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Author Topic: Time to do some repairs  (Read 622 times)
Anders Dinsen
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« Reply #15 on: January 04, 2020, 11:12:14 am »

Hi Frederik,

I wouldn't expect you to go wrong with Politecnic. They have experience.

Remember that you'd need to rejet your carburettors, and preferably set it up on a rolling road, so consider that too when you think about cost. A new/better exhaust manifold will probably be needed too.

A number of parameters define the performance of a cam, but it always depends on the engine: Cam development is to my knowledge as much an art as a science. However, the basic parameters are the ability to increase the amount of air being drawn into the cylinder and the ease with which it is blown out.

That depends on lift and period, of course, but there's more: E.g. the exact timing, the envelope (how quickly the valve is opened and closed), the overlap during which both the inlet and exhaust valves are open, and the exhaust and inlet manifolds. All these parameters determine more of the dynamics of the cam, i.e. how the engine performs at midrange to high RPM.

For example, at high air velocity, the vacuum developing on the back side of the exhaust "bubble" as it moves down the exhaust manifold can be used to initiate the draw of air in through the inlet valves early. That's why fast cams have overlap where both valves are open at the same time.

Remember that air has a mass, so getting it moving and accelerating it is important. Also, once the air through the inlet has accelerated, it will generally keep moving through the valve even as it closes, so at mid range to high RPM, the air will continue to fill the cylinder even as the piston starts the compression cycle, so you want the cam to stay open longer on a fast cam.

Now, I can't claim to be an expert. This is just to explain some of the dynamics that experts are working with when they're designing cams.

If you're interested, I suggest you contact Politecnic and inquire them about what kind of performance you will be looking at for the Gr.2 cam and what other changes will be needed. I would expect as a minimum the exhaust manifold should be changed from the standard cast iron manifold to a tubular design and the carbs should be rejetted. The flywheel should probably also be lightened.

/Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Moes
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« Reply #16 on: January 06, 2020, 09:39:35 am »

Hi Anders

Thank you very much for you reply!  Smiley  I really appreciate it. It has helped me to see things in the right light, and to make my decisions on what to do, and how far to go with my repairs  Grin

It would be a lot of fun to get the car on a rolling road after doing all the work you mention, but I would like to have the car back on the road this spring, so I am going to keep it all original, and keep the crank case with cylinder head and cam as it is; I might take off the timing chain, and do some measuring, to see how worn it is.

I was expecting most of the work you mention, if I choose to change the camshaft, but it is good to see a more complete picture of the work that would be needed in writing. I am thinking (dreaming) of having an engine tune-up project alongside a running car. So i might bye an 80´s 1600 cc Talbot engine (Murena crankcase), and rebuild it with a little more kick, to fit my Bagheera; and with a more modern style gearbox. I have found an article about the gearbox Simca used in the 70´s for Bagheeras and other models, and it states that the Simca gearbox were build on a 60´s Porsche design and patent (with compression-synchromesh rings). After reading this article I found a very nice rebuild-guide for a similar Porsche gearbox, which also explains wear and tear on these types of gearboxes: http://porsche.wikidot.com/how-to:porsche-915-transmission-repair-tutorial-part-ii

On Saturday I bought a Bagheera gastank without any damages, and a set of gastank straps. I have been removing a Kg of old underbody coating from tank, and it is looking better and better. I was quite disappointed with the tank straps; they should be original (I can see that one out of four parts is home made), but the original pieces has been welded on to the brackets in the engine compartment (from the factory), and not boltet on as I through when looking at the brackets on my car. Because of this i have chosen only to reuse a few parts for the straps, and make new ones, that kan be boltet on the the existing brackets.

The gastank came from a car that had been stranded for 10-20 year in a field, and it contained app. a liter of.. water! and not a hint of gas. So all metal parts in the tank (suction pipe and level transmitter) had turned into rust residues.

Best regards Frederik      



      
« Last Edit: January 06, 2020, 10:53:01 am by Moes » Logged
Moes
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« Reply #17 on: January 11, 2020, 08:04:35 pm »

I have been talking to a local metal surface treatment company. I heard about the company from a fellow Matra owner some year ago. He had a good experience with having door brackets and other steel parts for he's Murena given a new surface treatment at this place.

I got the idea that it would be much more satisfying to have all the bolts for the gearbox, differential and engine, cleaned and given a new anti corrosion surface, now when I got it all taken apart anyway  Grin

Then I thought maybe they can also do surface treatments of aluminium. They told me that they could do surface treatments of aluminium, but there can not be any steel bushings or any steel parts left on the aluminium parts, because the treatment of aluminium will damage the steel. I was hoping to get the complete gearbox and differential housing treated, but I am not able to get all the small steel bushings out of the lid for the gearbox gear selection mechanism (without damaging them), but I think I can have all the other parts treated. I will drop by company next week with the parts Grin

I have also startet to remove the old paint from the crank case. I startet out with a paint removing gel (Nitro Mors), it does not work that great on a rough surface like cast iron.. but it does make the paint soft like rubber, and then it is rather easy to remove the paint with a wire disc brush. 

 - Frederik
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Moes
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« Reply #18 on: January 13, 2020, 07:29:56 pm »

Today I had an hour to kill, and I got one side of the crank case primed; it feels good to do some work that is going to remain unlike most of the work I have done so far; disassembly, sanding and cleaning.  

Yesterday I started to remove rust ans loose paint on the frame and in the engine compartment. I hav not got very far with it yet, but the dust mask says otherwise  Shocked  I think I will change it out with a full face gas mask the next time.

I have also ordered a set of welsh/core plugs. The first time I started up the engine 10 year ago one of the plugs was rusted, and cooling water was suddenly everywhere, back then I only changed the one plug because it was difficult to get the new plug in place while the engine was in the car.     

- Frederik
« Last Edit: January 13, 2020, 07:46:05 pm by Moes » Logged
Anders Dinsen
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« Reply #19 on: January 13, 2020, 09:41:43 pm »

Greenish-yellow primer - what colour will it become? Awesome to see your progress Smiley
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Moes
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Posts: 147



« Reply #20 on: January 15, 2020, 01:34:21 pm »

Hi

The colour..  It will be a surprise  Grin At first I was going with a conservative colour choice, but them I thought.. No..  be bold!  Grin You will have to be under the car to appreciate it anyway   Cheesy    

Yesterday I delivered all the bolts and nuts + some steel brackets, and the gearbox and differential housings for surface treatment at a place called Værløse Galvaniske (In Denmark), they will do a Plasma electrolytic oxidation surface treatment of my aluminium parts, and some sort og dual layer black electrolytic zink treatment of the steel bolts and brackets, which should be four times as strong than the white electrolytic zink treatment. I am very excited to see the result, I am not completely sure what to expect, they said the result (and colour) on the aluminium would depend on the quality of the aluminium, but I should expect it to be darker in colour; they could also do more funky colors like screaming red or blue, but I told them to do it colorless.    
I have also delivered all of my larger steel parts for sandblasting and black powder coating.

 - Frederik      
« Last Edit: January 15, 2020, 01:36:51 pm by Moes » Logged
Anders Dinsen
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« Reply #21 on: January 17, 2020, 07:58:11 pm »

It all looks absolutely fantastic. I'm always impressed with your work - you're really doing a serious job. Let me guess about the colour... a chromed engine block would be bold, but would require a full stripdown, so probably not what you're doing. I think you'll paint it purple, that will go perfectly with the orange Smiley

Looking forward to seeing your parts. Unfortunately won't have time the coming weekends to drop by Sad

/Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
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