Exhaust & Headers - Part 1 - Initial Fitting

I have gone a slightly different route, it seems, from most of the other AK LS builds out there at the moment.  The majority of builders appear to have used the standard GM LS headers (either LS3 or LS7), I suspect for no reason other than they were supplied with their engines.  Not that that is an issue, both the LS3 and LS7 stock headers are pretty well matched to the engine and perfectly adequate for most street-driven applications.

However,  my engine was supplied without any exhaust headers.  Now I could have probably tracked some factory GM items (although when I initially looked there were not that many around) but I kind of like the look of proper tubular headers in the engine bay and, despite the cost, I knew that really I was always going to go down the route of buying the AK stainless steel headers and side exhaust system.

AK can supply headers in two diameters 1 5/8" or 1 7/8"; the former is typically for LS3 builds and the latter for LS7.  I had a chat with Jon about which size to go for. His view was that the smaller diameter headers would be a better option; typically larger diameter pipes are good for higher horsepower and high revs, while a smaller diameter is better for low-end torque and a better option for "normal" driving.  Looking online, I found that most LS aftermarket tubular headers are 1 3/4" in diameter so I went with the smaller AK option.  Which turned out to be quite handy as Jon had a complete set of 1 5/8" headers and side pipes on the shelf from a customer who no longer wanted them!  And so a week later they were in the boot of my car and on their way back to my garage.

AK Stainless Steel Tubular Header

Set of Exhaust Gaskets from LSX Performance - complete with instructions!

Comparison of Exhaust Port D shape/size in relation to Header tube size

Initially, I installed the headers onto the engine without the gaskets and just with a couple of bolts to hold them in place.  I can see that with the additional Gen III chassis bracing getting the front header bolt in place and tightened up on both sides will be fun.

Shiny tubes!!

The AK side pipes come with some mounting brackets and rubber bobbins (which look suspiciously like engine mounts!) which sit between the side pipe and the bracket.  

Rubber bobbin between side pipe and mounting bracket

The brackets are intended to be welded to the chassis but, following the example of many other builders, I am going to bolt them on and use a threaded bung welded into the chassis for added strength.

Firstly I marked the centre line on the top of both brackets and then bolted the bobbins and brackets to the side pipe (with the bobbins bolted in the centre of the slotted end of the bracket to give some adjustability), slid the pipe onto the headers and then used a couple of clamps to hold the whole assembly in place.  (I put plenty of blankets and bubble wrap down on the floor to prevent any damage in case I dropped the side pipe in the process!).

I could then finagle the side pipe backwards and forwards until the distance between the pipe and chassis was the same at both mounting positions.  I ended up with the pipe approximately 85mm set off from outside the chassis rail on both sides.

Offside side pipe is temporarily held in place...

...and the same for the nearside side pipe

Offset from chassis approximately 85mm

Ensuring that the brackets were at 90 degrees to the chassis rails I stuck a bit of tape on the chassis and transferred a mark for the centre line of the bracket onto the chassis.  I drilled a 10mm diameter hole through the top and bottom of the chassis rail and opened the top hole up to 20mm with a hole drill at each bracket position.  I could then drop in a couple of bungs made from 20mm diameter steel bar into which I drilled and tapped an M10x1.5 threaded hole and once I had drilled a 10mm diameter hole into the mounting brackets, these could be fixed into place with M10x30 bolts.

The centreline of the bracket transferred to tape on the chassis

20mm Diameter bung threaded for M10x1.5 on the underside

The last job was then to drill a 10mm hole in each of the mounting brackets, which I also powder coated in gloss black ready for final installation.

Bracket after drilling and powder coating

I then re-wrapped the side pipes in bubble wrap and put them away until the body is mounted and the pipes will need to be fitted into place again to finalise the position of the hole in the body.

Heating and Cooling - Part 2 - Radiator Plumbing

 A few weeks back I took a trip to AK to pick up various shiny parcels and to give my credit card a sharp intake of breath...

