You can do anything with fixed table lookups if you have little Mass Air signal. Trust Steve. The old Motec and Haltech Hilborne EFi reworks had the same issues, so they just used fixed values.
The best option is Independent runner without the common plenumb.
The Hemi 6 guys have an alloy head and Weber to ITB throttle body adaptor for the 2.2 sq in intake runner head, and none of it lines up.
The D-series Hemi block designed in the US has a strange look of your modified 250 block. Here is a 6 cylinder Hemi 265 block in a Toyota Corolla KE30. Oh whata feeling!
Most of the Mopar 6 Pack Hemi 265 guys down here copy the Ford Cross flow and BMW Fuel Injection intakes anyway.
The horsepower will be well, well over 300 hp net with that Tighe cam and the compression you have. Ivan Tighe cut his teeth on Jag XJ-6 cams, so Dean Tighes cam details are about as good as you'll get anywhere.
Even with a 1.5 factor loss of an auto, you can make 300 hp with supreme ease.
Even the ancient long stroke 3442 Jag XK 140 with triple DCOE40's makes 190 hp at the bags, or 238 rwhp. The 250, its got way more cam, capacity and the canted valve head is a natural for horepower.
View: https://www.youtube.com/watch?v=INCs8jkOqCU
The E49 cam had 306 degrees at lash duration, and at 50 thou, 232/232 with 479peak lift on a 110 LSA, so its a low load stress, high duration, low lift cam. The Tighe cam is heaps more radical in lift and intensity, with a nice wide lobe center for Speed Density EFi.
Peak ignition timing can be raised, and the whole fuel delivery and spark tables can allow some impressive torque figures.
The exhaust becomes the fifth stroke with a normally aspirated six, and it produces a simply bitching improvement in sound.
Cam influence goes like this.
All the EFi engines got decompressed to 8.8:1 compression ratio, down 0.6 points from stock 9.35.
Stock, 1983-1984 149 hp net with 256 degree and 190 degrees at 50 thou.
The 1985-1992 X flow cam factory Cammed up with a 4.9 EFi style cam with 264 degrees and about 200 degrees lift at 50 thou, and you got 13 extra horspower right off - 161 to 162 hp net for 1985-1992 XF EFi
A stock 250 with EFi and 270 degree cam with 210 degrees at 50 thou makes 180 hpnet without upsetting the EECIV. This is without headers. With them, and a CAI, you get 212 hp
A stock 250 with EFi and 280 degree cam with 215 degrees at 50 thou makes 200 hp net without upsetting the EECIV. This is without headers. With them, and a CAI, you get 236 hp
Even a carb 1985 engine with a 9.35:1 compression 500cfm 2-bbl Holley 2305 carb, and some intake work and tubing headers and the 280 at lash, 215 degrees at 50 thou cam makes 196 hp, up 65 horsepower.
As soon as a proper cam goes in, its into the high 300 + net horsepower as the head flow goes up with proper Cleveland 351 style valve lift.
Uncorked, the stock head flow figures go way up. The factory paltry 145 cfm at 425 thou lift flow rate goes right up over 215 cfm with 525 thou valve lift and just a little port cleaning up. Most of the power gains are due to the stock 264 and 435 thou lift cam taking so much peak cfm off the head flow,
the rest is due to the already great port angles just loving some extra port area. So that de-dagging and grinding of the ports you had done will yield a huge increase in CFM with the 525 thou lift cam.
Headers at the exhaust then make a uniform 18% power boost if under hood heat is controlled.
Off topic, but important to note. Talking the later SOHC versions, they got a very good iron exhaust header which gave the same performance as a set of headers.
The stock SOHC Multiple Point EFI with much milder camsafdt specs, and 2:1 valve lift lifter ratios, by 1992, the stock level of 186 hp had grown to 216 hp.
The Mick Webb SVO 3.9 liter gained a set of very special Genie headers, and it was the only engine to benefit from them because he had designed the engine around them, with no clamied increase in power. The car took 1 second less over the 1/4 mile with headers verses those without. 186 hp -----> 216 hp, but he didn't do any engine remapping or cam upgrades at all.
A cammed up, modified X-fow 4.1 or SOHC 3.9 or 4.0 can turn up to 250 hp and 300 lb-ft any old time.
With the stalwart cam you have, it'll be well over all those numbers above.
The cam maketh the In line six, and two valve per cylinder inline sixes just need duration and cfm to make outragoeus power. Nothing under the valves is different to a good traditional in line six with the Triple Weber DCOE style 45 and bigger carbs
Namely:-
the stock factory E37/38/48/49 Charger and Pacer 265 Hemi Six Packs, 248-295 hp net proven.
Modifed, they have
heaps more suds than a DOHC engine
the XK-E 3.8 or 4.2 (aftermarket Triple DCOE's, 48 DCO's, or 48 DHLA's), always 300 hp net at least
the factory DB6/DBS 4.0 liter Aston Martin Vantage, 325 hp net proven, 340 hp + with 48 DCO Webers or 48 DHLA Dellorto's
All of these two valve per cylinder in line sixes engines were able to not just match, but obliterate the much bigger 318/340/360 and 326 V8's and V12 stablemates.
The best account is what the old triple carbed E49's did to 351 4V HO Clevelands is this
Factory, a 0-100 mph time of 14.1 seconds! It was only above 120 mph that the deficincies of a 3.5:1 axle ratio, 86 cubic inches and two less cylinders showed up. As stated, Leo Leonards 265 made 295 hp net at 5300 rpm , no modifications allowed, (302 gross claimed), and according to Mick Webb in 1988, the best 1971 351 4V HO engine with 505 thou lift cam and 300 degrees duration made 350 hp net on Fords dyno.
Modified, maybee 293.7 hp at the bags, with perhaps 370 hp at 6200 rpm on this 9" axled 4 speed BW Single Rail specimen. Despite the claimes, the 9" and 7-7/8" axles show the same drive train losses.
View: https://www.youtube.com/watch?v=BLnMgrF1-v8
