914-4 to 914-6 suspension conversion

[Maj75]

I’ve searched and found a ton of information on the engine part of this conversion, but almost nothing about the suspension side. I’m acquiring parts for this conversion and don’t want to waste money buying the wrong thing. I know generally the 914-6 uses 911 front suspension. My question is what year 911 suspension works? I assume that I need struts, control arms, torsion bars, sway bar?

Do I need any changes at the rear? I planned to get the re-drilled rotors for the 5 lug wheels and add a sway bar.


I’m not familiar with air-cooled 911 parts interchange, so all help appreciated.

[Emo993]

Maj75. fronts you can do with just 911 struts and brakes (keep all the rest). They can be purchased with raised spindles, car can be lowered without bump steer issues. And rears you will want early 914 hubs with the five boss's for drilling for studs, then 5 hole rotors. Best, Mark

[Emo993]

bdstone914 just sold a pair of early rear hubs over on 914world. Contact him, see if he can find another set.

[racer]

911 front suspension from 1969-1989 will bolt right on. A 914/6 will have one from a 69/70 911T. The primary differences come with brake calipers. "early" 911's have a 3" spacing on the strut for the caliper. "later" 911's have a 3.5" spacing. Certainly this happened by the 911SC (so 78+) but can't recall if it started earlier (midyear 74-77?). This would impact which calipers you would use.

The rear, suspension wise is the same, but the 6 used heavier springs. Yes, the rear brakes/calipers are also different as they are for 5bolt wheels, but thats technically, not part of the suspension. The "6" engine/oil tank etc weighed a bit more than the stock 4. I think the whole car was about 200#s more.

[Maj75]

Originally Posted by racer

911 front suspension from 1969-1989 will bolt right on. A 914/6 will have one from a 69/70 911T. The primary differences come with brake calipers. "early" 911's have a 3" spacing on the strut for the caliper. "later" 911's have a 3.5" spacing. Certainly this happened by the 911SC (so 78+) but can't recall if it started earlier (midyear 74-77?). This would impact which calipers you would use.

The rear, suspension wise is the same, but the 6 used heavier springs. Yes, the rear brakes/calipers are also different as they are for 5bolt wheels, but thats technically, not part of the suspension. The "6" engine/oil tank etc weighed a bit more than the stock 4. I think the whole car was about 200#s more.

That’s the info I need. I didn’t know whether I needed the ‘69-70 control arms or any 911 up to ‘89. That makes the search easier and finding later brake calipers should be much easier.

[DonNewton]

I used 930 front uprights from a turbo that got REAL tail-happy. Then, I put Boxster calipers. Have the bias dialed back a bit and it will stop on dime and give you a nickel back. Then again, this was street/race/and back to street car. This is just to show that just about any combination will work.

[Dave at Pelican Parts]

The absolute minimum you need from the 911 front suspension are the strut assemblies with hubs and brakes and such. You can use the 914 A-arms, torsion bars, sway bar (if any), and so on.

You can switch the entire front suspension over to the 911 parts if you desire. Remember that the A-arms and the ride height adjusters need to be from the same type of car as the torsion bars, because 914 and 911 have different numbers of splines on the ends of the torsion bars.

The original Six rear was basically identical to the four-cylinder suspension, except that the rear hubs were drilled for the five-lug pattern instead of four-lug. The brakes were also slightly different, in that the calipers had different-diameter pistons inside them. You can have your hubs drilled and have studs pressed in, as long as the machine shop is careful to maintain the strength and concentricity of the the holes. Generally press-in studs will be stronger here than simply drilling and tapping for lug bolts as the original Six used. It may be possible to weld up the old holes and re-drill in the new pattern, but the hub might need more machining at that point if the heat of welding distorts it.

Here is an older article about the options. The information is mostly good, but there are several more options now than when it was written.

I believe that PMB Performance sells a rear conversion kit that is complete. They also know more than probably any of us about 911 and 914 brakes, so it is probably worth at least talking to them.

--DD

[colingreene]

I guess it depends on your goals here.

From the factory others have covered the front suspension well
the rear was a slightly higher spring rate, thats about it.

What are you doing with your car, what motor are you putting into it, what wheels and tires and what will you use it for?

[Maj75]

Originally Posted by Dave at Pelican Parts

The absolute minimum you need from the 911 front suspension are the strut assemblies with hubs and brakes and such. You can use the 914 A-arms, torsion bars, sway bar (if any), and so on.

You can switch the entire front suspension over to the 911 parts if you desire. Remember that the A-arms and the ride height adjusters need to be from the same type of car as the torsion bars, because 914 and 911 have different numbers of splines on the ends of the torsion bars.

The original Six rear was basically identical to the four-cylinder suspension, except that the rear hubs were drilled for the five-lug pattern instead of four-lug. The brakes were also slightly different, in that the calipers had different-diameter pistons inside them. You can have your hubs drilled and have studs pressed in, as long as the machine shop is careful to maintain the strength and concentricity of the the holes. Generally press-in studs will be stronger here than simply drilling and tapping for lug bolts as the original Six used. It may be possible to weld up the old holes and re-drill in the new pattern, but the hub might need more machining at that point if the heat of welding distorts it.

Here is an older article about the options. The information is mostly good, but there are several more options now than when it was written.

I believe that PMB Performance sells a rear conversion kit that is complete. They also know more than probably any of us about 911 and 914 brakes, so it is probably worth at least talking to them.

--DD

Will any 911 strut work with the 914 A arms, or is there a particular year 911 I need to look for?

[Maj75]

Originally Posted by colingreene

I guess it depends on your goals here.

From the factory others have covered the front suspension well
the rear was a slightly higher spring rate, thats about it.

What are you doing with your car, what motor are you putting into it, what wheels and tires and what will you use it for?

First is get it running and driving. I want to find out if I can get the transmission shifting well enough for track use. If I can, I want to convert the suspension to 914-6 spec and swap a Porsche flat six. A carbed 2.7-3.2 is what I’m hoping to use. I want to run Fuchs in a -6 configuration. Not interested in the GT big flares.

[911pcars]

Early 911 factory brakes comes in three flavors:
a. M calipers, cast iron, 3" bolt hole centers, solid (non-vented) rotors, 20mm
b. A calipers, cast iron, 3.5" bolt hole centers, vented rotors, 20mm
c. S, aluminum, same spacing as in b., vented rotors, 20mm

84-on front rotors are 24mm wide with widened A calipers.

more here and in the archives:
https://www.pelicanparts.com/techarticles/101_Projects_Porsche_911/47-Brake_Disc_Repl/47-Brake_Disc_Repl.htm

Sherwood

[Dave at Pelican Parts]

Originally Posted by Maj75

Will any 911 strut work with the 914 A arms, or is there a particular year 911 I need to look for?

Any 911 with torsion-bar suspension, so basically anything before 1989 (and some 89s).

Generally the 72+ ones are preferred because of the better ball joint and ball joint retaining mechanism, but any will fit the 914 A-arm.

Originally Posted by 911pcars

Early 911 factory brakes comes in three flavors:
a. M calipers, cast iron, 3" bolt hole centers, solid (non-vented) rotors, 20mm

There were also front M calipers made for vented rotors. There were spacers used to fit them, but I think (not sure!!) that there were also M calipers made for vented rotors that didn't use spacers in between the caliper halves.

--DD