I've been reading through the threads here for information on how to build up a 305 the last few weeks.

I'm at the point where my eyes are starting to bleed and my brain is muddling things altogether. I guess it is time to ask for some help.

I've read some web pages out there talking about 300+ hp from 305s. Must be flywheel...

I have a LO3 that I want to work with. Hey, I already own it and it was rebuilt ~10k miles ago.

I want the engine to be fairly daily driver friendly. I'd also like it to:

- be reasonably free breathing to ~5.5k-6k RPM (i.e. not sound strained).

- have a decently smooth idle from the camshaft.

- have aluminum heads and intake - weight is the devil. Implies matched camshaft?

- not break the bank! Nothing exotic...

- get decent fuel economy for what it is (hey, we can dream...)

- retain TBI if at all possible (would consider TPI conversion or aftermarket if not terribly expensive - just like the TBI's carb look). Will it go to 6+k RPM?

- have parts that might be able to be put on a 350 build at a later time (or have parts that could be sold later).

I was thinking along the lines of some L98 heads, LT1 cam, screw with the TBI code, Edelbrock intake. Maybe I should look at a more agressive cam/head combo?

Better options?

I'd be ecstatic with being able to consistently turn ETs in the high 13sec range. Realistic?

TIA!

 

How about vortec heads for a 350, machine down to 58cc (or smaller, depending on the compression your willing to run) combustion chambers and a vortec RPM manifold. TBI on top if you want. Maybe a mild cam, something in the 215-225 duration with .470 lift, vortec heads are supposed to be good for lift under .475. Headers, exhaust, and a good tune ought to easily bring in over 300 crank horsepower, all in a pretty economical package. I'm hoping for close to 300 crank hp by upgrading to just 350vortecs, machined to 56cc chambers, rpm vortec manifold, with my current 204/214 .423/.442 came, and the cc-Qjet on top. With more cam over 300hp would certainly be possible, with a still very streetable powerband. I would defintely reccomend a stall converter for any 305, and decent rear end gears.

 

Welcome aboard thirdgen.org, reece146.

You should first check out the TBI forum, if you haven't already. That where all of this is addressed.

I would say about the worst reason for building a 305 is because you have it. Since it's already been rebuilt, that's water under the bridge. But, the heads, cam, and exhaust are the performance killers, and fixing them requires fixing the PROM tuning. So, you're on the right track.

6000 RPMs is probably asking a bit much, but can probably be achieved. The idle overlap is where you're going to have problems, with it messing with the mind of the O2 sensor. Check what people have done on the TBI forum.

TBI is a little more than a glorified carb, as it addresses the low-speed problems that carbs have (needing the air flow to draw in the fuel), but it was never really fully exploited for performance. Holley makes a throttle body injection aftermarket retrofit system, so it can't be all bad, conceptually.

So, look over there and go from there.

 

Thanks for the input gents.

I'll go back to the TBI forum. I came away from there feeling that any combination could be made to run with the TBI given enough ECU fiddling. Is this not correct?

Let's assume I can make the TBI work for a minute. I'm not adverse to changing the EFI system, btw.

Is my choice of heads and cam going to be able to make ~300hp at the flywheel? Are there better choices for head and cam?

What compression could I run on 87 octane using aluminum heads? I was thinking ~10:1.

I really want to go with aluminum heads to get the weight down. This engine may end up in a locost ultimately. Weight is the devil. Also, a T-5 is about the half of the weight of a T56 so it would be better suited to a locost. A built 305 should let a T-5 live compared to a 350?

Given the same level of "builtness" wouldn't a 305 make proportionally the same power as a 350 while using proportionally the same amount of fuel?

Just throwing that out there.

Maybe I'd be better off to buy a LT1 or LS1? By the time the work is done the money may be a wash.

Any and all comments/insights appreciated.

T!

 

hmm, you're really still in the thinking and planning stages? I'd sit down and think about budget, and what you want to get out of the engine, and when you want to have it done. Think long and hard, then come on back here and decide. Suggestions may be moot at this point if your heart is set on something else.

