Exhaust System - 1954 Pontiac
I had to ditch the original exhaust manifolds for two reasons: first they were smog busters and had the air injectors in them and second the passenger side manifold exited into the firewall. I needed the passenger side exhaust to exit between cylinders 4 and 6 in the middle of the block and straight down. Here's a website that lists pretty much every SBC exhaust manifold with pictures to help find the right one.
Smog buster exhaust
I replaced the passenger-side exhaust manifold with a driver-side ram's horn manifold which probably came out of late 60s to early 70s Chev pick-up. The driver-side ram's horn manifold has mounting bolts for the power steering pump. They're called ram's horn because they look like ram's horns and supposedly flow very well. This one was painted silver which should dull pretty quick once the engine runs. I will probably grind off the power steering pump mounting bolt flange just for looks. There are two sizes of ram's horn manifolds: 2" and 2 1/2" I believe. Corvette's and high performance cars used the larger size for better flow, consequently they are about 5-8 times more expensive than the 2" outlet. I paid $30 for the 2" and the local Corvette restoration place wanted $200 for 2 1/2" manifolds in bad shape.
Shiny painted ram's horn exhaust manifold for passenger-side.
Poor casting - lower right corner flash restricts exhaust
It's difficult to see but the lower right corner is not rounded but has flashing present from poor factory casting. I will be grinding off the excess flashing.
New Problem!
New problem with the Ram's horn manifold on the passenger side! I was trial fitting the rack n pinion unit when
I realized that the ram's horn exhaust pipe exitted exactly where the rnp sits. From the front of the engine on
the driver's side, I have the fuel pump and front crossmember, the motor mount, the rnp and the starter motor.
There is no place to exit the exhaust between the block and the frame.
This exhaust exits into firewall support
I found a cast exhaust manifold that exits into the firewall support. I figure that I can make a 5" diameter hole in the firewall support using steel pipe and exit the exhaust through there. It should look pretty nice. The alternative is to remove the firewall support but that could get messy and wouldn't look right with only the driver's side support present.
The problem was how to center the manifold's exhaust pipe opening in firewall support. I figured that I would have to make spacers that would move the manifold away from the block. After several trial and error fittings using wooden blocks cut to size. I determined that 1 7/8" spacers would work perfectly. There may be a clearance problem between the lower exhaust pipe bolt and the frame but I figure I can raise the engine slightly on its engine mounts using some washers.
Wooden spacers in place to test fit exhaust manifold
Hole cut in firewall support and 5 inch diameter ring ready to be welded in place
This is the view from behind the firewall support showing the tight clearance between the firewall, firewall support, ring and frame
I've sand casted a set of cast iron spacers to move the exhaust manifolds 1 7/8" from the block. I'm going to use cast iron to match the temperature expansion/contraction characteristics of the block and manifold. Hopefully, this will stop the bolts from loosening up (come to think of it I should probably use the same material as the bolts!) So with all the fun that I've had milling metal, I'm looking into sand casting.
Here's the spacers cleaned up a little bit but in need of final machining
Here's the spacers after machining and temporarily bolted in place while fitting the exhaust pipe
This picture shows the hole and ring welded into the firewall support much clearer. Take a look farther down at the picture of the exhaust pipe and the 6 bends required in 3 axis in order to run the exhaust pipe to the manifold.
I made some studs from 4 1/2" bolts so that there wouldn't be too much strain on the head's bolt hole threads. Unfortunately, you can't slide the manifold off and on the studs cause the top of the front suspension is in the way. :-( So the studs are screwed in after the manifold is in position which makes it a pain to do.
Driver's side exhaust
I found a driver's side manifold that had good clearance, exitted exactly where I wanted and had comparable
flow (just by eyeballing it). I purchased and installed it. Unfortunately, all small block chevs aren't
made the same. This one completely covered my dipstick hole which is located between cylinders 5 and 7.
Perfect fit except covers the dipstick hole!
I did find a driver-side exhaust manifold that is identical to the original but without the smog ports on it. Unfortunately, I now have clearance problems between one of the mounting studs and the frame. It is very tight. I'm hoping that when the exhaust pipe is installed and bolted in place, I can cut the stud off and fix the clearance problem that way. The alternative is to find another manifold or notch the frame which I really don't want to do.
Driver-side exhaust manifold
I had to notch the frame to clear the stud. I used a die grinder to cut a 2" slot on the top of the frame parallel to where the notch would be. I then cut a 2" slot vertical slot in the side of the frame where I wanted the notch. This allows the sides of the frame to be bent in to the slot on the top of the frame. Weld it up and you have a nice notch that looks original. .
Knotches cut out and ready to weld
Completed knotch showing new clearance
Dual Exhaust Pipes
I'm running out of time and money and just to get the car on the road, I've decided to pick up a set of dual exhaust
(non catalytic convertor) from the local wreckers. Most cars end up at the wreckers through this process: pour
money into the car to fix it, something else goes wrong, get fed up and junk it. Quite a few vehicles have new
exhaust systems installed due to the age of the car and then something else goes wrong (like engine or tranny),
the owner says enough is enough and gets rid of it.
I'm going to look for exhaust pipes and mufflers in good shape, relatively straight from the manifolds to the mufflers. Once installed on my car, I'll exit the exhaust tips just in front of the rear wheels. That should require the minimal amount of time, money and effort to get a working set of 2" exhaust pipes. Down the road, I would like to exit them over the rear axle and out the back but then you're talking custom bends and mucho money versus $50 at the wreckers.
Went to the wreckers, looking to measure brake hose lengthens and found a 1980 Chev pickup with a relatively new dual performance exhaust on it, no catalytic convertor and stock exhaust manifolds. The exhaust stopped just before the rear axle. This was ideal. The mufflers were so new that there wasn't an ounce of rust on them and the pipes were solid! Total cost $23 and 15 minutes to remove myself (I was expecting 2 hours with a hacksaw!). All the bolts except for one came off relatively easily. I even got the mounting straps! Love those junkyards!
Dual exhaust - $23 from the wreckers
I'm going to loosen off the mufflers and install the pipes to the manifolds, then cut the pipes where I want them. The driver's side looks like it will be a cinch to install but I may have to bend the passenger's side pipe to fit the ram's horn manifold. I will exit the exhaust just before the rear wheels.
Hint: use a radiator hose as a guide when cutting exhaust pipe
Driver's side exhaust ready for installation
Here's the passenger side pipe that required bends in all 3 axis.
For the passenger side, I ended up using short 20-30 degree pipe bends and welded 6 pieces together in all 3 axis. What isn't shown in the above picture is that the pipe has curves bending directly towards the camera. It is a tight fit. After about 2 days work fitting and welding the pieces together, I realized that there is a much simpler path that goes over the tranny crossmember rather than under it. Oh well. Live and learn for next time....