OK guys, with everyone adding inches to their reciprocating members, here is the inevitable question!
Ive spoken with Vin Sharp at PACE who says a 103.4mm liner can be fit into the 2.5 block to take capacity out a 3.4, and he says that the combustion chambers dont need to have the bowl diameter increased to match the new bore... what do you guys make of that? Barry? Jim K? Mats? Kev? Ben? Apparently an older engine he built blew headgaskets until the owner gave up on it... it could be trash talk.. you never know in Aussie alfa circles.
Considering my engine already has 1mm oversize stainless valves, is that going to be the limiting factor in head flow? Ie... will I need to get bigger valves and seats made up to take advantage of the bigger capacity? The heads flow 280hp at the Cams' max lift as is... so I think it will need to be done.
The way I see it, with no extra stroke involved, and a new set of pistons, I will be able to keep my cams for some pretty stonking top end, and add to the torque which is sorely missing from the little screamer.
And here is the killer, at a cost of around 12k by the time I get a set of six throttles and a new ECU, am I better off buying a 24v 3.7 from the SA boys, or building myself a competition spec (Rods, big GT25 and serious I/C) turbo 2.0 from scratch for slightly more money?
Which engine will be lighter over the front wheels? The turbo motor will have I/C and stuff hanging out in front of the wheels etc.
I now what a turbo 2.0 with the good bits is capable of doing, especially comparing it to Paul Kretzas' 1.8T which is an absolute weapon, but Ive got no idea on the comparative merits of new OR old big bore sixes!
Please discuss for me!
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SydneyJules
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Bore Increase on 12v 2.5
Fixing it bit by bit....
Come on Jules, you KNOW why you want a 6-potter. It sounds freaking sick at 8K RPMs. You know it! SO enough talk about the 4-pot.... even though a boosted 4-pot will blow your V6 into the weeds 
BTW, why not go with your original idea with the 3.0? Custom 11.5:1 pistons and rods, big bore headers and you're set.
Also wasn't there an ad... I think in Victoria's AROC newsletter or whatever that Beninca built 3.0 24V (dyoned at > 270 WHEEL BHP) for sale at around AUS$12K or something like that. I think I posted a video of it (it was in a red GTV6 on Beninca's dyno). It's a race spec engine so I guess it probably has looser clearence.
BTW, why not go with your original idea with the 3.0? Custom 11.5:1 pistons and rods, big bore headers and you're set.
Also wasn't there an ad... I think in Victoria's AROC newsletter or whatever that Beninca built 3.0 24V (dyoned at > 270 WHEEL BHP) for sale at around AUS$12K or something like that. I think I posted a video of it (it was in a red GTV6 on Beninca's dyno). It's a race spec engine so I guess it probably has looser clearence.
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SydneyJules
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Oh yeah Zed the sounds a big factor 
The pleasure I get from a windows down three gear smack up to 150km/h in my car still makes me smile... just watching the tacho smash its way up to 8k rpm is fun in itself!
But who's to say a big exhausted turbo 4 banger doesnt make a great sound- all that tortured air and turbine noise, and the wheelspin that goes with it... If only I had the cash to do both
Are you talking 24v 3.0? Or 12v...? I wouldnt go out and buy a 12v 3.0 to spend all that cash on it.
As for the Beninca option, I remember the Vid... it sounded hot... I like my engine better though
you know youre gonna get a good product, so it makes sense, but as it appears my car is going to go into storage for a few years, Im wanting to start stripping it- Im not buying anything just yet, I need to get a jobbie so my daddy can be proud
Then it will all start (again)
What's your take on the Big Bore work on my current engine- picture it with AH Msp. TBs and a Haltech or PMS ECU on it, with the 4.3:1 diff
The pleasure I get from a windows down three gear smack up to 150km/h in my car still makes me smile... just watching the tacho smash its way up to 8k rpm is fun in itself!
But who's to say a big exhausted turbo 4 banger doesnt make a great sound- all that tortured air and turbine noise, and the wheelspin that goes with it... If only I had the cash to do both
Are you talking 24v 3.0? Or 12v...? I wouldnt go out and buy a 12v 3.0 to spend all that cash on it.
As for the Beninca option, I remember the Vid... it sounded hot... I like my engine better though
you know youre gonna get a good product, so it makes sense, but as it appears my car is going to go into storage for a few years, Im wanting to start stripping it- Im not buying anything just yet, I need to get a jobbie so my daddy can be proud
Then it will all start (again)
What's your take on the Big Bore work on my current engine- picture it with AH Msp. TBs and a Haltech or PMS ECU on it, with the 4.3:1 diff
Fixing it bit by bit....
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Mezevenf
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Go on Jules, be different 
do up the screamer!
