kdrolt

The following is my post from the "garage ported 193 head casting" thread from 4/05. I believe in attribution so I have documented where all this data came from, and who the original author was, to my best ability. I will make corrections if you PM me. FWIW, HTH.
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Stock (unported) peak cfm's summarized L to R by: casting number suffix (last 3 digits), material, RPO code, cfm peaks for int & exh and owner. The owner/thread posters: ME Leigh, smithtc, rhuarc30 and Dyno Don are all from TGO threads. All the heads listed have small-vol intake ports (approx 168-170 cc stock).

The SP heads are the LB4 (casting #?), 187 and 193 castings.

262 v6 head, ?"/?"
iron LB4 head: 165 intake; 119 exh (? source)
iron LB4 head: 138 intake; 116 exh (HRM, 1.94"/1.50")

305 heads, 1.84"/1.50"
187 iron LO3 head: 165 intake; 140 exh (Fast355)
081 iron head: 195 intake; 110 exh (ME Leigh)

350 heads, 1.94"/1.50" unless otherwise specified
083 iron L98 head: 185 intake; 106 exh (smithtc)
083 iron L98 head: 194 intake; 118 exh (rhuarc30)
083 iron L98 head: 202 intake; 141 exh, as posted by (F-BIRD'88, but he's not the author)
113 alum L98 head: 199 intake; 149 exh (Chevy High Performance)
113 alum L98 head: 182 intake; 145 exh (Vizard book, p124,127)
113 alum L98 head: 193 intake; 162 exh (GMHTP, 1.94/1.50)
193 iron LO5 head: 178 intake; 146 exh (Dyno Don)

Also see http://www.fullsizechevy.com/forums/...d.php?t=178604 for newer stock data from Fast305 (nee Fast355 on TGO).
193 head: 0.500----178.9----146.8 1995 Tahoe
083 head: 0.500----192.3----116.9

The relevant TGO threads and web sources for these:

https://www.thirdgen.org/techbb2/sho...hreadid=198595

https://www.thirdgen.org/techbb2/sho...hreadid=177465
https://www.thirdgen.org/techbb2/sho...&highlight=LO5

https://www.thirdgen.org/techbb2/sho...hreadid=268064

https://www.thirdgen.org/techbb2/sho...threadid=97882

https://www.thirdgen.org/techbb2/sho...416+heads+flow

https://www.thirdgen.org/techbb2/sho...+head+flow+cfm

http://www.chevyhiperformance.com/te...98/index4.html

http://herning.crosswinds.net/projects/350heads.html

http://www.hotrod.com/techarticles/e...v6/index1.html


L98 iron vs L98 alum (083 vs 113 castings):
http://www.chevyhiperformance.com/te...359/index.html
http://www.chevyhiperformance.com/te...59/index2.html
http://www.chevyhiperformance.com/te...59/index3.html

The 187 casting data came from a Fast355 PM, and some came from Vizard's book Build & Modify Chevrolet SB Cylinder Heads. They confirm other tests on L98 heads.

The 081 head (305 v8) was added because 081 (and 416) are often mentioned as being decent factory heads. The 081s are apparently the same as the 416s, except that one is used with centerbolt vcs, and the other uses perimeter bolt vcs. I also included the 4.3 liter v6 LB4 data from the Hot Rod mag data on SP LB4 heads ( swirl ramp based on the pix from their article). The other LB4 data appears on the web in several places but w/no source listed.

I also added Fast355's data on stock 187 casting SP 305 LO3 heads. Like the 193 SP heads, they don't flow as well on the int side but they flow better on the exh. It's not obvious that the stock 081 heads are better than the 187 LO3 heads due to the flow imbalance -- you can't fully use the int if the exh can't flush the cylinder. That's not to say that the LO3 heads are better. Both LO3 and 081 heads have their flaws in stock form. But you should be able to figure that out by looking over the numbers above.

The iron L98 heads are all better in the int side (they should be -- no swirl ramp) but they are not as good on the exh as compared to the 193 casting.

The aluminum L98 heads (113 casting) are equal to the iron L98 heads on the int, and much better on the exh side, and slightly better than the 193 exh as well. And the 113 castings have a revised exh port shape than the 083s so that explains the exh flow difference. Note: 88+ L98 aluminum heads got the higher-flow D-port, while pre-88 aluminum heads did not.

