ALFAGTV6.COM

[SydneyJules]

Jim, kevin, Zamani, MD, Giulie Evo- Anyone!!!?? care to comment further on this?

I've been toying with where to go with my engine plans for down the track.

They stand at:

Greg's blower kit. Rebuild my engine with S cams, strong rods, 8.5:1 comp, 15psi, air/air cooler and custom pipework.
Pros: massive torque and HP.
Cons: Lose the romance of an NA engine, lose the revs (I love the revs).

Bore out the 2.5, keep the Group A cams and build a 6 throttle manifold out of a Nissan GTR manifold (AHM stuff is a bit ridiculous $$ wise once you exchange currency and freight it)

I'm leaning towards the second option, to have something unique. I can do a lot of the work locally, too.

I don't want to go 24v. I just don't want to start accumulating engines, and short of someone needing a 2.5 for competing in a certain class, I can't see many people wanting to spend the $ on a 2.5 like mine when you can get a 24v for less. So I want to keep my engine and make it go harder!

The 6 throttles is a must- these cams mean that each cylinder really robs the airflow from the others. With the plenum and single TB, it really sings once it gets going, but I want more torque and better throttle response. As it stands, the ECU and the ITBs are the only things I can do to my 2.5 at the moment. Everything else is worked.

I can get help making runners and a throttle linkage for the GTR manifold

I figure that sizing the runner length for midrange torque, it will behave a heap better in the 3-5k range and still rev to at least 7.5k cleanly. The GTR ITBs are for a 2.6, so well-sized.

No one can really tell me how far i can go with the 2.5's bore.

Jim, do you know? I have your book on the way, so if it's in there, I'll know soon enough!

No one bothers with the 2.5, for obvious reasons!
I figure I can go close to 100mm from a previous thread I started and from what PACE has said.
100m bore gives me a 3.2.... That would be a sweet engine with my cams and ITBs. I'd be happy to leave it at that.

Anything else I can do to make it a bigger engine and still keep my Group A cams? (ie stroke wise?) or am I going to have issues with the wild cams and valve lift?

It will need custom pistons, but where do I get the liners? I'm thinking I remember SA talk of Cummins Diesel liners with the height machined down to fit in the 2.5 block (which will have to be machined, too).
I guess it may also need bigger valves, to flow for larger CCs at high revs.

I'm not going to muck around with a 2.8. If I'm going to the extent of machining the block, I want a big capacity increase.

I love these cars, I love my engine- quite unique- and I want to make the most of it, but once I've done this, I will put the "car" bug to rest for a while and concentrate on other aspects of life- I want to do it once, do it well, and just enjoy it!

[75evo]

Jules,

12:1 comp, custom cams with new lobe designs, ported heads, 3L valves, ported runners, i think this should be good for 210 bhp or more.

Forget about going fast, cheaper just to buy a used evo or something as a daily car. But the is something a bout screaming N/A Alfa engines

Even as a daily driver I got a car similar to a Euro-R, 7600rpm.

[fedezyl]

I'd go the supercharger route though....easier, cheaper, faster and definetely bullet proof if you go with aftermarket ECU.

Just take care of that gearbox....
At least that's what i'm going to do probably next year with the Giulie

[SydneyJules]

Remember zamani, my engine is already running 11.3:1, with stainless, 1mm oversize valves (3.0 size), custom valvesprings, ported heads, rods- shot peened, lightened, linished- all balanced tO the crank, with ex- Luigi racing GrpA cams- it spins to 8000 without hesitation. I cant imagine a better set of cams exist for the 2.5 than what i have. It was built to the same specs as the groupA and C engines raced in Oz with leftover bits when Alfa departed Oz in 92- It made 138kw at the wheels a few years ago- it's starting to get a little tired (rings- not bad, just noticeable), so I'm planning what to do when rebuild time comes in the next year/2.

If I supercharge it, I'll lose the beauty of it- may as well sell the rods, pistons, cams and 4.3 diff- they're all matched- if I can, because I'll need new ones- and gain an awesome animal- the cost is large, and I'll begin to threaten my gearbox. With all the headwork, and big exhaust it should perform brilliantly under boosted conditions. To say I like the idea would be an understatement.
Rough costing- blower and piping+I/c- 6k Aud, pistons, rods and cams, 4k AUd. Rebuild 2k. So call it 15k together and tuned, for about 350 flywheel horse. And heaps of torque. Nice.
Still, running forgies on a streetcar can suck and it would really need a 3.9 diff (nearly impossible) to hit the sweet spot between riding the torque and accelerating hard- possibly a high 12sec quarter in a straight line- and let's be serious here, these cars need less attention in the handling department than they do in a straight line!

