Putting a 3.2 into a 71t

dmcummins · 12-05-2008, 01:02 PM

I have read some of the previous swaps, but I still have a few questions as I want to start looking for the parts I need.

I bought a 71 roller several years ago and I am just now getting around to working on it. I also picked up an 84 euro motor last year. Since I have had a few longhoods, I have some spare parts laying around and I'd like to use them if I could.

I understand that I need a return fuel line running to the tank. I'm pretty sure my 71 does not have a return fuel line. I assume this means that I need a newer tank and I'll need to run another fuel line to it. Has anyone used an older tank and run a return to it somehow or do I just need a newer tank. I also will need a 3.2 fuel pump and fuel filter.

My understanding is that I will also need a 915 trans for the 3.2 as the 901 is not up to the task. I will also need a new shifter and rod that runs to the trans. Also does the year of 915 make a big difference. I know the earlier ones were geared differently, is one preferred for this setup?

For the engine can I use an older pair of exhaust and muffler? I plan on backdating the heat and I have some good heat exchangers and muffler from a 69. Also I currently do not have an external oil cooler, is this required for a street car?

I plan on stripping the paint off the car and replacing most of the suspension ect. so it will be awhile before I get to the engine and trans swap, but I want to start watching for the parts I need if I can pick them up for a good price. And with the economy the way it is I'm in no hurry.

Am I forgetting anything? I know will be alot of little things that I need but Im just trying to get the big things first.

Rot 911 · 12-05-2008, 01:08 PM

Older exhaust and muffler bolt right up. I am running SSI's on my 3.2. If you need any pictures of my '86 Carrera to help your install, just let me know.

4flyboy · 4flyboy's Garage

It's mt understanding that the ROW (European) cars came equipped with oil coolers for their 915 transmissions. More experienced guys than I will weigh in on it's necessity I'm sure.

Please post pictures when you get underway!

Good luck,

Scott

hillsprint · 12-05-2008, 01:35 PM

I bought a 71 T chassis with a 3.2 and oil cooler 915 box installed and I have just taken it out to put the car back to 2.2 spec !! Here is what I know :-

You need a different clutch cable.

The 915 box, you want a later one, which has the additional ring of webs on the diff side casing, the 3.2 is a torquey motor and if you start putting your foot down it's going to put a strain on the box. This box will have an electric speedo on it, so you either need an new speedo to suit or convert the box to take the mechanical speedo from your car.

The Motronic ECU, and other goodies usually sit under the passenger seat, or certainly inside the passenger compartment. You need to see where you want to put it and whether it fits under the seat.

Cheers

Michael

jpnovak · 12-05-2008, 01:42 PM

You will need to match the stub axles with the MY transmission. The early 915s (and 901s) had 108mm, 4 bolt, 2 pin CVs and output flanges. Later 915s (starting in 75?) had smaller 100mm- 6 bolt output flanges. The actual shafts are smaller to and not compatible with just swapping a CV joint on one end.

73/74 915s (and some 75s) had the 7:31 R&P. Later had an 8:31. Try to find one with the shorter gears. Also, the 73/74 will be setup for the mechanical speedo allowing you to keep your current gauges. I did not include the 72 915. It is less desireable due to case strength and ease of replacing seals. Also the TOB guide is not removable.

You will need to notch the top of the 915 for the Motronic reference sensors for all years.

An upgrade to later trailing arms will solve this problem although the 915 style stub axles will fit in the early steel arms.

The wiring changes should be relatively simple. You will need the updated fuel pump, not just the lines. Your T should have a return line in the tank and tub. The carb'd T used a rotary fuel pump that had an integral return line. It mimicked the MFI pump with much less pressure.

ossiblue · 12-05-2008, 06:59 PM

Your tank has a return line, but it doesn't have the internal "swirl pot" that came with MFI and CIS cars which, I believe, was designed to eliminate turbulance/bubbles from the high pressure return fuel from hindering the fuel pick up. Someone may have experience with a pre 72 tank with later pumps, so I don't know the true effect. Since your changes are moving far from stock, you may want to get a later and larger volume tank (74 >)to deal with this situation.

dmcummins · 12-06-2008, 09:49 AM

Thanks guys. I jacked up the car so I could get a better look at what I have. The tank does have a return from the fuel pump. I understand that the older tank may not be ideal but I'm really just trying to use what I can for now and figure I can always change some of it out later. As long as it doesn't cost me more to do it that way. It looks to me that I need to run a line through the tunnel from the engine compartment to the fuel tank. There is currently a plug next to my fuel line that I suppose was where a MFI car ran the return.

dmcummins · 12-06-2008, 09:51 AM

Here is a couple of pics of what I found.

dmcummins · 12-06-2008, 09:53 AM

I have a set of rear aluminum control arms that I plan on using. So I need to match the axels, and stub axels to the year of transmission, correct.