The shiny parcels included my side pipes and headers, but also the air inlet pipe, the radiator header tank and the top and bottom radiator pipes.  

This meant that I could get on with plumbing in all the radiator hoses.

Shiny new radiator header tank

The first job was to swill the header tank out with some water to remove any detritus that remained lurking within.  I then filled the tank with water and bunged up the bottom outlet pipe for an hour or so just to check that there were no pinholes in the welds that would leak.

No leaks from welded joints!

The header tank is mounted to a cross-member at the front of the chassis.  I marked the centreline by measuring between the two radiator top-frames and then marked two lines 50mm on either side to allow for the diameter of the air inlet pipe.  I then marked another line midway between the "edge of inlet pipe" line and the radiator top frame and then centred the mounting holes for the header tank on either side of this.

Centres for mounting holes measured...

I then centre-punched the holes, drilled out to 6.8mm, and tapped for an M8x1.25 thread.  The header tank was then installed using 2No. M8x20mm stainless steel bolts with spring washers.

Header tank installed

The radiator top hose was connected up next.  AK supply a stainless steel section of pipe which is joined to the radiator and to the engine with some lengths of flexible hose.  I had measured the stubs on the engine and the radiator to determine the hose bore needed and had purchased some 35mm bore silicone hose.  The AK stainless pipe is actually around 38mm outside diameter, so while the 35mm bore silicone hose could be squeezed onto the stainless pipe, it was a tight fit.  To my mind, however, this was the right thing to do; using a larger bore pipe to fit onto the stainless pipe would result in a looser fit onto the radiator and engine stubs and, while the silicone hose might be compressed enough to seal when tightening up the jubilee clips, I think having a tighter fit in the first place presents less risk of leaks.

AK supplied Top Radiator Pipe...

...installed in place with a short length of silicone hose at each end

Thinking ahead I angled the tightening screws on the jubilee clips securing the silicone hose at the radiator end so that in future they can be accessed from the side or below; once the body is on, access from the top will be impossible and it's very tempting to just secure these clips with the screws pointing upwards!  All the hose clips were tightened to 5Nm torque and rechecked again after 30 minutes or so to allow for any relaxation of the silicone.

Next up was the connection between the header tank and the small pipe on the top of the engine which connects to the water galleries in the cylinder heads, and the header tank overflow pipe.  I used some silicone hose with a bore of 6.5mm for both of these.  I secured the overflow pipe with a couple of P-clips secured with some M6 button screws to the radiator top frame and the bottom chassis rail.

Small diameter pipe between header tank and engine

Overflow pipe secured using a couple of P-Clips

The bottom radiator hose was slightly more tricky to fit.  The bottom hose has three connections; one to the bottom of the radiator, one to the bottom of the header tank and one to the thermostat housing on the engine.  The connection to the radiator bottom outlet was made with a length of 35mm bore silicone hose (same as the top hose).  The connection to the header tank was made with a length of 25mm bore silicone hose. I needed to support the bottom stainless pipe roughly level to be able to judge the correct length to cut the required length of hose.  I erred on the side of caution and initially made the hose too long and cut it down 10mm at a time until the right length was achieved.

The connection to the engine thermostat was more involved.  Other builds I have seen have just used a 90-degree silicone hose bend between the thermostat housing and the vertical section of stainless steel pipe (the angle is slightly more acute than 90 degrees but the silicone hose gives some flexibility to adjust).  

I had ordered a 90-degree 35mm bore silicone bend thinking this would suit the purpose.  Unfortunately, I discovered two problems.  The first was that the leg lengths on my 90-degree bend were too short so when the bend was slid onto the vertical stainless pipe, it didn't reach the thermostat housing.  The second problem was that the diameter of the thermostat housing is 42mm and no amount of cajoling would get the 35mm bore hose onto the outlet.

