Bryce-o-rama
True Classic
Are those made of Glastic/Haysite?Proceeding to test fit the DCNVH Webers to vintage Abarth intake, with custom made spacers.
View attachment 43577
Are those made of Glastic/Haysite?Proceeding to test fit the DCNVH Webers to vintage Abarth intake, with custom made spacers.
View attachment 43577
Not sure, really. Any advice?
EDIT- looked back at my build spreadsheets. Estimate shaving .75mm from piston dome yielding .65mm pop up.
Thank you Steve and Ulix.but that was when you had an estimated combustion chamber volume of 31.5cc.... now you have the head "in hand" and measure it at 27cc it changes this a little... add to this the fact that skimming the piston crown will also reduce the measured flycut volume.
If your tame machinist has a piston roll over vice then enlarging the inlet flycut (2 on the left and 2 on the right side) of the KS pistons isn't a difficult job and will add some volume back.
Still aim for that SQ value of 1mm to 1.2mm max, so you need to choose a head gasket and determine what it's compressed thickness is likely to be and base the CH you want to achieve on falling into that SQ measurement window.
Al was well known for over estimating the valve open duration of the cams he sold, a bigger number looks more impressive and will probably sell more... so if you choose the faza 40/80 as the cam you'll use, it would pay to actually measure the valve open duration at running clearance (I guarantee it will be less than 300 degrees) and then you can easily determine your simple dynamic compression ratio... I think Ulix had a spread sheet where someone in germany had actually measured this particular cam grind.
SteveC
Is the prisma block M12 fasteners?Meanwhile, ordered a multi-layer steel head gasket.
https://www.midwest-bayless.com/Fia...ayer-steel-fiat-bertone-x19-128-yugo-new.aspx
Thank you Steve appreciate your high value input. Yes, M12 fasteners on the Prisma block. I will inform machinist on guidance.Is the prisma block M12 fasteners?
Not sure why but the listing doesn't recommend using this gasket with m10 bolts, possibly not enough clamping force available at 61ft/lb with an M10 bolt to get a good seal? I guess you could always go the ARP stud route
One thing not mentioned in the listing is surface finish, generally MLS gaskets require a much finer finish on the block / head faces (a much finer Ra number - your machinist will understand that) to ensure a seal ... the standard Fiat finish on the block is not smooth enough for an MLS gasket.
If you do use the MLS gasket you don't need to worry about working out the compressed thickness, as they don't compress, so at 1.3mm thick your going to be aiming for 0.3mm of plus deck (piston protrusion past the deck face) to get 1.0mm SQ value.
with the euro cam I would be aiming for around 10.5:1
trouble is at the moment with 86.4 bore / 67.4 stroke / 27cc comb chamber/ 1.3 gasket (7.9cc) / 2.cc valve flycut after skimming 1.2mm of the crown - (a guess)/ 33.7 piston CH (so 0.3mm pop up after the block has been decked 0.1mm to get it smooth) which is minus 1.8cc... is that my rough calcs put you at 11.4:1
you need add approx 2.5cc in the combustion chamber to get down to 10.5:1 with your current configuration...
SteveC
Compression ratio is spot on, but aren't you giving up 100cc's displacement?Update: we are going to forego the 67.3mm / 1600 crank. Combustion chambers are so small it is going to be perfect with the stock 1500 crank = 10.5:1 C/R. I will save the crank for my next X motor buildout.
I am. Also giving up the marginal advantage of the lighter 1600 crank. That said the setup should make a lot of power relative to the lightness of the car and flexibility of the frame. Big valve head, euro cam, header, Alquati intake w/ twin 36 dcnf.Compression ratio is spot on, but aren't you giving up 100cc's displacement?
Why not just come up with different pistons to get the ratio up, and keep the other benefits of the 1600?I am. Also giving up the marginal advantage of the lighter 1600 crank. That said the setup should make a lot of power relative to the lightness of the car and flexibility of the frame. Big valve head, euro cam, header, Alquati intake w/ twin 36 dcnf.
You and Ulix are both on point. Explanation: the Kolbenschmitt pistons are quite high quality and rare. No need to re-bore with this set. I happen to have another set of pistons but with same compression height, so that wouldn't have helped. The head is from Europe and fully configured ready to go so to either / or / both change pistons and modify the head wasn't really worth the extra 100cc. Besides, I can save the crank for the next iteration of my X engine. Or, use it in the 1300 coming out of the 128. Fiats are like Legos!Why not just come up with different pistons to get the ratio up, and keep the other benefits of the 1600?