What kind of compression do you all think I have?
(approximately). I have a BBC

60 over 427
215 oval port closed chamber heads (219/188 valves I think they are 100.9cc
The heads have been shaved TWO different times
And I have JE forged flat top pistons with valve relief's
the block was zero decked
.039 typical head gaskets
and I run the UD hyd ROLLER 288/296 234/244 .600/.600 cam on a 110 LSA
I was told it should have at least 10-1 but others tell me it would be much lower. I would like to here a few of your opinions. After a few guesses on this, I will have another fun questions for you blower people thanks for any help.

i guess 9 ish?

I had a 454 with a JE blower piston with a single valve relief and .040 copper gasket and closed chamber head (rec.port)which has a larger chamber and my comp. calculated to 10-1.I think your definetly over 10-1.

If the heads are 101 its about 8.2

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Oops graemlins/clonk.gif If the heads are 101 it would be 8.7 not 8.2

Running the numbers through the ROSS Racing Piston compression ratio caculator using -6 cc's for the valve notch and .0001" for the deck height since it won't calculate zero, gave 8.73 CR.

I may be too small on the valve notch size???

AND a stock, '74/'75, 454 P/U motor with -781 heads is only like 7.9 to maybe 8.1 CR. with stock, true flat-tops..

pdq67

Mike,101= 8.2 ?? then what was my 106 7.8-1 ???

Sorry about that I used the wrong piston top diameter graemlins/clonk.gif
With zero deck it would be about 8.7
With a std 9.800 deck int would be about 8.5

Josh, 106 would be about 8.4 at zero deck

If the heads have been shaved twice, then the cc volume should not be 101 (maybe under 100 cc's?).

Anyway, a quick input of the info in Pat Kelly's DCR program gives approximately 6.7, which is way low.

Charles

So it kinda looks like most of you figure it has around (8.7) or around 9 to 1 at most even with the closed chamber heads?

i come up with a rough 8.6 to 1 compression...........with the heads being shaved it would come in slightly higher not knowing the true cc'c of the heads......it would be very safe to say your under the 9.0 to 1 mark........

Originally posted by bb427:
So it kinda looks like most of you figure it has around (8.7) or around 9 to 1 at most even with the closed chamber heads? =
yes ;)

Thanks for all the replys.
I am going to start another topic about putting a blower on my car tomorrow maybe you guys can help me out with that also. I will post my 427 specs for ya.

I thought flat tops and closed chambers = 10.1-1+ compression :confused:

Originally posted by Rapid Robert:
I thought flat tops and closed chambers = 10.1-1+ compression :confused: =
Not on Rat unless it's a 496 & then it would be about 9.7 ;)

That's what's wrong with the aftermarket head choices b/c we really could use a cast-iron head like a large oval port Merlin that is down around 90 cc's so we could get good compression from the old, stock, true flat-top pistoned 454 P/U truck motors we have to dig up to start with..

Plus make this type head so we can use ALL stock valve train parts too!! No custom length pushrods that would up the overall install job..

(E-brock does have a 100 cc aluminum head but it is a schosh pricey, imho..)

A 468" motor using .020" thick, steel shims should be right at 9.96 CR. with a 90 cc head!!!!

Should be perfect for street pump gas use, imho....

pdq67

This gets confusing. According to the KB site, the KB202 @ 30 over with my 97cc 206's are around 9.6:1 for 3cc flat tops. This sounds nothing like what you guys are describing here. :confused:

Not to mention all the wild arse guessing about chamber size. bb427, have one chamber on each head maeasured. Heck , here it only costs $25-30 for all 8. Don't guess at CC, MEASURE IT!

Originally posted by 70 Elco Joe:
This gets confusing. According to the KB site, the KB202 @ 30 over with my 97cc 206's are around 9.6:1 for 3cc flat tops. This sounds nothing like what you guys are describing here. :confused: Joe,
What is confusing about a 454 being 9.6 with a 97cc head??
The larger the engine the higher the compression with a given head volume holding all else equal.

Your engine calculates to 9.56 at zero deck with a 4.370" x .039 gasket, a 4.250 piston head diameter, 3cc valve notch, the rings down .200 & a 97cc head.

I just got finished posting 9.7 with a 101cc head at zero deck on a 496 but used a 5cc valve notch.
If it were a 97cc head it would be 10.05


And all this is assuming you know what the head cc actually is.
As Gene posted they need to be measured to give an accurate number ;)

Thanks Mike, I didnt realize 4cc's made that big of a difference in the SCR. graemlins/clonk.gif Just wanted to make sure that KB wasnt feeding me bogus info ;)

Joe,

Please use a static compression ratio calculator like ROSS Racing Pistons has and play around with the numbers.

Usually our pistons are down right about .025" from the factory and valve notches can vary from 4 to 6 cc's or more

We suggest cc'ing heads to be as accurate as possible b/c GM made open chambered heads from say 113 to 122 cc's.

AND closed chambered heads from 96.7, (ovals), to above 108 cc's in some of the rect. port heads..

The next thing to consider would be to cc intake ports but that's another post altogether!!

pdq67

So are we still saying it is safe to say that my CR is still 9.0 or less?

Originally posted by bb427:
So are we still saying it is safe to say that my CR is still 9.0 or less? =
Still yes ;)

Thanks Mike!
I just purchased a weiand 177 for my BBC tonight now I have to get some things figured out with my combo to make it work. Will my cam work with this blower I know that a wider LSA would be better but if it will work with what I have that would be better for me, I will up grade my fuel system to a electric pump. here is some info of what I got
60 over 427
215 oval ports closed chamber heads(219/188)valves
JE forged flat top pistons 8.73-1 cr (no more than 9.0-1)
UD hyd roller 288/296 234-242 .600 .600 on a 110 lsa Matching springs
CC roller lifters
Crane roller rockers
Cloyes hex adjust timing set
Performer RPM intake 1/2 four hole spacer
750 DP holley k&N air filter
Holley fuel pump
Mallory IGN
Dynomax headers 1 3/4"
3''exhaust with flowmasters
Turbo 350 - 3000 b&m stall
410 12 bolt posi
3750 pounds

Sorry BB427, didnt mean to hijack your thread. Thats a pretty nice combo you got going there. Should make one heck of a runner with it. You trying to run a cast crank with the blower, or do you have a forged one? I always see opinions from people that say both sides of the coin just wondering what people that actually use one are running.

Originally posted by 70 Elco Joe:
Sorry BB427, didnt mean to hijack your thread. You trying to run a cast crank with the blower, or do you have a forged one? I always see opinions from people that say both sides of the coin just wondering what people that actually use one are running. 70 Elco Joe - not a problem with the thread. Yes I only have a cast crank I wish it were forged.

IMHO,your 427 combo w/o the blower would perform quite well,even with your compression being 8.6

Originally posted by mr 4 speed:
IMHO,your 427 combo w/o the blower would perform quite well,even with your compression being 8.6 4 speed - The car does move well, should be real fun with the 177 on it. I am trying to find out how tall of a cowl hood I will need on my car. (69 camaro) does anyone know someone who has a BB with a 177 on there camaro?