 

Yeah, see, the thing is I have this LO3/700R4 holding down the dirt outside. I'm kinda attached to it for some unknown reason. I want to swap the 700R4 for a T5 and re-engine another car with it. All because it is cheaper to use what I have one hand versus getting all new junk.

If I could get to 300hp at the flywheel that would be "crazy power" for what the engine is going to be used for. I don't need any more than ~300hp at the most.

My biggest desire is to get as much weight off the engine as possible without breaking the bank.

 

ZZ4 cam

ZZ4 463 casting aluminum heads

Good headers

4bbl intake and Q-Jet or tuned TBI setup.

 

Thanks! I've been reading up a bit more since originally posting. It's starting to gell.

Versus LT4-HOT? Or is the Hot too much lift for the 305?

Should the heads be machined to 56cc? What'll that give me in CR? 10.x?

What can I get away with on 87 octane?

T!

 

The ZZ4 heads are 58cc to start with.

 

Hey.

Im doing a mild 350 build right now, and im aiming for about 250fwhp, or 190 - 200 rwhp.

My combo:
LT1 Cam (.450/.460 Duration: 202/208@50)
Lt1 Roller Lifters
Comp Cams Valve Springs
Edelbrock TES Headers
Taylor Spiro-pro Ignition Cables
160 Thermostat
Air Foil
3.42 10bolt Disc Rear

The Engine will rev upto about 5200 - 5500 rpm before the engine falls flat on its face. It is an LB9 Engine, with the tpi induction setup, the heads are stock 081 castings, which flow exeptionally well for a stock head.

If you end up with the bucks down to the full extent, get 081 castings, and do a nice bit of porting on them, if you feel the need, you could put bigger valves in. These heads have 58cc chambers, and with stock pistons, will make a 9.3:1 Compression ratio.

Personally, as a TPI guy, i feel that the TPI is one of the greatest systems ever, for driveability, fuel consumption, emissions etc. Very expandable, with the stealth ram systems, mini ram, or the LT1 intake conversion, which works extremely well.

Lt4 hot cam would be fine in the engine, its about the max cam you can put in as EFI doesnt like any more duration then that.

Hope this helps.

Sheldon

 

I had the same dilema too.. prep up my 305... But after much reading, it was actually cheaper to get a moderate 350... I mean for the hp/$. so I bought a short block and prep it up to be smiliar to a GM ZZ3 engine. (this was way back).

I have to say... 350! Nice!!!

I would definetlay recomend a GM ZZ# grate engine (if you could afford it). or build it to be like that.

 

Well I hopped up my 305 because thats what my car had in it, and it had only 70,000kms on it. So I started looking around and picking up parts that would work well for my 305, yet be transferable to a 350 down the road.

What did I end up with? A pretty healthy sounding and running 305 that pulls pretty hard and surprises the 350 and LT1 guys. I started with a TPI LB9 305 roller block.

Here is a quick break down;

aluminum L98 corvette heads: ebay $600
LT4 hotcam kit (cam, 1.6rr, springs, etc) : summitracing $500
headers: mopac auto supply $400
gasket kit, locktite, etc: $100
custom prom: time and effort, minimal expense

Total: $1500 USD

Now thats the basics of it. I did the work myself over a week when I had free time. Everything I used can be take off/out and reused in a 350. Pretty decent if you ask me.

Pulls hard, reliable, still gets good gas milage. I ended up picking up a TPIS intake, SLP runners, and a mega ported plenum. I'll bolt these on in the spring and see what happens. In the mean time, I've got a 355 sitting on an engine stand getting prepped.

 

Thanks for the pointers guys.

Ok, so this is what I'm thinking

- ZZ4 463 casting aluminum heads
- LT4-HOT

If the cam doesn't work for me in the day to day I'll swap it out.

What about changing the EFI type? I was talking to a friend over the weekend and he offered a TPI setup (LB9 I think) in exchange for a couple boxes of beer.

