964 Turbo: Bushings and Coilovers

It has been a while since we updated everyone on the beautiful 964 Turbo barn find that Rennline owner Paul was able to recover in North Carolina. The 964 Turbo is continuing to rise both in desirability and value; the last of the Turbos to feature truly classic 911 styling, but were limited by Porsche’s budget at the time which. The result? For a long time the 964 was relegated to the “not so desirable Porsche” category. Fiendishly complex and technically advanced, the original 1989 964 C4 was Suttgart’s way of showcasing the technology developed with the legendary 959. C2 models followed for 1990, and a myriad of variants became available in the following years, however this would be the last of the legendary Turbo line not to be all wheel driven.

Classic 911 with 964 Turbo in Rennline shop

This particular 964 was parked years ago due to a leaky brake caliper of all things. The then-owner decided that lack of use and cost of repairs was enough to justify some downtime. ‘Some downtime’ turned into years, which turned into full fledged abandonment, and that is about where our story picked up last installment. This meant that there was plenty of work to be done. As many will tell you, a car sitting deteriorates much faster than one being driven, so there have been a number of time related issues that needed addressing. First up was the front suspension, which not only featured a plethora of dry rotted rubber bushings, but also steel bolts that were corroded and frozen into the aluminum subframe. The result was that we had to remove the driver’s side front subframe just to remove what remained of the bolt!

964 turbo receiving a minor restoration

With all of the front suspension bits finally freed up, we went about burning out the rubber bushings, cutting out the residual races where necessary, and pressing in a fresh assortment of Rennline HD bushings. Our High Density (HD) line of bushings feature rubber construction to avoid annoying squeaks and groans typical of aftermarket poly and delrin bushings, but feature stiffer durometer even compared to OE RS or similar parts. This means you get the performance increase of a stiffer, more responsive chassis without dealing with the extra NVH, squeaks and creaks associated with most aftermarket solutions. The installation of the front suspension bits went smoothly as expected, simply pressing into the control arms just like factory bushings. Thankfully it was less stinky than the process of removing the old bushings!

Pressing new bushings into 964 control arms

We are not known for leaving things “well enough,” so while the car was in the air and the front suspension was totally disassembled a set of Bilstein PSS10 coilovers found their way into the mix. PSS9/10s are widely known for their high-quality, rebuild-able design, adjustability and performance during track and spirited driving. Based on our past experience, we deemed these the best fit for the kind of roads and driving this Turbo will see. We paired these coilovers with a set of our Rennline Adjustable Camber Plates in the front and Monoball Strut Mounts in the rear. This will ensure that we are able to maximize the benefits of increased stiffness added by our High Density suspension bushings. Further, this will allow us to dial in appropriate camber settings when we get around to taking this thing to the track, and will ensure minimal suspension geometry changes during hard driving.

Rennline camber plates with Bilstein PSS10 coilovers

With the front end back together and the car on the ground it was time to get it moving under its own power for the first times since it came to the Rennline shop. When it first arrived, the first items on the docket were to drain the 5-10 year old gas, change the fuel filter, pump, plugs and wires. With this basic tuneup and a little futzing we got it fired up and settled into a nice, even idle with no smoke or strange smells coming from the exhaust. With the car on the ground we finally had a chance to give it a serious test!

Rennline camber plates and Bilstein coilovers in our 964 turbo

Unfortunately, the brakes that originally caused the car to be parked have since deteriorated further. This meant that a single front caliper leak has developed into a front and opposing rear rendering the car able to brake but not able to do so quickly or exceedingly effectively. Despite this limiting factor the 964 made its first laps around the industrial park under its own power! The engine, it turns out, is indeed nice and strong, giving solid off boost response and a mid range without hiccups or misfires. The turbo spools up nicely and makes target boost levels in typical early-turbo style: plenty of it but after a deep breath to spool.

964 turbo first drive

All in all we are extremely pleased with this project’s progression. It is a back-burner barn find that has provided a relaxed and enjoyable series of projects. Without a deadline and with all the other things going on in the shop we are taking our time with this one and having fun! That said, we are looking towards the 2016 season for the debut of this thing at some or our local New England track events!

964 turbo cooling down after first drive

Leave a Reply