964 Engine - What is the realistic redline for bottom end?

[TonyG]

With respect to a 964 3.6 liter engine....

What are the stock rods/stock rod bolts, good for with respect to rpms (using stock pistons)?

Sustained rpms vs short bursts?

Need real deal figures....



Thanks,


TonyG

[ischmitz]

I wouldn't go anywhere over the stock rev limit unless you have upgraded the rod bolts to ARP or Raceware. They are known to be the weak link in these engines. Every burst over redline adds up to an eventual failure.

[Wayne 962]

I agree with Ingo. 6500 to be extra safe...

-Wayne

[TonyG]

The stock rev limit (according to the tach) is 6800rpms.

Are the rods/rod bolts good for 6800rpms sustained? (meaning running to redline through the gear shifts time and time again, on a track)?


TonyG

[ischmitz]

Well, let's put it this way: Even though I am relatively cheap I did replace my rodbolts with ARP when doing the topend. And I do not run constantly at the (stock) rev limit.

Someone told me that the damage is accumulative. In other words if you constantly scratch that redline area chances are that over time you will see a catastrophic failure. By the way in stock configuration your powerband is before redline. So if you change things redo the rod bolts at the same time. It can be done without splitting the case. The cylinders have to come off.

Cheers,
Ingo

[herman maire]

Guys.... With just the bolt upgrade is the rod still a really big weak point?
In Anderson's book he mentions the crappy rod bolts but when upgraded the rods should be fine.

I wanna be able to rev my motor to 6800-6900k RPM and not have to worry .

Are the rods really that bad?

[Jeff Alton]

The rod is not the weak point for the revs you want to run, the bolts are.

The rods are fine, they are used in 3.3 turbos, 3.2 and 964 3.6 (and maybe the 94 3.6 turbo, though I am not 100% on that one) The problem is the bolt 9mm compared to the SC bolt which was 10mm.

Cheers

[TonyG]

Great info.

But the $64,000 question is.... who races their stock rod/stock rod bolt 964 engine w/o problems?

And... who has lost a rod on a stock rod/stock rod bolt 964 engine which was kept at or under the factory 6800 rpm redline?


TonyG

[herman maire]

Originally posted by catca
The rod is not the weak point for the revs you want to run, the bolts are.

The rods are fine, they are used in 3.3 turbos, 3.2 and 964 3.6 (and maybe the 94 3.6 turbo, though I am not 100% on that one) The problem is the bolt 9mm compared to the SC bolt which was 10mm.

Cheers

I am under the impression that 993 rods are not as strong as the 964 rods.
I am still trying to get my 95 993 3.6 build together..... I am going to buy the rod bolts for sure (probably raceware ) but I really dont feel like spending $1800+ on carrillo rods just to be able to run my motor to 6900-7000 rpm with a nice cam
which is still 3-400 rpm less than my 'S'

My 73 "S" still screems to 7200-7300rpm and still runs perfect after 33 years

[Cookie Porsche]

But the $64,000 question is.... who races their stock rod/stock rod bolt 964 engine w/o problems?

Tony, I have raced a very modified 964 engine (3.8 - 350bhp) for over two years now. The rods and bolts are stock standard - the rest of the engine is not! I use factory RSR cams and rev to 7000 (soft cut out). Max is 7200.

I have had half a dozen whoopsies - say 7500-7800.

Estimating +/- 5000 kms on the current engine (more than 30 race starts) so far and that at least 50% of the distance has been @ 100% throttle I can safely say that the 964 can handle quite a lot.

To run it safe I use 6800 in practice and when in front (brag brag). Max power is around 6600 rpm.

I did hit the valves twice (you know - twice burnt...) before pocketing my pistons a little - other than that she's as strong as ever.

Of course all parts must be sound and known - don't fit unknown bolts.

Tom

[JP911]

I think Jack Olsen runs a stock 964 engine in his car, which he tracks often. Maybe he will pipe in here.

[snowman]

The use of factory parts is best if you track you car on occasion. But if you race your car, that’s RACE, wheel to wheel, not time trials or autocross you NEED Carrillo rods which come with the best rod bolts (SPS CARR, still the weakest link) available. You have to be honest here. If you do not RACE, factory parts are best with ARP rod bolts, otherwise you are playing Russian roulette without Carrillo rods. Again RACING is just like on TV with NASCAR, wheel to wheel, anything else is just playing around.

