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I invent stupid usernames
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Discussion Starter · #1 ·
I'm building up the 350 in my truck, and I'll list the specs below, but the real question is: can I run 9.23:1 compression on 87 octane unleaded with .040" quench distance without detonating? P.S. I will not change my heads to vortec, don't try to convince me, and my cam choice is staying too.

Specs (important for this question):
Heads: Summit SUM-152123 72cc comb. chamber (Same casting as Dart Iron Eagle s/s so I've heard).
Head Gaskets: Mr. Gasket .015" thickness 4.100" bore
Deck clearance: .025" in the hole
Pistons: D.S.S E Series forged 8cc dish
Stroke: 3.48"
Bore: 4.030"
Camshaft: Comp Cams XE256H 256/268 adv. dur. 212/218 @ .050 lift

This truck will be a daily driver and a puller (trailers and such)
This puts my compression ratio at 9.225:1 but rounded to 9.23:1.
 

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Wrench Turner
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4,952 Posts
It really depends more on your actual running compression(DCR) is after considering cam timing.Namely the point in degrees that the intake valve closes. (IVC).This will determine the amount of mixture pulled into the cylinder & therefore the amount of cylinder psi.There are several online calculators that will help you determine this.For a modern iron head, you want this # to be 8.5:1, or thereabouts.For older smog type heads, keep it closer to 8:1.For aluminum heads, you want in the range of 9:1.
 

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Wrench Turner
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4,952 Posts
Based on the info you supplied,the KB calculator puts the DCR for your motor at 8.25:1,if the cam is installed straight up & not advanced,or,retarded.You should be good on 87 octane provided the tune/fueling is setup correctly along with adequate cooling.IMO,the KB calculator runs slightly high,so,I would think you are good to go.
 

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I invent stupid usernames
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360 Posts
Discussion Starter · #6 ·
Based on the info you supplied,the KB calculator puts the DCR for your motor at 8.25:1,if the cam is installed straight up & not advanced,or,retarded.You should be good on 87 octane provided the tune/fueling is setup correctly along with adequate cooling.IMO,the KB calculator runs slightly high,so,I would think you are good to go.
I know this is a dead thread, but I just found out some useful information about my cooling system. I have a 3 core radiator.
 

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Administrator
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Probably a Brass rad ?
Aluminum is far superior.
If you live down south where summer temps are pretty high all day, you might wanna consider at least a one core (large tube,like 1 inch) aluminum rad.
 

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I know this is a dead thread, but I just found out some useful information about my cooling system. I have a 3 core radiator.
What is the core surface area or what is this radiator for or from? A GM 30 by 19 with a 3 tube core in copper/brass that is in good shape will cool a 350 with no problems. My experience shows that a 2 row of 1 inch tubes with the same surface area of 30x19 will cool the same as a 3 tube core copper/brass radiator

Bogie
 
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