I'm looking for what modifications/combinations you have for a 305 that puts 260hp/300tq to the wheels.

 

100 shot of N2O.

 

Didn't see that one coming... guess it's a possibility for a road race car, but I bet that's one hella big bottle for a 40 minute race!

 

Check out the thread on the FAQ forum about differences between 305's and performance modifications.

 

Good information, but not quite what I was looking for. I'm looking for real numbers, not factory or guesses. Not really just general upgrages to increaes power to an unknown level. Real dyno numbers, no butt dynos allowed

I was looking for "These headers + an edelbrock carb= 250" or "this cam + 1.6 rockers on a TPI = 270" or "K&N + supersekret tune = 260" and yeah, I'll even take "100 shot of N2O = 295"

Guess I'll explain my reasoning...
In the class I run, CMC, they just announced a horsepower limit increase. It was limited to 230/300, with rules being mostly stock (manifolds, cam etc). A fresh built LB9 is right at those numbers. Mine, 180k miles, is at 209/276

Now they just bumped up that limit to 260/300 and are looking for ideas of what will be needed to put that number down on a dyno.

 

http://www.goingfaster.com/spo/290hp305.html

RHS built this motor, its only 290hp, but its a pretty darn small cam. Didn't read the article recently, but I'm assuming they used the AFR 180's. I think you could use the Vortec heads with very similiar results.

You need to make about 310 hp and 350 ft/lbs at the motor to reach your goal at the wheels.

Here's a question I have though, many dynos are different, how do you plan on not going over?

 

Car Craft did a build up many years back..with a parts list for maximizing the 305 TBI, think they got about 300hp, I'll have to dig around and see if I kept that info..was around 93-95 when that was done.

 

Heads, cam, and exhaust should get you in that vicinity.

I'd look at a 3 inch exhaust with long tube headers (short tube if you are worried about ground clearance). Heads and cam combo depends on where you want your powerband.

 

i'm afraid you put cam and heads on a TPI car you'll make the hp but the torque will be well over the limit. I'd suggest a mild cam and HSR as a start to flatten the torque curve while limiting the peak numbers alittle and definately increasing Hp.

flatter broader torque curve is better for road racing anyway

 

He's looking for a proven combination. That's pretty difficult to pinpoint, and you're probably going to end up changing your cam.

Guessing that your going to have some sharp low speed turns, you will want a good wide powerband, which means you will need VERY good parts to be competetive. I don't know anything about road racing, wish I did, but I do know a few things about dirt track racing.

An edelbrock performer intake, (RPM might lose considerable low end tq, gain slight top end), 650 cfm carb, 170-180 cc heads, 1 5/8 long tube headers, single 3" exhaust, cam-good luck.
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HSR might be a bit big for a 305 that needs a wide curve. Superram might be better if you're going FI.

Do you have any idea what rpm range you'll be in?

 

No specific RPM range, but low enough to make it live and not have to rebuild the bottom end every season. Dyno numbers have to come from a Dynojet brand dynamometer, so kinda keeps the numbers close.

It does sound like it will definetly involve a cam swap and exhaust, maybe intake. I would hope that heads (or porting) would not be absolutely necessary to get up to 260. Most people currently run the 081 casting heads from the TPI.

 

Well I'm sure its possible, but the cam will be ever more important and you will most likely be swapping a few cams until your happy. Or competitive.

Better heads and intake with a smaller cam (smaller than it would take to make the same power with those heads and tpi) would yield a wider curve.


You may just have to do some experimenting. Start with some good heads (aluminum milled L98 if they're allowed) a cam, and the tpi. Work your exhaust and see what numbers you get.

If your using the 86 305 tpi, your only starting out with 190hp I believe.

 

Experimenting = money I don't have

FWIW, my motor is a Speed Density TPI setup, the entire drivetrain, heck the whole car minus the shell is from a 92 b4c 1le, just the body is an 86.

It has 180k, a/c and air pump delete pullys, underdrive crank pully, K&N filters, no cats, stock manifolds and y-pipe (from a dual cat car), new valve springs and it puts out 209/276.

Thanks for the input guys, keep em coming.

 

Well do the important things first, headers, exhaust, cam, tune. See where you are, could be close. Leftover money, put it in the heads.

 

thats a stout 305 base so far. 209 isnt to shabby at all.

road race cams tend to have alot of exhaust duration split compared to intake duration. somewhat tighter LSA would be nice. ZZ4 isnt a bad cam nor is the ZZ9 from TPIS. Probly both capable of getting near 260whp with head swap and full exhaust.

Hotcam isnt a bad choice either but will make that 305 a rev machine and will love slp siamesed runners and ported base if you keep TPI

 

When I still ran my 305 with a 5-speed I had 252 RWHP and 317 RWTQ with this combination. I am sure other combinations of heads could give the same results.

-350 Vortec heads
-1098 felpro steel shim head gasket
-SDPC intake manifold, TPIS large tube runners
-ZZ-4 cam
-Max headers and cat back exhaust
-Stock chip worked fine
-Stock 19 LB injectors worked fine
-SLP cold air intake

I am sure you could use a set of conventional heads and intake to make the same power as the vortec heads and SDPC intake.