are the stock aluminum corvette L98 heads any good?



are the stock aluminum corvette L98 heads any good?

Postby grumpyvette » September 28th, 2011, 9:20 am

most of us want to save money and theres almost always some guy selling used " C4 ALUMINUM CORVETTE HEADS" at a good price so I get asked if thats a good performance upgrade as they are usually far less expensive than new aftermarket heads,those used aluminum corvette heads can usually be found for well under $400 a set, making them appear to be a bargain.
short answer? the stock, un-ported aluminum L98 heads flow about 200cfm and even stock iron VORTEC HEADS easily out perform them,as the stock 170cc production versions flow about 228cfm un touched
If you have them they save about 50 LBS on the front of the car, thats good and aluminum heads are easier to repair if damaged , but they do not provide a significant air flow advantage or power increase over the iron heads they replaced,
the basic bottom line here is that the stock L98 aluminum heads flow about 200cfm while even vortec heads flow about 230cfm and thats a significant difference, yet even vortec head are restrictive if your looking to exceed about 430hp, good aftermarket aluminum heads with 215cc or larger ports from AFR,BRODIX,TRICKFLOW,DART can easily flow 270-300cfm, making the corvette heads a lost cause in an all out horse power race.


read these threads and sub links

viewtopic.php?f=69&t=519

viewtopic.php?f=52&t=5537

viewtopic.php?f=52&t=5364&p=16066&hilit=head+flow+numbers#p16066

viewtopic.php?f=52&t=1563&p=11967&hilit=flow+numbers#p11967

viewtopic.php?f=52&t=4221&p=11119&hilit=flow+numbers#p11119

viewtopic.php?f=55&t=624&p=11125&hilit=flow+numbers#p11125

viewtopic.php?f=52&t=322&p=9895&hilit=flow+numbers#p9895

viewtopic.php?f=52&t=92&p=7882&hilit=flow+numbers#p7882

viewtopic.php?f=52&t=5078

http://www.carcraft.com/techarticles/cc ... ewall.html


HERES SOME INFO
In mid-1986, GM converted the corvette over to aluminum heads, casting '128. (Saving about 40lbs off the front end compared to the old '624 Iron heads.)This continued throughout the 1987 model year. In '88, they revised the exhaust port design, raising it 0.100" and it was shaped into a "D", thus they are called D-ports. There are other differences in the two heads also, in that the 128 heads were fitted with an exhaust valve rotator. To accomodate this, the valve spring seat was lowered approximately 0.125" or so. Therefore to delete the heavy exhaust valve rotator on the 128's, you need to shim the spring accordingly to achieve the correct spring installed height.

Usually when you see "L98 vette" heads listed on some site, this '113 head is what they are talking about. ZZ4 and H.O. 350 heads are the same, but with different springs.

Note: I have 'heard' that the last 250 units of the 87 model year came with the '113 head, from the factory.

'128s should be good for 300-325ish, whereas the '113s should support up to 350.

Intake runner-163cc
Combustion Chamber size for '113-58cc
Valves-1.94/1.5
Plug-L98 angle, this is a GM angle, not every angled-plug head offered in aftermarket is this angle. You must check on what is being sold, as not all headers fit different angled plug heads.

Stock exhaust port dimension for '113 D-ports:
1.55" horizontal dimension (flat part of the D)
1.475" vertical dimension (total port height)
0.775" radius along the upper port surface
5.38" perimeter length (requires 1.75" header pipe without stretching)


Here are some intake flow numbers for #113 heads from TPIS "Insider Hints":
Lift......Stock......Ported
.100"......62...........68
.200".....116.........149
.300".....161.........193
.400".....185.........211
.500".....195.........211
.600".....198.........211
Note that the "Ported" numbers were with 1.940" intake valves.

These flow #'s are from fully ported '113 heads:
The flow numbers are with 2.02/1.57 valves and the figures are from the one doing the work.

I have not had them verified by any other source:

.1000 86.9
.2000 144.1
.3000 179.3
.4000 215.2
.5000 231.0
.5500 232.3
.6000 242.3
.6500 243.0



The only data I have on '128 flow was posted on the forum years ago:
Intake - 199 cfm @ 0.500" @ 28" H2O
Exhaust - 110 cfm @ 0.500" @ 28" H2O

You may also find data on the Cylinder Heads links on my main page.

The 84-86E head is casting #462624 (PN #464045)
161/62 int/exh port in cc
2.02/1.6 valves
76cc combustion chamber
Plug-straight

It is an identical casting to the '492 head, except that the '492 has a smaller chamber. '492 is itself a replacement for 461, 462, and 186.

