EPA and Federal Goverment mandates are always putting presssure on the US Auto makers to reduce emissions and stretch the fuel mileage. I have a friend that is getting in the mid 20's on a 500 HP Mod, and is very friendly. For me, I think I get about 15 but my A/F at cruisingRPM's is fairly low and the 65 lb injectors don't help (the .82 OD works aginst me, also the 370 rear keeps my RPM's upto around 1800 at 65 MPH). I know guys that run like a 17 to 1 AF at cruisingspeeds and get great mileage.My pushrod motors get from 6-7 to about 11-12 on the ones that make over 400 HP. As far as lasting, another friend turned over 500,000 on his 4.6 stang on the original engine and no rebuilds, and he beats the crap out of it every day (100 miles round trip to work).

 

i still hold my position that if fod had put more R&D into the 5.0 they would have 03-04 cobra performance easily with mpg better than 4.6. but like you said the LSx series is all in the flow of the head ford has never been known for great flowing heads....why? who the hell knows.

 

I've thought about this and I think I can offer a suggestion or two as to why Forddid not try to get (or perhaps couldn't get)mod motor performance out of the small blocks. As can be seen from this discussion (https://mustangforums.com/m_4066125/tm.htm), the 289 doesn't come close, even with high performance mods, to a bone stock 4.6L (281 ci) 01 Cobra motor. The Cobra motor makesover 50% more power than the stock A-code 289 (even without takinginto consideration gross vs. net HP conversions)and still quite a bit more than a highly modified 289. At the height of Ford's 5.0 run, the 93 Cobra only made about 260-270 HP at the flywheel (SAE estimated, Ford specs say 235, and that's with 21 more ci - 7.5%).

The main reason is obviously cylinder head design. Couldn't Ford just put these heads (or similar) on a small block and go? No. The reason is the geometry of the block. The mod blocks (4.6L) have a higher deck height than the small blocks, thus separating the heads farther apart. That makes it possible to design a head with a more directly aligned intake port. It also makes it possible to have better angles (and more flexibility in design) for the intake manifolds.

The other reason is that the mod motors have closed up the valley. In the small blocks, the intake manifold is the 'lid' for the lifter valley. This means two things. First, the intake manifold will have more engine heat transfered to it, both by physical contact and because coolant has to flow through it to get to the heads. This means that the fuel/air charge will be hotter. Cooler fuel/air charges mean you can run more timing andcompression before spark knock, and a cooler mixture is denser tomake more power. The 01 Cobra, 03-04 Mach 1run almost 10 to 1 compression and the 05-08 GT motors run over 10 to 1. A 4.6L DOHC motor cansafely run 11 to 1 on 93 octane gas (with a good tune). The 93 Cobra 5.0 ran 9 to 1.

Second, by opening up all that space the intake manifold design can be more flexible. The runner length can be tuned more easily and they can provide a smoother flow. All one has to do is look at a 5.0 EFI intake to see the contortions Ford had to go through to get long runners for low-end torque from a small block (and the flow-restrictingtight bends the runners make in the lower intake). With the mod motor, you have room for such exotic things as variable geometry intakes where you have a long runner for low end torque and a short runner for high RPM power (such as the FR500 or Aviator intake - pictured). They can also design the intake for smoother airflow in a smaller space for hood clearance.

Thus, the top-end of the engine is where all the power comes from and Ford probably could not do with the small block design what they did with the mod motors. (That, and the fact that they rev much higher due to the, actually, longer stroke with a longer rod and smaller piston, and overhead cams.) If you look at the LS motors you'll find the same thing (slightly wider head spacing, closed lifter valley, more exotic intakes).



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ozarks: Those were intelligent and informative posts, thanks. It's nice to see someone offer data to support an argument.

 

Thanks.

 

Did anyone see this? I found it in the street/strip section... looks like Ford is going in the direction of twin turbo v6.
Looks like a great motor that makes tons of power, but the Mustangs heritage is all about the v8...