I think I really want to go bigbore- if the cops pull me over, there's just a v6 in there, so no roadworthy engineering issues (eng.'s certificate req'd in NSW or they can remove your roadworthiness- harder with blowers/turbos).
There's less gearbox stress, and I live the unique nature.

If I bore it out, it will be like a bigger, torquier version of what I already have (and love).
Some complexity is lost in the end, by keeping it NA, except of course, the buiild process itself and for the 6 throttles (linkages, tuning with Tps vs rpm), Barry (Kevin- can you get him back here!!??) suggested using (factory cast) bike pistons (bolts designed to rev) because they're available in 100mm bore, then use custom rods to get the correct CR. Cast pistons mean good drivability, and without the blown pressures, im pretty sure I can get away with it.
I can build the 6 ITB setup in the meantime, and it will make the 2.5 a crisper, torquier little thing, while I accumulate bits for the big bore.
Thinking I'll buy a junked 2.5 to start fiddling with- it should be cheap- and start looking for diesel liners that I can machine down to fit in the block.

I need to figure out how much the machining costs are going to b

[GTV27]

Increasing the displacement is a expensive way to go (custom rods/pistons and lots of machining with a high risk of stuffing up the block). Can understand not wanting to do it for a 2.8 litre (doubt that I'd proceed down that path either given availability of 3+ litre engines now).

Given the rego/police issues (I've kept mine looking VERY factory for that reason too), how about a 3.0 12v - the extra capacity will help plug the torque hole and it will still rev OK (piston weight and speed is still OK for 7000ish - not that I rev my own beyond 6500!).

Alternatively, keep the 2.5 and try the ITB option. I'd alway thought that the factory manifold and throttle body ADDED low down torque not detracted, so would be interested to see if ITB and long trumpets helped. You may have rego/police issues with that thou' (but as these things get older and less common, they become less of a 'target' and who knows how they're supposed to look anyhow!)

[SydneyJules]

Hi Jason!
Look- I accept that either way, there is going to be a fair amount of $ needed to be spent.

I won't go down either route by halves- this is not just for me, but also for our cars and our marque- it's nice when we can see what an Alfa can do! Unfortunately for me, the guys I've associated with have set the bar high- Fab's Twin Turbo 3.0, Paul K's 1.8 Turbo and Jim L's Alfetta Sedan Nord Turbo see to it that I want to do some justice to this 2.5. Yeah, I'll admit that there is some keeping up with Joneses in it, but I want something interesting for myself, too. And the more I think about it, I'd like to go NA- there's a certain romance to it

A 3.0 or 24v is pretty much out of the question- I don't want to start all over again- I already have a really good base to work with- My heads have had big $$ spent on them and if I go NA, I can almost leave them alone. To blow it, I have to change the cams.

I'm also leaning towards the big bore because there are less ancillaries involved. I can leave the engine in while I buy a crap 2.5 and get stuck into its' block to keep mine intact. Then just swap the heads onto it.

Re: The ITB setup- I don't think you realise how lumpy my cams are! Talking to my BMW mates (2002 Sport Sedan with an ex Brabham F1 turbo donk stroked to 2.0), and Vin Sharp from PACE has explained the cylinder robbing that happens at low to mid rpm-
The profile of the cams is REALLY optimised for about 4-8k. I think it made peak power around 7900- so with the single TB, the engine is restricted to what it can breathe out of the plenum- even at WOT.
At idle and lower rpm, the ability of the engine to get the air it needs is restricted, because every other cylinder has had its' airflow interrupted by the one that fires before it.
The ITBs allow each cylinder to breathe, without scavenging the plenum of air that the next cylinder needs....the idle, part throttle and mid range which are affected by the cam lobe's profile are smoothed out because they can breathe individually.
This was what was explained to me, anyhow!

