As persons who read this board are aware, I like to start newbie threads. Here is another one:
I am starting to think about my heads. I know very little about heads other than what I have read on Greg Gordon´s site (countless times). When heads are rebuilt, the machinist can remove material, potentially creating space for larger diameter valves and guides.
¿Correct so far?
I have looked on the normal sites that sell alfa bits and I have never seen big 3l valves offered. However, I seem to remember reading some place about a large valve conversion. Is a large valve conversion a good idea for a hot 3.0? Is it possible buy larger valves that are OE on somebody else´s car and install them in my machine? Does messing with valve size have any negative consequences other than changing economy?
I do not anticipate going through with this, but I would like to know and understand my options. Going through this car has been an educational experience which is exactly what I wanted from the beginning.
Thanks for the help
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junglejustice
- Verde
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- Location: Granolaville, WA
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MerrilGordon
- Gold
- Posts: 166
- Joined: Wed Dec 29, 2004 5:55 pm
- Location: Marysville, WA. USA
From what I've read, going to larger valves on the 3.0 12-valve may not be worth the trouble as this engine's ports are the same size as the 2.5L. I'd say the 3.0L heads would need to be ported first to justify larger valves. Then there is the extra weight of larger valves. That might stress other components in the valve train.
What about, if I've got the term right, swirl polishing ? I've seen it in Hot Rod magazine where the valve stem is reduced and the back side of the valve head is altered as well. I wonder if there's any worth to that ?
Merril
What about, if I've got the term right, swirl polishing ? I've seen it in Hot Rod magazine where the valve stem is reduced and the back side of the valve head is altered as well. I wonder if there's any worth to that ?
Merril
82 GTV6 3.0
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Que Boludo
- Gold
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- Joined: Sun Nov 28, 2004 9:02 pm
- Location: Australia Sydney
Sorry to say this but our engines are more related to hot rods then the newer hi-tech
Machinery, that why I love this engine it’s a engineering masterpiece.
I wouldn’t go putting bigger valves, just get a good port job, some nice cams and up the compression.
Machinery, that why I love this engine it’s a engineering masterpiece.
I wouldn’t go putting bigger valves, just get a good port job, some nice cams and up the compression.
I maka de list, you Justa geta the parts - OK! Wise words from the great master Toni Baloney – Ginger Fingers.
Hi Guys!
I'd also like to have some questions about the heads.
I have a stock 2.5. I don't want to change to 3.0 only would like to create some power increase by modifying the heads.
I will have a set of brand new 3.0 litre valves. But AFAIK, they are too large to simply fit them in the 2.5 litre head. Can they be machined to the largest possible diameter that the head can accomodate? What it that largest diam?
Of course it should go together with porting, polishing, and fabricating matching intake runners. And fitting S cams.
But this all only will be a case if my cams I've found are really S-cams. They have a number 3033 and 3031. Could somebody make me confirm they really are? Thanks to Seb I already got an answer, but I'am interested in others opinion as well. In another way, could somebody tell me how can I identify the cams whether they are 2.5, L or S ones?
Thank in advance!
I'd also like to have some questions about the heads.
I have a stock 2.5. I don't want to change to 3.0 only would like to create some power increase by modifying the heads.
I will have a set of brand new 3.0 litre valves. But AFAIK, they are too large to simply fit them in the 2.5 litre head. Can they be machined to the largest possible diameter that the head can accomodate? What it that largest diam?
Of course it should go together with porting, polishing, and fabricating matching intake runners. And fitting S cams.
But this all only will be a case if my cams I've found are really S-cams. They have a number 3033 and 3031. Could somebody make me confirm they really are? Thanks to Seb I already got an answer, but I'am interested in others opinion as well. In another way, could somebody tell me how can I identify the cams whether they are 2.5, L or S ones?
Thank in advance!
'The GTV': '83 GTV6; (summer)
' Mr Brown': '82 Alfetta 2000L; (family car)
'The Little Red': '79 Alfasud 1.3 Super; (under restoration)
' Mr Brown': '82 Alfetta 2000L; (family car)
'The Little Red': '79 Alfasud 1.3 Super; (under restoration)
As written above; porting, larger valves, larger intakes.
I'll get a set of 3.0 valves soon, and was thinking of taking them to the macine shop and make them machined to smaller diameter. But I don't know exactly, what is the largest, the 2.5 head can accomodate? ~42mm intake maybe?
