Corvette wind tunnel testing

Nice vid I found on YouTube of wind tunnel smoke tests of C1 through to C6 models. Interesting that even though the C3s curves look smooth, the headlights are a killer.

How to replace the gas tank on a 1968 C3

I recently had a bit of an issue with some pinholes in my gas tank seeping gas which at first glance didn’t look to bad. But as the tank had been repaired before and my repairs didn’t hold it was time for a new tank. Thought I’d write up the process just in case anyone needs it in the future. It’s up to you whether you jack up and support the rear of the car as the tank can be removed without it. But it will give you a lot more room to work in which you’ll be thankful for later.

 

Try to drive your car to as empty as possible before starting to drain the tank. You can remove it without draining it but damn it will be heavy as you lift it out. You can partially drain it by removing the hose from the sender unit in the base of the tank, but this will still leave 5 – 10L of gas in there.

Best way is to siphon the gas out from running a pipe in through the filler cap as that managed to get most of it out for me.

Once the gas is out you need to remove the fuel hoses where they attach to the tank. Remove the large hose at the sender unit, and on the 68 the return hose is on top of the tank so it’s easier to disconnect the return hose at the hard line on the right hand side rail. On mine the return hose was perished inbetween the two so I didn’t have to remove anything unfortunately.

If you have a later model chances are you’ll have a charcoal vapour canister on the left you’ll need to remove at this point too.

Next I removed the sender unit and fuel outlet from the base of the tank. Although not necessary, it’ll save you from accidentally knocking it around while removing the tank later. It apparently takes a special tool, but I just used a screwdriver and hammer to gently tap/rotate the 3 lugs around until the keeper ring popped out. At this point I found the pickup tube was missing the filter sock which explained some crud in the carb when I bought the car. Unit was nice and clean though.
 
I also removed the rubber splash shield around the filler neck and removed the filler from the tank as well to make for easier manoeuvring later.

If you have mufflers out the back then they will be completely in the way if you try to drop the tank. Easiest thing to do I found was to loosen off the clamps where the pipes are usually joined just in from of where they pass though the crossmember in the middle of the car. Once loosened you can undo the hangers and “gently” rotate the pipes down and towards the outside of the car giving enough clearance later to drop the tank. Remove the spare tyre carrier and especially it’s top shield at this point as well to give you room later.

Once this is done the tank straps need to be loosened off. The bolts for these are on the rear crossmember and need to come completely out so the straps are free. Of course on my tank I found only one of the straps was even bolted down! Looks like they didn’t attach one so it didn’t put pressure on their dodgy tank repair. Once the straps are loose it is handy to try to slide the tank back and to the side so that it is supported by the rear crossmember and side frame rail as it will make removing the support easier.

The support bar runs under the front of the tank to support it. This is held on by 2 bolts/nuts on each side (or only 1 each side on my car). To get this off you need to slide a spanner (1/2” I think) in though the handy gaps in the frame rail to hold the bolt head so you can turn the nut underneath. Loosen off both sides and the support will just be held by the back of the tank straps. Once the support is loose you can rotate it around so you can get the straps out of the slots on the back of it. Once the straps are loose slide them off the side of the tank and remove them as it will be easier when dropping the tank.

Now you can push the tank towards the back of the car to enable you to rotate the front of it down to drop the thing out.

Once I got the tank off I found it had 4 previous repairs along the ridge where it sat on the support bar. Research shows this is common as the spots get a lot of flexing pressure from the support. Also looking inside the tank there was a lot of rust residue along this line as well as the tank being is a dodgy state overall.

Reassembly is the exact reverse of the above process but a few tips will make it easier. At the end you’ll end up with a nice shiny tank in there.

1. New tanks are usually just bare steel. You can either paint it, or do as I did and just spray it with a few coats of clear to give it a bit better protection from the elements.

2. The front support bar and rear crossmember should have an anti/squeak pad across the top of them. I threw away the 40 year old stuff that was barely there and just got some rolls of sticky backed felt from the surface protection aisle at the hardware store. The adhesive makes it simple to stick it to the supports and prevent it moving when you are messing round putting the tank back in. I also used it on the underside of the top of the tank straps to protect the top of the tank slightly. Just make sure you don’t use too thick a felt as it will make the straps a pain to try to do up later (ask me how I know).