Now for the ported comparisons, and again I'm showing the peak values for cfm, along with valve data if available in the same script format as above:

305 heads
416 iron head: 220 intake; 161 exh (Kitch, 14014416)
081 iron head: 221 intake; ??? exh (ME Leigh, stock 1.84" diam int valve)
081 iron head: 230 intake; ??? exh (ME Leigh, 1.90" diam int valve)
601 iron heads: 224 intake; 157 exh (Fast305, 1.84/1.50, 14022601, medium duty truck heads)

350 heads
083 iron L98 head: 209 int; 137 exh (dj haf, stock valves) radiused int inlet, open no pipe exh
083 iron L98 head: 200 int; 139 exh (smithtc, stock valves)
083 iron L98 head: 206 int; 144 exh (smithtc, stock valves)
083 iron L98 head: 203 int; 171 exh (smithtc, 2.02/1.60 Manley)
083 iron L98 head: 229 int; 171 exh (rhuarc30, 2.02/1.60)
083 iron L98 head: 241 int; 180 exh (rhuarc30, 2.02/1.60)
083 iron L98 head: 265+ int; 192+ exh (rhuarc31, 2.02/1.60) final version, 271/195 cfm on 190-195 cc runner volume, Manley Proflo

083 iron L98 head: 197 int; 160 exh (CHP)
083 iron L98 head: 248 int; 181 exh (Insomniac92z28, 2.02/1.60)

113 alum L98 head: 210 int; 172 exh (Vizard stock valves, backcut)
113 alum L98 head: 224 int; 177 exh (Vizard, 2.00/1.55 valves)
113 alum L98 head: 220 int; 191 exh (CHP) revised & upgraded casting
113 alum L98 head: 263 int; 206 exh (Lingenfelter CNC ported, big valves)
113 alum L98 head: 243 intake; 192 exh (slightly ported by owner, GMPP pn 12556463)

SP heads
v6 LB4 iron head: 208 intake; 190 exh (HRM) (2.02"/1.60")
193 iron L05 head: 196 int; 183 exh (Dyno Don, stock valves)
193 iron L05 head: 224 int; 216 exh (Fast355, stock size valves, backcut)

The HRM data on the v6 SP heads shows the same trend observed by Dyno Don & Fast355: the exh flows really well after porting (190 cfm up from 116), & the int flows well too (208 cfm up from 138) showing again that the e/i ratio favors the exh. The 270 cid v6 (overbored from 262) engine made 301 fwhp, which would be ~390 fwhp on an equal-spec ported 350.

EDIT: This post describes just how good the factory L98 head castings are now, after 10+ years of tweaking to the casting (backcut valves, smooth radii etc). So the newest 113 casting have nearly no room for porting... although the owner did use sanding rolls before he got them flowed.

FYI, DynoDon's 3rdgen car ran 13.7 @ 101 mph with the ported 193 heads listed above, 1.6 rockers and LT1 cam. It dyno'd at 250 rwhp and 335 rw ftlbs. Prior to the swap, using the unported stock 193 heads, it dynod at 210 rwhp and 330 rw ftlbs, and ran 14.1 at the track (edit: not sure if it had the Fcar LT1 cam during that run or the factory L31 cam which =s the Bcar LT1 cam). All per this thread, and this thread.

Fast355's 1/8th mile runs in his heavy Gvan with his ported 193 heads, extrapolated to a 3500 lb Fcar in a previous post, show an equivalent run in the mid to low 13s. He also measured 279 rwhp. When Fast355 as known as Fast305, he ported 601 heads (305) so I added them for ref.

Among all the info collected here I don't know:

- which heads had back cut valves
- the port volumes
- flow values vs lift

though all are GM factory heads for production vehicles so they all have relatively small port vols. None have large valves (except as noted after porting & head work). The exh flow seems really good on the 193s even with a 1.50" exh valve. And of course all the above data were taken by different people at different times, locations etc. so there is some scatter in the data but the trend is pretty clear. FWIW.

