redline

[zuerchers]

i am new to the world of porsches and need to know...how bad is it to redline the 3.2 engine? are these engine so well balanced that they can maintain that high rpms without doing much damage or excessive wear and tear? FYI, my engine is completely stock.
thanks

[Chuck Moreland]

It's absolutely fine and required if you are going to drive the car as it was meant to. Your car will do this all day long.

About 300 rpm above the indicated red line a rev limiter will kick in preventing you from going any higher. You are safe up to the rev limiter.

Some aftermarket chips raise the rev limiter, that is not good. If you have one of those chips it is not a good idea to go to the rev limiter.

[Doug E]

1 year ago I was in your shoes - new owner not quite sure how to drive a 911. This board and lots of miles made me realize how these cars are meant to be driven.

Enjoy your car like it was meant to be driven ... safely and to the limit!

[zuerchers]

thanks for the responses...thats what i wanted to hear. now, i have one broken head stud. how does that change things?
thanks, mike

[steve rush]

Just a note on how tough these motors are...a few years ago a good friend with a rail dragster with an SC motor had a missed shift at Mission in BC (Canada) and had another friend / shop in Edmonds (Washington) rebuild the motor after the tattletale showed 11000+....could not find ANYTHING wounded...resealed and went racing. "There is no substitute"

[pbs911]

I rtan mine at redline for three 20 minute sessions at the California Speedway today. It never ran better!

As for the broken headstud, it goes without saying that it should be fixed before even running the motor. You can do some significant damage even if you don't run it at redline from the head slapping on the cylinder. That said, I believe Superman ran his for quite a while with 2 or 3 broken head studs. He eventually rebuilt the motor, but did not document any damage from running the car with the broken head studs.

[StuttgartDavid]

I disagree that running with the broken headstud will automatically damage it. Many owners tear down their engines to find that they have been driving for a long time with one or more broken studs with no resulting damage. For serious high temp, sustained hi rpm/redline track use you may have issues, but I believe that for street use with regular redlining through the gears should cause few problem in the short to medium term.

[zuerchers]

StuttgartDavid...you're my new best friend! thats what i wanted to hear.

pbs911, thanks for the advice. i want to fix it but i would like to wait intil its time for a rebuild. i only have 150K on the engine and had a top end rebuild done 15K ago. i am due for a valve adjustment in 5K and will re-evaluate then. it must have been really fun to redline like that for so long. one of these days!

[Wayne 962]

Wow, there's a bit of mis-information here.

Firstly, running with a broken head stud will not automatically damage the engine, however, it increases the likelihood of it. Worst case you'll destroy one head and one piston (happened to one of my cars).

Secondly, the 3.2L engines suffer from a HUGE rod bolt problem that is directly related to redline over-revs.

Here is a section from my new book:

Rod Bolts – Carrera (1984-89) & 911 Turbo (1978-89)

In 1984, with the release of the 3.2L engine, Porsche reduced the size of the rod bolts used inside the engine to 9mm from the 10mm used on previous engines. Using the rods from the 1978-89 911 Turbo 3.3L engine in conjunction with the Turbo crankshaft increased the displacement to 3.2L. Unfortunately, it has been recently discovered that the rod bolt diameter is too small for the large loads that these engines place on the rods. A number of failures in the 911 Carrera motor have been traced back to the rod bolts failing to adequately maintain their proper tightness.

The failure occurs when the engine is consistently revved at the high end of its RPM range. The stock rod bolts are designed to stretch when tightened down to their final torque values. At RPMs of 6700 or higher, the rotating mass on the end of each rod (namely the piston and the mass of the rod itself) has a tendency to stretch the rod bolt further. Repeated stretching of the rod bolts causes them to deform and loosen up which can result in rod separation and complete engine failure.

While all engines for all years need to have their rod bolts replace during a rebuild, the remedy for these particular engines is to install aftermarket performance rod bolts in the rods. Quality hardware from Race-Ware or ARP are two very good substitutes for the original rod bolts. In the meantime, if you have a stock 3.2L engine, one remedy is to make sure that you do not rev the engine over a safe range like 6300 rpm. This risk of failure applies to both the 911 Turbo engines, and the 3.2L Carrera engines.

------------------------------------------------------
This is a very well documented failure that affects 3.2, 3.3 and 3.6 liter engines, and should not be 'glossed over.' I have pictures in the book of a completely destroyed 3.6L engine (rod went through the case) that was caused by this failure.

The 3.0L engines can be revved higher than the 3.2L because they don't suffer from this problem.

-Wayne

[Wayne 962]

Also suspect is your 15K top-end rebuild. Any good Porsche mechanic knows to replace the head studs while they're in there with the steel ones. The fact that you have a broken one tells me that they weren't replaced. Makes you wonder what other short-cuts were taken?

-Wayne

[Randy W]

I agree with Chuck and Wayne. The biggest danger of aftermarket chips used in a stock rod bolt 3.2 is too high an RPM limit. A few years ago I put a stock 3.2 in my '72T and replaced the chip with an aftermarket one that raised the RPM cut out to 7000. I also delayed putting in an auxillary cooler due to cost and weight. Result? After six months of autocrossing and DE: burnt rod bearings, copper in the oil, and a knocking noise that signaled eminent engine failure. The engine was rebuilt with ARP rod bolts and a Carrera cooler with fan was added. One rod, half the valves, all the rockers, guides and the engine oil cooler had to be replaced. And I consider myself lucky that the crankshaft could be reused!

Moral of the story: On a stock rod bolt 3.2L, get a Carrera cooler and make sure you keep the revs under 6700. When it's time for a rebuild, replace the rod bolts with ARP or Raceware.

[zuerchers]

i just checked the invoice from the top end job and they did not replace the head studs.

thanks again for the info.

wayne, i ordered your book, 101 projects, and it wasn't autographed...very disapointed. great book though and looking forward to getting the next.

mike

[Wayne 962]

You got it from Pelican? Wasn't autographed on the front cover? Perhaps I missed that one - I sign them all...

-Wayne

[juanbenae]

mine was signed by the big kahuna and now i dont even like to use it. i photo copy the pages i need for the current project, staple them together then head for the garage. dont want to get it oily or greasy.....

[jyl]

So revving a stock 3.2 to 6,200 rpm is fine (absent some specific problems with one's engine), but going up to the high-six-thousand rpm range or higher can be problematic due to the stock rod bolts?

Just trying to distill the various comments I'm reading on this thread.

[Wayne 962]

jyl, there is no exact science. I'm sure that there are people out there who say they never drove their car past 6000 rpm who have the problem. And then there are others who might say that they have raced their 911 for 15 years past the redline without a problem.

All I can say is that there is a definite problem that is exacerbated by the high-RPM range. This problem should be fixed in all 3.2/3.3/3.6 rebuilds...

-Wayne