3. The bolt on my tank strap was 1 ¾” long. I replaced both sides with 2” bolts which made starting the tightening of the straps a lot easier.

4. While the tank is out take a look at the drains from the rear deck. Like mine they may be jammed up with 40 years of dirt. For a quick fix I just poked around with a screwdriver to clear them a bit and blasted from the top with compressed air to flush it all out.

5. While the tank it out it could pay to take a look at the rails and give them a bit of a cleanup and rust protection treatment while you are at it.

6. Before tightening down the tank straps check to make sure that the filler is lined up on top with the opening in the deck.

7. Don’t put the old gas back into the new tank. Chances are if the tank was rusty there will be rust particles in the gas that you don’t want in your new tank. This is not so much of a problem if you have lined the new tank with a sealer like the POR15 gas tank kit.

Replacing the fuel pump in a 68

Well one more thing on Frankenvette needed replacing so here’s another short writeup in case anyone else needs the info. The following should see you through replacing the mechanical fuel pump on an early C3.

My pump had developed a couple of issues. First oil was misting out of the little vent hole in the casing of the pump and being drafted by the airflow up and onto the hood. Second there was a tiny gap in the casing (circled in the pic below) that was also venting fluid as well.

Simplest option was just to replace the pump with a new one. Total cost for me was about $50 for a standard Carter style replacement (which came with a gasket) and a metre of 3/8″ (10mm) fuel hose. You may also need some 1/4″ hose if you intend to replace the return line as well if you have one.

First step is to find someone with a lift as that will make this job a whole lot easier.  If not, then just raise the car up on ramps or support it with stands under the jacking points on each side of the car. Now clamp off the fuel hose at the tank as it will stop the fuel being pulled by gravity when you remove the line on the pump. Also disconnect the battery so there are no sparks while you’ve got gas dripping about. If you don’t have a A/C compressor in the way then the next bit will be a lot easier. If you do, then it’s time for a bit of contortion.

On the front of the block in line with the fuel pump there should be two holes in the block with the top one filled by a bolt. If you remove this top bolt and thread in a longer one (I used a 3/8″ x 1 3/4″) you will be able to trap the rod that drives the pump so it won’t fall out when you remove the pump. Believe me this will make life a lot easier when re-assembling things.

Next remove the soft lines to the pump. Now you may have a 3/8″ feed line and a 1/4″ return line to remove, or you may have a modified setup with only a feed line. Either way remove the clamps on the hoses and pull things off. It’s a good idea to have a tub or something to catch the gas that will drain out or you may end up lying in it when under the car for the next part. Next remove the hard line from the pump to the carb at the pump.

That’s the easy part done. Now time to remove the pump. It’s held on by two bolts. The first is nice and easy to get to from the top/front by sliding a ring spanner past the lower radiator hose onto it. More fuel will drain from the pump as it starts to come loose. Now there’s the last bold left. This you can get to from underneath with a ring spanner, just. On my car there was about enough room for about 1/8th of a turn at a time so this last bolt took a long time. Once it comes out the pump will either drop off or need to be pried off because the gasket has stuck so you are half way there and probably should go have a beer to celebrate.

Next if there are signs of an oil leak from behind the mounting play you may need to take that off too via the two bolts that retain it. I didn’t have a gasket handy so left mine for now. Either way you will need to clean up the surface as there’ll be crap from the old gasket all over it I’m guessing.

Easily cleaned up from underneath with a scraper as there’s enough room to get one up under there. Just be careful not to cut your radiator hose as it’s going to be close.

Now is probably a good time to take the hard line to the carb out and check/clean your filter and line as well. I found a whole heap of crud in my in-carb filters (from my old bad tank).

Getting the new pump on is a lot easier now you know how it all came apart. Put the gasket on the pump and feed the two bolts through it. This will hold the gasket in place while you fit the pump. Get under the car and feed the pump lever into the hole so it’s under the rod. Now you’ll need to try and hold the pump with one hand while trying to start one of the bolts with your other hand. Once that’s started try the same with the other bolt which will most likely be a lot harder due to the tight space. Do them both up tight once you are able.