Relevant edits: Stock SP performance and Mopar SP

Fast writes on FSC:

http://www.fullsizechevy.com/forums/...=183103&page=2

From Lo-tec post here, probably using a carb given the intake manifold choice. The carb+manifold solves the breathing/fuel on the induction side (improved over TPI), so the decent ET & trap shows that the heads, even swirl port heads, can't be the problem they were claimed to be. 13.6 @ 101+ (below) is on par with JPrevost's similarly modified 3rdgen. It's not a stretch to think that any head porting done on the LO5 Cad would have dropped the ET and raised the trap speed:

Dewey316's post on dyno and track data on his LO3 TBI car with cam + intake mod, that ran 14.5 @ 94.6 mph and dyno'd 208 rwhp @ 4700 rpm and 272 rw ftlbs @ 3000 rpm :

https://www.thirdgen.org/techbb2/sho...ighlight=swirl

His detailed mod list is:

stock bottom end, stock (unported) heads, stock TB, stock injectors, UltraDyne Cam (206/216 .447 .447 112 on a 106 centerline), Weiand 7525 intake, thru a centerforce clutch, lightweight flywheel, LS1 driveshaft, and 3.42's. Hooker headers, flowmast 3" catback, with a cut-out.

The recurring theme in both above is that, if the LO3 (Dewey) and LO5 (Lo-tec) heads were as bad as many on TGO have said, then the cam+intake+exh swap would not have been able to overcome the lack of adequate flow through the heads. For Dewey, the int + exh fixed the factory restriction to allow the (swapped) cam to make more power than the stock "peanut" cam. The new cam is only slightly warmer than LT1 cam, and 208 rwhp is approx 236 fwhp (12% loss) or 245 fwhp (15% loss) depending on the choice manual trans loss. An Fcar LT1 (350) is 15% larger than a 305, so if you scale Dewey's numbers up by 1.15 you get 239 rwhp which is slightly better rwhp than the stock LT1 Fcars measured, and the torque is close.

A Fiero SP ported head build:
http://mywebpage.netscape.com/fierost4rsc/tst4e.html

Mopar SP

CDP (Chrysler Dodge Plymouth) had swirl port heads, with intake ramp AND heart-shaped combustion chambers, in the '85+ 318 v8. So they had the GM swirl intake port ramp plus the chamber of the later LT1/LT4/L31 heads. Here's HRM's article:

http://www.hotrod.com/howto/113_0304_junk/index1.html

FWIW a 318 that made over 400 fwhp and 408 fw ftlbs using a Comp 268 cam (.480" lift; 224/230 deg duration i/e) stamped factory rockers and the usual exh mods. The heads flowed 215 cfm @ 0.500" lift (intake), up from 135 cfm stock (nearly the same flow #s by HRM on the LB4 v6 test above). The exh numbers were not posted. Scaling the Mopar 318's 400 hp result back to same-mods + unported-heads, 400*(135/215), and scaling from 318 to 305 cid (305/318), you get 241 fwhp.... which is on-par with Dewey316's 305 (above) using a milder cam.

Another Mopar ported 318 test:
http://www.geocities.com/alwest_83/318

F-BIRD'88

Just to clarify: The flow numbers shown for the 083 heads that are shown above as being mine, are not. I got those stock port flow numbers from someone else's forum post on TGO.

The "I got higher numbers" was taken out of context.

I was commenting on flow results of someone elses ported 416 heads.
The posters numbers looked very low for the amount of work done. I questioned the test method. I believe he/or the tester did not use a radius inlet during the test.
I did get higher numbers because my test method was correct. The bench I used gives the numbers you would expect from the different known performance heads we've tried on it. It has even been compared to other benches with the same test head. My data on my ported 416's is accurate and not inflated. The shape and size of the radius inlet on the port is critical. Must be uniform for all comparisons. Industry standard for the radius inlet is 1/2" radius around the port opening. Anything different will give different results. Testing without the radius on the opening will chop off 20 or so cfm @28"

Note: I also tested my ported 416 heads with various intake manifolds attached. That's where the rubber really meets the road.

ShiftyCapone

iTrader: (7)

Great post Kdrolt. I too will soon have data to add to this ongoing discussion. In the meantime I am going to make this a sticky in hopes of consolidating old SP thread debates. This is long overdue and I apologize for my lateness.

Fast355

iTrader: (2)

Just thought I would post a picture of Hot Rod Magazines Ported TBI bowl. Mine are very similar, in fact this is the picture that inspired mine. I took more material out of the walls around the swirl ramp, dug them deeper, and ground down the guide more. This is a 270 cubic inch V6 that made 301 FWHP with only 224/224 @ .050, an edelbrock peformer intake(very low-rise), 600 holley and tiny 1 5/8 x 2 1/2 headers. It also has dished pistons with 9.0:1 compression(that cam could use around 10:1 and be fine.

