ALFAGTV6.COM

[Maurizio]

I suppose your next post will be about the 'correct' 'π' and not just 3.14?
Jim K.

no, I don't want to disturb your sleep anymore....
At least your building something and not just crunching theoretical numbers

[Jim K]

The numbers always come before the build, like designing a cam, figuring port sizes, intake and exhaust manifolds... The actual building is the easy part! It would be nice if we could easily realize different configurations for testing, something more tangible than simulators! We would then spend days in the dyno room, blowing things up -the only true way to find actual limits, heheh! Like, what is the ultimate 3.2liter rpm? Hmmmm! Anyone claim to have the TRUE answer
Really, my Superflow guy has an engine dyno he hasn't installed yet as he's looking for a remote shop where noise won't bother neighbors or rattle buildings. He's very eager to do just this: explore engine limits and he wants to start with our (my) 24v...
Jim K.

[Maurizio]

"The ultimate wet dream", really test where the limits are, with destructive testing!


I work at and for firms who have serious r&d budgets and even here, this is still a wet dream
Though we break enough stuff also

[Jim K]

I must say... of course I'd be interested to witness some engine destructive testing -from a safe distance- as long as its someone else's engine!
Jim K.

[Mats]

Like this?

http://youtu.be/j973645y5AA

[Jim K]

Oh yes, great clip Mats!
Jim K.

[Jim K]

Having a spare 24v engine, I decided to work on its heads and port them a little different than the first set for the 3.2. This time I opened up the bowl area between guide and seat a bit more and leveled out completely the intake guide mound -the intake guides still project in the port though. After size-matching and polishing, I roughened the intake ports and polished the exhaust ones well. In general, the exhaust ports are diverging from the seat out. Again, std size valves are used but the seat ID was opened up to 32mm for the 35.6mm valves. The purpose for this exercise is to compare the two very differently ported heads on the flowbench.
Some pics of this work below.
Jim K.

[Maurizio]

Cool!
Is there/do you have a way to measure swirl?

[Jim K]

I will ask when I go there. I don't even know if he has velocity probe/mode.
Jim k.

[maxiboy]

So looking forward to some more data re the heads

thanks Jim

[Jim K]

Don't expect anything radical, porting is within 1-2mm from std dimensions. It can be taken a lot further but 9krpm is not in the plan!
Jim K.

[Jim K]

Moving slowly but surely along the 3.2 path, I have completed all preliminary work on two sets of heads. I have named them B and C, following the A heads in my car. I am waiting for the exhaust guides to come in and when I have all the guides for the C heads, I will reshape them on a lathe. After installation and seat refacing, its flowbench time! I expect the C heads to show the best flow, followed by the B heads. Graphs will be posted when available. The time is near to measure CR and determine amount to shave off for ~11.5:1.
I decided to keep time for once and I finally have some labor data for the above work. From start to finish, one head is ~11hrs of work -for me. Start with removing valves, wire brush gross cleaning, knock out guides, porting, repeated caliper measurements, manifold matching, thorough cleaning, cam fitting/relieving for free rotation, follower oil hole elongation, last cleaning cycle, insert guides. The guides take another ~1hr for cutting and shaping. If you have never ported heads or you don't have the proper tools, you're looking at much longer times. So for two finished heads it takes me ~23hrs of concentrated work. Then there's the machine shop work: valves/seats/milling. Other costs involve a supply of various grades rotary bits and several quarts of paint thinner. My next post will be more interesting, comparing 3 head versions all with std size valves.
Jim K.

[kevin]

Huge amount of work there ! Did you check the comp ratio on the standard heads as we found on the old gta 156 race cars they were 0.2:1 less the manufactures claim . How much do you intend shaving off to get to your 11:5:1 or is the top secret at this stage .
What do you consider a reasonable ( max) compression ratio for a fast road and trackday car on the 24v motor .

[Jim K]

Max CR is a function of cam duration and available fuel. We can leave fuel out since we have very good 'premium unleaded' pump fuel -called 100octane gas here- so we are left with the cams. Here is where the simulator helps. We are looking for as good a dynamic CR as we can get and from that we can find our geometric CR, or we can work backwards by searching which geometric CR will give us a high DCR, but no more than ~9.5:1. This helps: http://www.wallaceracing.com/dynamic-cr.php
I would think 11.5-11.7:1 to be a practical CR for a trackday car.
Today I installed the guides in the second set of heads. I had to hammer a lot with the exhaust guides as they were ~0.01mm thicker than the last set (different manufacturer). As a result, they tightened when in place so tomorrow I'm taking the heads to the machine shop to use their 7mm reamer. The seats will also be cut at the same time.
Measuring CR and how much to mill off the heads: After the seats are cut and I lap the valves, I will install valves in cylinder #2 or #5. Old head gaskets will be used and the heads torqued down. With the respective piston at TDC, the engine stand will be tilted so that the gasket is horizontal... This you will have to see and laugh at, its a major undertaking given the type of stand I have! I have high compression pistons, so what I end up milling will probably be of no help to anyone. With my 10.3 cams, 112* lobe centers and 11.6:1 cr, dcr comes to 9.5:1 which is ok.
More news soon including valve/piston clearance measurement... Following that, both head versions will visit the flowbench...moment of truth!
Jim K.

[Jim K]

On the subject of valve seats, I have been drooling over a good cutter set for some time, able to cut modern catalytic ultra hard seats: http://www.ebay.co.uk/itm/Sealey-VS1825 ... 5aedb03950
You can see that it costs quite a bit and I can't justify it by building 2-3 heads/year. I do have a complete set for old-style seats exactly like this one: http://www.ebay.co.uk/itm/BGS-Tools-27- ... 589d65a846 but I can only use it for older 105 series Alfa heads -the cutters just skid on new type seats. Therefore, I hover over the machinist when he does the seats making sure they are cut as I want them. Only problem is these guys are busy and I can't just barge in there any time I feel like it!
Jim K.