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Beaky

32. vs. 3.2 with ITB vs. 3.4

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Ok silly question time,

As plans are afoot for my engine rebuild the biggest dilemma is what rebuild to undertake. In practical and simplicity terms it's either a straight 3.2 rebuild or you go exotic.

Considering the trade off of cost vs. real world drivability, performance etc. is there that much difference between a 3.2, 3.2 with ITB's and a 3.4.

Over to you my learned friends

 

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Don't want to teach you to suck eggs but:

Go bigger you end up with additional low down usable torque which is great for everyday driving & simple overtaking etc.

Go for ITB then you open up a lot of additional lairier cam choices so you can build yourself a high revving screamer.

Worth figuring out what you want out of your engine and what you mainly use it for then doing the sums for each option as it's all big bucks.

How come you forgot to ask about 3.6-ing it? That's the obvious & sensible choice ;)

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1 hour ago, ALEX P said:

How come you forgot to ask about 3.6-ing it? That's the obvious & sensible choice ;)

I wanted to keep the original engine and matching numbers, to go 3.6 I'd probably need to sell the original.

I use the car mainly for fast B road blasts and long weekends away fellow and close friends Porsche owners in the Uk and Europe.

Low down grunt and overtaking capability would be useful as I'm normally in the company of GT2/3's turbos etc and these just breeze past traffic!

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I'd do standard(ish) rebuild and put money into shorter gearing. Not exactly cheap to do with a G50, but if your gearbox hasn't been opened up yet you might consider going this route.

 

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Has anyone done a 3.4 and been happy with the result? Longmans suspected 3.4 is the only one I can think of. 

Ultimately getting more power than a remap = big bucks.

Horsepower sounds good in the pub. Suspension makes you get there faster.

If it was my money I’d probably go for a fairly standard rebuild with a lightweight flywheel/clutch (zing!), any nice bolt on upgrades and a proper remap. Then spend the money saved on really good damping, something like Ohlins, ExeTC.

Nice position to be in though 👍

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9 minutes ago, Northy said:

Has anyone done a 3.4 and been happy with the result? Longmans suspected 3.4 is the only one I can think of. 

Ultimately getting more power than a remap = big bucks.

Horsepower sounds good in the pub. Suspension makes you get there faster.

If it was my money I’d probably go for a fairly standard rebuild with a lightweight flywheel/clutch (zing!), any nice bolt on upgrades and a proper remap. Then spend the money saved on really good damping, something like Ohlins, ExeTC.

Nice position to be in though 👍

That's very true, so perhaps a standard 3.2 with cams, big bore throttle body, AFM , etc and the remap would do the trick.

I've already done the sports clutch, refurbed the suspension a few years back and GC just refurbed the steering rack and a small makeover of the suspension again.

mmmmm, decisions, decisions..................:unsure:

 

 

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Without any other mods a larger throttle body will likely do more harm than good. You'll just be throwing away lower down torque. If Porsche could have freed up some bhp by putting in a 3mm larger butterfly I bet they would. All these things need balancing. I reckon if my ITBs were 46mm they'd have sold already. People see that 46mm > 40mm and think therefore they must be better. I bought 40mm deliberately as they suited my 3.2SS application much better than 46mm butterflies.

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11 hours ago, Beaky said:

That's very true, so perhaps a standard 3.2 with cams, big bore throttle body, AFM , etc and the remap would do the trick.

I've already done the sports clutch, refurbed the suspension a few years back and GC just refurbed the steering rack and a small makeover of the suspension again.

mmmmm, decisions, decisions..................:unsure:

 

 

Maybe do a standard-ish rebuild on the 3.2 but add some nice bits like some lighter rods, ARP's, valve springs, cams etc.

Also, you could look at the intake, maybe put a 964 one on same as RB's old car, that made pretty good numbers and it wouldn't cost a fortune. Always nice to have someone do all the R&D for you first!!

 

9 hours ago, Kenny Senior said:

Without any other mods a larger throttle body will likely do more harm than good. You'll just be throwing away lower down torque. If Porsche could have freed up some bhp by putting in a 3mm larger butterfly I bet they would. All these things need balancing. I reckon if my ITBs were 46mm they'd have sold already. People see that 46mm > 40mm and think therefore they must be better. I bought 40mm deliberately as they suited my 3.2SS application much better than 46mm butterflies.

I must admit when I saw them I thought oooooooohhh, and it's Christmas! 

But they would be too small for me and I remembered how much Christmas costs :D 

Nice though - Surprised they haven't gone.

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The choice might ultimately be made by the condition of your engine. I was heading for 3.8 rebuild on my 964  but when engine was stripped P&C were good so ended up staying with 3.6  maybe good to do have various mod options in advance and then decide once the engine has been split & checked out. I believe you need cams & motec (or similar) to get the most out of ITB's so need to factor in the additional costs.

+1 on shorter gearing, I have a 3.2 with carbs in my 73 project that still has the original 915 box with 7:31 ring/pin, acceleration is brutal & has surprised a few. If your pistons are good & your budget allows it then cams, motec & ITB with a short ratio gearbox would make a great aural/visual & seat of pants improvement. BTW fuel consumption of carbs isn't as horrendous as some say so weber/PMO could be an option if budget is tight - additional fuel bill over efi will only be around 200 per 3000 miles (one year).

