Jump to content

manifold leaks studs and why


Pete Lewis

Recommended Posts

There's been some good topics in the twiddle day post following problems on the day  and subsequent problem with one of my  a  local cars

anglefire had a gasket and  problem  and this wandered about with thoughts and how to use squirt cans and oil or cleaners to see if the joints sucked air 

which they did, my local car ran like a pig at idle and   despite much twiddling lead to the similar fault.

what made this worse than let say normal was a 421 had been fitted using an old gasket,  this happens to be a 1500 spitty, on removal it was clear the studs and manifold nuts were seriously seized, so whilst the nuts appeared to be tight , they did not clap the faces , once the stud reached it end of thread

the nut appears very tight , when its not , none of the studs could be reclaimed all   sheared on attempts to remove the nut .

so lesson is if the manifold leaks but the fixings appear to be  b...dy  tight .....they may not be doing anything  meaningful at the  clamp face 

using an already compress gasket exasperated a pre existing problem , we got there in the end but this followed a few desperate days of Twiddling the basics before the strong tea and a head scratch

Pete and Ray

 

 

 

Link to comment
Share on other sites

Recommend use of bronze (NOT brass!) nuts for exhaust manifold studs.   They will not seize on the studs. Used to be available from Halfords!   But are off eBay.

Alternative, not as good, coppper grease to lubricate steel nuts.

John

Link to comment
Share on other sites

I meant to file a nut to see what they were , but in the bin, certainly been   in a poor   aged  state   ...been    stuck for years  until we got them ,  

and you never have a stock of spare studs the right thread or lengths,  some replaced with copper'd  setscrews ...needs must when its in bits 

Pete

Link to comment
Share on other sites

Sorry I was not clear  the nut and its stud came out of the block easy,  there was a chance of spliting the nut to reclaim a stud  but didnt try that... easy to be clever afterwards

But a good soak and with  stud in a vice , a pull on a ratchet just sheared the stud

So none of them sheared in the head    , whilst some setscrews were used to effect a repair you need to make sure they are correct length or it can bottom out or even punch into the water jacket

Its the time taken to unravel previous cock ups takes up the day and you wonder where the time has gone

Never mind the cups of tea.

Pete

Link to comment
Share on other sites

Hi

Bronze nuts are not that easily available. The last lot I made in the lathe using some hex P-B I had from year dot; that was for a Mitsubishi Shogun of 1990 vintage. I assume the Nuts are 3/8 or 7/16?. Likely AF or UNF/UNC?.  Looking at some of the pictures, getting the clamping fingers parallel has to be a bit of a challenge too. I suspect that if they are too far out of kilter some of the clamping effort is lost?.

Pete

Link to comment
Share on other sites

34 minutes ago, Pete Lewis said:

Without the raised dimples they might pitch rather than pressure on the faces

That was the issue with some of the dumbells on mine - before I swapped them out with the ones off my old engine. Due to the difference in heights between the exhaust and inlet flanges, they tended it bear on the exhaust flange more. 

Link to comment
Share on other sites

Hi

Maybe a tiny bead of judiciously placed weld material might "square" things up?. This assumes they are steel not iron.

3/8 x 24 UNF. sounds about right. It is also not uncommon to find the thread in the "Head" casting, is coarse, and the external is a fine thread either!. I will have a check as the manifold(s) on my engine will have to come off anyway. I want to check the condition of the head and valves. one (No 2) I think it is, was showing lower than the others when I cobbled up a comp test some time back. I wrote the results down somewhere. Interestingly, I have a recently discovered invoice from H-Q for an "unleaded" head!, circa late 80`s?. The kit of parts, which was this car, came with a huge pile of "stuff", bills, MOT`s, even copies of letters to suppliers!.

Pete

Link to comment
Share on other sites

the local car with the problems started with a 421 being fitted on the 'old' gasket so thats a steel +alloy mix as many are these days

its all down to good dimples and nuts that screw !!!     if your nuts are seized expect  some leaks    Hmmm !!!!

pete

 

 

Link to comment
Share on other sites

5 hours ago, PeteH said:

Hi

Maybe a tiny bead of judiciously placed weld material might "square" things up?. This assumes they are steel not iron.

Were you refering to the manifold clamps, it would certainly even up the force between the exhaust and inlet if a small weld was added to one dimple only and fettled to sit level.

Aftermarket manifolds often suffer from having an increased flange thickness. On BMC A and B series engines you have to resort to fabricating stepped washers to take up the difference!

David

 

Link to comment
Share on other sites

6 hours ago, PeteH said:

Hi

Maybe a tiny bead of judiciously placed weld material might "square" things up?. This assumes they are steel not iron.

3/8 x 24 UNF. sounds about right. It is also not uncommon to find the thread in the "Head" casting, is coarse, and the external is a fine thread either!. I will have a check as the manifold(s) on my engine will have to come off anyway. I want to check the condition of the head and valves. one (No 2) I think it is, was showing lower than the others when I cobbled up a comp test some time back. I wrote the results down somewhere. Interestingly, I have a recently discovered invoice from H-Q for an "unleaded" head!, circa late 80`s?. The kit of parts, which was this car, came with a huge pile of "stuff", bills, MOT`s, even copies of letters to suppliers!.

Pete

Hi

Further to the foregoing. Ref: manifold`s. I just checked mine, Cast Iron Exhaust and Alloy inlet, so pretty standard, the nuts are all "free", so that`s a bonus. Inc the ones under the Exhaust!, Ran the tap down a Nut to check they are 3/8" UNF. I get the impression there was some work done on the engine. (it was sorned end of 2015), in the late 90`s by the look of the paperwork. The engine # is GK1315HE. Is the HE significant?. The Head was Exchanged for unleaded 22/06/1999. The Carburettor also received an overhaul about he same time.

I too have noticed that in photo`s there is often a significant difference especially when 421 after-market Exh: Branches are involved.

 

Pete

Edited by PeteH
Additional text.
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...