Slalom4me

Do we care about intake port size or just that flow is optimal
at each of the valve lift check points when comparing cylinder
heads?

To rephrase the question, can we discuss whether the 166cc-181cc
heads below are as good or better than the higher flowing
191cc, 195cc and larger choices for a small displacement (350),
low rpm (5,500) engine driving an automatic and a 3.07 rear.

0.200". - 0.300". - 0.400". - 0.500".

121/095. 174/134 . 216/159 . 235/177. - 166cc Intake
139/101. 190/121 . 227/140 . 239/147. - 170cc
125/094. 177/123 . 220/144 . 254/155. - 181cc
144/121. 208/157 . 244/188 . 262/202. - 191cc
141/107. 201/143 . 247/175 . 258/190. - 195cc
140/118. 197/153 . 240/183 . 271/200. - 215cc

Am I correct in believing that port volume (and hence
port velocity) is important to low and mid-range response.

If all else is equal, do the 170cc heads offer the optimal
combination of ideal low speed port velocity and total flow
from this particular grouping?

.

SWCDuke

What most guys overlook - probably because they don't have a background in fluid mechanics - is port flow efficiency. This is the ratio of actual flow to "isentropic flow" - the flow that would occur in a "perfect port" using an inviscid fluid with no heat transfer or friction. Such a port is not achieveable in the real world, but it gives us an indication of how good a port flows by expressing flow as a decimal faction or percent of the same size isentropic port.

For example, a production vintage 461 head has flow efficiencies of about .44 on the inlet side and .41 on the exhaust side. Pocket porting will improve these flow efficiencies to about .49/.59 without a significant increase in port size. The CNC ported LS7 heads are about .60/.70, and dedicated race designs, today are in excess of .70 on both sides.

In a street engine we want a modest size port to maintain high velocity at low revs for good fuel distribution and vaporization. Otherwise low end torque and driveabililty/fuel economy may be poor in normal street driving. But if these modest sized ports have good flow efficiency, the engine will make good top end power. If the flow efficiency is poor, top end power will be less.

This is why pocket porting heads improves top end power without having a significant effect on low end torque or driveability/fuel economy, all other things being equal. Pocket porting and multiangle valve seats improve flow efficiency without making the port significantly larger because only a few ccs of material is removed.

Fluid dynamics texts contain the isentropic flow formula, but the Engine Analyzer simulation program computes them for me when I have flow and port dimension data - length and port volume. EA then divides the actual flow by isentropic flow for an equal size port and reports the average flow efficiency over the range of valve lift.

Another trap is to just focus on peak flow at high lift, which is a big mistake. Max valve lift with a lobe of about .300" is only about .43" because the OE rocker arms don't ever achieve a true ratio of 1.5, and the valve spends little time near peak lift. You should consider the flow at all lifts, and focus on the lift at about .2", which is about the average lift over the complete event

Based on your engine/drivetrain configuration you need good low end torque bandwidth. The 170 is only marginally larger than the 166, so average flow velocity will be about the same, but I can tell from inspection that it has better flow efficiency throughout the lift cycle.

Combine the 170s with a low restriction exhaust system and low overlap cam like the OE base 350 cam and the engine should make stump pulling off-idle torque and produce useable power to about 5500 and have excellent driveablility with decent fuel economy.

I've found that with this combination you can retard the OE cam four degrees to achieve better top end power and a few hundred extra useable revs at no expense to low end torque. Even with the cam retard the inlet valve closes relatively early, so DCR is fairly high with a modest static CR, so limit the true compression ratio to about 9.75:1 for good performance on premium unleaded without having to run excessively retard timing at low revs, which will reduce low end torque.

Duke

GOSFAST

I've found that with this combination you can retard the OE cam four degrees to achieve better top end power and a few hundred extra useable revs at no expense to low end torque. Even with the cam retard the inlet valve closes relatively early, so DCR is fairly high with a modest static CR, so limit the true compression ratio to about 9.75:1 for good performance on premium unleaded without having to run excessively retard timing at low revs, which will reduce low end torque.

Duke[/QUOTE]

Hi Duke, better yet just put in a 10.00 nylon timing set, it'll retard itself upstairs and lose nothing downstairs! On the dyno we always see between a 10/20 HP gain on the topside. Thanks, Gary in N.Y.

P.S. Couple of weeks back one of our units in a 3900# '56 Chevy ran Maple Grove, a "blown" 540" BB "street-car" in the neighborhood of 1200 HP on street tires turning 9.50's with a $20.00 timing set turning the "stick"! It's been in there 5 years or more with over 700# springs. This is one of Bill J.'s old "tricks". Still works. The "nylon" serves a dual purpose, like I said it'll retard itself topend AND keep the "harmonics" from the roller lifters. I have them in a bunch of high-end street units here that usually get freshened up pretty regularly.

Double P.S. Jesel recommened not using their setup in this application! Probably a few reasons but mainly "belt-life".

gkull

Out of the above choices I would use the 191 cc head. If this head also uses a FelPro intake gasket 1205 I would use the Weiand stealth dual plane intake.

