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Alfaross69 · Post by **Alfaross69** » Fri Apr 15, 2005 3:41 am

Mats wrote:
Alfaross69 wrote:
JimGreek wrote:You've just begun to scratch the surface of hard work! Now you must equalize chamber volumes to the largest one by careful grinding. It may take anywhere up to 4 hours and countless repeated precision measurements! When that is done, you must make sure combustion volumes are equal, by bolting the head to the block with a used head gasket and cc'ing all cylinders in turn, with the pistons at TDC of course. If you have any discrepancies there, start crying, because rod lengths will be at fault. When that is also done, you must decide how much to mill off the head for the desired CR and then worry again about how close your valves are to the pistons!
Jim K.
Jim
Would you explain how with the head in place how to measure combustion volume your way.
With a burette. Seal the piston to liner with some grease, torque the head down and fill the combustion chamber through the spark plug hole using a burette, stop when you reach the bottom thread.

That's the combustion chamber volume.

Sorry I knew that ! But I had edited my post to read "cc'ing the cylinders" but your post and my edit passed each other in space. I assumed he meant cc'ing the combustion chambers with pistons at top dead centre when he wrote to cc' ing the cylinders. But it begs the next question.How will you determine swept cylinder volume when pop up pistons are used? which is what I MEANT to write,sorry for the confusion. I'm tired ,sorry or is this just bore(area of bore) x stroke formula for volume?

Mats · Post by **Mats** » Fri Apr 15, 2005 8:16 am

well, that is just depending on bore and stroke, so if the bores are all the same and the crank have the same stroke on all cylinders it's good.

Alfaross69 · Post by **Alfaross69** » Fri Apr 15, 2005 12:27 pm

Mats wrote:well, that is just depending on bore and stroke, so if the bores are all the same and the crank have the same stroke on all cylinders it's good.

mats ,
granted, but for purposes of knowing swept volume divided into combustion chamber volume to calc the CR ? just simple bore/ stroke calc for volume without regard to volume of piston pop up?

Mats · Post by **Mats** » Fri Apr 15, 2005 1:21 pm

well, the piston pops up just as much at bdc as tdc, right?

Jim K · Post by **Jim K** » Sat Apr 16, 2005 5:54 am

The simplest way I use to measure comb.chamber volume and hence CR, is by filling with 2-stroke oil from the plug hole at TDC (with both valves shut!!-I've also done it in overlap Mats, heheh!!) using a simple 60cc syringe with a thin transparent tube. Practice accurately reading the syringe to obtain near perfect results. The burette method allows you to grow a...fair size beard before you're done and this long interval promotes ring leaks. If you want to double check yourself, repeat measurement on another cylinder (I assume you have equalized chamber volumes?...).
Purists may scoff at this method, but it WORKS!!

Maurizio · Post by **Maurizio** » Mon Apr 25, 2005 10:31 am

Some progress...

New 155 piston not machined / Old 75 piston.

New piston design

Saluti,
Maurizio

Mats · Post by **Mats** » Mon Apr 25, 2005 11:21 pm

So that is a std 155 piston? It doesn't look like the top is ~3mm higher, but it might be the angle of the pic?

One thing I don't understand... If the rods are the same, the crank is 0.25mm offset, how can the piston be so much higher without hitting the head? With a narrower valve angle the head would be even closer to the piston.
Are the rods really the same? Different block?

That CAD rendering, is that the machined piston? Unigraphics?

Maurizio · Post by **Maurizio** » Tue Apr 26, 2005 12:21 am

Mats wrote:That CAD rendering, is that the machined piston? Unigraphics?

Yep, unigraphics of the machined piston.

I don't believe that the rods are the same, liners are. I'm at a customers site, so no AR parts disk available

But the 3 mm is really there. Even when you look from a side 3 mm does not seem much.

Mats · Post by **Mats** » Tue Apr 26, 2005 12:45 am

Interesting...
How much did the piston cost? Weight (complete) compared to 75 piston?

Maurizio · Post by **Maurizio** » Tue Apr 26, 2005 1:05 am

I borrowed the piston from the machine shop. A 155 being there for a rebuilt has some delay

Will get a qoute for the machined piston in a few days.
Weight I didn't check ...

Mats · Post by **Mats** » Tue Apr 26, 2005 3:14 am

What!?! You didn't weigh it when you had the chance??

Baaad Alfisti...

Maurizio · Post by **Maurizio** » Mon May 23, 2005 12:19 am

For my TS bottom end project, I'm making a list of new parts.
http://alfagtv6.com/bb/viewtopic.php?t= ... 30cf581183
is a nice list as guide.

I have three questions.
1) As I'm rebuilding a 4 cil no timing belt but a chain.
Do you guys replace the gear wheels of the timing chain also?
2) Head gaskets, what to use standard Reinz/Goetze or a better quality like from Spesso
3) Oil pump replace ? (I have checked the current pump, gears are fine, minimised axial play and optimised flow of the pickup tube

)

Saluti,
Maurizio

Ps machining the 155 piston was quoted E45,- (each).

Jim K · Post by **Jim K** » Mon May 23, 2005 6:45 am

If you really want cam timing accuracy, it is imperative to replace the crank and intermediate gears, as a new chain is not enough. Make sure you buy the shortest lower chain you can find

Don't assume they all have the same length, there are brands that just won't do

. I would go as far to advise replacement of the cam sprockets and top chain also as they wear a lot and the tensioner doesn't properly compensate for this type of wear (for the engineering types out there, the cam sprockets are gradually reduced in diameter also!)
All gaskets you mention are fine, provided you retorque 5-6 times to 10kgm. Make allowance for valve/piston clearance....not only at TDC

If oil pump axial clearance is ~0 and radial within spec, use it. Make sure the relief valve shuts properly (I lap it with fine valve paste) and don't use extra washers on the spring! They do nothing for hot oil pressure and can cause problems with a cold engine.
Jim K.

Maurizio · Post by **Maurizio** » Mon May 23, 2005 10:01 am

OK, thanx for info.

Make allowance for valve/piston clearance....not only at TDC Exclamation

Checked the valve clearance in the design again and have theoretically on intake 2.47 mm and exhaust 2,34 at TDC when taking the C&B race cam, with a 1.6 mm gasket thickness,

Cam Lift IN Cam Lift EX Valve Timing Valve lift TDC Clearance Part No.
11,4 11,4 45°- 75° / 72° - 42° 4 / 3,8 40 / 50 ARTS.114.300C

as reference, wasn't more I could take out of the piston, but I will start with the original cam, so for now there is clearance enough.

Will also check when assembling the engine to see what the real cleance is. So I know for sure what the max is, before I start shopping for cams. I will mail C&B for a for a complete lift diagram. But on the other hand there are probally more very nice cams available (HINT) only emmision rule is 0.5% CO at idle!
Which is only needed at the yearly check

for about 15 minutes.

Saluti,
Maurizio

kterkkila · Post by **kterkkila** » Sat Apr 22, 2006 10:50 am

Maurizio,

How much you took away from the 155 pistons and to what compression ratio you finally ended up?

I'm planning to build another engine with those 155 pistons. Not sure yet is using TS rods and shaving 155 pistons like you did, or trying to find 155 rods and milling the head radically to get up the compression ratio.