I recently got my tacho fixed, watching it hit 7k is awesome, I wouldnt take it as far as 8 though (jealous).
Personally I wouldnt go the 4pot turbo, only because its all I see day in day out up here on the coast/ricer central.
Make it a 3.4L screamer
Also, 4.3:1 dif? interesting.
do up the screamer!I recently got my tacho fixed, watching it hit 7k is awesome, I wouldnt take it as far as 8 though (jealous).
Personally I wouldnt go the 4pot turbo, only because its all I see day in day out up here on the coast/ricer central.
Make it a 3.4L screamer
Also, 4.3:1 dif? interesting.
Bernard M (AKA Mef - Mezevenf)
1986 75QV 3.0L 24v V6 - Silver
1985 GTV6 2.5L 12v V6 - Red
1999 166 3.0L 24v V6 - Red
NightSpec
1986 75QV 3.0L 24v V6 - Silver
1985 GTV6 2.5L 12v V6 - Red
1999 166 3.0L 24v V6 - Red
NightSpec
103.4 mm bore..Problems imo...
Id stick to a 100mm bore without welding heads up.This is safe..
If you weld the heads up,102mm bore max.Preferably 4 "(101.6mm)
Id use the headgasket as in the 20l turbo trhead ...
Also beware pistons touching opposite sleeves at bdc.You have to notch the sleeve...
Id stick to a 100mm bore without welding heads up.This is safe..
If you weld the heads up,102mm bore max.Preferably 4 "(101.6mm)
Id use the headgasket as in the 20l turbo trhead ...
Also beware pistons touching opposite sleeves at bdc.You have to notch the sleeve...
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French cars are shit and shit expensive to service and bloody awful and unreliable and expensive and friends don't let friends drive french cars and you wait years for parts.
Joolszzz,As soon as you go bigger bore,cr increases..obvious.
The 2.5 head chamber is way too small for a big bore and reasonable cr..At least take it out to euro/us 30l spec.,mo only..
Mmmmm....or run inverted dish pistons....mmmm....
The 2.5 head chamber is way too small for a big bore and reasonable cr..At least take it out to euro/us 30l spec.,mo only..
Mmmmm....or run inverted dish pistons....mmmm....
French cars are shit and shit expensive to service and bloody awful and unreliable and expensive and friends don't let friends drive french cars and you wait years for parts.
Z,No..Too much to offset downwards..but with some custom pistons or something from another manufacture.....Never know....
2.642cc`s...realy not worth it Id say...
2.642cc`s...realy not worth it Id say...
French cars are shit and shit expensive to service and bloody awful and unreliable and expensive and friends don't let friends drive french cars and you wait years for parts.
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SydneyJules
- Verde
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- Joined: Sun Dec 19, 2004 1:57 pm
- Location: Sydney
So Barry, If I am to go down that route, I would need to have chambers bowled out to match the bore? Or Just nearly to the same size? Will have a look at what you mean headgasket wise.
Because of the availability of 98 octane here (BP100 too) I would try keep the comp up around 11.5 or maybe 12.
What do you think about valves Barry?
Sounds like a fair bit of work to make sure that there's no hassles all round....
Are the stock rods (mine are shot peened, balanced to the crank and linished) gonna hold the bigger piston at those revs without any troubles?
Yes... there is something hot about the idea of a six throttle 3.4, and that allure is the problem... I know a turbo 2.0 would go harder.... but I reckon a lightweight 3.4 would make an awesome trackday car... which could possibly run a respectable drag strip number too, for an all-motor Honda bash up.
Bernie, I had the 4.3:1 when we met up, but to avoid the front of my car and that Falcon becoming one, I stopped my run in first gear at around 5... which is where my engine really starts to pick up. Its a bit of a dog below that!
Because of the availability of 98 octane here (BP100 too) I would try keep the comp up around 11.5 or maybe 12.
What do you think about valves Barry?
Sounds like a fair bit of work to make sure that there's no hassles all round....
Are the stock rods (mine are shot peened, balanced to the crank and linished) gonna hold the bigger piston at those revs without any troubles?
Yes... there is something hot about the idea of a six throttle 3.4, and that allure is the problem... I know a turbo 2.0 would go harder.... but I reckon a lightweight 3.4 would make an awesome trackday car... which could possibly run a respectable drag strip number too, for an all-motor Honda bash up.
Bernie, I had the 4.3:1 when we met up, but to avoid the front of my car and that Falcon becoming one, I stopped my run in first gear at around 5... which is where my engine really starts to pick up. Its a bit of a dog below that!
Fixing it bit by bit....
Jooolszzz,Firstly,Id look at Jap motorbike pitons if I were you...Way lighter than anything automototive or forged,AND cast clearences..
