I need help on a 740

Howling · Post by **Howling** » 26 Dec 2009, 21:15

I need some input on a 1990 740 turbo. Does anyone know where i can find a serpentine belt kit to replace the v-belts I have now? And is there a major difference in the turbos from a 740 and a 780? Any help would be grateful. Thank you

Howling · Post by **Howling** » 26 Dec 2009, 23:17

One other thing, my tachometer just stops working from time to time. Any thing I can do about it?

Post by **jblackburn** » 27 Dec 2009, 02:46

Not sure if there's a kit or not, I thought IPD had one for the 700/900 series cars, but I can't seem to find it.

Here's all the belts though:
http://www.fcpgroton.com/category-exec/ ... by_year/40

I don't know anything about the 780 model Volvo, but if you can get your hands on one, they're EXTREMELY rare. A '90 740 had a better turbo than the previous models, and I'm not sure if that carried over to the last year of the 780.

As far as the tach issue, start by checking the wiring to the RPM sensor at the back of the engine by the flywheel. It may just be a loose wire.

Howling · Post by **Howling** » 27 Dec 2009, 09:15

ok thank you for the help and a starting point. This is my first Volvo and so far I love it. Thanks again for the help.

Post by **billofdurham** » 27 Dec 2009, 11:28

The 1990 740 turbo had a TurboG3 tic. This was the Volvo designation. The turbo was a Generation 3 and was either a Garrett T25 or a Mitsubishi TD04. Both were intercooled. Generation 3 turbos were smaller, giving faster spoolup and less 'turbo lag'.

The 1990 780 turbo coupe had a TurboG3 tic+. Again, the Volvo designation. The Generation 3+ was either a Garrett T25 or a Mitsubishi TD04. Both were intercooled and had higher boost than the Generation 3.

I have never heard of a kit to convert to a serpentine belt. I would think that converting to one would be a major, and very costly, enterprise as you would have to change every pulley, add a tensioner and probably have to move some of the driven parts to accomodate the belt.

Bill.

Howling · Post by **Howling** » 27 Dec 2009, 14:45

I have a lot of time to design a pulley system for it and i work with a lot of machining tools at work. If I can get the specks on the output shafts I can come up with something to build for it. As far as the turbo goes would the Mitsubishi turbo work and bolt straight on? Would i have to worry about any codes with it?

Post by **billofdurham** » 27 Dec 2009, 16:06

If you were to make your own pulleys you would only need a tensioner and a belt. The length of the belt would have to be determined after you had the system ready to take it.

The turbos are basically the same. Generation 3+ has higher boost than Generation 3. I can't see that you would set codes by changing.

Bill.

Howling · Post by **Howling** » 28 Dec 2009, 09:09

OK Bill. Thank you for all the info. Let me ask this then, what is the psi for the stock 740 turbo and how can I increase it? I am new to the whole turbo and volvo world. They seem to be a lot like superchargers on a v8 chevy but with their differences too.

Post by **jblackburn** » 28 Dec 2009, 09:11

My mistake, I thought you were asking about a kit that contained all the belts to replace rather than to convert to a serpentine. No, there isn't one of those!

I can't see that there would really be that much of an advantage to convert to a serp. belt. They are slightly more fuel-efficient and more organized with one belt driving everything, but I'd say the work involved in such a feat far outweighs the slim advantages you'd get from doing such a conversion. I'd almost rather have multiple belts in mine like my old Saab did - that way, if one breaks, you don't lose EVERYTHING driven by it. Replacing serpentine belts and stretching and routing it around everything are just a PAIN, and a near-impossible task in a cramped Honda engine.

Post by **billofdurham** » 28 Dec 2009, 12:05

I can't see that there would really be that much of an advantage to convert to a serp. belt.

+1 on that.

My book shows the T25 can hold 10psi comfortably and can reach 15psi, but for only a very short time. However, I have also found that the Garret was fitted to manual 740s only. The auto had the Mitsubishi.

For more info on increasing boost use this link.

Bill.