1991tealRSt-topGuy

305 heads from say an 85 monte carlo

OR

350 heads from a 78 4bbl chevy truck


?????

i need to know, because whatever ones do, they are comming to school with me for a 3 angle valve job

RB83L69

The 350 heads will flow more.

But that's not saying much... the 305 heads are probably 416s and have 1.84" intake valves; the 350 heads are probably 882s or 624s, and have 1.94"/1.5" valves and 76cc combustion chambers.

I hope you're only going to use this for practice, on heads you're going to throw in the trash anyway, so when you get a set of real heads you won't do yor learning on them.

jimmy_mac

What are you gonna do with them. The 350 heads probably won't fit on a 305. The vavles will likely either hit the cylinder walls or be shrouded horribly. If you are using them on a 350, the 305 heads will raise your compression ratio but flow slightly less.

Mark A Shields

The 350 heads, should fit no problem, I would think.

Sitting Bull

Hah! Take the 305 heads and port and polish them according to the instructions in the link at the end of my sig. They can be made to flow like Vortecs and cost a LOT less

rezinn

Did you have them flowed, Sitting Bull?

RB83L69

305 heads will never flow like Vortecs. We need to quit hearing that. If they would, nobody would need Dart or World or Trick Flow or AFR heads any more, those guys could all just fold up shop and go home. You'd never hear of any professional racers buying heads, they'd all just go to the junkyard and pick up some crap heads, and stomp the people with the expensive heads. Somehow I haven't noticed that happening too much.

In fact, it kind of reminds me of how a few years ago, everybody noticed that Vega Turbo 350 torque converters were looser than any others, so the budget kind of people years all went out and got junk Vega converters. Problem was, they didn't win races. If they were all that good, you'd think maybe once in a while they'd be competitive; but they weren't. As each of them came to the bitter realization that sometimes you get what you pay for, they picked up time when they went to a properly built racing converter, every time.

305 heads can be made to flow better than they do from the factory, that much is for sure. As good as some 350 heads? maybe. As well as Vortecs, or even old double-humps? I don't think so.

There's a time and a place, and the right circumstances, for maxing out a set of 416s. A 350 isn't it. They will get beat by an amazing variety of other stock castings.

Sitting Bull

Well, I DON'T say things unless I can back up what I say.

Here is the flowbench data that F-Bird'88 came up with for his 305 heads. I quote:
_______________

Only have the flow numbers for the "081" '87/'91 305 heads.

They flow:

195cfm@.500 in.(182@.400") and
110cfm@.500 ex.

Other stock 305 heads with 1.84"in and 1.5" ex valves
will flow real close to this as this is very typical.

The last set of 305 heads I ported and flowed were
"416" castings and flowed:

225cfm@.500 in. and

140cfm@.500 ex.

through 1.94x 1.60" valves.

Should give you an idea of where you're at and the potential.
_________________

If you recognise those last numbers you are correct: they ARE the same numbers as L31 Vortec heads flow!

I believe the last set he did flowed somewhere around 170 cfm on the exhaust side.

In the February 2002 issue of Car Craft, on page 54, under the "How to Port Cylinder Heads" article, they state that AirFlow Research has quantified the question of Air Flow = HP with a formula, which they claim is "fairly well established." It reads thusly:

hp = cfm x 0.2575 x number of cylinders.

So just plug in your numbers and it should be pretty close.

Let's use the stock L31 Vortec head as an example. Its maximum flow is supposed to be 226 cfm at .500 lift. (This is according to Destop Dyno 2000's flow file.)

Therefore we arrive at 226 x 0.2575 x 8 = 465.56 hp

Thus the ported 305 heads will produce 465 hp as well!!!

That WILL keep a well built 350 very happy, too

What say ye doubters now???

I think it is pretty clear that folks spend money on aftermarket heads SIMPLY because they DON'T KNOW how well these little old 305 heads will work

PS This is all accomplished for about $400 US. F-Bird'88 was selling a set of these just a week or two ago for $375 US plus shipping.

RB83L69

I'll believe it when I see time slips, dyno pulls, etc.

I'll especially believe it when I see people winning races that way.

Sitting Bull

I refer you, sir, to F-Bird'88. He can supply even more up to date data. He had them flowed by a friend of his who also does head work for CASCAR.

And he races his Firebird all the time.

But the formula is entirely scientific. That IS the hp they can develop.

Sitting Bull

And here is what these little beauties look like when they are done.

Sitting Bull

Opposite side view.

Sitting Bull

And the combustion chamber side, with resized 1.94" intake valves

Sitting Bull

They keep my little 305 VERY happy, indeed

And F-Bird'88 tells me he has folks running them on 400 ci smallblocks with NO complaints

RB83L69

So what kind of times does it run? or what engine or RW dyno numbers do you have? Prove that it outruns the same motor with some other kind of heads on it.

One guys numbers from some flow bench somewhere compared to somebody else's numbers on some other flow bench is not an apples-to-apples comparison. I'm not a flow bench or Desktop Dyno kind of guy, and I'm not easily impressed by pictures, I like to see results.

Sitting Bull

Man, you sound JUST like F-Bird'88!!!

He says exactly the same things you do! "Don't give me no baloney! I wanna see time slips! I want dyno numbers!"

Talk to him. He's got all the info you want. He's on this board EVERY day

Maybe you two could get a good thing going. You both love tinkering to no end. Why not produce and package these 305 heads? You could undercut the Vortec market by a long shot!

1991tealRSt-topGuy

well, wisdom would tell me that:

if you can get crappy flowing 305 heads flowing that good

that you can

get decent flowing 350 EVEN better

is this true?

so far i am going to bring the 350 heads in, i have a 2nd set of 305 heads i am going to put on the engine for now

then i MITE try my hand at porting the 350 heads.........

