3.0L Exhaust Manifolds

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Brian16
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3.0L Exhaust Manifolds

Post by Brian16 » Tue Nov 21, 2006 12:52 pm

Hi there,
First of all: Murray, X-Rad, Dennis, Barry and MD; Thank you all for the advise on removing the front pulley nut. I got it off using some implements you would'nt find in a Swiss Watch Makers toolbox: 41 mm socket, extension bar and onto that an old hollow go kart rear axle. I had the flywheel blocked with a crowbar between the three protruding bolts. Standing on the go Kart axle I wacked the extension bar and the nut turned. No sign of thread locker TG.
Thinking ahead for my ( Alfa 75 3.0L) engine reassembly, does anyone have any thoughts or good or bad experience regarding sport exhaust manifolds or exhaust headers as they are known in some parts. Any recommendations for any brands and where can I get hold of them or any I should avoid?? Are they worth the money??
// Brian.
La vita e troppo breve da non guidare un'Alfa
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Dennis
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Post by Dennis » Wed Nov 22, 2006 12:25 am

Good to hear you've got it off.

As for headers I would go for CSC. They're not the best money can buy but probably the best bang for buck. Plus extra ground clearance!! I have them on my own car and they are great!
'81 GTV6 3.0 QV
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patzo_3l
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Post by patzo_3l » Wed Nov 22, 2006 5:29 am

best bang for buck would be to leave the standard 3.0l exhaust. belivieve me i have tested a few and backed them up on the dyno and for the money your gona have to spend i wouldnt bother. simply leave it all standard bar a straight through rear muffler thats it. not saying its the be all and end all but unless u plan on maiking alot more power there are not many benefits to gain except less dollars in your wallet and an exhaust that sounds a little different. having said this if you could come across a a decent size short type of manifold for a good price then i would bother.other then that save ur hard earned. just my 2 cents.
patzo_3l

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Greg Gordon
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Post by Greg Gordon » Wed Nov 22, 2006 7:25 am

There are two problems with the 3.0 exhaust manifolds. First is they are very rare in the U.S. The only car that had them was the Verde. The second and far bigger problems is that A LOT of Verde manifolds are identical to the 2.5 manifolds except for the part number. So even if you track down and buy a pair of Verde manifolds unless you get lucky they will offer no improvement at all.
I don't know how many Verde manifolds actually had bigger inner diameters. The two sets I have here, one on a 87' and one on a 88' are exactly the same as all the 2.5 manifolds I have lying around.
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x-rad
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Post by x-rad » Wed Nov 22, 2006 5:03 pm

my set of 2.5's and my alleged set of 3.0's have the same inner diameters at the exhaust port...
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Fernando
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Post by Fernando » Thu Nov 23, 2006 6:07 am

On my own 3.0 litre, after I had a Glenwood Motors Group 1 conversion done,they put a Wildact manifold on.I cannot vouch for dyno power figures before,using the 2.5 manifolds,and after using the Wildcat system.It was specificaly developed for the GTV6 here in South Africa.

The manifold was designed to aid top end power from 4000 rpms onward. :D

I reckon Barry and Kevin would be able to provide you with even more detailed info and a possible pic as I no longer have them.They were not designed to work on a 3.5 litre motor. :D
"Racing is life,everything before and after is just waiting."- Steve Mqueen
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Post by patzo_3l » Thu Nov 23, 2006 7:20 am

the inlet and outlet are exactly the same diameter as the 2.5 manifolds. the bigger part is where the bends are they r nearly 2-3 mm bigger through those areas. i have dynoed back to back and gained 10 hp through the rev range and actually held power up high rpm for a little bit longer. as u say though if they are rare in the u.s then that is another problem, but if ur car already has them i would leave them on. if u truly do have 3.0l original manifolds on hand u will be able to measure for yourself and see that it is true. also the test i did was between a 2.5 manifold and a 3.0l manifold on a 3.0l engine.
patzo_3l

3l gtv6 turbo 85'
2006 147 gta selespeed
1990 75 twinspark
1998 spider
2.0l gtv 85'
33 1.7ie
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Post by Greg Gordon » Tue Nov 28, 2006 6:57 am

Thanks Patzo. I thought I checked the bore farther back, but it was a while ago. I have two set of 3.0 manifolds here and various set's of 2.5 so I will look later today when I get a chance.
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Zamani
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Post by Zamani » Tue Nov 28, 2006 2:56 pm

3.0 manifold has a slightly bigger bore. The difference is very slight, maybe in the 1-2mm range. But I've verified this myself.

BTW, Patzo who recommended the bigbore short headers?

Big bore and good primary length is almost impossible.
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