My solution was to order a 38/35mm silicone reducer plus a couple of alloy 35mm hose joiners assembled as shown in the photos below. Ideally, I would have ordered a 40/35mm reducer but Merlin was showing it out of stock for 6-8 weeks and I wasn't prepared to wait that long.  You might ask why I didn't just do the whole section in 38mm bore hose, which might have been simpler, but as I had already bought the 35mm 90-degree bend I wasn't too keen on just binning it.

AK Bottom Radiator Pipe

My solution involves a reducer, some joiners and a 90-degree bend...

...all fully assembled

As installed on the car

The hose from Header Tank to the lower Radiator Pipe

The last hose to fit was the pipe from the header tank to the top of the radiator.  Unfortunately, I hadn't thought this one through fully; the routing of the pipe is quite tight and very dependent on the position of the wash/wipe water tank, which I had not yet ordered.  So there was another short delay in the proceedings while I ordered the second tank from AK Sportscars and awaited delivery.

Once it arrived I fitted it in the same manner as the radiator header tank.  I could then route the final silicone hose, fix a P-clip in an appropriate spot, and that is another job complete!

Routing of the final section of radiator hose

Not quite relevant to this post - but both bling tanks are in place!!

Engine & Gearbox Installation - Part 6 - Ancillaries

With the engine in the car, the last job to complete the installation was to attach the alternator and the power steering pump and fit the serpentine drive belt.

When I bought the engine, Kyle supplied a nice billet aluminium bracket set-up, which once I worked out which holes on the engine it was all supposed to bolt up to, went on quite easily.  There is a smaller bracket which supports the rear of the alternator which sits directly against the cylinder head, the larger front bracket is then set off from the engine block with a number of spacers.

Initial Fit of Ancillary Bracket

Somewhat oddly, despite it being listed as a part of the bracket kit, I didn't seem to have the lower idler pulley with my kit; it was all blister packed and there didn't seem to be a "missing" spot for it.  That created a short delay in proceedings as I had to order a new idler pulley from Summit Racing in the States (I did this to be sure I got the right one, which needed to be for a Z06 Corvette).  Once it arrived it just needed to be fitted with the 110mm M10 bolt supplied with the bracket kit through the pulley and a couple of spacers and screwed into a hole in the engine block.

"Replacement" Lower Idler Pulley

The alternator could then be fitted into place between the front and rear parts of the bracket and held in place with two M10x80 bolts.

The alternator is fixed in place

Then it was 'just' a matter of fixing the Power Steering Pump in place with the three M8x25 bolts supplied.  And with that, a five-minute job turned into a several weeks job...

The first problem was that the Power Steering pump that I had been supplied with the engine, which was a standard GM / AC Delco unit, did not have threaded mounting holes.  The fixings were meant to be much longer bolts that passed through the whole unit and were secured with nuts at the rear.  OK, so I could have bought some longer bolts, but the pump unit is a snug fit between the front and rear parts of the ancillary bracket which would have made it impossible to get any nuts on the bolts in any case.

Another AK builder, who had also got his engine from Kyle, and with who I had been in contact previously, had purchased a new pump from Summit and he had previously given me the details of this.  Figuring he might have encountered the same problems that I was having, I blindly went and ordered the same pump; a performance pump with AN fittings from Tuff Stuff.  This was a long-lead item from Summit and I had to wait several weeks for it to arrive.  Once it arrived, I was relieved to find out that it did have threaded mounting holes and managed to fix it in place on the bracket.

Tuff Stuff 6170ALB-2 Power Steering Pump...

...installed in place

At this point, I noticed my next problem.  The pump that I ordered has the outlet port on the bottom.  This is the high-pressure line and while I knew that I would need to get a new hose made up with an AN fitting to suit, it was pretty obvious that there was going to be insufficient room between the port and the bracket to accommodate an AN fitting and sufficient clearance to form a 90-degree bend (similar to the brake pipe in the picture above, you can not form a bend immediately behind the fittings; there will need to a certain straight length needed to allow the pipe bender to do its thing...).  This was confirmed in my discussions with Adam at Earls, who I had contacted to request a quote for a new high-pressure pipe.