The engine made 317 ft/lbs at 4,400 RPM and peak HP @ 5,500.



The flow was 208/190.

The rest of the article.
http://hotrod.com/techarticles/engin..._v6/index.html

ShiftyCapone

iTrader: (7)

Fast,

Do you have any pictures of your ported heads? I would like to see a closeup of the work you did on the ramp.

Fast355

iTrader: (2)

Unfortunately I do not at this time. They are on a 1995 Tahoe 350 right now. Should they come off, I will try to pull an intake valve and get a picture. My bowls are nearly identical looking to the Hot Rod ones.

ShiftyCapone

iTrader: (7)

Here are a couple of pictures of the untouched bowls.







These pics are sub par at best.

kevm14

So now that I have headflow data for stock 193s, stock vortecs and ported versions of both, I decided it might be fun to model some stuff.

First, I decided to model the civilian L05, which came in non-9C1 b-bodies (roadmaster, custom cruiser, caprice LTZ). This engine uses the same peanut cam as the L03, and I believe has the same pathetic exhaust. As such, they gained a paltry 10hp over an L03 (180). HP peak rpm went down. Using stock 193 head flow numbers, as well as peanut cam specs (I got the exact cam specs from a Pace parts crate engine page, of all places), I have modeled it next to 3 other cams. There are endless combinations. This first one is with a restrictive exhaust and stock 193 heads. A pretty lousy breathing setup.



The same everything except with an additional 100cfm of intake flow (like a bored out TBI) as well as an opened up exhaust:



Finally, here's swapping the stock 193s for stock L31 Vortec heads:



Even the L05 with the lame cam gained 20hp with Vortec heads. Not that someone should do that swap for 20hp. The Crane 227 cammed version gained 34. It's also interesting to compare the area under the curves for the various setups. I should also note that Vortec heads didn't appear to add meaningful HP until the 4000+ rpm area. I think this confirms what we knew about the SP heads.

I'm not sure what I was going for. Maybe I'll think of something. Or add something. Perhaps this is thought provoking?

Dewey316

Those numbers confirmed what I showed on the dyno also. It seems that the swirl port really starts to hold things back at 4200-4400 RPM. That seems to be shown over and over, to be where they start to hold the motor back

kevm14

Another thing. If my modeling of the L05 is any indication, a 0.78 correction factor to get from DD2000 HP to net flywheel HP should be applied to future simulations. I should model an L03 but I don't have one so it's of less interest to me.

kdrolt

Then explain how power increased in Kevin's first graph. He left the same head parameters in place for each of the three cams used.

Dewey316

That likely has to do with cylender pressure. and timing. The valve events and timing of a huge effect on cyl. filling. If you open and close the valves diffrently, you can acheeve a more complete cyl. fill, it does this because of differing pressure variances.

Notice though, how at about 4400, the vortecs really come alive compared to the swirl ports.

kevm14

That's why variable valve timing, in any form, is highly desirable, especially for an OEM who wants it all.

I don't think anything really works like a brick wall. Though there's that whole mach number thing, and I don't know anything about it or how to calculate it. I'm an EE!

kdrolt

Good answer, and I agree completely. But there was no "holding back" of these three cams at 4200 rpm even when using the flow-limited 193 stock heads. So your statements

are misleading, because power continued to climb.

Dewey316

That cam is not holding back, that is why power climbs. The head is holding back, that is why the vortecs take over at there. The SP heads don't lose power to the vortecs until that point. My SP heads didn't lose ground to the 416's, until that point. Something is holding those motors back, at the same point compared to the other heads, regardless of cam. It could be something to do with resonsese tuning not effecting things the same way, it could be flow limited. If i knew the exact reason as to why the SP heads start giving up power to the others at that point, I would gradly provide it. But, as an observer, I can tell you, that at 4400 RPM's, the SP heads, be it 305 heads, or 350 heads, start giving up power to the Vortecs, and 416's.

Dewey316

I will also add to this discusion, what Vizard has to say about some event timing. He being a MUCH smarter man that myself, sheds some good light on this.

The key there is cyl. pressure diffrences, during certian piston positions. Because the head may have hit its flow limit at one given pressure diffrence, if the valve events give you a greater pressure diffrence, it is possible to make more power, and gain some air-flow, if the cam timing gives you a really good pressure diffrence, over a greater piston location.

