All,
Planning what to have done to my Pinto head, and I'm stuck with the valves (no pun!), wether to enlarge or not. I will be running GSXR 600 TBs
which have a bore of ~38mm, so am struggling to figure out whether I have anything to gain by enlarging the std valves 42.1mm inlet & 36.2mm
exhaust? or do I just need to enlarge the exhaust valve?.
I am starting to think a good port and polish, 3-phase valve seats and new guides & bearings will get me as far as I will go with these throttle
bodies?
Any advise welcome (other than fit a Zetec, put a bike engine in etc )
Greg
What amount of power are you trying to get from your engine ? .i used bike carbs, planned the head by 1mm ported & polished and have a 285 piper
cam this gives me 175-180bhp -140 at the wheels
+rebore by 60th
Jacko
jacko - if I get above 150 at the fly I will be happy, so reading into what you are saying I don't need to enlarge the valves? (I am also
planning on a 285 cam)
Greg
Not a good idea to polish some Pinto ports IIRC
quote:
Originally posted by rusty nuts
Not a good idea to polish some Pinto ports IIRC
All you need is a smooth port surface, not polished . Polishing actually reduces power on a Pinto
quote:
Originally posted by rusty nuts
All you need is a smooth port surface, not polished . Polishing actually reduces power on a Pinto
If you want to split hairs - you want a mirror polish on the exhaust ports and a smooth but not polished surface on the inlet ports.
Once the ports have been enlarged and roughly smoothed any gains from further polishing will be minimal.
It's not neessarily the size of the valves that need changing, I know almost nill about the Pinto engine but in general the valve seat shape and
the area immediately in front of and behind the valve seat will have a far greater effect on power than polishing.
Get a copy of David Vizzard's book about the A series, it's not the same engine but he does demonstrate exactly what does and doesn't
work in there and you can relate what he shows to any engine.
quote:
Originally posted by andyharding
If you want to split hairs - you want a mirror polish on the exhaust ports and a smooth but not polished surface on the inlet ports.
Once the ports have been enlarged and roughly smoothed any gains from further polishing will be minimal.
thanks for the responses guys - the info I am really after I guess is how a 42mm valve (assuming the port shape is optimised) flows compared to the straight tube that is a 38mm throttle body?
quote:
Originally posted by gregs
thanks for the responses guys - the info I am really after I guess is how a 42mm valve (assuming the port shape is optimised) flows compared to the straight tube that is a 38mm throttle body?