V8 manifolds - downpipes won't fit

M

Madalicesdad

New Member
I fitted a complete exhaust system (from JRWadhams) about 2 1/2 years ago. I had problems getting the down pipes to meet the manifold but put it down to my haste to complete the job (carried out outside in -4 deg temperatures), and needing to get it back on the road ASAP I botched it with lots of paste.
Now i've had to change the head gaskets, I realise its nothing to do with my haste - there is no way that the pipes will meet the manifolds and the pipe that runs under the sump is in contact with it.

My thought are:
Is there a different manifold design for different vehicle applications? (i don't know if the engine is the original one)
Are the JRW exhausts correctly made?

Any clues?
It's a 1976 3500 auto.

Mike
 
Hi Mike,

I had a similar problem. I live outside the UK so I could not just drop in to Goughs to have the problem sorted. P D Gough eventually replaced the the left and right downpipes free of charge.

P D Gough confirmed that their design dimension for the length for the left and right downpipes (bottom of exhaust flange to the centreline of the crossover pipe under the sump) as 257mm. The actual lengths of these two sections of pipe that they supplied to me were 205mm on the driver’s side, and 220mm on the passenger side. These are significant manufacturing errors --- 52mm and 37mm. If the pipes had been supplied at the correct design dimension of 257mm then I would have 57mm clearance under the sump instead of the 5mm that I had, and I would have been able to fit a U-clamp on the slip joint under the sump.

Measure the dimension from the bottom face of the cast iron exhaust manifold on the driver's side to the centreline of the hoizontal section of pipe that passes under the sump. Measure also the same dimension on the left side to the centreline of the branch that joins the crossover pipe from the right side. These dimensions should be same on each side and ideally 257mm.

Let me know what you find.
 
I'll measure them tonight, but I'm in no doubt they are too short! The pipes are long out of warranty so what is the bext work around?

My thoughts are to drill out the studs on the manifolds (several are sheared anyway) to give a clearance for long pieces of 8mm threaded bar and clamp a piece of suitable diameter steel pipe in the gap to make up the difference, sealed with lots of paste.

It maybe another bodge, but the car has to work for its living and I need it back on the road. any other fixes/solutions greatly received!

Mike
 
P D Gough give a lifetime transferrable guarantee on the stainless steel exhausts. If they made the pipes shorter than their own design length then they have no option other that changing the incorrect parts free of charge. Although a lot of correspondence passed between Goughs and myself before they conceded, it's to their credit that they provided me with new left and right downpipe sections at no cost.
 
My system is mild steel and from Wadhams. I'll give them a call but don't hold out much hope 2 1/2 years on.

Cheers
Mike
 
I note from the JRW website there are long and short down pipes. I assume these are affectively LH and RH, or do they really come in two different lengths?
irrespective of that, at £75 +VAT for long pipes, I'm happy to bodge it!

Mike
 
It's difficult to measure exactly, but I reckon (drivers side) the distance from the end of the down pipe to the centreline of the horizontal pipe is about 220, definitely no more than 230mm. The gap between the manifold and the pipe is approx 10mm, but the horizontal pipe is hard against the sump with no room for any clamp.
I remember when fitting it I had to cut a fair bit off the horizontal part of the pipe to get the width between the two down pipes correct. Perhaps the pipe was the right length but bent in the wrong place during manufacture?
A semi permanent fix using longer studs, a 10mm length of scaffold pole and lots of paste is on the cards...

Mike
 
Short of cutting and welding in an extra bit of pipe, I think your long stud & pipe solution is a winner.

Richard
 
These are the "olives" that go between each exhaust section. According to my parts book - there are no olives between the down pipe and the manifold. However the "top" of the pipe should be "shaped"
 
Sorted. I tapped the manifolds out to M8, inserted 60mm lengths of M8 threaded bar and by tightening the nuts sequentially, pulled the down pipes into place (with lots of sealant).

It's very close to (possibly touching) the sump, so once I've got the engine back together and running again, I'll have to adjust the pipe runs to see if it can be improved.

Mike
 
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