I'm just wondering if anyone has done this, because that's were I'm headed.
I'm installing free-flowing mods on my 305. So far I have SLPrunners with my port matched plennum. I'm getting the Big mouth intake installed next, as well as two aftermarket cats(see my other mods).
What kind of 1/4 mile/HP@?RPM can you expect from a fully "free breathing" 305TPI with a 4.10 rear and 26.4 inch rear tires?
By "free breathing" I mean; 52/58MM TB,Ported intake(siamesed to Ported runners),Ported SLP Runners matched to siamessed plenum. And exhaust that's in my sig(plus free flowing cats).
What do you guys think? A high reving(?)305 that compensates w/a low rear end?
Thans in advance.
PS. All these goodies will eventually find their way on to a ZZ4 block.


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1990 Formula
Factory:TPI-305/Dual Cat(230hp),5 Speed,3.42 rear.
Dealer instaled:Aluminum Drive Shaft
Mods:SLP air foil,K&N Filter, Accel:wires,coil cap,rotor.Hypertech Thermomaster chip,Stat,Fan switch,TES headers,MSD6AL,AFPR(50), Harwood fiberglass hood.
Flowmaster 3" Cat-back exhaust,TB coolant bypass,B&M Ripper shifter, Centerforce dual friction clutch, Ported & Siamesed Plenum matched to SLP Runners, March Power/Amp Pulleys, Richmond 4.10 gears. (???HP)

 

Sounds like an interesting, but good, combination. I'd like to see how the power curve looks on a dyno and what times it turns in the 1/4-mile. Since you have the 350 cam, I'm guessing the power will peak at 4600-4800 rpm, and (with good traction) you might be able to hit the low 14's or even high 13's depending on how well it's tuned.

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Greg Westphal
'87 IROC 355TPI/A4

 

This is just MHO, but i wouldn't worry about a runner swap until i was into the heads and cam and base first. Those 3 present a bigger restriction IMO than the runners. You may see a couple tenths (especially since they'll help extend your powerband slightly since they are a semi-siamesed design, and those 4.10s are hella short for a TPI car.)

 

I have a lot of the same mods you do(minus the 4.10's, MSD box, pulleys, hood, and slicks)and I've run a 14.0 with consistent times in the low 14's. Sounds like you might have a 13.5-13.9 car. Those 4.10's should work great with your newfound upper rpm power.

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90 Black Formula
5.0 TPI 5spd lotsamods

 

Well, I finally installed the Edlebrock Base. In retrospect, I wish I would have done this at the same time I was installing the runners but I guess, hindsight is 20/20, like they say.
I do feel some loss of bottom end TQ, as predicted but with 4,10s my 1st gear was useless anyway. I still spin a lot but there's more power up-top. My new 265/50/16s BFGoodrich rear tires help quite a bit.
I'm gonna try to take it t E-town before season's end. But my Formula, as little as I drive it, is mostly for the ocassional street race. I got the 4,10s because it gives me better pull in any gear selection. Street races accur from a variety of situations; light to light, on the highway and from a roll(at different rpm ranges). For my "application" 4,10s work great.
Thanks for all your input, guys.