Monday, November 25, 2013

Oil Cooler

Yes Yes Yes, I know I haven't written on here in ages. Life has been getting in the way! Slowly slowly little things are happening  on the Cobra. The oil cooler is almost done. Here is a pic of the cooler I am using, from Finishline;

It has -10 AN fittings cast/machined into the housing. I am using all Aeroflow braided hose with black AN fittings for all my plumbing around the car. So the cooler gets mounted to the chassis with a couple of steel brackets which I fabricated and painted black, and then -10 braided hose with a couple of 90 degree hose ends;

Then comes the oil thermostat. A thermostat is important so the oil does not run too cold for too long, and has a chance to heat up to normal temperature before being totally passed through the cooler. This unit is from Improved Racing;

More -10 hose, and some angled fittings. The two heading rearwards towards the engine are 30 degree, the one heading out the left to the cooler is also 30 degree and the right hand front is 120 degree. The hose is secured in strategic locations with rubber coated stainless steel P clamps, and extra zip-tied rubber in certain locations to protect the chassis from rubbing of the stainless steel braid.
I am yet to install hose ends on the engine end of the hoses, I will that in another post along with the after-market oil pan that I have going on the LS3.



Friday, August 16, 2013

Fuel Pressure Sender

Next up to go on is the fuel pressure sender. This again matches my VEI fuel pressure gauge, and is an electronic sender with a 1/4" NPT thread. This sender could theoretically go anywhere in the pressure fuel line, but I think the closer to the engine the better. As luck would have it the LS3 factory fuel rail has a fitting on it, although sadly it is not 1/4" NPT. The fitting on the end of the fuel rail has a Schrader valve in it, and is presumably there to allow diagnostic fuel pressure testing by service centres. The end with the valve can be seen in the centre of this photo with the black cap on it.

The thread on this fuel rail fitting is -4AN, so we need an adapter to fit our 1/4" NPT fuel pressure sender. While a straight adapter is available, this would make it stick out a fair way, looking less than average and may also interfere with the not-yet-fitted power steering fluid reservoir. So I decided to dog-leg it, and use a -4AN / 1/4" NPT 90 degree elbow adapter together with another elbow which is 1/4" NPT on both ends, and then the sender attached to that. Here are the parts together with the thread sealer for the NPT thread.
Here is the Schrader valve fitting, remove the Schrader valve with the valve tool ($3 off ebay)
Then the fittings can be installed. The chosen method of turning it 180 degrees makes it three pieces long, but tucks it away nicely behind the injector wiring and coil pack brackets.


Friday, August 9, 2013

A few engine bolt-ons

I need to change and add a few things to the engine, and it is far easier to do most of this stuff before the engine goes in the chassis. First up is adding a water temperature sender. The factory sender is in the left-hand cylinder head, and will plug into the GM wiring harness and ECU. This factory sender is GM specific and cannot be used to feed an aftermarket gauge, but is critical to ECU operation so that the ECU knows the engine water temp. But the gauge I am using of course needs its own sender. The left and right cylinder head castings on Chev LS engines are the same alloy casting, so the location for the factory sender is also in the right-hand cylinder head and is blocked with a threaded bung from the factory. This is the best place to house the aftermarket water temp sender.

The gauges I am using are from VEI Systems and they came with the water temp sender. Like most aftermarket senders the thread is 1/8 NPT. The thread in the cylinder head is M12x1.5, so we need an adapter. Autometer make such an adapter, part number AU2277, but the internal diameter of it is just slightly to small to fit the sender, so I drilled it out by about 1.5mm

Then the body would fit inside the I.D.
And sadly this is where it all went wrong. Drilling out the I..D by 1.5mm weakened things enough that the housing of the thread adapter cracked upon tightening in the head - I didn't do it that tight I promise! I felt it give when tightening, and thankfully stopped quick enough that I was able to back it out with snapping it off in the hole, and without damaging the head. The crack can be seen in this picture just below the end of the thread.
Time for Plan B. I bought another thread adapter, and Autometer also make a "shorty" temp sender which fits natively in the adapter (part number 2259). I am not using Autometer gauges, thus I could not be sure that the resistance from the VEI sender and the Autometer sender would be the same, so I had to test it. So I cracked out the water temp gauge, a 12v battery, and for each sender I ran it under the hot water kitchen tap for a few mins and monitored the temp reported on the gauge - this confirmed that both senders are sending the same resistance to the gauge. In this pic it is measuring the VEI sender and the Autometer sender can be seen on the bench. Both senders reported the same temperature on the gauge

So the shorty sender went in the thread adapter with a bit of thread sealer and it's all buttoned up ready for attaching the sender wire.