I had two solutions.  Grind away part of the bracket to give clearance for the fitting or find another pump.  I went with the latter option but this time did a bit more research before pressing the order button. I thought a pump was a pump, but reading through the Tuff Stuff catalogue online, there are loads of configurations.  So this time I bought a pump with a top outlet and with threaded mounting holes and with AN fittings.  Summit was showing out of stock so I ordered via Ebay.com but that still took another 8 weeks to arrive!

Does what it says on the box...

...only this one has a top-facing outlet port!

The power steering pulley needs to be installed onto the pump using a special tool.  It's a press-fit but should not be attempted using a hydraulic press as that could damage the pump.  I bought a cheap tool from Amazon; this is basically a threaded bolt that screws into a thread at the end of the pump drive shaft with a nut/flange arrangement threaded onto the bolt.  The flange sits on the face of the pulley and then by holding the main bolt with one spanner and winding the nut down with another spanner, this presses the pulley onto the shaft.  The pulley is installed until the end of the shaft is flush with the front face of the pulley.

It's probably obvious, but the pulley needs to be installed with the grooved flange to the front; this is to allow a puller to grip onto the pulley in the event that it needs to be removed.  If you install it the wrong way around, you will need to take it to your local helpful mechanic to get it removed while he laughs at you; ask me how I know this...

Holley Power Steering Pulley - note which way round it goes...

Pressing the pulley into place...

...until the face end of the shaft is flush with the front of the pulley

I could then install the pump back onto the ancillary bracket; it needed a bit of wriggling to get the pump with the pulley into place with the tubular bracing of the AK Gen III chassis.  I could then get the bolts into place and tighten them to 15ft-lbs / 20Nm.

Finally, the pump is in place!

(Actually, I did have to take the pump out again as I had forgotten to torque up the bracket mounting bolt that is cunningly obscured by the pulley once the pump is in place.  I torqued all the bracket bolts to 25ft-lbs / 34Nm.)

Finally, I could get the serpentine belt looped onto the alternator, power steering pump, water pump, idler and crank, and using a spanner to pull the belt tensioner forward, slipped the belt fully into place and released the tensioner.

The serpentine belt looped into place...

...and over belt tensioner.

With all the faffing around with power steering pumps, that little job only took the best part of five months!!!

Exhaust & Headers - Part 2 - It's a Wrap

I plan on having the side pipes ceramic coated in black before the final installation.  Rather than have the headers ceramic coated, I have wrapped them to try and keep heat levels under the Cobra hood down as low as possible.

I decided to use Lava Rock Titanium Exhaust Wrap from Funk Motorsport, made from pulverised lava rock.  Apparently insulating the heat from the exhaust also helps to improve the flow of gases in the system which helps increase engine power output...bargain!

Funk Motorsport Exhaust Wrap - made from real volcanoes!

I bought two 15m rolls of 50mm wide exhaust wrap.  Each pack comes with five stainless steel tie clips although I bought another 10 at the same time - just in case...

I followed the Funk Motorsports videos on YouTube which cover how to use the exhaust wrap.  There is a "right" edge of the wrap which should be the exposed edge when wrapping the exhaust; I did get one pipe wrong and had to undo it and rewrap it correctly.

I used nylon zip ties to help hold the wrap in place - note LH pipe wrapped with the wrong edge exposed

All pipes are wrapped...correctly!

I could then cut off the temporary zip ties at the manifold end and replace these with stainless steel zip ties.  I found it helpful to grip the spare end of the tie with a pair of pliers and push on the locking tab with a screwdriver to help get the ties really tight.  The spare end was then cut off with side cutters and the end folded under to avoid any loose sharp edges.

Finished offside header pipe, top...