They both have a heat-riser passage for fast warm-ups.




keep in mind swapping heads gives you the option to increase or decrease the compression ratio of the combo, and once the compression ratios increased you can use a longer duration cam timing without sacrificing a great deal of low rpm torque, that you would loose with the lower compression ratio if the same cam were installed in the lower compression ratio combo

"(assume on a stock 350 small block)

Speaking in generalities and assuming no other changes, what's the relation between cylinder head combustion chamber size and overall engine compression?

Does just changing heads from a stock 76cc head, to a head with a smaller chamber make that much overall difference on engine c/ratio? Such as a 64cc or 58cc chamber. How about changes on necessary octane requirement?

Just curious to see what can be expected. I've read plenty on what performance gains can be had and what would work best for 350 TPI, but curious to see the other factors may play out.

Thanks"

Ok lets look at it a bit, theres two types of compression ratio, static and dynamic, keep in mind its MOSTLY dynamic compression ratio, that effects your results.
youll gain about 3% in hp increasing the effective static compression ratio one full point, so swapping from a 9:1 to a 10:1 cpr boost torque about 3%
swapping from a 76cc head to a 58cc head is a 1.84:1 cpr change so you can reasonably expect a 1.84 x 3% or a 5.52% boost in torque from that change alone.
if your current engine made 330hp that would jump to about 5.52% higher if the tq curve remained consistant, so youll see about 350 hp.


one of the the main functions of compression is to pack the fuel/air mix into a tight area for both fast effective ignition and to provide a mechanical advantage for the piston & rod assembly to push against the crank throw,as that mass in the combustion chamber burns and rapidly expands.

lets look at your question, given identical 350 displacement engines with flat top pistons and a common .032 thick head gasket, a .023 deck and 5cc valve notches, heres what your going to see in STATIC COMPRESSION,as a result of combustion chamber changes

58cc=10.61/1
60cc=10.36/1
62cc=10.12/1
64cc=9.89/1
68cc=9.47/1
72cc=9.09/1
74cc=8.91/1
76cc=8.75/1

keep in mind you want to stay at about 8:1-8.5:1 in DYNAMIC compression

to run common pump gas without getting into detonation
that depends on the fuel octane, cylinder head temp. and several other variables but generally 8.0-8.5:1 dynamic works out well if your going to run mid grade pump gas

Image

calculators


http://kb-silvolite.com/calc.php?action=comp

http://www.csgnetwork.com/compcalc.html

http://www.bgsoflex.com/cr.html



threads/info

viewtopic.php?f=52&t=266&p=40004&hilit=215cc+vortec#p40004

http://victorylibrary.com/mopar/chamber-tech-c.htm

http://victorylibrary.com/mopar/piston_position-c.htm

http://victorylibrary.com/mopar/cam-tech-c.htm

viewtopic.php?f=44&t=38

viewtopic.php?f=52&t=5078

viewtopic.php?f=52&t=796

viewtopic.php?f=52&t=148

viewtopic.php?f=52&t=4906

viewtopic.php?f=52&t=2203

viewtopic.php?f=52&t=389

viewtopic.php?f=50&t=10728

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=727

http://forum.grumpysperformance.com/viewtopic.php?f=50&t=499
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: are the stock aluminum corvette L98 heads any good?

Postby grumpyvette » September 30th, 2011, 12:45 pm

Image
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http://www.popularhotrodding.com/engine ... ewall.html
Image
you might want to read thru this carefully,its an interesting build that gives a good deal of info if you read carefully, they build a 447hp 350 with vortec heads for under $4K
matching components to the application is critical and they do a better than average job in this build.
if you notice the power curve youll see that torque peaks at about 4700rpm with that 350 displacement,
Image
if youve been paying attention in the threads discussing head flow and power thats a good indication that the ports about maxed out at 4700rpm on a 350 displacement with those vortec heads
Image
if youve been reading the cam related threads you can see, why a cam in the 230-240 duration range is about the absolute max duration that will provide decent results with a set of vortec heads,and that the blue bar on the chart for the 220-230 duration is almost perfectly matching the head flow rate restiction level, simply because adding duration past that 230-335 cam duration range effectively moves the power curve up above the rpm range a vortec head easily supports, they select a 224 duration cam on a tight 108 LSA to maximize mid rpm torque to complement the vortec heads characteristic of great low and mid rpm flow, but realizing above about 5000rpm your not filling the cylinder effectively.
Image
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NEWER vortec heads require different valve covers that the traditional first gen SBC but there are adapters available to sallow their use, but they cost almost as much or more than many valve covers themselves
Image
http://www.jegs.com/i/JEGS+Performance+ ... 0/10002/-1

viewtopic.php?f=52&t=5321&p=16006&hilit=volumetric#p16006

just a bit of math, if a 350 displacement maxes out the head flow at about 4700rpm, and lets say we want to build a 383?
4700 x 350 /383=4300rpm so you could expect the same combo to max those same vortecs head flow at about 4300rpm in as similar 383sbc combo
or put a different way a 350 is 91% as large as a 383 so a 383 will match a 350 engines port flow rates at about 91% of the same rpm as the 350 ie 4700rpm x .91=4300rpm

