I decided to have a go at sorting out the heat issue with the manifold and carbs. If you research the web you will find numerous solutions for blocking the exhaust crossover passage in the inlet manifold including:
- Melting pistons and pouring it into the cavity
- Filling the cavity with plaster of paris
- Filling the cavity with furnace cement
- Filling the cavity with aluminium foil, packing it in tight with a stick
- Using various materials to block the entrance at the gasket including pieces from soda and soup cans (it seems the thinner materials burn through)
I decided to use some stainless shim I had in the shed. I measured the thickness of a new gasket including the raised ridge, and it measured just under 0.040″. I had some 0.035″ stainless in the shed, so it should do the job perfectly. I started by cutting out two pieces 29mm x 44mm.
Next I cut the gasket to enable me to insert the stainless pieces. Not an easy task as the gaskets are a little delicate, but careful persistence got me there.
When finished, I had two gaskets with block off plates.
I removed everything near or connected to the carbs, and then removed them.
I could then proceed to remove the manifold – I forgot how heavy this lump is! I could see that one of the exhaust passages had been leaking a little at the lower edge so I filed the manifold to take a couple of thou off of the top edge to try and even it up. I cleaned up where the paint had burnt, and then primed and painted it with VHT Burnt Copper Engine paint. Once complete, I left it in the sun to cure.
Turning my attention to the engine I cleaned up the gasket surface. I then painted the inlet port areas of the gasket with copper sealant and installed them in place. I then inserted the stainless block off plates, sealing them with a little bit of RTV silicone.
I then reinstalled the manifold making sure it was settled in, however it was hard to tell the natural position because the copper cement is sticky.
The centre carb went back on first.
End carbs on next and it is starting to look complete again.
While the carbs were off I bought some brass fittings to improve the installation of the PCV hose and also the vacuum hose for the brake booster. Space is tight behine the carbs as I don’t have a Tri Power distributor, but it is not impossible. The first two pics show the vacuum take off from the rear carby using a 45 degree adapter. I also replaced the hose between the booster and one way valve. I actually made it shorter and routed it under the wiper motor and around the back of the engine.
For the PCV, I used a couple of adapters to make a U shaped fitting which eliminated a bend for the hose and made it easy to bring the hose forward and under the manifold.
All that was left to do was start the car to make sure it was all OK. The engine started, but it sounded like it was running on 6 cylinders. I started it numerous times to see if it was wet plugs, but no success – it is rarely that easy. I re-tightened the manifold and tried again to no avail. I spent the next hour checking the manifold and carbs, as well as spark plug leads and other things which I had removed.
After coming to the end of my wisdom, I was pretty well convinced that I had made a mistake with the thickness of the stainless plates, and was seeing visions of me removing the manifold again. Dread of dreads!
I went through one final check of the carb linkages hoping I could find something wrong, and noticed the linkage which joins the front to the rear carby seemed to have some load on it (it should be free). Not a lot of load, but it was not quite right and would potentially hold the rear carb open slightly. I loosened the front carb and gave it a jiggle. This was enough to take the tension off of the linkage. I tightened the carby back down and started the engine again.
Perfect! The engine ran smooth (ignoring the holes in the RH muffler).
The devil is always in the detail.
Just a follow up on the oil pump rebuild I recently did to close up the tolerances while the oil pan was off. It looks like it worked a treat.
The engine is idling high at around 1000rpm so it doesn’t stall when in gear. I now have 20psi at idle when hot, and well over 30psi if I increase the revs higher. This is much better than the 10psi I had previously.
I can now drive the vehicle up and down the driveway, which is cool. I need to check the brakes next and also bolt the steering wheel on (refurbishing this is a lower priority).