Next refit the hard line from the carb, and the feed/return lines. I replaced the feed line at this point as mine looked old and was starting to crack. Apparently the original fuel line in a 68 was moulded so it would curve nicely to from the line to the pump. If you replace things with standard hose make sure you have enough so you can route it without causing a kink and pinching the line which will restrict the fuel flow.

Once the lines are on and the clamps tightened remove the clamp on the line at the tank. Also remember to remove the bolt holding the pump rod and replace it with the original bolt. make sure this is done up tight otherwise it will seep oil.

Now it’s time to drop the car down and reconnect the battery. Crank the car over a few times without pumping the gas pedal to get the new pump going and prime things with fuel. Once you think it’s right then give it some gas and try to start it. All going well you now have a sweet running car. After a minute or so stop it and go and check the connections at the pump for signs of gas or oil leaks. Tighten everything if there is and repeat the process. Now go have a beer because it’s well deserved.

In the beginning – the start of my Corvette fascination

Reading the forums out there most people seem to trace their fascination with Corvettes back to when they were a kid.  There’s a lot of “My brother used to have one” or “the guy down the street had one”.  Well that’s probably the case in the USA where the vette was born and bred.  However growing up in New Zealand there wasn’t a huge amount of American iron (or fibreglass) rolling around on the streets.  So it wasn’t until the 80’s that I can recall seeing my first Corvette and thinking “wow that car looks cool”.  What’s even stranger about this is that it wasn’t even a real car that I saw.  Nope, it was a telephone.

Around 1980 I was given a novelty telephone as a birthday present I think.  Now having my own phone was cool enough, but the fact it looked cool (and seemed to resemble the batmobile I had seen in comic books)  was just great at the time.  Turns out the phone was in the shape of  a late C3 similar to this one that I found pics of out there on the net.  Sweet, my first vette before I hit 10 years old!  And now 30 odd years later, I finally own my second vette, just this time it’s a bit bigger.

The unique 68 vette – or why won’t that later c3 part fit

If you ever become the owner of a 1968 Corvette you will quickly come to realise that GM did things a bit differently with this car when it comes to parts.  Sure, as the first of the C3 generation of vettes you could expect it to not share a lot with it’s predecessors (although it did still share a chassis and certain other drivetrain components).  However what you may not expect is how many of the parts changed several times within the 68 production run, and how many then were not carried over to the 69 and later years.

What this means is that some original parts that you think might fit, won’t. Some original parts you won’t be able to find easily.  And you will expect to have to pay exhorbitant prices due to either the original parts rarity, or the low volume production/demand for reproduction parts.

Over the past year I have come across a lot of info on the internet about the supposed unique parts on these cars and have been noting them down with the aim of compiling a useful list here.  Some of the links to the original source of the info I have lost, or just do not work anymore, however a lot of the items below have been collated from dozens of posts at http://forums.corvetteforum.com.  Using the search function there will find the source of many of these.

Also if you are a 68 owner then come join some of us other owners on the “1968 Corvette Owners Group” on Facebook.

So onto the list.  These are all either parts that are supposedly unique to the 1968 vette, or only shared with perhaps one other model year.  If you can shed any light on whether these are correct or not, post a comment and I will amend the list as needed.  I’ll also be adding pics of any of the various unique items as I come across them. Where I remember I have linked the item to the source info I used for it.

[5 March 2015] Just came across  this site which has a handy illustrates summary of some of the 68 differences.