Aluminum does have advantages, like light weight, and easy of machining compared to cast iron, example,cracks in valve seats on iron heads ",usually the result of overheating,"tend to result in coolant leaks that are not easily repaired, so you need a new cylinder head even if you had hundreds of dollars in port work done previously.
but on aluminum heads a bit of tig welding and machining for new valve seats repairs the heads rather easily

Image
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: are the stock aluminum corvette L98 heads any good?

Postby grumpyvette » June 17th, 2012, 12:27 pm

http://www.trickflow.com/articles/dynod ... _heads.asp

HERES POSTED FLOW NUMBERS FROM SEVERAL SOURCES FOR BOTH THE CAMARO IRON HEADS AND VETTES ALUMINUM HEADS

083 iron L98 head: 185 cfm intake; 106 cfm exh
083 iron L98 head: 194 cfm intake; 118 cfm exh
083 iron L98 head: 202 cfm intake; 141 cfm exh

113 alum L98 head: 199 cfm intake; 149 cfm exh
113 alum L98 head: 182 cfm intake; 145 cfm exh
113 alum L98 head: 193 cfm intake; 162 cfm exh


ID STRONGLY ADVISE READING THESE THREADS ALSO

viewtopic.php?f=44&t=2099&p=17024&hilit=fuelie+heads#p17024

viewtopic.php?f=52&t=401&p=6078&hilit=machining+vortec#p6078

viewtopic.php?f=52&t=796&p=1156&hilit=dart+vortec#p1156

viewtopic.php?f=55&t=624&p=835&hilit=dart+vortec#p835

viewtopic.php?f=52&t=5078&p=14433&hilit=215cc+vortec#p14433

viewtopic.php?f=69&t=1040&p=1943&hilit=215cc+vortec#p1943

viewtopic.php?f=55&t=1509&p=10092&hilit=210cc#p10092

viewtopic.php?f=50&t=1249&p=3752&hilit=210cc#p3752

viewtopic.php?f=69&t=7028&p=23278&hilit=210cc#p23278

viewtopic.php?f=52&t=8596&p=30222#p30222

http://www.chevyhiperformance.com/techa ... ewall.html

WATCH VIDEO
https://www.youtube.com/watch?annotatio ... v3ZkqZiMjI

23 Degree Heads VS. L98 Heads

Trick Flow's 23 Degree Chevy Head vs. the Corvette L98


23 Degree Chevy Head

The 23 Degree Street head uses a conventional 23 degree valve angle, making it a direct, emissions-legal swap for 1995 and earlier non-LT1 Chevy heads, has factory valvetrain geometry, and uses standard small block components.

The 23 Degree head features 64cc combustion chambers, 2.02"/1.60" stainless steel valves, bronze valve guides, and 3/8" screw-in rocker arm studs. The intake ports are 195cc and have a high velocity, small cross-section design that provides excellent low-end torque and high rpm power. You also get a choice of valve springs. The standard spring is a 1.25" single, as used on the heads we tested. They're good for cams up to .520" lift. The next step up is a 1.47" single spring, designed for cams up to .540" lift. And for the more radical cams up to .600" lift, the 23 Degree heads are available with 1.46" dual valve springs.

Image


The Trick Flow 23 Degree Street head uses a conventional 23 degree valve angle, making it a direct replacement for 1995 and earlier, non-LT1 Chevy heads. The head features high velocity 195cc intake runners, 3/8" screw-in rocker arm studs, and bronze valve guides. Trick Flow also offers three valve spring choices: 1.25" single for cams up to .520" lift, 1.47" single for cams up to .540" lift, and 1.46" double for cams up to .600" lift.

This is where the 23 Degree heads really outshine the GM Performance L98s. The 2.02"/1.60" valves are a step above the L98's 1.94/1.50" valves, which means the Trick Flow heads can flow more power-building air. The 23 Degree's 64cc combustion chambers are larger than the L98's 58cc chambers, and thus yield less compression. Our 383 test engine had 10.1:1 compression with the Trick Flow heads, and 10.8:1 with the L98s. The extra squeeze gives the L98s a small torque advantage at lower rpms.

