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MD,

That suggestion is too simple. Usually complex problems like a malfunctioning hydraulic belt tensioner deserves a similarly complex explanation and solution, like "mate, your block was casted wrong causing your tensioner to malfunction, we need to do a new cast and full rebuild".

We can't have things like "Hey buddy, did you tighten the bolts properly?". It takes away from the excitement. Hope you understand.

MD wrote: ↑Mon Jul 20, 2020 2:02 am Is it possible that you may have a loose front pulley?

Checked the nut. But it was tight.

@MD: your far of. It's an interstellar problem
No offence mate

With the new brace it looks a lot better then before. Now it is only a few degrees. Orderd a new sensor because it once rubbed the toothed wheel and it got a little thin up front. Maybe there's some flex also.

But it looks like a computer problem. It hits for example +2 degrees. Stays on that spot for a few seconds and jumps to minus 2 degrees.... maybe the flex in the sensor messes up the predictiuon algorithem in the ecu..?

Have you thought about a new efi system? Like MAXXECU? I like the UI. Originally I thought "who needs a good UI as long as it can run the engine"...I was wrong.

Yes, thought of it. But let's first see if it is something more cost friendly.

You can check used Autronic SM4 units, less than 800 euro . In some cases with CDI as well. If a used one comes up I will let you know.

Software issues aside, you may have another simple problem such as intermittent make & break episodes in a slightly defective loom. Even the connector from the sensor to the loom can get very contaminated and cause resistance based voltage drops. Remembering that the output of the sensor would be in millivolts which is a weasel amount of power to mess with. ( Much like evos' right hand after 99 strokes )

If an affordable quality ecu is a consideration, I have a friend who has an Autronic Sm2 for sale. It will do more than everything you need and has auto tune, traction control etc... If you’d like more info, send me a pm and I’ll put you in touch with him.

Only issue with autronic is you need to run a home/cam sensor. I didn't check if this build had it. A few ways to do that for the 12V. You can use the distributor mount a bolt on the rear of the cam gear and the sensor on the head behind the cam gear.

75Evo, true it would be best to use a cam position sensor to utilize full sequential injection. As there is already a crank sensor on the crank as you mentioned he could use the Distributor or a bolt on the cam pulley but I would be inclined to to use the location on the back of the left cyl head where the 164 dist originally was located. Use the 164 dist housing and parts of the internals. To mount a sensor no need to use the dist cap.

If this build used a 164 head it should work. I could be wrong, but if it has an early 75 3.0 V6 heads then some minor machining may be needed.

Had a nice vacation in France for a coulple of weeks.

Thanks for the thinking guys.

A new ecu would be very nice. It also is a lot of work. I have to learn myself all the new software. Rewire the engine becuase it is set for batch injector fire. Install a camshaft angle sensor.

I orderd a new timing light beauce i noticed rpm reading on the light was faulty. It was fluctuating a lot. Let's see what it does.

timing light was broken. It was a brand new one.
Bought an other one without rpm calculation and without a timnig you can set on the timing light because i heard a lot of bad stories from them when i searched the web.

Finaly we can drive again!

How much power do you think a 2.5 12v with cams and a Rotrex running 1 bar of boost can put out? 300 bhp possible? Thinking of building a 2.5 12v since they are pretty cheap and already have low comp 9.5:1 pistons.

Probely not. 9.5 is still to high. I went in a knock limited power band with my 9.5 cr and couldn't push it further than 310hp. That's why I now run lower cr. Also 1 bar is probably a bit low but I don't know how efficient the sprintex blowers are?

I was wrong. The 2.5 in the 75 has 9:1 CR. Rotrex is like a turbo, so no crazy torque at low rpms. The sprintex is a positive disp. twin scroll unit so lots of torque and heat.