RWebb · RWebb's Garage

correct. There was a recent post with some info on this...

good luck with the fuel line & electrical changes.

BK911 · BK911's Garage

Quote:

Originally Posted by ossiblue

Your tank has a return line, but it doesn't have the internal "swirl pot" that came with MFI and CIS cars which, I believe, was designed to eliminate turbulance/bubbles from the high pressure return fuel from hindering the fuel pick up. Someone may have experience with a pre 72 tank with later pumps, so I don't know the true effect. Since your changes are moving far from stock, you may want to get a later and larger volume tank (74 >)to deal with this situation.

I put a 3.0 into a 73. The fuel pump would cavitate under braking with anything less than 3/4 tank, sometimes even stalling. I put in a fuel tank from a '74 with the 'swirl pot' and the cavitation issue went away.

dmcummins · 12-06-2008, 08:07 PM

I'm starting to think it would be easier to put the 3.2 into my 73. I'm having some problems getting the CIS to start when its cold and its not the original engine anyway. Also I could have this car going sooner with less money as I could use the existing transmision and Ive already gone through the suspension and everything else on the car.

ossiblue · 12-07-2008, 10:08 AM

That might be a plan, and the tank issue might be solved--I say might because I thought MFI cars had the '"swirl pot" as well as CIS but from BK911's post, I'm not so sure. Your car looks to be a MFI 73, correct?

dmcummins · 12-07-2008, 10:47 AM

I think it was originally a CIS car, but I can't be sure. Its definatly not the original motor. Its a 72 with a 73 CIS injection added.

When I had the motor out you can see the MFI wheel on the back. I'm not sure how all this went together, but except for it being hard to start when cold, it ran fine.

But I have this 3.2 motor that is going to go into something. I just have to decied which way I want to go. I have some things to work on on both cars to keep me busy for the time being .

dmcummins · 12-07-2008, 10:50 AM

Is an external oil cooler required for the 3.2. Neither of my early cars have an external cooler. I know it would be nice to have, but this will be a street car and something that I could posible add later if needed.

dmcummins · 12-07-2008, 12:27 PM

Im guessing on some cost, but how do these look.

915 trans $900 - $1,500
74 up tank $200-$300
84 up fuel pump $150-$250
fuel lines, misc,ect $1000

So that comes out to be around $2,250 to $3050 to just put the motor into the 71. Add around $1000 to $1,500 if an external oil cooler is needed.

Does that seem about right? The cost to put it into the 73 would be less the transmission.

dmcummins · 12-07-2008, 12:33 PM

The 71 does need a few other things though.

cubby911T · cubby911T's Garage

Quote:

Originally Posted by dmcummins

Is an external oil cooler required for the 3.2. Neither of my early cars have an external cooler. I know it would be nice to have, but this will be a street car and something that I could posible add later if needed.

I converted my '77 911 to a 3.2 last summer without installing the external oil cooler (yet). In cool or cold weather my engine temp stays under 200 deg, but once the ambient temps get into the 70's and 80's the engine temp rises to 215-ish within a half hour or sooner if I drive spiritedly. I have not pushed it beyond that point and don't plan to.

I do plan to install a cooler and you probably should to, but it doesn't seem to be an urgent task unless you plan to do autocrossing or drive for long periods in warm ambient temps. Hope this helps.

ossiblue · 12-07-2008, 05:02 PM

It still may be better to put the engine into the 73 because of the trans. I guessed your car was originally MFI because of the bumper guards, though those could have been changed. What is the build date or vin? Is it a 73.5? If so, it should have the correct tank but with the 3.2, you may wish to get a later tank simply for the larger volume and subsequent driving range.

My understanding is an external cooler is almost a "given" on 3.0 and higher displacement engines and well worth it to avoid excessive temps, especially in summer. The money saved on the tranny might be put into the oil cooler.

dmcummins · 12-07-2008, 07:17 PM

The previous owner painted the silver car black, I then stripped the paint off and painted it back silver. I'm not sure if it was an original CIS car, but I assume it was and someone just swapped out the longblock at some point. I changed the bumper guards as I liked the chrome ones. [img]

This is what the car looked like when I brought it home.

http://forums.pelicanparts.com/uploads14/DSCN04721228706170.jpg[/img]