fit ?[frame][/frame]

[bmcecosse]

Not 'any' bolt - it will need a 5/8"UNF plug. Sorry - I had forgotten you are on an HS4. Interesting to hear what improvement changing the manifold makes. You should cut the exhaust off a standard Minor manifold - not the rather better manifold you have with the HS4. Make sure you cut into the inlet manifold - and then tidy up the rump left on the exhaust.

[Declan_Burns]

Like this.
Regards
Declan[frame][/frame]

[samir]

Great help one again i fitted to today finished about half hour ago. Looks and sound nice, but first when warmed up with no choke it would kind of die, I then adjusted the idle speed and got that set ( I could be wrong), it was fine after that then drove around and the revs seemed high and when acclerating I would let go off the pedal and it would still feel like it's at high revs but slowly drop, not enough though to call normal. The exhaust sounds like a few gunshots are being let off inside on idle aswell.

[bmcecosse]

Sticking throttle cable? How did you plug the servo hole? Is the carb sitting with the float chamber absolutely vertical? And - look for air leaks - is the manifold held TIGHT against the head? Are you sure the inlet manifold has clearance off the exhaust - otherwise it may be held slightly 'tipped up' causing an air leak at the manifold/head interface.

[GBond]

From that picture it doesn't appear to be a servo hole at all but rather a hole that goes to the water passage in the manifold perhaps for a thermostat.

If that is the case it wouldn't even need to be plugged unless you're circulating coolant in the manifold.

[philthehill]

The 5/8" hole is in the No: 3/4 inlet tract.
The water tube is just a straight through pipe.
The blanking plug is available from Mini Spares Pt No: ADP210 £2.88 inc VAT plus P&P. Use washer 1B3664 also available from Mini Spares. You can also use blanking plug Pt No: 5-8UNF also available from Mini Spares.

[samir]

Thanks guys. Everything all seems held in place. My idle speed is just so high and when I adjust it it's either too low as if it's about die or too high . When braking and putting the car into neutral and then downshifting the revs increase which is making it hard to drive, if I put the car in second, the car will just keep running without any throttle pressure. Also sometimes when stood still with no choke I will rev it and as the revs slowly come down it will stArt to die until I give a little more revs to keep it running. I know if I get it set right I will see the difference in the new inlet mani but for now it's become a bit of a problem.

[bmcecosse]

You haven't answered about sticking throttle cable? Is there an adequate return spring? And is there a GAP between the inlet manifold - and the (now cut off) exhaust manifold? Is the carb piston free to rise - and does it fall back with a nice clunk? Have you set up the idle mixture? And - how have you plugged the servo hole??

[katy]

how have you plugged the servo hole??

That was my thought also, probably sucking air in there.

[philthehill]

I would suggest that if the 5/8" blanking plug has not been fitted it would run really awful; much worse than described above.
If the hole has been plugged with a non standard plug, yes there may be a weakening of the mixture as air is sucked past the ill fitting plug. The correct 5/8" blanking plug must be fitted.

[bmcecosse]

Just a thought....is a spark plug 5/8" UNF....?

[philthehill]

No
The blanking plugs advertised (Part No: 5-8UNF) are 5/8" UNF x 18TPI (I purchased several to use in blanking the oil galleries).
The spark plug is 14mm x 20TPI.
Have checked both the 14mm spark plug and manifold blanking plug with a thread gauge.
I have just also removed a blanking plug from an alloy manifold and the thread used is 5/8" x 16TPI Unified National Special (UNS). I believe that this is the correct thread for the manifold blanking plug.
So there may be variations in plugs used to blank holes in inlet manifolds.

[bmcecosse]

It was just a thought......thinking back, I suspect I tried a spark plug many moons ago...and failed. Strange that a 'metric' thread would have 'tpi' - is that just a 'nearness' ?

[philthehill]

bmc
A good question well put.
The three thread gauges I have
Whitworth - Threads per inch.
UNF - Threads per inch.
Metric - Gives the pitch from i.e. 0.5mm - 1.75mm.
As regards the metric TPI it is a generalisation (nearness) term as pitch is the correct term when describing metric threads.
A 14mm (13.5mm actual) spark plug should be deemed as being 14mm x 1.25mm pitch.

5/8" Whitworth is 11 TPI.
5/8" UNF is 18 TPI.
5/8" BSP is 14 TPI.
5/8" BSF is 14 TPI.
5/8" UNC is 11 TPI,
5/8" (16mm) ISO Fine in mm is 1.50 pitch.. ISO Coarse in mm is 2.00 pitch.
5/8" UNS is 16 TPI.

Have just been reading my copy of the British Standard for Unified Threads & how the British Standard for UNC/UNF & UNS came about after WW2. The designations adopted were the nominal diameter and the Threads Per Inch (TPI).
Interesting reading. Well someone has to read it!!!!

[bmcecosse]

" Have just been reading my copy of the British Standard for Unified Threads & how the British Standard for UNC/UNF & UNS came about after WW2. " A quiet day then Phil ......... I do know that metric are expressed as pitch - I was just asking a 'leading' question...