TierAngst

Was planning on going with vortec heads then suddenly realized that it'll put my compression at something like 10.5:1 waaay more than I want. So now I'm thinking of going with the world product heads with the stock size chamber (76cc) but I don't know which ones to buy. The part numbers (from summitracing) for the closest I can come to a match are:
WRL-043600-1
WRL-042670-1
WRL-042770-1
WRL-043640-1
WRL-043640-2
WRL-043600-2

Which should I get?

Fast355

iTrader: (2)

The stock chamber size is just over 64 cc with 193s!

kdrolt

I've heard both 76 cc and 64 cc on the 350 swirl port heads.... but I've also not seen people carefully check to see what the casting number was (193 or 191 casting suffix, 350 heads), whether the pistons were dished, and whether the vehicle was a car or a truck.... and then post all that info together.

It would have been easier and cheaper for the factory/foundry to make a single chamber size (64 cc) on both the 191 and 193 castings for use in both cars & trucks, and then to use dished pistons to drop the CR on the trucks. But I've never been able to confirm that.

Fast355

iTrader: (2)

Well EVERY 193 that I have run across comes in at about 65 cc, stock from GM.

kdrolt

Which would lend credence to the cost-cutting practice of the foundry making ONE casting and reducing CR with dished pistons.

TierAngst

I thought only 305's got the smaller cc heads... How would I be able to find this information out for my car? Would it be in my service manual?

TierAngst

Will do more research after work (on lunch break) but I did a quick search and found this...
http://69.20.110.81/index.asp?PageAc...D&ProdID=42937

BronYrAur

iTrader: (1)

305's did get smaller cc heads, in that they had 58cc combustion chambers. I would check the casting numbers on your heads and reference them on something like www.mortec.com or similar. I would say they are most likely 64cc heads, same as vortecs. You just don't see those big chambered heads much anymore on fairly late model cars/trucks. Like kdrolt was saying, i think cost efficiency alone would say all 350 swirl heads would be 64cc and just the pistons would be dished or not dished.

That link you posted gives compression for the 9C1 car to be 9.6:1 and lists the heads as 65cc, that makes me think they're probably flat top pistons in that engine. Whereas the lower compression motors probably had the same heads but dished pistons.

kevm14

My 93 FSM lists my compression at 9.8:1.

Too bad this thing uses dished pistons:

http://www.sdpc2000.com/catalog/514/...e-Assembly.htm

If L31s have about the same combustion chamber volume as my 193s, and I have flat top pistons, then I can use flat top pistons with L31s and still run 87 octane. That'd be nice.

TierAngst

The link I posted says except 9C1 cars. Which would mean my engine as well as Kevin's. I think I'm back on track with these vortec heads though.

BronYrAur

iTrader: (1)

haha so it does. I overlooked that, just glanced quick. Just noticed now that it lists flat top pistons too. I would definitely check the head casting numbers though to be sure, but you're most likely fine with 64cc heads.

kdrolt

They say "except police" because the engine:

1. has the low-lift peanut cam rather than the police cam (773 pn suffix, same as used on L98),

and

2. they don't want it used for warranty use in a copcar (even though it's an identical LO5 engine, other than the cam).

TierAngst

Anyone know the stock head gasket size bore/thickness? It'd help an awful lot for figuring out compression differences between heads with a new gasket.

zipfast

iTrader: (2)

You can use the 64cc Vortec's.
I just happen to have the engine on the stand out of my 93 (LO5) it does not have a dished pistons they are flat tops. They do have 4 valve refiefs at about 5cc.
The pistons are .020 down in the hole, the gasket is .037 after compression by 4.1 bore. The 193's come in at 64ish cc like Fast355 said. With all that stated gives you about 9.83:1 by the Compression Ratio Calculator that I use.
If you want to change the CR alittle just use diffrent head gaskets, a .060 copper will be 9:32:1,
an .043 gasket (.041 compressed) will be 9.74:1
and a .015 steel shim will be 10.38:1

Fast355

iTrader: (2)

If you use the .015" steel shim gasket, with the .020" in the hole, that is about .035. You need a steel shim gasket that comes in at about .020 if your pistons are .020" in the hole. Most rebuilder pistons are .025" in the hole, combined with the .015 shim, that is .040. With .040 quench and higher compression you will actually have less of a chance of detonation than say .060 with lower compression.

TierAngst

You read that article too

Anyone have Desktop Dyno??? I'm trying to figure out the compression ratio calculator in it... not making any sense to me.
For flat top pistons without valve reliefs it gives four options
1) Head chamber volume (64cc)
2) Head gasket bore (4.2")
3) Head gasket thickness (.039")
4) Piston down bore @ TDC (.045") Added the 5cc of valve relief here
Gives a compression ratio of 9.73

When I try to do it the right way using option two
For dome, dish, or flat tops with valve reliefs I have five options
1) Head chamber volume (64cc)
2) Head gasket bore (4.2")
3) Head gasket thickness (.039")
heres where I get lost
4) Piston down from TDC (?) value must be between 0.1 and 2.0 inches
5) Volume above piston (5cc)

I tried using a shim (.02 as mentioned) in the first set but it jumped from the 9.73 to 10.21 which seems a bit higher than I want.

Fast355

iTrader: (2)

Here is my math on the 193s

Stock 350 bore and flattop piston with 4 valve reliefs (8cc of reliefs)
65 CC 193 Head
.020 in the hole((factory engine are about this)
.020 nominal compressed gasket 4.1" diameter (typical felpro shim which is identical to what would have come in the 9C1)

9.78:1

Fast355

iTrader: (2)

You actually have to pick a point in the pistons travel, and CC the volume above the piston for this choice.

I simply do my math by taking the piston dished volume and adding it to the head CC.

TierAngst

So what do you think I should plug in for #4 on the second option?

kevm14

Damn, they fully spec out the cam in that thing. That would be useful for at least modeling the non-9C1 L05. What are 9C1 people supposed to do?

kdrolt

It's the so-called peanut cam Kevin. The specs are on TGO already.

A 9C1 owner would have to swap cams.... which would technically void the warranty if they ever found out about the cam swap.

kevm14

I know it's the peanut cam. I've just never seen the full IVO, IVC, EVO, EVC specs for it before. They are much more accurate in engine modeling than using the duration @ 0.050 or even advertised duration. See my post in your sticky thread.