I really like the look of the LT1 style intakes. Is there a way to get one on a Gen I 305 engine with TPI EFI system without it falling on its face?

Or should I stick with the TBI? Will an RPM air gap work with these heads/cams? I have the hood clearance (errr, don't mind making it).

Any of this stuff can be transfered to a 350 but will any of it work on a 305?

TIA

 

I'm seeing some pretty impressive 305 based builds on this forum.

I'm going to do LT1/TPI hybrid on a 305 bottom end.

I will run aluminum heads.

Assuming I use the ZZ4 heads, what is the max compression I can run on 87 octane? 10.5:1? Less? More?

Will a different head with similar flow numbers let me run more compression?

What about 305 specific heads? What are the issues (if any) with running the ZZ4 on a 305 bottom end?

T!

 

87 octane? About 9.5:1 tops.

87 octane is what soccer moms run, time to step up to premium fuel if you're going to play with sports cars. Then you can run 10:1 or so and regain the bottom end.

 

What, f-bodies are sports cars now? Was there a memo? I didn't get it.

LOL <j/k>

Even with the Al heads you figure "only" 9.5-9.7?

 

haha, you weren't at the meeting I guess

yea, 87 octane is weak. 8.5-9 on iron heads, 9.5 or so on aluminum. We're talking about less than perfect efficiency burn heads here, not the TBI or Vortec or fast burns.
There's lots of discussions on CR recommended, but usually it's assumed with 91-93 octane premium. That's where 9.5-10 on iron, 10-10.5 on AL.
Depends mostly on chamber design, quench distance, altitude, induction system, CAMSHAFT (almost forgot about that), restrictions on intake (back to induction really).... etc etc

 

Ok, gotcha.

So, since I'd likely be buying new (to me) heads anyway, is there a fast burn in aluminum that will work with a LT1 intake? I want to maximize compression on 87 and build the rest of the engine around it.

I've heard good things about the E-Tecs but then is there a 305 variant and Ebrock seems quite expensive for what it is a lot of the time...

Hmm, LT4 is vortec pattern no? Aluminum LT4 compatible heads and intake?

This car will likely be driven back and forth to work (~80 miles round trip) quite a bit in the summer time so I'd like to stick with 87 if possible. If I can get the compression to 10.x:1 without it pinging like a b!tch that would be good from my perspective.

TIA!

 

for what its worth, I run 87 octane

 

I doubt you'll be able to run 10.x and 87 octane. I just don't think it'll happen.

Throw on a restrictor plate, then you can. Not a smart idea in the slightest, but if you've got your heart set on the bragging rights of saying "10:1 compression!", then you can do that

LT1 heads work pretty good with an LT1 intake , if you don't mind the modifications to the cooling system.

"350" heads fit remarkably well on a 305. The bolts line up, etc. No reason you can't use 'em. You'll need 58cc chambers or less if you're hoping to have a reasonably high compression ratio.

LT4? As in LT4 heads? Vortec is vortec. Only vortec is vortec, nothing else. E-tec is a variety of vortec, but I'm pretty sure that's the only exception.

Look into all the ways to eliminate detonation. Piston/head thermal coatings, eliminating sharp edges, bigger cam, better fuel distribution/atomization, better swirl, etc. See what YOU can accomplish from where are.

 

Fastburns are Vortec, too.

 

The Crane cam Powermax 20/20 works fine in my 305 and its not to radical for the street.

 

Ok, last questions and after this I'll go stew on this for a while.

Which year TPI harness should I use? I'm interested in most tunability and potentially most robust/reliable (if any are different). In case it makes a difference, the plan is to use a LT1 intake manifold.

This is going in a custom vehicle so I don't need to worry about emissions.

Thanks everyone!

 

The '90-'92 speed density systems are more flexible and capable than the earlier MAF systems. They also require more tuning with engine changes, but that shouldn't be a big deal.

 

Cool, thanks.

Time to get shopping.