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706 Heads On 6.0 Questions


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Well i acquired some milled/p&p 706 5.3L heads, ive been doing some reading but still need some help, wheater or not i will benefit from the switch. So far i know they will raise my compression, from some reading it will be good low end tq but not quiet up top. any other help from the tech guys would be helpfull, im not building a race truck just need it quicker and do plan to go whit a 102 fast intake later on, staying N/A.....low 13's maybe high 12's would be good.

 

Im not sure how much there milled, i still need to take them to the machine shop to measure but i belive .03

 

 

I do know 243/799 heads would be best (well besides l92's that everyone is putting on now days) but i got these for a deal w/dual springs ect. whit 0 miles since the work was done to them.

 

Mild cam 224/224 563/563 112lsa (wish it was the 581 lift but like mentioned, deal!)

 

Thanks for any help. :)

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I talked to a guy who had done this swap and said that with the bump in CR (61.15cc vs 71.06) made up for the slight loss of flow. INT-200/EXT-70cc 706 vs 210/75 for the 317.

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Could i use the valves in my 317's? i remember when i was reading someone mentioned this i belive there 2.0 intake/1.55 ex.

 

 

I'm not opposed to leaving the stock 317 heads on and just doing the cam swap either.

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Let me go through my PM's IIRC it was zippy that i talked to who done this to a LQ4 and all he done was swapped out the INT vlv for a 2", EXH vlv is the same size as our 317's.. If yours has been milled you might want to run a thicker gakset to lower your CR some as it might be to high were the LQ9 has flat top pistons and the LQ4 has a dished piston.

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You can run a stock 2.00 Valve if your on a budget. If you want the best Air flow a back cut and polished valve would be the best choice. I am not sure if there is enough meat to go to a 2.02 valve or not.

 

You might even find a nice set of take out Valves on Ebay. Every once and a while stuff like that pops up.

 

Most of the modified heads on the market go with a 2.02/ 1.57 combo. So the stock valves get tossed. Howeveer some guys buy new heads and re sale the original valves. there really not worth more then $50 in my Opinion. in some cases I have seen a whole set of in/ex sale for that.

 

And by the way he is correct on the head gasket. You may bump the compression a little to much with those heads and want to run a thicker gasket so you can still run pump gas.

Edited by 1FASTBRICK
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  • 2 weeks later...

IMHO

 

The compression rise isn't worth the trouble and cost of changing heads. With smaller valves it's a step backwards. I would do cam and exhaust work with your exsisting heads. Plus the usual tuning of injectors,computer etc..

 

 

My V-Max 6.0 pings on less than 92 octane.

 

:pepsicheer:

 

The compression is worth everthing. Yes it has a smaller valve in stock form but the added compression will help in increasing air speed and pull more air into the cylinder. If he runs higher compression he can also run a slightly larger cam and the larger intake manifoldand still tame the idle, driveabilty and needed stall down. When picking a cam you can also run a cam with more overlap to get better top end numbers and not worry about your DCR going to hell because your static compression was higher to begin with

 

A lot of guys are running decked heads and thinner gaskets to make these motors really shine. I'm running around 11.38 and still getting away with 33 degrees of timing using aftermarket heads and 93 pump gas. with the stock heads i ran around 10.97

 

The heads are ported? by who, or better yet by what? A cnc or a die grinder? Do you know the new flow numbers even with the smaller valve?

 

Decking a 5.3 head can put you into to high of a compression ratio so i would want to know the exact amount they are decked before putting them on my truck. If they are decked .030 that would be around 6cc missing(or worse because the chamber was so small already), putting you around a 55cc chamber. A 55cc chamber on a stock head gasket would be around 12.68, so these heads are just not right for our stock flat top pistons, but don't fear a reasonable amount of increase 11.3-11.8 ish.

Edited by shadowsniper3006
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The compression is worth everthing. Yes it has a smaller valve in stock form but the added compression will help in increasing air speed and pull more air into the cylinder. If he runs higher compression he can also run a slightly larger cam and the larger intake manifoldand still tame the idle, driveabilty and needed stall down. When picking a cam you can also run a cam with more overlap to get better top end numbers and not worry about your DCR going to hell because your static compression was higher to begin with

 

A lot of guys are running decked heads and thinner gaskets to make these motors really shine. I'm running around 11.38 and still getting away with 33 degrees of timing using aftermarket heads and 93 pump gas. with the stock heads i ran around 10.97

 

The heads are ported? by who, or better yet by what? A cnc or a die grinder? Do you know the new flow numbers even with the smaller valve?

 

Decking a 5.3 head can put you into to high of a compression ratio so i would want to know the exact amount they are decked before putting them on my truck. If they are decked .030 that would be around 6cc missing(or worse because the chamber was so small already), putting you around a 55cc chamber. A 55cc chamber on a stock head gasket would be around 12.68, so these heads are just not right for our stock flat top pistons, but don't fear a reasonable amount of increase 11.3-11.8 ish.

 

 

 

 

Thanks for the education. I was hoping my comment would draw out the tech reasons for the head swap. I know very little about the newer LS motors and their respective numbers.

 

I didn't realize you could get such a bump with just a head change. I figured he would get at most he would about .25 to .50 in compression.

 

 

 

How much Hp could he gain with this swap?

 

I have little to no experience with computer controlled mods either.

 

Give me a few months on this Forum and I will catch up. Thats why I am here. Can't beat the forums for an accelerated education.

 

 

 

 

:cheers:

Edited by 1STTEXAN
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