Sitting Bull

Wisdom is blowing smoke in your ear, unfortunately.

The problem with all those smog era 350 heads is their massive combustion chambers. 76 cc requires a lot of milling to reduce it to a useable 64 cc or so. In fact, they probably can't even be milled that far without weakening them fatally.

The 305 heads have 58 cc combustion chambers, ideal for high performance.

As for the intake runners, that's what porting is all about. You simply open those 305 runners out to 175 cc or so and you're in business.

F-Bird'88 cc'd a set of 416 305 intake runners and they come out to 167 cc from the factory, so you don't need to do a lot to get them the same as Vortecs.

Don't get freaked out just because the heads come off a 305. They look identical to most other smallblock heads from the outside.

1991tealRSt-topGuy

ehhhhhh, i totally disassembled one 350 head

there are indeed 624's

THEY ONLY HAVE 1.72 INTAKE VALVES!!!!!!!!!!!!!!

DAMN THAT SUCKS

looks like i am going with the 305 heads after all

F-BIRD'88

The latest set I did with 1.94 x1.60" valves flowed 238@28" in
and 189 ex.

Thats not too shabby for something that you'd throw in the garbage.
Even my friend with the flow bench was shocked. "This thing must be leaking or something!!"

We flowed a set of Brodix -8's and a set of 2.02 Vortecs
at the same time so we know the bench was operating right.
Outflowed the unported 2.02 vortecs and a set of mildly ported
041's.

If it ever stops raining here:
I will be getting them on the car (with a few other mods
single plane intake .550" lift solid cam, 12.65:1 cr)
and will report on their performance.
My vortecs (Set A) are coming off. Flow was 228@28" on these vortecs and it runs 13.05. Won't be a direct comparision but...

Looking for a 12.6? et at about 108mph
I'm curious to see what these 305 heads would do on the dyno
also.... maybe some day.

In my opinion these 305 heads have a little more potential
than the common open chamber smoggers if you're willing to
put the work and bigger valves into them. The combustion chamber size and shape is better especially after a lil reshaping (unshrouding). The ports are about the same.

Note: These 305 heads are not lightly ported. a lil pocket port
will not cut it. Plan on removing some metal.

Xenodrgn

It's all about combustion chamber design... ported 305 heads, even if they flow more than vortec heads or any other performance head, will never make equal or more HP... the improved design of race heads will always win...

Flow is only half the battle...

Sitting Bull

These are my "601" 305 casting's combustion chambers. Not too terribly different than a Vortec's, is it?

And flow is a LOT more than half the battle!

Xenodrgn

They look nothing like my Vortecs...

Sitting Bull

Oh really?

Vortec's have a widows peak on the straight side of the chamber and the spark plug boss protrudes into the chamber a little more. And THAT'S about it, believe it or not

Sitting Bull

Here is a Vortec combustion chamber, to prove my point!

1991tealRSt-topGuy

sitting bull- did you enlarge the valveseat to accept the larger valves yourself? if so, how did you do it?

also, what is the bowl area? i dont understand what that is

also, what is meant by pocket porting?

Sitting Bull

The machine shop does the valve enlarging. It's a simple procedure if you have the equipment and doesn't cost very much. In fact, I started with completely bare heads--no valves, not springs, nothing--and ALL of the machine work and valves, springs, etc., cost about $300 US.

The bowl is the area where the runner ends and the "bowl" area under the valve forms. You can see it in the pics I posted.

Pocket porting is working over the bowl area with a carbide cutter in order to take off any sharp edges and jagged juts, and to smooth the transition area from the runner and valve seat into the bowl.

It is NOT rocket science. All you need to do is take your time and work methodically. Patience will deliver you an excellent set of smallblock heads that will last you for years

1991tealRSt-topGuy

sitting bull- how much did the machine shop charge to enlarge the valve seats?

Sitting Bull

$10 Canadian per valve. I only did the intakes.

In the states it would be about $5 or $6 per valve.

goneracin

Your formula is not entirely accurate. Combustion chamber size, shape, manifold tuning, velocity, cam timing, and many other things all enter into horsepower. Using the above formula, my 1300 hp 500 inch prostock motor should make only about 1135, but i have the dyno sheets to prove 1293 @ 8900 rpm. We dont race flowbenches, nor does a flowbench take into consideration the recovery dynamics of a port. While im not saying you cant make a very good set of heads out of a set of 305 heads, you can make a better set out of heads that start life as better heads. I have built 11 second 350's out of old 283 as well as 305 heads, but could have been even better with a better heart chamber (high swirl) and more efficient runners to start with. The 305 heads that he is selling should make for a decent running piece, for a very reasonable price however.

Aaron91RS

iTrader: (2)

Heres some flow numbers for some ported 86 305 heads (416 casting)
Stock valves

Intake: .200 .300 .400 .450 .500 (valve lift)
CFM:__119_172__201_207_207 (flow)

Exhaust:.200 .300 .400 .450 .500 (valve lift)
CFM:___ 93__127_143_168_169 (flow)

Sitting Bull

Hey, thanks for the reply!

I guess the old 305 heads might be able to produce over 500 hp

Sitting Bull

Terrific numbers on the exhaust side.

Just need a little more on the intake and you've got some smokin' heads

F-BIRD'88

They may have been flowed without radius plates on the intake port opening.
This eliminates the "edge effect" of the sharp port entry.
The difference is about 10 to 20 cfm.

The proper way to flow a head is with a radius plate.

Although some people don't do this.

They also may have not been ported near as much as i do them.

What size valve? that would be good numbers for a 1.84" valve.

The exhaust side is good thou.