Compression lt1 383
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Joined: Oct 2018
Posts: 22
Compression lt1 383
Hey,what kinda compression are a lot of you guys running to run on pump gas? I got 2 relief flat tops and with 3.75 stroke and If I run a 58cc or 60cc combustion chamber I’m looking at 12to1or so.i have heard that i mite get away being able to run pump gas if I run like a 256/276 110lsa cam.. but just like to no what some of you are running on pump gas,I want to get compression as high as I can ,but not have run race gas... The higher I can get the compression the more power in guna squeze out of the engine ,with good porting and support mods.
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Joined: Jan 2004
Posts: 77
From: Lake Wylie, SC
Re: Compression lt1 383
I built a 383 with aluminum LT1 heads and a GM hot cam. We aimed at 10:1 CR so we could run pump gas. No, we didn't build it to win trophies at the track, just terrorize at the local traffic lights.
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Joined: Feb 2004
Posts: 1,154
From: VA
Registered User
Joined: Feb 2004
Posts: 1,154
From: VA
Re: Compression lt1 383
Hey,what kinda compression are a lot of you guys running to run on pump gas? I got 2 relief flat tops and with 3.75 stroke and If I run a 58cc or 60cc combustion chamber I’m looking at 12to1or so.i have heard that i mite get away being able to run pump gas if I run like a 256/276 110lsa cam.. but just like to no what some of you are running on pump gas,I want to get compression as high as I can ,but not have run race gas... The higher I can get the compression the more power in guna squeze out of the engine ,with good porting and support mods.
Thread Starter
Registered User
Joined: Oct 2018
Posts: 22
Re: Compression lt1 383
12to1 that’s more like it.i emailed loyd he said bout 12to1 or little above,with like a 244/254 110lsa cam,he figured you would have to run 92 93 octane.were I live most I’m guna get at pump would be 91,n I could at some 104 booster to it,but I would really like to make shur I’m not guna have a detination problem.i was thinking changing out the pistons to a 4 releif flat top and run the stock heads witch I’m guna have loyd port and run like a .50 head gasket and with deck height should put me around 11.5,but I am open to any suggestions because I want get most out of engine first time around n not wish I did things different after it’s in..
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Joined: Nov 1998
Posts: 71,123
From: Hell was full so they sent me to NJ
Re: Compression lt1 383
Why would you lower the CR? Not necessary, unless you're running iron heads.
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Joined: Apr 2007
Posts: 425
Re: Compression lt1 383
I have a new all forged 383 LT1 with LE3 heads, 847 cam (234/242@.050/.575/.595" lift) and my cr is 12.5:1 and I'm running 93 pump gas with no problems. However when I got my engine I asked what my timing curve should be for the SCR I'm running and my machine shop told me 14*- 16* initial at idle and slowly ramp it up to 32* - 34* total.
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Joined: Nov 2002
Posts: 1,332
From: Louisville KY
Re: Compression lt1 383
Agree, there is zero reason to run lower than stock compression. Especially with an aftermarket cam as you are most likely lowering the dynamic compression even lower than the 0.4 reduction in static that you are running. 11-12 is not a problem on 93 pump gas if you are running the right cam.
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