Stock L31 Intake flow numbers, CR & Best heads ? AFR's or EDELBROCK?

[Calderone]

Not trying to beat a dead horse but we are close to upgrade our ´96 Yukon.
i've been trying to find out the best combo for the Yukon but everytime some new details comes into mind
and might change the plans a bit. The upgrade is a fact. I've done a great upgrade on my L98 87 vette
with a 219 LPE cam, SuperRam intake and base, AFR195 heads, 3200 vigilante, 3.45 Dana 44 and much more.
Once you are bitten by the performance bug i cannot leave the Yukon alone.

Now this are the facts and doubts :

- What's the stock '96 L31 Compression ratio? thinking on using 0.026" compressed inch head gaskets to bump the compression a bit
- Will this Compression Ratio good for the LT4 Cam?
Not sure what will be the CR with this heads
- Im between AFR0912's 190cc or Edelbrock 60975 170cc E-tecs (we won't be using the stock heads anymore)
AFR has bigger valves but might be overkill with the stock intake and 19lb poppets. Is it worth to swap heads with this alum versions?

We will add a VMax spacer later for more volume on the intake..

All of this will be coupled with a Vigilante 10.5 3600 stalll and 1 5/8 Long tube headers and 1.6 Roller Rockers , we have 3.42 gears.

Any of you running this heads with the LT4 Hotcam
need to find out pushrod length as well

Thanks !

 

[autolover3]

Found this a while back while doing some stuff to my yukon. From thirdgen.com i think.

I have checked several engines of the engines I have personally pulled apart. Here is a quick run-down.

1997 L31 Vortec Stock G1500 Van engine (Hydraulic Locked on #2)

Piston Dish is = 12cc total (same exact piston as a Light Duty TBI 350)
Head = 64 cc.
Piston was .026" in the hole
Head gasket was a .028" compressed composite gasket.
Calculated = 9.2:1
Advertised = 9.4:1

Stock GM Goodwrench HD TBI replacement engine

Piston Dish = 18cc total (Same piston as Scyclone/Typhoon FWIW)
Head = 65.3cc
Piston was .025" in the hole
Head gasket was a .028" compressed composite gasket.
Calculated = 8.6:1
Advertised = 8.75:1

Stock 1992 LD TBI 350

Piston dish = 12cc total (Same piston as L31)
Head = 65cc
Piston = .027" in the hole
Head gasket was .028" compressed composite.
Calculated = 9.1:1
Advertised = 9.3:1

Stock 1983 LE9 305 4bbl (The highest compression conventional smallblock GM truck engine I have pulled apart, I almost wonder if the pistons were a factory mistake as others I have seen had deep trough dishes like the early LG4s but this engine was 100% original in every way, unless it had the engine replaced prior to 100 miles).

Piston = Flat-top with 6cc worth of eybrow reliefs
Head = 53cc
Piston - .025" in the hole
Head gasket was a .016" compressed steel shim
Calculated = 10.4:1
Advertised = 9.2:1

Just what I have found through measurements I have carefully taken.

---------- Post added at 10:41 PM ---------- Previous post was at 10:37 PM ----------

I would suggest not getting different heads unless you want aluminum. Could do the 2.02 and 1.6 valves in stock heads with a bowl blend and polish runners. If going to spend all the money for the intake spacer why not go for the marine intake swap. Than go with bigger injectors etc and better flow so you won't be limiting heads.

Pushrod length will need to be found out on your own. Get an adjustable pushrod and follow these guidelines http://www.lunatipower.com/Tech/Valvetrain/HowToVerifyValvetrainGeometry.aspx

 

[Lotshp]

Good call Kolton, yeah pushrod length checker is a must for proper valve train geometry. If it's a street truck run the AFR 180 eliminators with a mild .525 lift cam and a smaller converter then your choice, you will not be disappointed.

 

[Calderone]

Thank you Lotshp, cannot find the 180's in Vortec configuration.
190cc SBC "Eliminator" Vortec 23° Street Head is the only one available.

 

[Lotshp]

I believe the part#0912 is the vortec 180 heads and the 190 for some reason, maybe the newer version is the 190cc with the same part# but I think you can still get the 180cc,treperformance sells them still I believe. You should call AFR directly to see what they have. The 190's are some serious flowing heads for the sbc, but in my humble opinion if you can still get the 180's they would be better suited for your application.