The Manhattan Project

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rhd racer
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Re: The Manhattan Project

Post by rhd racer »

AndrewSlater wrote:General concensus is that the meters tend to show a little lean in this configuration at low rpm as there isn't enough exhaust pressure to keep some air from re-entering the exhaust
I have a fix for this issue Andrew. You can blank off the rest of the exhaust with a rag to allow you to get sensible readings at low revs, thus stopping the air re-enter. It was suggested to me by Wayne Schofield when he mapped my Boxster race car. I had been having problems getting it to pass the emissions on the MOT, despite new O2 sensors and cats (we basically had to rev the knackers off it!) The reason being that on a Boxster, the tight bends by the tailpipe prevent the exhaust sensor going far enough up the exhaust to stop the ambient air cocking things up. He put a rag on over the pipes and the reading came back to bang on. Different issue, but the same solution perhaps

By the way, the car looks beautiful

Hope that helps!
Regards
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93 964 C2
99 Boxster 2.5 > 2.7 hill climber

71 914/6 3.0 - gone

'You see Paul, hill climbing is like making love to a beautiful woman. You get your motor running, check your fluids, hang on tight and WHOA..30 seconds later it's all over!' Swiss Tony
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AndrewSlater
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Re: The Manhattan Project

Post by AndrewSlater »

Thanks for the help Wayne.

I might try the rag tip on a stationary test to see what variation I get, but am looking for a more permanent solution to allow me to do some road trials. My plan is to fabricate something that won't fall off mid drive.

I've realised that I have recently introduced a fault on the car. A few weeks back I noticed a small fuel leak, which at first I thought was around the cold start valve, so I battled to remove it from the air box so that I could tighten the fuel line fittings. On refitting I realised the leak was still present and spotted it was actually on the TAV line, which was an easier fix. Unfortunately when it was all back together I spotted the inner o-ring from the cold start valve housing had dropped out during the work. At the time I decided to leave it alone as I doubted much fuel could escape from the second outer o-ring. However I have now realised that the main purpose of the inner o-ring is to stop un-metered air entering the air box. This could explain the lean running.

Long story short, I battled removing the cold start valve again yesterday to fit the errant o-ring.
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
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Re: The Manhattan Project

Post by AndrewSlater »

Before trying to optimise the mixture, I decided to perform a valve adjustment to make sure everything is bang on correct. Also the engine seems to have become a little noisier of late, especially the right bank so seemed a prudent thing to do. The Wayne Dempsey book suggests you do this after 500 miles on a rebuild, whereas my car has only done 300 miles or so since I rebuilt the engine. However it has also had many hours of tinkering and idling etc.

I checked the values first using my dial indicator, and my calibrated hand.

Image

Here are the results

CYL IN OUT
1 0.15mm 0.25mm
6 0.125mm 0.25mm
2 0.20mm 0.25mm
4 0.35mm 0.13mm
3 0.23mm 0.30mm
5 0.35mm 0.45mm

So in summary they are all pretty slack, and we won't talk about bank 5, but I am guessing that's where a lot of the noise was coming from.

Whilst there I started to check the torque setting on the cylinder head bolts, but everything looked good - nothing loose.

So all valve reset relying on feeler gauge, dial indicator and calibrated hand and double and triple checked.
Hopefully this alone will make some difference.

Whilst the covers were off I also repainted them with high temperature paint again, detailed the Porsche scripts back to metal and high temperature lacquered them all.

Now ready to go back on.

Image
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
911hillclimber
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Re: The Manhattan Project

Post by 911hillclimber »

Will you re-set those clearances with the 4 thou feeler gauge? Really hard to get a good feel without the correct mini blade tool.

Those gaskets are ace, never had a leak with them, plain ones always leaked.
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Re: The Manhattan Project

Post by AndrewSlater »

Yes all valve clearances set using the SirTools feeler gauge, the dial gauge and my calibrated hand. The gauge was difficult to use when the engine was out, now much more of a pain.

I've also replaced the spark plugs ( gone for a hotter variant again for now ) and I even indexed them all ( not that it's going to make any difference ).

The bottom covers with the silicon bead are definitely very good, but probably a bit of a waste as I have to do all this again in another 500 miles or so.

Whilst I was refitting the missing o-ring from the cold start valve, I also investigated why the throttle body butterfly would occasion bind and not quite return to the no throttle setting.
I thought possible the helper springs weren't up to the job, but it turned out that the TAV was slightly misaligned. Now it is all square it snaps back every time very smoothly. Hopefully another niggle resolved.

Having dropped the oil from the oil tank before taking the cam covers off, I decided to refill with new oil ( despite the old oil being pretty recent ). Hadn't appreciated that I had dropped about 7 litres of oil, so didn't have enough Valvoline VR1 to refill, so currently awaiting delivery of some more oil.

So while the rear was up on axle stands got the chance to go underneath and give it all a good inspection and clean.

Image
Last edited by AndrewSlater on Thu Jun 11, 2020 8:15 pm, edited 1 time in total.
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
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Re: The Manhattan Project

Post by Cortina »

What is indexing a spark plug ??

OK - Google sorted me ................ never come across that , never heard of it , and better not to say what the engineer in me thinks of it !!
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jb
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Re: The Manhattan Project

Post by jb »

You may have wanted to drain the oil for other reasons but I thought ought to say that if you want to do the valve clearances without draining the oil then just jack up the side you want to do before taking the cover off and you will lose very little oil.
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Re: The Manhattan Project

Post by AndrewSlater »

Yes the engineer in me doesn't think I'll get much benefit from spark plug indexing but it was quite quick and free.

