ALFAGTV6.COM

[mjr]

So I have been given a healthy 2.5 stock engine from a broken up gtv. I have a spare £2000 to spend, and am thinking of lightly tinkering with this engine, even though theres nothing wrong with my engine in my car. Im looking at mild porting and polishing of the top ends plus headers, and installing a set of the fast road cams that EB spares in the Uk sell. Anyone have any experience with these cams??. How do they compare to the S cams? Im told they give very good results without making for a real lumpy idle. Im thinking I can increase Hp to about 180 with these minor modifications for this kind of money. Not particularly big or fast, but a nice little increase for a small budget, and keeps that sweet 2.5 where it should be, under the hood, instead of swapped for a 3litre. Just like to be a bit different

[rz]

just buy gregs supercharger kit.
the only way to become happy without paying skyhigh prices.
cams are expensive but the result in hp is really not enough,next upgrade...you will never be satisfied.
with gregs kit, you'll have so much torque that you'll be happy

[mjr]

yeah, already doing that with a magnuson mp62 on my stock engine, my point was, I know I could do that, but Im more interested in playing with the spare engine with some minor mods to get a modest 20-25 horse power upgrade if possible, then drop it straight into a donor car for nipping around town in. Just interested to see what simple mods I can make to a stock 2.5, without the use of forced induction, but I dont know anyone that has used the fast road cams. They are £300 sterling for a set, I dont think thats expensive.

[MD]

rz has your answer.

This is not simply a plug for Greg. Never met the guy. However his strattegy is correct and his product delivers the job. A much more cost effective power upgrade than what you are proposing.

[SydneyJules]

Or you could go to the other side of the forced induction world and stuff around with a Single or Twin Turbo setup. With a 9:1 comp ratio stock, you could jam around 15psi down the throat of a stock 2.5 with reasonable fuel. Dont go too far, though!

But then most of your budget is destroyed by the need for programmable management.

The naturally aspirated route? Comp ratio to 11:1 straight away, and get the heads ported, make up some sort of budget 6 throttle setup using motorbike TBs. S cams, and wow would be a nice little engine for the road- but that doesnt include labour costs... so...

Do greg's SC kit!

[mjr]

As I said, Im not interested in the supercharger Kit. This is purely and experimental exercise with a spare engine to see what kind of results some light head work and a set of fast road cams will do. A similar set up to the chapparal GTV6 set up from the early nineties. I believe compression rate was altered, some light head work, and a set of mild cams produced a claimed 195bhp with reliability, from the stock 2.5, using the standard Ljet system. Sounds a bit high to me, but, Unfortunately chapparal have long since gone, and there doesnt seem to be much in the way of detail as to what exactly was done with the 2.5. All I remember was, that the bottom end and pistons were not touched, and no turbos or chargers were used.

Apart from the carbs, its sounds like a similar set up you mention sydneyJules?? not sure. Anyone else know anything abojut the Chapparal set up?

[Greg Gordon]

Getting 195-205 hp out of a normally aspirated 2.5 is not a problem. Autodelta (the REAL Autodelta not the current outfit that's unrelated except in name) published part by part instructions on just how to do it. I used to have those instructions on my website but I took them off as nobody seemed to build engines to those specs anyway.
The overall idea was bigger valves with some minor headwork, headers, cams, 10.5:1 compression, bigger injectors and ECU with a higher rev limiter (BMW M535i).

[Barry]

As I said, I'm not interested in the supercharger Kit. This is purely and experimental exercise with a spare engine to see what kind of results some light head work and a set of fast road cams will do. A similar set up to the chaparral GTV6 set up from the early nineties. I believe compression rate was altered, some light head work, and a set of mild cams produced a claimed 195bhp with reliability, from the stock 2.5, using the standard Ljet system. Sounds a bit high to me, but, Unfortunately chapparal have long since gone, and there doesn't seem to be much in the way of detail as to what exactly was done with the 2.5. All I remember was, that the bottom end and pistons were not touched, and no turbos or chargers were used.

Apart from the carbs, its sounds like a similar set up you mention sydneyJules?? not sure. Anyone else know anything about the Chapparal set up?

I still have the full Chapparal write up that Fast Car did many years ago..
I do remember distinctly that they would NOT divulge the cam spec,neither the porting procedure they followed..
It did make a difference though.They did good work on the GTV6..

Correct porting of the little 2.5 heads make a big difference to flow...Using a mildish cam like the cams we used on the Group 1 race Alfa`s here,you would have a nice little screamer...Id definitely change 30 year old conrods though..

[mjr]

Thats the definately the kind of route Im looking at, Im not so sure that the head work and cams do work out sky high, prices wise, if you are fitting it at all back together yourself, and time is not an issue. I didnt realise that autodelta had done that, thats useful to know. Do you still have those instructions? Chapparal wise, I think they used quite an agreesive cam set up, as I do recal that many of the original chapparal cars, had the cams reverted back for every day use, otherwise they were very tetchy and user unfriendly. Fast road claim to yield the same results as agreesive cams, without turning the 2.5 into a lumpy tractorat idle. A chapparal car recently sold in the uk for $1500 ($2200) I believe, very cheap, though I have been told once or twice that the chapparal cars used to fall apart within a few years, suffering from build quality issues. So what is the "correct" porting on the 2.5 heads?


thanks all for advise.

[mjr]

sorry if this has been covered before, I couldnt seem to find much in a search, but staying with the porting and polishing of the heads, are the 3litre 12v runners and intake plenum of a larger diameter than those on the 2.5 or are they the same? ie any advantage to fitting the 3 litre runners and plenum, over porting those on the 2.5? do sperry valve works still trade? they used to sell ported runners and plenum for the 2.5 that bolted straight on.

thanks

[zambon]

I dont think that the runners or plenum are different on 2.5 and 3l engines. That is, unless you switch to 3l runners from the 164 12v. I think those might be slightly larger. That swap would require the 164 injectors as well, and the motronic ecu. I dont know what (if any) gains could be made with this swap, but it would be serious work.
Another thing to consider if you are interested in labor intensive but inexpensive upgrades would be a megasquirt programable ECU. Or you could pay a bit more for a system like GoTech and save some work. Combined with porting, cams, and exhaust you should be able to make something really nice.
BTW, The porting is a very good idea. People talk about it in vague terms all the time, "I have had light porting done." I have seen a 2.5 head that was cut in half to reveal the extent of how rough these ports are in stock form. The castings were not smooth to start with, there are ridges present (not the best description). These ridges had some rough touch ups done to try to smooth them out, but it appeared to me that the worker who did it was in a very big hurry. This is what people refer to when they talk about cleaning up the heads. They go in and finish what the guy in the factory should have done with more care.

[Greg Gordon]

I strongly suggest anyone considering porting thier heads wait until Jim's book is out.

[Raymonds 75]

Here's a short list of what autodelta needed to get 195-200hp from a 2.5...... with an after market ECU sytem you would get even more...[/img]

[Raymonds 75]

take 2...

Here's a short list of what autodelta needed to get 195-200hp from a 2.5...... with an after market ECU sytem you would get even more