RPM limit on 3.4 w/ arp bolts?

[DUK]

Just wondering what the rpm limit is on a 3.4 with stock rod , arp bolts, dc20 cams, Nickies, J&E's 9.5:1, ported heads and intake, headers, dc perf. springs?

I'm thinking in the 7000 range, is that realistic. Looks like the cam should pull atleast to that point.

[Steve@Rennsport]

Originally Posted by DUK

Just wondering what the rpm limit is on a 3.4 with stock rod , arp bolts, dc20 cams, Nickies, J&E's 9.5:1, ported heads and intake, headers, dc perf. springs?

I'm thinking in the 7000 range, is that realistic. Looks like the cam should pull atleast to that point.

JMHO, but I wouldn't turn it over 7k.

[88-diamondblue]

DUK, I have the same setup except I have he DC-22 cam and had talked with John at DR Camshafts and SteveW @ 911chips and decided to set the redline at 7200. It was set at 6800 to start with and I was bouncing off the rev limiter in 1st & 2nd consistently. I have not been at the rev limiter since we changed it, in fact I haven't seen anything over 7000 with throttle being applied. I believe 7000 is very realistic as Steve says.

The other thing that I am learning is to shift sooner and being able to drive in a higher gear (lower rpm) due to having more power. Do a dyno run and see where your engine is making the most power. I will be doing this in the spring. Last run of the year that I did I ran higher gear through our favorite local run and was in 4th gear through what I used to run in 3rd. I am learning the highest RPM is not necessarily the fastest way to go

[cstreit]

Rev limit is as much a function of your valve spring pressure as the strength of your rods. I certainly wouldn't go above 7k to be extra safe as I'd start worrying about valve float depending on the condition of the springs. That said, I us a higher rated spring from EBS, with stock rods and J&E pistons and rev to 7300. Engine has withstood numerous accidental excursions to 8k.

That said, the last sustained one (oops I calibrated my tach wrong!) to 8k resulted in a spun rod bearing. However the damage was limited to the rod bearing and rod itself

[DUK]

Thanx guys, that's exactly what I wanted to hear.

Chris which ebs springs are you using?

[88-diamondblue]

I put in DR Camshafts performance springs which John recommends a max RPM of 7500 which I hope I never get to...

[JeremyD]

7200 here -

EBS performance spring set, titanium retainers here - 993 ss cams

[ChrisBennet]

Originally Posted by JeremyD

7200 here -

EBS performance spring set, titanium retainers here - 993 ss cams

I'm interested in your tach. Is it a modified Porsche tach or aftermarket?
If modified, who did the work?
thanks,
-Chris

[JeremyD]

Modified original tach by North Hollywood Speedometer

Quote de JeremyD

7200 here -



EBS performance spring set, titanium retainers here - 993 ss cams

I'm interested in your tach. Is it a modified Porsche tach or aftermarket?

If modified, who did the work?

thanks,

-Chris

[DUK]

Hey, who's stealing my thread? J/K. I like your tach also Jeremy.

[911st]

Originally Posted by Steve@Rennsport

JMHO, but I wouldn't turn it over 7k.

Dose this mean that even with the up grade bolts the rods remain a weak spot?

Or dose oiling through the crank become the concern with the 3.2/3.3 crank?

[JeremyD]

I was more concerned about the valve springs at the higher RPM's.

Porsche valves are pretty heavy in the whole scheme of things.

[34Carrera]

Originally Posted by DUK

Just wondering what the rpm limit is on a 3.4 with stock rod , arp bolts, dc20 cams, Nickies, J&E's 9.5:1, ported heads and intake, headers, dc perf. springs?

I'm thinking in the 7000 range, is that realistic. Looks like the cam should pull atleast to that point.

I have a similar setup and asked Bruce Anderson the same question and he did not think it was wise to bump the RPMs up because of the stock rods.

[911st]

The stock "rod bolts" are known to be a weak point on the 3.2 /3.3 motors because of there reduced size compared to the SC and earlier bolts.

I think Porsche used stock bolts on the Club Sport and took the RPM limit to something like 6850.

7000rpm should be more than fine I would hope w race bolts. With lighter pistons like J&E's one should think 7k would be well within reasonable limits for even race duty but I do not know that for sure (I would do it.).

There just has not been that many reported stock rod bolt failures it seems. I think I have only seen one reported in all the posts I have seen here and I think that motor saw a lot of race duty.

Valve float should of course be addressed (springs and/or lighter retainers - talk to the cam supplier) and at some point crank oiling (pressure limit and or cross drilling) depending on how far up the RPM range we reach -- but those are separate points.

To me the question still remains: with race bolts what is a reasonable limit w stock pistons and or with light weight race pistons.

[Steve@Rennsport]

Originally Posted by 911st

To me the question still remains: with race bolts what is a reasonable limit w stock pistons and or with light weight race pistons.

As above,....

Remember, rod failure (due to either bolts, oiling issues, or heavy reciprocating components) is a catastrophic event leaving VERY few usable parts.

Its all about insurance and how lucky you are,....

[911st]

Originally Posted by Steve@Rennsport

JMHO, but I wouldn't turn it over 7k.

Sorry, I missed this. I guess 7k must be about it. Thx.

Wonder how far we can go with proper rods.

[Steve@Rennsport]

Originally Posted by 911st

Sorry, I missed this. I guess 7k must be about it. Thx.

No worries, mate,....

Wonder how far we can go with proper rods.

Thats dependent on several oiling mods, proper bearings, valve springs & retainers, camshafts, pistons, and of course, head airflow modifications.

Naturally, one needs to ensure that the intake and exhaust systems are up to the task.

I've seen several 2 litre engines make good power to 9K+ and larger engines to 8500+.

The harder you run them, the shorter the lifespan,....

[DUK]

The harder you run them, the shorter the lifespan,....

Exactly why I'm thinking 7000 sounds good. I've heard a couple of 3.2's in the 6800 range and it was SWEET.

[911st]

I find it fun to go to 911Chips.com dyno section and study the graphs when it comes to 3.2's.

I think there is a TRE build for a stock class where the motor is still making HP at 7k if I remember right.

I chiped and did a cat delete on my 3.2 and found that even if could go to 6800rpm for a DE I often short shifted on the track except when it was the time trial part.

I have seen reports of stock block 3.2's that were made to breath with proper exhaust and ITB's or carbs making around 270fwhp with the stock ports and cams so I am not sure how much they need cams unless it is bigger motor or the motors effecency is going to be moved to higher rpm or such.

I have wondered about re-timing the stock cam to early euro SC specs. One thread a 3.2 owner played w re-timing his cams and found I think about a 3% difference in hp up top or mid range. For him his conclusion was that with the stock trans and for the class he was running it, setting the cams for TQ may be an advantage.

[spuggy]

Originally Posted by 911st

There just has not been that many reported stock rod bolt failures it seems. I think I have only seen one reported in all the posts I have seen here and I think that motor saw a lot of race duty.

Well, you can add two street-driven cars to that total that I know of personally, one of which I have the invoices for...

Originally Posted by 88-diamondblue

Do a dyno run and see where you the engine is making the most power.

That's very good advice. Without real numbers, it's all guesswork. "seat of the pants" is not accurate - I was very surprised where my 3.3 made peak power.