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spize909

Heads for a 5.3

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A guy in our group has a Desert Dynamic sand car that has an iron block 5.3 in it. He put a cam in it and now wants to do something with the heads. Any suggestions on good set ups?

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the aluminum 5.3 heads are 243, make sure they are the same combustion chamber size, so you do not loose comp ratio,

the iron 5.3 heads have tiny valves so this should be a great improvement, to add to that I would go to a LS2 intake, with a 90mm Throttle body,

it is $23 change the lifter guides,  I have used the summit and jegs ones, they suck for $4 a set more use the AC delco guides,

funny thing about a cam is that you only gain 75% of the power with the stock lifters,  we have ran a bunch of dyno test with the 440 and we gained 30 rear HP with race lifters, not sure what this would add to a 5.3 but we use the Johnson Race Slow leak limited travel lifter,

this will need to be setup around .035  +/- .010 of lift,

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Posted (edited)

 Sorry this might be long.

IMO he made a mistake. Rule one is match the components - don't pick a cam until you know what heads you are gonna run.  engines are air pumps.... the cam can make them pump more air, but  if you can't flow it then its a waste.

The Throttle body, intake manifold, cam, heads and headers should all be considered when choosing any of the those pieces by themselves.  this is why good builders and companies sell kits.  Trickflow has done a huge business on this. and in the sand world CBM does this as well.   Any one of thos pieces is a choke point.  So if the budget is a consideration, Start buying the pieces of a "combo" and as you add the other pieces it just gets better 

But to answer your Q:

Depending on the model of the Iron 5.3 it came with a lot of different heads... You can identify them by the three digit number stamped near the valve cover.

As I recall all early trucks before 2005 had 706. 852 and 862 heads all are 61cc chambers  (the Ls1 heads are 64- 65cc exceptt first year are 67cc)

so if thats what he has and puts an LS1 or LS2 head on the engine he will lose compression and therefore power, almost a 1/2 point compression so depending on cam and other factors maybe 25-35HP and LS engines LOVE compression for power (up to the point where you can't run pump gas that is...)

the 706. 852 and 862 heads are all small valve and make awesome low end because they were built for Torque on trucks, but fall off over 4500 RPM ish...  I don't think you lose more power with smaller valve heads on a mild engine  than you would with bigger valve heads and less compression, so an off the shelf swap for swap does not buy you anything just to put a bigger un ported head on.

For example - I have a 5.7 running 706 heads that makes more power down low than it would with LS1/LS6  243's ...for duning in the 2500-4000RPM range with the right trans gears - it is amazing, idles like a baby roars like a lion... so its a combo thing...

the LS1 Heads of choice are 243's followed by 241's in most cases those two are equal on a 5.3 and 241's are generally half the price.

So you can easily go to an LS1 head that is surfaced down to 64cc (safe) and run a thinner head gasket and regain the compression lost and the engine  assuming the cam is right - will pick up power and everything will fit fine.

 All the LS1/6 heads have a limiting factor  that is the shrouding on the valve due to small chamber size - the valve is too close to the side...this just cannot be worked around,  so you only get so much power compared to a bigger bore head.

Now here is some Good news

5.3 Iron engines 2005 and up run Great heads they will have 799 heads which are essentially 243 heads  so if he has those he's great...

Of course there are tons of great aftermarket heads that offer better valves and better flow and some have porting specifically good for sand car use like the CBM's 

and even some as-cast heads like the PRC's that can be had any combustion chamber size from 61-71cc that are huge HP makers

IMO if you go with new or rebuild heads - spend money on US made Manley or Ferrea valves and good springs and valve locks. Factory valve guides last 150,000 miles, stock rockers are perfect for milder cams, and Factory valves are good, some aftermarket are Junk. Drop a valve and throw away your engine.. its not worth it

Intake wise the LS6 intake is far better than any LS1 intake even with  a ported 78mm TB from ebay (cost you $50-75 and they work) small TB  is fine on a 5.3  especially if its ported. That combo is miles better than an LS2 intake even though the LS2 uses a 90mm TB- GM screwed that one up bad.  and ypou can save money by not buying a non-china 90mm TB just to use on a bad flowing LS2 manifold - the no brand China ones are not very good or consistent - can't go wrong with Nick Williams, Fast, or Accufab/CBM but those are $400-500.  (Chinese ones like G-plus are $50 and generally have all kinds of problems including sticking open and losing screws into the intake. The Holley Sniper is low quality and half the price , and they fixed some of the warts and are a little better.

And believe it or not the Dorman 615-901 intake with a 90mm throttle body out performs anything shy of the $1200 FAST intake.  Dorman took an LS6 lower and a Fast upper (90mm ready) and put them together - it a fantastic intake for under $400 new..

Edited by fullthrottleguy
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Thanks for the info. I forwarded it over to him.

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AZLSX board on facebook I saw a bunch of 243 heads for around $400 loaded which is a great price.  I am sure you can get a ls6 intake on there too. 

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Depends on how much you’re willing to spend on heads and intake what would be best. Mast Motorsports makes great heads, AFR or look into the PRC from Texas speed. Intake, a stock ls6 or Dorman intake are great. No reason to spend a ton on intake if you’re not going to flow enough to make a huge difference. 

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