Soooo.... sizing the trumpet/runner length for mid range torque will give better cylinder filling in that rev-range, from what I understand (shock wave travels from an opening inlet valve, up the runner, hits the trumpet, and returns with fuel/air mix in time to fill the cylinder through a still-open inlet valve- lower rpm means longer opening period for the valve, so the inlet runner needs to be longer to allow for the greater time).
And because the cams will never have an issue breathing at high rpm (they are made for it), having ITBs means it will breathe better at high revs anyway, or at least better than it does with a single TB, even though the runner length isn't optimised for high revs, it will be way better than a single TB plenum
Chatting to a guy who builds sprint car 350 Chevs and the occasional hot, stroked, street/drag motor, he talks of the extra capacity as being able to "iron out" the lumpiness by covering up the erratic breathing with capacity (Cubes), so if you build it to rev (which we all know, means $ no matter what sort of engine you're talking about), you will have the best of both worlds- high rpm and good midrange torque.

Yeah, it's all bore and no extra stroke (unless someone can point me in the right direction, there), but from what Vin Sharp said about an engine he built years ago, it had so much torque it would just light up the rears and step sideways if you didn't feed the throttle in.
If I can get an extra 700cc out of my engine and keep it revving, it will be a sweet, sweet thing, with the torque to match it's redline- and the induction noise of 6 ITBs is right up there with the sound of a big turbo coming on boost, IMO!

The idea of using the bike pistons (I recall Barry saying somewhere that he had used Yamaha ones on a big bore engine) is that they will have no troubles with RPM or power (weight/bolts) and be cast, giving me a nice motor that warms up quickly, so less wear. And cheap enough to offset the cost of custom rods.

The problem I need to tackle is the liners and block work.

How much machining was involved in your 2.8?

[GTV27]

It is a shit to get the liners out without cracking the block. The corrosion risk where the liners seat mean even when you get them out, you may have to find another block and start again. My engine builder did not want any repeat business on this job.

However, FWIW I fully support the NA choice and think the extra bore and short stroke will make make for a great engine (I really do rate my 2.8 and a 3.2 should be even better, and ultimately it is totally your call as to whether it is worth it).

Sounds like your cams are a bit extreme for a road car. Friend of mine bought a gtv6 ex-sydney with a full race engine in it - it was scary fast from 4500 to 7000, but was scary slow below that. It really needed a close ratio box to make it work. He drove it on the road too and it was either bunnyhopping or wheelspinning. If you are going to rebuild, maybe a less aggressive set of cams would make life easier for a dual purpose option.

[SydneyJules]

Hmmm interesting re the block....

I will digest and reply shortly !

I drove mine on the street for about 4 years! It's peaky, but pulls pretty cleanly from about 2000- it comes alive at about 3500-4000 and runs straight up to ~8. But with the 4.3:1, pretty drivable. If I could stack the gears closer together it would be better again, but I'm not going to chase that path down unless I have to. The gearbox is in good nick, so if the synchros start to go, I may look at doing a mash-up gearset.
The ancient ECU is letting it down- no ignition control- just the dizzy. I'm sorting that shortly.
And the ITBs will do it a world of good in the throttle response just by allowing each cylinder to breathe individually.

I went for a ride in an angry, microtech injected Escort RS2000 a few years ago. It had a plenum and single throttle, and would sing from 4-7k, but horrible below that. He made up a plate and runners for GSX-R throttle bodies and it was night and day- smooth idle (well not smooth, but easier to tune!) and it picked up so much urge through the mid-range. It was his daily driver too. Ran a 14.2- not bad for an Esky!

As for the big bore, I guess the limiting factors will be
A) getting the block sorted
B) getting the rods made correctly to suit the pistons so as not to screw the CR up.

If that doesn't go smoothly, then I will seriously look at sticking a blower on it!

There was that guy in Germany that put a Sei 2.5, bored to 3.3 in his Junior- so it has been done. He ran triple webers in the valley. Barry thought that 3.3 (104mm) was pushing the boundaries of good faith...

I will call Vin Sharp and have a good chat to him again soon, too. He and Fab (my mechanic) get along great guns, too, so between Fab, his Dad (who was chief mechanic to Colin Bond and Alan Jones- hence the current state of my engine) and Vin, I should be able to start the ball rolling.

It is always good to garner opinion and others' experiences before diving in! Thanks for sharing yours.