Monday, April 22, 2013

Have an engine

The right deal came up at the right time, so I went ahead and purchased an engine! It is an LS3 crate motor. The LS3 is a Gen IV Chev small block, with it's roots in the legendary LS1. The LS3 is 6.2L (376 ci) and rated at 430 bhp (321 kw) and 424 lb-ft (575 Nm) of torque. This is standard equipment on the current model Corvette, and the local HSV VE Commodore derivatives.

The engine needs a couple of tweaks before being installed. Firstly the oil pan needs changing. The oil pan that you see in the picture is as delivered from the GM factory, and suits the Corvette and local HSV (VE Commodore). My CR chassis has a cross-member in the way, so this oil pan will come off and an afermarket unit will go in which has the "hump" more towards the rear of the engine.

The crate motor comes with everything you see on it, including inlet manifold, throttle body, water pump, exhaust manifolds, coil packs, knock sensors, cam and crank sensors, etc. The only other things it needs are an accessory drive setup - meaning alternator, power steering pump, idler pulley and belt tensioner pulley. This is all available from GM as a single part number. LS engines have three different harmonic balancer setups available. Which one is used depends on the vehicle that the engine is being installed into. There is one for Corvette, another for F-Body/Camaro, and another for trucks. The difference being the distance that the belt-line sticks out from the block. This crate motor came delivered with the Corvette line (the closest to the block) which suits perfectly the aftermarket drive kit that I intend to use, more on that in another post.

Further reading about LS engines here:

Wednesday, March 20, 2013

The Diff

The Classic Revival round-tube chassis is built to take the ZF diff unit as fitted (amongst others) to the VE Commodore. There are both LSD and non-LSD options available for this unit, along with a large number of ratios. While a second hand unit can be had quite readily from a wrecking yard or ebay, the ratio options are quite limited. This is because with a manual transmission either a 3.45:1 or 3.7:1 is preferred. Manual SS VE Commodores came with 3.45:1, while manual HSV's got 3.7:1. The second-hand 3.7 units from the HSV's get snapped up quick smart, and go for (in my opinion) to much money considering their mileage and condition.

Back in the day I had a VX SS LS1 Commodore, and although the diff in the VX was different to the VE's ZF unit, it had the same ratio of 3.45:1, and I was not 100% happy with it. When paired with a T-56 manual transmission I feel that a 3.7:1 ratio is a better fit. A diff from a wrecked HSV is hard to find, as they are snapped up quickly by Commodore owners looking for a cheap and easy ratio change for their SS. I never really wanted a second hand unit anyway - I view my Cobra as a new car, and I want to use new parts wherever it is feasible. So I picked up a new 3.7:1 LSD from Holmart, new old stock.

The front pinion flange on the diff needs to be swapped out because the three-pronged flange that Holden fit has quite a large radius and interferes with the round-tube chassis.You might wonder why the chassis was not made to fit the flange, but it would have meant altering an otherwise straight (and hence strong) structural piece of the chassis - a better solution is to change the flange for one that clears the chassis, in this case it is a Ford BA flange, part number BA4851A.

After removing the pinion nut it's fairly easy to pull the flange, no doubt a well bedded-in unit may have been harder to remove.

The next problem is that the dust cover on the new flange sits a couple of mm to low, and touches the diff housing. I pressed the cover on a little bit further in my workshop press, but that made it loose so a couple of tack welds sorted that out.

The last problem is that the new flange tube outside diameter is very slightly smaller than the original, this means the oil seal does not contact the flange and it would possibly leak oil. So the old seal gets carefully levered out so as not to mark the seal seating surface.

Then a new seal SKF part number SKF21283 gets knocked in, the old VE rear wheel bearing came in useful again for knocking the seal in square over the pinion.

Even though this unit is brand new, I went ahead and purchased a new pinion nut from Holden, as these are a one use item as the nut stretches when tightened. The nut is GM part number 92194936 and costs $27.25 - no that is not a misprint - it really is a $27 nut.

Now the unit is ready to go into the chassis, but that is easier said than done. As I am not removing the body from the chassis during this build, it was very awkward to fit the diff unit up into the chassis. It doesn't look difficult, but it soon becomes apparent that it needs to go in at a very odd and very steep angle, not so easy when the car is on stands and the diff weighs over 40kg so you cannot simply lift and tilt it by hand from underneath the car. I jacked the diff up while simultaneously using a strap over the chassis to tilt the diff to quite a severe angle to get the pinion over the chassis rail and line up the three mounting locations. Then in with three M12 grade 8 bolts, and it's done. This pic is after the angle shenannigans, ready to bolt-up.