L98 Heads

The L98 aluminum head first appeared on the 1986 TPI Corvette, and was used up until the LT1 motors were introduced in 1993. Trick Flow used brand new GM Performance heads for the dyno test. The GM heads feature the same basic design elements of the production L98-58cc combustion chambers, 1.94"/1.50" valves, high-velocity 163cc intake runners for good throttle response, and D-shaped exhaust ports for better flow -- and come assembled with heavy duty 1.27" chrome silicon valve springs, 3/8" screw-in rocker arm studs, and guideplates. The heads also have angled spark plug locations, and no provision for EGR or an intake manifold
heat riser.

Image



Instead of using a set of tired old L98 heads out of a boneyard, Trick Flow went with brand new heads from GM Performance. The GM heads have 58cc combustion chambers, high velocity 163cc intake runners, and D-shaped exhaust ports like the production L98, but are updated with 1.27" chrome silicon valve springs and 3/8" screw-in rocker arm studs. The exhaust ports are also raised .100" from the stock location, which may require opening up the exhaust manifolds or headers to achieve optimum flow.

The 58cc chambers in the GM Performance heads have 1.94" intake and 1.50" exhaust valves. While those are fine for building low and mid-rpm power (especially torque), they cannot flow enough to sustain power production above 4,000-4,500 rpm.


BTW its VERY easy to pick up 50-60 flw hp on a 1985-86 corvette 350 sbc by swapping to the trickflow 195cc heads, that seriously out perform vortec heads, in most applications, and then add a crane 114132 hydraulic flat tappet cam with 1.6:1 roller rockers.
if you additionally add ,boosting the compression ratio and stroking the displacement to 383 and porting the intake, and reaching 70-80 flw hp over stock power level is very easy

Image


RELATED INFO
viewtopic.php?f=69&t=519
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: are the stock aluminum corvette L98 heads any good?

Postby grumpyvette » January 19th, 2013, 10:22 am

Are the AFR 180cc or 195cc Eliminator Heads a good replacement for the small valve 'fuelie' heads on a 327 or 350 sbc
engine that will be used mostly for transportation but Im wanting a bit better performance
?

What improvements in hp and torque would be expected?


A VIDEO DART VS 882 chevy heads TO WATCH
http://www.youtube.com/watch?annotation ... v3ZkqZiMjI

http://www.carcraft.com/techarticles/11 ... rison.html

anyone who tells you that upgrading to the better aftermarket 180cc or even the 195cc afr heads is not going to be a huge improvement over the vortec . L98 or old fuelie heads just has never had the opportunity to drive the same car after making the swap to the better flow rate, cylinder heads, especially if you add a cam ,that allows those heads to breath effectively,with a bit more lift and duration than the stock cam.
even with a stock cam you feel the power improve's but give the engine a bit more cam and decent headers so the engine can use the extra air flow potential,and it really wakes up.
all these smaller port heads tend to respond well to dual plane intakes like the EDELBROCK AIR GAP, or WIEAND AIR STRIKE and a cam and rear gear combo that matches the usually intended 1500rpm-6000rpm power band.
you need to understand exactly what your goals are and what your starting with, read the linked info and call at least 5 cam manufacturers before selecting a cam.


http://www.summitracing.com/parts/edl-3817
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If your thinking of swapping to vortec heads on a TPI engine,as a cost effective upgrade,(which provide a noticeable improvement in air flow rates) edelbrock makes a vortec tpi base manifold, which is mandatory on a TPI if you swap to vortec heads
Image
vortec heads significantly out flow L98 stock heads the difference is an easy 30 hp or more in potential, when matched with a cam that allows the heads to breath, the best direct replacement cam to work with vortec heads and a tpi base combo Ive found in a flat tappet hydraulic cam for the earlier TPI engines is the CRANE 114132 cam, and despite what the cam info says it works ok on a stock 350 with an auto trans and the stock rear gears , but it helps to have an adjustable fuel pressure regulator set to 38-40 psi and headers ,with a low restriction exhaust won,t hurt either, just be aware theres other effective options, do some research then make intelligent choices, based on your goal and budget

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READ THE LINKS CAREFULLY


viewtopic.php?f=44&t=6175&p=19304&hilit=machining+vortec#p19304

http://www.highperformancepontiac.com/t ... ck_engine/

http://www.superchevy.com/how-to/engine ... -manifold/

READ THRU THESE LINKS AND SUB LINKS

viewtopic.php?f=69&t=519

viewtopic.php?f=55&t=58&p=13183#p13183

viewtopic.php?f=52&t=333

http://www.strokerengine.com/SBCHeadsFlow.html

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=3802

viewtopic.php?f=52&t=82

viewtopic.php?f=52&t=1070

viewtopic.php?f=52&t=5078

http://airflowresearch.com/articles/article115/A-P1.htm

http://airflowresearch.com/articles/article040/A-P1.htm

http://airflowresearch.com/articles/article054/A-P1.htm

http://airflowresearch.com/articles/article032/A-P1.htm
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Posts: 14105
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