lazylobster
Established member
I'm no expert (clearly) in the dark arts of engine CR. Whats the pro's and con's of having a higher CR?
R
R
It sounds like you can't take anything for granted with this build. I'm trying to get my head round the Catch-22 you must have when you're trying to get the height of the barrels just in that sweet-spot.:bang:
I'm no expert (clearly) in the dark arts of engine CR. Whats the pro's and con's of having a higher CR?
R
A most excellent thread, and great read...….
Just to pick up on something due to my unfamiliarity of Fiat components...
Am I right in saying that the head you are using is from a fiat Panda and is of a twin port inlet chamber affair and it fits directly onto a 500/650cc set up?
Rob
Hi Rob, You are correct in stating that the Panda 30 head will fit onto a 650 engine. The Panda 30 did indeed run a 650cc twin cylinder, but it delivered it's '30' bhp at 5500rpm rather that the precursor 126/2 engine of the same capacity, that gave 24bhp @ 4000rpm. I am uncertain if the head will fit a 500cc layout and to tell the truth why would you want to??? If Fiat went for the larger capacity with this head maybe they accepted that it was an advance to the basic engine configuration before the engine was finally killed off.
Ian.
Morning Ian....
Great info as usual, looks like I need to be precuring myself one of these heads then for a potential little project I have in mind...…..
If you have or know of any for sale...…
Hi Rob,
I'm afraid I don't know of any for sale, it would be a case of searching around - the demand would be high and prices too.
I would council you to take care with obtaining one as there are a few things one should be aware of - These heads are known to suffer cracking between the valves in the head pocket even with the standard size valves of 34mm inlet and 28mm exhaust. The repair of a crack is known to add strength to the area. The head does lend itself to porting and polishing of both the inlet and exhaust tracts to improve the breathing and even with two head studs protruding into the inlet I am told that the turbulence caused would not upset mixture flow to any great extent. Always check that the threaded areas for the exhaust and inlet manifolds are good, even if helicoiled. The rocker rail studs required the same caution as do the spark plug threads. Depending on the year of manufacture you will find that early heads (as with my 1983 head) only have a valve stem seal on the inlet valve. Whereas the later head (as with my 1985 head) have seals on both inlet and exhaust valve. These should be replaced if you cannot be sure of their age. You must establish if the head has been skimmed or not and by how much. If in doubt measure the capacity in cc . The main reason for this is that the capacity of the head directly affects the final compression ratio and if the squish area is good or not. My two heads are both skimmed to give different final compression ratio's, but it's still a faff to arrive at your planned figure. The pushrod tubes are also a pain, it's best to change them for VW items. Finally you may find that the external shape of the head has been cut away to facilitate the correct tight fit of a fan housing of one type or another (mine have) don't be put off by this as it has probably been done for good cooling. If you have any questions let me know.
Ian.
I will be fitting a 'Panda30' head onto my 'currently in-build' 695 engine, but instead of fitting the ubiquitous Weber DCOE/Dellorto/Solex twin side-draught carb I am taking a leaf out of the VW tuning book and fitting a Weber 34 ICH single downdraught carb---the same sort they fit to the early 1200/1600 VWs (1 per side). I am led to believe that the jury is still out regarding the benefit of the Panda30 head vis-a-vie the standard head---the ports are a bit too close to each other. Look at the 'after-market' twin-port heads and the inlet ports are definitely further apart, which will give a better 'flow'