113 chamber volume prob

[chaparral2f]

I have a set of D port aluminium L-98 heads that I am going to run on a mild 350. When I cc'd them I came up with a huge difference in the chamber volumes. From the largest to the smallest is a difference of 3ccs. How can I remove that much material without hitting water or getting beyond the edge of rhe head gasket. I've searched and still have no idea what to do. Any help would be really appreciated.
Thanks,
Joe

 

[87vette81big]

I believe that amount of CC Variation is normal in production GM SBC cylinder heads.

When I CC hecked my factory Pontiac cylinder heads of different casting #'s made from 1964 to 1979, combustion chamber volume never varied more than .2CC from one chamber to another on the same cylinder head.
I own a 100 CC glass Burette.
All Pontiac V8's made from 1955 to 1979 had fully machined combustion chambers. Unique Pontiac V8 design parameter.

See what Grumpy has to say about your 113 heads.
Most would polish chambers & use as is I believe.

 

[grumpyvette]

you might be amazed at the difference I see in combustion chamber volume I see on O.E.M. factory heads, the better aftermarket heads tend to be much closer in volume, but you have choices to make,
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 guide plates. The heads also have angled spark plug locations, and no provision for EGR or an intake manifold heat riser.
now the aluminum small block L98 heads generally came with 58 cc combustion chambers so 113cc sounds more like a BIG BLOCK CYLINDER HEAD COMBUSTION CHAMBER SIZE??
you can remove enough chamber volume on most heads by polishing the surface and DE-shrouding the valves to let you match the combustion chambers in the smaller combustion chambers to match the larger ones chamber volume, OR you might also consider a bit of TIG welding to take up some of the larger combustion chamber volume, if you want to decrease the larger chamber volumes.
BTW, When a head gasket thickness is listed its supposed to be the compressed gasket thickness
keep in mind it assumes you use the factory heads with the matched factory head bolts torqued to the factory suggested torque settings

polishing the combustion chambers and smoothing contours tends to reduce detonation and improve power

you can add a bit of chamber volume and reduce the potential hot spots that help cause detonation by opening and blending and smoothing the combustion chamber

THESE LINKS HAVE A GREAT DEAL MORE RELATED INFO

viewtopic.php?f=52&t=2630&p=6788&hilit=shrouding#p6788

viewtopic.php?f=53&t=4390&p=11552&hilit=polish+chamber#p11552

viewtopic.php?f=52&t=4715&p=12810&hilit=shroud#p12810

viewtopic.php?f=50&t=4618&p=13240#p13240

 

[87vette81big]

I think he was referring to the last 3 part numbers of the TPI L-98 heads he is working with.

113 is the 1988 to 1991 Corvette aluminum L98 heads.

128 is the 1987 Corvette L98 aluminum heads.
I can see the 128 casting number with the oil fill cap removed on my 1987 Corvette Vert.

I forget what the 1986 Corvette L98 aluminum head casting number was, may have #128's also.
The aluminum 1986 L98 Corvette heads were only used on the newly released C4 Convertible or as some call the 1986 Corvette convertible pace car.
All 1986 Corvettes were supposed to have aluminum cylinder heads but had a problem with cracking. Castings were revised & made thicker.
Time the updated heads were ready, decision was made to use them only on the 1986 Corvette convertibles that came out mid year 1986.