186S head info

[reddo]

Hi.all ...
Just done a swap with my eldest son.
I gave him my unregistered 1971 triumph Bonneville bike .. in exchange for a HR sedan rego to september.disk brake front. 3:08 'diff ( guess where the diff is heading .
It has a genuine 186s motor with headers and dual,throat carb etc.( may well end up in the FB Van too.... oops i gave ya the answewr to question one.. )
It has a "miss"in it .
I have replaced the plugs.. leads... checked rocker adjustment ..dizzy cap for cracks or shorting...swapped the dizzy and leads out of the panno for a trial.....done a compression test with all pots returning around 175PSI.

I can drop either No:5 or No: 6 plug lead off and it makes no difference to the idle
Begining to think it has a head gasket leak between 5 and 6.... but cant explain the good compression in those two pots.
They should be down on squish if that was the case.

Gunna whip the head off it next weekend and have a looksee...
Which brings me to the title of this topic...
I have a couple of stock 186 and 179 heads kicking around the shed. Is there anything special about a 186 Head??
Bigger ports???? larger valves... anything at all??
Obviuosly if its just a gasket i can replace it . need to have a good look at the head first though.

Its over to you guys. Your thoughts
A: why it is missing
B: 186S head differences to a stocker.???
Yours in anticpation
Reddo

[thropzed]

Rekit the carbie!
Cheers Theo Z.....................

[thropzed]

check ya firing order so ya leads are on the right plugs!
Cheers Theo Z................

[Mick]

no differance in the heads there's only high comp or low comp identified by a H or an L cast on the left rear of the head but if they are off you can see that one has an open combustion chamber and the other closed (smaller) then of coarse there's the sh!tty non ajustable rocker heads

did hear a guy at the swap yesterday had some cleveland heads for sale and when asked were they open chamber or closed he answered ahh both

[reddo]

Yo..
Carb is perfect.
leads are on the right plugs.
153624.
Car pulls like a train when on the road. just has a stutter down low and.. as i said. pulling either 5 or 6 lead off makes no difference to the idle.
Pull any of the others off and it rattles and shakes.

Only other thing i can think of is worn cam lobes. Its a reco Gem motor so i seriuosly doubt that is the issue.

Cheers
Reddo

[newman]

This might sound way out of left field but swap the PCV valve out for a new one or one from a good running motor, I had a mystery miss like you are describing on a 179 and I was trying everything before resorting to lifting the head. Last thing I tried was the pcv valve and it resolved the mystery miss, worth a try before taking the head off.

Mick

[Trev]

A leaky butterfly shaft in the carby can cause a miss down low.

[reddo]

Yeah ..
Thanks for all the tips guys.
Carb is perfect. no signs of fuel or air leaks.
I am going to try a new PCV valve this weekend.
Had a call from FB mad who also suggested that the diaphram / rubber in the booster could have a hole in it allowing extra air back to the inlet manifold . the vacumn pick up outlet is in betwwen 5 and 6. So i disconnected the booster and plugged off the manifold hole...... problem is still there.

Pulling either plug lead off makes absolutely no difference to the idle... so yeah .. will try the pvc valve shortly.
Hellavalot quicker / cheaper than pulling the head off..
I'll get back to yas shortly.

Reddo

[Trev]

Have you got a spark from either 5 or 6?

[roto]

Manifold gasket sucking air on 5 and 6
roto

[reddo]

Hi Roto and Trev.
Have perfect spark on both plugs 5 and 6
Have squirted soapy water across top of inlet and exhaust right along the head ... no bubbles or leaks.
Tensioned all nuts holding manifolds.
Tightened all screws on carby as well as checked carb to manifold nuts etc.....
checked mixture and leaned off a tad.

Havent swapped the pcv valve yet....do it saturday... fingers crossed.

Been sidetracked a bit..... fitting electronic dizzy to FB van .. and......

C4 auto in F100 not kicking up to drive when cold.... sticky valve and hard rubber seals....
Lets not talk F%rd.

Cheers
Reddo

[mickhrt]

Reddo try spraying crc around carbie and manifold if it picks up revs you know theres a leak
cheers Mick

[reddo]

Hi Mick..
Yup... been there done that..

If it was a leak at the carb it would effect all of the cylinders.
Its just 5 and 6 that are giving me grief.
Its sunday morning and todays plan of attack is to swap the 2 plugs from 5 and 6 for 1 and 2 to see if there is any difference.
I have replaced all 6 plugs and 6 leads ... even used the distributor and leads out of the FB ( red motor).
No difference.
Next will be drop the rocker cover off and go over the rockers while its idling.
Pay special attention on 5 and 6 inlet and exhaust .
If that doesnt cure it i will pull the 4 push rods up out of 5 and 6 and check they arent bent....
If they are OK .... well .... then the head comes off for a looksee....

Reddo

[reddo]

2nd edition for sunday 27th...
Tried everything in my previous post. No luck....
though something might be blocking the inlet manifold to 5 and 6....removed inlet manifold.... all clear in thge manifold.. nothing in the inlet ports on the head>..

Head is now off the motor.....
Noticed green coolant running out of last exhaust stud bolt hole when i was removing the manifold...
http://i10.photobucket.com/albums/a150/ ... 280371.jpg
Then there was green juice on the back two headbolts when i was removing them....

Got the head off....
http://i10.photobucket.com/albums/a150/ ... 280372.jpg
Coupla white valves.....hmmmmmmm
lets have a look at the block......
http://i10.photobucket.com/albums/a150/ ... 280374.jpg

OOOOOOOOOOOOOOOOOOOOOooooooooooooooooooooooooooooooooooooo...........
http://i10.photobucket.com/albums/a150/ ... 280375.jpg

aint too concerned about the bore being full of juice.. it got there as i was taking trhe head off.
Wound the piston to TDC and wiped it dry.... then wound it back to BDC no msigns of cracks or corrosion in the bore.
The problem i see is that when i stick my finger in either of the back 2 teardrop shaped water jackets and push up and down the water level in the back two .. and the first of the head stud bolt holes on the manifold side goes up and down

Soooo.. corrosion between head bolt holes, manifold bolt hole and water jacket.

But that doesnt explain the white valves... which usually is caused by water entering the combustion chamber or running lean.
Cant see and "blow holes "in the head gasket allowing water from 5 across to 6.. and if it was running lean all the chambers would be lean/ whitish
second thought...water might be getting into both chambers via a cracked head??
If this was the case the whole chamber would be effected not just the valves...

Before i pulled the head off. i pulled a plug out and started the motor... no signs of water coming out of the plug hole. There has been no evidence of hydraulic locking on start up from cold or at any oher time??

Where to from here??

[roto]

G'day Reddo,
Here's another guess.
There's a couple of small welsh plugs in the side of the head under the manifold gasket and maybe it's leaking between 5 and 6 cylinders.
Regards roto.