MkII Cortina Perana V6 racer

[Shauns]

Great Progress there,
Are you welding up the rear doors shut on the Tina ?

[KSF]

No, welding of the rear doors are not allowed in Classics, so they will be full doors on hinges and a latch at the back, door handle outside and so on. You don't need to be able to open them from the inside, just the two front ones. And all four can have the window glass replaced by lexan, no winder required, so much of the door internals goes too. Will post pics later of that set-up.

[KSF]

Back at Young's Body&Spray, things were still progressing and I got regular updates, but no pics to show for it. Happy that things were going forward with no major issues, I stayed on the Sierra, still hoping to get it running soon.

The exhaust branches I bought, being from a Cortina, was a straight fit on the engine and may have worked as is, was it not for the Sierra suspension where the anti-roll bar runs around the back of the engine. So, exactly where the Cortina's pipes aimed at to drop past the engine and bend backwards, is where the ARB sits. It took a bit of carefull measuring and planning to keep the cuts to a minimum, but I got the shapes altered to start the turn backwards a bit sooner and also managed to correct some of the imbalance in individual lengths.

With this top half tacked together and bolted to the engine, you get to crawl in underneath the car with the rest, including the collector box to go see where it needs to be.

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This was a fiddly bit of the job. Having a 4-poster lift or a nice deep pit like Rassie has would make this a lot easier. But like for must of us who work with a trolley jack and axle stands, you get the workout of crawling in and out of there a few dozyn times.

Once I had determined a good place for the collectors to sit and adding in the extra length I still needed to add to the branch overall lengths, I crawled in with bits of pipe and the welder to tack it in place.

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Yes, that is a nail tacked in place. The bit of pipe I had cut to length outside turned out to not fit properly and I needed at least two points tacked to keep it all steady and in place.

With this done, I took both off and to the bench. There in the decent light and space and with the operator right side up, I made up some pieces of pipe to properly fit.

No pics of all the individual steps, but here below one can see the parts added in. Where it is shiny is where new welds are and new pipe went in.

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On the one only about 40-50mm were added, on the other it was well over 100mm, around 150 or so I think.

[KSF]

Here was where the project took a bit of a turn. I was now ready to put the branches back on, but thought to first have a detailed look at the engine. It was running, but with so much tappet noise that it overwhelmed all else. It had not been maintained all that well. In fact, the whole car looked like it had seen regular and proper maintenance for much of its life, but then ended up an owner who did not take care of it at all. And then it stood for a long time.

Long story short, in the end I was not happy with the condition of the engine, just too much wear and you risk destroying it completely if you try and race it like that. So it had to come out.

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It is actually blue, just very dirty. It got dragged away and I found a spot next to another waiting for attention.

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This area has also been unkindly referred to as "death row". I'd rather think of it as the waiting room!

This put a small spanner in the works, obviously now it would not be so quick to get the car running. One could just do a quick build to get it running, but since a quick rebuild does not cost that much less than doing it properly, I decided to rethink my more immediate goals and targets.

Instead of just going over the car to get it mobile, I decided to rather just go over it piece by piece and get all of it right and hopefully right first time. Since I had built and campaigned the Sapphire and they are near as anything mechanically identical, lessons learnt from that car could be implemented.

I think next was to get the gearbox out and out the way too, but my next stop was to be suspension and brakes, leaving the drivetrain for later on.

Before the suspension got taken out, I decided to copy the Sapphire's strut tower mods. On that car I learnt after some experimentation that it liked a bit more castor than what you can gain at the bottom with shims and washers. I was still using full diameter springs and planned to do so again in the Sierra, but even then, they have a fair bit of free space in the turret. So I set about modifying the top mounting.

Note here: It is now allowed in Fines to use coil over suspensions and even camber plates are getting to be more common and accepted. It did not use to be the case and in many people's minds it should still not be. But, it is technically legal.

So here below is shown the top already cut out. There is some carefully measuring and drawing out required. Essentially, you draw an off-centre circle. It is off centre by half the amount of castor (and in this case camber) you wish to gain.

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This is (obviously) done for both side.

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Then the section you have cut out gets turned through exactly 180 deg. I leave the strut in place for this, it helps hold it in place and also helps keep it aligned at the angle required. Once happy with where it sits, it gets tacked in place. I used my Invertor welder and stick here again.

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While doing these tacks, I used a wet cloth (or maybe it was an old towel) to cool the tacks down as soon as possible. The top of the strut sits in a rubber mount which would otherwise get damaged and probably catch fire.

[KSF]

Then, with the tack welds in place and secure, the struts gets removed, as well ass the rubber mounts (shaped like fat round donuts). Then the full welds get done. These are quite important welds, so one has to be happy they are full strength. I had a go with stick, given that the metal there was still in excellent condition and also a decent thickness (I would guess around 2.5-3mm).

I did not risk trying to put lengthy runs in, but rather turned the welder's amps up a bit (to ensure proper penetration and fusion) and did lots of shorter runs, giving some cooling time between them. Below is what it looked like before clean-up. The black was the result of some paint that caught fire I think, cannot clearly remember.

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With these welds I made no attempt to cool them rapidly, but rather left it to cool at its own rate. Also, they were not all done in one go, but rather in 3 of 4 separate sessions, swopping between left and right turret.

That all done, a clean-up with anglegrinder sanding disc and some etch coat.

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And finally some white paint. It looks very bright here and not a match, but it is only because the engine bay is still dirty. Clean-up it is quite close.

