Compression...on L98 383
Thread Starter
Drifting
Joined: Feb 2002
Posts: 1,937
Likes: 2
From: Arvada CO
Re: Compression...on L98 383 (black bart)
Black Bart...yes I am running the SRP flat top pistons and the block is not decked and the pistons are down in the bores. I know he decked the heads to make them even. But everything is agreed on with the 74CC heads for 9:1 compresh? But still I don’t know jack about heads and CC's and blah blah blah? I just know this guy is a huge blower guy out here in Denver and everything he has he has a blower on (his wife’s C5 with 11:1 and D-1r)? But I have seen his work and all the cars out here are running allot of compression with blowers? There is a guy running 9:1 with 10psi and his car is super slow? But I am not saying mine would be slow but I am really wondering if atmosphere is really a huge factor out here? I called another shop and they are running all there cars at 10:1 or higher on 10psi? But my guy did say running at sea level would be out of hand and you would break parts running 10:5:1 with 10psi. But he is warranting it all and he wants to hit the dyno and see what kind of # we will be making before heads and after AFR heads.
Thanks again guys for all your help!
Thanks again guys for all your help!
Drifting
Joined: Jul 2001
Posts: 1,897
Likes: 0
From: La Fontaine Indiana
Re: Compression...on L98 383 (krivera)
You said that with the current heads that the C\R would be 10 to 1
Last winter you stated that you were at 17 lbs. boost if you run it at that boost and C\R your effective compression ratio will be 21.56 :eek:
If you plan on running full timming and pump gas all I can say is
GOODLUCK
Last winter you stated that you were at 17 lbs. boost if you run it at that boost and C\R your effective compression ratio will be 21.56 :eek:
If you plan on running full timming and pump gas all I can say is
GOODLUCK
Drifting
Joined: Dec 2001
Posts: 1,313
Likes: 1
From: providence ut
Re: Compression...on L98 383 (black bart)
what heads and c/r are you running dick..............and how in the dell do you get the serpentine belt on your crank pulley with that 8 ribs...mines a bitch with a six.
Drifting
Joined: Jul 2001
Posts: 1,897
Likes: 0
From: La Fontaine Indiana
Re: Compression...on L98 383 (lead foot 85 vet)
[QUOTE]what heads and c/r are you running dick..............and how in the dell do you get the serpentine belt on your crank pulley with that 8 ribs...mines a bitch with a six
QUOTE] Heads are AFR 220 Static C\R is 9-1 but needs to be lowered.
I put the belt on just like I did the 6 rib twist it and it goes right in.
On this subject I read where people are installing chains and cogged belts and I wonder how this will workout because the gears in a centrifugal blower can't withstand that amout of strain. Roots blowers on a street engine typically run 10% underdrive a procharger runs about ten times engine speed this means that when the engine gains 1k the blower has to gain 10k a small amount of belt slip would be better than breaking the transmission in the blower. The drag boys replace their cogged belt every run and still break them just something to think about.
QUOTE] Heads are AFR 220 Static C\R is 9-1 but needs to be lowered.
I put the belt on just like I did the 6 rib twist it and it goes right in.
On this subject I read where people are installing chains and cogged belts and I wonder how this will workout because the gears in a centrifugal blower can't withstand that amout of strain. Roots blowers on a street engine typically run 10% underdrive a procharger runs about ten times engine speed this means that when the engine gains 1k the blower has to gain 10k a small amount of belt slip would be better than breaking the transmission in the blower. The drag boys replace their cogged belt every run and still break them just something to think about.
Thread Starter
Drifting
Joined: Feb 2002
Posts: 1,937
Likes: 2
From: Arvada CO
Re: Compression...on L98 383 (krivera)
Well i am getting the Car back really soon...my guy working on it called and said they have it started and are tuning it so it should be ready to night! come to find out i had alot of broken connectors and stuff and i went with a smaller converter :)
Racer
Joined: Oct 2000
Posts: 315
Likes: 0
From: Johnstown PA
Re: Compression...on L98 383 (krivera)
On my info. sheet that came with my LPE 383 it says 10.5 but after talking to Tim Deyer @ LPE he told me he thinks it is 10.75 If I would have know this prior I would have never put the SC on my car!! Hope everything works out for ya!
[Modified by SnakeCharmer, 3:44 PM 6/5/2003]
[Modified by SnakeCharmer, 3:44 PM 6/5/2003]
Thread Starter
Drifting
Joined: Feb 2002
Posts: 1,937
Likes: 2
From: Arvada CO
Re: Compression...on L98 383 (SnakeCharmer)
Well to be honest right now the 10:50 compresh is no problem and i have pretty much broke it in and ran the **** out of it already so if was going to blow it would of blew the other night:D but i am thinkin at this altitude that is not a big deal? could i be wrong?
Burning Brakes
Joined: Aug 2000
Posts: 1,146
Likes: 2
From: Albuquerque NM
Re: Compression...on L98 383 (krivera)
My 11.15 c/r would ping hard but here are the things your should consider
apparent boost = ((12.2+Max boost/12.2) * static c/r * funky number dealing with your I/E valve overlap
In addition, I was running ouch 42 deg adv spark (thanks Ed)
Your biggest problem is that you have max 91 octane available vs 93 (94.5 in Al). You can buy octance booster but it will never be as good as premixed.
In addition, according to ligenfelter keeping your rod ratio high as well as getting your quench (TDC distance between head and piston) around .030" to 0.04" would maximize your ping tolerance.
Finally, don't be afraid to inter-cool your charge. whether misting (carroll s/c or 'aquamist') or air/water. Keeping the inlet temperature down is your best bet for beating ping.
apparent boost = ((12.2+Max boost/12.2) * static c/r * funky number dealing with your I/E valve overlap
In addition, I was running ouch 42 deg adv spark (thanks Ed)
Your biggest problem is that you have max 91 octane available vs 93 (94.5 in Al). You can buy octance booster but it will never be as good as premixed.
In addition, according to ligenfelter keeping your rod ratio high as well as getting your quench (TDC distance between head and piston) around .030" to 0.04" would maximize your ping tolerance.
Finally, don't be afraid to inter-cool your charge. whether misting (carroll s/c or 'aquamist') or air/water. Keeping the inlet temperature down is your best bet for beating ping.
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