That would the mods be together with the QV cams. What do you think, would that result an approx. 10hp power increase? Should I go that way?
I'll get a set of 3.0 valves soon, and was thinking of taking them to the macine shop and make them machined to smaller diameter. But I don't know exactly, what is the largest, the 2.5 head can accomodate? ~42mm intake maybe?
That would the mods be together with the QV cams. What do you think, would that result an approx. 10hp power increase? Should I go that way?
'The GTV': '83 GTV6; (summer)
' Mr Brown': '82 Alfetta 2000L; (family car)
'The Little Red': '79 Alfasud 1.3 Super; (under restoration)
' Mr Brown': '82 Alfetta 2000L; (family car)
'The Little Red': '79 Alfasud 1.3 Super; (under restoration)
How did you decide you need bigger valves? The 2,5liter has very good size valves, much larger proportionately than the 3liter. If you want something to improve, clean up the ports (not enlarge) increase compression ratio to the max compatible with the best commonly available fuel in your area (by shaving the heads), install the QV cams and a good free flow exhaust system, tailor the advance curve to what the engine wants and away you go. If all this proves too little for you, find a 3liter and do the same things. I don't know which solution is cheaper,but I strongly suggest you rebuild the engine and balance everything on your way to higher power-this way it will live longer and make more power!
Jim K.
Jim K.
Talking about larger valves, i remember something like porsche 911 valves on 3.0 v6 alfa engines, is this true?
I think that there is more to improve on a 3.0 liter because intake runners, plenum, exhaust, are the same as the 2.5 liter !!!
Intake runners have small diameter than the head intake, if you clean the ports you can have 2mm more diameter on the head than the stock runner, and the the holes in the plenum can be worked too, near 3mm more diameter.
Get rid of the AFM, and a good exhaust system.
JimGreek, i´m planing to put bigger intake runners, maybe 40mm is a good diameter for a 3.0? my head intake is about 38mm. (i think..)
I think that there is more to improve on a 3.0 liter because intake runners, plenum, exhaust, are the same as the 2.5 liter !!!
Intake runners have small diameter than the head intake, if you clean the ports you can have 2mm more diameter on the head than the stock runner, and the the holes in the plenum can be worked too, near 3mm more diameter.
Get rid of the AFM, and a good exhaust system.
JimGreek, i´m planing to put bigger intake runners, maybe 40mm is a good diameter for a 3.0? my head intake is about 38mm. (i think..)
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MerrilGordon
- Gold
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- Joined: Wed Dec 29, 2004 5:55 pm
- Location: Marysville, WA. USA
Yep Zambon, I read Hotrod. See, I trade my Autoweek publications with my brother for Hotrod and Cycleworld. They've had some very good detailed articles on many of the new engines. And there are other articles I just skip . . .
Regarding valve size, or the entire heads for that matter, I think one needs to keep in mind how good these 12v engines are compared to other designs like common OHV or even the old flathead engines. Greg Gordon touches on this a little on his website. The early Chevy small block was a real boat anchor of a design that flowed air quite poorly. And they were much better than the old Chevrolet "stovebolt" six that had multiple 90-degree air flow bends from the "hi-tech" one-barrel carb to the siamezed intake ports with a head bolt in the middle ! I've got a book on (early) Chrysler Hemi's and noticed experimental heads for the 426ci engine with even larger ports than stock didn't produce any more power. I believe the conclusion was that stock ports on those heads were huge to begin with.
So I guess my point is that this (fantastic) forum documents quite well what is most effective in increasing performance on these engines and larger valves isn't one of the leading items.
Merril
Regarding valve size, or the entire heads for that matter, I think one needs to keep in mind how good these 12v engines are compared to other designs like common OHV or even the old flathead engines. Greg Gordon touches on this a little on his website. The early Chevy small block was a real boat anchor of a design that flowed air quite poorly. And they were much better than the old Chevrolet "stovebolt" six that had multiple 90-degree air flow bends from the "hi-tech" one-barrel carb to the siamezed intake ports with a head bolt in the middle ! I've got a book on (early) Chrysler Hemi's and noticed experimental heads for the 426ci engine with even larger ports than stock didn't produce any more power. I believe the conclusion was that stock ports on those heads were huge to begin with.
So I guess my point is that this (fantastic) forum documents quite well what is most effective in increasing performance on these engines and larger valves isn't one of the leading items.
Merril
82 GTV6 3.0