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Coalnotdole's Scimitar - Machining work: Speedometer Drive Unit 12/4/19


coalnotdole

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Hmmm... He has carefully avoided mentioning the size of the exhaust valves in the advert !

 

Unfortunately, his description of the engine as a "collection of expensive performance parts bolted together" still rings true.

 

Considering what you've found so far, perhaps it's a good idea to measure combustion chamber and piston top volumes and calculate a static ratio yourself. You may well find it above or below 11:1. If the ratio was too high, I would expect clearly visible detonation damage. Unless the engine management system has been running the engine too rich to defend against that, which could explain your findings ?

 

The engine has definately been mapped to run rich but I think this is more due to needing a "safe" margin to prevent lean running. I had planned to introduce wideband 02 sensors, but will now look to to increase the amount of inputs which will give more precise fueling. I've bought a Knock sensor too. I'm hoping Dave will be availavble soon and we can sort the wiring loom out As it will need lots of cables adding to run these additional sensors. Once the engine is backtogether it will have to go to a rolling road for another mapping session and to set the sensors up.

 

There is a future plan that might allow Sequential ignition insead of wasted spark, This will depend on creating a camshaft position sensor from an old distributor mated to a modern ford sensor / body. Its probably more of a medium term project. As it will require an alternative concept for the coil packs.

 

Any evidence of work on the combustion chambers?

 

I'm wondering if they were modified to enlarge them, which could give the missing 100cc & reduce the compression ratio.

 

 I did consider the possibility someone might have done that but I can't see any machining marks, It would also have to have been done before the engine was balanced.  Also the correct 3.2 pistons are available from Burtons : http://www.burtonpower.com/accralite-forged-piston-v6-essex-96-25mm-3161cc-10-2-1-fv100-96-25.html It would have made more sense for them to have used those...

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I'm watching with interest. When I saw the first strip down pictures my first thought was what Captain Furious said. I used to mess around with SBC's and trying to explain to even 'experienced' people about the concept of removing a similar amount of material from an inlet manifold after skimming heads was very difficult sometimes!

Good luck with it, I hope getting to the bottom of the issue isn't too costly.

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I feel your pain. When you get to this stage it gets difficult to accept anything you've been told about how that engine was built. That monster compression ratio is one possible explanation for the heat, 11:1 is squeezing it very hard so the bang must have been huge. That rejects an awful lot of heat to the coolant but also through the exhaust valves.

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Cheers all, I can't pretend the last couple of weeks haven't been very frustrating... Ultimately as its a daily I get a lot of 'why don't you chuck it in and get something modern" type comments usually at work. I'm quite resistent to them as I find new cars to be vastly boring and the GTE is normally very capable...
 
So far this year with this car alone I've had a real run of bad luck and had to deal with:
 
Hitting a deer on a dual carrigeway smashing the front end up...
 
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Which also bent a vertical link...
 
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The speedo drive gear melted causing the speedo to stop working,

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All the wires dropped off the back off the ignition switch while investigating the speedo fault. leaving me stranded until I could work out which wire went where... They are mostly white I had no test lamp with me.

The windscreen exploded one morning on my way to work, I spent an hour in the car park taking it out and drove home without one... Its toughened, not laminated and shattered into a million pieces shortly after this picture was taken....

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The overdrive seems to be a bit intermittent

And the interior light has stopped working...

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11:1 does seem a bit radical to me, I had a V4 which had had the heads skimmed to 10:1 and that was keen on blowing head gaskets. Eventually the problem was solved by a fuel line coming off the carb and the whole lot going whoooof.

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  • 2 weeks later...

Reassembling The Heads:

 

When I took the heads off I rang almost every machine shop I could find in the southeast who worked on engines / cylinder heads. I had hoped to get the exhaust valve seats enlarged to take oversize valves but everyone I spoke to did not want to do the work for fear of damaging the heads. I even spoke to Burtons (who sell the oversize valves) but they no longer do any machining in house and generally supply oversize heads on an exchange basis. So I'm sticking with the standard exhaust valves on this set of heads.

