guys I know, please bear with. I am starting this revisit to clarify things. First off, I have no interest in blowing up the T5 in this 92 RS I now own. I want to give it some pep, 250 maybe. I want to know more about Vortec heads. Their flow numbers, I seem to find numbers all over the place. What are they really? the 187 on the L03 I hear are great for Torque. Better the 520 or 059 flow better? I am not looking for 6000. 5000 or streetible is all I want. I will be doing exhaust, TBI throating, Dual snorkel L69 air clean and Posi 10 bolt other things of this nature. I figure maybe this is new territory given the lack of info I can find, 305 heads on 305 blocks. I do not plan on a 350 for this car. Just a simple V8 with a 5spd. So I come to the experts. If some of y'all could help me figure this out, thanks

 

059s off a low hour boat. Flowed 218 @ 0.450 and 224 @ 0.500. The TBI heads hold their own until 4,000-4,500 rpm. You are going to want it to be able to rev out to 5,500-6,000 rpm to get the most benifit from the Vortecs. Even with the tiny little 196/206@ .050 GM marine cam the Marine 305 Vortec made peak power at 5,100 rpm.

 

Thought I would repost this from another thread.

https://www.thirdgen.org/forums/tech...-stoplite.html




I think that concurs with Fast's result.

 

Also closely matches the results on Youtube.

https://youtu.be/qy90bOCTpjM

 

L30 heads are coming out of the woodwork all of the sudden! I love it.

 

Kind of funny isn't it.
I've always given props to the much maligned 305. To me it's still an SBC and whether you care about the most out the package , it's still a V8. FWIW, my 1st engine was a 307 and I hotrodded the crap out of that thing. Then transferred all the goodies like heads and intake to a junkyard find 400.
When my 350 had to be pulled for a refresh, I plunked my spare 305 (that had actually been a replacement for the 400 SBC that was in my 77 Chevy Van but that got scrapped) and used the headers and balance of the accessories for a direct drop in. All that was needed was a conventional pattern intake manifold as the 350 was Vortec headed. It was just about as enjoyable to drive especially if I kept it in 1st or 2nd and held the revs up a little.
Build a 305. I've got your back.

 

The 307 was twice the engine the 305 is, except for the potential of OEM roller rockers.

Standard-23-degree 2.02 valves will fit inside a 307. Good luck with that on a 305.

 

2.02 is not needed to make good power. I had 250 cfm of flow through a 1.94 valve. My friend David Kauffung put 2.00 valve Fastburns on his stock bore 305.

I will take a 1-piece rear main seal roller block over any of the older ones. The 305 can tolerate a bigger cam than a 307 without losing as much low-speed torque.

A nice little street performance engine is often square. The 334 gets really close with a 3.766 bore and 3.75 stroke. several engine masters wins are held by the 400 Ford. 4.00x4.00. A 390 cid stroked 318 mopar gets with the program pretty well too. Same can be said for a 5.4 Modular Ford. The 5.4 is a tall deck 4.6 with more stroke.

 

The 307 was as much looked down on back in my early car crafting days (late 70's/early 80's) as the 305 is today. Short stroke and small bore when compared to the 350 which were also plentiful.
Cylinder head notwithstanding today, those "fuelie" heads I mentioned were originally a 1.94/1.50. My college tech teacher in 77 / 78 (a racer at heart) explained the benefit of going to a 1.6 exhaust valve. I don't recall the logic now although it would probably be easy to cypher from the archives if I actually knew what heads I found in a local autobody shop's scrapyard. It may be he knew were bound for a 3.07 and the 2.02 , in unmodified form might have significant chamBer shrouding. Something I didn't know of at the time. That they eventually ended up on my 400 might have changed his mind. But that's lost in history know.

Anyway, the point here is, if you're getting in to the game or want to build what you have, it doesn't matter. The potential is there to build a decent TQ to CID no matter the configuration .

As for a 1.94 intake valve, I can give documented proof of an online racer I know that's well past 550 HP with his 383. And guys are taking their 1.94 Vortecs to levels I never would have imagined while making my aftermarket 2.02 Vortecs look lame by comparison. (But to be fair, my heads aren't at their potential).

I hear what you're saying just the same though. The 307 has a broader selection of aftermarket head choices but having a less than 4" bore is still limiting. Not as limiting as the 305 as from my limited search experiences have come up with only a couple, maybe three decent choices for cylinder heads.

