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

[jehintheuk]

Carrillo CP-X Series pistons - https://lnengineering.com/products/cp-c ... ml?limit=8 bought as a set with the Nickies from LN Engineering
They are quite domed (10.5:1) pistons but I don't think the twin-plug was really necessary because of the CR. It was more a mid-range driveability/pickup issue with the 46 PMOs. I think it you wanted to run a higher static CR, or had a higher dynamic CR (because of better induction and exhaust) it might be more necessary to protect against detonation and/or to allow you more flexibility with the ignition timing. I don't think you would be likely to have any detonation issues on 98 ron fuel with a 10.5:1 static CR.
Twin-plugging the heads is actually quite cheap from a machining point of view, it's the ignition system that costs the money - especially if you want a traditional set-up or look. If you are happy to use a crankfire or coil-pack set up I don't think the cost needs to be that expensive.

[911hillclimber]

Thank you again.
Being a hillclimb car it is WOT almost 100% of the time. Sometimes it is an advantage to leave one corner in a tall gear/ say 3000 rpm and WOT to the next arriving at a better entry speed in the same gear.
My engine is on 50mm PMO and free flow exhaust system/see-through silencers.

I like to keep things as simple as possible in all areas of this car so would prefer to keep 6 plug ignition, but understand the limitations of the dizzy system I have now (points and condenser, FoMoCo coil)

[jehintheuk]

Doh, I hadn't twigged the engine was in a specialist hillclimb car, rather than a road car used for production or modified hillclimbing! The experience with my engine is probably of very limited relevance. However, I do think the 66 911 cam is better low down than the S, yet gives very little away to the S cam at the top end. It was also designed for carbs, albeit on smaller capacity cylinders. A bit of a forgotten option imo.

To be honest, as it is a specialist car and you aren't worried about a traditional look, like I was, why not go for a twin spark crankfire set up - it's simple, has no moving parts to bounce - and will protect the engine with higher compression pistons. Machining the heads for the second plug is straightforward and relatively cheap if you are changing the cams and upgrading the valve springs anyway. The only remaining worry I would have then would be the con rods, I can't remember from the earlier part of the thread if you are using standard rods and bolts. The BA book indicates the standard 3.2 rods (but not the 3.0) could be a weak point in a high revving engine.

PS What do you plan to do with the little CB when you've finished it?

[911hillclimber]

Yes, and why I drop pictures of the car in to illustrate the kind of car I'm dealing with!
The rods are stock 3.2 with stock rod bolts which are much smaller dia than the 3 litre and earlier rods, and Bruce does highlight this weak link in his excellent books which have been my bible for years.

As to the little cb175 the plan is to actually keep it since I 'gave away' my gold one a few years ago.

[map]

Know you're not necessarily keen to change your gearbox but this came up on another forum and at £650 might be useful.

986 5 speed with KAZ diff - you'd need to validate the ratios for your car, mountings etc but the "hard bit" in terms of linkage/shifter should be an easy win given it uses cables (designed for mid engine) and a "bolt in" shifter cage so all these parts are likely to be factory/stock. This gearbox is reckoned to be pretty strong - albeit the guy selling is putting a modified Audi S6 turbo engine in his 987 which is his reason for selling.

https://www.boxa.net/topic/91519-5-spee ... nt-1252502

[911hillclimber]

Have spent a long time looking at Boxster and the cheaper but similar AUDI 1.8T boxes.
The bell housing 'diameter' is too big to squeeze into the chassis frame and the fuel tank position stops the cables from passing through to the cabin of the car!
There are also some difficulties with adapting the box and engine interfaces let alone the clutch itself!!

A full Boxster transplant gets over a lot of these issues but the engine is too wide then, and I have to add water cooling too....

Simplest solution is to rebuild to a revvy engine, at Prescott hill I would do the whole hill in 3 gearchanges.

[map]

Have spent a long time looking at Boxster and the cheaper but similar AUDI 1.8T boxes.
The bell housing 'diameter' is too big to squeeze into the chassis frame and the fuel tank position stops the cables from passing through to the cabin of the car!
There are also some difficulties with adapting the box and engine interfaces let alone the clutch itself!!

A full Boxster transplant gets over a lot of these issues but the engine is too wide then, and I have to add water cooling too....

Simplest solution is to rebuild to a revvy engine, at Prescott hill I would do the whole hill in 3 gearchanges.

Fair enough - that's a chunk of work, certainly more than I'd contemplate.

[911hillclimber]

Sorry to revive this thread..
Do you think £6000 would do this engine without new barrels and twin plugs?
I.e.
Rods, arp bolts, 964 cams, forged Pistons?

[MikeB]

Wossner pistons, bolts and rods £2740 from Design911, Kent cams any grind £740. Would suggest a S GE40 as it will be quite torquey in a 3.2. Plus all the usual engine rebuild bits

[911hillclimber]

Thanks Mike.
Contemplating selling the Honda to buy the parts, rebuild the current engine this winter, all diy of course.
The new mod to the distributor to Hall effect magnet etc has been good, but to go further down the track and avoid a gear change or two could really work on the times.
Lost a few seconds last weekend at Loton due to 2nd to Neutral instead of 2nd to 3rd, but still won my class..
A revvy engine, to about 8k, would give better times than a 10k Hewland box.

Iirc £1000 will buy the crank/ rod bearings and rebuild parts etc.

[MikeB]

Lightweight flywheel and/or clutch too if you haven't got them, but you may also need to uprate the valve train and possibly open the ports as well to get to 8k. Am not too sure when twin spark needs to come into the equation, my friend's short stroke 3.2 has been dyno'ed a 265hp on single plug and is still on CIS induction. But there are so many different parameters and many ways to achieve results from the Flat 6. But if you want to go to 8k you need a cam that suits, otherwise you may rev but you may also start to lose power. Am sure there are folk here who know what to do, if they are prepared to share their often hard found knowledge

[911hillclimber]

Have the light flywheel and clutch already.
The stock cams drop off a cliff around the rev limiter, bit like a diesel does when revved.
My conclusion earlier on was this is a lot of change for 1800 more rpm, but any move forward seemed to be the same no matter what course I contemplate!
Thanks for the help Mike.
I think there is a wealth of knowledge on Impact Bumpers that will be free flowing.

[hot66]

To get the revs .. you’ll also need to make sure it can breathe …not sure what the max air stock 3.2 heads can flow . Maybe need to open the ports / increase valve size ?

[911hillclimber]

Mike said much the same James, and if that is so I won't bother with any of it.

The 3.2 is just a big lardy 911 engine, lazy and not really suitable for this car and it's purpose.

Maybe I'm trying to get a silk purse from a pig's ear, and a fresh approach is needed. Boxster/gearbox or A4 turbo and box might be far better, the latter very cheap.
It is hard to keep going at this game at my 'stage' of my 'racing driver adventure'.

Been at it for 30 years this year.

[Bruce M]

1 bar of boost = hp * 2

Roughly. Not a kit though, you’d need to engineer it yourself. Turbos have never been cheaper, if you use a common unit like the K03. No need to crack open the engine. Just saying