I just can't help but imagine all that Bore spinning at 8k. I'd have near on 300hp and so much more torque that the gearing wouldn't matter!

[Duk]

If getting corroded liners out of the block has a high potential to crack the block, why not have the old liners machined out?
It would be a fare bit of work for the machinist, but ultimately the block has to be machined to accept the larger liners any way.

I also remember reading about using bike pistons in the big bore engine, but I think that was for the 24 valve engines as all of the performance Japanese bike have been 4 valve per engines for quite a while now.

Not that I can condone such a thing , but how about a centrifugal supercharger? A more progressive torque curve that would deliver plenty of top end squirt with less chance to smash the transaxle.

[SydneyJules]

Cheers Duk- maybe it was a 24v thing.... just figured out the Ducati 999 has a 100mm bore...

If I was going to go blown, I'd go with Greg's kit- he's done all the work!

Reasonable idea with the liners...

[Giuliettaevo2]

I've never seen a v6 block crack due to taking the liners out.. Not even in my last 24v where the complete liner was cracked from top to bottom the block was still perfect and it has been reused with other liners.

From what i remember from reading about all the big bore conversions it were Honda motorcycle pistons.. And the liners were some kind of truck application, i have MAN in my head... But any good enginebuilder will have a catalogue with different liners, there will always be machining needed for them to fit so you can just take a liner that has good dimensions to work with.

NA is indeed very nice with the open trumpets... Would also keep the torque lower so gearbox failure is less of an enemy. 8000 rpm screamer would be very nice but not for a daily driver...

[75evo]

Get another car for a daily driver. But make this thing a special 8K screamer. 12:1 comp, new cam designs, big bore headers?

Jules, those older race cams were good for their time, but I was told by Richard Jemison, cam designs have moved on. The olde skool CB cams are just that, olde.

I don't know about the Luigi cams, but the only way to find out is if you put both on a cam doctor and see which profile has more area under the graph. Also, with custom cams you can tailor the overlap, LSA, etc.

Use 164 12V runners, which are 37mm, but cut them like how JimK did for his 24V. Then weld the 164 plenum stubs onto the bottom of the GTV6 plenum. Instant 3mm increase over stock. And you get to use newer injector styles which are easier to find and replace.

Throw away the dissy and go for a CDI. My dissy has so much play in it .

[SydneyJules]

Thanks Z...everyone!

I don't want multiple cars!

I'm going to continue this thread in the introduce me section to keep it neat

[kevin]

Jules, right now a friend and I are preparing a car to race as a 2.5 with allowances to go bigger in capacity.
Our first and most expensive option would be to have a 8000 rpm screamer like yours. As I have already been in your car I know it's Dam fast but we don't want to sit at that rpm with our non factory boxes and and fairly standard props so we are looking a more torque
Our cheapest options for us in order are
1) 2.5 12 v motor from 155 with few engine mods ie cams , comp , go tech and new intake (est cost R10 000 ~ 2000 oz dollar
2) 3.0 12 v motor standard with ljet R 11000
3) go 2.8 with standard 3.0 alfa sleeves and pistons and boring with new belts leaving existing crank and bearings as they are good R12500. We never worry about liners cracking blocks but we worry about studs pulling out.

So Jules if I were you I would pop in a standard 3.0 12 v in as in your case it would be the cheapest as you don't have access to all the machining facilities I have . Definitely not a 24 v as it's soooo much work . Then when you get bored take out jims book and start playing with that 3.0 v.

[GarthW]

Supercharge it. Why havent you considered turbocharging?

N/A wont give you 450nm. You will have great HP, but torque is what moves the car.

At least with boost, and a good ecu, it will give you better fuel economy, with greater HP. I used to love the revs also, but once you have that torque and pull, you soon forget about revs, and in this day and age, where you going to rev it out to?

The 2.5 is very strong, 15psi is nothing.

If your all wondering why i havent posted anything, no updates, etc, i've had a massive hiatus, i nearly died 8 months ago, well i actually did, a shot of adrenaline saw that i didnt, after that experience, i didnt even look at my car. Just now i'm starting to walk into the garage and wanting to drive it again, but i'm also considering selling it. I invested alot of money into it the last 2 years, but after what happened to me, i just feel different, but will know i'll regret it if i do. But life goes on...

So basically in this day and age, i wouldnt bother going N/A, just boost it.