This is getting very technical now, but there is great info here. Just pointing out, that the head may be the restriction at 4400rpm, but because of cam event timing, it is still possible to make power beyond that point.

ShiftyCapone

iTrader: (7)

What about when ported? Would be see that RPM branch extend beyond 4200 rpm? Based on Fast's flow results for ported SP's it would suggest that the difference between the two above 4200 RPM isn't as drastic. I would love to see your combo with ported 187's (wink wink) if nothing more than to help those who are on the fence still. I will have ported 187's soon and will have dyno data but that is still months away.

Dewey316

I would also. I'm taking donations. Honestly, doing them for nothing other than the name of science, just doesn't get me into the mood to spend the money and effort.

ShiftyCapone

iTrader: (7)

C'mon dewey! Maybe I can send you my soon to ported 187's?

Dewey316

I found some Vizard info on swirl.

Granted he is talking about mopars here, but the last line in the quote is interesting.

"Creating high swirl numbers alone is not difficult to achieve (shrouding half the valve is one quick way to do it). However, providing high-flow efficiency with adequate swirl is another matter."

Fast355

iTrader: (2)

Good info Dewey. The only thing is that GM didn't shroud half of the valve to do it. They shifted the port to one side of the intake bowl, necked the port down, and forced it up a swirl ramp.

kevm14

I have lately "obtained" Desktop Dyno 2003 and have done more simulations. I also found a Car Craft article where they ported heads. Here's the thing. Fast's ported 193s are about the same as the ported Vortecs. Was theirs the best vortec port job ever? No, in fact it was hardly more than cleanup on the intake side (and valve job), though the exhaust side enjoyed a gain similar to what Fast got out of the 193s (up over 200cfm at higher lifts). Anyway, here are the results. For laughs, I threw in the exact same setup with stock 193 heads. All three are an improvement over this, but the kicker is the ported 193s are within 3hp of the Car Craft vortecs.



I'll be damned if it doesn't look the same. Now assuming Fast didn't drastically increase intake port volume, then these results can probably be taken at face value, no salt needed. How cool is that? This is me rethinking my Vortec conversion ->

PaulD

Last year I pocket ported a set of #906 L31 heads and had them flow tested. I was disappointed with the results compared to stock L31 heads and posted SP figures. I never made the time to swap the heads. I could not be certain whether the results could be attributed to the test operator and equipment or my work. The recent swell of discussion the past year on the SP heads had me contemplating porting them and putting them on so I recently ported one chamber's ports and had the same shop flow an unmodified chamber. Here are the results:

INTAKE

Stock SP #193 . Modded SP modded Vortec

.100 70.7 68.1 55.8

.150 101.7 100 89.2

.200 124 125 123.5

.250 140 144 160

.300 146.5 154.7 186

.350 150.1 164.8 203.8

.400 154.7 171.3 228

.450 158.2 175.4 235

.500 160.4 177.4 228


EXHAUST

.100 47.8 51.7 42.9

.150 70.4 73.1 66.6

.200 85.1 93.7 90.1

.250 97.6 112.3 112.2

.300 112.3 129.7 129

.350 120.5 145 142.6

.400 125 156.3 152.6

.450 129.2 164.6 160.9

.500 129.2 162.5 166.5

The following parameters apply:

1. None of the heads had a three angle seat cut.
2. The L31 and stock 193 head used a single angle cut on the valve.
3. The modded 193 head used a 30 degree back cut on both the intake and exhaust valve.

What's it all mean? First of all, I make no claim to be a professional porter or even a good one, only what an educated amateur can do. It has been a knock against the 906 Vortec head that it does not flow as well as the later 062 casting. Looks like that might be right. I plan on relooking at the 906 exhausts to see what else may be able to be done.
The SP heads flowed very well at low lifts. The intake ports have a convoluted path with the pushrod on one side of the port, then the head bolt hole on the opposite side and severe undercuts below the bowl that were too deep to remove even opening the bowl diameter to 1.75. From .200 and up, the Vortecs flowed better.

Other observations are yours to make.

My apologies for not being able to format the data more clearly. It typed out clearly but I can't seem to get enough space between the columns.

Fast355

iTrader: (2)

PaulD- One more set of flow numbers posted showing the general trend of swirl ports. Modest gains on the intake, moderate gains on the exhaust. Sounds like you did a mild go over on the ports? How much bowl work did you do? How much material did you remove? What did you do to the swirl ramp? What about the ridge left from the cutter about 1/2" down below the intake seat? BTW, backcut valves or aftermarket valves will improve the flow by a substantial amount, especially at the lower lifts. Cutting the seats for 2.00/1.55 or 2.02/1.60 valves would alleviate some of the flaws in these heads as well.