The tip about jacking a side at a time so as not to have to drain the oil tank is worth remembering.
Even draining the oil tank the covers dripped enough oil to spoil my day :roll:

Still waiting for the delivery of the oil.
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
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Re: The Manhattan Project

Post by AndrewSlater »

I was expecting this post to read that the oil finally turned up and that the car started great, the mixture was spot on and and it drove like stink... however that didn't quite happen.

The oil did turn up but I struggled to get the car to start even with the hand throttle. When it did start the AFR readings were as previous, but the car didn't seem very happy.

I started to think I had introduced a fault somewhere, and concluded that I must have introduced an air leak with the re installation of the cold start valve o-ring. So I decided to remove it again. Whilst it was off I decided to check it was working. When first installed I remember manually energising it and it all worked fine, but I don't ever recalling testing it in situ with the cars electrics. Sure enough it didn't work in situ. After much head scratching it turned out that the two connections to the thermo-time switch were reversed. All the text I had read had said that you couldn't get it the wrong way around as the terminals on the switch are different sizes. However my wiring loom has the same size spade connector for both the thermo-time switch heater element and switch hence the mistake. So in effect if I pulled the hand throttle level then from cold I was shorting out the starter solenoid to ground. Might explain the few instances were the starter didn't always engage correctly. :roll:

Its good to find faults like this, even if it has taken a while to realise.

Sadly the cold start valve wiring discrepancy didn't explain why the car ran so poorly and lean.

Whilst the throttle body was off to access the cold start valve, I once again checked the body and found it occasionally binding a little.
Suspecting the TAV, I decided to disassemble it all again!
This time I stripped it down further than last time, took a brave pill and pulled the piston out!

Image

I cleaned out the piston housing, piston and ball bearing, where the old grease was pretty solid, and regreased with silicon grease.
I also noticed that the cam had a bit of a wear dip at one point which might have been giving a bit resistance. To fix the cam I swapped it for the one from my other unit that had no wear, and put it all back together.

With it all reinstated it was time to try again.

The engine burst into life first time but was now running very rich ( AFR = 10! ). The CIS mixture adjustment screw now needed a large adjustment to put the mixture back into the correct ballpark. I had to replace the plugs again as they had carbon fouled very quickly ( the smoke from the exhaust was very black and rich ).

After new plugs and resetting the idle I now had an idle AFR mixture of 14.7 and a CO figure of 1.5%. 1.5% is the bottom limit of the book spec so just in spec.
Image

Interestingly now the static RPM tests show the AFR to decrease from idle with high RPMs showing sub 13 figures - sounds more promising.

I also experimented with the Innovate Exhaust Probe, and found that restricting the exhaust with a drinks can helped improve the idle values.

Image

Not confident the exhaust probe would survive a drive, we took it for a test drive without the AFR gauge to see how it felt.

Well it felt - totally brilliant! Smooth pickup, zero hesitation at any revs and the hesitation in the 2-3K band totally gone and the valve train is so much quieter.

So in summary, not sure whether it was just the valve train adjustments or whether I have fixed an air leak around the cold start valve, but the engine is very much transformed. I thought it drove pretty well before - but clearly it didn't but it seems to now.

In celebration we took it for a long drive around the Hampshire countryside - a wonderful drive!

Image


Now I could tinker further to see if I can improve on things - but I think for the moment I will leave well alone and enjoy!
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
rhd racer
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Re: The Manhattan Project

Post by rhd racer »

Great result!
93 964 C2
99 Boxster 2.5 > 2.7 hill climber

71 914/6 3.0 - gone

'You see Paul, hill climbing is like making love to a beautiful woman. You get your motor running, check your fluids, hang on tight and WHOA..30 seconds later it's all over!' Swiss Tony
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hot66
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Re: The Manhattan Project

Post by hot66 »

Looks stunning
James

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jb
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Re: The Manhattan Project

Post by jb »

What a lovely ending to what must have been a very frustrating journey.
The car looks great and it sounds like you have it all sorted now.
So glad you have finally found some joy driving it.
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Re: The Manhattan Project

Post by 911hillclimber »

Especially now you can, plan a good road trip and take a camera rather than a tool kit.

Scorching colour for the time of year, lovely looking car and now a cracker.

Don't fix it until it's broke. :)
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Re: The Manhattan Project

Post by AndrewSlater »

Thanks for the comments guys.

Tonight I gave the car a decent 60 mile blast around the New Forest just to check everything is good.

Image

Image

Apart from the front plate becoming slightly dislodged at one point all is pretty good.

The car does have a few pops on throttle off which points to the deceleration valve not quite doing it's job properly, but it all adds to the drama.
I'll try to leave it well alone for the moment as per Graham's advice. :compress:
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
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Re: The Manhattan Project

Post by AndrewSlater »

Well I left it alone for almost 24 hours - sorry Graham.

It occurred to me that the popping on overrun might not be a symptom of running too lean but simply a side effect of the deceleration valve not working correctly. If that was so then I still had room to play to weaken the mixture ever so slightly and prevent the ever so slight carbon pick up around the rear bumper.

It also occurred to me that I had at least one other spare deceleration valve ( or vacuum limiter ) in my stock of parts so thought I would check if that worked OK.
Testing with my hand vacuum pump and gauge that one opened fine at around 15Hg.

So knowing I had a spare it was time to tinker (or f*** it up).

When tested the valve fitted to the car was definately stuck closed - Eureka.
It had worked when I fitted it to the engine all those years ago but had since stuck.

Image

With the replacement one fitted, a quick test run and hurrah, no more pops and bangs on zero throttle ( I say none - we heard a couple in a 30 minute trip whereas previously it was a couple every minute or so ).

Another thing fixed - now I need to test out my theory that I am still running ever so slightly rich and see where that gets me.

I'm starting to get the hang of CIS ( albeit about 3 years too late )
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
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