I'm big on exhaust flow. the 170 above head is minimal E-flow

silver84

does any other car/motorcycle company have?
the insane multiple-choice?

from the catalog, intake port

180cc... bad
195cc...slightly less bad
210cc...better than a turd, but not much
227cc... what everyone else would do

wonderful, we SBC owners get such great choices

Slalom4me

SWCDuke, thank you for some validation of my assumption
and for a great deal of food for thought. GOSFAST, I
hadn't known about the retard inherent in the nylon cam
sprocket. I suppose that the service life would be about
60K mi - far more than I expect to accumulate.

I realized after posting I was inconsistent with Exh
values on the first heads. Also, I found values for
the Performer Corvette heads and added four more
types of heads for comparison.

Here is a revised list, along with the mfrs associated with the numbers.
Most of the numbers come from CHP Head Database. The Performer Corvette,
AFR 180 Eliminator and Trick Flow 23º 175 numbers come from their respective
manufacturers.

0.200". - 0.300". - 0.400". - 0.500".

122/096. 177/124 . 217/147 . 229/166. - 165cc (Edelbrock Performer Corvette #60879 w/60cc 2.02/1.60 valves)
139/105. 190/137 . 227/151 . 239/160. - 170cc (885 Iron Vortec w/ 64cc & 1.94/1.50)
125/094. 177/123 . 220/144 . 254/155. - 181cc (AFR 180 w/ 68cc & 2.02/1.60)
144/121. 208/157 . 244/188 . 262/202. - 191cc (AFR 190 w/ 76cc & 2.02/1.60)
141/107. 201/143 . 247/175 . 258/190. - 195cc (Canfield w/ 67cc & 2.02/1.60)
140/118. 197/153 . 240/183 . 271/200. - 215cc (AFR 210 w/ 67cc & 2.08/1.60


120/096. 160/123 . 186/140 . 196/155. - 163cc (L98 TPI w/58cc & 1.94/1.50)
126/104. 177/138 . 215/160 . 240/180. - 170cc (Edelbrock E-Tec 170 w/ 64cc & 1.94/1.55)
127/109. 180/142 . 219/167 . 242/181. - 175cc (Trick Flow 23º 175 w/ 56cc & 1.94/1.50)
129/108. 195/156 . 240/178 . 255/190. - 180cc (AFR 180 Eliminator w/68cc & 2.02/1.60)


Further about the usage. This is a dual-purpose car with the
weighting somewhat more toward the track side than the street
side of the equation. By track, this means 'AutoX' events consisting
of a single pass on an open, fast 1.7 mi layout or six laps on a
2.0 mi road course.

On the 1.7 mi layout, logs of several runs show that avg RPM
is 1850-2050. From 4900 in 2nd, RPM drops to 3300 in 3rd.
Just before braking on the two fast straights, RPM is 4050-4200.
Max RPM recorded is 5400-5650 (in two spots I hold a gear rather than shift.)

My present aim is to make the RPM logs climb more steeply between
2200 and 5000. Especially between 3300 and 4200 while in 3rd.

The engine is essentially stock. It retains the untouched TPI
intake and has 1-5/8" long tube headers into an OEM exhaust.
I will be opening it up to address signs of coolant leaking
from the head gaskets into the oil.

To complement head work, I will be changing the intake system
and valvetrain.

.

Slalom4me

A consideration in mind is the limitation imposed by the 700R4 and the
D36. I do not know what the ceiling is but there is a point beyond
which torque really begins to shorten part life. I imagine the aim
is to keep the curve below this point but flatten & extend the curve
to extend torque over more RPM?

How much torque is enough? I do not have numbers on my car but for
reference, here is a dyno-sheet posted by 88BlackZ51 for his car
with these mods: Hooker Longtubes, Y-pipe (#2149 & #16720), Flowmaster
Force II Catback System (2.25 inch), Open Air Lid with K&N Fliter and
Random Tech High flow.



As for heads, currently my selections in order of preference are:

122/096. 177/124 . 217/147 . 229/166. - 165cc (Edelbrock Performer Corvette #60879 w/60cc 2.02/1.60 valves)
126/104. 177/138 . 215/160 . 240/180. - 170cc (Edelbrock E-Tec 170 w/ 64cc & 1.94/1.55)
129/108. 195/156 . 240/178 . 255/190. - 180cc (AFR 180 Eliminator w/68cc & 2.02/1.60)
139/105. 190/137 . 227/151 . 239/160. - 170cc (885 Iron Vortec w/ 64cc & 1.94/1.50)

From the big picture perspective (net result, availability, initial cost,
additional work), the 60879 Performer Corvette heads appear like a
worthy choice. Small port, small chamber, angle plugs, better-than-OEM
flow across the spectrum, aluminum, bolt-on fitment.