Last updated 5 March 2015

Interior

• Left side dash panel with ignition switch
• Right side dash panel with no map pockets
• Two different 68 only style interior door panels – door pulls added for later 68’s as the original hidden ones would crack
• No pull loops on rear compartment doors
• The coupe interior had 2 sail panel courtesy dome lights (one on each side) that was reduced to just one for 69, (drivers side) and later dropped completly.
• 2 different types of spring loaded rear compartment hinges
• Coupe middle storage compartment lamp assembly/lens is possibly unique. Some people have said they have a simple bare lightbulb, not the more normal lamp assembly and cream colored lens
• Early seats & seat backs are unique to 68 – release lever is on the lower part of the seat back (and is really annoying to get to when the seat is all the way back in the tracks!)
• Second design seat shared with 69 – release lever on the upper part of the seat back
• 3 different headliner types for coupes
• Removable rear window latches – different shape to later models
• Steering column – under dash mounts differ from later years – cast rather than the later pressed metal design
• Steering column itself is similar to (but not the same as) the 67 in design and assembly
• Shifter ball  is a plain chrome ball (not the black chrome as found on 69’s and up)
• Shifter console plate has no engine ID plate
• Park brake console – the parking brake console had pockets for the seat belts
• Seat belts were possibly one year only items
• Comfort weave seat covers were a 1 year only option
• Tobacco was a one year interior color option
• The shift boot on early cars was part year only, later ones were the same as found on 69’s
• The center gauge bezel has a smooth finish, not the wrinkly finish as on 69 and up
• Some variations in door ajar lights in the center gauge bezel across the production run
• Wiper overide warning indicator can be found on the center gauge bezel of some models
• Radio knobs had 2 different 68 only styles
• Kick panels were one year only style
• The panels that attach to the side of the forward console were a part year release –  early car ones just had a clip while later ones had a screw fastener
• Steering wheel was 16″ simulated wood (may possibly be shared with 67 so some say)
• Early 68 interior door handles were smooth on the back – later casting had ribbing on the back for added strength
• Dash mounted ignition switch
• Windshield pillar interior moldings on inside of car were unique
• The original external seal between the door windows and the door was unique. It was a strip of rubber about 1/2 inch wide that ran the length of the window – it made a seal between the window and the top of the door. It was completely external as compared to the 1969 window seal that is partially internal. No repro items seem to be available.
• T-top weatherstrips
• T-top moldings
• The center wiper/dash vent bezel on a/c cars was unique.  Reproductions are not available so if you have one spare let me know as I’d love to replace my broken one!
• Brakelight switch is a square one year only item – the original 68 switch has a toggle type switch (later models used a plunger type) that when you press the pedal the switch closes the circuit and the tail lights come on. When it goes bad what you see is people using the 69 and later switch as a replacement using a different mounting bracket.
• Early year plastic front fiber optic plate is different
• Vent knobs carried over into early 69’s but changed thereafter
• Early 68’s had the vacuum/wiper overide controls more to the right near the console. They were moved to center later in the production run
• The 68 tach cable was screw on as opposed to the later clip style
• Tach cable length is different in 69-later cars
• Headlight switch bezel was unique to 68
• The turn signal switch in the steering column is shared between 67 and 68 models
• Only telescoping steering option – no tilt option until 69
• Real halo panels (on coupes) were configured differently.
• No gromments were used under the interior dash screws.
• Shoulder belts did not retract, had a “hanger” and did not have the guides on top of the seats as found on some 69 models
• Flasher location was changed from center console to pass side dash panel during the production run
• Brake handle is 68 only
• Steering column covers
• Top dash cover has no speaker holes
• Bracket for drivers side odometer-reset/speed warning/courtesy light is different between early and late 68,  Early has no provision for courtesy light (is possibly separate piece that screws on).  Late bracket is all in one with hole for courtesy light included.
• Sunvisors/pins were unique to the 68 model and also differed between the coupe and convertible versions.  Also according to the “Corvette Parts Interchange Manual 1968-1982” the part numbers changed in approx Feb 1968.