177/162 further goes along with the trend that a single pattern cam may very well be the best way to go with modified swirl ports.

Your flow numbers also further reinforce my old thinking that vortec heads with a stock peanut sized cam are not that much of an upgrade.

Fast355

iTrader: (2)

FWIW, I had to model several engine combinations that I have built using swirl ports by using DD2003.

This is the 240 RWHP 350 TBI truck that I made mention to a long time back. This is the stock 193 numbers from above, a Mellings MTC1 cam, Ultimate TBI mods, Stock intake, and headers.

RPM-------HP-----TQ
2,000----143----376
2,500----180----379
3,000----216----378
3,500----249----373
4,000----270----355
4,500----275----320
5,000----260----273

Now for my little brothers tahoe, 350 TBI crate engine, stock 193s cut for lift, crane roller cam, headers, 454 TBI on a Holley Projection Manifold

http://www.cranecams.com/?show=brows...tType=camshaft

RPM-------HP-----TQ
2,000----133----350
2,500----172----362
3,000----208----365
3,500----249----374
4,000----286----376
4,500----316----368
5,000----326----343
5,500----321----306

This is the one that I built for an Astro, keep in mind it is a 9.8:1 compression, .030" over 4.3, gasket matched and cleaned up V6 193 equivelants (NO Porting just a clean up), crane 2020 cam, edelbrock intake, ultimate TBI mods, shorty style astro van headers.

http://www.cranecams.com/?show=brows...tType=camshaft

RPM------HP-----TQ
2,000----96-----251
2,500----126---264
3,000----158---276
3,500----185---278
4,000----205---269
4,500----219---255
5,000----219---230

This is why I love the idea of the B-Body LT1/Vortec cam and swirl ports, even stock ones. This is a stock 350 short block, ultimate TBI mods, exhaust work with cast-iron manifolds, stock 193s.

RPM------HP-----TQ
2,000----142---373
2,500----177---371
3,000----213---372
3,500----235---352
4,000----242---318
4,500----237---276
5,000----216---227
5,500----185---177

Now take the same engine as above, toss some headers at it, a 454 TBI, Holley Projection intake, and port the heads comparable to even the above ones, keeping the small roller cam.

RPM-------HP-----TQ
2,000----155----406
2,500----191----401
3,000----228----399
3,500----261----392
4,000----285----373
4,500----295----344
5,000----287----301
5,500----262----250

Now you take the above engine, add a 1/4" of stroke, .030" of bore, 9.5:1 compression, stick with the cast-iron manifolds, the stock sized TBI(ultimate TBI mods of course), edelbrock 3704 intake, add 1.6:1 rockers, and you have the engine we put in my dads 1989 TBI suburban. This engine looks lame on paper, but in reality, cruising 70 you are only lightly tipping into the gas and it has a stock converter 700r4/3.08 gear combo with 255/70/R15s.

RPM------HP------TQ
2,000----153----403
2,500----190----399
3,000----224----391
3,500----242----362
4,000----247----324
4,500----235----274
5,000----204----214

Notice how the low-speed torque on all of these simulated engines is enormous. That is what alot of Low-lift flow will do for you. Notice how the stock 193s edge out the ported vortecs in flow up to .200".

PaulD

On the intake, most all the work was done in the bowl. The throat of the bowl was opened to 1.75" and blended into that undercut. Very little was done to the ramp itself except to smooth the top of it. The valve guide was trimmed away on the open side.

On the exhaust side, the throat was cut away to 1.35". The face of valve guide was minimized. On the manifold face, I removed material from the roof and sides of the port to match an exhaust gasket.

kdrolt

Paul,

When Dyno Don ported his 193s he didn't do a lot of porting (timewise) but he did remove the undercut, at least as it appears in the pix here:

https://www.thirdgen.org/techbb2/sho...hreadid=268064

I know that when flow turns a corner, any corner, in a pipe section that an expansion chamber is needed to reduce the pressure drop at the bend. Vizard details this idea in one or more of his books.

On the SP heads, the corner is deeper than it is on a TPI head, for example, but the expansion region still seems to be there. That expansion area is not what you want to have in a length of pipe (the flow region around the valve guide) that has an accompanyng swirl ramp. That might explain what's happening and why Fast355 asked about bowl work and the "undercut region".

