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Time for a top end rebuild... part 2

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Finished running in the new 3.4 pistons and cylinders last week – I went for shorter more progressive run-in than last time as I didn’t want any risk of glazing the new bores. I used a good quality 15W40 mineral oil and did most the break-in over two ~3hrs drives – engine fully warm and progressively increased speed and load.

 

I did a hot leak-down check after ~550miles and all cylinders were between 1% and 2% leakage :) so I’m pretty happy the bores are bedding in well. Did the post run-in service and check over the weekend – sump plugs were clean and the oil looked fine. A few of the tappet clearances needed closing a fraction. Now refilled with fully synthetic 10W50.

 

The engine pulls well and there’s definitely more torque than before – over 5000rpm it’s harder to tell as I hadn’t driven it for 6months – certainly feels quick, there’s also a great induction noise with the MAF and big bore throttle body combo.

 

The only issue I’ve had has been a part throttle hesitation or stumble between ~2000rpm and 3000rpm. It’s possible to drive around it most the time but can annoying if you’re driving in traffic (or trying to drive sedately..). Some days it seems a lot worse than others but there seems to be no correlation to weather etc. I think it may have begun pre-rebuild - but was far less noticeable then.

  • I’ve tried replacing my MAF kit with the original VFM (twice!) and it made no difference.
  • I’ve been through the ignition system and I’m fairly confident it’s nothing there – I replaced the HT leads as a precaution as they were >10years old and it made no difference. Also checked the distributor cap and rotor.
  • I've checked the engine earths.
  • The flywheel speed sensors and cylinder head temperature sensor have all been replaced in the last 5000miles.
  • Spent some time checking fuel system – fuel pressures are fine, pressure regulator and pump have both been replaced in the last 5000miles.
  • Tried another DME relay and also checked the altitude sensor – all fine.
  • I’ve pressure check the inlet system for leaks multiple times.

This has left me a bit stumped – I’ve run it with a Lambda meter fitted and it shows its going lean briefly (about 1 AFR) when it stumbles… so I’m now back looking at the fuel system.

 

As I’ve come this far with the engine I’ve decided to invest in a new set of injectors – it’s been a pain sourcing these, so far three have arrived and I’ve fitted these on one bank; apart from making the idle a little smoother there’s no change to the hesitation. It’ll be another week before I get the remaining three injectors (1 from US, 2 from Germany!) to fit on the other side - keeping my fingers crossed this will sort it.

 

I’ve read a load of threads on here and Pelican re hesitation issues and I think I’ve covered off most the things – any other suggestions or ideas welcome !

 

Cheers

Matt

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Great thread. Thanks for documenting it. If you have to rebuild with new P&Cs the 3.2 to 3.4 Build has always weemed you a good idea to me. SO much confusing and conflicting info on what compression is safe with single plug though.

 

How did it all turn out. Did the lean problem ever get fixed and has it been Dyno'ed ?

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As I’ve come this far with the engine I’ve decided to invest in a new set of injectors – it’s been a pain sourcing these, so far three have arrived and I’ve fitted these on one bank; apart from making the idle a little smoother there’s no change to the hesitation. It’ll be another week before I get the remaining three injectors (1 from US, 2 from Germany!) to fit on the other side - keeping my fingers crossed this will sort it.

 

What injectors are you replacing it with Matt? Standard Bosch 3.2 injectors?

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Great thread. Thanks for documenting it. If you have to rebuild with new P&Cs the 3.2 to 3.4 Build has always weemed you a good idea to me. SO much confusing and conflicting info on what compression is safe with single plug though.

 

How did it all turn out. Did the lean problem ever get fixed and has it been Dyno'ed ?

 

Its all running well thanks - now coming up to 2000 miles on the new build. Its definitely quicker than it was as a 3.2 - I've not had a chance to run it on a dyno yet but hoping to after summer hols.

 

I'm now running a best guess full load tune; I've erred slightly on the rich side to be safe and gone a couple of degrees less advanced than Steve Wong's 98RON chips - this is still quite advanced over stock though. Switching between the stock Porsche ignition curve and the one I've created makes a difference you can really feel - especially over 4000rpm :D. I'm sure there's bit more to go but I want to do this on a dyno.

 

I've been looking into fitting a knock sensor kit for when I do the final ignition curve optimisation - I know which is the hottest cylinder from the exhaust thermocouples I've been running, so this is the one I want to monitor. Challenge is to find a decent mounting point - been looking at the 993 knock sensor mounts and also some that guys on Pelican have fitted on 3.2s. With the benefit of hindsight I would have drilled and tapped some mounting points before assembling the engine...

 

Re the lean hesitation problem - its still not gone completely, even with a new set of injectors (still trying to explain that one to my wife!). I tweaked the calibration a little at part load to try and fix it but didn't want to do any big changes until I've got it on a dyno - this improved it to the point where its no longer noticeable in warm weather so I'm just enjoying driving for now.

