Is 11.2:1 compression too much for pump gas.
03-05-2016, 08:27 PM
#22
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Do to my current motor issue I'm have to put a motor together from spare parts. I have a 6.0l short block and the 59cc stage 2 ls6 heads off of my 5.7 and the compression will be about 11.2:1 with a .060 headgasket. Will that be too much for 93 octane or should I get a .075 headgasket to lower it to 10.9:1. The only other thing I can do is to put my stock 5.7 heads on it but I would really like to have my ported heads on it.
03-06-2016, 01:00 AM
#24
The 'limit' is going to vary from car to car. Two cars running the same heads, cam, octane and tuned to the same timing may or may not have the same tolerance for detonation. Other factors that can effect octane tolerance:
Coolant Temps
Ambient Air/Inlet Air Temps
Underhood Temps
PCV System - Oil/Carbon deposits in the combustion chamber
Coatings on the valves/pistons/combustion chambers
http://www.popularhotrodding.com/tec...power_squeeze/
http://www.popularhotrodding.com/tec...ression_ratio/
Coolant Temps
Ambient Air/Inlet Air Temps
Underhood Temps
PCV System - Oil/Carbon deposits in the combustion chamber
Coatings on the valves/pistons/combustion chambers
http://www.popularhotrodding.com/tec...power_squeeze/
http://www.popularhotrodding.com/tec...ression_ratio/
WTF
05-22-2016, 02:30 AM
#28
I know this is an old thread but have a few questions. I have a Gen 4 Iron Block 5.3 in my 2008 Silverado, 3.78" bore, 3.622" Stroke. I know not a Gen 3 but this is a good thread in regards to my question. My 243 heads are at PRC being ported and milled, I have not told them what to mill them to yet since they are closed on the weekend. My goal was the Mill them to 59cc, use a .045" head gasket to have my Quench / Squish at .038" with Flat top pistons (0cc) with no valve reliefs. I will be using 91 Octane gas, with my current cam and specs my Static compression will be at 10.82:1 and Dynamic Compression at 8.73:1. I have always been told that 8.7-8.8:1 is Max for 91, and I dont have 92 or 93 Octane where I live.
243 stock Chamber size is 64.45cc
Now is that to high or should I step down. I can have them milled less if anything
59.45cc = STC 10.75:1, DCR 8.68:1
60cc = STC 10.68:1, DCR 8.61:1
60.45cc = SCR 10.61:1, DCR 8.57:1
61cc = STC 10.54:1, DCR 8.51:1
Opinions please, this is my Daily and I tow my travel trailer with it.
243 stock Chamber size is 64.45cc
Now is that to high or should I step down. I can have them milled less if anything
59.45cc = STC 10.75:1, DCR 8.68:1
60cc = STC 10.68:1, DCR 8.61:1
60.45cc = SCR 10.61:1, DCR 8.57:1
61cc = STC 10.54:1, DCR 8.51:1
Opinions please, this is my Daily and I tow my travel trailer with it.
05-22-2016, 01:01 PM
#29
91 RS w/LS1 stroker LS6 etc see sig 11.3 to 1 compression - no knock or ping or issues on 93
99 TA see sig 10.8 compression will ping on 93 octane in summer at low rpm crusing in 6th gear. Decarbon treatment and new plugs help for a while. Car has 152,000 miles and 120,000 is with heads and cam package. Probably would benefit from a retune.
99 TA see sig 10.8 compression will ping on 93 octane in summer at low rpm crusing in 6th gear. Decarbon treatment and new plugs help for a while. Car has 152,000 miles and 120,000 is with heads and cam package. Probably would benefit from a retune.
05-22-2016, 02:27 PM
#30
11 Second Club
I'm have a stock 2008 CC Silverado with the 5.3 (shorty headers and ram air) and it has a maxed out 87 octane custom tune.. It pings on 87, it pings on 89 depending on the time of the year and it runs perfect on 93.. It's a heavy truck on 33in tires.. With heavy trucks you have to be careful with how aggressive the tunes are especially if you tow..
05-22-2016, 09:48 PM
#31
I know this is an old thread but have a few questions. I have a Gen 4 Iron Block 5.3 in my 2008 Silverado, 3.78" bore, 3.622" Stroke. I know not a Gen 3 but this is a good thread in regards to my question. My 243 heads are at PRC being ported and milled, I have not told them what to mill them to yet since they are closed on the weekend. My goal was the Mill them to 59cc, use a .045" head gasket to have my Quench / Squish at .038" with Flat top pistons (0cc) with no valve reliefs. I will be using 91 Octane gas, with my current cam and specs my Static compression will be at 10.82:1 and Dynamic Compression at 8.73:1. I have always been told that 8.7-8.8:1 is Max for 91, and I dont have 92 or 93 Octane where I live.
243 stock Chamber size is 64.45cc
Now is that to high or should I step down. I can have them milled less if anything
59.45cc = STC 10.75:1, DCR 8.68:1
60cc = STC 10.68:1, DCR 8.61:1
60.45cc = SCR 10.61:1, DCR 8.57:1
61cc = STC 10.54:1, DCR 8.51:1
Opinions please, this is my Daily and I tow my travel trailer with it.
243 stock Chamber size is 64.45cc
Now is that to high or should I step down. I can have them milled less if anything
59.45cc = STC 10.75:1, DCR 8.68:1
60cc = STC 10.68:1, DCR 8.61:1
60.45cc = SCR 10.61:1, DCR 8.57:1
61cc = STC 10.54:1, DCR 8.51:1
Opinions please, this is my Daily and I tow my travel trailer with it.
Most vehicles I see pushing the boundaries with a high SCR and DCR are relatively light and run hard in short bursts. I think that your application is altogether different.
05-25-2016, 08:31 AM
#32
I'm have a stock 2008 CC Silverado with the 5.3 (shorty headers and ram air) and it has a maxed out 87 octane custom tune.. It pings on 87, it pings on 89 depending on the time of the year and it runs perfect on 93.. It's a heavy truck on 33in tires.. With heavy trucks you have to be careful with how aggressive the tunes are especially if you tow..
A bottle of Techron every month helps TREMENDOUSLY also, the one good for 20 gallons.
05-25-2016, 09:33 PM
#34
05-26-2016, 08:58 PM
#37
I see you are in Nevada and towing a travel trailer. I would venture a guess that an 8.73 DCR is too much for a heavy truck and trailer combo that is heat soaked and pulling up some of the long passes out west. Keep your quench as that helps, but I would not go over 8.5 DCR.
Most vehicles I see pushing the boundaries with a high SCR and DCR are relatively light and run hard in short bursts. I think that your application is altogether different.
Most vehicles I see pushing the boundaries with a high SCR and DCR are relatively light and run hard in short bursts. I think that your application is altogether different.