So the intake port might have to be opened up beyond 1.75".

Was the exhaust tested with, or without, an extension? I dunno if I asked you that (in email)?

I'm still puzzled that your L31 906 heads don't flow more after porting.

PaulD

Any further is getting into the seat area. 1.75" is only leaving .097 per side for the seat. The undercut is drastic.

Red94Chev

If anyone is interested in flow data for other GM and aftermarket heads, here are some good links:

http://www.dw1977.cz28.com/photo2.html
http://www.chevyhiperformance.com/te...598/index.html

I suggest putting the flow data, including those from the TBI and L98 heads listed above, into a program like Desktop Dyno or Dynosim. You can access a demo copy of the software and look how different heads on the same engine have an effect on hp/torque. The small block demo engine is essentially a 350 engine (non-existant 346 cid). Download at:

http://www.proracingsim.com/proracingsimdemopage.htm

Be sure to install the update file: http://www.proracingsim.com/support.htm

ShiftyCapone

iTrader: (7)

Red,

Welcome to TGO and thank you for the great links!

kdrolt

I stumbled across these threads recently... even though they're 4+ years old.

http://www.sallee-chevrolet.com/Disc...tml?1045725665

http://www.sallee-chevrolet.com/Disc...tml?1049930156

http://www.sallee-chevrolet.com/Disc...tml?1050432892

http://www.sallee-chevrolet.com/Disc...3390/3180.html

http://www.sallee-chevrolet.com/Disc...3418/4522.html

kdrolt

Update to some maximally ported iron TPI 350 heads:

https://www.thirdgen.org/forums/tpi/...d-project.html

kdrolt

Another update on some very expert professionally ported 416 heads:

http://speedtalk.com/forum/viewtopic.php?t=10242

At 0.500" valve lift: 225 cfm intake, 184 cfm exh.

They flowed more at higher, but very impractical, lifts. Went nearly 500 fwhp and 402 fw ftlbs on an engine dyno. These numbers were on the low side as compared to the minimum/normal/maximum spread of power the author cited, suggesting that the BSFC wasn't that great. Said differently, the heads were not that efficient.

kdrolt

And FWIW in the very same thread, the same author (Larry Meaux) cites flow data on a stock 081 casting (305 TPI iron head): at 0.400" lift, 177 cfm intake, 137 cfm exhaust (no pipe), tested with the Y-shape coolant heat riser passage blocked off.

There's a lot of 416 casting info & photos shown, incl F-bird'88 posts.

kdrolt

http://www.pacificp.com/forum/viewto...ghlight=#50340

Then see Savage Sierra's post 2/3rd into the thread.

383 TBI in a 95 C1500 with ported 193 heads; dyno'd at 310 fwhp and 420+ fw ftlbs, in the truck quarter mile in 14.5 sec @ 93 mph.

DM91RS

Ken.....when are you going to do some ported heads?



AND IIRC Tim Burgess runs the 081's with the heat riser filled with "something" and stiill runs a 305 with decent times in the 1/4 mile which equals good power.

FYI...Tim has very good documentation on his mod's with these heads.

Take it easy Ken

DM

kdrolt

I'm doing them now, sort of. They're (187) on the workbench, and have been there collecting dust for over a year. Kids (multiple), wife (one), dog, scouts, work have a habit of slowing my car projects.

The DIY flow bench is also on the list....

DM91RS

LOL..........ok do you need to borrow my grinder and head swivel mounts for the bench?

Oh yeah..........just one wife lol?

comp

did you get started ?

mistahlee

will 305 heads work on a 350? is it a power gain at all?

cosmick

I've personally flowed a washed, high-miles but virgin 416 on a then-new, freshly-calibrated SuperFlow 1020 bench, on a 4" bore, with clay around the intake gasket face. The worst intake port was just over 180 cfm at 28", the best was near 190. Tested to 0.500" maximum. Some of that variance was due to the clay. On the exhaust, they were all between 135-140, with no flow pipe.
I don't believe the 081 exhaust port to be any worse.
I did try the exhaust manifold off a '77 Camaro, made NO difference to the reading. Then again, it was only one exhaust port at a time.

cosmick

You can bolt them on, many have. Just use 350 head gaskets. Power gain? Not unless you have a 7.8:1 350 at high elevation.