 

 

What injectors are you replacing it with Matt? Standard Bosch 3.2 injectors?

 

Hi Alex - yes stock Bosch injectors, managed to gather a full set of six together from various places in UK, US and Germany. From what I've read up they should have enough headroom for my engine. They've made the engine run smother than its ever done before - given how much I've done to my engine its also peace of mind knowing the injectors are all new rather than ~30years old.

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Great thread, love the detail and results.

 

Mind me asking, what price did you find the injectors for. May need 1 or 2 for my 3.2.

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Great thread, love the detail and results.

 

Mind me asking, what price did you find the injectors for. May need 1 or 2 for my 3.2.

ive just ordered a set of these, which are close enough to the standard '158' injectors (I hope)

 

http://m.ebay.co.uk/itm/New-Bosch-Porsche-911-Aircooled-3-2-Fuel-injector-x-6-/161759894092?nav=SEARCH

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Great thread, love the detail and results.

 

Mind me asking, what price did you find the injectors for. May need 1 or 2 for my 3.2.

 

Cheers. I think the average price I paid was ~£125 per injector, the cheapest was from the US at ~£110 and the dearest ~£135.

 

ive just ordered a set of these, which are close enough to the standard '158' injectors (I hope) http://m.ebay.co.uk/itm/New-Bosch-Porsche-911-Aircooled-3-2-Fuel-injector-x-6-/161759894092?nav=SEARCH

 

 

Just had a quick look - those are Bosch 0280 150 352, specs below versus the stock 0280 150 158:

 

injector%20comp_2.jpg

 

 

The 352 injectors have a higher maximum operating pressure, but similar performance at the reference pressure:

 

Max flows at 3bar: 185.3g/min versus stock 181.7g/min (better to be on the high side than low)

 

Spray angle is 21 degrees rather than 18 degrees - can't see this making much difference

 

Distance between the two O-rings is 1mm less - I'd hope there's more than 1mm tolerance on the sealing in the rail/manifold

 

Will be interested to hear how you get on with these.

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May not be installed for a while yet, however do you have a comparison with the the 364 injectors I currently have fitted? Wondering if there is enough of a change between 352 and 364 to warrant a remap, hope not!

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May not be installed for a while yet, however do you have a comparison with the the 364 injectors I currently have fitted? Wondering if there is enough of a change between 352 and 364 to warrant a remap, hope not!

 

Here you go - this was the only injector that ended 364 that I could find, not sure why the type and OE part numbers are different. Looks like the flow numbers are identical between the 352 and 364 :)

 

injector%20comp2.jpg

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I would expect 99% of us would benefit from new injectors, but at £110+ per injector, it is ridiculous money! :( Bet the BMW or Ford nearest equivalent are £25 each from the same manufacturer! :smash:

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Here you go - this was the only injector that ended 364 that I could find, not sure why the type and OE part numbers are different. Looks like the flow numbers are identical between the 352 and 364 :)

 

excellent, should be a straight swap then . Only reason I'm swapping as the 364 are refurbed, whereas the 352 are brand new from the factory and bought a month ago according to the seller. I recall 'scarceller' on Pelican recommending new versus refurbed due to the electrical coil inside the injector usually not being touched during the refurb.

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we could really do with a set of these 352's being tried in a 3.2 engine. Could be very useful to know they work properly without any issues.

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I’m resurrecting my old thread as I had an oil consumption issue develop after this second rebuild that I thought others might benefit from knowing about. Its a picture heavy update!


Since doing the 3.4 rebuild I’ve done around 3,000 miles – what came as a surprise though was oil consumption increasing from ~1500 miles onwards until it had reached equivalent of 1ltr/1000miles…. I’d did leak-down checks every 500miles or so and it showed the cylinders were bedding in nicely – all sub 2%. So the oil consumption issue was mystery – it then started smoking after start-up, particularly if it had been left to idle for a while before key off – both of which made me start to think there was an issue with the valve stem seals. I did a borescope check of the cylinders and it showed bores were good but there was some oil sat in the cylinders. I also dropped the exhaust and saw what seemed to be oil coming from the valve stem:

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So I decided to pull the engine out again - I treated myself to a PVC tile floor in my garage first as I’d got fed up with flaking floor paint and concrete dust:

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Better safe than sorry - some sort of proper vehicle lift is definitely on my wish list still

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I’m getting quite slick at doing this now – engine was still warm in photo below!

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I got myself some insitu valve spring compressors from the US – they’re nice bits of kit, happy to loan them if someone else finds themselves in the same position.

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I found anything >75psi is sufficient to keep the valves firmly closed whilst your compress the springs. Also need a set of stem seal removal pliers in order not to risk damaging the valve stem.

