ALFAGTV6.COM

Post by **Zamani** » Wed Aug 10, 2005 9:07 pm

Dear All,

Any info on what can be done here? I'm getting ~180 wbhp @ 5700 rpm with 24* BTDC ignition advance (max) with stock heads, stock SZ manifolds and paper air filter.

I'm looking for another 10 wbhp from "stage 1" head work. What I mean by stage 1 is, lighter and slightly bigger valves and very mild porting. Is it possible?? And maybe cut the exhaust valve guides to blend into the port, but this could make the valve wiggle more (due to rocker design) and cause excessive wear.

OK let the discussion begin!

And maybe another 10 wbhp from super custom headers he (I just bought a lincoln mig welder hehehe )

Mats · Post by **Mats** » Thu Feb 02, 2006 4:55 am

Old thread but interesting...

I'm about to do a small job on a 2.5 (12v) and it would be nice to have some background info. Anyone have cut up a head?
What can be done about those ports? The shape of them looks strange...

jrreeve · Post by **jrreeve** » Thu Feb 02, 2006 8:21 am

I'm sure its all dealt with in JimG's new book....maybe he can give us an excerpt or two...

Since, i'll be rebuilding a 164L motor for my GTV6 i'll be interested in this as well.

Rob

Mats · Post by **Mats** » Thu Feb 02, 2006 8:55 am

I want to find out what's been done, and when the book comes out it will be a little late...

TS_turbo · Post by **TS_turbo** » Thu Feb 02, 2006 10:25 am

some J. Greek quotes

....The problem with the 3liter are the intake runners, limiting flow to ~85cfm with the std valves. If you enlarge these runners to an ID of~39mm (from std 34mm) you will gain ~8cfm per cylinder or ~20hp total!! On top of this, if you reshape the intake valves giving them a flatter back, you will gain another 4cfm/cyl or ~9hp more! A total gain of ~29hp is no laughing matter. If you go through the expense of special profile large valves+larger valve seats+huge aftermarket runners+good head porting, you will spend a LOT of $$ for ~120cfm, worthy of a good race 3liter. Such a motor will go to more than 250hp with streetable cams.
All in all, larger valves are a waste of money in this V6, if all you want is a 20-30hp increase. A good porting job, reprofiled valves, enlarged std runners, higher CR, Motronic (S)cams and a set of CSC headers will get you much more.
Jim K.
....2.5 and 3.o 12v fwd engines all have the same cast alloy runners.
164 12v engines have 2 different chrome sizes, one with 36mm ID and one larger one (??mm). 24v engines also have 2 sizes, 36mm and 45mm in the Q4 and Quadrifoglio.
Reply With Quote
.....For your info, I plugged some airflow values in an engine simulation program and you can get ~12hp increase in a fairly stock motor just by changing intake flow by 18%, a fair and entirely realistic value with bigger runners. The increase starts at 4000rpm with NO detriment below that rpm (no loss).....

TS_turbo · Post by **TS_turbo** » Thu Feb 02, 2006 12:02 pm

the only thing that i cant understand is why flater back of valve give better flow

... for nord engine Jim advice for 46mm concave valve which is oposite to flat back ...hmm

shures · Post by **shures** » Thu Feb 02, 2006 6:28 pm

I know you guys are trying to find out what can be done and I am not trying to hijack your thread. However, at one time Sperry Valve Works in the US was the place to go for 4 cyl head work and was also reputed to be good with the V6. Assuming they did a lot of heads and have a flow bench they should know, right? Can anyone glean anything from their web site? Or has anyone had any experience with their V-6 heads? How about Rich Goodrich or any of the other vendors linked on from this site? Pat Braden always warned not to tackle the heads without a flow bench. He claimed Alfa did a fairly good job from the factory and that it was easier to reduce performance than increase it unless you had experience on your side....

Jose I · Post by **Jose I** » Fri Feb 03, 2006 3:28 pm

I don't understand what he means by flatter back valve ,is he saying that if I modify my vales to look like the one on the right it will flow better.
I would realt like to know I'm inthe middle of porting & polishing my heads (50mm runners)

Mats · Post by **Mats** » Sat Feb 04, 2006 1:37 am

I would not reprofile, I would buy new. VERY difficult to get them the same shape I think, easy enough to destroy them too.

So, no info on the 2.5?

Jim K · Post by **Jim K** » Sat Feb 04, 2006 9:56 am

You KNOW it must be the same shape as the 3liter!The ports are the same shape, same offset. Size is a different issue.
Hose1: 50mm runners is TOO big!
TS Turbo: you can have a flat-back AND concave (face) at the same time.
Jim K.

Post by **Zamani** » Sat Feb 04, 2006 11:26 am

Arghhhh!!! 50mm is too big?! You should have told me that earlier.

JoseI,

Where did you get your runners from?

Jose I · Post by **Jose I** » Sat Feb 04, 2006 11:39 am

Here's a pic you guys have seen them before they are 50mm
on top then taper down to 45mm

Post by **Zamani** » Sat Feb 04, 2006 11:45 am

I should get mine next week. Well whatever, I'm just going to throw it in there. And did you get the plenum too? I'm getting the whole set. But it's the stock plenum with modified stubs to fit the 50mm runners.

Jose I · Post by **Jose I** » Sat Feb 04, 2006 12:24 pm

the runners won't fit without the plenum

Jim K · Post by **Jim K** » Sat Feb 04, 2006 12:58 pm

Zamani, them pair of pants come only in two sizes right now, too small and huge. Ideally you'd want the ~50mm on top, ending at ~38mm at the bottom. You should see what serious engine simulation programs have to say about it! I'm sorry I was too late with this.
Jim K.

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