strange info request: exhaust port spacing on SBF head

[wicked93gs]

well, I had an idea that seems to be clever if it works....headers for the DOHC 4.6L are expensive...not that I mind paying the price...but I dont want to spend $500+ on a set of headers that I will be replacing when I eventually turbocharge it....on the other hand SBF headers are plentiful and cheap (as low as $150) which is fine for some temporary NA performance until I can do a twin turbo setup....of course they wont fit a 4.6L, but I can cut and weld assuming the port spacing is close enough to keep it minimal and just use a 4.6L flange, I know cheap headers dont last forever, but its worth messing with...anything has to flow better than the stock manifolds(which I dont have anyway)

 

[jlangholzj]

well, I had an idea that seems to be clever if it works....headers for the DOHC 4.6L are expensive...not that I mind paying the price...but I dont want to spend $500+ on a set of headers that I will be replacing when I eventually turbocharge it....on the other hand SBF headers are plentiful and cheap (as low as $150) which is fine for some temporary NA performance until I can do a twin turbo setup....of course they wont fit a 4.6L, but I can cut and weld assuming the port spacing is close enough to keep it minimal and just use a 4.6L flange, I know cheap headers dont last forever, but its worth messing with...anything has to flow better than the stock manifolds(which I dont have anyway)

if someone doesn't beat me to it, I'll give you some measurements. I've got my headers off now (cause i need new ones to fit the AOD) and I'll do some measurements.

port width, and inside to inside along with total length.

 

[wicked93gs]

awesome....thank you....one other measurement while you are it...my particular heads have a diagonal bolt pattern...just curious as to whether its the same as a SBF...though the port shape is entirely different...so maybe a bolt spacing(center to center) and offset(distance between the two holes horizontally) measurement too

 

[mrmustangman357]

exhaust manifolds save a lot of headache until you turbo it, and i bet they will fit your chassis fine

 

[jlangholzj]

and PICTURES!

alright, here ya go!


the port spacing is 4.5" on the nuts from center to center.
the bolt spacing is 2.25" from center to center.
outside bolt to outside bolt is 15.25" center to center.
and the total width is 16"


if you need any other measurements...(that you CAN't tell from the pics ) let me know!

 

[wicked93gs]

awesome, thank you very much, unfortunately it wont work....the port spacing is 4" on the 4.6L, which will be a inch off for the #1 and #4(or #5 and #8) ....so much for that idea...unless I redo the entire port side of the header and by that point I may as well build my own from scratch....as for exhaust manifolds, the only ones that will fit(driver's side anyway) are Marauder manifolds...not exactly easy to come by...or cheap when you do

 

[jlangholzj]

possibly buy a pair of these and hack off the top 2" of the header or so??? then build up from the flange and weld to where you cut off??

lol. ALOT like work, but good luck!

 

[wicked93gs]

the other thing I am worried about is the angle of the V8....its a lot steeper on a SBF...not sure what types of clearance issues that will cause, but I can imagine the collectors hitting the transmission or something weird like that, so I may just build my own from scratch...cant be that hard, just wish I had a better welder to work with

 

[bnickel]

i've had a kind of similar idea for a long time that basically involves using chevy LS manifolds on a SBF, not sure if it would work or not but i've been thinking about giving it a try. the idea is to keep the engine looking stock with cast manifolds but breathe better than stock SBF manifolds. i know the LS bore spacing is almost identical to the SBF engines so ny the same token i think the exhaust manifold spacing should be pretty close too. it would sure save me a lot of time porting and welding on a set of 351w or 289 hi-po manifolds to get the same or less flow if it would work.