I didn’t want to take any risk with the new steam seals so I went for genuine Porsche – they cost me more than the entire top end gasket kit I used last time. I think this is the key lesson learnt for me – I suspect the gasket set I used, although labelled ‘Elring’, was a poor quality copy - some gaskets were missing and some O rings were the wrong size… I should have thrown it in the bin at that point :banghead:!

Whilst the engine was out I made the ‘mistake’ of checking ebay for 964 cams and a set happened to come up at sensible money ;) So in the usual 'while I’m there mode' I got these:

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On closer inspection one of the 964 cam lobes had some significant pitting :o  it looked like a rocker arm had unevenly loaded one side of the lobe. The seller wan't interested in discussing the pitting...

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I ended up sending the cams to Pipers – they gave the pitted cam a ‘lick’ – removing just 0.15mm to clean up the pitting, fortunately they have the 964 profiles in their library:

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They also removed the redundant PAS drive from the other cam:

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I then started putting it back together – whilst setting the cam timing to 1.26mm I found it hard to get repeatable numbers… even with the timing chains clamped tight. I removed the rocker arms again and measured the bushes – the best ones were at the max wear limit but the worst were significantly higher. So the I spent the next month sourcing rocker bushes and getting these fitted, bored and honed (rocker arm bush refurb).

Finally rockers ready with new shafts and O-rings:

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With the re-bushed rocked rockers it was easier to get consistent valve lift measurements. After many attempts I managed to get both side bang on 1.26mm lift:

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The only other potential cause I came up with for the oil consumption was blocked crank breather pipes – when I took the engine out both large diameter breather pipes had a significant amount of gunge in where they’d drooped into a U-shape - there’s no support bracket on my MAF kit. So I’ve made up a temporary tin bracket to do this – if it helps then I’ll make a proper one out of aluminium:

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I put the engine back in last week and its running well – no sign of using or burning oil at all – so I’m hoping that’s it fixed. I’ve had a quick look at the old stems seal with a magnifying glass and the thin sealing lip looks very rough, in places its seems to have come away completely. I’ll see if I can get some close-up pics – including the manufacturers markings. Last time I buy a cheap gasket set.

I haven’t pushed the engine hard yet as its need re-calibrating for the new cams…. I’ve bought a Canems ECU for this as I haven’t got willpower to update the old Motronic maps again! 

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I’ll start another thread on the Canems system. I'm aiming to run it with closed loop Lambda feedback via an Innovate Lambda kit - once this is working I hoping to delete my extra MAF controller... whilst retaining the MAF inlet.

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Great job and attention to detail.   

Can I ask how much piper charged for sorting that lobe , I have a spare pair of 64 cams one with very minor pitting that I may wish to use one day . 

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7 minutes ago, Henry said:

Great job and attention to detail.   

Can I ask how much piper charged for sorting that lobe , I have a spare pair of 64 cams one with very minor pitting that I may wish to use one day . 

Thanks Henry.

Piper charged £75+VAT to lick over all lobes on one camshaft - it took them a little while, but quality of work seems very good. I was surprised how little they had to grind off to clean it up - good thing is it meant no re-hardening required.

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Hmm sounds a good option  re cams    ,good luck with  mapping will be good  seeing the result of the new cams .

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Just caught up with this.

Really nice work (again!) + your garage is starting to look like an operating theatre. How did you not get scrape marks and oil all over the floor!!

Good luck with the run-in miles. Hopefully nailed it this time.

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Any excuse to drop the engine again Matt :rolleyes:

Good work sir + 964 cams are a good shout.

Tempted to do some engine modding this winter myself!

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On 6/13/2017 at 11:51 AM, Lesworth said:

Matt - what floor tiles did you use and was the floor underneath totally flat?

The tiles are PAF Tektile Embossed 7mm: http://www.paftektiles.com/all-products/#!

The 7mm ones are forklift rated so I figured they'd be fine with trolley jacks etc. 

The concrete underneath isn't great - it was damaged by rain and frost just after laying. I leveled the most uneven bits with heavy duty self leveling compound before laying the floor - my trolley jack had worn two tracks down the middle...

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Laying the tiles is very quick until you get to the edges - I tried cutting the tiles with a knife but they're really tough. I found a decent handsaw was best in the end.

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I got carried away and used ramp pieces as matching skirting - this took ages so I probably wouldn't recommend it! 

I'm chuffed with the end result - its made it  much better to work in - especially the lack of dust!

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I've been using trolley jacks straight onto the tiles and there's no damage so far. Axles stands do leave an indent in the tiles - but it seem to go after a while. I'm using some tile off-cuts to spread the load under these now.

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Looks great. Dust is my main issue and the floor has lots of trowel marks so isn't level.


Sent from my iPhone using Tapatalk

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Looks really the business. I used epoxy two-pack green paint on mine and so far it is holding up really well.....time will tell though in the long term. I really made a point of neutralising the concrete with acid-etch first tho', then following the manufacturer's instructions.

David. O

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