I contemplated changing out the factory rubber bushes for an aftermarket polyurethane type. Manufacturers such as Pedders and Superpro have a few different stiffness' available, but some research leads me to believe that these polyurethane bushes in this diff in the Commodore community have resulted in some people complaining about ride harshness, and in a Cobra that weights 600kg less than a Commodore this is likely to be even more pronounced. So we're staying with the factory rubber mounts for now, I can always upgrade them later if the need should arise - although that will require the tricky job of removing and refitting the unit to the chassis!

Monday, March 18, 2013

Sunday, January 6, 2013

Rear Suspension Knuckles

The rear suspension of the Classic Revival round-tube chassis is based on the VE Commodore rear. In fact, it is the same as the VE rear with the following changes;
  • Driveshafts are shortened by 65mm each side
  • The top suspension A-arm is custom made
  • There is no rear K-frame, with all arms and components having mounts built-in to the chassis design
All the components I am using for the suspension are either brand new where there are moving parts (eg bearings), or stripped and fully-rebuilt/painted where it is a static component (such as a simple steel suspension arm). I will make a video shortly of assembling the rear-end, but first this post explains the rebuild of the rear suspension knuckle. I thought this was worthy of its own blog post because there are so many parts to the knuckle. After the knuckle was stripped bare, blasted and painted, assembly can begin;

Clockwise from the bottom left corner we have;
  • Main drive-flange
  • Handbrake backing plate and retaining bolts (backing plate has been trimmed as per this blog post)
  • Handbrake shoe and retaining spring
  • Main driveshaft bearing and retaining circlip
  • Top A-arm heim joint
  • ABS sensor and retaining bolt
  • Handbrake adjustment and actuating mechanism components
  • Two polyurethane bushes and crush tubes

The first job is to press in the polyurethane bushes. The cast knuckle unit itself is extremely unwieldy and an awkward shape. It is difficult to fit in the press for some components and impossible for others. There are 5 pressing operations to be made, for which I used a combination of workshop press, vice, and socket/bolt methods. The main drive bearing and drive flange must be installed with a proper press.

Once the bush is in, it is greased up and the crush tube can be installed by hand with some force.

The top suspension A-arm mounts to a heim joint unit which is pressed into the top mounting of the knuckle. This is an awkward piece to install. I started it and seated the first 3mm with the socket/bolt method, and then this is one of the awkward press positions you need to use to drive it home.

Fully seated

Next up the main drive bearing has to be pressed in. The bearing has the ABS reluctor built-in to the inner race, so the bearing must be installed in the correct direction for the ABS sensor to work. Installing this bearing is fairly straight-forward in the press. To push it home the last few millimetres I took the old bearing housing, ground it down by a few thou on the grinder so it wouldn't get stuck, and used it between the press and the new bearing, this insured I was pushing square on the new bearing and only on the outer race (there is no picture of this step, sorry). The old bearing also served nicely as a spacer underneath while pressing.

Then the bearing retaining circlip is easily installed

View from the back, ABS side

Now the handbrake backing plate and actuation/adjustment mechanism can be greased, assembled, and installed. The dumb thing about this knuckle design is that once it is fully together the handbrake mechanism cannot be removed without removing the drive flange, an action which destroys the wheel bearing in the process. I guess GM thought they could make money out of selling wheel bearings as part of a handbrake rebuild!

The two retaining bolts for the actuator housing and the one top bolt on the backing plate all get thread-locker - once it is finished there is no way to tighten them! The top bolt is out of view in this photo, directly above the bearing housing just under the middle-top of the handbrake shoe.

Next the main drive flange is pressed into the bearing. It's important here to have a supporting socket or other suitably sized spacer underneath the knuckle, with the inner bearing race resting on the spacer underneath (I used a large 3/4" drive socket, size-wise it needs to be suporting the inner bearing race). This is because the bearing inner race is actually two pieces, one on each side, which are held in place by the drive flange. Failure to support it means pressing in the drive flange will sepaate the bearing. In the end the bearing is held together by the drive flange. With the lower race supported, pressing in the drive flange forces the bearing together.

Insert the ABS sensor, thread-lock the retaining bolt, and voila. Finished!

Repeat for the other side. I didn't time it, but I estimate that the first knuckle assembly took me at least 3 hours, the second one took 50 minutes :-)