Exciting day - rebuild of 78 coupe

[johng]

The rest of my bits have now landed and cleared customs and I'm going to collect them next Tuesday, so I decided that it was time to start removing my existing exhaust. The pipes and mufflers all came off pretty easily, probably because the previous owner had renewed them and I had removed them whilst renovating the car. The cast iron manifolds were a bit more tricky. I had heard stories of manifold bolts snapping trying to get them off. This wasn't an issue though, they were all very tight but came off in one piece. The trouble was getting at them. The long stud which goes through the A/C compressor needed a very thin wall and very deep socket, I had one which was thin enough but not long enough. The end of the stud stuck out of the end of the socket, so no way to get a ratchet on it. In the end I managed to undo it with a pair of mole grips on the outside of the socket (very Bubba). At the other end of the passenger side the heater box prevented me getting a socket on at all, but luckily it came undone with a ring spanner and a long bit of tube.
What surprised me the most was the total lack of any gaskets between the manifolds and the heads. I take it this is not normal! I had always thought that the engine had never been touched as everything on it looked original, now I'm not so sure.
The good news it that now it's going to be very easy to replace my spark plugs and wires. I'll also need to give the engine a good clean up.

 

[teamzr1]

Where does that braided ground wire go to ?
Looks like it needs replacing, and that ground point really cleaned up or ground connection point moved somewhere else to
assure good ground for electrics for engine and ground to chassis

 

[Roscobbc]

Not a bad idea perhaps John to source the correct threaded 'bottoming' tap and run it through all the exhaust manifold fixing threads and getting any rust and crud cleaned out - ARP 12 point stainless bolts are great for securing manifolds/header flanges - the reduced heads make it far easier to get a socket in there!

 

[johng]

Where does that braided ground wire go to ?
Looks like it needs replacing, and that ground point really cleaned up or ground connection point moved somewhere else to
assure good ground for electrics for engine and ground to chassis

That strap just connects to the cover over the distributor, it's to stop radio interference, but you can't really hear the radio anyway . You're right though it does need cleaning up.

Not a bad idea perhaps John to source the correct threaded 'bottoming' tap and run it through all the exhaust manifold fixing threads and getting any rust and crud cleaned out - ARP 12 point stainless bolts are great for securing manifolds/header flanges - the reduced heads make it far easier to get a socket in there!

I've got a set of taps Ross, so I could run one down the holes. On the other hand I might need a bit of crud to act as locking device to stop the bolts coming loose! The headers do come with a set of small head bolts, so I'll see how well they work.

 

[Forrest Gump]

What surprised me the most was the total lack of any gaskets between the manifolds and the heads. I take it this is not normal! I had always thought that the engine had never been touched as everything on it looked original, now I'm not so sure.

I‘ve read before that GM didn’t fit gaskets on the iron heads and manifold. Gaskets were retro fitted if there was a leak.
You'll need a gasket with your headers though.

 

[johng]

That's good news Andy, perhaps my engine is unmolested after all. Changed the plugs and leads today, so much easier without any exhaust or manifold in the way.

 

[Roscobbc]

Header gaskets can be problematic John if header flange isn't 'square' - I've tried them all - and eventually they'll leak and burn-out. Solid copper is an option - they can be annealed for several uses.
The best header gaskets I've used to date been multi-layer aluminium like these - 1978 CHEVROLET CORVETTE Flowtech 99150FLT Flowtech Real-Seal Header Gaskets | Summit Racing. Re-useable too.
Also going to say that quite often the header bolts supplied with headers can be rather short and perhaps work loose even with spring washers. Perhaps check depth of threads in head?.

 

[johng]

That's good info, thanks Ross. Those gaskets look good, although just a little pricey. I'll put a straight edge across the header flange before I fit them.

 

[Forrest Gump]

Your headers might well come with gaskets, it’s worth trying them first.
I‘m still using my originally supplied ones, layered/aluminium type, no idea what brand. I’ve tried others (from good brands) when I’ve had to take the headers off (thinking good practice to replace gasket) but they’ve failed and I’ve gone back to refitting originals that continue to be fine surprisingly.
Notice the end holes on the gasket are slotted so that you can drop it in after you’ve got the header loosely bolted on, which helps.
Ive had more trouble with the collector flange gasket burning out. I’ve got copper ones in that location now.

 

[johng]

Yes the headers do come with gaskets. I will try them first (just because I don't want to wait any longer!) unless the header flange is obviously not flat.

 

[johng]

Collected my bits today, they look good.



Had a go a fitting the passenger side header (thinking this would be the easy side). It actually wasn't too difficult, had to jack up the car and remove a metal shield around the front of the starter motor and a couple of spark plugs, then I could just squeeze the header in from below. The bad news is I could only fit 5 of the 6 bolts, so it will have to come off again for some fettling.

 

[CaptainK]

That looks really nice and shiny. Which headers did you go for in the end ?

 

[johng]

It was these
Hedman Hedders 68286 Hedman Street Headers | Summit Racing

 

[CaptainK]

It was these
Hedman Hedders 68286 Hedman Street Headers | Summit Racing

Nice one thanks. I did wonder if it were those ones as I was on Summit just the other day and spotted them in my wishlist from ages back. Back around 2016, not long after I got my Corvette, I decided to get headers and didn't really understand much about ceramic etc, and was fairly skint - so just got the basic Hedman Headers for around £200. They seem ok and do the job, look naff now though, and obviously the ceramic would have been good because of the heat. Be interested to see how you get on.

 

[johng]

Had some good luck and some bad luck today. I took the passenger side header off and filed out the offending hole which wasn't lining up, refitted it and got all 6 bolts in Then I had a go at the driver's side. I was right this was much more difficult, ended up having to disconnect the power steering ram from the chassis, turn the steering to full left lock, bend the water temp sensor connector and after about an hour of moving the header around it finally just slipped into place. The good news here was that all 6 bolt holes lined up and I got the bolts in. Then came the bad news, once I'd reconnected the power steering ram I discovered that it is just touching the header.


I'm not actually sure if I will be able to turn the steering to the right without it binding up (didn't have time to check) but there's no room for the suspension to move backwards. Anyone got an idea how I could move the ram forwards? Other than that I'll have to put a dent in the header, but that would invalidate the warranty.

 

[teamzr1]

What if you filed down the corner of that bracket where the arrow is and
would the clearance change at all once the car is back on the ground and jack than not forcing upward ?

 

[johng]

I guess I might be able to file the corner off of the ram, hadn't thought of that, thanks. When I put the car back down it didn't make any noticeable difference to the ram position, but it did change the position of the hoses. Whilst up in the air the hoses were clear of the exhaust, but down on the ground one of the hoses is also touching. I'll have to do something about that, but that shouldn't be too difficult

 

[Roscobbc]

John - have you tried putting the car down on it 4 wheels and rotating the steering side to side - is that 'interference' linear from left to right lock - will taking a file or grinder to the end plate comprimise anything - what condition are your engine mounts in? - sometimes poly mounts can slightly re-align the engine lower or higher in the frame - would a spacer under the L/H engine mount help clear the flange on the steering ram?

 

[johng]

Don't think I can put a spacer under the engine mount because the end of the header is only sitting about 5mm below the chassis rail and I need some space for the engine to rock. Left lock won't be a problem because the ram moves away from the header then, but right lock will move the ram further to the driver's side. At the moment filing or grinding the ram end plate does look like the best solution

 

[teamzr1]

I think angle cut on that bracket would have enough free space and not degrade the bracket's strength