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With that the fabrication part of getting the suspension sorted is done. The rest gets done on the parts themselves.

[Waterhond]

Hi KSF,

This thread is fantastic, fantastic !

Why did you lengthen the branch tubes ? Was it for fitment purposes ?

I'm asking because they are not equal length anymore, what would the impact be ?

Pieter.

[KSF]

Hi Waterhond and thank you for the kind words.

No I lengthened them purely to get the overall branch lengths within the tuned length range, they were well short of that in the original form. Lengths varied from the shortest at about 550mm to 600 and then one at some 780mm. Especially the left bank was on average much less than 600mm long. For this type of engine and usage you need at least 700mm to get within range, 750 or so closer to ideal.

Interesting question about the equal lengths. I got these to within 25mm of each other which is about as good as you will need to get. First thing is that they are then all in the optimum range for pulse tuning, a spin off benefit is that the engine also runs a bit smoother. I also like the smoother sound you get from that. There are some professional engine builders who deliberately make the lengths unequal (between 50 and 75mm variation), they maintain that it spreads the peak power across a bigger rev range. It sounds good in theory, but I have no first hand knowledge of that.

As the branches were supplied, they may be too short for pulse tuning, but they are still a decent freeflow design with its benefits. From OEM to freeflow you get maybe 8% or so extra power, from there to tuned length peak power might increase a couple percentage points, but the main benefit is in the shape of the torque (and therefor power) curve.

[KSF]

This was now around end of April, going into May of this year (2016). Still roughly on track to get the Sierra running by winter and the Cortina arriving back just about when the Sierra is done.

I got some more update pics from Young's Body&spray. They now had completed the basic filling and shaping of the flares and also my weld repairs on the mudguards.

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Here the mudguard and flare is already in a new type of primer/filler. The product is new to me, it is not the old style of sprayfiller from way back and replaces the MS primer of more recent times. Body work specialists could maybe comment on that.

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Needless to say, seeing them like this was quite exciting for me. For the first time now you could see what the final product will look like.

With the mudguards done, work on the rest of the car could continue. I have some interesting video clips of the finer work of massaging out some minor dents with a slidehammer that welds itself to the panel as required and so on. (Sorry, I am too IT challenged to master the art of posting video clips!)

Here below the rear door repair is progressing well.

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For the Cortina project this was very positive and good news. With the work they had done, no nasty surprises of botched old repairs or hidden rust came out and the body work was nearing the final phase of a thorough sanding of the remaining areas where no (or limited) work was required.

[Mustang Sally]

Hi KSF

I agree with Waterhond, a most addictive and enjoyable thread!

Thanks for all the interesting info. Following the rest with great interest.

[KSF]

Back home the Sierra was now without drivetrain and suspension. The shocks I had sent off to Ian Glass to do his thing. He is very well known around here for the work he does on shocks and suspensions, not just for racing cars, but road cars as well. The internals of shocks can be one of those dark arts that few fully understand, so usually I just describe to him what I plan with the car, give a list of details such as the car's mass, wheel mass, spring rates etc and he does his mods to internal valving and oil used. In this case I could give him some feedback from the Sapphire and we agreed on a slight adjustment to the compression rates, rebounds left as is.

On this car I wanted to keep the suspension rubbers a bit simpler than the Sapphire where a lot of work and time was spent. Between Rowley Stanton (Motordrive) and myself all of them were custom made items from various grades of poly prop. Some areas I also made completely solid. It probably worked well enough, but we also found that the gains compared to the other cars in our "team" might not have justified the effort and expense. So for this car I simply ordered a ready made set of poly bushes from a supplier in PE. I got his details here on the forum from GavinRS (their name slips my mind for the moment, something -tech. Wheel tech? Suspensiontech? I can find it again if someone needs it).

Here below a pic of the front suspension components with the bushes fitted.

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They go in with no further mods, except the lower control arm mounting point on the cross member gets redrilled to get more camber. The ARB is from a later model Sapphire and is about 2mm thicker than the Sierra's own one. Not seen here is the additional ARB that may be clamped to the underside of this one. I might not need it on this car since I am using different springs, but it might be added later. Will see once it has run.

It leaves the suspension springs. Since I wanted to stay with the full diameter springs, you cannot just go and buy the spring rate you want. It is more challenging than that and perhaps also unnecessarily difficult, but it appeals to the engineer in me to find the right springs that will give me the required spring rate and ride height. You can sit and do lots and lots of calculations with various combinations. Also scope to frustrate yourself navigating what is readily available. Yes, a simpler shortcut is to get hold of a spring manufacturer with your specs and he'll make what you want, or alternatively to buy a set of springs and hope they are what you want. I found many (if not most) of the aftermarket spring kits (and that includes the now very popular "coil-over" kits) are not much more than "drop" kits and not much thought goes into the spring or shock rates. There are exceptions to that of course, I am not knocking the lot of them. Just saying good luck sorting out which is good and which is sh.., uhm, not so good.

Anyway, here below a pic of a page I created with springs and spring rates.

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There are plenty of on-line calculators for coil springs. This was not with one of them, but the results remain the same (roughly!).

And here below the four springs after selections, some modification and here just prior to some paint to look prettier.

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I am somewhat hesitant to fully describe the modifications I made to them. Not to keep secrets, but rather because it is a field where a lot of botching and butchering takes places, some of it dangerous, some of it just internet nonsensical babbling. So I will just say they started out as a popular car's rear springs and after some rework, they now look like this.