Yamaha make a 100mm and so does Honda....
Once you have the pistons and you have an actual piston top cc measurement,Id then do the chamber accordingly.To indiscriminatly hack out the chamber to a size and shape first is not the way to do it.Things to remember is as small a chamber as possible and as flat a chamber as possible..
The nice thing with a big bore is that there are oddles of space for REAL big valves if you need them..In the old days we would get a 2.25"chevy valve into that head...
Stock but prepped rods?Yes,as long as they are new as in latest generation gta or 164...AND good bolts..Those light bike pistons are worth thier weight in gold when it comes to the riods..and rods..hehe..
Yamaha make a 100mm and so does Honda....
Once you have the pistons and you have an actual piston top cc measurement,Id then do the chamber accordingly.To indiscriminatly hack out the chamber to a size and shape first is not the way to do it.Things to remember is as small a chamber as possible and as flat a chamber as possible..
The nice thing with a big bore is that there are oddles of space for REAL big valves if you need them..In the old days we would get a 2.25"chevy valve into that head...
Stock but prepped rods?Yes,as long as they are new as in latest generation gta or 164...AND good bolts..Those light bike pistons are worth thier weight in gold when it comes to the riods..and rods..hehe..
French cars are shit and shit expensive to service and bloody awful and unreliable and expensive and friends don't let friends drive french cars and you wait years for parts.
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SydneyJules
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- Joined: Sun Dec 19, 2004 1:57 pm
- Location: Sydney
Jeezuz Barry. One day Im gonna come over to SA and get you really legless!
Cast clearances will solve a lot of my warm up issues. Absolutely hate waiting for the forgies!
I do like this idea very much. I need to price it all firstly. Machining is gonna be the big killer, followed by ECU and TBs.
Vin Sharp says the Six Throttles calms the idle down with my cams too, because the profile means the vaccum from one port interferes with anothers, and makes light load driving a kangaroo-ing experience (it is bad below 2500).
He says with his 103.4mm Bore engine that if you stand on it the 225 Azenis spin from around 3k rpm in 2nd. i like the idea of that!
Cast clearances will solve a lot of my warm up issues. Absolutely hate waiting for the forgies!
I do like this idea very much. I need to price it all firstly. Machining is gonna be the big killer, followed by ECU and TBs.
Vin Sharp says the Six Throttles calms the idle down with my cams too, because the profile means the vaccum from one port interferes with anothers, and makes light load driving a kangaroo-ing experience (it is bad below 2500).
He says with his 103.4mm Bore engine that if you stand on it the 225 Azenis spin from around 3k rpm in 2nd. i like the idea of that!
Fixing it bit by bit....
Jooolszz,Go Haltech or similar and run on tps mode...forget vacuum sensing..Haltech also have zero throttle maps ..You will get the wildest cam to purr along nicely...
I take it Vince has built a coulpe of these 103mm jobbies??He has noe problems with sealing here then??
I take it Vince has built a coulpe of these 103mm jobbies??He has noe problems with sealing here then??
French cars are shit and shit expensive to service and bloody awful and unreliable and expensive and friends don't let friends drive french cars and you wait years for parts.
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SydneyJules
- Verde
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- Joined: Sun Dec 19, 2004 1:57 pm
- Location: Sydney
He's built a few of them from what I hear.
He says his is still going, 12 years later, with a one off billet six throttle slide injection setup he made for it.
And yeah, he said for $4k AUD he would bore the block out and fit the liners... which I thought was pretty reasonable considering Beninca wants 3K AUD for a TS Monoblock insert.
Im guessing they are eithe Volvo or Cummins liners or somthing, which are machined down in height to fit....
The other thing I said, was I heard he had built a customer one that blew headgaskets all the time.... perhaps the Comp was a bit high with that one? I dont know the truth on that, though....
The ECU will def. be a Haltech I reckon, as Ive already got all the sensors to run one.... ie. My old F6 is still doing its job... fuck its a crude little box!
He says his is still going, 12 years later, with a one off billet six throttle slide injection setup he made for it.
And yeah, he said for $4k AUD he would bore the block out and fit the liners... which I thought was pretty reasonable considering Beninca wants 3K AUD for a TS Monoblock insert.
Im guessing they are eithe Volvo or Cummins liners or somthing, which are machined down in height to fit....
The other thing I said, was I heard he had built a customer one that blew headgaskets all the time.... perhaps the Comp was a bit high with that one? I dont know the truth on that, though....
The ECU will def. be a Haltech I reckon, as Ive already got all the sensors to run one.... ie. My old F6 is still doing its job... fuck its a crude little box!
Fixing it bit by bit....