Next is the E-Tek 170. Larger port, better Exh values throughout (and
Int values improve at higher lifts), but needs a Vortec-shaped intake
and straight plugs may interfere with primaries. 64cc chamber could be
in keeping with 9.75:1 compression suggested by SWCDuke and can be
compensated with a cam selection that provides additional DCR.

Third is the AFR 180 Eliminator. Larger port, but better flow on
both Int/Exh, angle plugs, is 68cc possible to compensate or should
these be flycut for lower chamber volume. What kind of availability
is there for this new release and if work is done by AFR, how long
will it take?

Fourth is the 885 Iron Vortec. All the positives mentioned by SWCDuke
but the iron adds 40 lbs/pr and the straight plugs may interfere with
the headers.

Looking at my big picture (net result, availability, initial cost,
additional work) and taking into account the effect of torque on
drivetrain life, are these choices prioritized reasonably or
do those with larger ports in the group deserve a second look?

Does having work done on the heads change the outcome?
Could professional bowl/port work, say, on the #60879 heads
bring them up a notch?

.

gkull

Your 700 can be built to take on 800-850 HP if you want to.

I have AFR 210's and had them flat mill them to 64 cc to keep my 383 at 11 ish static compression and it runs fine on 91 octane. Because the cam keeps the DCR to 8.3 or 8.4

Hot rodded 355 ci motors really run well up to about 210 cc and single planes. The head cc is just a small part of the equation. It's actually the total dead air space of the intake port and whether the cam is also causing reversion.

So you can put a hot cam with small ports and it will run worse that a big port and cam timing that is correct for the cubic inch and compression.

Slalom4me

I anticipate using an intake with total runner lengths of between 21"-13"
(inc 6" in the head). The Super Ram at the long end, a modified
Stealth Ram at the short end or one of some choices I am considering
between these.

As for the drivetrain, the thinking is to live within relatively stock
load capability, just stretching the engine's ability to produce these
loads out over a much broader RPM range. In another place and
time, I would have chosen increased, detuned displacement to get
hp/tq down low that carried up across the targeted operating range.
If building from scratch now was on the agenda, I would be using
light parts in the rotating assembly for acceleration gains from
reduced inertia.
.

Slalom4me

An OEM 700R4 can live for quite a while behind 300-350 lbs/ft.

If the torque curve on the dyno runs above could be flattened to
reach and hold 300+ lbs ft through to 4800-5000, this would translate
into 310 CHP at 5000. Unreasonable?

Using HP = (TQ * RPM)/5252

Then for Torque = 325 lb/ft

RPM . HP
2000 123.8
2500 154.7
3000 185.6
3500 216.6
4000 247.5
4500 278.5
5000 309.4
5500 340.3


In sticking to the smallest port size within the group, am I only
raising torque at the low end of RPM and still facing having it
fall off above 4000? If so, then I'd appear to be be better off
looking at some of the larger offerings?

By example, GM offers a crate engine that produces 400+ lbs/ft
from 2500 through to 5000, peaking with 435 lbs ft @ 4000. Peak
HP is 340 at 4500. This package has its power in the operating range
I use. However, it would require an upgraded 700R4 in order to remain
durable behind this power.

.

0Tony Mamo @ AFR

The best running combinations in my experience are always high flowing heads with conservative port volumes. I have never ONCE seen that combination fail, yet have seen big port heads with big flow numbers (claimed at least) fall short at lot more than once.

Airspeed is as key a component to power and TQ as is total flow....having alot of both is the homerun scenario. Our new Eliminator 23' heads will have similar port volumes to our former product but significantly more flow at practically every lift point which obviously increases the velocity of the charge because you have more air moving thru the same size cross-section (which isn't an easy task to accomplish if your starting with a good piece already).

We just finished our first dyno test of the new street 195 Eliminator($1400 retail)....you will see the results in an upcoming Chevy Mag. Here is a quick rundown of the components we used:

383 CID "budget" shortblock, cast crank, hypereutectic pistons, etc. (I think it was a Speedomotive kit but I could be wrong).
10.8 CR (91 octane all day long)
1.75 headers
240/246 Flat tappet hydraulic cam (this particular story is aimed at making big power with a conservative outlay of $$$).
Vic Jr that I lightly cleaned the plenum and port matched
750 Demon Carb

How about 520 HP at 6200 RPM....481 TQ @ 5200 and the engine was still making 490 HP @ 7000 RPM. We were extremely pleased....I drove to the dyno facility with the heads thinking if I leave with 500 HP that would be pretty awesome all things considered.

That head flows 280 CFM @ .500 lift with stong low and midlift flow and a killer exhaust port as well (its actually stronger on the exhaust side than we will probably advertise....that head went around 220 @ .500 lift!).

Huge numbers for a reasonably priced street head (100% CNC ported) that competes in price with alot of our competitors "as cast" stuff.

ALOT more good stuff on the way but this is one of the first tests that points to the fact our new Eliminator heads are going to perform as well if not better than we had hoped.

Thanks Guys...

Tony

CORKVETTE1

now put that engine in a car and see what it will run most of the mags engines do not perform very well at the track