Exciting day - rebuild of 78 coupe
- Thread starter johng
- Start date
johng
CCCUK Member
I got them from Topflight, but I guess most of the vendors would have them. They go between the chassis rail and the bottom edge of the cover, supposedly as shown in this diagram
There is a small hole in the chassis rail behind the main fixing slot for the muffler and the bracket is then meant to point forward and attach to the cover. The strange thing is that if I used that small hole in the chassis neither my lh or rh bracket lined up anywhere near the cover. However, if I drilled a new hole in front of the main fixing slot and point the bracket backwards it does line up pretty well with the bottom edge of the cover (if you use the lh one on the rh side!!)
Colour wise the plan is to get them to look as much as possible as if they are actually metal. That's probably a few weeks away yet though.
CaptainK
CCCUK Member
Ah nice one thanks. I see what you mean now. I don't think mine has them on to be honest. But then, I don't think I've actually looked down there.
CaptainK
CCCUK Member
I agree. Looks odd. They should have painted it the same silver colour as the "gills" so it all matched.
That said, my pipe covers are a different colour to my gills
(gills are actual silver, whereas the pipe covers are silver with a tiny tiny bit of blue to match the bodywork).
Nick B
CCCUK Member
Massively agree, looks rubbish!
Nassau65
CCCUK Member
It’s quite a common sight now at many stateside car shows to see C3 Corvettes with body colour side pipes.
On the non chrome era cars 1974-82 I suppose it’s fine to most owners as everything is the same colour.
I like side exhausts to “stand out” so aluminium or chrome to my eyes looks much better.
On the non chrome era cars 1974-82 I suppose it’s fine to most owners as everything is the same colour.
I like side exhausts to “stand out” so aluminium or chrome to my eyes looks much better.
Nassau65
CCCUK Member
Always loved side pipes since I first saw them on mid year sting Rays. My friend had Thrush outsiders on his 1969 Camaro RS/SS . I loved the look and the noise. Grafted a few sets on various cars over the years, from yanks to Capri’s and Cortina’s. 
not forgetting Transit Vans
not forgetting Transit Vans 
teamzr1
Supporting vendor
A bit of history
Angle and shape of the side covers of side pipes can better the slipstream, downforce and increase MPH
Also, further angle of A-pillar for windshield few more degrees pitched downward also increases speed
This was tested in a wind tunnel during designing
GM built and raced the #93 & 94 C4 ZR-1s
I bought and raced the below #94
If you notice the shapes and angles for exhaust and windshield, you can see a difference to normal side pipe covers
Angle and shape of the side covers of side pipes can better the slipstream, downforce and increase MPH
Also, further angle of A-pillar for windshield few more degrees pitched downward also increases speed
This was tested in a wind tunnel during designing
GM built and raced the #93 & 94 C4 ZR-1s
I bought and raced the below #94
If you notice the shapes and angles for exhaust and windshield, you can see a difference to normal side pipe covers
johng
CCCUK Member
I've made some progress over the past couple of days. First I bought a 2.5" pipe adapter which nicely fills the gap between the header and the rest of the exhaust. You can see it in the top right hand of this photo. Then I tackled the clash between the power steering ram and the header. I loosened off the hoses between the ram and the valve, rotated the ram anti-clockwise and re-tightened the hoses. This plus a little bit of filing on the corner of the ram means I now have a small clearance (about 3mm at it's worst position) between ram and header. I also loosened the hose from the pump to the valve and re-positioned that so that it is now well away from the header. I'm now in the process of trimming the body and covers to get them to fit nicely.
johng
CCCUK Member
The covers and body are now trimmed and holes have been drilled in the covers for the fixings. Yesterday I dropped them off to be sprayed, hopefully I will have them back in a couple of weeks. I've also finished fitting all the exhaust, plus new spark plug leads and boots to protect them. All the cutting, drilling and filing had made a bit of a mess of the car, so today I started it up, drove it onto my driveway and gave it a clean. The exhausts don't seem any louder at tickover, but do sound more aggressive when you rev it. The thing I'm not sure about is whether I need to alter the carburation any, now that I probably have a more free flowing exhaust. Any thoughts?
Roscobbc
Moderator
Theoretically with a free flowing exhaust one would expect it to run a little leaner - but car tuning on cars of this age have quite a wide tolerance range.......taking to account warm-up time with choke.....did you feel that it perhaps was a little weak (woolly response) before it got fully warmed through?
teamzr1
Supporting vendor
There are a lot of factors that will determine with exhaust changes as to how the engine will function and what setting will be
Such as the design of the intake manifold, carb size, headers, exhaust alone with engine factors as to CAM grind, compression, size of ports and valves, if chosen headers is the primaries are too small or large to too little or too much back pressure and will the total exhaust design generate good or poor removal of exhaust gases out of the cylinders and produce low amount of exhaust pulses
Incorrect type of header can kill off high-end torque
Hotter temps of primaries I would go 1 step colder spark plug with bit shorted gap set and heat socks
Total design than may show AFR too lean or rich and also if timing has to be adjusted first
To give some examples I made up a 327 CI engine with slight CAM and then run that engine in a software dyno, 3 designs
1. Stock exhaust
2. Short tube headers
3. Long tube headers
Clearly the more the HP and Tq numbers come up would require a richer AFR adjustment
Refer to bottom left for type of exhaust and engine flywheel HP/Tq computed
johng
CCCUK Member
Thanks guys
Ross - I've only driven it out of the garage and back so far, if the roads dry up a bit tomorrow I'll take it for a longer spin to see how it feels.
JR - Everything is still stock except the exhaust, so I'm not expecting any gain in HP/TQ
Tim - I've gone from the stock manifold with true dual 2" pipes, to not particularly long headers with somewhat shorter 2.25" pipes. I've no idea whether that is going to flow better or worse than before. My guess is that the manifold was the biggest restriction previously.
Probably the only way of knowing for sure is to get it on a chassis dyno with an O2 sensor up the exhaust.
Ross - I've only driven it out of the garage and back so far, if the roads dry up a bit tomorrow I'll take it for a longer spin to see how it feels.
JR - Everything is still stock except the exhaust, so I'm not expecting any gain in HP/TQ
Tim - I've gone from the stock manifold with true dual 2" pipes, to not particularly long headers with somewhat shorter 2.25" pipes. I've no idea whether that is going to flow better or worse than before. My guess is that the manifold was the biggest restriction previously.
Probably the only way of knowing for sure is to get it on a chassis dyno with an O2 sensor up the exhaust.
CaptainK
CCCUK Member
If only you lived nearby - I'd hand you my 1968 327 and ask nicely to get you to make it have those power outputs.