Exterior/Mechanical/Body

• Doors had wider door panels – 69 were scalloped to give more room inside the car
• Exterior door handles
• Push buttons to open doors
• Door internal latch mechanism unique to match push buttons
• Door window wipes inner and outer were of awhisker style, not the felt used later
• 2 or 3 different windshield header moldings used across production run – early cars were 1 piece design
• 2 different top alignment pin receivers
• Outer windshield moldings
• Removable hardtop rear mounting hardware was different, pin size was smaller, no 3rd center bolt, convertible top rear pin latches different
• Wheels  were 7″ wide rims
• Back up/reverse lamps on rear valance/exhaust panel, whcih makes the panel itself different to 69+
• Gas door emblem riveted on gas tank fill lid
• Gas door bezel used an interference fit rather than a spring clip to hold it open.
• Side marker lights were white lenses instead of yellow as in later years.
• Rear deck vents
• Antenna mast and nut shared with 67 – but exterior bezel is a 1 year only and not repro’d.
• Front grilles had several production changes over the years run – chrome/silver paint only on the leading edges of the center 4 ribs across the whole grill, including the center.  Some later 68’s may not have had the silver paint.  Also ribs protruded from surround edge, as opposed to 69/repro where the ribs front is flush with the plastic of the surround.  See this thread for good pics and descriptions – http://forums.corvetteforum.com/c3-general/2983666-1968-grille-pics-needed.html
• Small front spoiler
• Front grill brackets made up of multiple pieces – 69’s and later were one piece
• Real early front bumper is one year only design- though a 69 will interchange with it
• Angle on end of front bumper reinforcement extensions was different
• Hole spacing on front bumper outer brackets are different from 69 (holes on 68 frame are spaced differently)
• PO-1 Wheel covers were 68 only
• Door sill plates may have been unique – rumor is they were wider on early 68’s on the innermost side
• Side rear view mirror placed a lot further forward on early 68s than later 68’s
• True quad red tail lights
• Side “gills” were plain body colur with no moundings
• No stainless “tips” on the rear tip of the optional hard top
• No bumper stops on rear convertible deck lid
• Reverse light switch is unique to ’68
• The paint formula for Lemans Blue in ’68 is different than it is for ’69 (the 69 blend was shared with the 68 Camaro which was different form the 68 Corvette) according to anecdotal evidence from “a DuPont guy”
• Early ’68’s lacked the kick-up reinforcements behind the rear wheels that were added later in the production run.
• No holes in the lower front valance on early cars – Dealers were instructed to retro cut these for improved airflow to the radiator.
• 3 different sized headlight doors across the production run
• 3 different metal surround panels/bezels to go with the headlights
• 2 different wiper door grills – one with cutouts for washer nozzles, one without
• Washer nozzles 2 different types depending on the wiper door
• Didn’t have a wiper door close safety valve as found in 69 and later cars
• Radiator core support has holes in it to allow the wiring harness to pass through.  This means they also have flat inner fender walls next to the support whereas later models have a notch to allow the harness to pass
• Small block valve covers (L-79) were unique (Chrome stamped?)
• Rocker covers were a two piece design that carried over into 69
• 327 engine was unique to 68 C3s (one year only large journal)
• Wiper motor is unique (wiring and opertation)
• Wiper arms
• 20 gal gas tank
• Steering damper on the drag link was a part year option, later canceled
• Body mounts were solid aluminum, later years were rubber (some early 69’s may have had the solid mounts)
• Dash wiring harness
• Front spindles are the same as 67`s and earlier. 69`s and after are different bearings.
• Inner fender splash sheild were changed from stapled to push pin.
• No hood insulation
• Spare is also mounted on a ralley wheel. Was this also done on a 69?
• Front bolt-on cross member doesn’t have holes in it, whereas later years do to allow for the radiator support to bolt to them.
• External voltage regulator
• Headlight / wiper door vacuum relays unique
• Can wiper door actuator and connecter –  ’68 Wiper cans had 1/4″ shafts. Early ’69 wiper cans had 5/16″ shafts. Sizes (rod diameter) are dif between early 68/late 68, and 69
• Headlight vacuum canisters
• Hood latches located differently to later years
• Smog pump on small block had relief valve
• Frame on early 68’s differed from late 68s – bolt holes on frame horns and their extensions were of a different configuration.
• Oil fill cap  – possibly same as on a 67
• Intake manifold (has oil fill tube)
• Door alignment shims
• The 68 had a nose support bracket that was part year only, none for early models
• Rear brake lines (top inlet on caliper)
• Left side exhaust manifold (alternator mount)
• Rear plenum vent tubes
• Upper door hinge is possibly one year only part but is interchangeable with 69 and up. The difference is a shorter spring and the tongue configuration is shorter than 69 and up. (however some grinding may be required to prevent it taking a chunk out of door when fully opened as the door on my 68 can attest to.)