 

There are several good 305 heads. Vortec 305, ZZ4 113 aluminum heads, Etec170s, Trickflows 305 offering and there is a Brodix spec head for the Racesaver 305 class.

 

There you go then. I knew of a couple but I tend to overlook the racing classes.
I had a set of 113's at one time but sold them to finance the then current engine program.
Would have liked to have kept them and all of the parts I've gathered over the years. A little impractical but I'd have a warehouse filled by now.
And I have a nice 82 Berlinetta roller that needs a drivetrain. Go figure.

 

I never knew the 059s were such good heads and flowed as good as they do. I do remember my Dad using a set of free 059s on a 350 in a Chevy truck once and it ran strong. I'm anxious to see some of these TBI 305 Vortec builds and how they run.

 

Me too! I had planned on reworking my interior last winter, and the drive-train this winter, but the garage fire through that whole schedule out the window.

The factory motor (L30 Vortec 305) was rated at 235 h.p. (a 65 horsepower jump from L03, and 5 better than the same Vortec components gave the 5.7L), so I figure with better exhaust and a few other goodies, I should be able to get 250 anyhow. That's 350 TPI territory (with a higher rpm torque peak). With a desire to keep a stock-ish 700R4 and 7.5" rear axle, I think that would all play well together.

When I first joined here, one of the earliest thread I followed was in the TBI forum, where a member had bought a crate L30, and was putting his L03 TBI system on top, and managing it/tuning it with EBL Flash. This was the first time that I had heard of EBL, and he seemed very happy with the end result, though I don't think he had ever perfected a few of his drivability issues. I think he eventually got tired of dealing with it and figured it was good enough for who it was for.

 

Don't underestimate the importance of this.
Get it as free flowing, with properly sized headers and enough flow capacity to the back including the mufflers, as is possible and/or practical.

 

Well, I think I have good coverage there. JetHot coated SLP stainless shorties for N10, into Magnaflow stainless N10 system (converters), into stainless Borla catback.

 

The limiting factor there is the short header. I would expect high flow cats in your system.
Plenty of California guys with full smog and Dyno Don's short header setup that make very, very good output. Legally...

For me, I need to have a full length header as it'll be run open when I'm going for the best result. There'll be a lot a thought into the race only exhaust. The street stuff will be what it is.

 

I can tell you I never expected my TBI build to run as strong as it does. I expected it to be a lil better than what I had honestly maybe 250hp. By upgrading the TBI and intake it pulls about another 1000rpm easy. I do have a lil headwork , headers, 3in exhaust, better pistons, 3.73 gears and torque converter but basicly a stock L98 on TBI. It really surprised me to outrun a charger and a couple C4s.

 

Thank you all for the feedback. I had login issues, I hope I have corrected, my apologies for not getting in on the conversation earlier. My plans when I was thinking about getting another 5 spd was to enjoy it without destroying the Brog Warner. I hope 250 hp is a reasonable goal. It is fun to drive, and it will be a street car. I don't want to go crazy with chrome and a lot of aftermarket. I have bought a 10 bolt posi, 3.42. The tires are a little different than the RS OEM. 225/55 frt and 245/50 rear. It gives it a bit of a different look and sits level at 25.7 inches. The only noticeable changes will be a Dual snorkel air cleaner L69 type and Headers. I have read that the 187 swirls on it now are great for bottom end torque, but I would like the pull pass 4000. As of now if am playing, the 3.08 puts the engine around 4500 in1st. My other idea, if it's true about the 187's, is a 2 stage Cam to help the Exhaust and port the heads. Actually, just clean them up and match the intake. Good Headers and 3.5 pipe. Any thoughts on this?

 

One other thing I wanted to add. It seems the 305 Vortech Heads are hard to find. I did not think that would be the case. I have posted in FB marketplace and checked junkyards I know of...so far, no luck. I see the trucks running around town. Maybe that is the problem, too many still running.

 

I hunted for several years before I found my set of 059s. They are not common.

 

FWIW a 350 won't eat your trans unless you abuse it. If you look outside this forum there are a lot of folks running 350/S10 combos on drivers (i.e. not racing).

A place you may want to check would be estate sales and police auctions. Some interesting stuff pops up on those more often than not and for not much money.

 

I will do that. I plan on checking the junk yards, too. I may end up buying a complete truck. If I find the right combo, seeing a lot of broken OBS's listed.

 

HP wont kill your transmission alone. It's the torque output. As long as you keep torque under 300, you'll be fine.

 

Or just drive it normally and avoid dumping the clutch at 5k and you can live with much higher torque #’s