...and bottom

In theory, I could remove the nylon zip ties as the wrap should stay tight (if I have done it correctly!).  For the moment I will leave them in place (I trimmed the spare ends) as I will wrap all four of the pipes and the extent of the side pipe in the engine bay when I assemble the exhaust properly.

I then installed the headers onto the engine, this time with the gaskets.  I secured them using some ARP 12-point header bolts.  These are torqued up in two stages, working from the centre bolts outwards; the first pass was to 11lb-ft / 14.9Nm and the final pass to 18lb-ft / 24.4Nm.

ARP 12-point Header Bolts

As I anticipated, I did have issues getting the front header bolts into place.  The location of the vertical bracing tube prevented me from getting the bolts in straight enough to be able to get the thread to engage.  I needed to make a "small" dimple in the side of the tube with a ball pein hammer to give a bit of wiggle room.  But having got the bolt started in the cylinder head, it was quite stiff to turn and the proximity of the bracing made it impossible to get a socket or a ring spanner onto the head of the bolt (this wouldn't have been an issue with a normal hex head bolt as I could have used an ordinary open spanner, but those don't work on 12-point heads...).

Tactical dent in the bracing gave enough room to get bolt started in hole

I then gave all the holes a chase through with an M8X1.25 tap to clean up the threads; I was pretty surprised how much crap came out of the holes but after doing that all the bolts could be nipped up tight by hand before being finally torqued down. 

Cleaning up the holes removed a surprising amount of debris...

Manifold installed and all bolts torqued to specification

Fuel System - Part 3 - Deep Breathing

Next up on my job list was installing the air intake and air filter.

I purchased the stainless steel air intake pipe from AK; another bit of engine bay bling! This includes a couple of spigots to connect to the crankcase breathers so that any oil-contaminated air from the engine is recirculated back into the air intake.  It also has a hole underneath into which the Intake Air Temperature (IAT) sensor is installed; this is one of the sensors monitored by the Canems ECU.

Shiny intake pipe!

I ordered a standard GM IAT sensor from Billy's Speedshop via eBay.  I needed to clean up the hole in the inlet pipe slightly with a hole drill to get the sensor to fit.  This will be held in place with some polyurethane sealant.

Intake Air Temperature Sensor...

...installed into air intake pipe.

For the air filter, I went with a K&N RD-1450 unit.  This was basically the largest diameter but shortest height unit I could find with a 4-inch inlet flange diameter to match up with the AK air intake pipe (the short height is important as there is not a lot of room to fit the filter in between the intake pipe and the radiator). As well as providing increased airflow, the K&N units are washable and will last pretty much forever.

K&N Air Filter with oiled cotton filter element

The air filter was a simple slip-fit over the end of the air intake pipe and was secured in place with the supplied jubilee clip.

To attach the air intake pipe to the throttle body on the engine required a 102mm ID silicon Straight Coupling Hose (from Merlin Motorsport) and a couple of suitably sized jubilee clips.  These were torqued up to 6Nm as per the Samco recommendations and then checked again after at least 30mins to allow for any relaxation of the silicon pipe.

Filter and intake pipe installed - I even made sure the logo was level...

For the connections to the crankcase breaker pipes on the rocker covers, I used some 200 Series -8 braided steel line from Merlin Motorsports and some neat -8 hose finishers (which incorporate a jubilee clip) from Torques UK.  

Offside breather hose completed

The nearside hose was a bit more of a faff as the outlet breather pipe on the rocker cover faces towards the rear of the car.  This needed the breather pipe to turn 180 degrees; unfortunately the bending radius of -8 braided hose is rather large so an alternative solution was needed.

I used a couple of -8 straight female fittings and a -8 180-degree adaptor from Torques UK to come up with a suitable arrangement.  Unfortunately I couldn't quite finish off the install as I managed to misplace the final -8 hose finisher somewhere; no doubt it will surface once I've ordered a replacement...

My solution to redirect the breather pipe through 180-degrees

Somewhere in the garage, there is a stray hose finisher...