What's this pre-filter thingy you speak of? Is it inside the air cleaner snout?
As stupid as somethings seem at first glance... Its actually not stupid... Its called a flame retarding ring.. its purpose is to absorb gasoline fumes and prevent a backfire through the carb, which can cause a fire and or simply ruin the
H/O carb. (A carb that is getting harder and harder to find... ) There are plenty of tricks to improve flow of your exhaust, without pissing off the Smog Nazi's... What they cant see, they wont know... That said, the Olds 307 is a bit far from its "Rocket Olds" brethren of yore, but it was pretty slick for its day. Little healthier cam, clean up the head's ports, a cleanup of the valves, massage the intake manifold's plenum, mandrel bent exhaust parts (ie no kinks)... .
Now, correct me if Im wrong, but wasnt there 2 versions of the Olds 307 exhaust manifolds? Thicker ones used on Caddy's, Wagons, & Tow Package-equipped B cars?
As for the Air Cleaner issue... solutions can be pretty simple and as easy as the boneyard. If you can find an older Olds aircleaner with the larger snorkel and duct, you can swap it on and they might not even realize it...
Comparatively, Chevy had used a few exhaust tricks to squeeze a little juice out of their CCC Qjet 305... The F-Body L69 has a bunch of things that really stepped it up over the LG4... amongst the healthy list was a few on the exhaust... They have larger I.D. exhaust manifolds (later reused for the LB9 & L98 TPI F-Body's) 3" Y Pipe, 3" cat, 3" headpipe out to a highflow muffler to (2) 2 1/2" tailpipes...
Notable 80's GM air induction/air cleaner layouts... The '82 (Crossfire only), '83 (crossfire & L69), & all '84 T/As (LG4 & L69) used a "functional" cowl induction hood (turbo hood) that had a special air lid with a hole that sealed to the hood but used the basic V8 F-Body air cleaner... Crossfire's have a larger diamond-shaped hole that mayes to a special air cleaner...LG4/L69 has a round circle hole.
The '82/'83 Z28 w/ crossfire used a functional ram air hood that mated to the Crossfire air cleaner (different from the Firebird version)
The'83/'86 Z28/IROC-Z w/ L69 used a true dual snorkel air cleaner that has seperate ducts that attatch to the rad support... its very close in design as the late 70's/early 80's Vette design, but slightly different, & the ducting wasnt the same.
In '85, the T/A was redesigned and the Turbo hood was abandoned, so Pontiac used Chevy's dual snorkel on the L69 T/As is '85 & '86.
GM re-Issued this dual snorkel for its ZZ3/ZZ4 50-state Emissions Legal 3rd Gen F-Body swap.l
The '88 Monte had an uber-rare dual snorkel available, Ive only seen 2. Not sure if it was a Dealer/Parts Counter item or actual Chevy option on the L69.
And sadly, there is the
H/O - 442 307 air cleaner... really a piss-poor design there.. put a second, "open" snorkel, pointing towards the firewall, mere inches from said firewall, to suck in all that nice and Hot, dirty air.. at least they had actual ductwork going to the Rad Support.
All in All, All GM did was pretty much take air cleaner parts already in their bins and tack them on... using stock GM pieces to create a better dual snorkel for your Olds wouldnt be hard. You can cut off another long snorkel from an Olds 307 air cleaner, tackweld or rivet it onto your "good" one, cut the hole in it, add a Tee into the thermovac's vacuum line to operate the second thermovac... then hunt down a V6 Pass Side duct setup.... its the mirror of the Olds 307 one but a little hard to find. Paint it all GM engine black and youre done... if the smog Nazis ask, point to all of the stock GM pieces and say you repainted it because it was ugly with rust. .
