Back pressure - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

Blue Baron · 02-23-2005, 01:23

Greetings. In discussions with other people who are far more knowledgeable about mechanics than I, I've heard conflicting reports about the need for backpressure on the old Ford big blocks. I have an FE390 in my Galaxie now. I've read and heard that you don't want to eliminate the necessary backpressure from these motors. Then, in conversation, I've heard people tell me that's complete BS . . . so gentlemen . . . what's the bottom line?

ford4v429 · 02-23-2005, 16:37

in my opinion, I really think the camshaft profile might affect what works best, make/type of motor shouldnt mean much at all. if you get some time, look thru here:

http://www.theoldone.com/archive/

theres a lot of hitech info in here about what works and why- dunno who 'the old one' is, but wish he'd publish a book on the things his company has found/developed...theres a cool thread in there on the boss429 they did for Bob Glidden that put ford on top of prostock for years- threads on bore/stroke/rodlength theory(and some data to back it up), porting, timing, combution chamber shaping...a wealth of knowledge all in little tidbits hidden in these archives- well worth reading thru.

Blue Baron · 02-23-2005, 23:42

There is a lot of info there, thanks for the link. Most of the info there seems to be for modern motors though. I'm sure most of the theory is close to the same. I didn't really see anything addressing backpressure specifcally . . . so I'll keep the floor open. :)

390wagon · 02-24-2005, 16:39

I think the only way to really harm a motor in the backpressure sense is to run the motor with no manifolds or headers, just straight out of the heads, sounds cool though

. the only car i've experienced that really needs back pressure is a honda 4 banger, with an open header that little crx fell flat on its face, hook the exhaust back up(factory cat and fart pipe) and it would wind right up and go like hell(for a honda at least). i think newer cars are designed for more back pressure because they come with cats but the old iron never had to worry about that.