 

So In the end the heads went to Saunders Motorworks in Hampshire as they offered the best turnaround time, even then it took over a week to get the work done. They have fitted the new burtons valve guides, Recut the valve seats and drilled and tapped the to take screw in rocker studs.

 

The new guides stand a little bit proud in the port but they are at least smooth.

 

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Machining marks on the head suggest that there has been some work done in the past to the face where the inlet manifold sits.

 

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Guides tops and the threads cut for the screw in studs,

 

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I then lapped the valves in.

 

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With the heads clean it was possible to see heat discolouration between the valves. To my mind this confirms that there has been some form of pre-detonation occurring, The heat marks are present on both heads not just the bank where the gasket had failed.

 

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Heads reassembled,

 

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Head Replacement:

 

I spent most of a morning getting the crowns of the pistons as clean as I could and vacuuming out the debris. I've gone for a Victor Reinz Head Gasket in the end as I'd already bought them and the fancy Cometics were eye-wateringly expensive. If I have future problems, I'll consider getting a set.

 

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Instead of the mismatched head bolts that came off I'm going to use a set of ARP head studs. They come with a recommended torque of 110 lb ft A long way above the 65-70 lb ft specified in the factory workshop manual. (I am aware that Ford increased the torque to 90 lb ft at some point during production)

 

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The torque is now so high that my Norbar torque wrench is a bit under spec and I've used the Large Britool one my dad bought at the car boot a few years ago. £25 well spent :)

 

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Close up of the studs:

 

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Inlet manifold waiting to be refitted, I used a few dabs of superglue to hold it in place and no sealant...

 

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With the inlet on the studs and rockers could be fitted. I'm not 100% sure which camshaft is fitted so wasn’t sure what to do regarding valve clearances, In the end I went for 0.36mm on the inlet and 0.41mm on the exhaust Measured cold. I will look at them again when I fit a set of alloy rocker covers in a few weeks’ time.

 

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The Yella terra rockers have a slightly different ratio 1.5:1, giving them slightly more lift than standard rockers which are 1.4754:1 I bought these on eBay a few years ago, for a fraction of the price of a new set… http://www.burtonpower.com/street-terra-roller-rocker-kit-cast-alloy-ford-ford-essex-v6-fv461.html

 

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Final picture, Almost back together...

 

 

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I really do appreciate all the details you're posting fella - luckily I've never had to do more than a 'refresh' on any motor I've had so far - so I'm still terrified of a full on rebuild/upgrade etc...

To stick with it after all the back n forth - sticking with the 'proper' Scim engine is fantastic. Very best of luck with the ongoing trials n tribulations, I know I'm among a large group of watchers

 

How are you progressing with the SA injection setup?

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How are you progressing with the SA injection setup?

 

Glad you like the writeup, I probably include too many photos but as I've got them I sort of thought why not.

 

The EFI project has been a bit of an experiment, there was alway going to be some room for development. I'd not expected to have the engine apart so early. but in some ways its been good to know that it does still come apart fairly easily. I had been concerned that all the throttle bodies would have to come off to get to the inlet manifold bolts. Fortunately I was able to get them out without disturbing any of the injection setup.

 

I wish I'd sat the samcor manifold & plenum on there for a look while i had the inlet off but it was wrapped up in storage and I did not really have time. I've got two other 3.1 essex blocks which would make a reasonable base for the SAMCOR setup, or alternatively I could fit it to my Scimitar GT which has sat in the garage unloved since I started playing with the GTE's engine. The expense of buying another ECU has prevented me from doing more with it (£850-£950.)

 

The downside of all this attention the GTE's engine is getting is that I'm not getting any other jobs done...

 

The Rebel Van needs an engine rebuild,

Both Scimitar GT's need MOTing,

The xflow rebel still needs a cluch, MOT and front end.

The GTE is part rubbed down for new paint after the deers incident and is desperate for at least some primer...

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