Crustang to Mustang
Well-known member
What is the performance gain of bolting a crossflow head on a pre-crossflow block?
And adding to that, the 200ci alloy head2 in Xd-e was rated at 88kw net(118bhp), the earlier precross 200 would have had 85bhp if it was lucky. I drove the alloy head 200s when I worked for telecom Australia way back in the early 80s, they went about as good as a pre 250, and lower fuel usage. So the gain with the crossflow head is quite a bit. the 250 crossflow EFI was very close in power to the 302 Geelong V8!1980 AUS Fairmont Ghia 1 bbl Crossflow 4.1 liter, 126 hp net. 18.5 second quarter mile as an automatic. 108 mph top speed, 27 US Mpg at 62 mph.
1980 USA Granada Ghia 1bbl non Crossflow 4.1 liter, 99 hp net. 20.7 second quarter mile as an automatic. 95 mph top speed, 23 US mpg at 55 mph.
So 27 extra HP, 13 mph more top speed, more than 4 mpg better fuel consumption. From 1976 to October 1980, (the last year of the 103 HP net Iron non cross flow in Falcons and Fairmonts in Australia, until the introduction of the aluminum headed cross flow) , the city and highway fuel consumption dropped 20%.
Key concepts. When you get a 27% power boost and a similar fuel economy improvement, it's because not just the air flow of the whole engine combination is improved, it's combustion efficiency and reduced requirement to be always giving it death on the road. Those years, they used the same size 1.3 inch Venturi 1bbl carb, Carter or Bendix Technico, same 195 CFM flow. Same 256 intake duration cam with lift difference only be suse the Cross flow uses a 1.73 rocker instead of 1.5 ratio as on the Log head
The total over the log head intake CFM improvement at 400 thou valve lift was 125 CFM to 145 CFM, just 16% more peak flow, but at lower lifts which happen twice as much, the flow improvement were far greater.
This isn't a pro Cross flow rant. The same improvements can be made with similar flow efficiency improvements, either through better carburetion ( not discussed) or through head porting, rocker ratio or exhaust flow improvements.
Myself and a guy who called himself JD got involved with Jack Collins way back, i was still working and living in Perth, JD helped him a lot getting two engines to jack via sea frieght. He rang me a couple of times from Orlando. It all started off talking about 250-2v heads. Anyway the crossflow is a big gain over the old iron heads preX. And yes I have one or three.I just wanted to give Crustang to Mustang a real world opinion on a 250 Crossflow in a Mustang. The builder had a 9.5:1 compression ratio, 292 hydraulic cam, T-5 transmission, and 3.55 rear gears.