3.2 911 engine: mods to give 7600 min red line?

[911hillclimber]

Just a simple set of questions I need some clarifications on.
Stock healthy 3.2 used for hillclimbs, so WOT and lots of runs to the rev limiter.
Plan is to change the engine parts to run 7600/8000 reliably for short periods of time.

Strip the engine and replace stock with:
Pistons, forged, but what make? Must run in stock barrels.
Rods: Replace stock with forged beam item, which ones are popular for these revs?
Hardware: ARP in the rods, do I need to change case through bolts?
Cams: which ones to use? The engine MUST have good wide torque from low down.
Valve gear? what needs to be changed to titanium for these rpm or just change the rockers.

Engine is on PMO carbs and RS 2.7 dist and points. Plan to use a 2.4S rotor arm for rev limit, currently using a 2.4T rotor.

Anything else?

Please, just tech chat and not if my wife approves (etc)

[Jonny Hart]

What ignition are you running? We can give you the low/mid torque improvement.

[911hillclimber]

It is a 2.7RS dizzy, points and condenser with the 2.4T rotor arm, and that's it.

All set-up by Bob Watson about 9 years ago and untouched since (literally)
Carbs are too big PMO's and Bob squeezed 247 bhp from it, and about 210 lbft iirc.

[hot66]

Make sure it can breathe and flow enough air at that rpm ... after that make sure the valves won’t float and the rod bolts are up to spec

[redrobin911]

I'm a big fan of dougherty racing cams, and john (dougherty) will gladly chat oer spec and advise what will work best. I'd use his modern cam profiles before using std porsche ones, he does seem to to get cams to do the best of both worlds ie. I'm ordering my 3rd set of cams from him soon. I also used the H rods on ebay at £600/900 and they're perfect value for money, i normally use wossener pistons again good value. I believe that the performance is in the cams/heads/induction/ignition in that order. My 2p.

[911hillclimber]

Excellent!
I saw those £700 rods that have ARP bolts in them and wondered, so good to read.
Same with the pistons for £1214 from Design911.

As to valves, the 2.4S revs to 7600 red line on stock parts, but the 3.2's are larger so may need changing over the rockers and valve spring loads.

Those cams are the tricky bit, I also remember the GE cams being popular alternatives.

The engine had 50mm PMO, and will flow air for a stout 3.8 and certainly have free flow exhausts, so feel ok there.
Thanks for the comments so far!
G.

[KS]

Buy Wossner pistons direct from the importers (TSR) for less money. They import ARP, too...

https://www.forged-pistons.co.uk/websho ... tons-9255/

[911hillclimber]

Thank you Keith iirc you used those pistons.

[rhd racer]

I would definitely use comp valve springs Graham

Cheers

[KS]

Thank you Keith iirc you used those pistons.

I did - and they're used by Porsche in the SuperCup cars, among others.

[hot66]

2.4S / 2.7RS has a 7200rpm red line. I run my limiter at that although I know it can rev higher .. dyno work showed the port size / valve size was limiting any significant power gains going further up the rev range as it couldn't really flow the required air.

I'm running heavy duty springs & titanium retainers with ge40 spec cams ( forged blanks with fresh grind by kent cams .. essentially an S cam though )

[wadsworthi]

It all depends on how much power you want and how much money you want to spend Graham.

Get the 3.2 barrels bored out to 98mm by Capricorn and fit JE high compression pistons giving you 3.4 litres and around an extra 20 bhp.
Cylinder heads on 3.2 should be fine for airflow, but could do with some small amount of tidying work.
If you want the engine to rev to 8000 then Carillo rods (will rev to 8500) are seen to be a good choice by engine builders albeit much more than £700 although they do include rod bolts.
John Docherty produces some good camshafts with DC60 producing mid and upper range torque although DC80 will make it fly at the top end. It did take a long time for him to produce some camshafts for me as he is not always reliable with his timings. I think you will lose some lowdown torque with the higher performance camshafts, but John does give advice on this if you email him.
DC60 should allow you to retain existing rockers, but DC80 will mean upgraded rockers and springs, retainers.
I don't think you need to change case bolts, but with high compression pistons I think you will need twinspark ignition.
I would expect the above combination to get you to 300 bhp at flywheel with the DC60.
Just an opinion, but hope it helps!

Ian

[911hillclimber]

Again, thank you all for these tech details.

Ian, you know the hills, I want torque from , say, 2500 on to a fat red line so I can avoid lumbering through a long '915' gearbox gear change wherever I can.

Thus, the purpose of this thinking is to have a simple engine that can be run to 7500 or more at minimal cost but with total reliability, I've blown this engine up once and the cost was quite tearful.

I did not think of S cams in this engine, good info James, wonder if E cams would actually be better for low down torque?

The idea of twin plug heads chill me to the bone tbh due to cost but the pistons would have a tall crown compared to the stock 3.2 pistons.
Are 'we' sure the stock rockers can cope?

[coomo]

Agreed with Dougherty cams.Just be prepared to wait.Mine took about 3 months.Not very adept at replying to mails either.
Give EB racing a call/mail.They will advise on pistons, plus can do a deal.I got Mahle from them at better prices than Europe.
Carillo/Pauter rods appear to be popular.Again EB can help
Langthorpe charged me £1200 to go to 98mm and replate my cylinders.
Titanium retainers and tougher springs.

[911hillclimber]

Not that bothered to stretch to 3.4 from 3.2.
I know the barrels still have good evidence of cross hatching on the bore hone, so will keep them as is, fresh pistons that can take the rpm the order of the day, likewise the rods.
Extra power will come along 'naturally' due to increase in rpm.

A typical one mile hillclimb in the Lola takes me about 56 seconds from a standing start, I change gear just 4 times in that run (Loton Park) but should change gear 8 times to avoid hitting the limiter.

In places it is more time efficient to run to the line in 2nd, dip the clutch and go through the next bend in 2nd rather than ponder from 2nd to third and quickly back to 2nd.
With the longer rpm I can hold and still deliver acceleration in second, brake like mad and scoot out in 2nd.
It is the same issue further up the hill.

Please do not say change the box or modify the box, been through ALL of that discussion and do not have the energy to go through it again!
A box change will cost 2 x this engine change at least.