Marc 85Z28

Look harder, not just internet sites. I know of 2 local machine shops that have both 350 Vortec castings in stock and for $450/pair stock complete, $550 with some cleanup, redrilled intake holes, cut pockets and better springs.

85_305

Actually the stock heads on the 305's flow very nicely, and if you get some work done to them they can flow exceptionally well

slimdawson

/\Agreed. The biggest limiting factor is the bore diameter.

85_305

^Not the bore, but the stroke.

slimdawson

You can stroke it to the moon but the bores will always shroud the valves. You can fix the stroke, but you can't fix the bores. It also has the same stroke as a 350 but you don't hear about people ragging on the 350's stroke.

ws6transam

Come on, Matt!@ Why disagree on everything? Think it through before replying:

3.736 inch bore on a 305, compared to the 4.00 inch bore of a 350. It makes it hard for the air to get past the intake valve, which is why it's hard to make a 305 breathe. The biggest valve you can fit in there is a 1.94 inch intake valve. Some folks will actually relieve the tops of the 305 cylinders around the intake valve in order to try and make better air flow, but it's gutsy with the water jacket so close and all...

As for the stroke, the 305 and 350 use the same 3.48 inch stroke.

For the record, you *can* make 305 heads flow fairly well with old fashioned porting, but in reality, unless you can do most of the work yourself, it's cheaper to simply replace those heads.
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Lil305GTA:

If you want to beat the Mustang, put in 3.73 gears which are PERFECT for the 305, making sure you have also included a functional limited slip differential. Put in a 2400 to 2700 RPM torque converter, too. It wont compromise streetability one bit and will enable your TPI to really launch you off the line, assuming you've replaced your lower control arms with some aftermarket pieces.

Then, as Mark says, replace that cam. I like to lean towards the Comp Xtreme Energy cams, and after using two of them in my feeble305, think the best one for the TPI305 is probably the XE254, with some new Comp 981-16 valve springs and retainers. It's a $160 camshaft, plus $60 worth of springs.

If you want to assure the win, buy the vortech heads and the SDPC Vortech intake manifold. I think there's a couple TPI intakes out there for Vortech heads now, so shop around. Either way, get the heads with intake valves no larger than 1.94 and exhaust valves no larger than 1.50. When installing you will have to pay careful attention to valve/piston clearance. Install the heads with a .015" steel head gasket too, or you will lose significant compression ratio.

Lastly, get yourself some new programming for your ECM that takes the changes into account.

85_305

Yes guys, I wasn't thinking when I posted that I relized when I was laying in bed, about to fall asleep that I messed up when I typed that, lol. *proceeds to bang head off concrete wall*

But ws6transam; why are 373's perfect for a 305?

EDIT: And does anybody know the headgasket thickness in this rebuild kit?
http://www.jegs.com/cgi-bin/ncommerc...25&prmenbr=361
Thanks,
Matt

ws6transam

Cant help you with the gasket thickness, but look for one with a compressed volume of 3.2 cc.

The reason 3.73's are great is because the 305 is naturally a little less up on torque when compared to the 350, and the gears will launch you better with the right tires. Plus, the 3.73's will put you through the traps at 100 MPH in third gear, right about 5000 RPM. ...also when you cruise on the highway, you'll be turning 2600 RPM at 70 MPH, where your 305 will be making good peak torque, giving you a nice, lively throttle response on the interstate. I've had 3.73's since my car had ZERO miles on the odometer, and I'll never have it any other way. They are working great with the T56 and my 450+ HP Minirammed 385, too: I'm hitting 6000 RPM in fourth in the traps.

85_305

2600rpm at 70mph.. isn't that a bit high?
ARe you giving me these 'trapped estimates' using the 6spd of yours, or using my 5spd?

cc89formula

at 90mph im at 3000rpm and i love it, but thats with 3.23s and an A4...and does matter if really hes talking about the 5 speed or 6 speed. I would have thought they were geared the same until the overdrive(s) but maybe im wrong...