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Aside from ITBs, I think this has largely been covered before

If your old p and c don’t need replacing, I wouldn’t bother. Spend the money elsewhere, I like Lewis’ trick suspension recommendation, or gear ratio changes as above.

Boring/replating - spoke to Neil about this as I was contemplating going from 98 to 100mm, he’s only seen one set and the Nickasil (?) plating had started to flake off; no, he can’t recall who did the work.

Saying that, a 3.4 with 964 ish cams is a really nice conversion. 270+ bhp and 240+ torque can easily be felt, and you don’t need to rag it to feel the benefits. Looks standard too. Prices are a lot higher now though than when I bought the 98mm kit in 2008 (£2750)

Part of me is thinking I should have gotten Neil to do a straight rebuild this time round and not go mental with Gt3 crank, itb, etc. 

However, if you speak to likes of William Knight or Jeff Gamroth, they’ll show/tell you the 3.2 has lots more to give with changes to induction, cams, head work etc. Extreme example but William built a race 3.2 for a customer hitting over 350 bhp - largely down to very trick heads and cams, but still a 3.2.

Less can be more though.

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Thanks everyone for their input.

I'm now leaning toward a 3.2 with added bits, I'll have a good chat with my Indie and see where we go.

Have a great New Years 

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1 hour ago, SP72 said:

Part of me is thinking I should have gotten Neil to do a straight rebuild this time round and not go mental with Gt3 crank, itb, etc. 

Trust me, by the time you add up all the bills you'll be glad you went the extra mile for a very trick engine. BTW what is anticipated power on your engine?

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Once I've refurbished my suspension setup and addressed my exhaust im going to be in a similar position to you Beaky. 

At the moment I'm leaning towards cams, uprated valvetrain, ITB's and a decent ecu. I'm not chasing big numbers but would prefer a slightly a bit more top end freedom/revs (which in itself helps with gearing) 

Short ratio is probably last on my list unless my 915 dictates otherwise :)

Good luck with whatever route you take 

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No estimates from Neil (as expected)

With the SSIs that I have, I’m thinking 300-320bhp.  William Knight believes that if it had correct sized headers and with the cams, crank, rods etc its 100bhp/litre, so 350ish

 

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49 minutes ago, SP72 said:

No estimates from Neil (as expected)

With the SSIs that I have, I’m thinking 300-320bhp.  William Knight believes that if it had correct sized headers and with the cams, crank, rods etc its 100bhp/litre, so 350ish

 

That's going to be awesome, I'd be happy with around 250 - 260 ish.

The saved money will go towards Jonny's air con ;)

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6 hours ago, ALEX P said:

Maybe do a standard-ish rebuild on the 3.2 but add some nice bits like some lighter rods, ARP's, valve springs, cams etc

This is what I did. Love it....:twocents:

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22 minutes ago, Dr Rock said:

This is what I did. Love it....:twocents:

Do you have a build spec you can share, Ta

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1 hour ago, Beaky said:

Do you have a build spec you can share, Ta

STD crank, balanced, std flywheel and Sachs clutch, balanced , Mahle 3.2 barrels and pistons, balanced and half mooned, Carillo rods, std 3.2 heads, slight increase in CR, ARP stud set, std valves and springs, titanium spring retainers, Dougherty 993SS cams, std rockers, std 3.2 intake, inlets blended to the heads, SSI’s with Dansk s/s 2in1 out exhaust.

Originally had a Patrick Motorsports lightweight flywheel and Centreforce lightweight clutch, but they only lasted 4 days... so went back to standard items.

Pretty much sums it up. Much faster (161mph on the autobahn) :cool:than a standard engine.

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45 minutes ago, Dr Rock said:

STD crank, balanced, std flywheel and Sachs clutch, balanced , Mahle 3.2 barrels and pistons, balanced and half mooned, Carillo rods, std 3.2 heads, slight increase in CR, ARP stud set, std valves and springs, titanium spring retainers, Dougherty 993SS cams, std rockers, std 3.2 intake, inlets blended to the heads, SSI’s with Dansk s/s 2in1 out exhaust.

Originally had a Patrick Motorsports lightweight flywheel and Centreforce lightweight clutch, but they only lasted 4 days... so went back to standard items.

Pretty much sums it up. Much faster (161mph on the autobahn) :cool:than a standard engine.

Thank you

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And so the fun begins, She's booked in for a May rebuild slot.

P&C's have already been sorted 

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1 hour ago, Beaky said:

And so the fun begins, She's booked in for a May rebuild slot.

Just in time for the driving season to begin :rolleyes:

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54 minutes ago, Dr Rock said:

Just in time for the driving season to begin :rolleyes:

Oh, did it stop then?

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19 minutes ago, Lesworth said:

Oh, did it stop then?

Wasn't it due this Saturday!

Mine will miss my trip to the Algarve, (will take my son's Boxster) but be ready for the Classic and Spa

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