[Cookie Porsche]

Again RACING is just like on TV with NASCAR, wheel to wheel, anything else is just playing around.

Snowman. That IS what I mean about racing in my post! We 'bang' wheels, each other and sometimes other things... hell, we're even on national TV too...

Fact is - my car has been ultra reliable (and before asking - Yes, very competitive) using the FACTORY rods and bolts.

Of course a great driver looks after his car.

Regards, Tom

[snowman]

If you do not have Carillo rods and bolts, you will eventually wish you did. They are the ONLY ones that do not break a lot. All the others will and do break, much more often than one would want.

[TonyG]

snow

I agree on the Carillo rods. No argument. Purchased a few sets in my time thus far.

But the short block I have now, simply ain't got 'em. As such... I just want to know where the realistic limits are, with respect to rod/rod bolts on a stock 964 short block that will see a little track use before I install the new short block (which is far more stout).

TonyG

[racing97]

Somewhere you should be able to find the power curve of your engine in graph form as published by the manufacturer. Go 500 rpm past the peak HP to provide a good area under the curve, it should provide you
a safe operating range and a practical one for performance. It could be lower than the redline that is indicated on the tach. If you have made modifications use a chassis dyno to verify the same situation bearing in mind the factory warning.
Regards

[snowman]

Its quite simple. Rod bolts are and most likely always will be the weakest link. Carillo rods are designed around the best bolts available, sps. They are x rayed to guarentee they do not have a defect that can explode your engine. NO other rod or bolt can do this for you. Even if you stick to the factory red line, and your rods or bolts have a defect, and you don't know it, because they wern't tested, x rayed and so forth, kaboom. Its like shooting dice. It might be ok for 9 out of 10 engines, or NOT. As long as you understand this, and are willing to roll the dice, WTF. Otherwise there is NO way to tell. From what I have seen with real racers, its not 9 out of 10 but more like 2 out of 10 and even then they end up with Carillos in the long run. Think about it, your talking about an extra $600, the difference in price for Carillo rods,for an engine that cost how much????

Almost 100 percent of racers, that have been racing for a while, and do not have engine failures, have Carillo rods. Its really simple, you get what you pay for. If you don't test it, Thats 100 percent testing, you are rolling the dice.

To answer your question, You can't, why, because you haven't 100 percent tested all the parts. Also they arn't the best parts available.

[TonyG]

Guys...

I understand rods and rod bolts. We have used many sets of aftermarket steel as well as a few sets of TI aftermarket rods on various engine projects in the past (and present projects).

I understand that the rod bolt is by far the most stressed part of the engine.

I am not asking if I should use aftermarket rods and/or rod bolts.

I am not asking what the benefits of aftermarket rods and/or rod bolts are or if they are even a good idea.

I am simply asking what the stock short block is good for with respect to rpm, based on experience of people using stock 964 short blocks in club racing environments.

Yes I have factory manuals. Yes I can see the redline on a stock tach.

Please... just those with direct experience of running a stock 964 short block (with or without other engine modifications) in a club racing environment, on large tracks need reply.

For those of you that fall into the above paragraph, what are you taking the short blocks up to with resepect to rpms.


Thanks...

TonyG

[Cookie Porsche]

Hello - anybody out there...?

Knock knock - are my posts invincible?


I have in the shop TODAY:

1x 964 RS Clubsport - Original factory race car from Europe with 3.8 race engine. The car RACES with standard rods.

1x 964 RS Race Car 3.8. The car RACES with standard rods.

2x 993RS (one is an original factory Club Sport). Original rods.

1x 964RS 3.6 Club Time Trial Car - you guessed it. Original rods.

Now - aftermarket rods ARE good and may sometimes prevent failures. Many webcrawler experts will sing the praise of all things aftermarket - hell, I've seen a lot of crap from aftermarket sources. Just because it is sold as a 'racing part' doesn't mean it is.

Remember. I have NEVER suggested that one runs with 10 year old parts. I did mention that earlier. Of course no 10 year old rod bolt can be expected to compare with new parts.

FACT IS - in the real world many race cars run perfectly on factory parts.

The answer to your question is in my posts above.

Regards, Tom

[911-32]

Tom,

Very useful posts, thanks.

Are the 993 rod bolts better than the 964 ones? I was told the 933s have a stretch type rod bolt like the ARP rod bolts. Is this true?

Many thanks,
Richard